Neurons And synaptic Transmision Flashcards
What are neurons?
They are specialised nervous cells that move electrical impulses to and from the CNS.
What are the 7 parts of a neuron?
Cell body- control centre for the neuron has nucleus inside it
Nucleus- contains genetic material
Dendrites- receives electrical impulses from other neurons or sensory receptors
Axon- long fibre that takes the impulse from the cell body to the axon terminal
Myelin sheath- insulating layer that protects the axon and speeds up impulse transmission
Schwann cells- make up myelin sheath
Nodes of ranvier- gaps in the myelin sheath, speeds up the impulse along the axon
What are the 3 types if neurons?
Sensory neurons- found in sensory receptors( skin, ears,eyes) Carey electrical impulses to the CNS via the PNS. They convert information from the sensory receptors into electrical impulses which are converted into sensations by the brain. Some sensory impulses do not travel all the way to the brain but just to the spinal cord allowing faster reflex responses to occur.
Motor neuron- located in the CNS but project their axons outside it, send electrical impulses into muscles and glands in order to create a certain effect such as movement if they send the impulses into certain muscles. These glands and muscles are called effectors
Relay neuron- found in the CNS and connect sensory neurons to motor neurons so they can communicate. During a reflex arc the relay neurons in the spinal cord can decide how you respond but analysing the sensation instead of the brain.
How do electrical impulses travel between neurons
It travels from the pre synaptic neuron to the post synaptic neuron across the synaptic cleft which is the space between neurons. When action potential (another word for electrical impulse) reaches the pre synaptic terminal neuro transmitters are released from sacs in a process called exocytosis.
The neurotransmitters diffuse across the synaptic cleft and bind to specialised post synaptic receptor sites, this only takes a fraction of a second. Until the process is stopped by re uptake when the neurotransmitters are taken back the ore synaptic neurons, the quicker they are taken back the smaller the effects.
The binding of the neurotransmitters to the receptor sites allows information to be passed to the next neuron and the information can only travel in one direction and the receptor side has no neurotransmitters and vice versa.
Types of neurotransmitters( excitatory and inhibitory)
Neurotransmitters can be both excitatory or inhibitory or just one or the other such as GABA which is inhibitory and is targeted by some types of medical drugs.
Excitatory neurotransmitters causes electrical charges in the membrane making a excitatory post synaptic potential making it more likely another impulse will be fired.
An inhibitory neurotransmitter will create an inhibitory post synaptic potential decreasing the chance another neuron will be fired off.
A neuron can receive both at the same time and the likelihood of an impulse being fired is by adding up both inputs and finding the net results called the summation. It the net effect is inhibitory it won’t fire if it’s excitatory it’ll fire.
