the central nervous system

Question 1

what is the role of the nervous system?

Answer 1

• monitors and co ordinates internal organ function
• responds to changes in the external environment

Question 2

what two parts is the nervous system divided into?

Answer 2

• central
• peripheral

Question 3

what are the two main organs of the CNS?

Answer 3

• brain
• spinal cord

Question 4

describe the process of information passing through the CNS

Answer 4

• nerves send information to the brain via the spinal cord
• the spinal cord receives information from the skin, joints and muscles
• the brain receives information from the senses via the spinal cord
• the brain processes the information and sends a message to the body via the spinal cord
• the brain uses the information to react, remember, think and plan

Question 5

what is the role of neurons?

Answer 5

pass messages via electrical impulses
- receive and transmit between brain cells in response to info received from the rest of the body

Question 6

describe the soma

Answer 6

• life support
• contains nucleus, DNA, ribosomes and mitochondria

Question 7

describe dendrites

Answer 7

• receives messages to send to soma
• branched and short extensions

Question 8

describe the axon

Answer 8

• long cable like extension
• transmits electrical impulses from the cell body to other nerve cells, glands or muscles

Question 9

describe the myelin sheath

Answer 9

• covers axon
• speeds up transmission by providing insulation

Question 10

when do neurons transmit signals?

Answer 10

when stimulated by the sensory input or triggered by neighbouring neurons

Question 11

what are the contact points between neurons?

Answer 11

synapses

Question 12

what is sent across the synaptic gap?

Answer 12

chemical messengers called neurotransmitters

Question 13

what happens if the neurotransmitter isn’t accepted into the next neuron?

Answer 13

it is reabsorbed by the pre synaptic neuron

Question 14

define ‘neuron’

Answer 14

fundamental units of the brain and nervous system, responsible for receiving sensory input and sending electrical impulses between the brain and body to transfer messages

Question 15

describe the axon terminal

Answer 15

• at ends of axon
• has terminal buttons
• pass nerve impulse from cell body to part of body they control or activate
• contains vesicles which store neurotransmitters

Question 16

summarise the process of how a message is sent via neurons

Answer 16

• electrical impulse travels down axon
• electrical impulse arrives at terminal button
• synaptic vesicles in terminal button release neurotransmitters
• electrical signals are transferred to chemical signals
• each neurotransmitter binds to a specific receptor
• after transmission, neurotransmitter is broken down or reabsorbed

Question 17

what is meant by the ‘action potential’?

Answer 17

the method by which the nerve impulse passes down the axon of the neuron to stimulate the release of neurotransmitters

Question 18

what is depolarisation

Answer 18

• a tiny impulse is triggered by a change in electrical potential of the neuron
• resting membrane potential = -70
• inside of neuron has a slight negative charge in relation to the outside

Question 19

describe the process of action potential

Answer 19

• neurons act as batteries with separate charges
• electrical impulse due to electrical potential changing in neuron - depolarisation
• environmental stimulus occurs and triggers part of neural membrane to open and allow positively charged ions inside cell and negatively charged ions out
• for the channel to be open, charge is -55mv otherwise neuron returns to resting state
• -55 only occurs if enough receptors on dendrite are activated, allowing positive charge to increase neuron to +40mv
• impulse is transmitted down nerve fibre