M1 Nerves Flashcards
What are neurones? What are two different types of neurone?
Neurones are nerve cells/specialised cells that can transmit an action potential. The two most important types are sensory neurones and motor neurones.
What are the differences between the structure and functions of motor and sensory neurones?
FUNCTION - Sensory neurones transmit action potentials from sensory receptor to the CNS whereas motor neurones transmit action potentials from the CNS to effectors.
STRUCTURE - both have myelin sheath. However, the sensory neurone has a dendron and the motor neurone doesn’t.
How is the resting potential established and maintained?
When a neurone is at rest, the membrane is polarised. The inside of cell = -60mV compared to outside cell. The membrane contains sodium potassium ion pumps which maintain this potential difference - using ATP they pump 3 sodium ions out for every 2 potassium into the cell. At rest the cell contains more potassium cells than sodium cells.
Describe and explain how an action potential is generated
1) When a neurone is stimulated, it becomes depolarised. The change in potential difference, once it reaches threshold, opens VGSI channels. Sodium ions flow into the cell.
2) the inside is LESS negative than the outside. When it reaches +40mv, sodium channels close and action potential is generated.
3) Repolarisation - VGPI open to allow potassium ions out of cell. This reduces the potential difference, returning it to resting (-60mv)
4) Hyperpolarisation - the potential briefly falls below normal resting potential. This REFRACTORY PERIOD explains why we can’t keep stimulating a neurone.
How does the Hyperpolarisation that occurs after the action potential prevent the impulse going backwards?
There is a REFRACTORY period. Depolarisation cannot take place and a further action potential cannot be generated.
Outline the role of sensory receptors
Sensory receptors are specialised cells that detect changes and convert one form of energy into an action potential
