Nervous System: Nervous Tissue and Brain

Critical vocabulary terms and definitions regarding the anatomy and physiology of the nervous system, including cell types, action potentials, brain divisions, and spinal functions.

Central nervous system (CNS)

The division of the nervous system that consists of the brain and the spinal cord.

Peripheral nervous system (PNS)

The division consisting of nerves that connect the CNS with the rest of the body.

Neuroglia (glia)

The most abundant type of nerve cell that supports, protects, insulates, nourishes, and generally cares for neurons; these cells undergo mitosis.

Neurons

Nerve cells that conduct nerve impulses and do the communicating for the nervous system; they are delicate and do not undergo mitosis.

Astrocytes

A type of neuroglial cell that forms the blood-brain barrier.

Ependymal cells

Neuroglial cells that help form cerebrospinal fluid (CSF).

Microglia

Neuroglial cells protective through the phagocytosis of pathogens and damaged tissue.

Schwann cells

Cells that produce the myelin sheath for neurons located in the Peripheral Nervous System (PNS).

Oligodendrocytes

Cells that produce the myelin sheath for neurons located in the Central Nervous System (CNS).

Myelin

An insulating layer made of protein and fatty substances that allows nerve impulses to travel quickly down the axon.

Dendrites

Multiple neuronal structures that receive signals and transmit them toward the cell body.

Axon

The single structure of a neuron that transmits signals away from the cell body.

Neurilemma

A layer found only in the PNS that is important in the regeneration of a severed nerve.

Nodes of Ranvier

Areas of the axon not covered by the myelin sheath.

Sensory neurons

Neurons that carry information from the periphery toward the CNS; also known as afferent neurons.

Interneurons

Neurons found only in the CNS that connect sensory and motor nerves.

Motor neurons

Neurons that carry information from the CNS toward the periphery; also known as efferent neurons.

White matter

Nervous tissue composed mostly of myelinated axons.

Gray matter

Nervous tissue composed of unmyelinated axons, cell bodies, interneurons, and synapses.

Nuclei

Clusters of cell bodies located within the CNS.

Ganglia

Clusters of cell bodies located within the PNS.

Depolarization

The stimulated state of a neuron where it becomes positive as $Na$ moves in.

Repolarization

The return to the resting/ready state where the neuron becomes negative as potassium moves out.

Saltatory conduction

The process where action potentials jump quickly from node to node along a myelinated axon.

Synaptic cleft

The space between the axon of one neuron and the dendrites of the next neuron.

Cerebrum

The largest part of the brain, further classified into four lobes and joined by the corpus callosum.

Gyri

Convolutions or elevations that increase the surface area of the brain for thinking.

Sulci

Shallow grooves between gyri.

Frontal lobe

The 'executive' lobe responsible for behavior, personality, attention, voluntary motor control, and intellectual functions.

Broca’s area

The motor speech area in the frontal lobe that controls movements of the mouth and tongue for word formation.

Parietal lobe

Contains the postcentral gyrus and somatosensory area; receives and integrates info from skin and muscles regarding temperature, pain, pressure, and joint position.

Temporal lobe

Responsible for hearing (primary auditory cortex), smell (olfactory area), memory, and speech.

Occipital lobe

Responsible for visual perception, reading, judging distances, and seeing in 3D.

Wernicke’s area

Located in the parietal and temporal lobes; concerned with the translation of words into thought and vice-versa.

Thalamus

The 'receptionist' of the diencephalon that relays information to the correct area of the cerebrum.

Hypothalamus

A diencephalon structure that acts as a thermostat, regulates autonomic functions, and controls the pituitary gland.

Medulla oblongata

Part of the brain stem called the 'vital center' because it controls HR, BP, and R; also a reflex center for coughing, sneezing, swallowing, and vomiting.

Cerebellum

The brain part that coordinates voluntary motor activity and balance.

Limbic system

Known as the 'emotional brain'.

Reticular activating system (RAS)

Regulates the sleep-wake cycle and maintains consciousness.

Meninges

Three layers of connective tissue surrounding the brain and spinal cord: pia mater, arachnoid mater, and dura mater.

Choroid plexus

Ventricle structures made of ependymal glial cells that form cerebrospinal fluid (CSF).

Decussation

The crossing over of spinal cord tracts, where the right side of the brain connects to the left side of the body and vice-versa.

Reflex arc

A 5-component pathway (receptor, sensory neuron, integrating center, motor neuron, effector organ) that processes information without involving the brain.