Movement Spinal Control

Question 1

muscle contraction

Answer 1

controls all movement, flexors: create smaller joint angles, extensors: create larger joint angles, relaxation: lack of contraction

Question 2

alpha motor neuron

Answer 2

cells in ventral root of spinal cord, cause the contraction of muscles

Question 3

rostral- caudal organization

Answer 3

size of ventral horns corresponds to amount of muslce in the area, amount of white matter corresponds to amount of axons in the area (how faw away from brain)

Question 4

dorsal-ventral and medial-lateral organization

Answer 4

Question 5

strucutre of muscle fiber

Answer 5

many myofibrils make up a fiber, T-tubules contain extra-cellular solution, sarcoplsmic reciculm is like the ER, sarcolema is the plasma membrane

Question 6

getting ready for muscle fiber contraction

Answer 6

muscle has Ach receptors (ionotropic, Erev ~ 8), Ach depolarizes mucle cells producing an AP, AP goes on sarcolema and into T-tubules, at regions where T-tubules are close to sarcoplasmic reticulum there are Ca2+ channels, depolarization opens channels allowing Ca2+ to go out of sarcoplasmic reticulum and into cytosol

Question 7

muscle fiber contraction

Answer 7

at rest, tropomyosin blocks myosin (thick filament) binding sites on actin (thin filament). when troponin binds Ca2+, tropomyosin moves away to expose myosin binding site so thick filament can move along think filament ot produce a contraction, myosin disengages from actin using ATP, if Ca2+ still present, mysoin continues moving, Ach is degraded by acetylcolinesterase, receptors close, sorcolema returns to rest, Ca2+ is acively pumoed back into sarcoplasmic reticulum

Question 8

The NMJ is very reliable because

Answer 8

there is a lot of Ach per vesicle and a high denisty of Ach receptors on the muscle

Question 9

inputs to aplha motor neurons

Answer 9

interneurons: project very locally, in grey matter of spine

muscle spindles: type pf proprioceptor (Ia), directly synapses onto aplha motor neurons

upper motor neurons: help us conciously control movement

Question 10

Reflexes

Answer 10

automatic responses to stimuli, circitry is in spinal cord (doesn’t go to brain)

Question 11

Myotatic reflex purpose

Answer 11

contraction of a muscle fiber in response to muscle stretch, uses propioceptor input

ex. if a box is heaver than we think it is our muscles are streched and we automatically contract muscles more so we are able to hold it up

Question 12

reverse myotatic reflex purpose

Answer 12

inhibition of muscle contraction in response to tension in the tendons, uses propioceptor input

ex. box is way heavier than we think, we feel tension in tendons which connect muscle to bone (can’t risk damage here), muscles give up and drop it

Question 13

flexor/crossed extensor reflex purpose

Answer 13

removes limb from noxious stimulus (flexor) and maintains balance (crossed extensor), nociceptor input

Question 14

myotatic reflex mechanics

Answer 14

Question 15

gamma motor neurons and muscle spindles

Answer 15

gamma motor neurons send signal to intrafusal fibers so the muscle spindles stay online with the extrafusal fibers (which do the contraction) and can detect stretch

Question 16

reverse myotatic reflex mechanics

Answer 16

Question 17

flexor/crossed extensor reflec mechanics

Answer 17