Bio- Neurones
- Created by: Codster
- Created on: 30-04-16 14:09
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- Neurones
- Types of Neurones
- Sensory
- Carry action potential from sensory receptor to CNS
- -Long dendron-short axon
- Motor
- Carry action potential from CNS to effector
- Sensory
- All neurones have...
- Gated ion channels
- Na+/K+ ion pumps
- 3Na+ out to 2K+ in
- A p.d. across membrane
- a myelin sheath
- Resting State
- ATP used to pump 3Na+ out to every 2K+ in
- Membrane-> more permeable to K+ than to Na+ so many diffuse in
- Cell cytoplasm-> contains large anions
- Membrane is polarised
- -60mV
- Action Potential
- Resting state-> polarised -60mV
- Na+ channel, some Na+ diffuse in
- Membrane deploarises- reaches threshold potential
- -50mV
- Voltage-gated Na+ channels open- Na+ flood in
- Membrane reaches action potential
- +40mV
- Na+ channels close/ K+ channels open
- K+ diffuse out- membrane repolarises
- P.d. overshoots- hyperpolarised
- Cell returns to resting state
- P.d. overshoots- hyperpolarised
- K+ diffuse out- membrane repolarises
- Membrane reaches action potential
- Membrane deploarises- reaches threshold potential
- Na+ channel, some Na+ diffuse in
- Resting state-> polarised -60mV
- Refractory Period
- Short period of time afterfiring where it is more difficult to stimulate a neurone
- Absolute
- 2nd stimulus won't cause another action potential
- Relative
- 2nd action potential can occur but only if stimulus is considerably higher than threshold potential
- Reasons...
- Restore original polarity
- Ensures action potentials are only transmitted in one direction
- Absolute
- Short period of time afterfiring where it is more difficult to stimulate a neurone
- Types of Neurones
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