9.2 1 Nervous systems and neurones Flashcards
nervous system purpose
communication
neurones definition
specialised cells for the rapid transmission of impulses throughout an organism
what is the nervous system made up of
interconnected neurones
receptor cells definition
specialised neurones that respond to changes in the environment
give information from internal and external environment to neurones
effector cells definitions
specialised cells that bring about a response when stimulated by a neurone
muscles or glands
simple nervous systems
receptor cells –neurones—nerve endings associated with effectors
sense organs definition
groups of receptors working together to detect changes in the environment
what do sensory neurones do
neurones that only carry information from internal or external environment into the central processing areas of the nervous system
central nervous system (CNS) definition
a specialised concentration of nerve cells where incoming information is processed and from where impulses are sent out through motor neurones which carry impulses to the effector organs
what is the CNS in vertebrates
the brain and the spinal cord
neurone structure
each has a long nerve fibre that carries the nerve impulse
nerves are bundles of nerve fibres
axons
long nerve fibre of a motor neurone which carries the nerve impulse
away from cell body
dendron
long nerve fibre of a sensory neurone which carries the nerve impulse
towards the cell body
peripheral nervous system
parts of the nervous system that spread through the body and are not involved in the central nervous system
motor neurone
long axon short dendrites connected to an effector synaptic bulbs pass on impulse to effector (see image)
sensory neurone
long dendron
cell body not in middle
connected to a receptor
(See image)
relay neurone
equal axon and dendron
typical neurone
(see image)
nerve impulses definitions
electrical signals transmitted through neurones of the nervous system
what is in the cell body and why
cell nucleus , mitochondria , other organelles and the rough endoplasmic reticulum and ribosomes which are needed for the synthesis of neurotransmitter molecules
dendrites
slender finger-like processes that extend from the cell body of neurones and connect to neighbouring neurones
relay neurones
found in CNS
connect motor and sensory neurones
most vertebrate neurones
are associated with another specialised type of cell the Schwann cell
Schwann cell membrane wraps itself repeatedly around the nerve fibre forming the fatty insulating layer called myelin sheath
gaps between schwann cells
nodes of Ranvier -enable saltatory conduction
why is the myelin sheath important
protects the nerves from damage and speeds up transmission of the nerve impulse
myelin sheath consists of
many layers of schwann cell membrane -cytoplasm and nucleus of schwann cell squeezed to outside
what does the speed of impulses depend on
the diameter of the nerve fibre - the thicker the fibre the more rapidly the impulses travel along it
presence/absence of myelin sheath -myelinated nerves can carry impulses much faster than unmyelinated ones
invertebrates do not
have myelin sheaths on their nerve fibres and have a small nerve diameter so many nerve impulses travel quite slowly
some have developed giant axons to allow to respond quickly to avoid danger
research on axon
uses giant axons because easier to work on and fewer ethical issues when working with invertebrates
vertebrates contain
both unmyelinated and myelinated nerves
e.g. voluntary motor neurones all are myelinated however autonomic neurones control involuntary muscles can be unmyelinated
why is myelin sheath effective
speeds up transmission without the need for giant axons which take up a lot space
