BIO 105: Nervous System Lecture

Comprehensive vocabulary flashcards covering anatomical divisions, cellular structures, action potential electrophysiology, brain regions, and autonomic mechanisms from the BIO 105 nervous system lecture.

Central nervous system (CNS)

The division of the nervous system consisting exclusively of the brain and spinal cord.

Peripheral nervous system (PNS)

All nervous tissue and nerves located outside of the brain and spinal cord.

Afferent nerve

A sensory nerve that carries impulses and sensory information from the peripheral nervous system up into the central nervous system.

Efferent nerve

A motor nerve that carries motor commands and information out of the central nervous system down into the peripheral nervous system to elicit an effect.

Visceral sensory system

The sensory division that monitors and carries signals from internal body organs such as the stomach, pancreas, and intestines.

Somatic sensory system

The sensory division that receives information from the skin, muscles, joints, and special senses.

Somatic motor system

The motor pathway that transmits voluntary signals to control skeletal muscles.

Autonomic nervous system (ANS)

The involuntary division of the motor nervous system that innervates glands, smooth muscle, and cardiac muscle to regulate automatic functions such as heart rate, blood pressure, and digestion.

Sympathetic division

The fight-or-flight division of the autonomic nervous system that prepares the body to escape or handle stressful, threatening situations.

Parasympathetic division

The rest-and-digest division of the autonomic nervous system that oversees routine, calming bodily functions between stressful episodes.

Neurons

The primary cells of the nervous system responsible for transmitting electrical nerve impulses.

Neuroglia

Non-conducting support cells in the nervous system that nourish, protect, and hold neurons in place, occurring in roughly a $9$ to $1$ ratio to neurons in the brain.

Microglia

Phagocytic glial cells of the central nervous system that clear away debris, dead cells, and bacteria through phagocytosis.

Astrocytes

Star-shaped central nervous system neuroglia that offer structural support and provide nutrients such as glucose to neurons.

Oligodendrocytes

Central nervous system glial cells with octopus-like branching processes that wrap around multiple axons to form myelin sheaths.

Schwann cells

Peripheral nervous system glial cells that wrap individually along the length of an axon to form its myelin sheath.

Myelin sheath

A white, lipid-rich insulating coating wrapped around axons that accelerates nerve signal conduction up to $300\,\text{mph}$.

Nodes of Ranvier

Unmyelinated gaps along an axon between adjacent Schwann cells that facilitate rapid electrical impulse transmission.

Interneuron

A neuron located exclusively within the central nervous system (commonly in the spinal cord gray matter) that bridges the communication between a sensory neuron and a motor neuron.

Dendrites

Branching extensions attached to the neuronal cell body that receive incoming signals from sensory receptors or neighboring neurons.

Axon

A single long nerve fiber that conducts electrical impulses away from the neuron cell body toward axon terminals.

White matter

Nervous tissue characterized by dense bundles of myelinated axons, appearing white due to lipid content.

Gray matter

Nervous tissue composed primarily of neuronal cell bodies, dendrites, and unmyelinated axons.

Resting membrane potential

The electrical charge across an inactive neuron's plasma membrane, established at $-70\,\text{mV}$ due to uneven ion distributions.

Sodium-potassium pump

An ATP-dependent transport protein that maintains the resting membrane potential by pumping $3$ sodium ions ($\text{Na}^+$) out of the cell for every $2$ potassium ions ($\text{K}^+$) brought inside.

Threshold

The minimum membrane potential level of approximately $-55\,\text{mV}$ that must be attained to initiate an action potential.

Depolarization

The phase of an action potential in which sodium channels open and positive sodium ions rush into the axon, elevating membrane potential to $+35\,\text{mV}$.

Repolarization

The phase of an action potential during which sodium channels close and potassium channels open, allowing positive potassium ions to exit and restoring the membrane potential toward $-70\,\text{mV}$.

Refractory period

A brief recovery period following an action potential during which sodium gates cannot open, ensuring unidirectional impulse propagation along the axon.

Synaptic cleft

The minute extracellular fluid-filled space that separates a presynaptic axon terminal from a postsynaptic cell.

Neurotransmitter

A chemical messenger stored in synaptic vesicles and discharged across the synaptic cleft to bind specific receptors on the postsynaptic membrane.

GABA

The chief inhibitory neurotransmitter within the brain that decreases neuronal excitability and induces drowsiness or relaxation.

Meninges

Multiple layers of protective membranes enveloping both the brain and the spinal cord.

Ventricles

Interconnected chambers within the brain that house specialized cells dedicated to producing cerebrospinal fluid.

Cerebrospinal fluid (CSF)

A fluid circulating within brain ventricles and around meningeal spaces that cushions, protects, and supports the central nervous system.

Dorsal root

The posterior nerve root entering the spinal cord that is composed exclusively of sensory fibers.

Ventral root

The anterior nerve root emerging from the spinal cord that is composed exclusively of motor fibers.

Dorsal root ganglion (DRG)

An enlarged nodule situated on the dorsal root of each spinal nerve containing the cell bodies of sensory neurons.

Corpus callosum

A prominent band of white matter tracts that bridges the right and left cerebral hemispheres, permitting interhemispheric communication.

Longitudinal fissure

The deep sagittal groove dividing the cerebrum into right and left halves.

Sulci and gyri

The surface convolutions of the cerebral cortex, where sulci represent grooves and gyri represent elevated folds or ridges.

Primary motor area

A strip of cerebral cortex situated in the frontal lobe immediately anterior to the central sulcus that commands voluntary skeletal muscle contractions.

Somatosensory area

A cortical region located in the parietal lobe immediately posterior to the central sulcus that interprets sensory information from the skin and skeletal muscles.

Prefrontal area

An anterior region of the frontal lobe that executes higher-order cognitive functions such as planning, critical thinking, decision making, and judgment.

Broca's area

A specialized motor speech area of the brain that coordinates the muscular movements essential for speaking and writing.

Wernicke's area

A brain association region dedicated to processing, interpreting, and comprehending written and spoken language.

Hypothalamus

A diencephalic regulatory center that acts as an internal clock, oversees autonomic balance, controls body temperature, hunger, and thirst, and couples the nervous system to the endocrine system via the pituitary gland.

Thalamus

A large diencephalic relay station that sorts and directs incoming sensory impulses (excluding smell) to appropriate regions of the cerebral cortex.

Pineal gland

A diencephalic endocrine structure that secretes melatonin to govern the circadian rhythm and sleep-wake cycles.

Cerebellum

The posterior brain structure located beneath the occipital lobe that coordinates balance, posture, and smooth voluntary movements.

Arbor vitae

The distinctive tree-like internal branching pattern of white matter tracts found within the cerebellum.

Medulla oblongata

The most inferior segment of the brainstem that oversees vital autonomic functions like heart rate, breathing, blood pressure, vessel constriction, and digestive reflexes.

Hippocampus

A key component of the limbic system that serves as the major center for memory formation and learning.

Cranial nerves

Twelve ($12$) pairs of peripheral nerves designated by Roman numerals that originate directly from the brain.

Vagus nerve

Cranial nerve $10$ ($\text{X}$), an extensive autonomic nerve that innervates key internal viscera including the heart, lungs, and digestive organs.

Spinal nerves

Thirty-one ($31$) pairs of mixed peripheral nerves that emerge from the spinal cord carrying both sensory and motor axons.

Norepinephrine

The principal fight-or-flight neurotransmitter released by sympathetic postganglionic fibers to elevate heart rate, respiratory rate, and blood pressure during stress.

Acetylcholine

The primary neurotransmitter employed by the parasympathetic nervous system to promote calming, restorative rest-and-digest actions.