Reflex Movement

Question 1

what are the types of movement

Answer 1

involuntary actions (reflexes), semi-automatic actions and voluntary actions

Question 2

what are involuntary actions centred on?

Answer 2

spinal cord and brainstem

Question 3

what type of circuit is an involuntary action?

Answer 3

monosynaptic (only 2 neurons)

Question 4

how many neurons are involved in voluntary movement?

Answer 4

2

Question 5

where do the cell bodies of the motor neurons sit in the spinal cord?

Answer 5

in the ventral horn of the grey matter

Question 6

what is the common final pathway of involuntary and voluntary movement?

Answer 6

motor neurons as they both result in muscle contraction

Question 7

what are motor neurons activated by?

Answer 7

various brain regions (cortex) and various peripheral receptors (reflex)

Question 8

what are the 3 horns of a spinal cord segment?

Answer 8

dorsal, intermediate, ventral

Question 9

how do sensory fibres recruit motor neurons?

Answer 9

they do it directly resulting in a motor response

Question 10

what happens as a result of am intervening interneuron in a reflex pathway?

Answer 10

it recruits the motor neuron instead of the sensory neuron making the response slower

Question 11

what are the 7 steps of the reflex pathway?

Answer 11

1 - stimulus activates receptor, 2 - receptor, 3 - afferent neuron has an action potential along axon, 4 - synapse (transmission released here), 5 - efferent motor neuron has an action potential along axon, 6 - effector muscle/gland, 7 - response

Question 12

what receptors and nerves are involved in the tendon-jerk reflex?

Answer 12

proprioreceptor endings, group 1a muscle afferents, homonymous motor neurons

Question 13

what receptors are involved in the cutaneous reflexes?

Answer 13

mechanoreceptor endings and nociceptor endings

Question 14

what is the stretch reflex?

Answer 14

important postural reflex, alters tension in muscle to help maintain constant length

Question 15

what are group 1a muscle afferents?

Answer 15

A alpha axons

Question 16

what does it mean if a reflex pathway contains group 1a muscle afferents

Answer 16

the reflex is a really quick one

Question 17

what axon is used for the monosynaptic reflex arc and what does this mean?

Answer 17

the A alpha axon meaning that the response given is the quickest you can get

Question 18

what are the steps of the ankle jerk reflex?

Answer 18

hammer tap to achilles tendon - stretches spindles within gastrocnemius - action potentials conducted along group 1a muscle afferents to spinal cord - monosynaptic activation of motor neurons of gastrocnemius muscle - axon potentials travel along A alpha motor axon - gastrocnemius muscle contracts - foot extends

Question 19

what are the steps of the jaw jerk reflex?

Answer 19

hammer tap to chin - stretches spindles of jaw elevator muscles - action potentials conducted along group 1a muscle afferents to brainstem - monosynaptic activation of motor neurons of jaw elevator muscle - axon potentials travel along A alpha motor axon - jaw elevator muscles contract - jaw jerks upwards and mouth closes

Question 20

what are the protection mechanisms of the somatic reflexes?

Answer 20

escape mechanism, prevention of muscle overloading, prevention of inadvertent foreign body ingestion, digestive aid

Question 21

what is the stimulus for the flexion withdrawal reflex?

Answer 21

a noxious stimulus e.g. burning fingers but can’t drop what you’re holding so you can control your response a bit

Question 22

what is the interneuron like for the flexion withdrawal reflex?

Answer 22

it is disynaptic with one end influencing the response to the situation

Question 23

what is the receptor for muscle loading activated by?

Answer 23

stretch and contraction

Question 24

what do afferent signals in muscle loading do?

Answer 24

inhibit motor neuron activation

Question 25

what does the muscle loading reflex do?

Answer 25

prevents overloading of muscle

Question 26

what is the bite force in the jaw controlled by?

Answer 26

increasing loading of periodontal ligament

Question 27

what does anaesthesia of molars do to maximum bite force?

Answer 27

increases it

Question 28

what innervates somatic muscle loading?

Answer 28

golgi tendon organs

Question 29

what do golgi tendon organs give rise to?

Answer 29

group 1 afferents

Question 30

what is the pharyngeal reflex (gag reflex) activated by?

Answer 30

mechanoreceptor afferent from the posterior part of the tongue/soft palate

Question 31

what happens in the pharyngeal (gag) reflex

Answer 31

stimulation of sensory fibres from the glossopharyngeal and/or trigeminal nerve - afferents terminate in the brainstem (spino trigemino-thalamus) - interneurons project from spino-trigemino-thalamus to nucleus ambiguous - vagus afferents terminate innervated muscles

Question 32

what does the pharyngeal reflex result in?

Answer 32

mass contraction of both sides of the posterior oral and pharyngeal musculature

Question 33

how does bilateral contraction occur in the oral cavity?

Answer 33

neurons bifurcate to innervate the nucleus ambiguous on both sides

Question 34

what is the outcome of the salivary reflex?

Answer 34

increased salivary flow

Question 35

what are the stimuli of the salivary reflex?

Answer 35

gustatory, visual, olfactory, chewing forces