Brain and CNS

Central Sulcus

Fissure that separates the frontal lobe from the parietal lobe; divides the primary motor cortex and primary somatosensory cortex.

Pia Mater

Delicate, innermost meningeal layer that clings tightly to the brain surface and contains many blood vessels.

Efferent Neuron

Motor neuron that carries signals away from the CNS to muscles or glands.

Dendrite

Main receiving region of the neuron that carries signals toward the cell body.

Astrocytes

Glial cells that support neurons, regulate ion balance, and form part of the Blood-Brain Barrier.

Microglia

Immune and phagocytic cells of the CNS that remove debris and pathogens.

Oligodendrocyte

Glial cell that forms the myelin sheath in the CNS; one can myelinate several axons.

Schwann Cell

Glial cell that forms the myelin sheath in the PNS; each myelinates one axon segment.

Action Potential

Rapid electrical signal that travels along the axon; primarily involves sodium (Na⁺) influx and potassium (K⁺) efflux.

Saltatory Conduction

Fast propagation of an action potential that jumps between Nodes of Ranvier along a myelinated axon.

Node of Ranvier

Gaps between myelin segments where voltage-gated ion channels cluster and allow saltatory conduction.

Neuromuscular Junction (NMJ)

Synapse where a motor neuron releases acetylcholine (ACh) to trigger muscle contraction.

Resting Membrane Potential

The inside of a neuron is more negative (~–70 mV) due to unequal ion distribution and K⁺ leak channels.

Corpus Callosum

Large fiber tract that connects the left and right cerebral hemispheres for communication.

Longitudinal Fissure

Deep groove that separates the left and right hemispheres of the cerebrum.

Transverse Fissure

Groove that separates the cerebrum from the cerebellum.

Primary Motor Area

Located in the precentral gyrus just anterior to the central sulcus; controls voluntary skeletal muscle movement.

Somatosensory Cortex

Located in the postcentral gyrus just posterior to the central sulcus; processes touch, pressure, and pain sensations.

Hippocampus

Temporal lobe structure essential for memory formation and learning.

Broca’s Area

Frontal lobe region responsible for speech production (usually in the left hemisphere).

Wernicke’s Area

Temporal lobe region essential for language comprehension (usually in the left hemisphere).

Diencephalon

Contains the thalamus (relays sensory information) and hypothalamus (regulates homeostasis, temperature, hunger, and thirst).

Ventricles

Four fluid-filled cavities in the brain (two lateral, third, and fourth ventricles) that contain cerebrospinal fluid.

Choroid Plexus

Capillary network inside ventricles that produces cerebrospinal fluid (CSF).

CSF Flow Pathway

Lateral ventricles → Interventricular foramen (of Monro) → Third ventricle → Cerebral aqueduct (of Sylvius) → Fourth ventricle → Subarachnoid space → Arachnoid villi → Venous system.

Lumbar Puncture

Performed between L3–L4 or L4–L5 vertebrae to safely collect CSF without injuring the spinal cord.

Parkinson’s Disease

Progressive loss of dopamine-producing neurons in the substantia nigra causing tremors, rigidity, and slow movement.

Hydrocephalus

Accumulation of excess cerebrospinal fluid in the ventricles due to a circulation blockage; increases intracranial pressure.

Meningitis

Inflammation of the meninges (dura, arachnoid, pia) often caused by bacterial or viral infection; symptoms include fever and stiff neck.

Cerebral Palsy

Non-progressive motor disorder caused by brain injury before, during, or shortly after birth; affects movement and coordination.

Poliomyelitis

Viral disease that destroys motor neurons in the spinal cord, leading to paralysis; preventable by vaccination.

Meninges

Three protective layers of the brain and spinal cord — dura mater, arachnoid mater, and pia mater.

Central Nervous System (CNS)

Consists of the brain and spinal cord; processes and integrates information.

Peripheral Nervous System (PNS)

Includes cranial and spinal nerves; carries signals between the CNS and body.

Somatic Nervous System

Voluntary division of the PNS controlling skeletal muscles.

Autonomic Nervous System (ANS)

Involuntary division of the PNS controlling smooth and cardiac muscle and glands.

Sympathetic Division

“Fight or flight” response; increases heart rate, dilates pupils, and inhibits digestion.

Parasympathetic Division

“Rest and digest” response; slows heart rate, stimulates digestion, and conserves energy.