Neurophysiology

Question 1

State the 4 components of a neuron

Answer 1

1. Cell body (Soma)
2. Dendrites
3. Axons
4. Presynaptic terminals

Question 2

Define multipolar neurons

Answer 2

Neurons with single axons and 1>= dendritic branches that emerge from all parts of the cell body

Question 3

Define resting membrane potential

Answer 3

The differential distribution of ions across the membrane of nerve cells and muscles as a result of the inside of the membrane being more negative (-75mV) compared to the outside.

Question 4

State the ions that have a higher concentration in the intracellular and extracellular environment respectively

Answer 4

Intracellular:
- K+ (135mM vs 3mM)
Extracellular:
- Na (145mM vs 18)
- Cl (120mM vs 7)
- Ca (1.2mM vs 100nM)

Question 5

Intracellular K+ is higher compared to extracellular K+. List 2 forces that forms the electrochemical gradient acting on K+

Answer 5

1) Concentration gradient that favours efflux of K+ from inside to the outside of the membrane
2) Electric gradient that hold/pulls charged K to the inside (since inside is relative -ve compared to outside)

Question 6

Define equilibrium potential of an ion

Answer 6

The potential at which the outward and inward gradients acting on the ion balance out and there is no net movement of the ion across the membrane

Question 7

State the formula to calculate the equilibrium potential for K

Answer 7

E = 58log(Kout / Kin)

Question 8

State the effects if extracellular K is increased from eg. 3mM to -50mM

Answer 8

1) Concentration gradient is less steep
2) Greater accumulation of positive charges on inside of membrane
3) Membrane will depolarise to new value from starting resting potential of -80/-60mV

Question 9

Which channels control the refractory period?

Answer 9

Inactivation of Na channels and opening of K channels

Question 10

Define afferent and efferent neurons

Answer 10

Afferent: Signal carried from periphery to CNS
Efferent: Signal from CNS to periphery

Question 11

List 4 examples of afferent neurons

Answer 11

1. Pacinian corpuscle
2. Abeta myelinated fibre
3. Adelta myelinated fibre
4. C fibre

Question 12

What type of sensory information is carried by Abeta, Adelta and C fibres?

Answer 12

1. Abeta: touch (nonpainful experience)
2. Adelta & C-fibre: Pain

Question 13

Describe how an action potential is generated

Answer 13

1. Depolarisation
2. Depolarisation to threshhold
3. Upstroke: Opening of voltage gated Na channels
4. Downstroke: Inactivation of voltage gated Na channel, opening of voltage gated K channel
5. Repolarisation to RMP

Question 14

Hypokalemia will lead to the following chnages in excitable membrane:

1) Hyperpolarisation of membrane
2) Depolarisation of membrane
3) Inactivation of voltage gated Na Channels
4) Opening of volatge gated K channel

Answer 14

Ans: 1). In hypokalemia, lower K+ outside relative to inside. This favors mmovement of K+ out of the cell. RMP hyperpolarises to blance out K+.

3) VG Na channels only open when treshhold AP is reached. Hence, hyperpolarisation will not affect this.
4) VG K+ channels only open towards peak of AP, not affected by hyperpolarisation

Question 15

List 2 structures in the brain belo the limbic system

Answer 15

1) Hippocampus
2) Amygdala

Question 16

State the roles that the cortex is involved in

Answer 16

Cortex plays a role in all functions

1. Sensation & perception (both cortices)
2. Voluntary control of movement
3. Personality traits (frontal lobes)
4. Learning and memory
5. Language

Question 17

Damage to the Broca’s area lead to?

Answer 17

Difficulties in expressing language

Question 18

Damage in the Wernicke’s area leads to?

Answer 18

Difficulty in comprehending language

Question 19

Define Aphasia

Answer 19

Difficulty in producing/comprehening speech not caused by hearing or motor distrubances.

Question 20

State condition(s) that cause aphasia

Answer 20

Damage to Broca’s area and/or Wernicke’s area (affect written & spoken langugage)

Question 21

T/F: Broca’s area and Wernicke’s area are both found in the right hemisphere.

Answer 21

False. Both are found in the left hemisphere

Question 22

Which area of the brain is implicated in the development of depression?

Answer 22

Subgenual Anterior Cinguate Cortex (ACC). Increase in Subgenual ACC lead correlated with depression

Question 23

State the function of the Hippocampus

Answer 23

Involved in Declarative memory, defined as memory that involves recall eg. no. of events, names, numbers

Question 24

List a few examples of non-declarative memory

Answer 24

Memory that involves non-conscious recall eg. riding bike or swimming

Question 25

Explain how the Amygdala plays a role in mood changes

Answer 25

Important for emotion & emotional memory - eg. damage causes loss of ability to recognise facial expression of emotion, fail to identify fear in facial expression