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NERVOUS SYSTEM
Functions
1. Receiving sensory input
2. Integrating information
3. Controlling muscles and glands
4. Maintaining homeostasis
5. Establishing and maintaining mental activity
Main Divisions of the Nervous System
➢ Central Nervous System (CNS)
○ Brain and spinal cord
➢ Peripheral Nervous System (PNS)
○ All the nervous tissue outside the CNS
➢ Sensory division
○ Conducts action potential from sensory
receptors to the CNS
➢ Motor division
○ Conducts action potentials to effector
organs, such as muscles and glands.
➢ Somatic Nervous System
○ Transmits action potentials from the
CNS to skeletal muscles. (voluntary)
➢ Autonomic Nervous System
○ Transmits action potentials from the
CNS to cardiac muscles, smooth
muscle, and glands. (involuntary)
➢ Enteric Nervous System
○ A special Nervous system found only in
the digestive tract.
Cells to the Nervous System
Neurons
➢ Receive stimuli, conduct action potentials, and
transmit signals to other neurons or effector
organs.
➢ Main Cells
Glial Cells
➢ Supportive cells of the CNS and PNS, meaning
these cells do not conduct action potentials.
Instead, glial cells carry out different functions
that enhance neuron function and maintain
normal conditions within nervous tissue.
Neurons (Nerve Cell)
➢ Cell Body
○ Which contains a single nucleus
➢ Dendrite
○ Which is a cytoplasmic extension from
the cell body, that usually receives
information from other neurons and
transmits the information to the cell
body.
➢ Axon
○ Which is a single-long cell process that
leaves the cell body at the axon hillock
and conducts sensory signals to the
CNS and motor signals away from the
CNS
Structural Types of Neurons
➢ Multipolar neurons
○ Have many dendrites and a single axon.
○ Most of the neurons within the CNS and
nearly all motor neurons are multipolar.
○ Most common type of neurons.
➢ Bipolar neurons
○ Have two processes
■ One dendrite
■ One axon
○ Bipolar neurons are located in some
sensory organs, such as in the retina
of the eye and in the nasal cavity.
➢ Pseudo-unipolar neurons
○ Have a single process extending from
the cell body, which divides into two
processes a short distance from the cell
body.
○ One process extends to the periphery,
and the other extends to the CNS
○ The two extensions function as a single
axon with small, dendrite-like sensory
receptors at the periphery.
○ rare
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Glial Cells
➢ Glial cells are the supportive cells of the CNS
and PNS
➢ Types:
○ Astrocytes
■ Serves as the major supporting
cells in the CNS
■ Astrocytes can stimulate or
inhibit the signaling activity of
nearby neurons and form the
blood-brain barrier.
○ Ependymal Cells
■ Line the cavities in the brain that
contains cerebrospinal fluid.
○ Microglial cells
■ Act in an immune function in the
CNS by removing bacterial and
cell debris
○ Oligodendrocytes
■ Provide myelin to neurons in the
CNS
○ Schwann cells
■ Provide myelin to neurons in the
PNS
Myelin Sheath
➢ Myelin sheaths are specialized layers that wrap
around the axons of some neurons, those
neurons are termed, myelinated.
➢ The sheaths are formed by oligodendrocytes in
the CNS and Schwann cells in the PNS
➢ Myelin is an excellent insulator that prevents
almost all ion movement across the hall
membrane.
➢ Gaps in the myelin sheath, called nodes of
Ranvier, occur about every millimeter
➢ Ion movement can occur at the nodes of Ranvier
➢ Myelination of an axon increases the speed and
efficiency of action potential generation along
the axon.
➢ Multiple sclerosis is a disease of the myelin
sheath that causes loss of muscle function.
Unmyelinated Neurons
➢ Unmyelinated axons lack the myelin sheaths.
➢ These axons rest in indentations of the
oligodendrocytes in the CNS and the Schwann
cells in the PNS.
➢ A typical small nerve, which consists of axons of
multiple neurons, usually contains more
unmyelinated axons than myelinated axons.
Myelinated and Unmyelinated Neurons
Organization of Nervous Tissue
➢ The nervous tissue varies in color due to the
abundance or absence of myelinated axons.
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➢ Nervous tissue exists as gray matter and white
matter.
➢ Gray Matter
○ Consists of groups of neuron cell bodies
and their dendrites, where there is very
little myelin.
➢ White matter
○ Consists of bundles of parallel axons
with their myelin sheaths, which are
whitish in color.
Membrane Potentials
➢ Resting Membrane potentials and Action
potentials occur in neurons
➢ These potentials are mainly due to differences in
concentrations of ions across the membrane,
membrane channels, and the sodium-potassium
pump.
➢ Membrane channels include leak channels and
gated channels.
➢ Leak Channels
○ Always open
➢ Gated Channels
○ Are generally closed, but can be opened
due to voltage or chemicals.
Leak Membrane Channels
➢ Leak channels are always open and ions can
“leak” across the membrane down their
concentration gradient.
➢ Because there are 50 to 100 times more K+ leak
channels than Na+ leak channels, the resting
membrane has much greater permeability to K+
than to Na+; therefore, the K+ leak channels
have the greatest contribution to the resting
membrane potential.
Gated Membrane Channels
➢ Gated channels are closed until opened by
specific signals
➢ Chemically gated channels are opened by
neurotransmitters or other chemicals, whereas
voltage-gated channels are opened by a change
in membrane potential.
➢ When opened, the gated channels can change
the membrane potential and are thus
responsible for the action potential.
Sodium-Potassium Pump
➢ The sodium-potassium pump compensates for
the constant leakage of ions through leak
channels.
➢ The sodium-potassium pump is required to
maintain the greater concentration of Na+
outside the cell membrane and K+ inside
➢ The pump actively transports K+ into the cell
and Na+ out of the cell.
➢ It is estimated that the sodium-potassium pump
consumes 25% of all the ATP in a typical cell
and 70% of the ATP in a neuron.
Resting Membrane Potential
➢ The resting membrane potential exists because
of the:
○ The concentration of K+ is higher on the
inside of the cell membrane and the
concentration of Na+ is higher on the
outside.
○ The presence of many negatively
charged molecules, such as proteins,
inside the cell that is too large to exit the
cell.
○ The presence of leak protein channels
in the membrane that are more
permeable to K+ than it is to Na+.
➢ Na+ tends to diffuse into the cell and K+ tends to
diffuse out.
➢ In order to maintain the resting membrane
potential, the sodium-potassium pump recreated
the Na+ and K+ ion gradient by pumping Na+
out of the cell and K+ into the cell.
Action Potential
➢ Action potentials allow conductivity along nerve
or muscle membrane, similar to electricity going
along an electrical wire.
➢ The channels responsible for the action potential
are voltage-gated Na+ and K+ channels, which
are closed during rest (resting membrane
potential).
➢ When a stimulus is applied to the nerve cell,
following neurotransmitter activation of
chemically gated channels, Na+ channels open
very briefly, and Na+ diffuses quickly into the
cell.
➢ This movement of Na+, which is called a local
current, causes the inside of the cell membrane
to become positive, a change called
depolarization.
➢ If depolarization is not strong enough, the Na+
channels close again, and the local potential
disappears without being conducted along the
nerve cell membrane.
➢ If depolarization is large enough, Na+ enters the
cell so that the local potential reaches a
threshold value.
➢ Thos threshold depolarization causes
voltage-gated N channels to open, generally at
the axon hillock
➢ The opening of these channels causes a
massive, 600-fold increase in membrane
permeability to Na+.
➢ Voltage-gated K+ channels also begin to open.
➢ As more Na+ enters the cell, depolarization
continues at a much faster pace, causing a brief
reversal of charge – the inside of the cell
membrane becomes positive relative to the
outside of the cell membrane.
➢ The charge reversal causes Na+ channels to
close and Na+ then stops entering the cell,
➢ During this time, more K+ channels are opening
and K+ leaves the cell, resulting in
repolarization.
➢ At the end of repolarization, the charge on the
cell membrane briefly becomes more negative
than the resting membrane potential; this
condition is called hyperpolarization and
occurs briefly.
➢ Action potentials occur in an all-or-one fashion
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➢ All-or-none refers to the fact that if threshold is
reached, an action potential occurs; if the
threshold is not reached, no action potential
occurs.
➢ The sodium-potassium pump assists in restoring
the resting membrane potential.
Generation of the Resting Membrane Potential
Action Potential
Voltage-Gated Ion Channels and the Action Potential
Unmyelinated and Myelinated Axon Action
Potentials
➢ Action potentials are conducted slowly in
unmyelinated axons and more rapidly in
myelinated axons.
➢ Action potentials along unmyelinated axons
occur along the entire membrane.
➢ Action potentials on myelinated axons occur in a
jumping pattern at the nodes of Ranvier.
➢ This type of action potential conduction is called
saltatory conduction.
Axon Conduction Speed
➢ The speed of action potential conduction varies
widely, even among myelinated axons; it is
based on the diameter of axon fibers.
➢ Medium-diameter, lightly myelinated axons,
characteristics of autonomic neurons, conduct
action potentials at the rate of about 3 - 15
meters per second.
➢ Large-diamter, heavily myelinated axons
conduct action potentials at the rate of 15 - 120
m/s.
Synapse
➢ A neuroneuronal synapse is a junction where
the axon of one neuron interacts with another
neuron.
➢ The end of the axon forms a presynaptic
terminal and the membrane of the next neuron
forms the postsynaptic membrane, with a
synaptic cleft between the two membrane.
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➢ Chemical substances called neurotransmitters
are stored in synaptic vesicles in the presynaptic
terminal.
➢ An action potential reaching the presynaptic
terminal causes voltage-gated Ca2+ channels to
open, and Ca2+ moves into the cell.
➢ This influx of Ca2+ causes the release of
neurotransmitters by exocytosis from the
presynaptic terminal
➢ The neurotransmitters diffuse across the
synaptic cleft and bind to specific receptor
molecules on the postsynaptic membrane.
➢ The binding of neurotransmitters to these
membrane receptors causes chemically gated
channels for Na+, K+, or Cl- to open or close in
the postsynaptic membrane.
➢ The specific channel type and whether or not
the channel opens or closes depend on the type
of neurotransmitter in the presynaptic terminal
and the type of receptors on the postsynaptic
membrane.
➢ The response may be either stimulation or
inhibition of an action potential in the
postsynaptic cell.
➢ If Na+ channels open, the postsynaptic cell
becomes depolarized, and an action potential
will result if a threshold is reached.
➢ If K+ or Cl- channels open, the inside of the
postsynaptic cell tends to become more
negative, or hyperpolarized, and an action
potential is inhibited from occurring.
➢ There are many neurotransmitters, with the best
known being acetylcholine and
norepinephrine.
➢ Neurotransmitters do not normally remain in the
synaptic cleft independently, thus their effects
are short duration.
➢ These substances become reduced in
concentration when they are either rapidly
broken down by enzymes within the synaptic
cleft or are transported back into the presynaptic
terminal.
➢ An enzyme called acetylcholinesterase breaks
down the acetylcholine.
➢ Norepinephrine is either actively transported
back into the presynaptic terminal or broken
down by enzymes.
The Synapse
Reflex
➢ A reflex is an involuntary reaction in response to
a stimulus applied to the periphery and
transmitted to the CNS.
➢ Reflexes allow a person to react to stimuli more
quickly than is possible if conscious thought is
involved.
➢ Most reflexes occur in the spinal cord or
brainstem rather than in the higher brain
centers.
➢ A reflex arc is the neuronal pathway by which a
reflex occurs and has five basic components.
Reflex Arc Components
1. A sensory receptor
2. A sensory neuron
3. Interneurons, which are neurons located
between and communicating with two other
neurons
4. A motor neuron
5. An effect organ (muscles or glands)
Note: The simplest reflex arcs do not involve
interneurons.
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Reflex arc
Neuronal Pathway (Converging)
➢ The CNS has simple to complex neuronal
Pathways.
➢ A converging pathway is a simple pathway in
which two or more neurons synapse with the
same postsynaptic neuron,
➢ This allows the information transmitted in more
than one neuronal pathway to converge into a
single pathway.
Neuronal Pathway (Diverging)
➢ A diverging pathway is a simple pathway in
which an axon from one neuron divides and
synapses with more than one other postsynaptic
neuron.
➢ This allows the information transmitted in one
neuronal pathway to diverge intro two or more
pathways.
Neuronal Pathways
Summation
➢ A single presynaptic action potential usually
does not cause the sufficiently large
postsynaptic local potential to reach threshold
and produce an action potential in the target cell
➢ Many presynaptic action potentials are needed
in a process called summation
➢ Summation of signals in neuronal pathways
allows integration of multiple subthreshold local
potentials.
➢ Summation of the local potentials can bring the
membrane potential to a threshold and trigger
an action potential
➢ Spatial Summation
○ Occurs when the local potentials
originate from different locations on the
postsynaptic neuron - for example. From
converging pathways
➢ Temporal Summation
○ Occurs when local potentials overlap in
time
➢ This can occur from a single input that fires
rapidly, which allows the resulting local
potentials to overlap briefly
➢ Spatial and temporal summation can lead to
stimulation or inhibition, depending on the type
of signal.
The Nervous System
➢ The nervous system can be divided into the
central nervous system and the peripheral
nervous system.
➢ The Central Nervous System (CNS), consists of
the brain and spinal cord.
➢ The Peripheral Nervous System (PNS), consists
of all the nerves and ganglia outside the brain
and spinal cord.
Spinal Cord
➢ Extends from the foramen magnum to 2nd
lumbar vertebra
➢ Protected by vertebral column
➢ Spinal nerves allow movement
➢ If damaged paralysis can occur
Gray Matter and White Matter
➢ Gray Matter
○ Center of spinal cord
○ Looks like letter H or a butterfly
➢ White Matter
○ Outside of spinal cord
○ Contains myelinated fibers
White matter in Spinal Cord
➢ Located in the white matter of the CNS are three
columns: dorsal, ventral, and lateral
➢ Columns contain ascending and descending
tracts.
➢ Ascending tracts
○ Axons that conduct action potentials
toward the brain
➢ Descending tracts
○ Axons that conduct action potentials
away from the brain
Gray Matter in Spinal Cord
➢ The gray matter has a letter H shape with horns.
➢ Posterior Horns
○ Contain axons which synapse with
interneurons
➢ Anterior Horns
○ Contain somatic neurons
➢ Lateral Horns
○ Contains autonomic horns
➢ Central Canal
○ Fluid-filled space in the center of cord
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Spinal Cord Cross Section
Reflexes
➢ A reflex is an involuntary reaction in response to
a stimulus applied to the periphery and
transmitted to the CNS.
➢ The simplest reflex is the stretch reflex
○ Stretch Reflex
■ Occurs when muscles contract
in response to a stretching force
applied to them
○ Knee-jerk reflex
■ Or patellar reflex is a classic
example of a stretch reflex.
○ Withdrawal reflex
■ Or flexor reflex, is to remove a
limb or another body part from a
painful stimulus
■ The sensory receptors are pain
receptors, and stimulation of
these receptors initiated the
reflex
Spinal Nerves
➢ Arise along spinal cord from the union of dorsal
roots and ventral roots
➢ Contain axons sensory and somatic neurons
➢ Located between vertebra
➢ Categorized by region of vertebral column from
which it emerges (C for cervical)
➢ 31 pairs
➢ Organized in 3 plexuses
Cervical Plexus
➢ Spinal Nerves C1-4
➢ Innervated muscles attached to hyoid bone and
neck
➢ Contains phrenic nerve which innervated
diaphragm
Brachial Plexus
➢ Originated from spinal nerves C5 - T1
➢ Supply nerves to the upper limb, shoulder, hand
Lumbosacral Plexus
➢ Originated from spinal nerves L1 to S4
➢ Supply nerves lower limbs
Dermatome
➢ The nerves arising from each region of the
spinal cord and vertebral column supply specific
regions of the body
➢ A dermatome is the area of skin supplied with
sensory innervation by a pair of spinal nerves.
➢ Each of the spinal nerves except C1 has a
specific cutaneous sensory distribution.
Brainstem
Components
➢ Medulla oblongata
➢ Pons
➢ Midbrain
Brainstem Components
Medulla Oblongata
➢ Location:
○ Continuous with spinal cord
➢ Function
○ Regulates heart rate, blood vessel
diameter, breathing, swallowing,
vomiting, hiccuping, coughing, sneezing,
balance
➢ Other
○ Pyramids: involved in conscious control
of skeletal muscle
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Pons
➢ Location
○ Above medulla, a bridge between
cerebrum and cerebellum
➢ Function
○ Breathing, chewing, salivation,
swallowing, relay station between the
cerebrum and cerebellum.
Midbrain
➢ Location
○ Above pons
➢ Function
○ Coordinated eye movement, pupil
diameter, turning head toward noise
➢ Other
○ The dorsal part has the four colliculi
which are involved in visual and auditory
reflexes.
Reticular Formation
➢ Location
○ Scattered throughout brainstem
➢ Function
○ Regualates cyclical motor function,
respiration, walking, chewing, arousing
and maintaining consciousness,
regulated sleep-wake cycle
Cerebellum
➢ Location
○ Attached to the brainstem by the
cerebellar peduncles
➢ Characteristics
○ Means little brain
○ Cortex is composed of gyri, sulci, gray
matter
➢ Functions
○ Controls balance
○ Muscle tone
○ Coordination of fine motor
Diencephalon
> Located between the brainstem and cerebrum
Components
➢ Thalamus
➢ Hypothalamus
➢ Epithalamus
Diencephalon Components
Thalamus
➢ Characteristics
○ Largest portion of diencephalon
➢ Function
○ Influences moods and detects pain
Epithalamus
➢ Location
○ Above thalamus
➢ Function
○ Emotional and visceral response to
odors
Hypothalamus
➢ Location
○ Below thalamus
➢ Characteristics
○ Controls pituitary gland and is
connected to it by infundibulum
➢ Function
○ Controls homeostasis, body temp, thirst,
hunger, fear, rage, sexual emotions
Cerebrum Characteristics
➢ Largest portion of brain
➢ Divisions
○ Right hemisphere and left hemisphere
■ Separated by longitudinal
fissure
➢ Lobes
○ Frontal, parietal, occipital, temporal,
insula (fifth lobe)
Cerebrum Components
Cerebral Cortex
➢ Location
○ Surface of cerebrum, composed of gray
matter
➢ Function
○ Controls thinking, communicating,
remembering, understanding, and
initiated involuntary movements
Cerebrum Surface Features
Gyri
➢ Folds on cerebral cortex that increase
surface ares
Sulci
➢ Shallow indentations
Fissure
➢ Deep indentations
Cerebral Hemispheres
Left Hemisphere
➢ Controls right side of body
➢ Responsible for math, analytic, and
speech
Righ Hemisphere
➢ Controls left side of body
➢ Responsible for music, art, abstract
ideas
Corpus Callosum
➢ Connection between the two
hemispheres
Lobes of the Brain
Frontal Lobe
➢ Location
○ Front
➢ Function
○ Control voluntary motor
functions, aggression, moods,
smell
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Parietal Lobe
➢ Location
○ Top
➢ Function
○ Evaluates sensory input such as
touch, pain, pressure,
temperature, taste
Occipital Lobe
➢ Location
○ Back
➢ Function
○ Vision
Temporal Lobe
➢ Location
○ Sides
➢ Function
○ Hearing, smell, memory
Sensory Functions
➢ CNS constantly receives sensory input
➢ We are unaware of most sensory input
➢ Sensory input is vital of our survival and normal
functions.
Ascending Tracts
➢ Ascending pathways are sensory tracts carrying
impulses up the spinal cord to specific areas of
specific of the brain.
➢ Each tract is involved with a limited type of
sensory input, such as pain, temperature, touch,
position, or pressure.
➢ Tracts are usually given composite names that
indicate their origin and termination.
➢ The names of ascending tracts usually begin
with the prefix spino-, indicating that they begin
in the spinal cord, such as the spinothalamic
➢ Sensory tracts typically cross from one side of
the body in the spinal cord or brainstem to the
other side of the body
➢ The left side of the brain receives sensory input
from the right side of the body, and vice versa.
Sensory Areas of Cerebral Cortex
Primary Sensory Areas
➢ Where ascending tracts project
➢ Where sensations are perceived
Primary Somatic Sensory Cortex
➢ General sensory area
➢ In parietal lobe
➢ Sensory input such as pain, pressure, temp.
Somatic Motor Functions
➢ Somatic motor neurons innervate skeletal
muscles
➢ The somatic motor system is responsible for:
○ Maintaining the body’s posture and
balance
○ Moving the trunk, head, limbs, tongue,
and eyes
○ Communicating through facial
expressions and speech
➢ Reflexes mediated through the spinal cord and
brainstem are responsible for some body
movements that are involuntary
➢ Voluntary movements are consciously activated
to achieve a specific goal, such as walking or
typing
➢ Voluntary movement result from the stimulation
of neural circuits that consists of two motor
neurons: upper and lower motor neurons.
➢ Upper motor neurons
○ Have cell bodies in the cerebral cortex
and project down the spinal cord to
synapse with lower motor neurons.
➢ Lower motor neurons
○ Have cell bodies in the anterior horn of
the spinal cord gray matter or in cranial
nerve nuclei
➢ The axons of lower motor neurons leave the
central nervous system and extend through
spinal or cranial nerves to skeletal muscles.
Motor Areas of Cerebral Cortex
Primary Motor Cortex
➢ Frontal lobe
➢ Control voluntary motor movement
Premotor area
➢ Frontal lobe
➢ Where motor functions are organized
before initiation
Prefrontal area
➢ Motivation and foresight to plan and
initiate movement
Sensory and Motor Areas of the Cerebral Cortex
Descending Tracts
➢ Descending tracts are motor tracts carrying
impulses down the spinal cord, either
terminating there or in the brainstem
➢ The corticospinal tracts are considered direct
because they extend directly from upper motor
neurons in the cerebral cortex to lower motor
neurons in the spinal cord.
➢ Some tracts are considered indirect because
they originated in the brainstem but are indirectly
controlled by the cerebral cortex, basal nuclei,
and cerebellum.
➢ Tracts in the lateral columns are most important
in controlling goal-directed limb movements,
such as reaching and manipulating
➢ Tractsin the ventral columns, such as the
reticulospinal tract, are most important for
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maintaining posture, balance, and limb position
through their control of neck, trunk, and proximal
limb muscles.
➢ Crossover of axons in the brainstem or spinal
cord to the opposite side of the body is typical of
descending pathways.
➢ The left side of the brain controls skeletal
muscles on the right side of the body, and vice
versa.
Basal Nuclei
➢ Group of functionally related nuclei
➢ Plan, organize, coordinate motor movements
and posture
➢ Corpus Striatum
○ Deep in cerebrum
➢ Substantia nigra
○ In midbrain
Speech
➢ Mainly in left hemisphere
➢ Sensory Speech (Wernicke’s Area)
○ Parietal lobe
○ Where words are heard and
comprehended
➢ Motor Speech (Broca’s Area)
○ Frontal lobe
○ Where words are formulated
Brain Waves and Consciousness
➢ Used to diagnose and determine treatment for
brain disorders
➢ Electroencephalogram (EEG)
○ Electrodes plated on scalp to record
brain’s electrical activity
Brain Waves
➢ Alpha Waves
○ Person is awake in quiet state
➢ Beta Waves
○ Intense mental activity
➢ Delta Waves
○ Deep sleep
➢ Theta Waves
○ In children
Memory
➢ Encoding
○ Brief retention of sensory input received
by
○ Brain while something is scanned,
evaluated and acted up
○ Also called as sensory memory
○ In temporal lobe
○ Lasts less than a second
➢ Consolidated
○ Data that has been encoded
○ Temporal lobe
○ Short tem memory
➢ Storage
○ Long term memory
○ Few minutes or permanently (depends
on retrieval)
➢ Retrieval
○ How often information is used
Types of Memory
➢ Short-term memory
○ Info. is retained for a few seconds or
min.
○ Bits of info. (usually 7)
➢ Long-term memory
○ Can last for a few minutes or
permanently
➢ Episodic memory
○ Places or events
➢ Learning
○ Utilizing past memories
Limbic System and Emotions
➢ The olfactory cortex and certain deep cortical
regions and nuclei of the cerebrum and the
diencephalon are grouped together under the
title limbic system.
➢ The limbic system influences long-term
declarative memory, emotions, visceral
responses to emotions, motivation, and mood.
➢ A major sources of sensory input to the limbic
system are the olfactory nerves
➢ The limbic system is connected to, and
functionally associated with, the hypothalamus
➢ Lesions in the limbic system can result in
voracious appetite, increased (often perverse)
sexual activity, and docility (including loss of
normal fear and anger responses.)
Meninges
➢ The meninges are three connective tissue layers
that surround the brain and spinal cord.
➢ The outermost (most superficial) meningeal
layer is the dura mater, which is the toughest of
all the meninges.
➢ The dura mater forms two layers around the
brain and only one layer around the spinal cord.
➢ The second meningeal membrane is the very
thin, wispy arachnoid mater.
➢ The space between the dura mater and the
arachnoid mater is the subdural space, which is
normally only a potential space containing a very
small amount of serous fluid
➢ Cerebrospinal flid is and blood vessels are found
in the subarachnoid space
➢ The third meningeal membrane, the pia mater, is
very tightly bound to the surface of the brain and
spinal cord.
Ventricles
➢ The CNS contains fluid-filled cavities, called
ventricles
➢ Each cerebral hemisphere contains a relatively
large cavity called the lateral ventricle
➢ The third ventricle is a smaller, midline cavity
located in the center of the diencephalon
between the two halves of the thalamus and
connected by foramina (holes) to the lateral
ventricles.
➢ The fourth ventricle is located at the base of the
cerebellum and connected to the third ventricle
by a narrow canal, called the cerebral aqueduct.
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➢ The fourth ventricle is continuous with the
central canal of the spinal cord.
➢ The fourth ventricle also opens into the
subarachnoid space through foramina in its
walls and roof.
Cerebrospinal Fluid
➢ Cerebrospinal fluid (CSF)
○ Bathes the brain and spinal cord,
providing a protective cushion around
the CNS
➢ The ependymal cells located in the choroid
plexuses of the ventricles produce the CSF.
➢ CSF fills the brain ventricles. The central canal
of the spinal cord, and the subarachnoid space.
➢ The CSF flows from the lateral ventricle into the
third ventricle and then through the cerebral
aqueduct into the fourth ventricle
➢ A small amount of CSF enters the central canal
of the spinal cord.
➢ The CSF exits the fourth ventricle through small
openings in its walls and rood and enters the
subarachnoid space.
➢ Masses of arachnoid tissue, called arachnoid
granulations, penetrate the superior sagittal
sinus, a dural venous sinus in the longitudinal
fissure, and CSF passes from the subarachnoid
space into the blood through these granulations.
Cranial Nerves
12 pairs of cranial nerves
Named by Roman Numerals
2 categories of functions: sensory and motor
➢ Cranial Nerve I (olfactory) is a pure sensory
nerve for smell
➢ Cranial Nerve II (Optic) is a pure sensory nerve
for vision
➢ Cranial Nerve III (Oculomotor) is a pure motor
nerve for eye movement
➢ Cranial Nerve IV (Trochlear) is a pure motor
nerve for eye movement
➢ Cranial Nerve V (Trigeminal) is both a motor
and sensory nerve. It is sensory for pain, touch,
and temperature for the eye and lower upper
jaws. It is motor for muscles of chewing
➢ Cranial Nerve VI (Abducens) is a pure motor
nerve for eye movement
➢ Cranial Nerve VII (Facial) is both a sensory and
motor nerve. It is sensory for taste and motor for
facial expression.
➢ Cranial Nerve VIII (Vestibulocochlear) is a
pure sensory nerve for hearing and equilibrium
➢ Cranial Nerve IX (Glossopharyngeal) is both a
motor and sensory nerve. It is sensory for taste
and motor for swallowing
➢ Cranial Nerve X (Vagus) is both a motor and
sensory nerve. It is sensory and motor for
organs in the thoracic and abdominal cavities.
➢ Cranial Nerve XI (Accessory) is a pure motor
nerve for the trapezius, sternocleidomastoid,
and muscle of the larynx
➢ Cranial Nerve XII (Hypoglossal) is a pure
motor nerve for the tongue
Autonomic Nervous System
➢ The autonomic neurons innervates smooth
muscle, cardiac muscle, and glands
➢ Autonomic functions are largely controlled
unconsciously
➢ The autonomic nervous system is composed of
the sympathetic division and the
parasympathetic division.
➢ Increase activity in sympathetic neurons
generally prepares the individual for physical
activity, whereas parasympathetic stimulation
generally activated involuntary functions, such
as digestion, that are normally associated with
the body at rest.
➢ In the autonomic nervous system, two neurons
in series extend from the CNS to the effector
organs
➢ The first neuron is called the preganglionic
neuron; the second neuron is the
postganglionic neuron
➢ The neuron are so named because
preganglionic neurons synapse with
postganglionic neurons in autonomic ganglia
within the PNS
Sympathetic Division (figth-or-flight)
➢ The sympathetic division cell bodies of
sympathetic preganglionic neurons are in the
lateral horn of the spinal cord gray matter
between the first thoracic (T1) and the second
lumbar (L2) segments
➢ The axons of the preganglionic neurons exit
through ventral roots and project to either
sympathetic chain ganglia or collateral ganglia
Parasympathetic Division (rest-and-digest)
➢ Some preganglionic cell bodies of the
parasympathetic division are located within the
lateral part of the central gray matter of the
spinal cord in the regions that give rise to spinal
nerves S2 through S4.
➢ Other preganglionic cell bodies of the
parasympathetic division are located within
brainstem nuclei of the oculomotor, facial,
glossopharyngeal, and vagus nerves.
➢ Axons of the preganglionic neurons extend
through the spinal nerves or cranial nerves to
terminal ganglia either located neat effector
organs in the head or embedded in the walls of
effector organs in the thorax, abdomen, and
pelvis
➢ Most of the thoracic and abdominal organs are
supplied by preganglionic neurons of the vagus
nerve extending from the brainstem
ANAPHY | FINALS
Senses
Sense
● Ability to perceive stimuli
Sensation
● Conscious awareness of stimuli recieved by
sensory neurons
Sensory Receptors
● Sensory nerve endings that respond to stimulu
by developing action potentials
Classification of Senses
Types of Senses
General Senses
● Receptors over large part of body that
sense touch, pressure, pain,
temperature, and itch
● Somatic provide information about body
and environment
● Visceral provide information about
internal organs
Special Senses
● Smell, taste, sight, hearing, and balance
Types of Receptors
Mechanoreceptors
● Detect movement
● Example, touch, pressure, vibratiion
Chemoreceptors
● Detect chemicals
● Example, Odors
Photoreceptors
● Detect light
Thermoreceptors
● Detect temp, changes
Nociceptors
● Detect pain
Types of Touch Receptors
Merkel’s disk
● Detect light touch and pressure
Hair Follicle receptors
● Detect light touch
Meissner Corpuscle
● Deep in epidermis
● Localizing tactile sensations
Ruffini Corpuscle
● Deep tactile receptors
● Detects continous pressure in skin
Pacinian Corpuscle
● Deepest receptors
● Associated with tendons and joints
● Detect deep pressure, vibration, position
Sensory Receptors in the Skin
Pain
● Pain is an unpleasant perceptual and emotional
experience
● Pan can be localized or diffuse
○ Localized
■ Sharp, pricking, cutting pain
■ Rapid action potential
○ Diffuse
■ Burning, aching pain
■ Slower action potentials
Pain Control
Local Anesthesia
● Action potentials suppressed from pain
● Receptors in local areas
● Chemical are injected near sensory
nerve
ANAPHY | FINALS
General Anesthesia
● Loss of consciousness
● Chemicals affect reticular formation
Referred Pain
● Originates in a region that is not source of pain
● Felt when internal organs are damaged or
inflamed
● Sensory neurons from superficial area and
neurons of source pain converge onto same
ascending neurons of spinal cord.
Areas of Referred Pain
Olfaction
● Sense of smell
● Occurs in response to odorants
● Receptors are located in the nasal cavity and
hard palate
● We can detect 10,000 different smells
Olfaction Process
1. The nasal cavity contains a thin film of mucous
where odors become dissolved
2. Olfactory neurons are located in mucous.
Dendrites of olfactory neurons are enlarged and
contain cilia
3. Dendrites pick up odor, depolarize, and carry
odor to axons in the olfactory bulb (cranial nerve
I)
4. Frontal and temporal lobes process odor.
Taste
Taste Buds:
● Sensory structure that detects taste
● Located on papillae on the tongue, hard palate,
and throat
● Inside each taste bud are 40 taste cells
● Each taste cell has taste hairs that extend into
taste pores.
Taste Process
1. Taste buds pick up taste and send it to taste
cells
2. Taste cells send taste to taste hairs
3. Taste hairs contain receptors that initiate an
action potential which is carried to parietal lobe
4. Brain processes taste
Types of Tastes
1. Sweet
2. Sour
3. Salty
4. Bitter
5. Umami
*> Certain taste buds are more sensitive to certain tastes
Taste is also linked to smell
Vision
Accessory Structures
Eyebrow
● Protects from sweat
● Shade from sun
Eyelid/Eyelashes
● Protects from foreign objects
● Lubricated by blinking
Conjunctiva
● Thin membrane that covers inner surface of
eyelid
Lacrimal Apparatus
● Produces tears
Extrinsic eye muscles
● Help move eyeball
ANAPHY | FINALS
Anatomy of Eye
● Hollow, fluid filled sphere
● Composed of 3 layers (tunics)
● Divided into chambers
The Eye
Fibrous Tunic
● Outermost Tunic
● Sclera
○ Firm, white outer part
○ Helps maintain eye shape, provides
attachment sites, protects internal
structures
● Cornea
○ Transparent structure that covers iris
and pupil
○ Allows light to enter and focuses light
Vascular Tunic
● Middle tunic
● Contains blood supply
● Choroid
○ Black part (melanin)
○ Delivers O2 and nutrients to retina
● Ciliary Body
○ Helps hold lens in place
● Suspensory Ligaments
○ Help hold lens in place
● Lens
○ Flexible disk
○ Focuses light onto retina
● Iris
○ Colored part
○ Surrounds and regulates pupil
● Pupil
○ Regulates amount of light entering
○ Lots of light = constricted
○ Little light = dilated
Nervous Tunic
● Innermost tunic
● Retina
○ Covers posterior 5⁄6 of eye
○ Contains 2 layers
● Pigmented retina
○ Outer layer
○ Keeps light from reflecting back in eye
● Sensory retina
○ Contains photoreceptors (rods and
cones)
○ Contains interneurons
○ Rods
■ Photoreceptors sensitive to light
■ 20 times more rods than cones
■ Can function in dim light
○ Cones
■ Photoreceptor provide color
vision
■ 3 types blue, green, red
Pigments and Pigment Protein
● Rhodopsin
○ Photosensitive pigment in rod cells
● Opsin
○ Colorless protein in rhodopsin
● Retinal
○ Yellow pigment in rhodopsin
○ Requires vitamin A
Effects of Light in Rhodopsin
1. Light strikes rod cell
2. Retinal changes shape
3. Opsin changes shape
4. Retinal dissociates from opsin
5. Change rhodopsin shape stimulates response in
rod cell which results in vision
6. Retinal detaches from opsin
7. ATP requires to reattach retinal to opsin and
return rhodopsin to original shape
The Retina
● Rods and cones synapse with bipolar cells of
sensory retina
● Horizontal cells of retina modify output of rods
and cones.
● Bipolar and horizontal cells synapse with
ganglion cells
● Ganglion cells axons converge to form optic
nerve
● Macula
○ Small spot near center of retina
● Fovea Centralis
○ Center of macula
○ Where lights is focused when looking
directly at an object
○ Only cones
○ Ability to discriminate fine images
● Optic disk
○ White spot medial to macula
○ Blood vessels enter eye and spread
over retina
○ Axons exit as optic nerve
○ No photoreceptors
○ Called blind spot
Chambers of the Eye
● Anterior Chamber
○ Located between cornea and lens
○ Filled with aqueous humor (watery)
○ Aqueous humor helps maintain
pressure, refracts (bend) light, and
provide nutrients to the inner surface of
eye
● Posterior Chamber
○ Located behind anterior chamber
○ Contains aqueous humor
● Vitreous chamber
○ Located in retina region
○ Filled with vitreous humor: jelly-like
substance
○ Vitreous humor helps maintain pressure,
holds lens and retina in place, refracts
light
ANAPHY | FINALS
Functions of the Eye
● The eye functions much like a camera
● The iris allowed light into the eye, which is
focused by the cornea, lens, and humors onto
the retina
● The light striking the retina produces action
potentials that are relayed to the brain
● Light refraction and image focusing are two
important processes in establishing vision
● Light Refraction
○ Bending of light
● Focal point
○ Point where light rays converge
○ Occurs anterior to retina
○ Objects is inverted
● Focusing images in Retina
○ Accommodation
■ Lens becomes less rounded
and image can be focused on
retina
■ Enables eye to focus in images
closer than 20 feet.
Focusing by the EYe
Neuronal Pathway for Vision
Optic Nerve
● Leaves eye and exits orbit through optic
foramen to enter cranial cavity
Optic Chiasm
● Where 2 optic nerves connect
Optic Tracts
● Route of ganglion axons
Visual Pathway
Visual Defects
Myopia
● Nearsightedness
● Images is in front of retina
Hyperopia
● Farsightedness
● Image is behind retina
Presbyopia
● Lens becomes less elastic
● Reading glasses required
Astigmatism
● Irregular curvature of lens
● Glasses or contacts required to correct
Color blindness
● Absence of deficient cones
● Primarily in males
Glaucoma
● Increase pressure in eye
● Can lead to blindness
ANAPHY | FINALS
The Ear
● The organs of hearing and balance are located
in the ears
● Each ear is divided into three areas:
○ The external ear
○ The middle ear
○ The inner ear
The External Ear
● Extends from outside of head to eardrum
● Auricle
○ Fleshy part on outside
● External auditory meatus
○ Canal leads to eardrum
● Tympanic membrane
○ Eardrum
○ Thin membrane that separates external
and middle ear.
The Middle Ear
● Air filled chamber with ossicles
○ Malleus (hammer)
■ Bone attached to tympanic
membrane
○ Incus (anvil)
■ Bone that connected malleus to
stapes
○ Stapes (Stirrup)
■ Located at base of oval window
● Oval Window
○ Separates middle and inner ear
● Eustachian or auditory tube
○ Opens into pharynx
○ Equalized air pressure between outside
air and middle ear
The Inner Ear
● Set of fluid chambers
○ Bony labyrinth
■ Tunnel filled with fluid
■ 3 regions: cochlea, vestibule,
semicircular canals
○ Membranous labyrinth
■ Inside bony labyrinth
■ Filled with endolymph
● Endolymph
○ Clear fluid in membranous labyrinth
● Perilymp
○ Fluid between membranous and bony
labyrinth
● Cochlea
○ Snail-shell shaped structure
○ Where hearing takes place
○ Scala vestibuli
■ In cochlea
■ Filled with perilymph
○ Scala tympani
■ In cochlea
■ Filled with perilymph
○ Cochlea duct
■ In cochlea
○ Filled with endolymph
● Spinal Organ
○ In cochlear duct
○ Contains hair cells
● Tectorial membrane
○ In cochlea
○ Vibrates against hair cells
● Hair cells
○ Attached to sensory neurons that when
bent produce an action potential
● Vestibular membrane
○ Wall of membranous labyrinth that lines
scala vestibuli
● Basilar membrane
○ Wall of membranous labyrinth that lines
scala tympani
Hearing Process
1. Sound travels in waves through air and is
funneled into ear by auricle
2. Auricle through external auditory meatus to
tympanic membrane
3. Tympanic membrane vibrates and sound is
amplified by malleus, incus, stapes which
transmit sound to oval window.
4. Oval window produces waves in perilymph of
cochlea.
5. Vibrations of perilymph cause vestibular
membrane and endolymph to vibrate
6. Endolymph cause displacement of basilar by
hair cells in spiral organ
7. Hair cells become bent and cause action
potential is created.
Balance (Equilibrium)
● Static equilibrium
○ Associated with vestibule
○ Evaluates position of head relative to
gravity
● Dynamic equilibrium
○ Associated with semicircular canals
○ Evaluates changes in direction and rate
of head movement
Balance
● Vestibule
○ Inner ear
○ Contains utricle and saccule
● Maculae
○ Specialized patches of epithelium in
utricle and saccule surround by
endolymph
○ Contain hair cells
● Otoliths
○ Gelatinous substance that moves in
response to gravity
○ Attached to hair cell microvilli which
initiate action potentials.
● Semicircular canals
○ Dynamic equilibrium
○ Sense movement if any direction
● Ampulla
○ Base of semicircular canal
● Crists ampullaris
○ In ampulla
● Cupula
○ Gelatinous mass
○ Contains microvilli
○ Float that is displaced by endolymph
movement
ANAPHY | FINALS
Urinary System
● The urinary system is the major exam excretory
system of the body
● Some organs in other systems also eliminate
wastes, but they are not able to compensate in
the case of kidney failure.
Urinary System Functions
● Excretion
● Regulation of blood volume and blood pressure
● Regulation of blood solute concentration
● Regulation of extracellular fluid pH
● Regulation of red blood cell synthesis
● Regulation of Viramin D synthesis
Components of the Urinary system
● Two kidneys
● Two ureters
● One urinary bladder
● One urethra
Kidney Characteristics
● Bilateral retroperitoneal organs
● Shape and Size:
○ Bean shaped
○ Weighs 5 ounces (bar of soap or size of
fist)
● Location
○ Between 12th thoracic and 3rd lumbar
vertebra
● Renal Capsule
○ Connective tissue around each kidney
● Renal cortex
○ Outer portion
● Renal medulla
○ Inner portion
● Renal pyramid
○ Junction between cortex and medulla
● Calyx
○ Tip of pyramids
● Renal pelvis
○ Where calyces join
○ Narrows to form ureter
Nephron
● The nephron is the functional unit of the kidney
● Each kidney has over one millio-n nephrons
● There are two types of nephrons in the kidney
○ Juxtamedullary
○ Cortical
● Approximately 15% are juxtamedullary
● The nephron includes the renal corpuscle,
proximal tubule, loop of henle, distal tubule and
collecting duct
Nephron Components
● Renal Corpuscle
○ Structure that contain a Bowman’s
capsule and glomerulus
● Bowman’s capsule
○ Enlarged end of nephron
○ Opens into proximal tubule
○ Contains podocytes (specialized cells
around glomerular capillaries)
● Glomerulus
○ Contains capillaries wrapped around it
● Filtration membrane
○ In renal corpuscle
○ Includes glomerular capillaries,
podocytes, basement membran
● Filtrate
○ Fluid that passes across filtration
membrane
ANAPHY | FINALS
● Proximal tubule
○ Where filtrates passes first
● Loop of Henle
○ Contains descending and ascending
loops
○ Water and solutes pass through thin
walls by diffusion
● Distal tubule
○ Structure between loop of henle and
collecting duct
● Collecting duct
○ Empties into calyces
○ Carry fluid from cortex through medulla
Flow of Filtrate through Nephron
1. Renal corpuscle
2. Proximal tubule
3. Descending loop of Henle
4. Ascending loop of Henle
5. Distal tubule
6. Collecting duct
7. Papillary duct
Blood Flow through kidney
1. Renal artery
2. Interlobar artery
3. Arcuate artery
4. Interlobar artery
5. Afferent arteriole
6. Glomerulus
7. Efferent arteriole
8. Peritubular capillaries
9. Vasa recta
10. Interlobular vein
11. Arcuate vein
12. Interlobar vein
Urine Formation
● Urine formation involves three processes
○ Filtration
■ Occurs in the renal corpuscle
○ Reabsorption
■ It involves removing substances
from the filtrate and placing
back into the blood
○ Secretion
■ It involves taking substances
from the blood at a nephron
area other than the renal
corpuscle and putting back into
the nephron tubule.
Urine Formation-Filtration
● Movement of water, ions, small molecules
through filtration membrane into Bowman’s
capsule
● 18% of plasma becomes filtrate
● 180 liters of filtrate are produces by the
nephrons each day
● 1% of filtrate (1.8 liters) become urine test is
reabsorbed.
● Only small molecules are able to pass through
filtration membrane
● Formation of filtrate depends on filtration
pressure
● Filtration pressure forces fluid across filtration
membrane
ANAPHY | FINALS
● Filtration pressure is influenced by blood
pressure
Urine Production-Reabsorption
● 99% of filtrate is reabsorbed and reenters
circulation
● Proximal tubule is the primary site for
reabsorption of solutes and water
● Descending loop of Henle concentrates filtrate
● Reabsorption of water and solutes from distal
tubule and collecting duct is controlled by
hormones.
Urine Formation
Urine Concentration
● The descending limb of the loop of Henle is a
critical site for water reabsorption (osmosis)
● The filtrate leaving the proximal convoluted
tubule is further concentrated as it passes
through the descending limb of the loop of Henle
● The mechanism for this water reabsorption is
osmosis.
● The renal medulla contains very concentrated
interstitial fluid that has large amounts of Na+,
Cl-, and urea.
● The wall of the thin segment of the descending
limb is highly permeable to water
● As the filtrate moves through the medulla
containing the highly concentrated interstitial
fluid, water is reabsorbed out of the nephron by
osmosis
● The water enters the vasa recta
● The ascending limb of the loop of Henle dilutes
the filtrate by removing solutes
● The thin segment of the ascending limb is not
permeable to water, by it is permeable to solutes
● Consequently, solutes diffuse out of the nephron
Urine Production - Secretion
● Tubular secretion removes some substances
from the blood
● These substances include by-products of
metabolism that become toxic in high
concentrations and drugs or other molecules not
normally produced by the body
● Tubular secretion occurs through either active or
passive mechanisms.
● Ammonia secretion is passive
● Secretion of H+, K+, creatinine, histamine, and
penicillin is by active transport
● These substances are actively transported into
the nephron
● The secretion of H+ plays an important role in
regulating the body fluid pH.
Urine Concentration and Volume Regulation
● Three major hormonal mechanisms are involved
in regulating urine concentration and volume:
1. Renin-angiotensin-aldosterone
2. The antidiuretic hormone (ADH)
3. The atrial natriureticic hormone
Renin-Angiotensin-Aldosterone Mechanism
1. Renin acts on angiotensin to produce
angiotensin I
2. The angiotensin-converting enzyme converts
angiotensin I to angiotensin II
3. Angiotensin II causes vasoconstriction
4. Angiotensin II acts on adrenal cortex to release
aldosterone
5. Aldosterone increases rate of active transport of
Na+ in distal tubules and collecting duct
6. Volume of water in urine decreases.
Antidiuretic Hormone Mechanism
1. ADH is secreted by the posterior pituitary gland
2. ADH acts of kidneys, causing them absorb more
water (decrease urine volume)
3. Result is to maintain a normal blood volume and
blood pressure
Atrial Natriuretic Hormone
1. ANH is secreted from cardiac muscle in the right
atrium of the heart when blood pressure
increases
2. ANH acts on kidneys to decrease Na+
reabsorption
3. Sodium ions remain in nephron to become urine
4. Increased loss of sodium and water reduced
blood volume and blood pressure
ANAPHY | FINALS
Ureters and Urinary Bladder
● Ureter
○ Small tubes that carry urine from renal
pelvis of kidney to bladder
● Urinary Bladder
○ In pelvic cavity
○ Stores urine
○ Can hold a few ml to a maximum of
1000 milliliters
Urethra
● Tube that exits bladder
● Carries urine from urinary bladder to outside of
the body
Urine Movement
● Micturition reflex
○ Activated by stretch of urinary bladder
wall
○ Action potentials are conducted from
bladder to spinal cord through pelvic
nerves
○ Parasympathetic action potentials cause
bladder to contract
○ Stretching of bladder stimulates sensory
neurons to inform brain person needs to
urinate.
Body Fluid Compartments
● The intracellular fluid compartment includes
the fluid inside all the cells of the body
● Approximately two-thirds of all the water in the
body is in the intracellular fluid compartment
● The extracellular fluid compartment includes
all the fluid outside the cells
● The extracellular fluid compartment includes,
interstitial fluid, plasma, lymph, and other special
fluids, such as joint fluid, and cerebrospinal fluid.
Composition of Fluids
● Intracellular fluid contains a relatively high
concentration of ions, such as K+, magnesium,
phosphate, and sulfate compared to the
extracellular fluid
● It has lower concentration of sodium, calcium,
Cl-, and HCO3, than does the extracellular fluid.
Exchange Between Fluid Compartments
● The cell membranes that separate the body fluid
compartments are selectively permeable
● Water continually passes through them, but ions
dissolved in the water do not readily pass
through the cell membrane
● Water movement is regulated mainly by
hydrostatic pressure differences and osmotic
differences and osmotic differences between
the compartments.
● Osmosis controls the movement of water
between the intracellular and extracellular
spaces.
Regulation of Extracellular Fluid Composition
Thirst Regulation
● Water intake is controlled by the thirst
center located in the hypothalamus
● When the concentration of ions in the
blood increases, it stimulated the thirst
center to cause thirst
● When water is consumed, the
concentrations of blood ions decreases,
due to a dilution effect; this causes the
sensation of thirst to decrease
Ion Concentration Regulation
● Regulating the concentrations of
positively charged ions, such as Na+,
K+, and Ca2+, in the body fluids is
particularly important
● Action potentials, muscle contraction,
and normal cell membrane permeability
depend on the maintenance of a narrow
these concentrations.
● Negatively charged ions, such as Cl-,
are secondarily regulated by the
mechanisms that control the positively
charged ions
● The negatively charged ions are
attracted to the positively charged ions;
when the positively charged ions are
transported, the negatively charged ions
move with them.
Sodium Ions
● Sodium ions (Na+) are the dominant ions in the
extracellular fluid.
● About 90 - 95% of the osmotic pressure of the
extracellular fluid results from sodium ions and
from the negative ions associated with them
● Stimuli that control aldosterone secretion
influence the reabsorption of Na+ from nephrons
of the kidneys and the total amount of Na+ in the
body fluids
● Sodium ions are also excreted in sweat.
Potassium Ions
● Electrically excitable tissues, such as muscles
and nerves, are highly sensitive to slight
changes in the extracellular K+ concentration
● The extracellular concentration of K+ must be
maintained within a narrow range for these
tissues to function normally
● Aldosterone plays a major role in regulating the
concentration of K+ in the extracellular fluid
Calcium Ions
● The extracellular concentration of calcium is
maintained within a narrow range
● Increases and decreases in the extracellular
concentration of Calcium have dramatic effects
on the electrical properties of excitable tissues
● Parathyroid Hormone (PTH)
○ Secreted by the parathyroid glands,
increases extracellular Ca2+
concentrations
● Calcitonin
○ Reduces the blood Ca2+ concentration
when it is too high
ANAPHY | FINALS
Phosphate and Sulfate Ions
● Some ions, such as phosphate ions and sulfate
ions, are reabsorbed by active transport in the
kidneys
● The rate of reabsorption is slow, so that id the
concentration of these ions in the filtrate exceed
the nephron’s ability to reabsorb them, the
excess is excreted into the urine
● As long as the concentration of these ions is low,
nearly all of them are reabsorbed by active
transport.
Regulation of Acid-Base Balance
Buffers
● Chemicals resist change in pH of a solution
● Buffers on body contain salts of weak acids or
bases that combine with H+
● Three classes of buffers: proteins, phosphate
buffer, bicarbonate buffer
Respiratory system involvement in acid-base
● Responds rapidly to changes in pH
● Increased respiratory rate raises blood pH (more
alkalotic) due to increased rate of carbon dioxide
elimination from the body
● Reduced respiratory rate reduces pH (more
acidic) due to decreased rate of carbon dioxide
elimination from the body.
Kidney Involvement in acid-base
● Nephrons secrete H+, into urine and directly
regulate pH of body fluids
● More H+ secretion if the pH decreasing and less
H+ secretion if pH is increasing
Acidosis and Alkalosis
● Acidosis occurs when the pH of blood falls
below 7.35
● There are two types of acidosis based upon the
cause: respiratory and metabolic
● Alkalosis occurs when the pH of blood increases
above 7.45
● There are two types of alkalosis based upon the
cause: respiratory and metabolic
ANAPHY | FINALS
REPRODUCTIVE SYSTEM
● The human species could not survive without a
functional male and female reproductive
systems.
● The reproductive systems play essential roles in
the development of the structural and functional
differences in human behavior, and produce
offspring
● However, a reproductive system, unlike other
organs system, is not necessary for the survival
of an individual human.
Reproductive System Functions
1. Production of gametes
2. Fertilization
3. Development and nourishment of a new
individual
4. Production of reproductive hormones
Formation of Gametes
Gametes:
● Sex cells
● Sperm in males
● Oocytes (eggs) in females
Meiosis:
● A special type of cell division that leads to the
formation of sex cells
* Each sperm cell and each oocyte contains 23
chromosomes.
Meiosis
1. Before meiosis begins, all the chromosomes are
duplicated
2. At the beginning of meiosis, each of the 46
chromosomes consists of 2 chromatids
connected by a centromere
3. The chromosomes align as pairs in a process
called synapsis
4. Because each chromosome consists of 2
chromatids, the pairing of the chromosomes
brings 2 chromatids of each chromosome close
together.
5. Genetic material is exchanged on occasion,
when a part of a chromatid of 1 chromosome
breaks off and is exchanges with part of another
chromatid from the other chromosome, in a
process termed, crossing over
6. Meiosis I produces 2 cells, each having 23
chromosomes composed of 2 chromatids joined
at a centromere
7. During Meiosis II, each of the 2 cells divide into
2 cells, and the centromere breaks, giving
separate chromosomes
8. The final result from meiosis are four cells, each
having 23 chromosomes.
*Since the number of chromosomes are reduced during
the process of dividing into 4 cells, the process is a
reduction division process.
From Fertilization to Fetus
Fertilization
● Union of sperm and oocyte
Zygote
● What develops after fertilization
● Develops into an embryo 3 - 14 days after
fertilization
Embryo
● 14 - 56 days after fertilization
Fetus
● 56 days after fertilization
Male Reproductive System
● The male reproductive system consists of the
testes, a series of ducts, accessory glands, and
supporting structures.
● The ducts include the epididymis, the ductus
deferens, and the urethra
● Accessory glands include the seminal vesicles,
the prostate gland, and the bulbourethral glands.
● Supporting structures include the scrotum and
the penis.
Scrotum
● Contains testes
● Contains dartos muscle that moves scrotum and
testes close to and away from body depending
on temp.
● Sperm must develop at temp. Less than body
temp.
Testes
● Primary male reproductive organ
● Produces sperm
● In scrotum
● Contain seminiferous tubules: where sperm is
produced.
● Contain interstitial cells: secrete testosterone
● Contain germ cells: cells that sperm cells arise
from
● Contain sustentacular cells: nourish germ cells
and produce hormones.
Epididymis
● Thread-like tubules on side of each testis
● Where seminiferous tubules empty new sperm
● Where sperm continue to mature and develop
ability to swim and bind to oocytes
ANAPHY | FINALS
Ductus deferens
● “Vas deferens”
● Extends from the epididymis and joins seminal
vesicle
● Cut during a vasectomy
Urethra
● Extends from the urinary bladder to end of penis
● Passageway for urine and male reproductive
fluids
Penis
● Corpus cavernosum, corpus spongiosum,
spongy urethra:
● 3 columns of erectile tissue which fill with blood
for erection
● Transfer sperm from male to female
● Excrete urine
Male Reproductive System Glands
Seminal Vesicles
● Next to ductus deferens
● Helps form ejaculatory duct
Prostate gland
● Surrounds urethra
● Size of a walnut
Bulbourethral gland
● Small mucus-secreting glands near the base of
prostate gland
Secretions
Semen
● Mixture of sperm and secretions from
glands
● Provides a transport medium and
nutrients that
● Protect and activate sperm
● 60% of fluid is from seminal vesicles
● 30% of fluid is from bulbourethral gland
● 5% of fluid is from testes
Seminal Vesicles:
● Provide fructose
● Contain prostaglandins which decrease
mucus thickness around cervix and
uterine tubues and help sperm move
through femal repro. Tract
● Contains coagulants that help deliver
semen into the female
Prostate gland
● Contains enzyme to liquefy semen after
it is inside the female
● Neutralized acidity of vagina
Bulbourethreal gland
● Neutralizes acidity of the male urethra
and female vagina
Testicular secretions
● Include sperm and a small amount of fluid
● 2 - 5 ml of semen is ejaculated each time 1
milliliter of semen contains 100 million sperm.
● Sperm can live for 72 hours once inside the
female
Path of Sperm
1. Sperm develop in seminiferous tubules (testes)
2. Epididymis (mature)
3. Ductus deferens
4. Receive secretions from seminal vesicles,
prostate gland, and bulbourethral gland
5. Urethra, where semen (sperm) exits the body
Spermatogenesis
● Formation of sperm cells,
● Begins at puberty
● Interstitial cells increase in number and size
● Seminiferous tubules enlarge
● Seminiferous tubules produce germ cell and
sustentacular cells
Production of Sperm Cells
1. Germ cells
2. Spermatogonia
3. Primary spermatocytes
4. Secondary Speratocytes
5. Spermatids
6. Sperm cells
ANAPHY | FINALS
Sperm cell structure
Head
● Contain nucleus and DNA
Midpiece
● Contain mitochondria
Tail
● Flagellum for movement
Male Sex Hormones
● Gonadotropin-releasing hormone (GnRH)
○ is produced in the hypothalamus and
stimulates the secretion of LH and FSH
● Luteinizing Hormone (LH)
○ is produced in the anterior pituitary and
stimulates the secretion of testosterone
● Follicle-stimulating hormone (FSH)
○ is produced in the anterior pituitary and
prompts spermatogenesis
● Testosterone
○ Is produces in the interstitial cells in the
testes and is involves in development
and maintenance of reproductive organs
● Inhibin
○ Secreted by cells of the seminiferous
tubules and inhibits FSH secretion
Male Puberty
● Sequence of events in which a boy begins to
produce male hormones and sperm cells
● Begins at 12 to14 and ends around 18
● Testosterone is major male hormone
● Secondary Sexual Characteristics develop:
○ Example - skin texture, Fat distribution,
hair growth, skeletal muscle growth, and
larynx changes.
Male Sex Act
● The male sex act is a complex series of reflexed
that result in the erection of the penis, secretion
of mucus into the urethra, emission, and
ejaculation.
● Emission
○ Is the movement of sperm cells, mucus,
prostatic secretions, and seminal vesicle
secretions into the prostatic,,
membranous, and spongy urethra
● Ejaculation
○ Is the forceful expulsion of the
secretions that have accumulated in the
urethra to the exterior.
● Sensations, normally interpreted as pleasurable,
occur during the male sex act and result in
intense sensations called an orgasm
● A phase called resolution occurs after
ejaculation in which the penis becomes flaccid,
an overall feeling of satisfaction exists, and the
male is unable to achieve an erection and a
second ejaculation.
Penile Erection
● Erection
○ Is the first major component of the male
sex act.
● Neutral stimuli cause the penis to enlarge and
become firm
● Specifically, parasympathetic action potentials
from the sacral region of the spinal cord cause
the arteries that supply blood to the erectile
tissues to dilate.
● Blood then fills small venous sinuses called
sinusoids in the erectile tissue and compresses
the veins, which reduced blood flow from the
penis
Penis Ejaculation
● Ejaculation
○ Results from the contraction of smooth
muscle in the wall of the urethra and
skeletal muscles surrounding the base
of the penis.
● Just before ejaculation, action potentials are
sent to the skeletal muscles that surround the
base of the penis
● Rhythmic contractions are produced that force
the semen out of the urethra, resulting in
ejaculation.
● In addition, muscle tension increases throughout
the body.
Female Reproductive System
● The female reproductive organs consist of the
ovaries, the uterine tubes, the uterus, the
vagina, the external genitalia, and the mammary
glands.
● The internal reproductive organs of the female
are located within the pelvis, between the
urinary bladder and the rectum.
Female Pelvis
Female Reproductive Organs
ANAPHY | FINALS
Ovaries
● Primary female reproductive organ
● Produces oocytes and sex hormones
● One on either side of uterus
● Ovarian ligaments: anchor ovaries to uterus
● Suspensory ligaments: anchor ovaries to pelvic
cavity
● Ovarian follicle: cells in ovaries that contain
oocytes
Structure of Ovary and Ovarian Follicles
Uterine (Fallopian) Tubes
● Part of uterus which extends toward ovaries and
receive oocytes
● Fimbriae are fringe-like structures around the
opening of uterine tubes that help sweep oocyte
into uterine tubes
● Tubal ligation (sterilization of female)
Uterus
● Pear sized structure located in pelvic cavity
● Functions: receive, retain, provide nourishment,
for fertilized oocyte, where embryo resides and
develops
● Body: main part
● Cervix: a narrow region that leads to vagina
● Uterus wall layers
○ Perimetrium (serous): outermost layer
○ Myometrium (muscular): middle layer
○ Composed of smooth muscle
○ Endometrium: innermost layer that is
sloughed off during menstruation.
Vagina
● Extends from uterus to outside of body
● Female copulation organ that receives penis
during intercourse
● Allows menstrual flow
● Involved in childbirth
● Contains very muscular walls and a mucous
membrane
● Very acidic to keep bacteria out
External Female Genitalia
Vulva
● External female sex organs
● Mons, pubis, labia majora, and minora,
clitoris, and vestibule.
Mons Pubis
● Fatty layer of skin covering pubic
symphysis
Labia Majora
● Larger, outer folds of skin
● Equivalent to male scrotum
Labia Minora
● Thin, inner folds of skin
Clitoris
● Small erectile structure located in
vestibule
● Equivalent to male penis
Prepuce
● Where 2 labia minora unite over clitoris
Vestibule
● Space in which vagina and urethra are
located
Ovulation
● Release of an oocyte from the ovary
● Due to LH secreted from the anterior pituitary
Corpus Luteum
● Mature follicle after ovulation
● Degenerates if the egg is not fertilized
Oogenenis and Fertilization
● Females are born with all of their oogonia (2
million), unlike males that only begin to produce
sperm during puberty.
● At puberty about 300,000 to 400,000 oogonia
are left
● Puberty to menopause, FSH stimulates several
follicles to begin developing during each
menstrual cycle but only 1 follicle should be
ovulated.
● Oocytes are swept into one of uterine tubes by
fimbriae
● If sperm is present in uterine tube during
ovulation oocyte could be fertilized.
● If fertilization occurs then zygote implants in
uterus
● Oocyte only lives for 24 hours, so if no sperm is
present at ovulation no zygote develops and
oocyte dies
Female Puberty
● Begins between 11 - 13 and is usually
completed by 16
● Menarche - first episode of menstrual bleeding
● Vagina, uterus, uterine tubes, and external
genitalia to enlarge and fat is deposited in breast
and hops
ANAPHY | FINALS
● Elevated levels of estrogen and progesterone
are secreted by ovaries
Mammary Glands
● Organs of milk production in breasts
● Modified sweat glands
● Female breasts begin to enlarge during puberty
● Consists of lobes covered by adipose
● Lobes, ducts, lobules are altered during lactation
to expel milk
Female Sex Hormones
● Gonadotropin-releasing (GnRH) hormone is
produced in the hypothalamus and stimulates
secretion of LH and FSH
● Luteinizing Hormone (LH) is produced in the
anterior pituitary and causes ovulation
● Follicle-stimulating hormone (FSH) is produce
in the anterior pituitary and prompts follicles in
the ovaries to begin development
● Estrogen
○ Proliferation of endometrial cells
○ Development of mammary glands
(especially duct system)
○ Control of LH and FSH secretion
○ Development and maintenance of
secondary sex characteristics.
● Progesterone
○ Enlargement of endometrial cells and
secretion of fluid from uterine glands
○ Maintenance of pregnancy state
○ Development of mammary glands
(especially alveoli)
○ Control of estrogen, FSH, and LH
secretion
○ Development of secondary sex
characteristics
Menstrual Cycle
● series of changes that occur in sexually mature,
nonpregnant females
Menses
● Time, when the endometrium is shed from
uterus ● Average, is 28 days and results from
cyclical changes that occur in the endometrium
Stages of Menstrual Cycle
● Days 1 - 5 Menses (Shedding of
endometrium)
○ Menstrual bleeding (menses)
○ Estrogen and progesterone levels are
low
○ Follicle begins to mature
● Days 6 - 13 Proliferative (between the end of
menses and ovulation)
○ Endometrium rebuilds
○ Estrogen levels being to increase
○ Progesterone levels remain low
○ Follicle matures
● Day 14 Ovulation
○ Oocyte is release due to LH
○ Estrogen levels high
○ Progesterone levels are increasing
○ Cervical mucus thins
● Days 15 - 28 Secretory (between ovulation
and next menses)
○ Endometrium is preparing for
implantation
○ Estrogen levels decreases (low)
○ Progesterone levele high
○ Cervical mucus thickens
Menopause
● Time when overies secrete less hormones and
number of follicle in ovaries is low
● Menstrual cycle and ovulation are less regulat
● Hot flashes, fatigue, irritability may occur
● Estrogen replacement therapy may be used to
decrease side effects
Female Sexual Behavior
● Sexual drive in females, liek sexual drives in
males, is dependent on hormones
● Testosterone-like hormones, and possibly
estrogen, affect brain cells (especially in the
area of the hypothalamus) and influence sexual
behavior
● Testosterone-like hormones are produced
primarily in the adrenal cortex.
Female Sex Act
● During sexual excitement, erectile tissue within
the clitoris and around the vaginal opening
becomes engorged with blood.
● The mucous glands within the vestibule secrete
small amounts of mucus, with larger amounts
extruded into the vagina through its walls
● Stimulation of the female’s genitals during
sexual intercourse and psychological stimuli
normally trigger an orgasm or climax
Contraception
● Many methods are used to prevent pregancy,
either by preventing fertilization (contraception)
or by preventing implantation of the developing
embryo.
● Methods include behavioral, barrier, chemical,
and surgical