Nervous System I: Structure and Function

Comprehensive vocabulary flashcards covering the structural and functional organization of the nervous system, cell types, electrophysiology, and neurotransmitters according to the lecture notes.

Nervous System

An organized system designed to detect changes (stimuli) in the internal and external environments, evaluate that information, and initiate responses through muscles or glands.

Sensory Neurons

Specialized cells and sensory receptors capable of perceiving a wide variety of stimuli or changes within or outside the body.

Central Nervous System (CNS)

The structural and functional center of the nervous system, composed of the brain and the spinal cord.

Motor Neurons

Neurons responsible for conducting impulses from the CNS to effectors, such as muscle or glandular cells.

Neurotransmitter

A chemical messenger released at a synapse that triggers a response, such as muscle contraction or glandular secretion.

Gray Matter

Tissue within the CNS containing dendrites, neuronal cell bodies, unmyelinated axons, and neuroglia.

Nuclei

Functional groups formed by clusters of neuronal cell bodies within the gray matter of the brain and spinal cord.

White Matter

Tissue composed primarily of bundles of myelinated axons organized into tracts or pathways.

Peripheral Nervous System (PNS)

All nervous tissue located outside the CNS, including cranial nerves, spinal nerves, ganglia, plexuses, and sensory receptors.

Ganglia

Clusters of neuronal cell bodies located outside the brain and spinal cord.

Nerves

Bundles consisting of axons, associated connective tissue, and blood vessels located in the PNS.

Afferent Division

The sensory division consisting of all pathways that carry information toward the CNS.

Efferent Division

The motor division comprising all pathways that carry information from the CNS toward effectors.

Somatic Nervous System (SNS)

The division responsible for conducting motor information to somatic effectors, specifically skeletal muscles, involved in voluntary movements.

Autonomic Nervous System (ANS)

Also known as the visceral nervous system, it operates without voluntary control and regulates smooth muscle, cardiac muscle, and glands.

Enteric Nervous System (ENS)

Often called the 'digestive brain,' it is an extensive neuronal network distributed from the esophagus to the anus that can function independently of the CNS.

Myenteric Plexus

Also known as Auerbach's plexus, it is located between muscle layers and primarily controls gastrointestinal motility.

Submucosal Plexus

Also known as Meissner's plexus, it is located within the submucosa and controls the secretions of digestive organs.

Nissl Bodies

Condensations of rough endoplasmic reticulum in the neuronal cell body used for synthesizing proteins for growth and axon regeneration.

Dendrites

Short, highly branched extensions of a neuron that serve as the main receptor or input structure.

Axon

A single, thin, cylindrical neuronal process that propagates nerve impulses away from the cell body toward another cell.

Trigger Zone

The area at the junction of the axon hillock and the initial segment where nerve impulses typically originate.

Synaptic Vesicles

Small membrane-bound sacs in synaptic bulbs or varicosities that store neurotransmitters.

Neurofibrils

Fine chains composed of intermediate filaments that provide shape and support to the neuron's cytoskeleton.

Multipolar Neurons

The most common structural type of neuron, possessing several dendrites and one single axon.

Bipolar Neurons

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

Unipolar Neurons

Also called pseudounipolar neurons, they have a single process emerging from the cell body that branches into central and peripheral directions.

Interneurons

Also called association neurons, they are located within the CNS and process incoming sensory information to determine motor responses.

Astrocytes

CNS neuroglia that provide support, help form the blood-brain barrier (BHE), regulate the chemical environment, and form scar tissue after injury.

Oligodendrocytes

CNS neuroglia with processes that wrap around axons to form myelin sheaths, which increase impulse conduction speed.

Microglia

Small CNS glial cells with a phagocytic function, removing cellular debris and damaged nervous tissue.

Ependymal Cells

Glial cells that line the brain ventricles and the central canal of the spinal cord, producing and circulating cerebrospinal fluid (LCR).

Schwann Cells

PNS neuroglia that form the myelin sheath and the neurilemma around peripheral axons.

Satellite Cells

PNS glial cells that surround and support neuronal cell bodies clustered in ganglia.

Chemical Synapse

A specialized region where a presynaptic neuron releases a neurotransmitter into a synaptic cleft to communicate with a postsynaptic cell.

Electrical Synapse

A communication site where cells are joined by gap junctions (connexons), allowing ions and nerve impulses to flow directly between cells.

Resting Membrane Potential (PMR)

The voltage difference across the plasma membrane of a non-stimulated cell, typically valued at $-70\,mV$.

Action Potential (PA)

A rapid, transient electrical signal involving depolarization followed by repolarization that propagates along the membrane surface.

Threshold

The minimum magnitude of depolarization required to generate a nerve impulse, typically around $-59\,mV$.

Depolarization Phase

The phase of an action potential where voltage-gated $Na^+$ channels open, allowing an influx of positive ions that makes the interior less negative.

Repolarization Phase

The phase where $Na^+$ channels inactivate and voltage-gated $K^+$ channels open, allowing $K^+$ to exit and return the membrane toward a negative state.

Saltatory Conduction

A rapid mechanism of impulse propagation occurring in myelinated axons, where the impulse 'leaps' between nodes of Ranvier.

Nodes of Ranvier

Interruptions in the myelin sheath where the axonal membrane is exposed and contains a high concentration of voltage-gated ion channels.

Acetylcholine (ACh)

A neurotransmitter that is excitatory at the neuromuscular junction but can be inhibitory in other areas, such as the heart.

Glutamate

The primary excitatory neurotransmitter in the brain, involved in learning and memory.

GABA

The most common inhibitory neurotransmitter in the brain.

Dopamine

A monoamine involved in mood elevation and skeletal muscle control; its deficiency is associated with Parkinson's disease.

Nitric Oxide (NO)

A small gaseous neurotransmitter that is produced on demand rather than stored in vesicles and is involved in memory and learning.

Neuropeptides

Large-molecule neurotransmitters consisting of chains of 2 to 40 amino acids, such as endorphins or Substance P.

Neuromodulator

A substance, often a neuropeptide, that is co-secreted with a neurotransmitter to regulate or modulate its effects.