Revision cards - nerves (communication and homeostasis)

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Nerves CA
Receptors are energy transducers ­ convert energy from one form to another
Each detects a different energy form
receptor Energy changes detected
Rod & cone cells in retina Light intensity and range of wavelength
Sound receptors in inner ear Vibrations in air
Olfactory cells lining inner surface of nasal Presence of volatile chemicals
Pressure receptors in skin Pressure on skin
Muscle spindles Length of muscle fibres
Taste buds, hard palate, epiglottis and first Presence of soluble chemicals
part of oesophagus
Sensory neurone ­ receptor to CNS
Motor neurone ­ CNS to effector
Relay neurone 0 connects sensory and motor neurone within CNS
Organisation Sensory neurone

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Nerves CA
Motor neurone
Relay neurone
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Nerves CA
Similarities Differences
Sensory and motor Motor neurones have their
neurones are long to cell body within the CNS
transmit AP over long
Sensory & motor neurones Sensory neurones have
are surrounded by a fatty their cell body just outside
myelin sheath (a series of the CNS
Schwann cells) that
insulates the neurone from
electrical activity in nearby
Have gaps called Nodes of Motor neurones have a
Ranvier where Schwann long axon to transmit AP to
cells meet effectors
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Nerves CA
Have a cell body containing Sensory neurones have a
the nucleus, many short axon to transmit AP
mitochondria and to the CNS
dendrites to connect with Sensory neurones have a
other neurones long dendron to transmit
AP from receptor to cell
feature mylinated Non-mylinated
Speed of conduction Fast (100-120 ms-1) Slow (0.…read more

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Nerves CA
Where found In peripheral nervous system IN CNS and in nerves
carrying impulses to/from CNS controlling organs with no
conscious control
Resting potential is -65mv.
Outer surface positively charged, inner surface negatively charged = polarised
Generated by sodium-potassium pump ­ channel protein in membrane.
Three Na+ out (active transport), two K+ in = polarisation.
Action potential is generated by a stimulus opening gated Na+ channels. If enough Na+ enters the
cell then voltage gated Na+ channels open and Na floods in.…read more

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Nerves CA
the neurone from one node to
the next.
- A synapse is a junction
between 2 or more
- Between 2 neurones is a
small gap, the synaptic
cleft, about 20nm wide
- An action potential cannot
bridge this gap. Instead,
the pre synaptic action
potential causes the release
of a neurotransmitter that
diffuses across the gap.…read more

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Nerves CA
- This then generates a new action potential in the post synaptic neurone
In a cholinergic synapse the neurotransmitter = Acetylcholine
A synapses role is to allow signals from different parts of the nervous system to create the same
response.…read more

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Nerves CA
If sufficient depolarisation to reach the threshold potential, a new AP is
generated in the post synaptic neurone
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