Structure and function of neurones

Question 1

What is the function of neurones

Answer 1

Once stimulus detected and its energy has been converted into depolarisation of the receptor cell membrane the impulse must be transmitted to other parts of the body.
impulse is transmitted along neurones as an action potential.
The action potential is carried as a rapid depolarisation of the membrane caused by an influx of sodium ions.

Question 2

What are the 3 different types of neurones?

Answer 2

Motor, sensory, relay.

Question 3

What are motor neurones?

Answer 3

neurones that carry action potential from the CNS to an effector such as a muscle or a gland.

Question 4

What are sensory neurones?

Answer 4

neurones that carry an action potential from a sensory receptor to the CNS.

Question 5

What are relay neurones?

Answer 5

neurones that connect sensory and motor neurones.

Question 6

Motor neurone structure

Answer 6

Cell body at the top of neurone
dendrites
long axon
axon surrounded by myelin sheath
node of ranvier- gaps in axon between the myelin sheath
direction of transmission- from cell body towards the axon

Question 7

Sensory neurone structure

Answer 7

synaptic ending at the top
in the CNS
then the short axon
cell body in the middle
long dendron
myelin sheath surrounding axon and dendron
then sensory receptor at bottom
direction of transmission: opposite to motor neurone from the sensory receptor up to the synaptic endings.

Question 8

relay neurone structure

Answer 8

small
cell body
dendrites
small axon
synaptic endings
Direction of transmission- same as motor neurone from top of neurone to bottom where synaptic endings are.

Question 9

Structure of neurones

Answer 9

• long- transmit action potential over a long distance
• plasma membrane has many gated ion channels- control the entry or exit of sodium, potassium or calcium ions.
• sodium/ potassium pumps use ATP to actively transport sodium ions out of the cell and potassium ions into the cell.
• neurones maintain a potential difference across their plasma membrane
• a cell body contains the nucleus, many mitochondria and ribososmes.
• dendrites connect to other neurones

Question 10

What does an axon do?

Answer 10

An axon carries impulses away from the cell body.
A- Away

Question 11

What do dendrites do?

Answer 11

Dendrites carry impulses towards the cell.
towarDs- Dendrites

Question 12

What is the myelin sheath

Answer 12

a fatty layer that insulates the cell from electrical activity in other nerve cell nearby.
It is composed of Schwann cells.

Question 13

Differentiating a motor neurone

Answer 13

they have their cell body in the CNS and have a long axon that carries action potential out to the effector.

Question 14

Differentiating a sensory neurone

Answer 14

have a long dendron carrying the action potential from a sensory receptor to the cell body- positioned just outside the CNS.
short axon carrying the action potential into the CNS.

Question 15

Differentiating the relay neurone

Answer 15

connect the sensory to the motor neurone
have many short dendrites, short axon

Question 16

What is the amount of peripheral neurones in vertebrates are myelinated neurones?

Answer 16

one third are myelinated- are insulated by an individual myelin sheath
rest of peripheral neuroes and neurones found in the CNS- non myelinayted

Question 17

Myelinated neurones

Answer 17

most sensory and motor have schwann cells- make up fatty sheath ( myelin sheath) it is tightly wrapped around the neurone.
at intervals of 1-3mm along the neurone there are gaps in the myelin sheath. - nodes of Ranvier
each node is very short

Question 18

What is the consequences of the myelin sheath being tightly wrapped around the neurone?

Answer 18

it prevents the movement of ions across the neurone membranes.
so movement of ions across the membrane can only occur in nodes of Ranvier, so impulse jumps from one node to the next.
Therefore, conduction is much more rapid.

Question 19

Non myelinated neurones

Answer 19

have schwann cells but many neourones may be covered in one loosely wrapped schwann cell.
This means the action potential moves along the neuropne in a wave rather than jumping from node to node- myelination.

Question 20

Advantages of myelination

Answer 20

Can transmit an action potential quicker than non myelinated neurones.
Myelinated neurones carry action potentials from sensory receptors to the CNS and from CNS to effectors.
Carry action potentials over long distances.