Nerves

Question 1

What are the receptors in the muscles and the nose?

Answer 1

Proprioceptors

Olfactory cells

Question 2

How is a resting potential kept?

Answer 2

Voltage gated Na+ ion channels are closed
The Sodium / pottassium pump uses ATP to pump Na+ out of the cell
The inside of the cell is more negative than the outside
So the membrane is polarised
So a -60mV resting potential is produced

Question 3

Explain how the cell membrane of a neurone can create an action potential

Answer 3

Gated Na+ ion channels open
Na+ flow into the cell down concentration gradient
Membrane becomes depolarised
Voltage-gate (Na+) channels open due to the depolarisation
The inside of the membrane becomes more +ve than the outside ( = +40mV)

Question 4

Explain what repolarisation / hyperpolarisation is, and how they occur

Answer 4

Gated Na+ ion channels shut, but the K+ channels open
Pottassium ions diffuse out of the cell
So the potential difference returns to -60mV
The potential difference overshoots slighltly during hyperpolarisation to just over -60mV before returningback

Question 5

Explain how closed Na+ ion channels can be opened to create a current, from an action potential

Answer 5

The sodium ions that have been diffused into the inside of the cell travel down the dendron / axon away from the region of higher concentration
This movement of ions cause the closed Na+ channels to open
So another action potential can be created
So a current is formed

Question 6

What is the insulation of a neurone?

Answer 6

The mylelin sheath

Question 7

What type of cells produce the myelin sheath?

Answer 7

Schwann cells

Question 8

In which direction does an axon carry an impulse?

Answer 8

Away from the cell body

Question 9

What are the two key differences between a sensory and motor neurone

Answer 9

Motor neurones cell body is much bigger

Direction of transmission is different

Question 10

What type of ion channels open at the synaptic knob, and what is diffused into the synaptic knob as a result?

Answer 10

Voltage gated calcium ions

Ca2+ ions

Question 11

Explain how the presence of Calcium ions in the synpatic knob causes a new action potential to be produced in the synaptic cleft

Answer 11

Ca2+ ions causes vesicles containing Ach to fuse with the membrane of the synaptic knob, and leave via exocytosis
The Ach leaves the vesicles and bind with recepters on the Na+ channels on the post synpatic membrane
These channels open and Na+ enter the post synpatic membrane
This creates a generator potential (EPSP), which if enough are present, creates a new action potential

Question 12

What happens to Ach after it is used?

Answer 12

Broken down by acetylcholinesterase to ethanoic acid and choline
These re-enter the synaptic knob to form more Ach
This breakdown stops the transmisison across the synapse

Question 13

Define summation

Answer 13

Several small potential changes can combine to produce one larger change

Question 14

Define acclimitisation

Answer 14

Repeat stimulation causes the synaptic knob to run out vesicles containing Ach, and so transmission across a synapse stops

Question 15

What does a stimulus of a greater intensity result in?

Answer 15

A greater frequancy of generator potentails, and so action potentials

Question 16

True of false? Non myelinated neurons carry signals over a short distance?

Answer 16

True

Question 17

Define the all-or-nothing law

Answer 17

An action potential is either formed fully or not at all, regardless of the strength of the stimulus