Topic 8 Nervous system

Question 1

Describe the roles of:
-Schwann cells
- Axon
- Dendrites
- Nodes of ranvier
- Cell body

Answer 1

Schwann cells: Acts as insulation to prevent loss of charge
Axon: Long transport chain to allow ion transport.
Dendrites: Receive chemical signal from synapse.
Nodes of Ranvier: Speeds up conduction
Cell body: Contains neurons

Question 2

State the order of events in a typical reflex arc

Answer 2

Receptor —> Sensory neurone —> CNS —> relay neurone —> motor neurone —> effector.

Question 3

Describe the structure of a sensory neuron

Answer 3

Receptor cell connected to dendron with myolin sheath around the outside, Main cell body attached to dendron in centre, axon branches off with axon terminals at the end of axon.

Question 4

Describe the structure of a relay neuron

Answer 4

Highly branched Dendrites connected to main cell body, main cell body connected to axon, axon connected to axon terminals.

Question 5

Describe the structure of a motor neuron

Answer 5

Cell body w/ dendrites connected to axon, axon wrapped by shwann cells with nodes of ranvier (gaps) between each cell, forms myelin sheath, axon connected to axon terminals.

Question 6

Describe the role of schwann cells in/ myelin sheath.

Answer 6

Insulation to prevent charge from being transferred to surrounding tissue.

Question 7

Describe the role of the axon

Answer 7

Wave of depolarization travels through it to send a signal from the dendrites to the axon terminals.

Question 8

Describe the role of dendrites

Answer 8

Receive chemical stimulus to trigger wave of depolarisation through axon.

Question 9

Describe the role of the nodes of ranvier

Answer 9

Allow for propagation of an action potential due to their many ion transport channels.

Question 10

What is the resting potential of the membrane around the neuron

Answer 10

-70mV

Question 11

Describe resting potential.

Answer 11

Sodium ions outside of axon, Potassium ions inside axon. Sodium ion channel gates closed, Potassium ion channel gates closed. -70mV charge inside axon.

Question 12

Describe depolarisation

Answer 12

Stimulus causes some Sodium ion channel gates to open, Sodium ions travel from outside to inside of cell, causing a change in charge. once -55mV charge inside axon reached, many voltage gated sodium ion channel gates open causing a flood of sodium ions into the cell, which results in the depolarisation of the cell membrane.

Question 13

Describe repolarisation.

Answer 13

Positively charged axon causes voltage gated potassium ion channel gates to open, causing potassium ions to diffuse out of the cell which repolarises the axon cell membrane.

Question 14

Describe hyperpolarisation

Answer 14

After repolarisation, Potassium ion channel gates remain open which causes more potassium ions to travel out of the cell, causing the outside of the cell to be hyperpolarised due to having many more potassium ions.

Question 15

What is the neurotransmitter problem that causes parkinsons

Answer 15

Lack of dopamine

Question 16

Explain how L dopa works to treat the symptoms of parkinsons

Answer 16

can cross the bloodstream - brain barrier and gets converted to dopamine

Question 17

State the neurotransmitter problem that causes depression

Answer 17

Lack of serotonin

Question 18

Explain how SSRI’s can be used ti treat depression

Answer 18

Prevent reuptake of serotonin from synaptic cleft, therefore more serotonin present in synaptic cleft so more serotonin binds to receptors

Question 19

Explain the action of MDMA at the synapses

Answer 19

Increases rate of release of serotonin from presynaptic nerve, reduces reuptake of serotonin