Zusammenfassung der Ressource
4.1.2 Nerves
- All receptor cells are transducers,
in which one form of energy, the
stimulus energy, is converted into
another form, electrical energy.
- Receptors in mammals are
adapted to respond to
different aspects of the
environment such as: • light
intensity and wavelength •
sound • touch and pressure •
temperature • chemicals
- sensory neurons transmit
nerve impulses from a
receptor to the central
nervous system (brain or
spinal cord)
- Structure of a motor neuron
- Large nucleus, large
quantities of rough er and golgi
bodies, short dentrites that
carry nerve impulses towards
the cell body
- Structure of a sensory neuron
- Long dendrite, short axon,
transmit impulses from a
receptor to the CNS
- When not conducting a nerve impulse, there is a p.d
across the plasma membrane, such that the inside has a
-70mV charge compared with the outside
- Na+-K+ pumps in the plasma membrane actively transport
K+ ions into the cell and Na+ ions out
- 3 Na+ ions actively transported out for every 2 K+ ions
actively transported in. The axon contains organic anions
tro which the membrane is impermeable
- This and a slight loss of K+ ions through the permeable
membane, accounts for the resting potential
- The membrane is effectively impermeable to Na+ ions
- Resting potential
- Action potential
- generated by a stimulus that excites
the neurone causing sodium ion
channels to open allowing Na+ to
diffuse in making the inside less
negative