Neurophysiology

Question 1

Which ONE of the following statements about the functional organization of the brain is CORRECT?

Answer 1

The left cortical hemisphere generally controls the right side of the body.

Usually control is crossed, so the right side of the body is controlled by our left cortical hemisphere.

Question 2

The pitch of a pure tone:

Answer 2

determines where the travelling wave in the basilar membrane has its peak

This is based on the resonance of the basilar fibres.

Question 3

Choose the CORRECT statement. The vestibular system:

Answer 3

uses the utricle and saccule to provide information about static head position

Question 4

With regard to image formation by the eye:

Answer 4

the cornea has greater optical power than the lens

The cornea is roughly twice as powerful as the lens

Question 5

Choose the CORRECT statement about the retina.

Answer 5

Rod photoreceptors outnumber cone photoreceptors throughout the retina except at the fovea.

Cone density is low except at the fovea

Question 6

During normal voluntary muscle contraction (alpha and gamma co-activation):

Answer 6

extrafusal fibres provide most of the contractile force

Intrafusal fibres regulate the spindle activity.

Question 7

Which ONE of the following statements about the spinal cord is INCORRECT?

Answer 7

The spinal nerves have an organization where the sacral nerves tend to innervate the face, and the cervical nerves innervate the legs.

The spinal nerves do exhibit organization, with sacral nerves innervating the lower body, and cervical nerves the upper body and neck

Question 8

The blood-brain barrier

Answer 8

is produced by astrocytes and endothelial cells of the capillary wall.

These two cell types work together to make the barrier.

Question 9

Choose the option that correctly assigns the roles of the outer, middle and inner ear.

Answer 9

outer ear: modify sound based on location of source, middle ear: impedance matching, inner ear: sound transduction

The pinna (outer ear) alters a sound to help with localising front/back and up/down; the middle
ear achieves impedance matching using the piston effect of the different areas of the tympanic membrane and oval window and the lever effect of the ossicles; the inner ear is where transduction of mechanical to electrical energy actually happens.

Question 10

Golgi tendon organs

Answer 10

are in series with extrafusal muscle fibres

The force of the muscle is transmitted through the tendon, and detected by the Golgi tendon organ.

Question 11

Which ONE of the following statements is CORRECT with regard to sensory receptors and afferents? Sensory receptors and afferents characterised as “rapidly adapting” or “phasic”:

Answer 11

generate more action potentials during changes in stimulus intensity than during steady stimulation.

The steady stimulus will lead to adaptation, while the varying stimulus will cause ongoing activity in the
receptor/afferent.

Question 12

Shown in A and B are the action potentials generated in a single tactile afferent over 1s, under two different conditions. The alteration in response from A to B is due to a change in the applied stimulus.
The stimulus change that best accounts for the response change from A to B is:

Answer 12

making the stimulus surface contact the skin with less force.

This is plausible, and suggests it is probably a slowly adapting receptor.

Question 13

Which ONE of the following statements about motor pathways is CORRECT?

Answer 13

The corticospinal tract crosses the midline

Most fibres cross in the medulla, and so give rise to motor cortex controlling the contralateral side of the body.

Question 14

hich ONE of the following statements is CORRECT with regard to the organisation of the spinal cord and peripheral nervous system?

Answer 14

Dorsal root ganglia contain the soma of sensory neurons

Only the dorsal roots have ganglia. The ventral roots take out the motor signals from the motor neurons with their cell bodies in the spinal cord. These sensory neurons are bipolar: they have two axons - one from the receptor and one
going to the CNS.

Question 15

Which ONE of the following statements about optical defects is CORRECT?

Answer 15

Hyperopia is usually not corrected in adolescent patients

The accommodative power of the young eye means that there is no need to correct mild
hyperopia.

Question 16

In transducing mechanical energy into a neural signal, the cochlear hair cells:

Answer 16

utilise an influx of cations to depolarise the hair cell.

In this case K will be the major cation contributor because of the high concentration of K in endolymph and the big driving potential.

Question 17

ch ONE of the following statements about the photoreceptors of the retina is CORRECT?

Answer 17

In the peripheral retina, rods are more common than cones.

Question 18

Inhibitory synapses from a GABA-ergic neuron:

Answer 18

can prevent the post-synaptic neuron from reaching threshold.

This is effectively the ‘mission statement’ for an inhibitory synapse.

Question 19

With regard to the vestibular senses:

Answer 19

The otolith organs can signal linear acceleration without significant adaptation

makes them well-suited to signal the direction of gravitational attraction.

Question 20

With regard to spinal motor neurons:

Answer 20

The activity of an alpha motor neuron can be influenced by descending cortical input

This is correct and necessary otherwise our muscles wouldn’t be much use to us.

Question 21

Reflexes:

Answer 21

can be used to keep a limb in position

Reflexes are best at simple tasks. The myotatic reflex helps hold a limb in position.

Question 22

The traces below show action potential recordings from nine different peripheral afferent fibres. What was the likely movement of the stimulus relative to the finger?

Answer 22

The stimulus was moved along the finger from tip to base.

Question 23

Choose the best option from the following table about spindle and Golgi tendon organ afferents.

Answer 23

A

Question 24

Which ONE of the following statements about cerebrospinal fluid is INCORRECT?

Answer 24

It fills axons and the central canal of the spinal cord.

Intracellular fluid is found inside axons; CSF is an extracellular fluid.

Question 25

In the myotatic reflex:

Answer 25

the extrafusal muscle fibres contract due to 1A activity.

This is the reflex contraction.

Question 26

Which ONE of the following statements is CORRECT with regard to the skin pain system?

Answer 26

Nociceptive afferent fibres are slower to relay a signal to the spinal cord than the afferents for light touch on the fingers.

Nociceptive fibres are type Aδ (small myelinated) or C (unmyelinated) and are both smaller than the large myelinated fibres Aβ that carry light touch from the fingertip.

Question 27

When preparing to reach down and pick up a bag, which brain area would be the final motor area to be activated before the movement begins?

Answer 27

primary motor cortex

The primary motor cortex directly innervates spinal motor neurons and spinal cord interneurons that drive the motor
neurons.

Question 28

Tactile sensory fibres with large receptive fields:

Answer 28

innervate body regions with low receptor densities.

Low receptor densities are associated with low afferent densities and large receptive fields.

Question 29

A person who is unable to see things to the left side of where their gaze is directed has probably suffered damage to:

Answer 29

their right visual cortex (occipital lobe).

Question 30

Three neurons (designated N1, N2 and N3) synapse onto a common post-synaptic neuron. Simultaneous synaptic activity in these neurons has the following effects:
N1 and N2: post-synaptic action potential
N2: post-synaptic action potential
N2 and N3: no post-synaptic action potential
Which of the following is the most likely conclusion?

Answer 30

N1 is sub-threshold excitatory, N2 is supra-threshold excitatory, N3 is inhibitory.

This is one possible scenario

Question 31

Which ONE of the following statements about cerebro-spinal fluid (CSF) is CORRECT?

Answer 31

CSF is made at the choroid plexus.

CSF circulates through the ventricles and eventually drains into the venous circulation, so more needs to be produced all the time.

Question 32

The traces below show action potential recordings from nine different peripheral afferent fibres.
Which ONE of the following physical stimuli is most likely to have caused the observed pattern of activity?

Answer 32

An ice cube pressed gently against the skin.

An ice cube pressed gently against the skin would explain the cold and tactile afferent activity

Question 33

A person with normal vision except for anomalous trichromacy (red-green colourblindness):

Answer 33

sees purple as grey.

With normal vision, purple is red and blue together without green, whereas grey is red, green and blue all together. If your red and green sense is the same, then there is no distinction between purple and grey
for you.

Question 34

With regard to the organisation of somatosensory cortex:

Answer 34

The cortical representation of the hand is found near that of the face.

There is a disjunction in the topographic map here.

Question 35

Which ONE of the following statements about the structure of the brain is CORRECT?

Answer 35

Connections between cortical areas are made by white matter tracts

Cortical communication over any distance happens via bundles of axons called white matter tracts.

Question 36

Which of the following sensory parameters are topographically organised in their primary sensory cortex?

Answer 36

B

Topographically means ‘map-like’ and generally these
parameters will be organised like that in the periphery and in the primary sensory
cortex.

Question 37

When a neuron adapts to a stimulus, this means that it:

Answer 37

generates action potentials at a lower rate.

The response rate decreases over time, even though the stimulus is steady.