Ch. 11 - Nervous System ALL KEY TERMS

key terms only

Action potential

Nerve impulse

Adrenal glands

Triangular-shaped glands on top of each kidney that play a role in the function of the sympathetic nervous system

Adrenergic fibers

Nerve fibers that secrete norepinephrine

Afferent neuron

Sensory nerve that carries impulses toward the central nervous system

Alpha-adrenergic receptors

Receptors to norepinephrine that generally produce an excitatory response

Amygdala

Portion of the limbic system concerned with emotion

Arachnoid mater

Delicate meningeal layer lying between dura mater and pia mater

Autonomic nervous system

Subdivision of the nervous system responsible for regulating activities that maintain homeostasis; also called visceral motor system

Axon

Fiber extending from a neuron’s cell body that conducts impulses

Babinski sign

An abnormal neurological response in older children and adults that involves dorsiflexion of the great toe along with fanning of the other toes when the sole is firmly stroked

Basal nuclei

Masses of gray matter deep within the cerebrum; play a role in the control of movement; also called basal ganglia

Beta-adrenergic receptors

Receptors to norepinephrine that generally produce an inhibitory response

Blood-brain barrier

Semi-permeable membrane that exists throughout the brain that protects the brain of foreign substances

Brainstem

Stem-like portion of the brain that connects the cerebral hemispheres to the spinal cord; consists of the midbrain, pons, and medulla oblongata

Broca’s area

Area in brain’s left hemisphere responsible for the muscle movements required for speech

Central canal

Minute opening through the spinal cord; carries cerebrospinal fluid

Central nervous system

Portion of the nervous system consisting of the brain and spinal cord

Cerebellum

Second largest region of the brain responsible for coordination of voluntary movement and balance; also plays a role in sensory, cognitive, and emotional functions

Cerebral cortex

The surface of the cerebrum consisting of a thin layer of gray matter

Cerebrospinal fluid

Clear, colorless fluid that fills the brain’s ventricles and central canal and also bathes the outside of the brain and spinal cord

Cerebrum

Largest portion of the brain

Cholinergic fibers

Nerve fibers that secrete acetylcholine

Choroid plexus

Network of blood vessels lining the floor and wall of the brain’s ventricles; charged with creating cerebrospinal fluid

Corpus collosum

Thick bundle of nerves that runs along the brain’s longitudinal fissure and joins the two hemispheres of the brain

Corticospinal tracts

Spinal tracts responsible for fine movements of hands, fingers, feet, and toes on the opposite side of the body; also called the pyramidal tracts

Cranial nerves

Nerves of the peripheral nervous system that arise directly from the brain (instead of from the spinal cord)

Decussation

The action of spinal cord tracts crossing from one side of the body to the other in the brainstem

Dendrites

Portion of neuron charged with receiving signals from other neurons and conducting the information to the cell body

Depolarization

Loss of the difference in charge between the inside and outside of the nerve cell membrane

Dermatome

A specific area of the skin innervated by a spinal nerve

Diencephalon

Region deep inside the brain that consists of thalamus and hypothalamus

Dorsal column

Relays sensations of deep pressure and vibration in the spinal cord

Dorsal nerve root

Posterior spinal nerve root that carries sensory information into the spinal cord

Dura mater

Tough, outer meningeal layer

Dural sinuses

Spaces created by separations in the dura mater; collect blood that has passed through the brain and is on its way back to the heart

Efferent neuron

Motor nerve that carries impulses away from the central nervous system

Enteric nervous system

Network of neurons lining the intestinal tract that communicates with the central nervous system

Epidural space

Small space between the outer covering of the spinal cord and the vertebrae

Extrapyramidal tracts

Group of spinal tracts associated with balance and muscle tone

Fascicles

Bundles of spinal nerve fibers

Fissure

Deep sulci in the cerebrum

Frontal lobe

Portion of the cerebrum responsible for decision making, reasoning, memory, and voluntary movements

Glial cells

Supportive cells of the nervous system; also called neuroglia

Gray matter

Nervous tissue containing mostly cell bodies of motor neurons and interneurons

Gut-brain axis

Bidirectional communication pathway between the central nervous system and the enteric nervous system

Gyri

Thick ridges in the cerebrum

Hippocampus

Portion of the limbic system charged with converting short-term memory into long-term memory

Hypothalamus

The bottom half of the diencephalon of the brain, which is responsible for many vital body functions

Insula

Area of cerebrum hidden behind lateral sulcus; plays a role in perception, motor control, self-awareness, and cognitive functioning

Interneurons

Connect incoming sensory pathways with outgoing motor pathways in the central nervous system

Limbic system

Complex set of structures in the brain responsible for emotion and learning

Medulla oblongata

Attaches brain to spinal cord; contains centers that govern heart rate, blood pressure, and breathing

Membrane potential

Refers to the relative difference of electric charge across the nerve cell membrane

Meninges

Layer of fibrous connective tissue covering the brain and spinal cord

Midbrain

Portion of the brainstem containing tracts that relay sensory and motor impulses

Mixed nerve

Nerve that contains both sensory and motor fibers

Motor neurons

Relay messages from the brain to muscle or gland cells; also known as efferent neurons

Muscarinic receptors

Receptors to acetylcholine on target cells that exhibit a variable response

Myelin

Fatty sheath encasing the axons of many neurons; formed by Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system

Nerve

A bundle of neurons that transmits impulses between the brain and spinal cord and the rest of the body

Neurilemma

Outermost layer of Schwann cell; necessary for nerve regeneration

Neuroglia

Cells in the nervous system that support neurons but do not conduct impulses

Neurons

Nervous system cells that conduct impulses

Neuroplasticity

The ability of the brain to change its physical structure

Nicotinic receptors

Receptors to acetylcholine on target cells that produce an excitatory response

Nodes of Ranvier

Gaps in the myelin sheath along an axon

Occipital lobe

Portion of the cerebrum responsible for analyzing and interpreting visual information

Parasympathetic division

Division of the autonomic nervous system that primarily has a calming effect; also called craniosacral division

Parietal lobe

Portion of the cerebrum concerned with body sensations and proprioception

Peripheral nervous system

Portion of the nervous system consisting of the network of nerves throughout the body

Pia mater

Innermost meningeal layer covering brain and spinal cord

Plexus

A network of nerves

Polarization

The electrical state of a cell membrane that has an excess of positive ions on one side of the membrane and an excess of negative ions on the other

Pons

Portion of the brainstem containing tracts that convey signals to and from different parts of the brain

Reflex arc

A neural circuit that bypasses regions of the brain where conscious decisions are made

Refractory period

Period immediately after stimulation during which a nerve or muscle is unresponsive to further stimulation

Reticular activating system

Network of nerve pathways in the brainstem that receives sensory input from eyes and ears to maintain state of wakefulness

Saltatory conduction

Conduction of nerve impulses along myelinated axons from one node of Ranvier to the next

Sensory neurons

Detect stimuli; also known as afferent neurons

Soma

Nerve cell body; contains the nucleus

Somatic reflex

Reflex involving contraction of a skeletal muscle after being stimulated by a somatic motor neuron

Spinal nerve

Single nerve resulting from fusion of dorsal and ventral nerve roots; carries both sensory and motor fibers

Spinocerebellar tract

Spinal tract responsible for proprioception

Spinothalamic tract

Spinal tract that relays sensations of temperature, pressure, pain, and touch

Subarachnoid space

Separates arachnoid mater from pia mater around the brain

Subarachnoid space

Space between arachnoid mater and pia mater; filled with cerebrospinal fluid

Subdural space

Separates dura from arachnoid mater around the brain

Sulci

Shallow grooves in the cerebrum

Sympathetic division

Division of the autonomic nervous system responsible for “fight or flight” response; also called thoracolumbar division

Synapse

Space between the junction of two neurons in a neural pathway

Synaptic knob

Terminal ending of axon branches; contains vesicles containing a neurotransmitter

Temporal lobe

Portion of the brain responsible for hearing, smell, and visual recognition

Thalamus

Area within the diencephalon that acts as gateway for sensory impulses

Tracts

Bundles of axons in the spinal cord that serve as routes of communication to and from the brain

Ventral nerve root

Anterior spinal nerve that carries motor information out of the spinal cord

Ventricles

Four chambers within the brain

Visceral reflexes

Reflex of the autonomic nervous system affecting organs

Wernicke’s area

Area in brain’s left hemisphere charged with language comprehension; also involved in speech production

White matter

Nervous tissue containing bundles of axons that carry impulses from one part of the nervous system to another