THE CENTRAL NERVOUS SYSTEM

Question 1

What does the brain do?

Answer 1

The brain determines out behaviour, coordinating sensory input and previous experience. Behaviour reflects brain function.

Question 2

What are the regions of the CNS?

Answer 2

Forebrain
Midbrain
Hindbrain
Spinal Cord
Brainstem

Question 3

What makes up the forebrain?

Answer 3

The cerebrum, a central core and diencephalon

Question 4

Describe the midbrain?

Answer 4

It is the smallest part of the brain.

Question 5

What makes up the hindbrain?

Answer 5

The pons, the medulla anteriorly and the cerebellum posteriorly.

Question 6

What makes up the brainstem?

Answer 6

The midbrain, the pons and the medulla

Question 7

What is the function of the somatosensory cortex?

Answer 7

Responsible for receiving sensory input from all parts of the body.

Question 8

How does the somatosensory cortex work?

Answer 8

Each neuron takes its information to a specific place in the somatosensory cortex. Then the somatosensory cortex works out what the information means.

Question 9

What is the function of the motor cortex?

Answer 9

It is the part of the cerebral cortex where voluntary movements are planned, controlled and executed. It controls movement rather than the activation of single muscles.

Question 10

What is a synapse?

Answer 10

A specialised junction where neurones make connections

Question 11

How does communication across a synapse work?

Answer 11

Involves a release of a chemical messenger ‘neurotransmitter’ from the pre-synaptic terminal. The neurotransmitter binds to receptorsin the post-synaptic membrane and elicits an electrical signal (post synaptic potential) in the neurone.

Question 12

What are the steps for communication across a synapse?

Answer 12

1. Action potential reaches axon terminal and depolarises membrane
2. Voltage gated Ca2+ channels open and Ca2+ flows in
3. Ca2+ influx triggers synaptic vesicles to move to membrane and release neurotransmitters.
4. Neurotransmitter diffuses across the synaptic cleft and binds to receptors on the target (postsynaptic) cell

Question 13

How does a cell become depolarised?

Answer 13

A neurone is bombarded with stimuli that changes its membrane permeability. If the changed permeability allows more cations to enter a neuron its membrane potential decreases (becomes less negative) and the cell is depolarised.

Question 14

How does a cell become hyperpolarised?

Answer 14

A neuron is bombarded with stimuli that changes its membrane permeability. If the changed permeability results in an efflux of positive charges of entry of negative charges, the membrane potential increases (becomes more negative) and the cell is hyperpolarised

Question 15

How does a neuron regain its resting membrane potential?

Answer 15

After the cell is depolarised/hyperpolarised the ions redistribute across membrane depending on equilibrium potentials and permeabilities. The flow of charges stops and the membrane potential returns to the resting value.

Question 16

What are the steps in an action potential?

Answer 16

1. Stimulus starts the rapid change in voltage or action potential.
2. Depolarization is caused by a rapid rise in membrane potential opening of sodium channels in the cellular membrane, resulting in a large influx of sodium ions.
3. Membrane Repolarization results from rapid sodium channel inactivation as well as a large efflux of potassium ions resulting from activated potassium channels.
4. Hyperpolarization is a lowered membrane potential caused by the efflux of potassium ions and closing of the potassium channels.
5. Resting state is when membrane potential returns to the resting voltage that occurred before the stimulus occurred.