neurons and synaptic transmission Flashcards
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 action potential’s direction?
from the main body cell, down the long axon to the synaptic terminals
what is the CNS
central processor of info and control centre for human behaviour made up of all the neurons in the brain and spinal cord
what is the peripheral nervous system? (PNS)
branches out from spinal cord it’s a web of nerves carrying info to and from the CNS to the rest of the body
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
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
what is the function of the neuron
to communicate with 1000s of other cells at a time in huge networks. these networks adapt as we have new experiences new networks are formed when we learn something new
describe the axon
long branch from the cell body that passes electrical impulses down to the other end of the neuron to communicate
describe dendrites
branches at the top end of the neuron that receive messages from the other neurons
describe cell body
main point of the cell where the nucleus (which stores DNA) sits and it contains mitocondria
describe the axon hillock
the area that connects the cell body to the axon and where action potential is generated
describe the myelin sheath
fatty deposit that provides electrical insulation for an axon and allows electrical nerve impulse to be passed along faster/coats axon and speeds up action potential
describe the nodes of ranvier
gaps between adjacent myelin sheaths speed up action potential
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
define neuron
nervous system, responsible for receiving sensory input and sending electrical impulses between the brain and body to transfer messages
what’s the function of neurotransmitters?
chemical messengers that take around info that are released from pre-synaptic neuron into the synaptic cleft after an action potential then stimulate post-synaptic neuron and assist neuron to make its own action potential and also inhibit the post-synaptic neuron making it less likely to produce an action potential. allow neurons to communicate.
what is the role of neurons
make a chain forming a passage which allows messages to be sent from one part of the brain to another keeping the brain and body working correctly
form new connections everytime we learn something new
what is the synapse?
where the communication between one neuron and the next takes place
it has three main elements pre-synaptic neuron where action potential starts,
post-synaptic neuron where the message travels to
the tiny gap between the two called the synaptic cleft which neurotransmitters are released into and travel across it
summarise the process of how a message is sent via neurons
- electrical impulse travels down axon
- electrical impulse arrives at synaptic terminals
- 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
when do neurons transmit signals?
when stimulated by the sensory input or triggered by neighbouring neurons
what is sent across the synaptic gap?
chemical messengers called neurotransmitters
what happens if the neurotransmitter isn’t accepted into the next neuron?
is reabsorbed by the pre synaptic neuron
describe the processes of synaptic transmission
- action potential moves down pre-synaptic neurons and causes vesicles with neurotransmitters to move close to the terminal membrane
- vesicles fuse with the membrane in a process called exocytosis which causes neurotransmitters to be released into synaptic cleft
- neurotransmitters bind to protein receptors on the post-synaptic neuron & stimulate both neurons the activation of the receptors on the post-synaptic neuron causes the post-synaptic to increase the probability of producing an action potential
- once neurotransmitter released into cleft removed by reuptake taken back up to pre-synaptic neuron
degraded by enzymes in the synaptic cleft
diffusion dispersed away from synaptic cleft
describe serotonin
neurotransmitter
- happiness and good mood
- regulates sleep-wake cycle with melatonin
- low levels linked to depression and anxiety
- selective serotonin reuptake inhibitors prescribed for mental disorders
describe dopamine
neurotransmitter
- produces pleasure when the reward pathway is activated
- memory, learning, movement
describe endorphins
neurotransmitter
- relieves pain and stress
- during pleasurable activities
strength of synaptic transmission as an explanation of how messages move around the brain
Much of the evidence comes from brain scans such as PET scans. This provides objective and reliable evidence of the brain functioning which increases reliability. For example, PET scans have shown differences in synaptic receptor sites related to the serotonin pathway in women with PMDD suggesting synaptic transmission is important for the brain. However, PET scans do not give microscopic detail on transmission
weakness of synaptic transmission
Much of the evidence that has come from animals to generalise from rats and cats to human brains isn’t valid as there are differences in animal brains to humans for example Van den Oever uses rats to study changes in the synapses of heroin-addicted rats when they relapse which may not be accurate for humans. Additionally, individual differences isn’t taken to account as it assumes everyone’s synaptic transmission is used in the brain in the same way. Some ppt with diff levels of neurotransmitters so processes can be the same but messages are influenced
