the central nervous system Flashcards
what is the role of the nervous system?
- monitors and co ordinates internal organ function
- responds to changes in the external environment
what two parts is the nervous system divided into?
- central
- peripheral
what are the two main organs of the CNS?
- brain
- spinal cord
describe the process of information passing through the CNS
- 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
what is the role of neurons?
pass messages via electrical impulses
- receive and transmit between brain cells in response to info received from the rest of the body
describe the soma
- life support
- contains nucleus, DNA, ribosomes and mitochondria
describe dendrites
- receives messages to send to soma
- branched and short extensions
describe the axon
- long cable like extension
- transmits electrical impulses from the cell body to other nerve cells, glands or muscles
describe the myelin sheath
- covers axon
- speeds up transmission by providing insulation
when do neurons transmit signals?
when stimulated by the sensory input or triggered by neighbouring neurons
what are the contact points between neurons?
synapses
what is sent across the synaptic gap?
chemical messengers called neurotransmitters
what happens if the neurotransmitter isn’t accepted into the next neuron?
it is reabsorbed by the pre synaptic neuron
define ‘neuron’
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
describe the axon terminal
- 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
summarise the process of how a message is sent via neurons
- 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
what is meant by the ‘action potential’?
the method by which the nerve impulse passes down the axon of the neuron to stimulate the release of neurotransmitters
what is depolarisation
- 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
describe the process of action potential
- 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
describe the structure of a neuron
- the nucleus of the neuron provides the genetic info and the mitochondria provide the neuron with the energy
- dendrites are attached and they receive messages from other neurons
- this message travels along the axon coated in the myelin sheath where action potential takes place
- action potential is when positive ions move in and out of the cell to create an electric current
- once the messages reacht the axon terminal it travels to the terminal buttons where the synapses are
- message converted into a chemical message
describe synaptic transmission
- the electrical impulses travels down the axon terminal and stimulates the vesicles full of neurotransmitters
- the vesicles then move down the pre synaptic neuron
- the neurotransmitters are then released as chemical messengers and diffuse across the synaptic gap
- they attach to the corresponding receptor on the dendrite of the post synaptic neuron and will then be absorbed
- any neurotransmitters that are not absorbed will get reabsorbed by the post-synaptic neuron in the process of reuptake through the transporters
