Intro to movt control spinal cord and reflexes

Question 1

What is a reflex?

Answer 1

Stereotyped involuntary response to a stimulus and not subject to conscious control

Question 2

What mediates autonomic reflexes

Answer 2

autonomic nervous system activating smooth muscle, cardiac muscle and glands

Question 3

What mediates somatic reflexes

Answer 3

somatic nervous system

Question 4

What is the function of a monosynaptic reflex

Answer 4

maintains upright posture and controls leg stretch

Question 5

What are the components of a monosynaptic reflex?

Answer 5

Receptor= muscle spindle
Afferent = myelinated, large A alpha afferent axon
Interpretation = spinal cord
Efferent = alpha motor neuron; large and unmyelinated 
Effector = muscle fibres

Question 6

What is endoneurium

Answer 6

surrounds individiual nerves

Question 7

What is perineurium

Answer 7

surrounds a bundle of nerves

Question 8

What is epineurium

Answer 8

surrounds entire nerve fibre

Question 9

What are the components of a post synaptic reflex?

Answer 9

Proprioceptor in skeletal muscle (Golgi tendon in series and spindle fibres in parallel)
Input carried via sensory neurons to CNS
CNS integrates input signal (interneurons)
Somatic motor neurons carry output via alpha motor neurons
Effectors - contract skeletal muscles

Question 10

What proprioceptors exist in muscle

Answer 10

Golgi tendons in series and spindle fibres in parallel

Question 11

Why are there both intrafusal and extrafusal fibres in muscle spindles

Answer 11

so spindles move independently to muscle

Question 12

Why is it important that muscle spindles are sometimes independent to muscles

Answer 12

if it always reflexed and trigger contraction everytime the muscle got stretched then there would be no control of muscle movements

Question 13

How are automatic reflexes from muscle spindles prevented to allow more control of muscle movement

Answer 13

alpha fibre to extrafusal fibre gives a collateral to the gamma motor neuron (to the intrafusal fibre) preventing a reflex.

Alpha-Gamma coactivation

Question 14

What is the withdrawal reflex an example of

Answer 14

total flexor pattern

Question 15

What is reciprocal inhibition

Answer 15

In a total flexor pattern/withdrawal reflex the flexors need to be excited but the extensors need to be inhibited

Question 16

What are intersegmental reflexes

Answer 16

When total flexor reflex occurs muscles controlled by different segments of the spinal cord need to react together.

Question 17

Describe the tracts that come down from the brain to inhibit reflexes

Answer 17

Two long tracts: pyramidal and extrapyramidal

Question 18

What are Renshaw cells

Answer 18

inhibitory neuron

Question 19

What are the types of pyramidal tracts

Answer 19

corticospinal (cortex to spine)

corticobulbar (cortex to brainstem)

Question 20

What are the types of extrapyramidal tracts

Answer 20

vestibulospinal = vestibular nerve
tectospinal = superior colliculi to midbrain
reticulospinal = MRST - pons; LRST - medulla (medial/lateral reticulospinal tracts)
Rubrospinal = midbrain

Question 21

Describe the vestibulospinal tract

Answer 21

works ipsilaterally - controls balance and posture. Innervates flexors in upper limbs and extensors in lower limbs

Question 22

Describe the tectospinal tract

Answer 22

cervical spine, coordinates head movts. in relation to visual stim. (like responding to waving)

Question 23

Describe the reticulospinal tract

Answer 23

MRST - increases muscle tone - excitatory to voluntary movt

LRST - decreases muscle tone - inhibitory to voluntary movt

Question 24

How is the vestibular apparatus a sense organ

Answer 24

it gives an idea of orientation relative to vertical

Question 25

How are visual reflexes processed

Answer 25

eye - lateral geniculate reflex - midbrain

Question 26

What are the types of abnormal reflex

Answer 26

absent, distorted, exaggerated, asymmetrical