Nerves and Synapses

Question 1

What are the main regions of a neuron?

Answer 1

Cell body, dendrites, axon and axon terminal.

Question 2

How many neurons are there in the human nervous system?

Answer 2

More than 10^11

Question 3

What characteristic allows the nervous system to process information?

Answer 3

Neurons are arranged in neural networks.

Question 4

What are the three types of neurons?

Answer 4

Afferent, inter and efferent.

Question 5

What is the function of interneurons?

Answer 5

To integrate and store information

Question 6

What is the standard membrane potential at rest?

Answer 6

-70mV

Question 7

What causes the membrane potential?

Answer 7

Differences in ion distribution across the membrane and differences in permeability to ions.

Question 8

What causes the membrane potential to be negative at rest?

Answer 8

Potassium ions leaving the cells.

Question 9

What is responsible for the membrane potential?

Answer 9

Sodium and potassium ion receptors

Question 10

How are the inactivation and activation gate arranged at rest?

Answer 10

Inactivation gates open, activation gates closed so no ions can move.

Question 11

What does the activation potential result in?

Answer 11

A hyper shoot where the potential is less than the resting potential.

Question 12

How do invertebrates increase action potential speed?

Answer 12

By increasing fibre diameter

Question 13

What do vertebrate nervous systems use to increase action potential speed?

Answer 13

Myelination and saltatory conduction.

Question 14

What cells carry out myelination?

Answer 14

Schwann cells

Question 15

What are Nodes of Ranvier?

Answer 15

Gaps between areas of the axon surrounded by Schwann cells.

Question 16

What is saltatory conduction?

Answer 16

The action potential jumps from one node of Ranvier to the next.

Question 17

How does myelination increase speed?

Answer 17

It reduces the need for opening and closing channels.

Question 18

Where do neurons communicate with each other?

Answer 18

At synapses

Question 19

What are released at synapses?

Answer 19

Neurotransmitters

Question 20

What is a graded potential?

Answer 20

A small change in membrane potential either positive or negative.

Question 21

When will a graded potential become an action potential?

Answer 21

When depolarisation exceeds the threshold at the axon hillock.

Question 22

What causes a graded potential?

Answer 22

Release of a neurotransmitter.

Question 23

What is the inhibitory action at the post synaptic cell?

Answer 23

Hyperpolarisation

Question 24

What does spatial summation add up?

Answer 24

Simultaneous influences of simultaneous synapses at different sites on the post synaptic cell.

Question 25

What does temporal summation add up?

Answer 25

Post-synaptic potentials generated at the same time in rapid sequence.

Question 26

What is convergence of input?

Answer 26

When once cell is influenced by many others.

Question 27

What is divergence of output?

Answer 27

When one cell influences many others.

Question 28

What is the benefit of electrical signals?

Answer 28

They are faster than chemical signals.

Question 29

What is the benefit of chemical signalling?

Answer 29

It allows more control.