The structure and function of sensory, relay and motor neurons. The process of synaptic transmission, including reference to neurotransmitters, excitation and inhibition. Flashcards
What are neurons?
Neurons are cells that are specialised to carry neural information throughout the body.
Which 3 types of neurons do we look at?
Sensory, relay and motor.
What do neurons typically consist of?
- a cell body
- dendrites
- an axon
Describe how the cell body, dendrites and axon are connected
- Dendrites at one end of the neuron receive signals from other neurons or from sensory receptors. Dendrites are connected to the cell body, the control centre of the neuron.
- From the cell body, the impulse is carried along the axon where it terminates at the axon terminal.
What does the myelin sheath do?
This allows nerve impulses to transmit more rapidly along the axon. If the myelin sheath is damaged, impulses slow down.
Describe dendrites
Dendrites protrude from the cell body, these carry nerve impulses from neighbouring neurons towards the cell body
Describe the cell body
Cell body includes a nucleus, this contains genetic material of the cell.
Describe the axon
Axon is covered in myelin sheath that protects the axon and speeds up electrical transmission of the impulse. The axon carries impulses away from the cell body down the length of the neuron
Describe myelin sheath
Myelin sheath is segmented by gaps called nodes of ranvier these speed up transmission by forcing it to ‘jump’ across the gaps along the axon.
Define motor neurons
These connect the CNS to effectors such as muscles and glands. They have short dendrites and long axons
Define sensory neuron
These carry messages from the Peripheral nervous system to the CNS. They have long dendrites and short axons.
Define relay neuron
These connect the sensory neurons to the motor or other relay neurons. They have short dendrites and short axons. They are found only in the brain and spinal cord.
What are motor neurons?
A motor neuron is a nerve cell (neuron) whose cell body is located in the spinal cord and whose fiber (axon) projects outside the spinal cord to directly or indirectly control effector organs, mainly muscles and glands. Motor neurons’ axons are nerve fibers that carry signals from the spinal cord
What are sensory neurons?
Sensory neurons are nerve cells that transmit sensory information (sight, sound, feeling, etc.). They are activated by sensory input, and send projections to other elements of the nervous system, ultimately conveying sensory information to the brain or spinal cord. Not all of these travel to the brain. Some terminate in the spinal cord to allow reflex actions to occur quickly without the delay of sending impulses to the brain.
Describe the function of the motor neuron
Form synapses with muscles and control their contractions. When stimulated, the neuron releases neurotransmitters that bind to receptors on the muscles and triggers a response which leads to muscle movement.