Chapter 3

Question 1

What must happen to propagate an action potential?

Answer 1

membrane potential must exceed threshold of excitation

Question 2

What are the three main parts of the neuron?

Answer 2

1. cell body, soma
2. dendrites
3. axon

Question 3

Where are cell bodies of most neurons located?

Answer 3

brain or spinal cord to stay protected, some are in the ganglia of the PNS

Question 4

What do dendrites do?

Answer 4

transmit impulses toward the cell body

-some impulses are received directly by the cell body or axon hillock

Question 5

What do axons do?

Answer 5

transmit impulses away from the cell body (axon hillock-origin of action potentials)

Question 6

Long axons are termed _____ _____.

Answer 6

nerve fibers

Question 7

The end of the axon branches into many _____ _____.

Answer 7

terminal ends

Question 8

Each terminal end has a ____ _____.

Answer 8

synaptic knob

Question 9

What do synaptic knobs contain?

Answer 9

vesicles that contain chemical neurotransmitters

Question 10

What is myelin sheath?

Answer 10

made of lipids, wrap around axons, increases conduction

Question 11

In PNS, myelin sheath is composed of _____ _____.

Answer 11

Schwann cells

Question 12

T/F

Myelin is continuous.

Answer 12

False

Question 13

Nodes of Ranvier?

Answer 13

myelin sheath gaps, voltage gated Na+ channels are concentrated here

Question 14

Saltatory conduction?

Answer 14

myelinated axons propagate impulses faster because it jumps from one node of ranvier to another

Question 15

3 functions of myelin sheath?

Answer 15

1. protect axon
2. insulate axon from other neurons
3. increase rate of conduction of impulse

Question 16

Myelinated neurons transmit impulses _____ than unmyelinated.

Answer 16

faster

Question 17

Small neurons transmit impulses _______ than larger ones.

Answer 17

slower

-larger= less resistance

Question 18

What does the size of the neuron refer to?

Answer 18

diameter or cross sectional area of axon

Question 19

What is conduction of a nerve impulse along the axon called?

Answer 19

propagation of an action potential

Question 20

Depolarization?

Answer 20

membrane potential becomes less negative

Question 21

Repolarization?

Answer 21

establishes the normal resting membrane potential

Question 22

Neurons that innervate skeletal muscle form _______ junctions.

Answer 22

neuromuscular

Question 23

Neurons that innervate smooth muscle cardiac muscle form ______ junctions.

Answer 23

neuroeffector

Question 24

How many kinds of neurotransmitters can one neuron release?

Answer 24

one

Question 25

What is the space between the pre and post synaptic membrane?

Answer 25

synaptic cleft

Question 26

In neuron to neuron synapses in the sympathetic chain ganglia or collateral ganglia, _____ of the synapses are excitatory.

Answer 26

all

Question 27

All or none principle?

Answer 27

if the threshold of excitation is exceeded, an action potential will occur

• neuron will either transmit or not, no in between
• strength cannot be graded

Question 28

How can graded potentials (EPSP) result in an action potential? (two ways)

Answer 28

1. Spatial summation- summing effects of several simultaneous EPSP graded potentials by more than one neuron
2. Temporal summation- summing effects of high frequency of EPSPs graded potentials from a single neuron
   - usually combined with both of the above

Question 29

How can you determine the strength of the stimulus?

Answer 29

by the frequency of action potentials

Question 30

Tract vs Nerve?

Answer 30

tract- CNS bundle of axons and dendrites

nerve- PNS

Question 31

Sensory neurons enter the spinal cord through the _____ roots.

Answer 31

dorsal

Question 32

T/F

Sensory neurons are typically unipolar.

Answer 32

True

Question 33

Upper motor neurons?

Answer 33

cross to the opposite side of the spinal cord and synapse with cell bodies of lower motor neurons

Question 34

Lower motor neurons?

Answer 34

axons exit the spinal cord and innervate effector organs (autonomic) or skeletal muscle (somatic)

Question 35

Motor neurons exit the spinal cord through the ___ root.

Answer 35

ventral

Question 36

Upper and lower motor neurons are mulitpolar or unipolar?

Answer 36

multipolar- more than two processes extending out

Question 37

Spinal nerves are bundles of what?

Answer 37

sensory and motor neurons