structure and function of sensory, relay & motor neurons Flashcards
What is an axon?
a long projection of a nerve cell that typically conducts electrical impulses known as action potentials.
What is a cell body?
the spherical part of the neuron that contains the nucleus. Connects to the dendrites.
What is a nucleus?
command centre of our cells. It contains our chromosomes and genetic info needed for reproduction.
What is a dendrite?
projections of a neurone that receives signals from other neurons.
What is the nodes of ranvier?
gaps in the insulating sheath on the axon of certain neurons that serves to facilitate the rapid conduction of nerve impulses.
What is the myelin sheath?
an insulating layer that forms around nerves. allows electrical impulses to transmit quickly along nerve cells.
what is a synapse?
the site of transmission of electric nerve impulses between two nerve cells or between a neuron and a gland or muscle cell.
Name the three types of neurons.
motor, sensory and relay.
Describe the structure and function of a sensory neuron.
These have long dendrites and short axons.
Found in receptors such as the eyes, ears, tongue and skin, and carry nerve impulses to the spinal cord and brain.
However, not all sensory neurons reach the brain, as some neurons stop at the spinal cord, allowing for quick reflex actions.
Describe the structure and function of a relay neuron.
They have short dendrites and short axons.
These connect the sensory and motor neurons.
Found in the brain and spinal cord and allow sensory and motor neurons to communicate.
Allow fast reflex responses to take place by bypassing the brain.
Describe the structure and function of a motor neuron.
Short dendrites and long axons.
These connect the CNS to the effectors.
Found in the CNS and control muscle movements.
When stimulated they release neurotransmitters that bind to receptors on muscles to trigger a response, which lead to movement.
Describe chemical transmission in synapses.
Each neuron is separated from the next by a synapse - includes the cleft and the presynaptic terminal and the postsynaptic receptor site.
Signals are transmitted chemically between neurons by synaptic transmission.
When the electrical impulse reaches the end of the neuron it triggers the release of neurotransmitter from the synaptic vesicles.
Neurotransmitters then diffuses across the synaptic cleft.
Once it passes the gap it binds to the postsynaptic receptor sites. The chemical message is then converted into an electrical impulse and the process begins again in the next neuron.
How can transmission of messages through the neuron be electric?
When a neuron is in a resting state, it is negatively charged.
When a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a split second.
An action potential will pass through the neuron when it is positively charged.
This allows an electrical impulse to move through the neuron.
What it a neurotransmitter?
chemicals that diffuse across the synaptic cleft to the next neuron.
Once it passes the gap it binds to the postsynaptic receptor sites. The chemical message is then converted into an electrical impulse and the process begins again in the next neuron.
How do neurones communicate?
Neurons receive messages from sensory organs or other neurons. Messages pass between two neurons by neurotransmitters diffusing across the synaptic cleft.
Messages run through neurons by becoming electrical impulses triggered by neurotransmitters reaching a postsynaptic receptor site.
