BIOL 208 Exam 2

Name and describe the 3 basic functions of the nervous system

1. Sensory function: translate sensory information (touch, hearing, vision, blood pressure)

2. Integration: use brain to translate signals

3. Motor function: move skeletal muscle

What does the central nervous system consist of and explain its 3 functions

consists of the brain and spinal cord

functions: integration and processes nervous information
1. sensory data: from inside the body

2. motor commands: control activities of peripheral organs

3. higher learning functions of brain: intelligence, memory, learning, emotion

What does the peripheral nervous system consist of and explain its function

consists of nerves/ganglia (12 pairs of cranial nerves, 31 pairs of mixed spinal nerves, and nerve plexuses; can be sensory, motor, or mixed)
function: send information to and recieve information from the CNS (and some reflexes)

What are the two functional divisions of the PNS?

Afferent/sensory: signals move toward the CNS (Arrives at CNS)
Efferent/motor: signals move away from the CNS (Exits the CNS)
SAME

What are receptors and effectors and which division are they found?

Found in afferent division
Receptors: detect changes/respond to stimuli (often proteins that can change shape); ex. neurons/specialized cells and complex sensory organs
Effectors: respond to efferent signals; ex. cells and organs

What are the two kinds of cells in neural tissue?

1. Neurons: cells that send and receive signals; basic functional units of the NS

2. Neuroglia (glial cells): cells that support and protect neurons

What are the 8 components to a neuron’s structure?

1. large nucleus and nucleolus: to make ribosomes

2. lots of proteins for neurotransmitters (chemical messengers)

3. Mitochondria: generate ATP

4. RER and ribosomes: to make proteins

5. Cytoskeleton: microtubules for neuronal communication

6. Nissl bodies:dense areas of RER and free ribosomes

7. Dendrites: receive information; highly branched; 80-90% of neuron surface area

8. Axon Hillock: signal integration (translates signals based on changes in ions); where action potential begins

What is a synapse?

the site of communication between two neurons or between a neuron and another effector

What are the three parts of a synapse?

1. Presynaptic cell: neuron that sends the message; releases chemical messenger (typically ACh) or communicates via ions

2. Postsynaptic cell: cell that receives the message; ex. neurons, muscles, glands

3. Synaptic Cleft: the small gap that separates the presynaptic membrane and the postsynaptic membrane
   

What are the three structural classifications of neurons and give examples for where they’re located

1. Unipolar Neurons: detect touch, pressure, temperature (sensory neurons); ex. skin

2. bipolar neurons: relay information for olfactory epithelium of nose and retina of eye (smell/sight); the more of these neurons you have, the stronger your senses

3. multipolar neurons: interneurons in the CNS (help to translate information); ex. all skeletal muscle motor neurons

What are sensory neurons and provide 4 examples

monitor internal environment and effects of external environment

1. pacinian corpuscle: sensitive to vibration and pressure; unipolar

2. meissner corpuscle: sensitive to light touch in skin; located near surface of skin; unipolar

3. nociceptor: pain perception; bipolar

4. merkel cells: sensitive to light touch; found in superficial skin layers; bipolar

What are interneurons?

Involved in higher functions (memory, learning, planning); located in the CNS between sensory and motor neurons

What are the 4 types of neuroglia in the CNS

1. Ependymal Cells: secrete CSF; stem cells

2. Astrocytes: forms blood brain barrier; replace damaged neural tissue; guide neuron development in the fetal brain

3. Oligodendrocytes: form myelin sheath in CNS

4. Microglia: defend against pathogens

Ependymal Cells

1. a type of neuroglia in the CNS

2. line central canal of spinal cord/ventricles of the brain

3. secrete CSF

4. have cilia/microvilli that circulate CSF

5. monitor CSF

6. contains stem cells for repair

Astrocytes

1. a type of neuroglia in the CNS

2. help form blood brain barrier (protects the brain)

3. replace damaged neural tissue (leaves scar tissue which can break connections between neurons - can cause paralysis)

4. guide neuron development in the fetal brain

5. exercise stimulates astrocytes which can help with neurorehabilitation; increases neuroplasty (creates new communication pathways)

Oligodendrocytes

1. a type of neuroglia in the CNS

2. wrap around axons to form myelin sheaths (forms white matter deep to the cerebral cortex)

Microglia

1. a type of neuroglia in the CNS

2. migrate through neural tissue

3. clean up cellular debris/waste products

4. defend against pathogens (works with astrocytes)

What are the two types of neuroglia in the PNS?

1. satellite cells: regulate environment around neuron

2. schwann cells: form myelin sheaths in PNS

Satellite cells

1. surround ganglia

2. regulate environment around neuron (O2, CO2, neurotransmitter levels, nutrients)

Schwann cells

1. form myelin sheaths (neurilemma) around peripheral axons

What are neuroglia? How many are found in the CNS and how many are found in the PNS?

supportive cells

4 found in the CNS; 2 found in the PNS

What is myelination and why is it important (5 reasons)?

a cover around the neuron (specifically the axon)

1. increases speed of action potentials going down axon

2. important for muscle contraction (swallowing/inhalation uses skeleton muscle which needs myelinated neurons - without it can cause respiratory failure)

3. myelin insulates myelinated axons

4. makes nerves appear white

5. prevents ion leakage

What is the difference between white matter/gray matter in terms of myelination?

white matter: regions of CNS with myelinated nerves

gray matter: unmyelinated areas of CNS

What is amyotrophic lateral sclerosis?

ALS: motor neurons degenerate and die; ultimately leads to respiratory failure (can no longer breathe anymore)

What is adrenoleukodystrophy?

ALD: leads to death due to respiratory failure; an X-linked recessive disorder; the depletion of the protein that breaks down long fatty acid chains (VLCFA); destruction of myelin sheath

What are neurotransmitters (5)?

1. chemical messengers

2. released at presynaptic membran/neuron by exocytosis (in vesicles)

3. affect receptors of postsynaptic membrane

4. broken down by enzymes (can cause twitching if not broken down)

5. are reassembled at synaptic knob/axon terminal

What are the two types of synapses?

1. electrical synapse: transmits signals directly from neuron to neuron (gap junctions)

2. chemical synapse: uses neurotransmitters

Electrical synapse

1. fast, direct contact

2. bi-directional (movement of ions through gap junctions)

3. excitatory (always get communication/action potential)

Chemical synapse

1. slower than electrical

2. unidirectional (presynaptic to postsynaptic)

3. can be excitatory or inhibitory depending on the receptor

What are the 3 types of potentials (charge)?

1. resting potential

2. graded potential

3. action potential

What is an example of stimulation and inhibition, and what is it dependent on?

stimulation: ACh released during muscle contraction is stimulatory

inhibition: ACh which is released into heart by Vagus CN X is inhibitory (heart rate is slowed)

response is dependent on receptors (different receptors, different outcomes)

What are the 4 segments of a neuron (potentials)?

1. Receptive segment (cell body): production of graded potentials

2. Initial segment (axon hillock): summation of graded potentials; initiation of action potential

3. conductive segment (axon): propagation of action potential; where the AP travels

4. Transmissive segment (axon terminal): action potential causes release of neurotransmitter

Why are neurons electrically excitable?

due to the voltage difference across their membrane, which causes them to communicate through electrical signals

What are the two types of electrical signals neurons use to communicate?

1. action potentials: travel long distances along the axon

2. graded potentials: temporary changes in charge

How does the flow of ions affect neuron function?

in living cells, ions flow through ion channels in the cell membrane, creating electrical charge differences that enable neuron communication

Where are ion channels found, and why are they important?

ion channels are present in all cell membranes but are especially important in the nervous system, as they help regulate electrical signals

How is charge measured in the body?

measured by amount of ions, which determines the charge within cells

What are the 6 reasons why resting potential (membrane potential) exists?

1. concentration of ions different inside vs outside

2. extracellular/interstitial fluid rich in Na+ and Cl-

3. cytosol full of K+, organic phosphate, protein (P-); the P- are stuck inside the cell and are negatively charged - the inside of the cell is negatively charged

4. most Na+ is outside the cells

5. membrane permeability differs for Na+ and K+ (50-100 greater permeability for K+)

6. Na+, K+, ATPase is active (leak channels work to keep at resting potential; -70mV)

Where are the location of ions at resting potential, and what channels are at work?

Inside cell: K+, phosphate, proteins (P-)

Oustide cell: Na+, Cl-

Channels: Na+, K+, ATPase (moves 3Na+ out and 2K+ in), Na+ leak channel (lets some Na+ in), K+ leak channel (lets some K+ out)

What are graded potentials and where do they occur?

deviations from the resting membrane potential (-70mV); occur most often in the dendrite and cell body of a neuron

What are the two types of graded potentials?

1. Hyperpolarized: more negative

2. Depolarized: more positive

What is hyperpolarization in graded potentials?

membrane potential becomes more negative than the resting potential (bring in Cl-/increase permeability to Cl- or let out K+/increase permeability to K+); does not lead to action potentials (inhibit/slow things down)

What is depolarization in graded potentials?

membrane potential becomes more positive than the resting potential (bring in Na+/increase permeability to Na+ or don’t let out K+/decrease permeability to K/close leak channel); can lead to action potential (if change is strong enough)

What channels do graded potentials use, and what channels do action potentials use?

graded potentials: can happen due to any type of channel

action potentials: can only use voltage gated type channels (VG channels)

What are the 4 types of channels?

1. Leak channels: are open and allow ions to leak-down gradient

2. Voltage gated channels: need charge/certain voltage to open (makes action potential)

3. Ligand/chemical gated channels: need a certain type of chemical to open

4. mechanically gated: physical distortion will open/close these)

What happens during an action potential?

Voltage-gated Na+ and K+ channels open in sequence to propagate the electrical signal

What is the all-or-none principle?

if a stimulus reaches threshold, the action potential is always the same. the threshold is reached at the axon hillock

What are the three phases of an action potential and what channels are at work?

1. Depolarization: voltage gated Na+ channels open and lots of Na+ rushes in

2. Repolarization: voltage gated K+ channels open so K+ rushes out (Na+ channels also close)

3. Hyperpolarization: voltage gated K+ channels close slowly (makes membrane potential more negative than resting)

   (all utilize VG channels)

What must happen for an action potential to occur?

a graded potential must be strong enough to reach threshold which triggers the opening of VG Na+ channels

Which channels work to bring the membrane potential back to resting?

Na+, K+, ATPase, Na+ leak, K+ leak (no VG gated channels)

Why is rapid inactivation of VG Na+ channels crucial during action potential?

important for the normal electrical activity of excitable cells; defects of activation of VG Na+ channels can lead to muscle paralysis, ventricular fibrillation, epilepsy

What are the two methods of propagating/moving action potentials?

1. continuous conduction: unmyelinated axons; slower

2. saltatory conduction: myelinated axons; very fast (jump from the nodes of ranvier

Why does an action potential only travel in one direction (unidirectional conduction)?

due to the transient inactivation of VG Na+ channels, preventing the action potential from traveling backwards

Why must voltage-gated Na+ channels be close together in unmyelinated neurons

in unmyelinated neurons, voltage-gated Na+ channels must be close together to ensure continuous conduction of the action potential.

Where are voltage-gated Na+ channels located in myelinated neurons, and why?

located at the Nodes of Ranvier to allow for saltatory conduction, preventing ion loss due to the insulation provided by myelin.

What is the brain, and where is it located?

a soft, whitish-gray organ that is anatomically continuous with the spinal cord and resides in the cranial cavity. it directly/indirectly controls most of the body’s functions

What is the brain primarily made of?

mostly nervous tissue, but it also contains epithelial and connective tissues

What are ventricles in the brain?

internal cavities within the brain that are filled with cerebrospinal fluid (CSF)

How much blood flow does the brain receive at rest, and why?

about 20% of total blood flow because of its high demand for oxygen, glucose, and nutrients

what is the spinal cord, and where is it located?

a long, tubular organ enclosed within the vertebral cavity. blends with the inferior portion of the brainstem and ends between the first and second lumbar vertebrae

central canal (of spinal cord)

an internal cavity within the spinal cord, continuous with the brain’s ventricles, and filled with CSF

What are the 4 divisions of the brain and how are they distinct?

1. Cerebrum

2. Diencephalon

3. Cerebellum

4. Brainstem

They’re distinct in the type of input it receives and where it sends its output

What are the folds and depressions of the cerebrum called?

Folds: gyri

Depressions between the folds: Sulci

What are the 5 swellings of the brain visible at 5 weeks of development

1. Prosencephalon → divides into telencephalon (cerebrum) and diencephalon (epithalamus, thalamus, hypothalamus)

2. Mesencephalon → remains unchanged (midbrain)

3. Rhombencephalon → divides into metencephalon (pons/cerebellum) and myelencephalon (medulla oblongata)

Which primary brain vesicle remains unchanged during development?

mesencephalon (midbrain)

Can the brain feel pain when cut?

No

What are the 4 things the brain is protected by?

1. Cranial bones: held together by sutures

2. Cranial meninges: pia, arachnoid, dura

3. Cerebrospinal fluid (CSF): absorbs shock

4. Blood brain barrier: has lots of tight junctions

What is the structural arrangement of the cranial meninges from superficial to deep (9)?

1. skin

2. periosteum

3. bone

4. epidural space

5. dura mater

6. subdural space

7. arachnoid mater

8. subarachnoid space

9. pia mater

What are the cranial meninges?

three connective tissue layers that support and protect the brain (dura, arachnoid, pia mater)

What are the 3 functions of the cranial meninges?

1. separate and support soft brain tissue

2. enclose and protect blood vessels supplying the brain

3. help contain and circulate CSF

Where does cerebrospinal fluid flow in relation to the meninges?

flows under the arachnoid mater in the subarachnoid space

What is the cranial dura septa, and what is its function?

a double-layered dura formed by the meningeal layer extending into the cranial cavity at four locations. it partitions the brain and provides support

What are the four cranial dura septa, and what do they separate

1. falx cerebri: separates left/right cerebral hemispheres

2. tentorium cerebelli: horizontal fold that separates cerebrum from cerebellum

3. falx cerebelli: separates left/right cerebellar hemispheres

4. diaphragma sellae: small septum between pituitary gland and hypothalamus

Where and how do dural venous sinuses form?

in locations where the two layers of the dura mater separate, creating spaces for venous blood drainage

What are the 4 major dural venous sinuses?

1. superior sagittal sinus

2. inferior sagittal sinus

3. transverse sinus

4. occipital sinus

What are venticles?

cavities within the brain that contain cerebrospinal fluid

What are the 4 ventricles in the brain and where are they located?

1. two lateral ventricles

2. third ventricle in diencephalon: communicates with fourth ventricle through the cerebral aqueduct

3. fourth ventricle between pons and cerebellum: merges with central canal of spinal cord

What is cerebrospinal fluid?

a liquid that protects the brain and spinal cord against chemical and physical injuries; also carries oxygen and glucose from the blood to nervous tissue cells

What makes CSF, and where is it typically contained?

choroid plexus makes CSF; contained in the ventricles of the brain (must be at a constant volume)

What is the function of the blood brain barrier (BBB)?

protects brain cels by acting as a selective barrier, preventing many substances and pathogens from entering the brain from the blood (substances must be hydrophobic to enter the brain)

How does the blood brain barrier affect drug delivery?

prevents the entry of therapeutic drugs

What happens if the blood brain barrier is damaged?

brain injuries can break down the BBB, allowing normally restricted substances to enter the brain tissue (may be harmful)

How does blood flow to and from the brain?

blood flows to the brain via the vertebral and carotid arteries and returns to the heart via the jugular veins

How much of the body’s oxygen supply does the brain use?

about 20%

What can happen if oxygen supply to the brain is interrupted?

can cause weakening, permanent damage, or death of brain cells

What are the effects of glucose deficiency in the brain?

mental confusion, dizziness, convulsions, and unconsciousness (symptoms of hypoglycemia)

What is the brain stem composed of?

midbrain, pons, medulla oblongata

What are the functions for each part of the brainstem?

Midbrain: regulate auditory (hearing) and visual (sight) reflexes

Pons: taste, swallowing, control of respiration

Medulla oblongata: heart rate, respiratory rate, swallowing, coughing, vomiting, sneezing, hiccupping

What are the functions of the cerebellum?

coordination of skeletal muscle contractions and maintenance of normal muscle tone, posture, and balance

What is the diencephalon composed of?

1. thalamus

2. hypothalamus

3. epithalamus

What are the functions for each part of the diencephalon?

1. thalamus: translates data (relay center)

2. hypothalamus (master gland): regulates homeostasis (especially temperature)

3. epithalamus: contains pineal gland which secretes melatonin; emotional responses to odor

What 5 sections is the cerebrum divided into?

1. frontal lobe

2. parietal lobe

3. temporal lobe

4. occipital lobe

5. insula

What are the functions for each section of the cerebrum?

1. frontal lobe: parts of speech, emotions, problem solving

2. parietal lobe: perception of stimuli

3. temporal lobe: memory, speech

4. occipital lobe: visual processing

5. insula: empathy and taste

Where is the limbic system located (emotional system)?

lies on both sides of the thalamus, just under the cerebrum

What structures are included in the limbic system (emotional system)?

hypothalamus, hippocampus, amygdala

What functions is the limbic system (emotional system) involved in?

memory, learning, emotion, behavior

What is the function of the hippocampus, and where is it located?

located in the temporal lobe; important for converting short-term memory into long-term memory

What happens if the hippocampus is damaged?

cannot form new memories (50 first dates)

What is the amygdala, and where is it located?

consists of two almond-shaped masses of neurons near the lower end of the hippocampus, on either side of the thalamus

What is the primary function of the amygdala?

involved in emotion processing (especially fear which is learned), helps sort/code memories based on emotional perception