Nervous System — Key English Terminology

1.The central nervous system, abbreviated CNS, is composed of the brain and the spinal cord. It handles integration and processing of information.

2.The peripheral nervous system, abbreviated PNS, is composed of twelve pairs of cranial nerves and thirty-one pairs of spinal nerves. It carries afferent and efferent signals.

3.The autonomic nervous system splits into sympathetic — fight or flight, with short preganglionic and long postganglionic fibers; and parasympathetic — rest and digest, with long preganglionic and short postganglionic fibers.

4.Soma is the cell body — the metabolic center containing the nucleus. Dendrites receive signals. The axon conducts action potentials. The axon hillock is the trigger zone where action potentials initiate.

5.The myelin sheath insulates the axon and speeds conduction. Nodes of Ranvier are the gaps where saltatory conduction occurs. Schwann cells form myelin in the PNS; oligodendrocytes form myelin in the CNS.

6.Astrocytes form the blood-brain barrier and provide metabolic support. Microglia are the immune defense cells of the CNS, performing phagocytosis.

7.Resting membrane potential is approximately negative seventy millivolts. Threshold is approximately negative fifty-five millivolts.

8.Depolarization is sodium influx raising the potential. Repolarization is potassium efflux bringing it back down. Hyperpolarization drops below the resting level. The all-or-none law: if threshold is reached, the action potential fires fully; otherwise it does not fire at all.

9.The sodium potassium ATPase pump moves three sodium out and two potassium in per ATP consumed. During an action potential, voltage-gated sodium channels open first, then voltage-gated potassium channels open — the timing difference produces the depolarization, repolarization waveform.

10.Frontal lobe handles motor, decision-making, and Brocas area for speech production. Parietal lobe handles somatosensory processing. Temporal lobe handles auditory and Wernickes area for language comprehension. Occipital lobe handles vision.

11.Hippocampus consolidates short-term memory into long-term memory — tested in year one fourteen as question twelve. Amygdala handles emotions like fear and anxiety.

12.Thalamus is the sensory relay station. Hypothalamus controls body temperature, hunger, thirst, circadian rhythm, and the pituitary. Cerebellum coordinates movement and balance.

13.Medulla oblongata is the autonomic control center for heartbeat, respiration, and blood pressure — tested in year one fourteen as question fourteen. Pons handles respiratory regulation and sleep-wake transitions.

14.Acetylcholine acts at the neuromuscular junction and parasympathetic neurons; deficiency causes myasthenia gravis. Dopamine handles reward and motor control; low dopamine causes Parkinsons, high dopamine is linked to schizophrenia.

15.Norepinephrine works in sympathetic postganglionic neurons. Serotonin handles mood and sleep; low serotonin is linked to depression.

16.Year one thirteen essay focused on amino-acid neurotransmitters: Glutamate is the major excitatory neurotransmitter in the CNS. GABA, gamma-aminobutyric acid, is the major inhibitory neurotransmitter in the CNS. Glycine is the inhibitory neurotransmitter in the spinal cord.