A&P Chapter 8: CNS and Nervous tissue

what are neuroglia and what are their characteristics

the supporting cells of nervous tissue support the neurons, maintain interstitial fluid, and undergo mitosis

What are neurons and what are their characteristics

neurons are the communication cells of nervous tissue that use electrical signals to send messages and require a lot of ATP to function

what are the four neuroglia of the CNS

astrocytes, microglia, ependymal cells, and oligodendrocytes

what are the functions of astrocytes

maintaining the blood-brain barrier, and maintaining the ion concentrations of the interstitial fluid

what is the function of microglia

the macrophages, immune cells of the nervous system that present antigens to the immune system

what is the function and the locations of ependymal cells

assist in the synthesis and movement of cerebrospinal fluid, they lines the ventricles and central canal of the spinal cord

what is the function of oligodendrocytes

myelinating axons

what is the most numerous neuroglial cell

astrocytes

what are the neuroglia of the PNS

satellite cells and schwann cells

what are the functions of satellite cells, and where are they located on the neuron

they are wrapped around the cell body of the neuron. They regulate ions in the interstitial fluid and regulate exchanges with capillaries

what is the function of Schwann cells, and where are they located on a neuron

they are around a PNS neuron’s axon. they build myelin sheaths

what are the five main components of a neuron and their functions

• soma (cell body): where neuron organelles are stored

• dendrites: location where messages are received

• axon hillock: location where messages are coordinated

• axon: location where messages travel

• axon terminal: location where messages are passed along to another cell

what determines whether a neuron is unipolar, bipolar, or multipolar, and what do these processes comprise of on each neuron

the amount of processes coming from the cell body

multipolar: one axon and the rest are dendrites

bipolar: one axon and one dendrite

unipolar: one axon

what are the locations of multipolar, bipolar, and unipolar neurons

multipolar: autonomic ganglia and throughout the CNS

bipolar: special senses

unipolar: general senses, cerebellum

what are the three functional classifications of neurons and their functions

sensory: afferent, carry info away from the receptor to the CNS

motor: efferent, carry info from the CNS to the effectors

interneuron: relay sensory information

how do the functional classifications and structural classifications of neurons overlap

multipolar: most are interneurons, some are motor

bipolar: all are sensory

unipolar: most are sensory

what are the ion concentrations of these ions with respect to their place in the cell: Na+, K+, Cl-

Na+: high outside, low inside

K+: low outside, high inside

Cl-: high outside, low inside

what initiates an electrical signal in a neuron, and what is the name of this message

a change in resting membrane potential, it is called an action potential

what is potential, graded potential, and action potential

• potential: difference in electrical charge between two points (voltage)

• graded potential: several small changes in the membrane potential that sum up to an action potential

• action potential: the rapid change in electrical potential across a cell membrane

what is depolarization and repolarization

depolarization is a higher positive charge in the cell, and repolarization is a higher negative charge in the cell

what value is resting potential, and what value is threshold value

• resting potential: -70mV

• threshold value: -55mV

what is threshold value

the voltage value that the neuron must reach in order for the voltage-gated Na+ channels to open, leading to rapid depolarization

what are the phases of a signal being propagated

1. Resting phase A: both gates closed, -70mV

2. Resting phase B: both gates closed, chemically gated Na+ gate opens, graded potential changes enough to hit threshold and neuron generates action potential at axon hillock, -55mV

3. Absolute refractory period A: voltage Na+ gate opens, Na+ flows into cell and neuron is depolarized, +30mV

4. Absolute refractory period B: voltage Na+ gate inactivated by blocking gate, voltage K+ gate opens, K+ flows out of cell and neuron is repolarized, -70mV

5. Relative refractory period: voltage Na+ gate closed, voltage K+ gate open, K+ flows out of cell and neuron is hyperpolarized, -90mV

6. New action potentials can be generated if threshold is met (-55mV). If not, neuron returns to rest, -70mV

If graded potentials change the membrane potential enough to hit threshold, where does the neuron generate the action potential

axon hillock

during which phase of signal propagation can new action potentials can be generated

relative refractory period

is unmyelinated axons, the signal is regenerated ____ often than in a myelinated axon

more often

what is continuous and saltatory conduction

continuous: slower, in smaller unmyelinated axons, signal constantly refreshed

saltatory: faster, in larger myelinated axons, signal refreshed at nodes of Ranvier

what is the signal propagating process after the action potential reaches the axon terminal

1. voltage gated Ca2+ channels open

2. Ca2+ binds to vesicles containing neurotransmitters

3. Vesicles exocytosis the neurotransmitters into the synaptic cleft

4. Neurotransmitters hit the chemically gated sodium channels

how to neurons communicate with each other

neurotransmitters released from the pre-synaptic neuron to the post-synaptic neuron at the synaptic cleft

what are the three different synapse locations

axosomatic: in front of the post-synaptic neuron cell body (soma)

axodendritic: in front of the post-synaptic neuron dendrites

axoaxonal: in front of the post-synaptic neuron axon hillock

what are the two types of neurotransmitters, their effects, and the receptors they bind to

• Excitatory neurotransmitter: bind to Na+ chemical gated ion channels and depolarizes (more positive) the neuron to bring it close to threshold. EPSP

• Inhibitory neurotransmitter: bind to Cl- (sometimes K+) chemical gated ion channels and repolarizes (more negative) the neuron to bring it farther away from threshold. IPSP

what is summation, and the difference between temporal and spatial summation

• summation: the combined effects of all the neurotransmitters affecting a single neuron

• temporal summation: all neurotransmitters are coming from one neuron

• spatial summation: all neurotransmitters are coming from multiple neurons

what are the two types of neurotransmitter receptors, their effects, and the mechanisms

• ionotropic (ligand-gated ion channels): neurotransmitter binds, ions flow through,

  • fast and short lived effects

• metabotropic (G-protein coupled receptors): neurotransmitter binds, G-protein activates, enzyme activates, 2nd messenger activates, ions flow through

  • slow and long lasting effects

what is the functional class, receptor type, and function of acetylcholine

• both inhibitory and excitatory class

• both ionotropic and metabotropic receptor types

• it contracts skeletal muscles and completes parasympathetic responses

what are the three ways that excess neurotransmitters are eliminated

• neurotransmitters broken down by enzymes in the synapse

• neurotransmitters uptaken by presynaptic neuron

• neurotransmitters taken by astrocytes and deposited elsewhere

what are the two factors that determine the strength of the response from the brain

• the frequency of action potentials in a single receptor

• the amount of receptors activated

what is serial and parallel processing, and provide an example

serial processing: one sensation triggers one pathway

• EX: reflexes

parallel processing: one sensation triggers multiple pathways

• EX: visual perception

what is neuroplasticity and when does it occur

the ability for the nervous system to change and adapt, it occurs during learning and memory formation

Is neuron repair easier in the CNS or PNS, and what are the three reasons for this difference

easier in the PNS because:

• prevented by oligodendrocytes

• lack of growth factors

• astrocytes make scar tissue

what are the seven major structures of the central nervous system (CNS)

• cerebrum

• diencephalon

• midbrain

• pons

• medulla oblongata

• cerebellum

• spinal cord

what are the two types of matter in the CNS, and what do they each consist of

white matter: myelinated axons

gray matter: nonmyelinated axons, dendrites, cell bodies

what are the four layers of protection that the CNS has (outer to inner)? what are the inner three layers called?

1. cranial and facial bones

2. dura mater: 2 layers in brain, 1 in spinal cord

3. arachnoid mater: spiderweb-like extensions and cerebrospinal fluid fill the space

4. pia mater

The three inner layers are called the meninges

what is the composition of the blood-brain barrier (BBB)

capillaries with a thicker basement membrane, surrounded by endothelial cells with tight junctions between them, and astrocyte processes surrounding those cells

what substances can/cannot pass through the blood-brain barrier

• CO2 and O2 can enter and leave the BBB

• lipids, amino acids, and glucose can leave the BBB into the brain

what is the defensive procedure if a substance from the BBB enters the brain when it is not supposed to

astrocytes pick it up before it can make contact with any neurons

what is the composition of cerebrospinal fluid (CSF)

CSF is a watery solution made from blood plasma but with less proteins and different ion concentrations.

what are the functions of CSF (cerebrospinal fluid)

• nourishes brain and carries chemical signals

• protects CNS from physical trauma

• reduces brain weight so it is not crushed under its own weight

what is a choroid plexus

a cluster of capillaries that hang off the roof of ventricles and are enclosed by the pia mater that produce CSF

what is the CSF movement cycle through the brain

1. the choroid plexus in the lateral, third, and fourth ventricles produce CSF

2. CSF from the lateral ventricle flows through the interventricular foramina into the third ventricle

3. CSF from the third ventricle flows through the cerebral aqueduct into the fourth ventricle

4. CSF from the fourth ventricle flows through the lateral and median apertures into the subarachnoid space

5. CSF flows throughout the sub-arachnoid space

6. CSF is absorbed by the arachnoid villi/granulations into the dural venous sinuses

7. CSF travels through the venous blood to the heart and lungs

8. heart and lungs pumps CSF to choroid plexuses through arteries

what is the largest part of the brain, and the one that makes you human

cerebrum

what are the five lobes of the cerebrum, their functions, and which one is internal

• frontal: coordinates information, controls behaviors

• parietal: sensory information from skin, muscles, and organs

• occipital: vision

• temporal: hearing

• insular: (this one is internal) taste and smell

what are the dividing structures of the cerebrum, and what do they each separate

longitudinal fissure: left and right hemispheres

central sulcus: frontal and parietal lobes, motor cortex and somatosensory cortex

parieto-occipital sulcus: parietal and occipital lobes

lateral sulcus: frontal and temporal lobes

what is the composition of the cerebral cortex

gray matter composed of: neuron cell bodies, dendrites, glial cells, blood vessels, no axons

what are the functions of the cerebral cortex

• sensory perception

• voluntary motor initiation

• communication

• memory storage

• emotions

• awareness and understanding

how are the motor and somatosensory cortexes divided and what are their functions

they are divided by the central gyrus

• primary motor cortex: in the precentral gyrus, initiates voluntary movement

• primary somatosensory cortex: in the postcentral gyrus, sensory input arrives here and is interpreted in the various cerebral lobes

where is the location of the general sensory information of the body? what does this information include

postcentral gyrus, primary somatosensory cortex

• pain

• touch

• body position

what is the sensory homunculus and to what extent does its characteristics impact the sensory input

it is a “map” of the body on the postcentral gyrus, the larger the size of the body part, the more detailed the sensory information a person receives from it.

what initiates the contraction of the body’s skeletal muscles

precentral gyrus, primary motor cortex

what is the motor homunculus and to what extent does its characteristics impact the locomotion of the body

it is a “map” of the body on the precentral gyrus, the larger the size of the body part, the more detailed the motor instructions a person receives from it.

where are Wernicke’s and Broca’s areas located

left hemisphere, cerebral cortex

what is the function of broca’s area

turning thoughts into speech

what is the function of wernicke’s area

interpreting speech

what are the six different functions of the left and right brain respectively

right brain:

• spatial patterns

• mental images

• intuition

• art/music

• creativity

• humor

Left brain:

• reasoning

• logic

• analysis

• STEM

• language

• teamwork

what are the three types of white matter tracts in the cerebrum, provide examples of each

• association tracts: connect areas in the same cerebral hemisphere

  • idk

• commissural tracts: connect areas in opposite hemispheres

  • corpus callosum

• projection tracts: send information out of the brain

  • corona radiata

what is the basal nuclei, and what is their function

they are groups of gray matter within the white matter of the cerebrum. their function is to filter incorrect responses and suppress unwanted movements

what are some disorders involving the basal nuclei, and what are their symptoms

• Parkinson’s disease: tremors

• Tourette’s syndrome: tics

what is the largest structure of the diencephalon

thalamus

what are the functions of the thalamus, in the diencephalon

relay center

• relay sensory info from spinal cord and brainstem

• relay motor info from cerebellum and basal nuclei

filters information as well

what is the major functional organ of the epithalamus, and what is its function

pineal gland: it makes melatonin which induces sleep and regulates circadian rhythm

what is the function of the hypothalamus

maintaining homeostasis, linking nervous and endocrine systems

• growth, metabolism

• stress

• circadian rhythm

• nutrient, water balance

• temperature

what are the 5 main structures of the limbic system, and their functions

• hippocampus: stores memories

• mamillary bodies: make memories accessible

• olfactory bulbs: trigger emotional responses to smells

• amygdala: regular fear and rage

• cingulate gyrus: use of gestures to express emotions

what is the function and the main structures of the brainstem

regulating involuntary vital functions

• midbrain

• pons

• medulla oblongata

what are the structures of the midbrain and their functions

• superior colliculi: assist with vision, they track moving objects and scan stationary targets

• inferior colliculi: assist with hearing, communicate with the cerebellum for the startle reflex

what are the structures of the pons and their functions, as well as the overall function of the pons

• pons (overall): bridge between cerebrum and lower and lower nervous system structures, relays motor information

• pontine respiratory center: regulate breathing length and depth

• pontine micturition center: control urination

what are the functions of the medulla oblongata

• breathing rate

• swallowing, coughing, sneezing, vomiting reflexes

• heart rate, stroke volume, blood pressure

what is the reticular formation

a group of neurons throughout the brainstem that control consciousness

what is the reticular activating system

a subset of the reticular formation that:

• sends signals to the cerebral cortex to keep it alert

• activated by sensory input

• deactivated while sleeping

what are the two types of sleep and what are the characteristics of each

Non-REM sleep

• heart rate, blood pressure, breathing rate decline

• muscle tone and temperature decline

• minimal dreaming

REM sleep

• heart rate, blood pressure, breathing rate increase

• muscle contraction inhibited

• vivid dreaming

what is the cycle of sleep

1. NREM stage 1

2. NREM stage 2

3. NREM stage 3

4. NREM stage 4

5. NREM stage 3

6. NREM stage 2

7. NREM stage 1

8. REM sleep

9. repeat

10. repeat, omit NREM stage 4

11. repeat, omit NREM stage 4 and 3

12. repeat

what are the functions of the cerebellum

• assist with posture, balance, and skeletal muscle movements

• stores motor patterns (muscle memory)

• evaluated motor movements as they occur

what are the structures of the cerebellum and their functions

• inferior peduncle: brings sensory info from medulla and spinal cord

• middle peduncle: brings info from pons, plans of desires movement

• superior peduncle: sends edited motor plans to the primary motor cortex

what is the function of the spinal cord

two way communication between the brain and the rest of the body

what are the structures of the spinal cord and their adjacent structures, beginning at the base of the skull

• medulla leaves foramen magnum of the skull

• ends at L2 at conus medullaris

• pia mater continues beyond, forming filum terminale

• spinal nerve branch to form cauda equina

what are the two enlarged areas of the spinal cord that contain more neurons

cervical and lumbar

what diagnostic/therapeutic procedures are made possible due to the extra layer of dura mater in the brain

• epidural anesthesia injection in epidural space filled with adipose tissue

• spinal tap/lumbar puncture to extract CSF from subarachnoid space

what are the four main neurons in the gray matter of the spinal cord, and what do they pertain to (each one and overall)

they control reflexes

• somatic sensory neuron: get sensory info from skin, muscles, connective tissue (dorsal)

• visceral sensory neuron: get sensory info from organs (dorsal)

• visceral motor neuron: carry motor info to smooth muscle, cardiac muscle, glands (ventral)

• somatic motor neuron: carry motor info to skeletal muscles (ventral)

Motor info travels ___ the spinal cord, sensory info travels ____ the spinal cord

motor travels down, sensory travels up

what are the results of aging in the CNS

• loss of neurons

• speed of neurotransmission declines

• ability to process information declines

• speed of muscle movements declines

• speed of reflexes decline

• enlargement of ventricles