High-Yield Study Guide: Neuro & Muscle

High-yield vocabulary flashcards reviewing essential concepts from neuroanatomy, sensory and autonomic physiology, and skeletal muscle contraction.

Gray Matter

Nervous tissue composed of cell bodies, dendrites, and unmyelinated axons that performs processing functions in the central nervous system.

White Matter

Nervous tissue composed mostly of myelinated axons appearing white due to fatty myelin, functioning as communication highways (tracts).

Nuclei

Clusters of neuronal cell bodies located inside the central nervous system (CNS).

Ganglia

Clusters of neuronal cell bodies located outside the central nervous system in the peripheral nervous system (PNS).

Spinal Cord Segments

The structural divisions of the spinal cord consisting of $8$ Cervical, $12$ Thoracic, $5$ Lumbar, $5$ Sacral, and $1$ Coccygeal segment, each giving rise to a pair of mixed spinal nerves.

Dorsal Root

Spinal root that carries afferent (incoming) sensory signals toward the spinal cord.

Ventral Root

Spinal root that carries efferent (outgoing) motor commands from the spinal cord to target muscles.

Dorsal Root Ganglion

A peripheral nervous system structure that houses sensory neuron cell bodies.

Medulla

Brainstem division containing heart and breathing control centers as well as vomiting, swallowing, coughing, sneezing, and hiccuping reflexes; where $90\%$ of corticospinal tracts decussate (pyramids).

Pons

Brainstem structure that acts as a relay between the cerebellum and cerebrum, and assists the medulla with breathing regulation.

Midbrain

Brainstem division controlling eye movement as well as visual and auditory reflexes; contains the substantia nigra.

Cerebellum

Brain division responsible for coordination, balance, and posture that smooths motor movement and corrects errors.

Reticular Formation (RAS)

A network running through the brainstem that controls arousal, alertness, and consciousness, filters sensory information to the cortex, and helps regulate muscle tone and vital functions.

Thalamus

Diencephalic relay center that sends sensory information from the eyes, ears, and spinal cord to the cerebral cortex, and relays signals from the cerebellum to the motor cortex.

Hypothalamus

Master homeostatic center in the diencephalon regulating blood glucose, body temperature, blood osmolarity, and food intake; directly controls autonomic and endocrine systems.

Basal Ganglia

Subcortical gray matter structures including the globus pallidus, putamen, and caudate nucleus that initiate and stop movement.

Limbic System

Neural network comprising the cingulate gyrus, amygdala, and hippocampus that governs emotions, learning, and memory.

Receptor Potential

A graded electrical potential (also called a generator potential) produced when a sensory receptor transduces a physical stimulus into an electrical signal.

Lateral Inhibition

A sensory processing mechanism that sharpens the spatial accuracy and contrast of stimulus location.

Population Coding

A mechanism by which stimulus intensity is encoded based on the total number of sensory receptors activated.

Frequency Coding

A mechanism by which stimulus intensity is encoded by the firing rate of action potentials.

Sympathetic Nervous System

The fight-or-flight autonomic division originating in the thoracic and lumbar spinal cord, featuring short preganglionic fibers synapsing in chains near the spine and long postganglionic fibers targeting adrenergic receptors.

Parasympathetic Nervous System

The rest-and-digest autonomic division originating in the brainstem and sacral cord, featuring long preganglionic fibers synapsing on or near target organs and short postganglionic fibers targeting muscarinic receptors.

Chromaffin Cells

Modified post-ganglionic sympathetic neurons located in the adrenal medulla.

Sarcolemma

The specialized cell membrane enclosing a skeletal muscle fiber.

Sarcoplasmic Reticulum (SR)

The modified smooth endoplasmic reticulum of muscle fibers specialized for storing and releasing $\text{Ca}^{2+}$.

Tropomyosin

A regulatory filamentous protein that physically covers the myosin-binding sites on actin at rest.

Troponin

A three-part regulatory protein complex consisting of Troponin T (binds tropomyosin), Troponin C (binds $\text{Ca}^{2+}$), and Troponin I (inhibitory; binds to actin).

Titin

A giant elastic spring protein spanning from the Z disk to the M line that stabilizes the thick filament and provides elastic recoil.

Nebulin

An inelastic structural protein that aligns actin filaments and sets the length of the thin filament.

A Band

The dark sarcomere region spanning the full length of the thick filaments, including areas of overlap with thin filaments, which does not change length during contraction.

I Band

The light sarcomere region containing only thin filaments, which shortens during muscle contraction.

H Zone

The lighter central region of the A band containing only thick filaments, which shortens during muscle contraction.

Motor Unit

A single alpha (lower) motor neuron together with all the individual muscle fibers it innervates, contracting simultaneously.

Amyotrophic Lateral Sclerosis (ALS)

A fatal neurodegenerative disease marked by the progressive death of upper and/or lower motor neurons leading to muscle atrophy, weakness, and eventual respiratory failure; approximately $10\%$ of cases are inherited and linked to $SOD1$ mutations.

Myasthenia Gravis

An autoimmune disorder characterized by antibodies attacking nicotinic acetylcholine (ACh) receptors at the neuromuscular junction, leading to degradation of junctional folds and muscle weakness.

DHP Receptor

A voltage-sensing L-type $\text{Ca}^{2+}$ channel in the T-tubule membrane that changes shape in response to an action potential to open the ryanodine receptor.

Ryanodine Receptor (RyR)

A calcium-release channel located on the sarcoplasmic reticulum membrane that releases stored $\text{Ca}^{2+}$ into the cytoplasm when opened by the activated DHP receptor.

SERCA Pump

An ATP-dependent calcium transporter that pumps $\text{Ca}^{2+}$ from the cytoplasm back into the sarcoplasmic reticulum lumen to induce muscle relaxation.

Calsequestrin

A calcium-binding protein located within the sarcoplasmic reticulum that sequesters and holds $\text{Ca}^{2+}$.

Rigor Mortis

A state of sustained muscle stiffness occurring after death due to the lack of ATP required to detach the myosin head from the actin filament.

Type I Muscle Fiber

A slow-oxidative, dark red muscle fiber rich in myoglobin and mitochondria that produces ATP via aerobic metabolism and exhibits high resistance to fatigue.

Type IIX Muscle Fiber

A fast-glycolytic, light/white muscle fiber with few mitochondria that produces ATP rapidly via glycolysis, develops maximum tension fastest, and fatigues rapidly.

Size Principle

The recruitment rule stating that motor units are engaged in order of increasing size: small motor neurons (Type I) first, followed by medium (Type IIA), and finally large (Type IIX) as demand increases.

Muscle Spindle

An intrafusal sensory receptor arranged in parallel with muscle fibers that senses muscle length/stretch and triggers reflexive contraction of the stretched muscle.

Golgi Tendon Organ (GTO)

A sensory receptor arranged in series within tendons that senses muscle tension/force and causes reflexive relaxation (inhibition) of the contracting muscle to prevent tearing.

Alpha-Gamma Coactivation

The simultaneous firing of alpha motor neurons (to extrafusal fibers) and gamma motor neurons (to intrafusal fibers) that prevents the muscle spindle from going slack during contraction.

Crossed Extensor Reflex

A polysynaptic reflex in which painful stimulation induces ipsilateral flexion to pull away while simultaneously stimulating contralateral extension to maintain posture and balance.