reflexes

Question 1

what is a reflex action

Answer 1

involuntary response to a stimulus applied to the periphery & transmitted to CNS(spinal cord, medulla and/or cortex)

Question 2

characteristics of reflex action

Answer 2

repeatable
directed and purposeful
rapid

Question 3

definition of motor unit

Answer 3

one motor nerve and skeletal muscle fibers it innervates

Question 4

each skeletal muscle bundle has mix of __ types of motor units

Answer 4

3

Question 5

types of motor units

Answer 5

slow twitch-fatigue resistant
fast twitch-fatigable
fast twice-fatigue resistant

Question 6

slow twitch fatigue resistant

Answer 6

S, type I, red
many mitochondria, much myoglobin
slow contraction, develops little tension, high endurance,

Question 7

slow twitch fatigue resistant adapted for

Answer 7

posture maintenace

Question 8

fast twitch fatigable

Answer 8

FF, type IIb, glycolytic, white
abundant glycogen
large fiber diameter, small to very large motor units
fast contraction, high tension, low endurance

Question 9

fast twice fatigable mainly for

Answer 9

strong bursts of tension but some adapted for precision movements

Question 10

fast twice fatigue resistant

Answer 10

FR, type IIAb, type IIa, oxidative-glycolytic
mitochondria glycogen&myoglobin
large fiber diameter
intermediate motor units
fast contraction, significant tension, moderate to high endurance

Question 11

fast twice fatigue resistant adapted for

Answer 11

strong bursts of continuous activity like walking

Question 12

FF fibers with training can develop into

Answer 12

FR
•Example; Compared to your initial efforts at jogging, the speed and distances you can jog without fatigue will increased.

Question 13

what gives demand to move a limb

Answer 13

motor cortex

Question 14

size principle

Answer 14

MUs receive common neural input and are recruited according to their sizes

Question 15

there is progression from ___ motor units to ____ motor units as motion action is effected

Answer 15

small –> larger

Question 16

during sustained activity, ___ motor units are activated and muscle fibers cycle in ____

Answer 16

larger IIb; rotation

Question 17

what happens to precision of motor skills during prolonged task

Answer 17

degrades

Question 18

reflexes are mediated using

Answer 18

hard wired pre-existing nerve circuits

Question 19

reflexes generally integrated at

Answer 19

spinal cord level

Question 20

modulation of reflex activity is

Answer 20

product of other circuits

Question 21

control signals from higher centers are sent by ___

Answer 21

interneurons to motor nerves controlling reflex

Question 22

how are receptors located in monosynaptic reflex

Answer 22

parallel

Question 23

what kind of nerve enters cord in monosynaptic reflex

Answer 23

afferent nerve from spindle(1a fiber)

Question 24

what does efferent nerve do in monosynaptic reflex

Answer 24

goes from cord to affected motor units

Question 25

what is adequate stimulus of monosynaptic reflex

Answer 25

rapid stretch of motor unit

Question 26

types of length receptors in muscle spindle

Answer 26

``` intrafusal fibers(nuclear bag fibers) nuclear chain fibers ```

Question 27

what do intrafusal fibers mediate

Answer 27

phasic/dynamic response

Question 28

skeletal muscle derivatives have striations at ___

Answer 28

end of spindle

Question 29

ends of spindle innervated by

Answer 29

gamma efferent fibers 1a in center of nuclear bag fiber 1a fiber wrapped around nuclear bag fiber

Question 30

when muscle is stretched ___ tension on cytoskeletal strands pulls open ___ channels of 1a fiber

Answer 30

increased | ionic (Na)

Question 31

intrafusal fibers have __compliance

Answer 31

high easily distorted rapidly adapt to prolonged stretch

Question 32

what do low compliance nuclear bag fibers mediate

Answer 32

``` dynamic and static response low compliance stimulate type II fibers tonic give data on position of limb in space ```

Question 33

sequence of stimulation

Answer 33

muscle rapidly stretched and circuit activated intrafusal fibers (muscle spindles) depolarize 1a nerves &AP results activated 1a fibers enter cord in dorsal ramus 1a fibers stimulate alpha motor nerves in cord

Question 34

contraction of extrafusal fibers __ stretch on spindle

Answer 34

unloads ia fibers stop firing alpha motor nerves not stimulated

Question 35

reflex disadvantageous if

Answer 35

you want to hold precise position

Question 36

reflex resists rapid stretch but also establishes ___ in resting muscle

Answer 36

tension | to oppose gravity

Question 37

3 neural circuits that modulate monosynaptic reflex

Answer 37

reciprocal innervation renshaw arc gamma efferents

Question 38

what is reciprocal innervation important circuit for

Answer 38

monosynaptic and multisynaptic reflexes

Question 39

reciprocal innervation purpose

Answer 39

enhance action of agonist muscle by reducing resistance to movement from antagonist muscle

Question 40

where do gamma efferent nerves originate from

Answer 40

reticular activating system

Question 41

what do gamma efferent nerves innervate

Answer 41

polar ends of intrafusal fibers

Question 42

what is recurrent inhibition

Answer 42

•Twigs of motor nerves activate interneurons called Renshaw cells

Question 43

purpose of renshaw arc

Answer 43

confines reflex to one group of muscles w/o interference from other muscle groups

Question 44

renshaw arc inhibits other ___ motor nerves and ___ motor neuron

Answer 44

parallel | same

Question 45

in renshaw arc GABA and glycine increase ___ conductance through channel

Answer 45

Cl-

Question 46

renshaw arc modulates the reflex to avoid ____ response

Answer 46

over exuberant

Question 47

primary function of inverse myotatic reflex/golgi tendon reflex

Answer 47

equalize forces between agonist and antagonist muscles across a joint stabilizes limb across other joints

Question 48

secondary function of inverse myotatic reflex

Answer 48

prevents muscle and or tendon tearing if muscle tendon is subjected to rapidly induced high levels of tension

Question 49

golgi tendon reflex senstive to force developed at the

Answer 49

tendons

Question 50

after stimulation of golgi tendon organ, agonist muscle is ____ by interneurons and antagonist muscle is ____

Answer 50

inhibited | stimulated

Question 51

flexor withdrawl reflex is the motor response to

Answer 51

sensory reception of pain | pain reflex

Question 52

once flexor withdrawal reflex stimulated, ipsilaterally motor nerves of flexor groups are ____ contralaterally motor nerves of flexor groups ___

Answer 52

stimulated to contract inhibited - extensor groups stimulated to contract - double reciprocal inhibition/crossed extensor reflex