biopsychology 1.2 Flashcards
The structure and function of sensory, relay and motor neurons. The process of synaptic transmission, including reference to neurotransmitters, excitation and inhibition.
neurons
electrically excitable cells that transmit signals throughout the body
7 parts of a neuron
cell body/soma
nucleus
dendrites
myelin sheath
axon
axon terminal
nodes of ranvier
cell body/soma
the largest part of the neuron
it contains the nucleus and the cytoplasm
nucleus
contains the genetic information
dendrites
extensions from the neuron’s cell body receive incoming nerve impulses from other neurons
myelin sheath
the insulation membrane that surrounds an axon
helps to speed neural processes
axon
long extension from the neuron’s cell body which carries outgoing nerve impulses toward other neurons
axon terminal
the axon end of the terminal where nerve impulses are transmitted to the dendrites of other neuron
nodes of ranvier
segmented gaps between myelin sheath that speed up the transmission of the impulse
how do neurons work?
neurons form the nervous system and use nerve impulses to rapidly mass messages around the body
from the cell body, an impulse is carried down the axon as an ‘action potential’ which is an electrical signal along the axon from the cell body to the axon terminals
3 types of neurons
sensory
relay
motor
sensory neuron dendrites
long
sensory neuron axons
short
what do sensory neurons do?
take information from the sensory site to the spinal cord and are found in various locations around the body
where do sensory neurons travel?
from the sensory site e.g. skin to the central nervous system (cns)
what action are sensory neurons involved in?
they convert senses to neural impulses
once they reach the cns, they convert these neural impulses into sensations
these would begin a reflex
where is the soma in the sensory neuron found?
outside the CNS
what do relay neurons do?
communication between sensory and motor neurons
where do relay neurons travel?
they are found in the spinal cord sending messages between sensory neurons and motor neurons
relay neurons dendrites
short
relay neurons axons
short
what action are relay neurons involved in?
they are found within the brain and spinal cord and are used to communicate
they are the thinking, feeling and deciding neuron
where is the soma of the relay neuron found?
inside the CNS
what do motor neurons do?
they begin in the CNS but project back out to the muscles
where do motor neurons travel?
they travel away from the CNS towards the skeletal muscles
what action are motor neurons involved in?
their role is to control muscles by sending messages from the CNS to inform the muscles to expand or contract
motor neurons dendrites
short
motor neurons axons
long
where is the soma of the motor neuron found?
inside the CNS
order of neurons
sensory
relay
motor
connection of the neurons
these neurons work as part of a system to respond to the environment
the sensory neuron begins the process by detecting a change in the environment, for example touching a hot object
a message is sent through to a relay neuron in the central nervous system where are decision is made to move away from the hot object
therefore a signal is sent through a motor neuron away from the central nervous system to a muscle
this is in order to change something, in this case, moving your hand by contracting the bicep
this process happens extremely quick as it forms part of a reflex response
neurotransmitters
chemicals that diffuse across the synapse to the next neuron in the chain
synaptic transmission
neurotransmitters are chemicals that diffuse across the synapse to the next neuron in the chain
once the neurotransmitter crosses the gap, it is taken up by the post-synaptic receptor site - in other words, the dendrites of the next neuron
here, the chemical message is converted back into an electrical impulse and the process of transmission begins again in this other neuron
excitatory neurotransmitters
some neurotransmitters trigger other neurons which increase activity in the brain and body
excitatory neurotransmitters “excite” the neuron and cause it to “fire off the message”, meaning the message continues to be passed along to the next cell
e.g. glutamate
if the neurotransmitter is excitatory then the post synaptic neuron is more likely to fire an impulse
positive
what happens if the neurotransmitter is excitatory?
if the neurotransmitter is excitatory then the post synaptic neuron is more likely to fire an impulse
inhibitory neurotransmitters
some neurotransmitters inhibit other neurons which decreases activity in the brain and body
inhibitory neurotransmitters block or prevent the chemical message from being passes along any further e.g. serotonin, GABA
if the neurotransmitter is inhibitory, then the post synaptic neuron is less likely to fire an impulse
what happens if the neurotransmitter is inhibitory?
if the neurotransmitter is inhibitory, then the post synaptic neuron is less likely to fire an impulse
describe chemical transmission
neurons communicate with each-other within groups known as neural networks
each neuron is separated from the next by a tiny gap called the synapse
signals within neurons are transmitted electrically, however signals between neurons are transmitted chemically across the synapse
when the electrical impulse reaches the end of the neuron (the presynaptic terminal) it triggers the release of neurotransmitters from tiny gaps called synaptic vesicles
summation
the addition of positive and negative post-synaptic potentials
a nerve cell can receive both positive and negative potentials simultaneously
these potentials are summed
if the net effect on the post-synaptic neuron is inhibitory, the neuron will be less likely to fire
if the net effect is excitatory, the neuron will be more likely to fire
outline the structures and processes involved in synaptic transmission
information travels down a neuron through an electrical impulse called the action potential
when the message reaches the end of the neuron, called the axon terminal this message needs to be converted to a chemical message to be transferred to the next neuron
the presynaptic neuron will release neurotransmitters (chemicals) from synaptic vesicles in the axon
these neurotransmitters will then travel across the synapse and are then absorbed by the dendrites on the postsynaptic neuron
this message then transfers back into an electrical impulse to travel down the neuron
neurotransmitters can be excitatory e.g. dopamine which means the post-synaptic neuron is more likely to fire an impulse
they can also be inhibitory e.g. serotonin which means the post-synaptic neuron is less likely to fire an impulse
