BMS11004 WEEK 10 - WEDNESDAY

Question 1

define reflex

Answer 1

rapid, involuntary, stereotyped and coordinated response to sensory stimulus (usually involving muscle contractions or gland)

Question 2

what can somatic reflexes also be known as

Answer 2

spinal reflex as involve spinal cords circuitary

Question 3

outline spinal reflex characteristics, speed, suggestions

Answer 3

requires sensory input (stimulation)
quick, involves few synapses
involuntary, automatic, hard to suppress
stereotyped, occuring same way each time suggesting underlying circuitry to be simple

Question 4

what is patellar reflex

Answer 4

sensory input (tap above patella) causes afferent to relay signal into spinal cord and motor neuron
fires = muscle contraction
monosynaptic

Question 5

define monosynaptic

Answer 5

only one synapse involved

Question 6

describe stretch (knee) myotactic reflex

Answer 6

tap on knee stretch thigh extensor muscle and associated tendon
corrects stretch, important to maintain body posture using proprioceptive system
muscle spindles (sensory fibres) sense muscle stretch and send signal to spinal cord
direct monosynapse on motor neuron fire AP
reciprocacl inhibition of other muscle to relax

Question 7

what is a muscle spindle

Answer 7

proprioceptor- sense organs monitoring position and movement of body parts
found in most striated muscle

Question 8

what are muscle spindles innervated by

Answer 8

1a sensory fibres, providing feedback to alpha motor neurons innervating surrounding muscle on amount of muscle stretch

Question 9

what are the muscles IN muscle spindles innervated by

Answer 9

axons from gamma (y) motor neurons, stimulates infrafusal muscle fibres to adjust tension in spindle as extrafusal muscle fibres surrounding muscle contract, so muscle spindle is never slack

Question 10

what are golgi tendon organs

Answer 10

type of proprioceptor detecting muscle tension due to muscle contraction (NOT STRETCH)

Question 11

how do golgi tendon organs use GTO sensory afferents to work

Answer 11

activate GTO sensory Ib afferents activates inhibitory interneurons, which inhibit alpha motor neurons that innervates same muscle

Question 12

explain how golgi tendon reflex is a negative feedback circuit

Answer 12

regulates muscle tension and protects muscle by regulating muscle contraction, maintaining muscle length, preventing over-contraction

Question 13

outline flexor withdrawal reflex

Answer 13

quick contraction of flexor muscles to withdraw limbs from injury due to activating nocieptive sensory receptors (nociceptors)

Question 14

what receptors sense pain

Answer 14

nocieptive sensory receptors (nociceptors)

Question 15

despite speed of response, explain why flexor reflex is a polysynaptic reflex

Answer 15

activate many excitatory interneurons sustains response
“parallel after-discharge circuit”
inhibitory interneurons also activated to relax extensor muscles (reciprocal inhibtion)

Question 16

how is balance maintained in flexor reflex

Answer 16

rapid withdrawal of limb causes imbalance = contralateral element
crossed extensor reflex provides postural support during limb withdrawal

Question 17

what is parallel-after-discharge circuit

Answer 17

assume time taken to cross each synapse is same
stimulus initiated by A will take different time to reach output neurons Z
meaning inital signal are sustained over extended periods

Question 18

explain how simple reflex could underlie repetitive behaviours

Answer 18

when walking, extensors and flexors are alternatively activated/inhibited
central pattern generators is presence of local circuit that generates pattern of alternating flexion and extension

Question 19

explain sigmoidal movement and its importance

Answer 19

simple organism movements (worm wiggling) used to study proprioception