Reflexes

Question 1

What are reflexes

Answer 1

Involuntary actions

Question 2

What about reflexes mean they have a short latency

Answer 2

Single synapse

Question 3

What are motor neurons activated by

Answer 3

• various brain reflexes
• various peripheral receptors

Question 4

Where can motor cell bodies

Answer 4

Ventral horn of the spinal cord or in cranial nerve nuclei

Question 5

Describe muscle spindles

Answer 5

• sensory endings wrapped around the intrafusal fibres
• when the muscles contract the muscle spindles relax

Question 6

How many synapses are the ventral horn

Answer 6

Only one synaptic transmission in the ventral horn

Question 7

What are some components of the reflex pathway

Answer 7

• stimulus
• receptor activation (mechanoreceptor)
• stimulus transduction AP conduction along sensory axon (A alpha)
• synaptic transmission
• motor neuron recruitment AP conduction along motor axon
• synaptic transmission (effector recruitment)
• response

Question 8

What are the different jerk reflexes

Answer 8

• biceps jerk reflex
• ankle jerk reflex
• tricep jerk reflex
• rectus abdominus reflex

Question 9

Describe the jaw jerk reflex

Answer 9

• hammer tap to the chin
• stretches spindles of jaw elevator muscles (Masseter, temporalis, medial pterygoid)
• action potentials conducted along group 1a muscle afferents to the brainstem (Aalpha)
• monosynaptic activation of motor neurons jaw elevator muscles
• action potentials travel along motor axon
• jaw muscles contract
• jaw jerks upwards, mouth closes

Question 10

What is the ankle jerk reflex

Answer 10

• hammer tap to Achilles’ tendon
• stretches spindles within gastrocnemius
• action potentials conducted along 1a muscle afferents
• monosynaptic activates neurons of gastrocnemius muscle
• axon potentials
• gastrocnemius muscle contracts
• foot extends (plantar extension)

Question 11

What is the latency of the response

Answer 11

Time between stimulus and response

Question 12

What latency is shorter, jaw jerk or ankle reflex?

Answer 12

The latency for the jaw jerk is less than that for the ankle jerk reflex

Question 13

Why is the latency for the jaw jerk less than that for the ankle jerk reflex

Answer 13

Because the neural pathway for the jaw jerk is less than that for the ankle jerk reflex

Question 14

Is the amplitude more for the jaw jerk reflex or for the ankle jerk reflex

Answer 14

The amplitude for jaw jerk is less than that for the ankle jerk reflex

Question 15

Why is the amplitude bigger jaw jerk and the ankle jerk reflex

Answer 15

The masseter is a smaller muscle than gastrocnemius, recruitment of muscle fibres in masseter less than for gastrocnemius

Question 16

What are the somatic reflexes receptors

Answer 16

Propnoiceptor endings, group la muscle fibres, homozygous motor neurons

Maintenance of posture and muscle tone

Question 17

What are the somatic reflexes functions

Answer 17

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

Question 18

What is the flexation withdrawal reflex

Answer 18

• inhibition of motor neuron activation
• inverse myotactic reflex (inverse stretch reflex)
• prevents over loading of muscle

Question 19

What is bite force controlled by

Answer 19

Loading of the periodontal ligament

Question 20

What does anaesthesia of molars do to bite force

Answer 20

Increases bite force

Question 21

What is the activation of the pharyngeal reflex

Answer 21

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

Question 22

The pharyngeal reflex involves the stimulation of what fibres

Answer 22

Stimulation of sensory fibres from the glossopharyngeal nerve and/or the Trigeminal nerve

Question 23

Where do the afferents of the pharyngeal reflex

Answer 23

Afferents terminate in the brainstem

Question 24

Where do the inter neurons in the pharyngeal reflex project from

Answer 24

The Spvn to nucleus ambigus (X motor neurons)

X afferents then terminate innervate muscles

Question 25

What are the stimuli for salivary reflexes

Answer 25

Gustatory (taste), visual, olfactory, chewing

Question 26

What is the outcome of salivary reflexes