Nervous System Anatomy, Physiology, and Pharmacology

Comprehensive vocabulary flashcards covering autonomic nervous system divisions, receptor subtypes, neuropharmacology, and key terms in neuroanatomy and neurophysiology.

Dual innervation

The condition in which an organ receives nerve fibers from both the sympathetic and parasympathetic divisions of the autonomic nervous system.

Cholinergic fibers

Nerve fibers that secrete acetylcholine (ACh); includes preganglionic fibers of both sympathetic and parasympathetic divisions, as well as postganglionic parasympathetic fibers.

Adrenergic fibers

Nerve fibers that secrete norepinephrine (NE); includes most postganglionic fibers of the sympathetic division.

Acetylcholinesterase (AChE)

The enzyme in the synaptic cleft that rapidly breaks down acetylcholine, resulting in short-lived parasympathetic effects.

Monoamine oxidase (MAO)

The enzyme that breaks down norepinephrine after it has been reabsorbed into the nerve fiber.

Nicotinic receptors

Cholinergic receptors located within the ganglia of the autonomic nervous system, the adrenal medulla, and the neuromuscular junction that produce an excitatory response to acetylcholine in all target cells.

Muscarinic receptors

Cholinergic receptors located on glands, smooth muscle, and cardiac muscle cells innervated by cholinergic fibers that exhibit a variable (excitatory or inhibitory) response to acetylcholine depending on the receptor subtype.

Alpha-adrenergic receptors

Adrenergic receptors to norepinephrine that generally produce an excitatory response, such as causing blood vessels to constrict; subtypes include $\alpha_1$ and $\alpha_2$.

Beta-adrenergic receptors

Adrenergic receptors to norepinephrine that generally produce an inhibitory response, such as causing blood vessels in the heart and skeletal muscles to dilate; subtypes include $\beta_1$ and $\beta_2$.

Beta blockers

A group of drugs that bind to beta receptors, blocking norepinephrine and epinephrine to lessen the sympathetic response; used to treat high blood pressure and irregular heartbeats.

Sympathomimetics

Drugs that enhance sympathetic action by either promoting the release of epinephrine or directly stimulating adrenergic receptors (e.g., phenylephrine).

Phenylephrine

A sympathomimetic drug that stimulates $\alpha_1$ receptors, causing bronchiole dilation to ease breathing and vasoconstriction in nasal vessels to relieve congestion.

Sympatholytics

Drugs that block the effects of epinephrine and norepinephrine primarily by inhibiting adrenergic receptors; used to lower blood pressure by promoting vasodilation.

Parasympathomimetics

Drugs (also called cholinergics) that stimulate or mimic the parasympathetic division by stimulating nicotinic or muscarinic receptors or by inhibiting acetylcholinesterase (e.g., physostigmine).

Parasympatholytics

Drugs (also called anticholinergics) that inhibit acetylcholine release or block its receptors to reduce parasympathetic activity; used to treat asthma by dilating bronchioles.

Action potential

A nerve impulse.

Adrenal glands

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

Afferent neuron

A sensory nerve that carries electrical impulses toward the central nervous system.

Amygdala

A portion of the limbic system concerned with emotion.

Arachnoid mater

A delicate meningeal layer lying between the dura mater and the pia mater.

Autonomic nervous system

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

Axon

A fiber extending from a neuron's cell body that conducts nerve impulses.

Babinski sign

An abnormal neurological response in older children and adults characterized by dorsiflexion of the great toe and fanning of the other toes upon firmly stroking the sole.

Basal nuclei

Masses of gray matter located deep within the cerebrum that play a role in motor control; also called basal ganglia.

Blood-brain barrier

A semi-permeable membrane existing throughout the brain that shields brain tissue from foreign substances.

Brainstem

Stem-like structure connecting the cerebral hemispheres to the spinal cord, consisting of the midbrain, pons, and medulla oblongata.

Broca's area

A region in the left cerebral hemisphere responsible for coordinating the muscle movements necessary for speech.

Central canal

A minute channel through the core of the spinal cord that carries cerebrospinal fluid.

Central nervous system

The division of the nervous system consisting of the brain and spinal cord.

Cerebellum

The second-largest region of the brain, responsible for voluntary movement coordination, balance, and cognitive, sensory, and emotional functions.

Cerebral cortex

The outer surface of the cerebrum formed by a thin layer of gray matter.

Cerebrospinal fluid

A clear, colorless fluid filling the ventricles and central canal that bathes the exterior of the brain and spinal cord.

Cerebrum

The largest portion of the brain.

Choroid plexus

A network of blood vessels along the floor and walls of the brain ventricles responsible for producing cerebrospinal fluid.

Corpus collosum

A thick nerve bundle running along the longitudinal fissure that connects the two cerebral hemispheres.

Corticospinal tracts

Spinal tracts responsible for fine motor control of the hands, fingers, feet, and toes on the opposite side of the body; also termed pyramidal tracts.

Cranial nerves

Peripheral nerves that emerge directly from the brain rather than the spinal cord.

Decussation

The crossing of spinal cord tracts from one side of the body to the other within the brainstem.

Dendrites

Neuron processes that receive incoming signals from other neurons and conduct them toward the soma.

Depolarization

The loss of electrical charge difference across the interior and exterior of a nerve cell membrane.

Dermatome

A specific cutaneous region innervated by a single spinal nerve.

Diencephalon

A region located deep inside the brain that comprises the thalamus and hypothalamus.

Dorsal column

Spinal cord tract that relays sensations of deep pressure and vibration.

Dorsal nerve root

The posterior root of a spinal nerve that carries sensory information into the spinal cord.

Dura mater

The tough, outermost meningeal layer.

Dural sinuses

Venous channels formed between separations of the dura mater that collect blood passing through the brain to return it to the heart.

Efferent neuron

A motor neuron that carries impulses away from the central nervous system.

Enteric nervous system

A neural network lining the gastrointestinal tract that communicates bidirectionally with the central nervous system.

Epidural space

A small anatomical space located between the outer covering of the spinal cord and the surrounding vertebrae.

Extrapyramidal tracts

A group of spinal tracts associated with the maintenance of balance and muscle tone.

Fascicles

Bundles of spinal nerve fibers.

Fissure

Deep sulci situated in the cerebrum.

Frontal lobe

Cerebral lobe responsible for voluntary motor movement, reasoning, memory, and decision making.

Gray matter

Nervous tissue composed primarily of interneurons and motor neuron cell bodies.

Gut-brain axis

The bidirectional communication channel linking the central nervous system with the enteric nervous system.

Gyri

Thick raised ridges on the cerebral surface.

Hippocampus

A limbic system structure responsible for transforming short-term memories into long-term memories.

Hypothalamus

The inferior half of the diencephalon responsible for governing many vital autonomic and bodily functions.

Insula

A hidden cerebral lobe concealed behind the lateral sulcus that contributes to motor control, perception, self-awareness, and cognition.

Interneurons

Neurons in the central nervous system that bridge incoming sensory pathways with outgoing motor pathways.

Limbic system

A complex network of brain structures essential for emotion and learning.

Medulla oblongata

The brainstem region joining the brain to the spinal cord; contains vital centers controlling heart rate, blood pressure, and respiration.

Membrane potential

The relative difference in electrical charge across a nerve cell membrane.

Meninges

A three-layered covering of fibrous connective tissue encasing the brain and spinal cord.

Midbrain

The portion of the brainstem containing nerve tracts that relay motor and sensory impulses.

Mixed nerve

A nerve containing both sensory (afferent) and motor (efferent) nerve fibers.

Motor neurons

Efferent neurons that relay nerve messages from the brain to effector targets such as muscles or glands.

Myelin

A lipid-rich sheath encasing neuronal axons, produced by oligodendrocytes in the CNS and Schwann cells in the PNS.

Nerve

A bundle of neurons transmitting impulses between the brain and spinal cord and peripheral tissues.

Neurilemma

The outer layer of a Schwann cell, essential for peripheral nerve regeneration.

Neuroglia

Supportive non-conductive cells of the nervous system; also referred to as glial cells.

Neurons

Excitable nervous system cells specialized to generate and conduct electrical impulses.

Neuroplasticity

The biological capacity of the brain to alter its physical structure in response to experience or injury.

Nodes of Ranvier

Periodic unmyelinated gaps along an axon's myelin sheath.

Occipital lobe

The posterior region of the cerebrum specialized in receiving, analyzing, and interpreting visual information.

Parasympathetic division

The craniosacral division of the autonomic nervous system that exerts primarily calming, energy-conserving effects on visceral effectors.

Parietal lobe

The cerebral lobe responsible for processing bodily sensations and proprioception.

Peripheral nervous system

The division of the nervous system consisting of the extensive network of nerves located outside the brain and spinal cord.

Pia mater

The delicate, vascular innermost meningeal layer adhering directly to the surface of the brain and spinal cord.

Plexus

An intricate interwoven network of nerves.

Polarization

The electrical resting state of a cell membrane characterized by an excess of positive ions on one side and an excess of negative ions on the opposite side.

Pons

A brainstem structure containing tracts that convey signals between different portions of the brain.

Reflex arc

A neural conduction pathway mediating a reflex that bypasses brain regions where conscious decisions occur.

Refractory period

The brief span following excitation during which a muscle cell or nerve fiber cannot be re-stimulated.

Reticular activating system

A brainstem network that processes sensory signals from the eyes and ears to sustain wakefulness and alertness.

Saltatory conduction

The rapid leaping mode of nerve impulse propagation along myelinated axons from one node of Ranvier to the next.

Sensory neurons

Afferent neurons responsible for detecting internal or external stimuli and transmitting impulses toward the central nervous system.

Soma

The cell body of a neuron, which houses the nucleus and organelles.

Somatic reflex

An involuntary contraction of skeletal muscle triggered by stimulation from a somatic motor neuron.

Spinal nerve

A mixed nerve formed by the union of dorsal (sensory) and ventral (motor) spinal roots.

Spinocerebellar tract

An ascending spinal tract responsible for conveying subconscious proprioceptive information to the cerebellum.

Spinothalamic tract

An ascending spinal tract that transmits sensations of pain, temperature, pressure, and crude touch to the brain.

Subarachnoid space

The fluid-filled anatomical space between the arachnoid mater and pia mater through which cerebrospinal fluid flows.