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NEURO 3000 > ch. 13 - spinal control of movement > Flashcards

ch. 13 - spinal control of movement Flashcards

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1
Q

motor system

A

all muscles and the neurons that control them

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2
Q

behavior requires the coordination of how many muscles?

A

almost 700

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3
Q

smooth muscle

A

lines the GI tract, arteries, and related structures; innervated by autonomic nervous system

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4
Q

what is the role of smooth muscles?

A

peristalsis and blood flow

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5
Q

cardiac muscle

A

heart muscle that functions without innervation but can be modified by ANS

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6
Q

skeletal muscle

A

the bulk of muscles mass; muscle within a sheath and composed of hundreds of fibers. innervated by CNS

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7
Q

functions of skeletal muscle

A
  • move bones around joints
  • move eyes within the head
  • control respiration
  • control facial expression
  • produce speech
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8
Q

muscles that work in opposite directions

A

synergists and antagonists

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9
Q

T or F: muscles ONLY pull (shorten), not push

A

true

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10
Q

axial muscles

A

move trunk, posture

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11
Q

proximal muscles

A

move shoulder, elbow, knee, and pelvis - locomotion

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12
Q

distal muscles

A

move fingers, feet, and hands - manipulation of objects

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13
Q

which neurons command muscle contraction?

A

ONLY lower motor neurons

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14
Q

lower motor neurons (LMN)

A

distributed in proportion to skeletal muscle density

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15
Q

LMN controlling flexors are located…

A

dorsal to extensors

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16
Q

LMN controlling axial muscles are located…

A

medial to those controlling distal muscles

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17
Q

which type of LMN triggers muscles?

A

alpha motor neurons

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18
Q

which typer of LMN innervates intrafusal fibers?

A

gamma motor neurons

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19
Q

motor unit

A

one alpha motor neuron and all muscle fibers it innervates

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20
Q

motor neuron pool

A

all alpha motor neurons which innervate a single muscle

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21
Q

what is NT used by alpha motor neurons?

A

acetylcholine (ACh)

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22
Q

how does the CNS grade muscle contraction?

A

by controlling firing rate of motor units and by recruiting more motor units

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23
Q

size principle

A

small motor units have small motor neurons, large have large

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24
Q

are small or large neurons more easily excited?

A

small

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25
twitch
rapid sequence of contraction and relaxation
26
"dark meat"
- red muscle fibers - slow to contract - slow to fatigue - present in antigravity muscles - many mitochondria - use oxidative metabolism
27
"white meat"
- fewer mitochondria - anaerobic metabolism - rapid - powerful - fatigue rapidly - present in "escape muscle"
28
fast motor units contain
white fibers | - 30-60 AP/sec bursts
29
slow motor units contain
red fibers | - 10-20 AP/sec steady
30
crossed-innervation experiment
muscle switched phenotype to match motor neuron type
31
sarcomere
a segment compromised of two Z lines and the myofibril in between
32
myosin
major thick filament protein
33
actin
major thin filament protein
34
why is Ca2+ required for muscle contraction?
- it initiates contraction by binding to troponin | - contraction continues as long as Ca2+ and ATP are available
35
steps of excitation
1. AP occurs in alpha motor neuron 2. ACh is released by axon terminal at NMJ 3. nicotinic receptor channels in sarcolemma open, posysynaptic sarcolemma depolarize (EPSP) 4. voltage-gated Na+ channels open, AP is generated in muscle fiber, which sweeps down the sarcolemma and into T tubules 5. depolarization of T tubes causes Ca2+ release from sarcoplasmic reticulum
36
steps of contraction
1. Ca2+ binds to troponin 2. myosin binding sites on actin are exposed 3. myosin heads bind actin 4. myosin heads pivot 5. myosin heads disengage at the expense of ATP 6. cycle continues as long asCa2+ and ATP are present
37
steps of relaxation
1. as EPSPs end, the sarcolemma and T tubules return to their rest potentials 2. Ca2+ is sequestered by sarcoplasmic reticulum by an ATP-driven pump 3. myosin binding sites on actin are covered by troponin
38
excitation-contraction coupling
this AP, excitation, triggers release of Ca2+ from organelle inside muscle fiber, which leads to the contraction of the fiber
39
sliding filament theory
process of sacromere shortening when thin filaments slide toward one another on the thick filament
40
muscle spindles
- stretch receptor | - specialized muscle fibers in a fibrous capsule
41
Ia sensory axons
- largest and fastest - innervate spindle - enter spine at dorsal roots - synapse on interneurons and alpha motor neurons
42
proprioception
body sense
43
myotatic reflex
- aka stretch reflex | - involves sensory feedback from muscle, shown by cutting the dorsal roots
44
what is an example of myotatic reflex?
knee jerk
45
intrafusal fibers
modified skeletal fibers within the muscle spindle
46
gamma motor neurons
- innervate intrafusal fibers | - activation keeps the muscle "on air" by contracting the poles of the spindle
47
alpha activation alone..
decreases Ia activity
48
gamma activation alone...
increases Ia activity
49
circuit of myotatic feedback loop
gamma motor neuron to intrafusal muscle fiber to Ia afferent axon to alpha motor neuron to extrafusal fiber
50
golgi tendon organ
- monitors muscle tension or force of contraction | - located in series
51
what innervates golgi tendon organ?
Ib sensory neurons
52
reverse myotatic reflex
- keeps muscle from being overloaded - muscle tension in optimal range - important for manipulation of fragile objects
53
joint receptors
- combined with muscle spindle, golgi tendon organ, and skin receptors - rapidly adapting
54
synaptic input from spinal interneurons
- primary sensory axons - descending axons from brain - collateral of LMN axons - other interneurons
55
reciprocal inhibition
the contraction of one set of muscles accompanied by the relaxation of the antagonists muscle
56
flexor reflex
complex reflex arc used to withdraw limb from adverse stimulus
57
crossed-extensor reflex
the activation of extensor muscles and the inhibition of flexor muscles on the OPPOSITE side
58
central patter generators
produce rhythmic motor activity
59
rhythms are produced by...
pacemaker cells and synaptic connections
60
rhythmic activity steps
1. membrane depolarizes 2. Na+ and Ca2+ flow into cell through NMDA receptors 3. Ca2+ activates potassium channels 4. K+ flows out of cell 5. membrane hyperpolarizes 6. Ca2+ stops flowing into cell 7. potassium channels close 8. membrane depolarizes, cycle repeats

NEURO 3000 (16 decks)

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