AP Biology - Plants and Human Body Systems
OpenStax Biology for AP — Chapter 26: The Nervous System — AP BIOLOGY Revision Notes & Topical Questions
5 min read 8 parts Lesson 7 of 15 Unit quiz
Lesson summary
OpenStax Biology for AP — Chapter 26: The Nervous System — AP BIOLOGY notes: Describe neurons, action potentials, synapses, the autonomic nervous system and central control.Neuron structure — dendrites receive signals, the cell body integrates them, and the axon carries impulses …
- Resting potential
- Depolarisation
- Repolarisation
- Neurotransmitter
- Saltatory conduction
- Reflex arc
Section 1 of 8Neurons and glia
Neurons and glia
Neuron structure
- Neuron structure dendrites receive signals, the cell body integrates them, and the axon carries impulses away.
Glia are non-neuronal cells that support neuronal development and signalling.
Section 2 of 8Action potentials
Resting potential
- Resting potential about −70 mV, maintained by the sodium-potassium pump and leak channels.
Depolarisation
- Depolarisation a stimulus above threshold opens voltage-gated Na+ channels.
Repolarisation
- K+ channels then open.
The action potential is all or nothing and travels along the axon.
Myelin sheaths speed transmission by saltatory conduction between nodes of Ranvier.
Section 3 of 8Synapses
1
An action potential reaches the axon terminal and opens Ca2+ channels.
2
Vesicles release neurotransmitter into the synaptic cleft.
3
The neurotransmitter binds receptors on the next cell and opens ion channels, producing excitatory or inhibitory postsynaptic potentials.
4
The neurotransmitter is broken down or taken back up.
Synapses
Synapses ensure one-way transmission and allow integration of signals.
Electrical synapses pass signals directly through gap junctions.
Synaptic plasticity (long-term potentiation and depression) strengthens or weakens synapses.
Section 4 of 8The autonomic nervous system
The autonomic nervous system
The sympathetic division is fight or flight; it is triggered by danger, exercise and stress.
The parasympathetic division is rest and digest, active during restful periods such as after a meal.
The divisions have opposite effects on most organs.
| Effect | Sympathetic | Parasympathetic |
|---|---|---|
| Heart rate | Increases | Decreases |
| Pupils | Dilate | Constrict |
| Digestion | Slows | Stimulates |
Section 5 of 8Central control
1
The central nervous system (brain and spinal cord) integrates information and is protected by the meninges.
2
The medulla oblongata in the brainstem is the centre for breathing and heart rate.
3
The cerebellum coordinates movement; the cortex has frontal, temporal, occipital and parietal lobes.
4
Reflex arcs give a quick response through the spinal cord: sensory neuron, relay neuron, motor neuron.
Section 6 of 8Nervous versus hormonal control
Nervous versus hormonal control
Nervous control is rapid and short-lived.
Hormonal control is slower and longer lasting.
Drugs and toxins often act at synapses by blocking receptors or preventing transmitter breakdown.
Section 7 of 8Key terms
| Term | Meaning |
|---|---|
| Action potential | Rapid, all-or-nothing change in membrane potential along an axon. |
| Threshold | Membrane potential that must be reached to fire an action potential. |
| Synapse | Junction where a neuron passes a signal to another cell. |
| Neurotransmitter | Chemical released across a synapse. |
| Saltatory conduction | Jumping of the impulse between nodes of Ranvier along a myelinated axon. |
| Reflex arc | Pathway of sensory, relay and motor neurons giving a rapid response. |
Section 8 of 8Exam technique
1
Saying the sympathetic division is triggered after a meal — the parasympathetic division is
2
Describing the action potential as graded — it is all or nothing
3
Forgetting the role of Ca2+ at the synapse — it triggers vesicle release
4
Confusing the roles of sensory and motor neurons — sensory carry signals to the CNS, motor carry them to effectors
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