Reflexes

Question 1

All reflexes are monosynaptic. T/F?

Answer 1

False

Question 2

The magnitude of a reflex can be modulated by higher brain centres. T/F?

Answer 2

True

Question 3

Fibres within a muscle spindle are termed ‘intramural’. What is the term for the contractile muscle fibres outwit the muscle spindle?

Answer 3

Extrafusal

Question 4

What type of sensory neuron innervates muscle spindles?

Answer 4

Ia sensory neuron

Question 5

How does the lengthening of a muscle affected the discharge rate of Ia sensory neurons?

Answer 5

Stretching (due to muscle lengthening) in the middle third of the intramural fibres leads to the increased depolarisation of the Ia axon endings due to opening of mechxnosensitive ion channels

Question 6

Sensory Ia efferent have an excitatory synapse in the spinal cord with what type of motor neuron?

Answer 6

Alpha motor neuron

Question 7

Gamma motor neurons innervate the contractile portions at the end of intramural muscle fibres, to cause these poles of the intramural fibre the contract when the extrafusal fibres contract. Why is this important?

Answer 7

This means that when the extrafusal fibres contract, the spindle does not become slack, which allows Ia sensory neurons to report information about muscle length

Question 8

What type of sensory neuron innervates Golgi tendon bodies?

Answer 8

Ib sensory neuron

Question 9

What is the name of the structures found at the junction between muscle and tendon which are innervated by Ib sensory neurons?

Answer 9

Golgi tendon organs

Question 10

How does the firing rate fo Ib afferent fibres change when the tendon organ is stretched?

Answer 10

The firing rate increases

Question 11

Ib sensory afferents, which transmit information from Golgi tendon organs, have excitatory synapses with alpha motor neurons. T/F?

Answer 11

False - these are inhibitory synapses

Question 12

Tendon organs form part of a reflex circuit which inhibits homonymous and synergist neurons. What is the term for this system?

Answer 12

The inverse myotactic reflex

Question 13

Describe the flexion withdrawal reflex.

Answer 13

This protects the limbs against potentially noxious stimuli detected by cutaneous structures. the flexors of the affected limb contract and the extensors are relaxed to draw the limb away from the noxious stimuli. At the same time the crossed extensor reflex is elicited in the contralateral limb to contract the extensors and relax the flexors in order to provide postural support during the withdrawal of the stimulated limb

Question 14

Why is a positive Babinski’s sign commonly seen in infants?

Answer 14

The corticospinal tract is not yet fully myelinated in infants

Question 15

What cranial nerve innervates the Jaw jerk reflex?

Answer 15

Trigeminal nerve

Question 16

What spinal roots innervate the biceps reflex?

Answer 16

C5/6

Question 17

What spinal roots innervate the triceps reflex?

Answer 17

C6/7/8

Question 18

What spinal roots innervate the brachioradialis reflex?

Answer 18

C5/6

Question 19

What spinal roots innervate the knee jerk reflex?

Answer 19

L3/4

Question 20

What spinal roots innervate the ankle jerk reflex?

Answer 20

S1/2

Question 21

Describe how reinforcement measures work to recruit more motoneurons into the reflex response?

Answer 21

Reinforcement measures use higher brain centre modulation to slightly depolarise some of the motoneurons in the pool to bring them closer to threshold and make them easier to excite

Question 22

The tendon jerk reflex is useful clinically but it is a response to an artificial stimulus. What is its normal function?

Answer 22

Acts to produce prolonged contraction when there is prolonged stretch of the muscle to maintain a constant muscle length and to control muscle tone

Question 23

Highly sensitive areas of skin such as on the hands and lips have lots of small receptive fields as compared to less sensitive areas such as the trunk which has fewer, bigger receptive fields. T/F?

Answer 23

True

Question 24

What must happen for two sensory stimuli on the skin to be perceived as separate?

Answer 24

These stimuli must activate different receptors i.e. they must ‘land’ in different receptive fields

Question 25

Explain the differences in two point discrimination between highly sensitive areas such as the hands, and less sensitive areas such as the trunk?

Answer 25

In the more sensitive areas there are multiple, small receptive fields whereas on the trunk there are fewer, bigger receptive fields. Stimuli must act on separate receptive fields to be perceived as separate. therefore, stimuli can be much closer together and still perceived as separate on areas such as the hand compared to areas such as the trunk

Question 26

What is kinaesthesia?

Answer 26

sense of movement speed of movement direction of movement

Question 27

Rufini endings, Golgi endings and free nerve endings are rapidly adapting. T/F?

Answer 27

False - they are slow adapting

Question 28

Paciniform endings are rapidly adapting. T/F?

Answer 28

True

Question 29

Subcutaneous receptors may discharge during movement to provide the sense of proprioception. T/F?

Answer 29

True

Question 30

Primary muscle spindle endins respons to changing length and to tapping or vibrating of the tendon. T/F?

Answer 30

True

Question 31

Opposing muscles at a joint (e.g. biceps and triceps) provide complementary information about joint flexion/extension. T/F?

Answer 31

True

Question 32

In the experiment, if vibration was applied to the biceps tendon of the right arm with the eyes closed and the subject asked to match the level of elbow flexion in the left arm to that of the right arm, the subject will extend their left arm further. Why is this?

Answer 32

the vibration is creating an artificial stimulus on the biceps muscle spindles which creates the impression that the muscle is longer than it actually is which accounts for why the subject would extend their arm further than they should on the left side

Question 33

Platinum grid array electrodes are used for seizure monitoring and brain mapping on subdural cortical surface in conscious patients. This is an invasive procedure. Name to non-invasive methods of brain stimulation?

Answer 33

Transcranial electrical stimulation | Transcranial magnetic stimulation