Chapter 1: The Nervous System - Neurons, Neuroanatomy, and Neurodevelopment

Vocabulary practice flashcards covering basic neuronal structures, supporting glial cells, anatomical and functional nervous divisions, embryonic development, and major brain regions from Chapter 1.

Input zone

The dendrites of a neuron, which serve as extensions of the soma to receive incoming information.

Integration zone

The cell body (soma) of a neuron, housing the nucleus and cellular organelles, where the decision to produce a neural signal is made.

Conduction zone

The axon of a neuron, a long extension that carries electrical information away from the soma towards the axon terminals.

Output zone

The axon terminals (boutons) of a neuron, which house transmitters to transfer chemical signals to other neurons or target tissues.

Neural Doctrine

The concept advocated by Santiago Ramón y Cajal stating that each neuron is an individual entity, isolated from neighboring neurons by small spaces.

Reticular Theory

The theory advocated by Camillo Golgi proposing that neurons are not distinct units, but are continuous or fused together to act as a whole.

Multipolar neuron

The most common neuron type, characterized by having numerous dendrites and a single axon.

Bipolar neuron

A neuron with a single dendrite at one end and a single axon at the other end, commonly found in sensory systems.

Unipolar neuron

Also known as a monopolar neuron, it features a single process extending from the cell body that branches in two directions (one for input and one for output).

Sensory neurons

Neurons responsible for detecting internal and external environmental changes (stimuli) and transmitting this input to the brain.

Interneurons

Neurons that process and interpret sensory information to determine an appropriate response; they comprise the majority of neurons in the brain.

Motor neurons

Output neurons that execute responses to sensory stimuli by transmitting signals to effectors such as muscles and glands.

Reductionism

A scientific approach that breaks down complex system functions or behaviors into smaller constituent parts or levels of analysis to better understand them.

Synaptic cleft

The small fluid-filled gap, measuring approximately $20\text{--}40\text{ nm}$ wide, separating the presynaptic membrane from the postsynaptic membrane.

Synaptic vesicles

Small membrane-bound sacs located within axon terminals that store chemical messengers called neurotransmitters.

Astrocytes

Star-shaped glial cells in the CNS that regulate the extracellular environment, contribute to the blood-brain barrier (BBB), and are often involved in edema.

Microglia

Glial cells that function as the resident immune cells of the brain.

Ependymal cells

Specialized glial cells lining the ventricles of the brain that produce and secrete cerebrospinal fluid (CSF).

Oligodendrocytes

Glial cells responsible for forming myelin sheaths around axons in the Central Nervous System (CNS).

Schwann cells

Glial cells responsible for forming myelin sheaths around nerve fibers in the Peripheral Nervous System (PNS).

Satellite cells

Glial cells that surround and support the cell bodies of sensory neurons in peripheral ganglia.

Somatic nervous system (SNS)

An anatomical/functional division of the nervous system under voluntary control that innervates skeletal muscles and sensory systems.

Autonomic nervous system (ANS)

A division of the nervous system under involuntary control that regulates visceral organs, smooth muscle, cardiac muscle, and glands.

Preganglionic neurons

Autonomic axons originating in the CNS that travel outward to synapse with postganglionic neurons located in peripheral ganglia.

Dorsal roots

Spinal nerve pathways that carry incoming sensory (afferent) fibers into the dorsal region of the spinal cord.

Ventral roots

Spinal nerve pathways that carry outgoing motor (efferent) fibers away from the ventral region of the spinal cord.

Dorsal root ganglion (DRG)

A nodular structure on the dorsal root containing the cell bodies of sensory afferent neurons.

Lumbar puncture

A procedure involving needle insertion between vertebrae L3 and L4 in adults (L4–L5 in children) into the subarachnoid space to collect cerebrospinal fluid.

Gastrulation

The early embryonic process following blastulation that establishes the three primary germ layers: endoderm, mesoderm, and ectoderm.

Neurulation

The developmental process occurring around 22 days post-conception in which the thickened ectodermal neural plate folds and closes to form the neural tube.

Anencephaly

A severe congenital defect characterized by the absence of a major portion of the brain due to failure of the anterior neural tube to close properly.

Meningocele

A developmental defect characterized by protrusion of the meninges caused by failure of the distal neural tube to close completely.

Prosencephalon

The embryonic forebrain primary vesicle that differentiates into the telencephalon (cerebrum), diencephalon, and optic vesicles.

Mesencephalon

The primary brain vesicle corresponding to the midbrain, which remains relatively undivided during neural development.

Rhombencephalon

The embryonic hindbrain primary vesicle that differentiates into the metencephalon (pons and cerebellum) and myelencephalon (medulla).

Fragile X syndrome

A genetic disorder causing physical and cognitive impairment, associated with a failure to eliminate excess synaptic connections postnatally.

Precentral gyrus

A ridge located in the frontal lobe directly anterior to the central sulcus, responsible for integrating motor signals.

Postcentral gyrus

A ridge in the parietal lobe immediately posterior to the central sulcus, responsible for processing primary somatic sensory information.

Basal ganglia

Deep gray matter structures—including the caudate nucleus, putamen, and globus pallidus—interconnected with the frontal lobe to control movement.

Limbic system

A brain network comprising the cingulate gyrus, amygdala, hippocampus, fornix, olfactory bulb, and hypothalamus, involved in emotion, memory, and learning.

Thalamus

A paired subcortical structure located deep in the brain that acts as the main relay station for sensory pathways heading to the cerebral cortex.

Hypothalamus

A subcortical region regulating essential homeostatic functions such as hunger, thirst, and body temperature, while controlling the pituitary gland.

Tectum

The dorsal roof region of the midbrain, consisting of the superior colliculi (visual processing) and inferior colliculi (auditory processing).

Tegmentum

The ventral main body of the brainstem containing structures such as the substantia nigra, periaqueductal gray, and reticular formation.

Hydrocephalus

A condition characterized by an abnormal accumulation of cerebrospinal fluid within the brain ventricles, leading to elevated intracranial pressure.

Meninges

The three protective connective tissue membranes—dura mater, arachnoid membrane, and pia mater—enclosing the brain and spinal cord.

Blood-brain barrier (BBB)

A protective, selective vascular barrier formed by endothelial cells linked by tight junctions and surrounded by perivascular astrocyte end-feet.

Glymphatic system

A specialized glia-mediated waste clearance network in the brain that flushes interstitial fluid and clears metabolic debris during sleep.

Ischemia

A restriction or blockage of blood supply to brain tissue, depriving neurons of vital oxygen and nutrients and potentially inducing cellular damage.