Chapter 15
The nervous system
Glossary
Action potential: conduction along a nerve or muscle cell membrane caused by a large, transient
depolarization.
Antidiuretic hormone (ADH): hormone that acts on the kidneys to reabsorb more water, thus
reducing urine output.
Afferent fibres: carry nerve impulses towards the central nervous system.
Arachnoid mater: middle layer of the meninges.
Astrocyte: neuroglial cell that helps for the blood–brain barrier.
Autonomic nervous system: involuntary motor division of the motor nervous system.
Axon: process of a neurone that carries impulses away from the cell body.
Brainstem: collective name given to the pons, medulla and midbrain.
Cation: an ion with a positive charge.
Central nervous system: brain and spinal cord.
Cerebellum: anatomical region of the brain responsible for coordinated and smooth skeletal muscle
movements.
Cerebral hemispheres: division of the cerebrum.
Cerebrospinal fluid: fluid that surrounds the central nervous system.
Cerebrum: large anatomical region of the brain thst is divided into the cerebral hemispheres.
Circle of Willis: part of arterial blood supply to the brain.
Cranial nerves: 12 pairs of nerves that leave the brain and supply sensory and motor neurones to
the head, neck, part of the trunk and the viscera of the thorax and abdomen.
Dendrite: part of neurone that transmits impulses towards the cell body.
Diencephalon: anatomical region of the brain consisting of the thalamus, hypothalamus and
epithalamus.
Dura mater: tough outer layer of the meninges.
Effector: muscle, gland or organ stimulated by the nervous system.
Efferent fibres: carry nerve impulses away from the central nervous system.
Ependymal cells: neuroglial cells that line the cavities of the central nervous system.
Epinephrine: hormone produced by the adrenal medulla that is also a neurotransmitter.
Epithalamus: part of the brain that forms the diencephalon.
Ganglia: a group of neuronal cell bodies lying outside the central nervous system.
Hypothalamus: part of the diencephalon with many functions.
Limbic system: part of the brain involved in emotional responses.
Lobe: a clear anatomical division or boundary within a structure.
Medulla oblongata: part of the brainstem.
Meninges: three layers of tissue that cover and protect the central nervous system (dura, arachnoid
and pia maters).
Midbrain: part of the brainstem that links the brainstem to the diencephalon.
Microglia: neuroglia that has the ability to phagocytose material.
Motor area: area located in the cerebral cortex that controls voluntary motor function.
Motor nerves: neurones that conduct impulses to effectors that may be either muscle or glands.
Myelin sheath: fatty insulating layer that surrounds nerve fibres responsible for speeding up
impulse conduction.
Neuroglia: cells of the nervous system that protect and support the functional unit – the neurone.
Neuromuscular junction: region where skeletal muscle comes into contact with a neurone.
Neurone: functional unit of the nervous system responsible for generating and conducting nerve
impulses.
Nuclei: cluster of cell bodies within the central nervous system.
Oligodendrocytes: glial cells that help produce the myelin sheath.
Peripheral nervous system: all nerves located outside of the brain and spinal cord (the central
nervous system).
Pia mater: innermost layer of the meninges.
Pineal gland: part of the diencephalon that has an endocrine function.
Pituitary gland: an endocrine gland located next to the hypothalamus that produces many
hormones.
Receptor: sensory nerve ending or cell that responds to stimuli.
Refractory period: the period immediately after a neurone has fired when it cannot receive another
impulse.
Reticular formation: area located throughout the brainstem that is responsible for arousal,
regulation of sensory input to the cerebrum and control of motor output.
Saltatory conduction: transmission of an impulse down a myelinated nerve fibre where the
impulse moves from node of Ranvier to node.
Sensory area: area of the cerebrum responsible for sensation.
Sensory nerves: neurones that carry sensory information from cranial and spinal nerves into the
brain and spinal cord.
Somatic nervous system: voluntary motor division of the peripheral nervous system.
Spinal nerves: 31 pairs of nerves that originate on the spinal cord.
Synapse: junction between two neurones or neurones and effector site.
Thalamus: part of the diencephalon.
Ventricle: cavity in the brain.
White matter: myelinated nerve fibres.