Neurons

Question 1

What are dendrites?

Answer 1

The short processes emanating from the cell body which receive most of the synaptic contacts from other neurons.

Question 2

What is an axon?

Answer 2

the long narrow process that projects from the cell body

Question 3

What is an axon hillock?

Answer 3

the cone shaped region at the junction between axon and cell body

Question 4

What is the cell body?

Answer 4

The metabolic centre of the neuron, also called the soma

Question 5

What is myelin?

Answer 5

The fatty insulation around many axons

Question 6

What are the nodes of Ranivier ?

Answer 6

The gaps between the section of myelin

Question 7

What are terminal buttons?

Answer 7

The button like endings of axon branches which release chemical signals into synapses .

Question 8

What are synapses?

Answer 8

The gaps between adjacent neurons across which chemicals signals are transmitted .

Question 9

How do neurons work?

Answer 9

1. Electrical potential in axon hillock becomes more positive, triggering electrical impulse .
2. Action potential travels across synapse to receptors on dendrites of receiving neurons .
3. Neurotransmitter causes either excitatory or inhibitory potential in receiving neuron .
4. If sum of excitatory is large enough then another action potential is created .

Question 10

What is the cell membrane?

Answer 10

A lipid (fatty) bilayer, with ion channels embedded in it .

Question 11

What happens at resting potential?

Answer 11

The outside of the cell has higher concentration of sodium

The inside of the cell has higher concentration of potassium

The outside is positively charged compared to the inside

Question 12

How is resting potential maintained ?

Answer 12

By a sodium pump which transports sodium out of the neuron and potassium into the neuron .

Question 13

What happens at action potential?

Answer 13

• The inside of the membrane becomes more positively charged and triggers opening of sodium channels .
• Positive sodium ions rush into the axon, causing it to be much more positive (depolarisation)
• potassium channels open allowing positive ions to flow out
• sodium channels close and potassium ion outflow reduces the electric potential back to resting potential .
• Depolarisation at one place in the axon triggers the opening of adjacent sodium channels, causing the action potential to propagate down the axon .

Question 14

What happens if the axon has a myelin sheath?

Answer 14

depolarisation jumps between gaps in the myelin (nodes of Ranvier) which speeds up transmission greatly.

Question 15

What is depolarisation?

Answer 15

When Positive sodium ions rush into the axon, causing it to be much more positive

Question 16

What happens at the release of neurotransmitter?

Answer 16

Ø Exocytosis- the process of neurotransmitter release
Ø The arrival of an AP at the terminal opens voltage activated calcium channels
Ø The entry of calcium causes vesicles to fuse with terminal membrane and release their contents

Question 17

What happens at receptors?

Answer 17

Some neurotransmitter molecules bind to receptors on ion channels - when a neurotransmitter molecule binds to an ionotropic receptor, the channel opens or closes, thereby altering the flow of ions into or out of the neuron.