Neurons, structure, role and function Flashcards
how many nerve cells are in the human nervous system and what is their function?
there are 100 billion nerve cells (neurons), 80% are located in the brain. neurons transmit signals electrically and chemically which provide the nervous system with a primary means of communication.
what are motor neurons?
they connect the central nervous system to effectors such as muscles and glands through carrying impulses from the cns to effectors. they have short dendrites and long axons.
what are relay neurons?
they carry messages within the central nervous system and connect sensory neurons to motor or other relay neurons. they have short dendrites and short axons.
what are sensory neurons?
they carry messages from the peripheral nervous system to the central nervous system. they have long dendrites and short axons.
what is the cell body or soma?
the part of the cell that contains the nucleus
what is the axon and what are axon terminals?
the axon is the part of the neuron that takes info away from the cell body down length of the neuron.
the axon terminals are the hair like ends of the axon
what are dendrites?
extensions that are branch like structures that protrude from the cell body. they carry nerve impulses from neurons towards the cell body.
what is the myelin sheath?
a fatty substance that surrounds and protects the axon
what are the node of Ranvier?
they are gaps in the axon that speed up transmission of the impulse.
what are schwann cells?
cells that produce myelin located on the myelin sheath.
what is the reflex arc and what is the behaviour that happens?
- the sensory information about the stimulus is detected by sense organs in the central nervous system by a message from the sensory neuron.
- they pass a message on to a relay neuron in the spinal cord in the cns.
- this then transfers the message to a motor neuron this then carries the message to an effector or muscles which causes the muscle to contract.
what is an electric transmission?
when a neuron is in a resting state the inside of the cell is negatively charged compared to outside. when a neuron is activated, the inside of cell is positively charged for a split second causes an action potential to occur. this creates an electrical impulse that travels down axon towards end of neuron.
