Neurons and synaptic transmission (The structure and function of neurons…
Neurons and synaptic transmission
The structure and function of neurons
Neurons carry neural information throughout the body
They can be either sensory, relay and motor neurons. They consist of a cell body, dendrites and an axon.
Dendrites are connected to the cell body and the impulse is carried across the axon where it terminates at the axon terminal.
The Myelin Sheath is an insulating layer around the axon and it allows nerve impulses to travel more rapidly along the axon
Carry nerve impulses from sensory receptors (vision, taste and touch) to the spinal chord and the brain
Sensory neurons convert information from the from these receptors into neural impulses, when they reach the brain they are translated into sensations of heat and pain etc, allowing an appropriate resonse
Relay neurons allow motor neurons and sensory neurons to communicate with eachother
They are based in the brain and spinal chord
They project their axons outside of the CNS and indirectly or directly control muscles
They form synapses with muscles and control their contractions . The motor neuron releases neurotransmitters when stimulated which bind to receptors in the muscles and trigger a response- leading to muscle movement
The muscle contracts as a result of the axon of a motor neuron firing
Dendrites receive information from sensory receptors and then the info is passed down to the cell body and on to the axon. At the axon the info is passed down in the form of an electrical signal. This is the action potential
Action potential reaches axon, transferred to another neuron/tissue. Crosses the synaptic gap (between pre synaptic neuron and post). In the axon terminal are the synaptic vesicles (contain neurotransmitters)
Neurotransmitters carry the signal across the synaptic gap and bind to receptor sites on the post synaptic cell, then it becomes activated.
Once activated they are either exitatory (noradrenalin) or inhibitory (GABA)
Excitatory and inhibitory neurotransmitters
Excitatory neurotransmitters (noradrenalin) are the nervous systems 'on switches' as it increases the likelihood that the neuron will fire
Inhibitory neurotransmitters (serotonin and GABA) decrease the likelihood that the neuron will fire as they are the 'off switches' and calm the mind, inducing sleep
The likelihood of the neuron firing is determined by adding up the amount of excitatory and inhibitatory synaptic input. The net result of the calculation (summation) determines whether or not the cell fires