Nervous

Question 1

When do Action Potentials occur?

Answer 1

only when membrane potential at axon hillock reaches threshold

Question 2

Explain the 3 phases of Action potentials

Answer 2

1. Depolarization (Na+ channels open first)
2. Repolarization (K+ channels open more slowly)
3. Hyperpolarization (Na+ channels close; K+ channels close slowly)

Question 3

What is Absolute Refractory Period?

Answer 3

cell incapable of generating a new AP

Question 4

What is Relative Refractory Period? How is it caused in APs?

Answer 4

more difficult to generate new AP

caused by open K+ channels

Question 5

What is Myelin? What’s its function?

Answer 5

insulating layer of lipid-rich Schwann cells wrapped around axon
reduce “leakage” of charge across membrane

Question 6

What are Schwann Cells?

Answer 6

a type of Glial cell (Cells other than neurons that support neuron function)

Question 7

What are Nodes of Ranvier?

Answer 7

areas of exposed axonal membrane between Schwann cells

Question 8

What are Internodes?

Answer 8

the myelinated region of axon

Question 9

Describe Saltatory conduction

Answer 9

Rapid conduction
APs leap from node to node
APs occur at nodes of Ranvier, and electrotonic current spread through internodes

Question 10

How do Action Potentials go in one direction?

Answer 10

APs start at axon hillock and travel towards axon terminal
Up-stream Na+ channels are in the absolute refractory period which prevents backward (retrograde) transmission and summation of APs
Relative refractory period also contributes by requiring a very strong stimulus to cause another AP

Question 11

What does Action Potential Frequency carry? How does it increase? How does magnitude respond?

Answer 11

AP frequency carries information
AP frequency increases w/ stronger stimuli
Magnitude of each AP does not change

Question 12

What is Maximum frequency limited by?

Answer 12

by the absolute refractory period

Question 13

What is a Synapse?

Answer 13

a specialized site of contact of a neuron w/ another neuron or w/ an effector

Question 14

What is a Synaptic Cleft?

Answer 14

20-30nm space that typically separates neurons at a synapse

Question 15

Presynaptic ____ cell

Answer 15

transmits

Question 16

Postsynaptic ____ cell

Answer 16

receives

Question 17

How are spinal nerves arranged and numbered?

Answer 17

sequentially arranged and numbered according to region of the vertebral column (Cervical (C-1), Thoracic (T-1), Lumbar (L-1), Sacral (S-1))

Question 18

Afferent fibers enter spinal cord via the ….?

Answer 18

dorsal root

Question 19

Efferent fibers leave via the ….?

Answer 19

ventral root

Question 20

What is Gray matter?

Answer 20

contains neuronal cell bodies

Question 21

What is a Ganglion?

Answer 21

a mass of nerve cell bodies

Question 22

What is the Autonomic Nervous System part of and involved in?

Answer 22

Part of Peripheral Nervous System (PNS)
Involved in homeostatic regulation of most physiological functions (ex heart rate, blood pressure, breathing)
[Not under voluntary control]

Question 23

Describe the 3 components of the Autonomic Nervous System

Answer 23

1. Sympathetic (active during stress or physical activity)
2. Parasympathetic (resting and digesting – opposes sympathetic)
3. Enteric (only digestion – separate from other 2)

Question 24

Compare the components of the Sympathetic and Parasympathetic ANS

Answer 24

Sympathetic: preganglionic neuron short; Neurotransmitter of preganglionic neuron is ACh; Neurotransmitter of postganglionic neuron is NE or E
Parasympathetic: preganglionic neuron is long; Neurotransmitter of preganglionic neuron is ACh; Neurotransmitter of postganglionic neuron is ACh

Question 25

Describe the Visceral reflex

Answer 25

4 neurons involved neurons leaving ventral root are preganglionic and can synapse w/ sympathetic ganglion, collateral ganglion, or at the visceral organ

Question 26

Describe Somatic motor pathways

Answer 26

2-3 neurons in circuit Only a single neuron in the efferent motor outflow (to effector via spinal nerve) Skeletal muscle only Utilizes Acetylcholine

Question 27

Describe the pathway of Acetylcholine and motor neurons

Answer 27

1. acetyl CoA synthesized in mitochondria 2. Choline acetyl transferase catalyzes the conversion of choline and acetyl CoA to ACh 3. The ACh is packaged into synaptic vesicles 4. ACh is released into the synapse 5. ACh binds to its receptor on postsynaptic cell 6. AChE breaks down ACh into choline and acetate, terminating signal in postsynaptic cell 7. Presynaptic cell takes up and recycles choline; acetate diffuses out of the synapse

Question 28

Where are Nicotinic ACh receptors found? What do they cause?

Answer 28

on skeletal muscle cells binds to nicotine; ligand-gated ion channels open; Na+ rapidly enters muscle cell causing excitatory postsynaptic potential

Question 29

Describe Myasthenia gravis

Answer 29

decreased # of ACh receptors on the muscle membrane | characterized by fatigue that increases throughout the day

Question 30

The number of spinal nerves varies with ...

Answer 30

the number of segments in the trunk or tail

Question 31

What is White Matter?

Answer 31

surrounds gray matter and is composed of nerve fibers linking levels of the spinal cord and between SC and brain [often myelinated, giving white appearance]

Question 32

What is a CPG?

Answer 32

Central Pattern Generator Rhythmic activity arising from the spinal cord that has no feedback Neural network System must repeatedly return to starting condition

Question 33

What are some examples of CPGs?

Answer 33

Swallowing, walking, hiccups, other rhythmic behaviors

Question 34

What is Autotomy?

Answer 34

the act whereby an animal severs one or more of its own appendages ex. rats (tail skin), geckos, lizards

Question 35

Describe what happens during tail autotomy in lizards

Answer 35

muscular contractions break vertebrae at autotomy plane | tail regenerates following autotomy

Question 36

Describe the motor patterns during the autotomy in lizards. What two theories may be the cause of these complex motor patterns?

Answer 36

Rhythmic swings and Complex flips and jumps. 1. Sensory feedback from the environment [probably not since experiments on a clear arena] 2. Multiple central pattern generators [more likely]

Question 37

Why is it crucial for brain development in birds to have one eye exposed to light?

Answer 37

so brain's 2 hemispheres can properly integrate information