Biology unit 1 signals

Question 1

What is the nervous system made of?

Answer 1

peripheral nervous system and the central nervous system.

Question 2

What is the central nervous system made of?

Answer 2

Brain and spinal cord.

Question 3

What are neurones?

Answer 3

Neurones are cells that carry electrical signals, or nerve impulses ,from one part of the body to the other.

Question 4

What does dendrites do in a nerve cell?

Answer 4

Dendrites recieve chemical signals from the axon terminal of other neurons.

Question 5

What does the node of ranvier do?

Answer 5

The node of ranvier allows the electrical impulse to pick up speed.

Question 6

What is the axon made of ?

Answer 6

Mylelin sheath and schwann cell. Mylin sheath is electriciyt insulating layer and the schwann cell produces the mylin sheath.

Question 7

What does a schwann cell do in a nerve cell?

Answer 7

Produces the mylin sheath.

Question 8

What does node of ranveer do?

Answer 8

Allows the electrical signal to pick up.

Question 9

What are features of non-myelinated nerve cell?

Answer 9

They have a small diameter, no mylin sheath, grey, slow impulse, no rodes of ranveer and transmits aches, soreness and temperature changes.

Question 10

What are features of myelinated nerve cells?

Answer 10

Large diameter, mylin sheath,white,fast impulses, nodes of ranvier, and sharp pain.

Question 11

What are the three neurones and what do they do?

Answer 11

Sensory neuron-they carry a signal from the receptors to the cns. Motor neuron-carry signal from cns to effector. Relay neuron-found in the cns.

Question 12

What makes the voltage changes when a signal passes through a membrane?

Answer 12

The gates which open and close.

Question 13

How can sodium and potassium ions move through the membrane?

Answer 13

Some gates open all the time so these ions can move through diffusion and some gates which can be open and closed. And there are pumps which make them move.

Question 14

What is depolarisation and what happens?

Answer 14

An electrical charge within a neuron from a negative charge to a positive charge and it occurs when the voltage goes from -70mv which is the resting potential to 30mv. This happens because more sodium comes in as the sodium gates open and so makes it more positive and potassium stays the same does not go in or out as potassium gates stay close.

Question 15

What do sodium and potassium channels depend on?

Answer 15

They depend on diffusion.

Question 16

What does it mean if the gate is voltage gated?

Answer 16

The gate will open when the voltage becomes a certain value.

Question 17

What happens step by step in the action potential when a signal moves across a membrane?

Answer 17

A stimulus comes and opens the sodium channels. This causes the sodium to diffuse in and so potential difference starts to rise from -70mv. When and if the volateg reaches -50mv threshold occures this causes the voltage gated sodium channels to open and so lots of sodium ions starts to move in and so the voltage rises rapidly from 30 mv and potassium gates open and also come into the cell. Then the sodium gates close and potassium gates open then sodium ions move out and potassium ions move out and this causes the voltage to decrease to -90mv. Then the sodium and potassium pump does its job and returns the potential difference back to resting potential–70mv it does this as sodium ions move out and potassium ions move in.

Question 18

What is repolarisation?

Answer 18

When potassium ions and sodium ions move out and potential difference is -90mv.

Question 19

What is hyperpolarisation?

Answer 19

When potential difference returns to resting potential and sodium is moved out and potassium moves in and so potential difference is -70mv.

Question 20

Why does action potential travel faste r in myelinated neurones?

Answer 20

Because myelinated has a mylin sheah which is an insulator and stops sodium ions moving in which prevents depolarisation and so signal travels from gap to gap instead which causes saltatory conduction which means leaping.