The nervous system and neurons · GCSE Psychology

Structure of the nervous system

The central nervous system (CNS) is the brain and spinal cord.
The peripheral nervous system (PNS) is all the nerves outside the CNS. It includes the somatic nervous system (voluntary movement and senses) and the autonomic nervous system (automatic functions).
The autonomic system has two parts: the sympathetic nervous system triggers the "fight or flight" response (faster heart rate, more adrenaline); the parasympathetic nervous system returns the body to rest ("rest and digest").
The James-Lange theory of emotion says we feel emotion after our body reacts: we see a bear, our heart races, and then we feel afraid.

Sensory neurons carry messages from the senses to the CNS. Relay neurons pass messages within the CNS. Motor neurons carry messages from the CNS to muscles.
Structure: dendrites receive signals; the cell body; the axon carries the electrical impulse, often covered in a myelin sheath that speeds it up; axon terminals pass the signal on.

At a synapse, an electrical impulse causes neurotransmitters to be released into the gap, where they bind to receptors on the next neuron.
Excitation makes the next neuron more likely to fire; inhibition makes it less likely.
Hebb's theory of learning: when neurons fire together repeatedly, the connections between them strengthen, forming cell assemblies ("neurons that fire together wire together"). This is linked to neuroplasticity.

Central nervous system: The brain and spinal cord.
Autonomic nervous system: The part of the nervous system controlling automatic functions.
Sympathetic nervous system: The part that triggers the fight or flight response.
Neuron: A nerve cell that carries messages.
Synapse: The gap between two neurons.
Neurotransmitter: A chemical that carries a signal across a synapse.
Myelin sheath: A fatty coating that speeds up nerve impulses.
Neuroplasticity: The brain's ability to change and form new connections.