Physiology Exam Study Guide: Nervous System and Muscle Physiology

Comprehensive vocabulary flashcards covering human physiology lecture notes on the nervous system, action potentials, synapses, neurotransmitters, brain organization, and skeletal, smooth, and cardiac muscle physiology.

Central Nervous System (CNS)

The brain and spinal cord; functions as the main integration and processing center of the nervous system.

Peripheral Nervous System (PNS)

All nervous tissue outside the CNS, including cranial nerves, spinal nerves, peripheral nerves, ganglia, and sensory receptors; carries sensory input to the CNS and motor output away.

Interneuron

A neuron located primarily within the CNS that integrates information and connects sensory neurons with motor neurons.

Sensory Neuron (Afferent Neuron)

A neuron that carries sensory information from receptors toward the CNS.

Motor Neuron (Efferent Neuron)

A neuron that conveys motor commands away from the CNS to effector organs such as muscles or glands.

Nerve

A bundle of axons located in the Peripheral Nervous System (PNS).

Tract

A bundle of axons located within the Central Nervous System (CNS).

Somatic Motor Nerve

A motor pathway carrying voluntary signals from the CNS to skeletal muscle.

Autonomic Motor Nerve

An involuntary motor pathway sending signals to smooth muscle, cardiac muscle, and glands.

Ganglion

A cluster of neuron cell bodies located in the Peripheral Nervous System (PNS).

Nucleus (Nervous System)

A cluster of neuron cell bodies situated within the Central Nervous System (CNS).

Multipolar Neuron

A neuron characterized by having many dendrites and a single axon extending from the soma.

Bipolar Neuron

A neuron structurally composed of exactly one dendrite and one axon extending from the soma.

Pseudounipolar Neuron

A neuron with a single process leaving the soma that splits into peripheral and central branches.

Neurolemmocytes (Schwann Cells)

Glial cells of the PNS responsible for myelinating peripheral axons.

Satellite Cells

Glial cells in the PNS that surround and provide structural and metabolic support to neuron cell bodies in ganglia.

Oligodendrocytes

Glial cells responsible for forming myelin sheaths around axons within the CNS.

Astrocytes

The most abundant glial cells in the CNS; they support neurons and maintain the chemical environment and blood-brain barrier.

Microglia

Specialized phagocytic, immune defense glial cells resident in the CNS.

Ependymal Cells

Epithelial-like glial cells that line the ventricles of the brain and help produce and circulate cerebrospinal fluid (CSF).

Nodes of Ranvier

Unmyelinated gaps along an axon between adjacent neurolemmocytes/Schwann cells.

White Matter

Regions of the CNS composed mostly of myelinated axon tracts, appearing white due to lipid-rich myelin.

Grey Matter

Regions of the CNS containing neuron cell bodies, dendrites, synapses, unmyelinated axons, and glia.

Resting Membrane Potential

The electrical charge across an axon membrane at rest, typically about $-70\,mV$, established by unequal ion distribution, $K^+$ leak channels, and the $Na^+/K^+$ ATPase.

Electrochemical Gradient

The combined influence of a concentration gradient and the electrical potential difference across a membrane driving ion movement.

Depolarization

A shift in membrane potential toward a less negative/more positive value, primarily caused by $Na^+$ influx.

Repolarization

The return of membrane potential back toward its negative resting level following depolarization, driven primarily by $K^+$ efflux.

Hyperpolarization

A change in membrane potential that makes it more negative than the resting membrane potential, caused by slow-closing voltage-gated $K^+$ channels.

Threshold

The critical membrane potential (typically around $-55\,mV$) required to open voltage-gated $Na^+$ channels and trigger an action potential.

All-or-None Law

The principle stating that an action potential is fully triggered once threshold is reached, or not produced at all if below threshold, without variations in amplitude.

Frequency Modulation

The neural mechanism where stimulus intensity is encoded by the rate or frequency of action potentials rather than their size.

Recruitment

The activation of additional axons, neurons, or motor units in response to an increase in stimulus strength.

Absolute Refractory Period

The interval during which no subsequent action potential can be fired, regardless of stimulus strength, because voltage-gated $Na^+$ channels are open or inactivated.

Relative Refractory Period

The phase following the absolute refractory period when an action potential can occur only if provoked by a stronger-than-normal stimulus.

Saltatory Conduction

The rapid propagation of action potentials along myelinated axons, appearing to leap from one node of Ranvier to the next.

Synapse

A specialized functional junction through which a neuron communicates with another neuron or an effector cell.

SNARE Protein Complex

A set of docking proteins that mediates the fusion of synaptic vesicles with the presynaptic membrane during exocytosis.

Excitatory Postsynaptic Potential (EPSP)

A graded depolarization of the postsynaptic membrane produced when ligand-gated cation channels permit $Na^+$ (and sometimes $Ca^{2+}$) influx.

Inhibitory Postsynaptic Potential (IPSP)

A graded hyperpolarization or stabilization of the postsynaptic membrane caused by $K^+$ outflow or $Cl^-$ influx.

Agonist

A chemical agent that binds to a receptor and stimulates its activity, mimicking or boosting the natural ligand.

Antagonist

A substance that binds to a receptor without activating it, blocking or diminishing the action of the endogenous ligand.

Nicotinic ACh Receptor

A ligand-gated cation channel requiring the binding of two acetylcholine molecules to allow rapid $Na^+$ influx and produce an EPSP.

Muscarinic ACh Receptor

A type of acetylcholine receptor that operates through G-protein coupled cascades and intracellular second messengers.

Acetylcholinesterase (AChE)

An enzyme present within the synaptic cleft that rapidly hydrolyzes acetylcholine to terminate synaptic transmission.

Choroid Plexus

Vascular epithelial structures within brain ventricles that actively and selectively secrete cerebrospinal fluid (CSF) from blood plasma.

Gyri (Gyrus)

Elevated ridges or folds visible on the outer cerebral cortex surface.

Sulci (Sulcus)

Shallow grooves separating individual gyri on the surface of the cerebral cortex.

Precentral Gyrus

The primary motor cortex located in the frontal lobe; contains upper motor neurons controlling voluntary contralateral movement.

Postcentral Gyrus

The primary somatosensory cortex located in the parietal lobe; receives conscious somatosensory input from the contralateral body.

Cerebral Lateralization

The functional specialization and asymmetry between the left and right cerebral hemispheres.

Decussation

The anatomical crossing of nerve tracts from one side of the Central Nervous System to the other.

Broca's Area

A language center located in the frontal lobe (usually left) responsible for speech motor execution and output.

Wernicke's Area

A language center located in the temporal/parietal region (usually left) involved in the comprehension of spoken and written words.

Limbic System

A network of brain structures regulating emotion, motivation, reward, memory, and autonomic endocrine integration.

Hippocampus

A medial temporal lobe limbic structure essential for learning and the consolidation of short-term memories into long-term memories.

Declarative (Explicit) Memory

Memory involving conscious, intentional recollection of factual information and autobiographical events.

Nondeclarative (Implicit) Memory

Memory revealed through behavioral performance rather than conscious recall, including motor skills, habits, and conditioning.

Suprachiasmatic Nucleus (SCN)

A hypothalamic nucleus that serves as the body's master circadian clock, receiving retinal light cues to regulate daily rhythms.

Reticular Activating System (RAS)

A diffuse brainstem network responsible for maintaining cortical alertness, arousal, consciousness, and sleep-wake transitions.

Reflex Arc

The neural circuit underlying a reflex: receptor, sensory neuron, CNS integration center, motor neuron, and effector.

Sarcolemma

The specialized plasma membrane enclosing an individual skeletal muscle fiber.

Sarcomere

The basic contractile functional unit of striated muscle, bounded by two successive Z discs.

I Band

The light region of a sarcomere containing only thin actin filaments, bisected by a Z disc.

A Band

The dark region of a sarcomere extending the entire length of the thick myosin filaments, including overlap zones.

Z Disc

Protein boundary structure anchoring thin filaments and titin at the lateral limits of a sarcomere.

M Line

A protein network at the exact center of the sarcomere that aligns and anchors thick filaments.

H Band

The pale central portion of the A band where thick filaments exist without overlapping thin filaments.

Motor Unit

A single somatic motor neuron along with all the individual skeletal muscle fibers it innervates.

Titin

An immense elastic muscle protein connecting thick filaments to the Z disc, stabilizing thick filaments and providing recoil.

Sliding Filament Theory

The mechanism of contraction wherein thin filaments slide along thick filaments toward the M line, shortening the sarcomere without altering filament lengths.

Power Stroke

The cross-bridge step where the myosin head flexes, pulling actin toward the M line while releasing ADP and inorganic phosphate.

Tropomyosin

A regulatory filamentous protein that blocks the myosin-binding sites on actin when a muscle fiber is relaxed.

Troponin

A three-protein regulatory complex on thin filaments that binds $Ca^{2+}$, causing a conformational movement of tropomyosin to uncover actin active sites.

Sarcoplasmic Reticulum (SR)

A specialized smooth endoplasmic reticulum in muscle fibers dedicated to storing and releasing $Ca^{2+}$ ions.

Transverse Tubules (T Tubules)

Tubular sarcolemmal invaginations that propagate action potentials deep into muscle fibers to trigger $Ca^{2+}$ release from the SR.

SERCA Pump

Sarcoplasmic/endoplasmic reticulum $Ca^{2+}$-ATPase that actively transports cytosolic $Ca^{2+}$ back into the SR lumen to terminate contraction.

Isotonic Contraction

A contraction where muscle tension remains sufficient to move a load while the overall muscle length changes.

Isometric Contraction

A muscle contraction where internal tension is produced without an accompanying change in the external length of the muscle.

Lactate Threshold

The exercise workload at which blood lactate accumulation exceeds clearance, resulting in a persistent upward inflection of lactate levels.

Excess Post-Exercise Oxygen Consumption (EPOC)

Elevated oxygen intake following exercise required to replenish ATP, phosphocreatine, and myoglobin stores, and process metabolic lactate.

Myocardium

The thick middle layer of the heart composed of striated, branched, involuntary, autorhythmic cardiac muscle tissue linked by intercalated discs.