IC2- CNS

Question 1

What is the difference between an afferent and efferent neuron?

Answer 1

Afferent: carries signal from periphery to CNS
Efferent: carries signal from CNS to periphery

Question 2

What is the name of a touch receptor?

Answer 2

Pacinian corpuscle

Question 3

Describe the nerve ending of the pacinian corpuscle and how the neuron is myelinated

Answer 3

• Enclosed nerve ending by layer of connective tissue
• Aβ myelinated

Question 4

What are the different types of myelination? What kind of receptors are they?

Answer 4

• Aβ (touch)
• Aδ (pain)
• C (pain)

Question 5

How does the myelination help in conduction of signal?

Rank the myelinations in terms of conduction speeds

Answer 5

More myelination → faster conduction

Speed: Aβ (thick myelin) > Aδ (thin myelin) > C (no myelin)

Question 6

Describe the nerve ending of afferent neurons (pain receptors)

Answer 6

Free nerve ending (selectivity conferred by TRPV1 receptor in membrane of nerve ending)

Question 7

Which tissue-damaging stimuli are the pain receptors activated by?

Answer 7

Pain receptors (afferent Aδ and C) are activated by tissue damaging stimuli: mechanical, thermal, chemical (ingredient of chilli/ capsaicin)

Question 8

What happens if there is loss of Aβ fiber (touch receptor)?

What happens to their pain sensation?

Answer 8

• Loss of non-pain sensation
• Pain sensation remains the same

Question 9

What happens if there’s a loss-of-function mutation in NTRK1 gene located on chromosome 1q21-22?

Answer 9

Absence of NGF (nerve growth factor)-dependent Aδ or C fibers → insensitivity to pain stimuli

Question 10

What is the postsynaptic target for an excitatory synapse?

Answer 10

Dendrite

Question 11

What is the postsynaptic target for an inhibitory synapse?

Answer 11

Soma (cell body)

Question 12

What happens during the upstroke of the action potential? (what channel is involved?)

Answer 12

First, threshold potential results in opening of a class of channels in membrane = voltage gated Na+ channel

When the action potential reaches the axon terminal, it opens the voltage-gated Ca2+ channels → Ca2+ influx → causes vesicles containing neurotransmitter to fuse with presynaptic membrane and exocytosis

Question 13

What happens during the upstroke of the action potential? (what channel is involved?)

Answer 13

• Inactivation of voltage gated Na+ channel
• Opening of voltage gated K+ channel causing K+ efflux → RMP restored

Question 14

In hypokalemia, there is a severe decrease in serum K+. What happens to the excitable membrane?

Answer 14

Hyperpolarisation as the concentration gradient favours movement of K+ from intracellular → extracellular; cell less excitable

Question 15

What are the limbic structures in the brain? (ie. structures largely responsible for regulating emotions)

Answer 15

Hippocampus and amygdala

Question 16

Which part of the brain is associated with consciousness?

Answer 16

Cortex

Question 17

What are the functions of the cortex?

Answer 17

• Sensation and perception (both cortices)
• Voluntary control of movement
• Personality traits (frontal lobes)
• Learning and memory
• Language

Question 18

What could damage to the Broca’s area (left hemisphere) result in?

Answer 18

Damage lead to difficulties in expressing language

Question 19

What could damage to the Wernicke’s area (left hemisphere) result in?

Answer 19

Damage leads to difficulty in comprehending language

Question 20

What is the term used to describe the symptom of difficulty in producing or comprehending speech due to damage in the Broca/ Wernicke’s area?

Answer 20

Aphasia

Question 21

Which region of the brain is correlated with depression?

Elaborate

Answer 21

A region in the prefrontal cortex, the ‘Subgenual Anterior Cingulate Cortex’ or ‘Subgenual ACC

Depression is correlated with increased activity (hyperactivity) of Subgenual ACC

Question 22

What is a type of Tx that can decrease depression?

Answer 22

Deep brain (electrical) stimulation to decrease activity in Subgenual ACC

Question 23

Which part of the brain is associated with cognition (learning and memory), emotion, mood?

Answer 23

Both cortical and sub-cortical regions

Question 24

What is the hippocampus associated with? What happens if there is a lesion/ neurodegeneration of cells in the hippocampus?

What disease is implicated?

Answer 24

Associated with declarative memory that involves conscious recall; e.g., memory of events, names, numbers etc

Alzheimer’s disease

Question 25

What is the amygdala associated with? What happens if there is damage to the amygdala?

Answer 25

Amygdala = emotion and emotional memory, important for mood changes

Lost ability to recognize facial expression of emotion