Block 2 Reflexes

Front 1

3 parts of the reflex arc

Back 1

1) specific type of sensory receptor+afferent fibers
2) interneurons in spinal gray matter
3)specific sets of alpha-motorneurons

Front 2

muscle spindles do what?


shape?

Back 2

stretch receptors in the muscles that detect an increase in muscle length

fusiform shape

Front 3

muscle spindles run _____ with striated muscle fibers (which are called ?)

Back 3

run parallell with extrafusal fibers

Front 4

what are intrafusal fibers? what is entwined around them?

Back 4

small diameter modified muscle fibers. a few in spindle organs. A-M on the polar ends.

afferent nerve fibers enter the center of the connective tissue capsule surrounding each spindle and entwine around the intrafusal fibers.

Front 5

The afferent axons around intrafusal fibers are called ______. they have a _____ diameter, and ______myelinated. they are sensitive to ______ stretch.

Back 5

Ia afferent axons

large diatmeter, heavily myelinated

sensitvie to rapid/phasic stretch

Front 6

Type II fibers do what to intrafusal fibers (what does it look like?)

most sensitive to what type of stretch?

Back 6

Type II fan-out over intrafusal "flower spray"

sensitive to tonic stretch. small myelinated

Front 7

gamma motoneurons are found where

Back 7

motor endplates on the polar ends of intrafusal fibers. intermediate diameter

Front 8

all motor control activity converges on what?

Back 8

alpha motor neuron pools

Front 9

a defect in a reflex can be caused by what?

Back 9

1) disorder of the afferents,
2) disorder of the efferents
3) disorder of synaptic connections

Front 10

during passive stretch of the muscle, spindle afferents....?

what are the 2 responses?

Back 10

increase firing proportional to muscle length

tonic response=primary+secondary endings discharge proportional to static length

phasic=primary endings have strong dynamic discharge proportional to the RATE of change of length

Front 11

Stretch of a muscle results in what?

Back 11

1) contraction of it and it's synergists
2)relaxation of antaonists (inhibited)=reciprocal inhibition

Front 12

what is the functional role of the stretch reflex?

Back 12

it restores muscle length in the face of an external disturbance

ex.) holding a glass, starts to get filled up, passively stretching muscle, causing spindle afferent firing to excite motoneurons to the same/synergist muslces=>increase in muscle tone and restores muscle to original length

Front 13

so how do the motoneurons receive a signal from the intrafusal fibers? what kind of motor axons and where do they synpase? what does this cause in central region? why? final results?

Back 13

via gamma motor neurons-exclusive to muscle spindles

gamma motor axons excitatory synapses on polar ends of intrafusal fibers

gamma efferents actually cause a shortening in the polar regions-->>>stretching in the central region

this stretching results is an increase in spindle afferent discharge

Front 14

alpha neurons exclusively innervate

Back 14

extrafusal fibers

Front 15

alpha-gamma coactivation: during ___ contractions, gamma and alpha are stimulated at the same time so that...?

results in what?

Back 15

voluntary contractions,

so that the spindle can continue to be sensitive to length throughout contraction

results in extrafusal fibers and spindles shortening at the same rate, keeping spindles responsive to stretch during muscle shortening.

Front 16

golgi tendon reflex: firing freq is proportional to what?

Back 16

to CONTRACTILE force (opposite of stretch reflex!)

Front 17

what type of axons are used in golgi tendon reflex? where do they entwine?

Back 17

afferent fiber branches=Ib
entwine alomng collagen fibers in musculo-tendon junction

Front 18

circuit for golgi tendon (inverse myotatic) reflex.

stimulus=?
response=?

Back 18

stimulus: large increase in tension (detected by golgi tendon organs)

response: relation of same muscle

Front 19

what is the results of the GTP reflex?

Back 19

relaxation of the homonymous muscle+excitatation of antagonists

Front 20

4 functional roles of GTO reflex?

Back 20

1) compensation for muscle fatigue
2)reduction of contraction upon contact of limb with object
3)reduction of contraction at limits of joint movement
4)protection from over-stress of muscle

Front 21

Flexion (Withdrawl) Reflex does what?

stimulus?
response?

what is inhibited?

the larger the stimulus....

Back 21

protective reflex withdrawls part of body away from damaging stimulus

stimulus: nociceptors activation
response: contraction of muscles to remove body part from site of injury (usually flexors)

flexor excited, extensor inhibited

...the more muscles/joints involved in response

Front 22

crossed extension reflex happens when?

as stimulus increases....

strong flexion in one limb->>>?

Back 22

at high levels of nociceptive stimulus

as stimulus increases, rate of afferent firing increase-->>>addional motor neuron groups recruited

strong flexion in one limb-->>>extension in opposite limb.

Front 23

infant reflexes

Back 23

extensor thurst reflex

stim=plantar pressure
resp=extension of limb against contact

changes with development, once corticospinal race is myelinated.

Front 24

central pattern generators. During walking, running, each limb goes through a repetive cycle of _____ phase and _____phase

what neurons are responsible for this?

Back 24

stance phase (extension)
swing phase (flexion)

cycle out of sync with each other

interneuronal circuits at spinal/brainstem levels