Introduction to Physiology of the Nervous System

A comprehensive set of vocabulary flashcards covering the functional organization, cell types, physiology, and pharmacology of the nervous system based on the lecture transcript.

Central Nervous System (CNS)

Composed of the brain and spinal cord, it serves as the primary center for integration and control in the body.

Peripheral Nervous System (PNS)

The part of the nervous system outside the brain and spinal cord, consisting of $31$ pairs of spinal nerves and $12$ pairs of cranial nerves.

Sensory (Afferent) Neurons

Neurons that conduct signals from sensory receptors toward the Central Nervous System.

Motor (Efferent) Neurons

Neurons that conduct signals from the Central Nervous System to effectors such as muscles and glands.

Interneurons (Association Neurons)

Neurons confined to the CNS that integrate incoming sensory information and elicit motor responses by activating motor neurons.

Somatic Nervous System (SoNS)

The division of the nervous system that collects information from the external environment and innervates skeletal muscles via a single efferent neuron.

Autonomic Nervous System (ANS)

The division of the nervous system that controls involuntary organs (heart, glands, viscera) and usually involves a two-neuron efferent pathway (preganglionic and postganglionic).

Sympathetic Division (SyNS)

An ANS division primarily responsible for emergency responses and the utilization of metabolic resources; often called the 'adrenergic' system.

Parasympathetic Division (PaNS)

An ANS division that helps in the restoration of body reserves and elimination of waste; often called the 'cholinergic' system.

Cranial Nerves

Twelve pairs of nerves ($I-XII$) that are components of the PNS and mediate special senses, somatic sensations, and motor functions.

Anosmia

Loss of the sense of smell, often caused by damage to the Olfactory nerve ($CN-I$) and the cribriform plate.

Bell's Palsy

Paralysis of the muscles of facial expression on one side caused by inflammation of the Facial nerve ($CN-VII$).

Tic Douloureux

Severe facial pain caused by inflammation of the Trigeminal nerve ($CN-V$).

Neuroglia

Non-excitable supporting cells in the nervous system that are $5$ to $50$ times more numerous than neurons; potential causes of glioma.

Astrocytes

Star-shaped CNS glial cells that nourish neurons, remove metabolic waste like ammonia, and stimulate the formation of the blood–brain barrier.

Microglia

Specialized immune cells that act as the macrophages of the CNS.

Oligodendrocytes

CNS glial cells that produce myelin sheaths for electrical insulation; one cell can myelinate several different axons.

Schwann Cells (Neurolemmocytes)

PNS glial cells that form myelin sheaths around larger nerve fibers and participate in neuronal regeneration.

Ependymal Cells

Cells that line the brain ventricles and the central canal of the spinal cord, secreting and circulating cerebrospinal fluid (CSF).

Satellite Cells

Small PNS cells that line the exterior surface of neurons and regulate the external chemical environment.

Nissl Granules (Bodies)

Stacks of rough endoplasmic reticulum in the neuron cell body responsible for the synthesis of neurotransmitters.

Myelin Sheath

A lipid wrapping around axons that protects, electrically isolates, and increases the rate of action potential transmission.

Nodes of Ranvier

Interspersed gaps along the axon where the myelin sheath is absent and current flow across the membrane occurs.

Multipolar Neurons

Neurons with several dendrites and one axon; the most abundant type in the brain and spinal cord.

Bipolar Neurons

Neurons with one main dendrite and one axon, found in the retina, inner ear, and olfactory area.

Unipolar Neurons

Neurons where the dendrites and axon are fused into a continuous process; primarily sensory in function.

Erlanger-Gasser Classification

A system for classifying nerve fibers based on diameter and conduction velocity: Type A (thickest/fastest), Type B, and Type C (thinnest/slowest).

Resting Membrane Potential (RMP)

The voltage difference across the plasma membrane at rest, approximately $-70\text{ }mV$, characterized by electropositivity outside and electronegativity inside.

Depolarization

A state where the membrane potential becomes less negative than the resting potential (usually due to $Na^+$ influx).

Threshold Stimulus

Any stimulus strong enough to initiate an action potential.

Absolute Refractory Period

A period during which the axon membrane is incapable of producing another action potential regardless of stimulus strength.

Continuous (Sweeping) Conduction

Action potential propagation occurring in unmyelinated axons where the entire length of the membrane must be depolarized.

Saltatory (Jumping) Conduction

The rapid propagation of action potentials in myelinated axons, where the impulse jumps from one node of Ranvier to the next.

Electrical Synapse

A junction where plasma membranes are joined by gap junctions, allowing local currents to flow directly between cells for rapid communication.

Chemical Synapse

A junction where a neurotransmitter is released into a synaptic cleft and binds to receptors on a target cell.

Excitatory Postsynaptic Potential (EPSP)

A graded potential that depolarizes the postsynaptic membrane, bringing it closer to the threshold.

Inhibitory Postsynaptic Potential (IPSP)

A graded potential that hyperpolarizes the postsynaptic membrane (via $K^+$ or $Cl^-$ channels), making it less likely to fire an action potential.

Acetylcholine (ACh)

The most abundant neurotransmitter in the PNS, synthesized by Choline Acetyltransferase (CAT) and degraded by Acetylcholinesterase (AChE).

Nicotinic Receptor

A type of cholinergic receptor that is a direct ligand-gated ion channel; blocked by hexamethonium in autonomic ganglia.

Muscarinic Receptor

An indirect ligand-gated cholinergic receptor that uses G proteins; blocked by atropine.

Norepinephrine (NE)

The primary neurotransmitter at postganglionic sympathetic nerve terminals, utilizing alpha ($\text{α}$) and beta ($\text{β}$) adrenergic receptors.

Reflex Arc

A circuit consisting of five components: a receptor, an afferent pathway, an integrating center, an efferent pathway, and an effector organ.

Sympathomimetic Drugs

Drugs that act on adrenergic effector organs to produce effects similar to sympathetic activation, such as Epinephrine and Phenylephrine.