Membranes and Action Potentials

Question 1

The human nervous system is built out of two types of cells:

Answer 1

Neurons and glia

Question 2

A neuron is:

Answer 2

The functioning cellular unit of the nervous system specialised to receive, integrate and transmit information through electrical and chemical means.

Question 3

A glia is:

Answer 3

a non-neuronal cell in the nervous system that maintains homeostasis, forms myelin and provides support and protection for neurons.

Question 4

Four types of glial cells?

Answer 4

1. Myelin sheath- oligodendrocytes (CNS), Schwan cells (PNS)
2. Astrocytes- star-shaped cells part of the BBB
3. Microglia- take part in the immune system
4. Ependymal cells- production of CSF (cerebrospinal fluid) and neuroregeneration

Question 5

Dendrites are

Answer 5

the short, branching fibres extending from the soma that receive incoming information

Question 6

soma

Answer 6

cell body, contains nuceli, ribosomes etc

Question 7

soma

Answer 7

cell body, contains nuclei, ribosomes etc

Question 8

axon

Answer 8

singular fibre carrying info from soma to axon terminals

Question 9

Morphological classification of neurons:

Answer 9

1. Multipolar (most common)
2. Bipolar
3. Unipolar

Question 10

Passive movement of substances across cell membrane:

Answer 10

osmosis and diffusion according to concentration gradient

Question 11

Active movement of substances across cell membrane:

Answer 11

transporters and pumps move ions against their concentration gradient

Question 12

The membrane potential is determined by the relative fluxes of __________ through specific ion channels in the cell membrane.

Answer 12

Na+, K+, Cl-

Question 13

Excitation moves the resting membrane potential towards

Answer 13

0mV; depolarisation

Question 14

Inhibition makes the resting membrane potential more

Answer 14

negative; hyperpolarisation

Question 15

At rest, the concentration of K+ is higher or lower inside the cell? (compared to outside the cell)

Answer 15

Higher

Question 16

At rest, the concentration of Na+ is higher or lower inside the cell? (compared to outside the cell)

Answer 16

Lower

Question 17

The Na+/K+ pump maintains the electrical gradient. This means that it pumps out _____ and pumps in ______.

Answer 17

3Na+ ; 2K+

Question 18

The action potential begins with a channel opening for Na+ in the membrane. What happens next?

Answer 18

Driven primarily by the concentration gradient but also by the electrical gradient, Na+ rushes into the cell causing depolarisation.

Question 19

Na+ rushes into the cell causing depolarisation… and what does the membrane potential reach?

Answer 19

30mV !

Question 20

Once the membrane potential reaches 30mV, the voltage-gated potassium channels open. What next?

Answer 20

K+ leaves the cell, causing repolarisation. It overshoots a little, but the potassium channels finally close during the hyperpolarisation period.

Question 21

Absolute refractory period?

Answer 21

Another action potential will not start due to the inactivation gate of the voltage-gated Na+ channel.

Question 22

Relative refractory period?

Answer 22

A new action potential can be started but only by a stronger stimulus than the one that initiated the current action potential.

Question 23

An action potential is a

Answer 23

transient reversal of membrane potential due to influx of Na+ during the opening of voltage-gated Na+ channels.