Reflexes

Question 1

Define a reflex and describe 2 types

Answer 1

Involuntary coordinated pattern of muscle contraction/relaxation elicited by peripheral stimulus

Intrinsic (inborn) - unlearned, part of neuroanatomy
Acquired (learned) - auto responses

Question 2

Describe spinal reflexes

Answer 2

Neural pathway between sensory (dorsal/post. root) and motor (ventral/ant. root) system gives rapid response to stimulus via spinal cord.

Doesn’t directly involve the brain

Question 3

Describe adaptability of 2 modified reflexes

Answer 3

Spinal reflexes can be modulated by higher control for appropriate behaviour (condition flexion-withdrawal reflex)
Table support, holding cup

Question 4

Describe muscle spindles

Answer 4

measure muscle length during stretch/contraction

intramural muscle fibres wrapped in set of sensory anulospiral nerve endings; when their shape is changed so is their firing rate

alpha (a) efferent fibres tell main extrafusal muscles to contract
y (gamma) efferent fibres tell spindle intrafusal muscles to contract at the same time

Question 5

Describe the golgi tendon organs

Answer 5

measure muscle tension

form of proprioreceptors in tendon at muscle insertion end

Question 6

Describe stretch reflex and damping with an example

Answer 6

monosynaptic, ipsilateral reflex that aids smooth activity of skeletal muscles

stretch sends afferent signal to spinal cord; sensory neurons synapse with a motor neurons of same muscle whilst inhibitory interneuron signal sent to antagonist reducing tension)

(inhibits antagonist when agonist stimulated - knee-jerk reflex)

Question 7

Describe tendon reflexes

Answer 7

polysynaptic reflex causes muscles to relax/lengthen in response to increased tension activating golgi tendon organs

spinal cord circuit motor neurons inhibited for contracting muscles so agonists stimulated

prevents over contraction/damage (afferent signal to cerebellum adjust contraction)

Question 8

What are crossed reflexes?

Answer 8

Polysynaptic pathways
Right leg - withdrawal/flexion of stimulated limb
Left leg - crossed-extension of contralateral limb to provide support

Question 9

Describe 7 cranial reflexes

Answer 9

Pupillary Light (pupil diameter)
Accommodation (lens adjust)
Corneal (blink)
Jaw jerk (masseter/temporal)
Vestibula-Occular (gaze hold)
Stapedius (mid-ear, loud sounds)
Gag (post. pharynx)

Question 10

Describe how reflexes can be used as clinical tools

Answer 10

Abnormal spinal reflexes identify spinal session
Screening newborns
Abdominal, Plantar, Moro (startle)
Cranial reflexes assess brain death