Nervous Coordination

Question 1

Sensory neurones

Answer 1

Carry nervous impulses from receptors into the central nervous systems

Question 2

Motor neurones

Answer 2

Carry impulses from the CNS to effecter organs

Question 3

Relay neurones

Answer 3

Intermediate neurones which receive impulses from a sensory neurone and relay them to motor neurones

Question 4

Dendrites

Answer 4

Carries nervous impulses towards a cell body

Question 5

Axons

Answer 5

Carries nervous impulses away from the cell body

Question 6

Cell body

Answer 6

Where the nucleus is normally located

Question 7

Myelinated motor neurones

Answer 7

Schwann cells are wrapped around the axon of the neurone which form the myelin sheath
Gaps between the adjacent Schwann cells are called nodes of ranvier

Question 8

Resting potential

Answer 8

At resting state the inside of the neurone is more negatively charged than the outside because there are more positive ions outside the cell
About -70mV

Question 9

How is the resting potential maintains

Answer 9

By sodium-potassium pumps in the neurone membrane : three Na+ ions are actively transported out of the neurone for every two K+ ions that are transported in which leads to a build up of positive ions outside the cell

Question 10

Stimulation

Answer 10

Na+ ion channels in cell membrane open when a neurone is stimulated so sodium ions flood into the neurone which causes the potential difference across the membrane to become more positive inside the neurone

Question 11

Depolarisation

Answer 11

If the potential difference increases above the threshold value (about -55mV) then the membrane will become depolarised so more sodium channels open and there is a sharp increase in the potential difference to about +30mV

Question 12

All or nothing response

Answer 12

If the potential difference reaches the threshold, depolarisation will always take place and the change in potential difference will always be the same. If the stimulus is stronger, action potentials will be produced more frequently, but their size will not increase

Question 13

Repolarisation

Answer 13

After the neurone membrane has depolarised to +30mV the sodium ion channels close and potassium ion channels open
Na+ ions are transported back out of the neurone and the potential difference becomes more negated

Question 14

Hyper polarisation

Answer 14

Short period after depolarisation of a neurone where the potential difference becomes slightly more negative than the resting potential which prevents the neurone from being restimulated instantly = refractory periods

Question 15

How do action potentials move along the neurone

Answer 15

When an action potential is generated , there are more Na+ ions inside the neurone than outside. Some of these Na+ ions diffuse sideways along the neurone axon which creates a change in the potential difference further along the neurone membrane and if this reaches the threshold value, sodium ions channels at this part of the membrane open which creates a wave of depolarisation

Question 16

How does myelination speed up transmission of nerve impulses

Answer 16

Schwann cells wrap around the axon of neurones to create a myelin sheath which acts as an electrical insulator because it is impermeable to ions.
Depolarisation and action potentials cannot occur at the myelinated parts of the axon and can only occur in the gaps between. The nervous impulse jumps from one node to the next = saltatory conduction

Question 17

How does temperature speed up transmission

Answer 17

Increase in temperature increase kinetic energy so ions move across the membrane more rapidly when they have more kinetic energy

Question 18

Axon diameter

Answer 18

Greater surface area for the movement ions across the cell membrane

Question 19

Synapse

Answer 19

Junction between two neurones or between a neurone and an effector

Question 20

Synaptic cleft

Answer 20

At a synapse, there is a gap between the cells . When an action potential reaches a synapse, it. Must be transmitted across the synaptic cleft

Question 21

Presynaptic neurone

Answer 21

Neurone before the synapse, when an action potential reaches the end of the neurone, it is transmitted across the presynaptic membrane to the postsynaptic membrane or to an effector cell

Question 22

Synaptic knob

Answer 22

Swelling which contains synaptic vesicles where the nerve impulse is transmitted across the synaptic cleft
Lots of mitochondria needed to synthesise neurotransmitters

Question 23

Synaptic vesicles

Answer 23

Located in the synaptic knob

Contain neurotransmitters and fuse with the presynaptic membrane to release neurotransmitters into the synaptic cleft

Question 24

Neurotransmitters

Answer 24

Chemicals that allow an action potential to be transferred across a synapse.
When neurotransmitters are released from the synaptic vesicles into the synaptic cleft, they bind to specific receptors on the postsynaptic membrane

Question 25

Post synaptic membrane

Answer 25

Membrane of the post synaptic neurone or effector cells.
Receptors on the post synaptic membrane have a complementary shape to the neurotransmitters released from the synaptic knob
When neurotransmitters bind to the receptors, the Action potential continues

Question 26

Excitatory neurotransmitters

Answer 26

Generate an action potential in the postsynaptic cell.

When the neurotransmitters bind to receptors on the postsynaptic membrane, the ,membrane is depolarised

Question 27

Inhibitory neurotransmitters

Answer 27

Prevent an action potential from being generated in the post synaptic cell. When the neurotransmitters bind to the receptors on the post synaptic membrane, the membrane is hyperpolarised

Question 28

summation

Answer 28

Process where neurotransmitters from multiple neurones are summed together to produce a response

Question 29

Spatial summation

Answer 29

Takes place when multiple presynaptic neurones form a junction with a single neurone
Each presynaptic neruone release neurotransmitters which means they can establish a generator potential that reaches the threshold value

Question 30

Temporal summation

Answer 30

Takes place when multiple nerve impulses arrive at the same synaptic knob within a short period of time.
More neurotransmitter is released into the synaptic cleft, so more neurotransmitter is available to bind to receptors on the post synaptic membrane

Question 31

Neuromuscular junction

Answer 31

A synapse between a motor neurone and a muscle cell. An action potential is transmitted across the synapse using the neurotransmitter acetylcholine

Question 32

Process at the neuromuscular junction