Neuronal communication

Question 1

What are neurones?

Answer 1

They are specialised cells that transmit action potentials (impulses).

Question 2

Structure of a neurone

Answer 2

• Dendron/ite
• Axon
• Myelin sheath
• Axon terminal
• Schwann cell
• Cell body
• Nucleus
• Nodes of ranvier

long to transmit signals over large distances

Question 3

Dendron

Answer 3

Sends impulses to the cell body (from stimuli direction)

Question 4

Cell body

neurone

Answer 4

does alot but can release neurotransmitters

Question 5

Axon

Answer 5

Sends impulses away from the cell body (in the effector direction)

Question 6

Myelin sheath

Answer 6

layers of plasma membranes (lipids)
insulates the neurone to speed the rate of transmission. produced by Schwann cells.

Question 7

Schwann cells

Answer 7

Cells that produce the myelin sheath

Question 8

Nodes of ranvier

Answer 8

Gaps on the neurone not covered by the myelin sheath

Question 9

Sensory neurone
Structure

Answer 9

Have a long dendron and short axon

Question 10

Motor neurone

Answer 10

Cell body in the CNS. Long axon and short dendrites.

Question 11

Relay neurone

Answer 11

Cell body in the middle. Short dendrites and axons

Question 12

What are myelinated neurons and where are they found?

Answer 12

• Neurones that have a myelin sheath.
• Control muscle movement
• Found in peripheral neurones

Question 13

What is transmission like in myelinated neurones?

Answer 13

• Fast
• Action potential moves from node-to-node
• Ion movement occurs at Nodes of Ranvier

Question 14

What are non-myelinated neurons and where are they found?

Answer 14

• Neurones w/o a myelin sheath
• Control breathing and digestive system
• Found in the CNS

Question 15

What is transmission like in non-myelinated neurones?

Answer 15

• Slow(er)
• Action potentials move as a wave

Question 16

What are sensory receptors?

Answer 16

Cells that are specialised to detect changes in our environment
* they are energy transducers (generator potential)
* specific to one type of stimulus

Question 17

Habituation

Answer 17

When receptors don’t respond to constant stimulus

Question 18

What is an action potential?

Answer 18

An action potential is the state of a neurone in which the inside of its axon reaches its maximum positive charge.

Question 19

What is hyperpolarisation?

Answer 19

Hyperpolarisation is the state of a neurone in which the inside of an axon reaches its minimum positive charge.

Question 20

What is a Pacinian corpuscle?

Answer 20

It is a sensory receptor in the skin which detects mechanical pressure and acts as a transducer converting it to chemical energy.

Question 21

What is a resting potential?

Answer 21

The potential of the membrane when there is no action potential.

Question 22

What is spatial summation?

Answer 22

It is where many presynaptic neurones connected to 1 postsynaptic neurone.

Question 23

What is temporal summation?

Answer 23

Action potentials triggered many times over a short period from the presynaptic neurone.

Question 24

What are the different neurotransmitter types?

Answer 24

• Excitatory
• Inhibitory

Question 25

What are Excitatory neurotransmitters?

Answer 25

If the threshold for neurotransmitter is reached then depolarisation will take place.

Question 26

What are inhibitory neurotransmitters?

Answer 26

They prevent action potentials by causing hyperpolarisation.

Question 27

What are some effects of drugs on neurotransmitters?

Answer 27

* they can block receptors * They can mimic the shape of the neurotransmitter. * They can stimulate the release of more neurotransmitters * They can inhibit the enzyme that breaks down neurotransmitters.

Question 28

What is the All-or-nothing principle?

Answer 28

The stimulus must reach threshold value in order to trigger an action potential.

Question 29

What factors affect the speed of an action potential?

Answer 29

* axon diameter => bigger=faster * temperature=> higher temp= faster

Question 30

What is saltatory conduction?

Answer 30

Where action potentials jumps from one node to another in myelinated neurones.

Question 31

What is the refractory period?

Answer 31

The period of time when an action potential can’t be triggered. * ensures that action potentials are unidirectional * ensures action potentials don’t overlap.

Question 32

How does a sodium-potassium pump work ?

Answer 32

It pumps 3 sodium ions out of the axon membrane and 2 potassium ions into the axon membrane.

Question 33

How does a voltage-gated Na+ work?

Answer 33

When a voltage of -55mV is reached (an action potential) the channels open.

Question 34

How does a voltage-gated K+ work?

Answer 34

When a voltage more positive than is reached the channels open.