Final Study Guide

Unicellular exocrine gland

Goblet cells — embedded in mucous membranes of respiratory & digestive tracts; NOT a multicellular gland

Cilia (epithelial)

Motile, hair-like apical extensions that move mucus/fluid

Collagen fibers (connective tissue)

High tensile strength, weight-for-weight comparable to steel, due to triple-helix structure

Keratin family of proteins

Found in epidermis (keratinocytes), hair, AND nails — unifies all three structures

Eccrine (merocrine) glands

Simple coiled tubular glands; produce watery sweat for thermoregulation

Apocrine glands

Larger glands in axilla/groin, activate at puberty; produce viscous secretion (body odor via bacteria), NOT for thermoregulation

Scabies

Caused by Sarcoptes scabiei mite; intensely itchy, red linear burrow tracks between fingers; common in close-contact settings

Fibrocartilage locations

Intervertebral discs, menisci of the knee, pubic symphysis

Hyaline cartilage locations

Nose, costal cartilage (NOT epiglottis)

Elastic cartilage locations

External ear, epiglottis

Sharpey's (perforating) fibers

Collagen bundles anchoring the periosteum to underlying bone matrix

Iliosacral (sacroiliac) ligament

Stabilizes the sacroiliac joint, connects ilium to sacrum

Sternocleidomastoid origin/insertion

Origin = sternum & clavicle; insertion = mastoid process

Osteomalacia

Defective bone mineralization ("adult rickets")

Osteoporosis

Decreased bone density/mass with normal mineralization ratio

Osteogenesis imperfecta

"Brittle bone disease" — genetic collagen defect, disorganized bone on histology

Paget's disease

Excessive/disorganized bone remodeling

Adductor magnus action

Adducts, flexes, and extends the thigh

Latissimus dorsi action

Extends, adducts, and medially rotates the arm

Vastus lateralis action

Extends the leg at the knee

Biceps femoris action

Flexes the knee, extends the thigh (part of hamstrings)

Triceps brachii action

Extends the forearm at the elbow

Symphysis joints

Fibrocartilage pad joints (e.g. pubic symphysis, intervertebral discs) — cartilaginous joint type

Synchondroses

Hyaline cartilage joints (e.g. epiphyseal plates, first sternocostal joint) — primary cartilaginous joint

Skeletal muscle features

Voluntary, multinucleated, striated, NO gap junctions, develops via myoblast fusion

Cardiac muscle features

Involuntary, single-nucleated, striated, autorhythmic, has gap junctions (intercalated discs)

Smooth muscle features

Involuntary, single-nucleated, non-striated; does NOT develop via myoblast fusion

Intercalated discs

Contain desmosomes and gap junctions; found ONLY in cardiac muscle

Varicosities

Found in smooth muscle instead of a classic neuromuscular junction

Visceral (single-unit) smooth muscle

Involuntary, non-branching, no sarcomeres, gap junctions present, autorhythmic; found in digestive tract, uterus

Multiunit smooth muscle

Single innervation per cell, non-branching, no sarcomeres, gap junctions absent/minimal, NOT autorhythmic; found in iris, large arteries

Endomysium

Innermost muscle connective tissue layer, wraps individual muscle fibers

Perimysium

Middle muscle connective tissue layer, wraps muscle fascicles (NOT a cardiac muscle feature)

Epimysium

Outermost muscle connective tissue layer, wraps the entire muscle

Muscle lever class

Most muscles act as 3rd-class levers — effort between fulcrum and load, prioritizes speed/ROM over force

Sarcoplasm

The cytoplasm of a muscle fiber

Titin

Giant elastic protein spanning Z-disc to M-line; anchors myosin, provides passive tension and elastic recoil

Z-disc

Sarcomere boundary; anchors thin (actin) filaments

Sarcoplasmic reticulum function

Stores and releases Ca2+ via terminal cisternae flanking T-tubules

SERCA

Ion pump that pumps Ca2+ back into the sarcoplasmic reticulum

Sliding filament sequence

Ca2+ released from SR → binds troponin on thin filament → tropomyosin shifts → exposes myosin-binding sites on actin → cross-bridge cycling

Skeletal/cardiac structural anchor vs smooth

Z-discs (skeletal/cardiac) vs. dense bodies (smooth)

Skeletal/cardiac calcium sensor vs smooth

Troponin (skeletal/cardiac) vs. calmodulin (smooth, no troponin)

Contraction physiological sequence

Lower motor neuron releases ACh at NMJ → binds nicotinic receptors on sarcolemma → depolarization → AP travels T-tubules → SR releases Ca2+ → contraction

ACh release for skeletal contraction

Released specifically by lower motor neurons of the spinal cord, NOT upper motor neurons or motor cortex neurons

Botulinum toxin mechanism

Prevents ACh release at the presynaptic NMJ → flaccid paralysis; used therapeutically for spasms, hyperhidrosis, migraines

Tetanus toxin mechanism

Blocks GABA (and glycine) release in the spinal cord → sustained/spastic muscle contraction

Myasthenia gravis mechanism

Autoimmune destruction of postsynaptic nicotinic ACh receptors at the NMJ → muscle weakness; treated with neostigmine, sometimes thymectomy

Isometric contraction

Muscle generates tension without changing length

Isotonic contraction

Muscle changes length and shortens during contraction

Absolute refractory period mechanism

Na+ channels are inactivated (not simply "reset"); no stimulus can trigger another contraction/AP

Treppe (staircase effect)

Gradual increase in contraction force with repeated fixed submaximal stimuli, driven by rising intracellular Ca2+ before fatigue

Phosphagen system

Creatine phosphate + ATP; immediate energy source, used during first 10-15 seconds of intense activity

Rigor mortis mechanism

Total ATP depletion after death → myosin cross-bridges cannot detach from actin; peaks ~12-24 hours postmortem

Fast glycolytic (Type IIx) fibers

Large diameter, LOW myoglobin, LOW mitochondria, fatigue quickly, best for sprinters

Slow oxidative fibers

HIGH myoglobin, HIGH mitochondria, high fatigue resistance, optimized for endurance

Dense bodies (smooth muscle)

Anchor actin filaments; functional analog of Z-discs in striated muscle

Calmodulin

Calcium-binding protein that activates smooth muscle contraction (smooth muscle lacks troponin)

Duchenne muscular dystrophy

X-linked single-gene defect, primarily affects males

Oligodendrocytes

CNS glia that myelinate axons; one cell extends processes to multiple different axons

Microglia

CNS immune/phagocytic cells; clear debris, respond to infection

Astrocytes

CNS glia providing structural support; help form/maintain the blood-brain barrier

Schwann cells

PNS glia that myelinate axons; one Schwann cell wraps only one axon segment (one per internode)

Satellite cells

Surround/support neuron cell bodies in PNS ganglia; do NOT provide myelin

PNS axon regeneration

CAN regenerate — Schwann cells proliferate, form a regeneration tube guiding regrowth

CNS axon regeneration

Generally CANNOT regenerate — oligodendrocytes and astrocytic scar tissue inhibit regrowth

Nissl substance

Rough endoplasmic reticulum in the neuron cell body; site of protein synthesis

White matter composition

Mostly myelinated axons; does NOT contain neuron cell bodies

Gray matter composition

Contains neuron cell bodies

Multipolar neurons

Account for >95% of all neurons in the CNS

Unipolar sensory neuron cell bodies

Located inside the dorsal root ganglia

Interneurons

Neurons located entirely within the CNS; structurally connect sensory and motor pathways

Anterograde axonal transport

Powered by kinesin; moves materials away from cell body toward axon terminal

Retrograde axonal transport

Powered by dynein; moves materials back toward the cell body

Type A axon fibers

Myelinated, largest diameter, fastest conduction

Type B axon fibers

Myelinated, intermediate diameter and speed

Type C axon fibers

UNMYELINATED — the only unmyelinated class; smallest diameter, slowest speed

Saltatory conduction

Action potential "jumps" between Nodes of Ranvier on myelinated axons, speeding conduction

Absolute refractory period (neuron)

Voltage-gated Na+ channels are inactivated; no stimulus can trigger another AP regardless of strength

Renshaw cells

Inhibitory interneurons providing recurrent (negative feedback) inhibition onto motor neurons

Myasthenia gravis receptor target

Nicotinic ACh receptors at the NMJ (not muscarinic)

Alzheimer's disease mechanism

Deficit in central cholinergic transmission impacting memory; treated with acetylcholinesterase inhibitors like donepezil (act centrally)

Ionotropic receptors (fast/direct)

Directly open ion channels; examples: ACh (nicotinic), glutamate

Metabotropic receptors (slow/modulatory)

Act through G-protein coupled receptors; examples: dopamine, norepinephrine, epinephrine, serotonin, GABA

Glutamate (NT localization)

Main excitatory neurotransmitter of the cerebellum

GABA (NT localization)

Main inhibitory neurotransmitter of the brain overall

Glycine (NT localization)

Inhibitory neurotransmitter mainly in the spinal cord

Dopamine pathway

Substantia nigra neurons communicate with basal ganglia via the nigrostriatal pathway; degeneration causes Parkinson's disease

Atropine

Muscarinic antagonist (blocks muscarinic ACh receptors only, not nicotinic)

Bethanechol

Muscarinic agonist (opposite of atropine)

Motor cortex location

Precentral gyrus

Wernicke's area

Responsible for language comprehension; typically left hemisphere in most people (including most left-handers)

Temporal lobe function

Auditory processing and memory — damage does NOT typically cause blindness

Occipital lobe function

Houses the visual cortex, handles vision

Substantia nigra location

Midbrain (part of the brainstem)

Corpora quadrigemina

Midbrain structure; superior/inferior colliculi, visual/auditory reflex centers

Medulla oblongata functions

Cranial nerve nuclei, respiratory center, connects cerebellar hemispheres via commissural fibers

Decussation of pyramids

Crossing point of corticospinal tract fibers, at the medulla-spinal cord junction

Circumventricular organs (CVOs)

Brain regions lacking a complete blood-brain barrier (e.g. area postrema, subfornical organ, OVLT)

Arbor vitae

Branching, tree-like pattern of white matter in cerebellar cross-section