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EXSC 463 Exam 1 > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

Somatic motor neurons are also called ______.

A

alpha motor neurons

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2
Q

Vesicles in the terminal knobs of somatic motor neurons release what neurotransmitter?

A

Acetylcholine (ACh) which causes excitation of skeletal muscle fiber

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3
Q

What is the motor end plate?

A

highly excitable region of the sarcolemma where the terminal end of a somatic motor neuron synapses with the skeletal muscle cell

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4
Q

How many neuromuscular junctions does one skeletal muscle cell have?

A

one, it is innervated by one terminal end of one somatic motor neuron

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5
Q

Sarcolemma?

A

cell membrane of a skeletal muscle cell, also called a fiber

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6
Q

Motor unit?

A

a single somatic motor neuron and all the skeletal muscle fibers that it innervates

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7
Q

T/F

Motor units exist in skeletal, smooth, and cardiac muscle.

A

False

only skeletal

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8
Q

What does the size of the motor unit refer to?

A

the number of muscle fibers that it innervates

-small units are found in muscles that need fine motor control

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9
Q

Why are muscle fibers in a motor unit dispersed throughout the muscle?

A

allows a more effective angle of pull on the skeleton

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10
Q

Can a single twitch be graded?

A

no

all or none

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11
Q

Size principle?

A

because small motor neurons have lower thresholds of excitation, they will be recruited before large neurons

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12
Q

T/F

All of the fibers in a motor unit are of the same skeletal muscle fiber type (I, IIa, IIx).

A

True

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13
Q

How can you increase the force of contraction of a single motor unit?

A

increasing the frequency of stimulation

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14
Q

High frequencies of stimulation result in ______.

A

tetanic contractions

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15
Q

The force of a single twitch is about ______ of the force of a tetanic contraction.

A

25%

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16
Q

Somatic motor neurons release _____, which is always ____.

A

ACh

excitatory

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17
Q

How many motor neurons have an inhibitory effect?

A

none

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18
Q

How do you decrease the force of contraction?

A

reducing the number of activated motor units

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19
Q

How does inhibition work in a reflex response?

A

cell bodies of some somatic motor neurons are inhibited by an interneuron, it releases a neurotransmitter (GABA in CNS) which causes hyperpolarization (membrane potential goes further away from resting potential)

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20
Q

Proprioception?

A

perception of movement of the body and its orientation in space

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21
Q

Where are muscle spindles located?

A

imbedded in the belly of the muscle and run parallel to extrafusal muscle fibers

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22
Q

What do muscle spindles do?

A

detect the amount and rate of stretch of muscle fibers

-they are more numerous in muscles that require fine motor control

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23
Q

What are muscle spindles composed of?

A

intrafusal fibers and annulospiral and flower spray sensory neurons

24
Q

Intrafusal fibers function?

A
  • stretch when muscle is stretched
  • have actin and myosin on the ends so they have contractile properties
  • central portion is non contractile
25
Q

Two types of intrafusal fibers?

A

nuclear bag fibers, nuclear chain fibers

26
Q

Annulospiral fibers function?

A

wrap around the center of both types of intrafusal fibers and detect the rate of change of length of the fiber

27
Q

Flower spray sensory neurons function?

A

wrap around only the nuclear chain fibers and provide info about relative muscle length, higher threshold of excitation than annulospiral

28
Q

What 3 motor responses are initiated by the activation of the muscle spindle?

A
  1. depolarization of the somatic motor neuron that innervates the agonist muscle group, causing the muscle to contract and oppose the force causing muscle stretch
  2. Inhibition of the somatic motor neuron that innervates the antagonist muscle group, prevents opposition and stretch
  3. depolarization of a gamma motor neuron which innervates the contractile ends of the intrafusal fibers, causing contraction, allowing spindle to keep proportionately same length as agonist muscle
29
Q

How does the knee jerk reflex work?

A

doctor taps patellar tendon causing a small rapid stretch of muscle spindles

30
Q

Myotatic reflex?

A

muscle stretch reflex

31
Q

reciprocal inhibition?

A

reflexive contraction of the agonist muscle and relaxation of the antagonist muscle in response to stretch of agonish

32
Q

What happens when you hold a stretch for 30 seconds?

A

muscle spindle adapts to its new length and reduces firing rate

33
Q

Function of Golgi Tendon Organ?

A
  • transmits info about muscle tension to CNS
  • reflexive inhibition of the agonist muscles, which protects muscles, ligaments, tendons, joints
  • doesnt let muscle tendons stretch too far to cause injury
34
Q

What are two unique characteristics of autonomic neural pathways?

A
  1. Ganglia serve as distribution centers for neural impulses

2. Include two motor neurons in series (pre and post)

35
Q

Where are cell bodies of pre ganglionic motor neurons located?

A

ventral horns of gray matter of spinal cord

36
Q

Where are cell bodies of post ganglionic motor neurons located?

A

ganglia

37
Q

In sympathetic and parasympathetic motor neurons, the pre ganglionic neurons release _____, which is always _____.

A

ACh

excitatory to the postganglionic neurons

38
Q

Pre ganglionic motor neurons are ____, post ganglionic are _____. (myelinate?)

A

myelinated

unmyelinated

39
Q

Post ganglionic sympathetic neurons release _____ to smooth muscle, heart, glands.

A

NE

40
Q

Neurons that release NE are ______.

A

adrenergic

41
Q

Post ganglionic sympathetic neurons release _____ to sweat glands, bloods vessels of skin and sk mm.

A

ACh

42
Q

Neurons that release ACh are ______.

A

cholinergic

43
Q

Pre ganglionic sympathetic neuron releases ____ at the adrenal gland which stimulates the adrenal medulla to release ______.

A

ACh

Catecholamines

44
Q

Catecholamines? 80%?

A

NE and Epi

80% Epi

45
Q

Pre ganglionic paraympathetic neurons are _____ than pre ganglionic sympathetic neurons.

A

longer

46
Q

Post ganglionic parasympathetic neurons release ____ at smooth muscle, heart, glands.

A

ACh

47
Q

How can a single post ganglionic neuron affect a large area of the effector organ if there are no motor units?

A

varicosities are filled with neurotransmitter, when released they diffuse across interstitial fluid to receptors at the neuroeffector junction

48
Q

How are waves of depolarization transmitted from cell to cell in smooth and cardiac muscle?

A

gap junctions

49
Q

Sympathetic neurons exit the _____ and _____ regions of the spinal cord.

A

thoracic, lumbar

50
Q

Parasympathetic neurons exit the ____ and _____ regions regions.

A

cranial, sacral

51
Q

Post ganglionic sympathetic neurons are _____ than parasympathetic.

A

longer

52
Q

Which has extensive branching, sympathetic or para?

A

sympathetic so as to synapse with more postganglionic, stimulating the quick fight or flight response

53
Q

What organs do sympathetic neurons inhibit?

A

gallbladder, pancreas, salivary glands

54
Q

What organs do parasympathetic excite?

A

those involved in digestion

55
Q

Why is heart rate an example of antagonistic control?

A

it has dual innervation from sympathetic and parasympathetic neurons of the SA and AV nodes

56
Q

The myocardium of the atria is innervated by ______.

A

sympathetic and parasympathetic

57
Q

The myocardium of the ventricles is innervated by ______.

A

only sympathetic to increase force of contraction

EXSC 463 Exam 1 (12 decks)

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