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how is seeing possible?
cells of the nervous system are able to conduct nerve impulses and pass them to one another
What does the central nervous system consist of?
brain and spinal cord
what does the peripheral nervous system consist of?
-sensory nerves- carrying sensory information from the receptors to the CNS
-motor nerves- carrying motor commands from the CNS to the effectors
what can the PNS be subdivided into?
-autonomic nervous system
-somatic nervous system
what does the autonomic nervous system do?
-involuntary
-stimulates smooth muscle, cardiac muscle and glands
what does the somatic nervous system do?
-voluntary
-stimulates skeletal muscle
what can the autonomic nervous system be divided into?
-sympathetic nervous system
-parasympathetic nervous system
what does the sympathetic nervous system do?
prepares body for fight or flight response
what does the parasympathetic nervous system do?
prepares body for rest and digest
what is the difference between a neurone and a nerve
-neurone is a single cell
-nerve is much more complex structure containing a bundle of the axons of many neurones surrounded by a protective covering
what are the basic characteristics of neurones?
-cell body contains the nucleus and cell organelles within the cytoplasm
-2 types of thin extensions from the cell body:
-very fine dendrites conduct impulses towards the cell body
-a single long process, the axon, transmits impulses away from the cell body
what are the 3 main types of neurone?
-motor neurones
-sensory neurones
-relay neurones
motor neurones
-cell body always within CNS
-axon extends out, conducting impulses from CNS to effectors (muscles or glands)
-axons of some motor neurones can be extremely long, such as those that run the full length of the leg
-motor neurones are sometimes known as effector neurons
sensory neurones
-carry impulses from sensory cells to the CNS
relay neurones
-found mostly within the CNS
-large number of connections with other nerve cells
-also known as connector neurones/interneurons
what is the myelin sheath?
-a fatty insulating layer around the axon
-made up of Schwann cells wrapped around the axon
-affects how quickly nerve impulses pass along the axon
-not all animals have myelinated axons- they are not found in invertebrates and some vertebrate axons are also unmyelinated
