F214 Unit 4: Nervous communication
- Created by: Saoirse
- Created on: 09-06-14 23:04
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Sensory receptors
- Specialised cells that can detect changes in our surroundings
- Energy transducers - convert from one form to another
- Each change in energy is called a stimulus
Generating nerve impulses
- Neurones have specialised gated protein channels specific to K+ or Na+ ions
- When open permability for the ion increases, decreases when closed.
- Nerve cell membranes have carrier proteins that actively pump Na+ out and K+ in.
- More Na+ moved out than K+ in giving inside of cell a negative (less positive) charge
- Cell membrane is polarised
- Nerve impulse created by altering permeability to Na+ ions.
- Movement of ions across membrane causes a change in potential difference (charge) across the membrane
- Inside becomes less negative than usual - depolarisation
- A generator potential is a small depolarisation caused by sodium ion entering the cell
Neurones
- Sensory neurones: carry AP from sensory receptor to central nervous system
- Motor neurones carry AP from CNS to an effector e.g muscle/gland
- Relay neurones connect sensory and motor neurones
- Function is to transmit AP from one place to another. Specialised:
- Very long to transmit AP across a long distance
- Many gated ion channels to control entry of Na+, K+ and Ca+
- Na/K pumps present that use ATP to pump Na+ out
- Maintain a potential difference across cell membrane
- Surrounded by fatty myelin sheath
- Series of Schwann cells
- Insulates neurone from electrical activity in nearby cells
- Gaps = Node of Ranvier
- Motor neurones have cell body in CNS and have a long axon to carry AP to effector
- Sensory neurones have a long dendron carrying the AP from a sensory receptor to the cell body, positioned just outside CNS. Then have a short axon carrying AP to CNS
- Dendrites are connected to neruones
Resting potentials and action potentials
Resting potential is the potential difference across a neurone cell membrane while the cell is…
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