Reflexes

Question 1

Are reflexes voluntary or involuntary?

Answer 1

involuntary

Question 2

How many synapses do stretch reflexes make?

Answer 2

usually only one -monosynaptic

Question 3

What is the common final motor pathway?

Answer 3

recruitment of motor neurones

Question 4

Where can motor cell bodies be found?

Answer 4

ventral horn of spinal cord (somatic)
brainstem (cranial nerves)

Question 5

What can motor neurones be activated by?

Answer 5

various brain regions (cortex)
various peripheral receptors due to reflex

Question 6

What are the intrafusal muscle fibres wrapped in?

Answer 6

sensory endings

Question 7

What do the sensory nerve endings (mechanoreceptors) fuse together to form?

Answer 7

a-Alpha axons

Question 8

What are the steps of the spinal reflex pathway? (knee jerk)

Answer 8

• Stimulus (hammer to knee)
• Receptor activation (mechanoreceptor- sensory endings around intrafusal muscles)
• Stimulus transduction
  AP conduction along sensory axon (Aa)
• Synaptic transmission in the spine
• Motor neuron recruitment
  AP conduction along motor axon (Aa)
• Synaptic transmission
  (Effector recruitment )

Response (knee contract and lifts up)

Question 9

What muscles are stretched in the jaw-jerk reflex?

Answer 9

jaw elevators - temporalis, medial pterygoid, masseter

Question 10

Why is the latency for the jaw jerk reflex shorter than for the ankle jerk reflex?

Answer 10

the neural pathway for the jaw jerk reflex is shorter than that for the ankle jerk

Question 11

What is the amplitude?

Answer 11

Measure of electrical activity in skeletal muscle

Question 12

Why is the amplitude for the jaw jerk reflex less than for the ankle jerk reflex?

Answer 12

Masseter = smaller muscle than gastrocnemius
Recruitment of muscle fibrils in masseter less than for gastrocnemius
Smaller amplitude of response

Question 13

What receptors and nerve fibres do tendon-jerk reflexes include?

Answer 13

Proprioceceptor endings
Group 1alpha muscle afferents

Question 14

Why are protective mechanisms of somatic reflexes important?

Answer 14

• Escape mechanism
• Prevention of muscle overloading
• Prevention of inadvertent ingestion of a foreign body
• Digestive aid

Question 15

How many synapses does a flexion withdrawal reflex have?

Answer 15

two synapses (disynaptic)

Question 16

In the flexion withdrawal reflex, what prevents instant reflex which may cause further harm via inhibition (i.e not throw pot of boiling water)?

Answer 16

interneuron which allows momentary control over situation and inhibits harmful action

Question 17

In the flexion withdrawl reflex, what are two responses that can occur?

Answer 17

can inhibit or stimulus different spinal regions through many inter-neurons to maintain balance or protect against further injury

Question 18

What triggers the flexion withdrawl reflex?

Answer 18

pain (mechanical or heat)

Question 19

What are golgi tendon organs?

Answer 19

proprioceptors that are located in the tendon

Question 20

What are inverse stretch reflexes?

Answer 20

golgi tendon organs activated by stretch and contraction
afferent signals cause inhibiton of motor neurons
prevents overloading of muscle

Question 21

Does an increase in synapses affect latency?

Answer 21

yes more synapses increased latency

Question 22

What protects the mouth from increased bite force?

Answer 22

no golgi tendon organs therefore controlled by increased periodontal loading which sends afferent signals which inhibit elevation of jaw muscles

Question 23

What does anaesthetisation of molars cause?

Answer 23

increased bite force as periodontal ligament cannot send feedback loop

Question 24

Where do interneurones project in the pharyngeal reflex to cause mass contraction?

Answer 24

nucleus ambigious (motor control)

Question 25

What does the gag (pharyngeal) reflex result in?

Answer 25

billateral contraction of posterior oral and pharyngeal muscles

Question 26

What nerve fibres are stimulated upon activation of sensory mechanoreceptors? (gag reflex)

Answer 26

glossopharyngeal
trigeminal

Question 27

What stimuli can affect salivary flow?

Answer 27

Gustatory (taste) stimuli
Visual, olfactory stimuli
Chewing forces