Anatomy and Physiology: The Nervous System

A complete set of vocabulary flashcards covering the key structures, cell types, functional divisions, action potential steps, cranial nerves, and cerebral lobes of the human nervous system based on Chapter 9 & 10 lecture notes.

Central Nervous System (CNS)

The main processing and control center of the nervous system consisting of the brain and spinal cord, which receives sensory input, controls basic bodily functions, and responds to external changes.

Peripheral Nervous System (PNS)

The network consisting of all nerves outside the central nervous system that connects the brain and spinal cord to the rest of the body.

Sensory System

The input division of the peripheral nervous system that collects environmental data and carries sensory signals toward the central nervous system.

Motor System

The output division of the nervous system that transmits neural directions from the central nervous system outward to effector muscles and glands.

Somatic Nervous System (SNS)

A division of the peripheral nervous system that controls skeletal muscles and governs voluntary body movements.

Autonomic Nervous System (ANS)

A division of the peripheral nervous system that operates involuntarily to regulate smooth muscle, cardiac muscle, exocrine glands, blood vessels, viscera, and external genitalia.

Parasympathetic Branch

A division of the autonomic nervous system responsible for everyday body maintenance, resting, digesting, and maintaining internal homeostasis.

Sympathetic Branch

A division of the autonomic nervous system that serves as an alert system, initiating the involuntary fight-or-flight response during stressful or dangerous situations.

Neuroglia (Glial Cells)

Specialized non-neuronal support cells in the nervous system that perform structural, metabolic, protective, and insulating helper functions for neurons.

Astrocytes

Star-shaped glial cells located in the central nervous system that provide structural and metabolic support to neurons.

Microglia

Specialized central nervous system glial cells that perform immune-like functions by removing cellular debris and waste.

Ependymal Cells

Glial cells in the central nervous system that cover and line the central canal and cavities of the brain and spinal cord.

Oligodendrocytes

Glial cells in the central nervous system responsible for synthesizing the lipid insulation layer known as myelin.

Schwann Cells

Glial cells in the peripheral nervous system that produce the myelin sheath around peripheral nerve axons.

Satellite Cells

Support cells located in the peripheral nervous system that surround and protect neuron cell bodies inside ganglia.

Neuron

An excitable functional cell of the nervous system responsible for receiving, processing, and transmitting electrical impulses across the body.

Dendrites

Branching extensions of a neuron cell body that receive sensory inputs and chemical signals from surrounding environments or other cells.

Axon

A long cellular extension of a neuron that generates electrical action potentials and conducts them away from the cell body toward target cells.

Axon Terminal

The specialized endpoint of an axon where electrical signals leave the neuron to transmit messages across the synapse.

Synapse

The functional junction where an axon terminal meets and communicates with a target cell or adjacent neuron.

Bipolar Neuron

A structural type of neuron featuring two distinct extensions from the cell body: one single axon and one single dendrite.

Unipolar Neuron

A structural type of neuron characterized by a single process extending from the cell body that splits into central and peripheral branches.

Multipolar Neuron

A structural type of neuron possessing multiple cellular extensions from its cell body, typically including one axon and many dendrites.

Sensory Neurons

Input neurons that convey sensory signals from the peripheral nervous system to the central nervous system.

Motor Neurons

Output neurons that transmit neural directions from the central nervous system out to muscles and glands in the peripheral nervous system.

Interneurons

Neurons located entirely within the central nervous system that process information and link sensory and motor neurons; also called association neurons.

Polarized Cell

A resting excitable cell possessing a net negative internal electrical charge relative to its exterior environment, typically at a resting membrane potential of $-70\,\text{mV}$.

Depolarization

The initial step of an action potential in which $\text{Na}^+$ channel gates open, allowing positively charged sodium ions to rush into the cell and push its charge above the $-55\,\text{mV}$ threshold.

Repolarization

The step of an action potential where $\text{Na}^+$ gates close and $\text{K}^+$ gates open, allowing positive potassium ions to leave the cell and restore its resting negative internal charge.

Action Potential (AP)

An all-or-none electrical impulse created across an excitable cell membrane consisting of depolarization, repolarization, and return to resting potential; in neurons, termed a nerve impulse.

Refractory Period

The period following an action potential during which a neuron cannot respond to a new stimulus until its membrane returns to its resting state.

Myelin

A lipid sheath or insulation wrapper formed around nerve axons that prevents ion leakage and greatly accelerates impulse conduction velocity.

Nodes of Ranvier

Uninsulated gaps in the myelin sheath along an axon that enable action potentials to jump rapidly from node to node.

Multiple Sclerosis (MS)

A central nervous system disorder characterized by the patchy destruction of myelin sheaths, leading to slowed or blocked nerve impulse conduction.

Chemical Synapse

A synaptic connection that uses chemical neurotransmitters stored in terminal vesicles to carry messages across the synaptic cleft to a receiving cell.

Neuromuscular Junction

A specialized chemical synapse formed between a somatic motor neuron and a target skeletal muscle fiber.

Acetylcholine

The neurotransmitter released at neuromuscular junctions that triggers depolarization and contraction of skeletal muscle fibers.

Acetylcholinesterase

The enzyme present in the synaptic cleft responsible for breaking down acetylcholine to terminate muscle fiber stimulation.

Selective Serotonin Reuptake Inhibitors (SSRIs)

Pharmaceutical drugs that inhibit the reuptake and clearance of serotonin in synaptic clefts, elevating serotonin activity on target cells.

Electrical Synapse

A direct cellular connection using gap junctions that allows electrical current to pass freely between adjacent excitable cells without chemical signaling.

Spinal Cord

A neural column located inside the vertebral column running from the foramen magnum down to the second lumbar vertebra ($L_2$).

Dorsal Horn

The posterior region of internal spinal cord gray matter dedicated to receiving and processing sensory information.

Ventral Horn

The anterior region of internal spinal cord gray matter containing motor neuron cell bodies that send output signals to muscles.

Meninges

The three protective connective tissue coverings—dura mater, arachnoid mater, and pia mater—that encapsulate the central nervous system.

Meningitis

A severe, potentially fatal infection causing inflammation of the protective meninges surrounding the brain and spinal cord.

Cerebral Lobes

The major anatomical subdivisions of the cerebral cortex, comprising the frontal, parietal, occipital, temporal, and insula lobes.

Cerebellum

The 'little brain' structure located posterior to the cerebrum responsible for sensory collection, motor coordination, and maintaining posture and balance.

Brain Stem

The inferior brain region continuous with the spinal cord that monitors and controls essential survival functions including blood pressure, heart rate, and respiration.

Cranial Nerves

Twelve pairs of peripheral nerves originating from the brain and brain stem that carry sensory and motor information for the head, face, neck, and internal organs.

Olfactory Nerve (CN I)

The first cranial nerve, dedicated to conveying sensory input for smell.

Optic Nerve (CN II)

The second cranial nerve, dedicated to conveying sensory input for vision.

Oculomotor Nerve (CN III)

The third cranial nerve, a mixed nerve primarily responsible for motor control of eye movements.

Trochlear Nerve (CN IV)

The fourth cranial nerve, a mixed nerve chiefly motor for controlling eye movements.

Trigeminal Nerve (CN V)

The fifth cranial nerve, a mixed nerve providing sensory input for the face and motor control for chewing.

Abducens Nerve (CN VI)

The sixth cranial nerve, a mixed nerve chiefly motor for eye movements.

Facial Nerve (CN VII)

The seventh cranial nerve, responsible for motor control of facial expressions.

Vestibulocochlear Nerve (CN VIII)

The eighth cranial nerve, responsible for carrying sensory signals for hearing and equilibrium.

Glossopharyngeal Nerve (CN IX)

The ninth cranial nerve, a mixed nerve providing motor output to throat muscles and sensory perception of taste.

Vagus Nerve (CN X)

The tenth cranial nerve, a mixed nerve that conveys autonomic motor control to the heart, lungs, and viscera, as well as sensory input from viscera and taste.

Accessory Nerve (CN XI)

The eleventh cranial nerve, a mixed nerve chiefly motor for the larynx, soft palate, trapezius, and sternocleidomastoid muscles.

Hypoglossal Nerve (CN XII)

The twelfth cranial nerve, chiefly motor for controlling tongue movements.

Reflex

An involuntary, rapid, and protective motor response to a stimulus that can occur automatically through the spinal cord without conscious brain involvement.