Action Potential

Question 1

What is the function of the dendrite?

Answer 1

Receives signals from other neurons/sensory receptor cells and activates action potential
- shoots electrical charge down axon

Question 2

What is the function of the myelin sheath?

Answer 2

Insulates the axon so impulses travel faster

Question 3

Where is the sensory neuron found?

Answer 3

In receptors e.g. eyes

Question 4

What do sensory neurons do?

Answer 4

• Carry nerve impulses to the spinal chord and the brain

- These impulses are translated into ‘sensations’ when they reach the brain e.g. vision

Question 5

What is the axon?

Answer 5

Long nerve fibre that carries nerve impulses in the form of an electrical signal known as action potential

Question 6

What do motor neurons do?

Answer 6

• in CNS

- Control muscle movements

Question 7

What happens when a motor neuron is stimulated?

Answer 7

• neurotransmitters are released
• they bind to receptors on muscles
• triggers response (movement)

Question 8

What is the axon terminal?

Answer 8

Connects neuron to other neurons

Question 9

When do neurons transmit signals?

Answer 9

• when stimulated by sensory input

- when triggered by neighbouring neurons

Question 10

What are synapses?

Answer 10

‘Contact points’

Question 11

What are the chemical messengers that are activated when AP runs down to the end of the axon?

Answer 11

Neurotransmitters

Question 12

What are excitatory neurotransmitters?

Answer 12

Increased chance of AP

Question 13

What are inhibitory neurotransmitters?

Answer 13

Decreased chance of AP

Question 14

Why do we need membranes within the body?

Answer 14

• body is electrically neural, but some parts are more + or - than others
• as opposite charges attract, we need membranes to keep + and - separate till we can use the energy their attraction creates

Question 15

In what way do neurons send messages?

Answer 15

Electrochemically

Question 16

What charge does potassium sodium, calcium and chloride have?

Answer 16

• potassium = +
• sodium = +
• calcium = ++
• Chloride = -

Question 17

What are the nerve cells surrounded by?

Answer 17

A semi permeable membrane that allows some ions in and blocks others

Question 18

What is resting membrane potential?

Answer 18

When a neuron is not sending a signal, it is at rest and has a negative charge in comparison to the outside

Question 19

What does the pump do?

Answer 19

Uses energy to move 3x sodium out for every 3x potassium in

Question 20

What is the resting potential?

Answer 20

Difference in forces inside and outside

- is usually -65mV as at rest, a neuron has more positive ions outside

Question 21

What does polarised mean?

Answer 21

When there is negative membrane potential

Question 22

When does AP occur?

Answer 22

When a neuron sends info down an axon (away from a cell body) when some event causes the resting potential RP Mv to move toward 0Mv

Question 23

What is AP?

Answer 23

Electrical activity created by a depolarising current

Question 24

What happens when depolarization reaches -55Mv?

Answer 24

• ‘threshold’ level

- neuron will fire an action potential

Question 25

Why are AP’s described as all or nothing events?

Answer 25

For any given neuron the size of the AP is always the same

Question 26

What does the neuronal membrane do?

Answer 26

Separates the charges and provides the potential to convert electricity into something useful

Question 27

What is intracellular fluid?

Answer 27

Fluid in cell

Question 28

What is extracellular fluid?

Answer 28

Fluid outside the cell

Question 29

What causes electrical signals?

Answer 29

Movement of ions across the neuronal membrane

Question 30

What 2 forces determine the movement of ions into and out of the cell?

Answer 30

1. Concentration (high to low)

2. Electrical (negative and positive)

Question 31

What do ion channels do?

Answer 31

Only allow specific ions to move through the neuronal membrane
- different ions have different ion channels

Question 32

What happens to sodium ions channels at rest?

Answer 32

They are closed

Question 33

Why is K+ attracted to the cell?

Answer 33

Because the cell is more negative inside compared to the outside (electrical force)

Question 34

Why is K+ attracted out of the cell?

Answer 34

Because there is less potassium outside the cell (concentration force)

Question 35

What 2 forces are in equilibrium in regard to the movement of K+?

Answer 35

Concentration force and Electrical force

Question 36

What is the function of the Na+ K+ pump?

Answer 36

Causes the charge imbalance by continually pumping 3x sodium out for every 2x potassium in

• causes increased K+ conc. inside
• increased Na+ conc outside

Question 37

What happens to the equilibrium when a neuron is stimulated?

Answer 37

The equilibrium is upset and if the stimulation is large enough (above the -50 threshold), the resting potential becomes an action potential

Question 38

What happens when a cell is stimulated above threshold?

Answer 38

Sodium channels open

Question 39

Why is sodium attracted into the cell?

Answer 39

• There is more Na+ outside than inside (concentration force)
• The cell is negatively charged (electrical force)

Question 40

What type of ion channel is a potassium ion channel?

Answer 40

Voltage gated

Question 41

What is myelin produced by?

Answer 41

Glial cells

Question 42

Why do myelinated axons conduct APs faster?

Answer 42

Saltatory conduction

Question 43

What is the strength of the stimulus denoted by?

Answer 43

Increasing firing rate

- the no. Of AP’s denotes the force of the stimulus

Question 44

What happens when the AP reaches the presynaptic terminal?

Answer 44

A chemical (neurotransmitter) is released into the junction between the neurons (synapse)

Question 45

What is shown about excitatory and inhibitory signals in epilepsy?

Answer 45

The correct balance of EPSP and IPSP signals is necessary for the proper working of the nervous system
- Epilepsy results in neurons becoming too active, resulting in uncontrollable patterns of electrical activity (seizures)