Neural Control and Coordination
Neural Control and Coordination tests impulse generation, transmission, synapse, brain regions and reflex action. Expect membrane potentials, saltatory conduction and autonomic divisions.
Core rules
- Resting potential is about -70 mV. The Na+/K+ pump moves 3 Na+ out and 2 K+ in; K+ leak maintains negativity.
- Depolarisation: Na+ influx reaches threshold; the axon obeys the all-or-none law. Repolarisation follows K+ efflux.
- Myelin enables saltatory conduction, making impulses faster.
- Synapse: neurotransmitter release, such as acetylcholine at the neuromuscular junction.
- Brain: cerebrum for thought and voluntary action; cerebellum for balance; medulla for vital centres; hypothalamus links nervous and endocrine systems.
- Reflex arc: receptor, afferent neuron, centre, efferent neuron, effector.
Worked example
A neuron at rest is -70 mV. A stimulus opens Na+ channels, influx raises the membrane potential to threshold, voltage-gated Na+ channels open and the potential spikes to about +30 mV. Repolarisation follows K+ efflux. Explain the event.
Reasoning: the pump establishes ion gradients; channels use them. Answer: action potential.
Traps that cost marks
- The all-or-none law applies to an axon, not to graded potentials.
- Cerebellum, not cerebrum, coordinates balance.
- Hypothalamus links nervous and endocrine systems.
- A reflex arc can bypass the brain.
- Nodes of Ranvier are gaps in myelin.