The Musculoskeletal System and Genetics/Evolution Practice Flashcards

Rhabdomyolysis

A condition caused by the destruction of skeletal muscle tissue, which leads to the release of muscle cell products into the blood.

Creatine kinase

A product of skeletal muscle destruction used to diagnose rhabdomyolysis when levels are five times the normal upper limit.

Myoglobin

An oxygen carrier in muscle that uses heme to carry oxygen and is not housed within a red blood cell.

Hematopoiesis

The production of blood cells, which occurs in the bone marrow.

Skeletal muscle

Muscle responsible for voluntary movement, innervated by the somatic nervous system, and characterized by a striated appearance.

Smooth muscle

Muscle responsible for involuntary movement, controlled by the autonomic nervous system, found in respiratory, digestive, and vascular structures.

Cardiac muscle

The contractile tissue of the heart which is striated, involuntary, and exhibits myogenic activity.

Striations

The striped appearance of certain muscle types (skeletal and cardiac) caused by the arrangement of actin and myosin into sarcomeres.

Sarcomere

The basic contractile unit of skeletal muscle, composed of thick and thin filaments.

Thick filaments

Organized bundles of myosin molecules within the sarcomere.

Thin filaments

Filaments in the sarcomere composed of actin, troponin, and tropomyosin.

Troponin

A protein on the thin filament of muscle that binds calcium to regulate contraction.

Tropomyosin

A protein that wraps around actin and covers myosin-binding sites in the absence of calcium.

Titin

A protein that acts as a spring and anchors actin and myosin filaments together to prevent excessive stretching.

Z-lines

Structures that define the boundaries of each sarcomere.

M-line

The line that runs down the center of the sarcomere, through the middle of the myosin filaments.

I-band

The region of the sarcomere containing exclusively thin filaments.

H-zone

The region of the sarcomere containing exclusively thick filaments.

A-band

The region containing the thick filaments in their entirety, including overlap with thin filaments.

Sarcomere length change: H-zone

Decreases during muscle contraction.

Sarcomere length change: I-band

Decreases during muscle contraction.

Sarcomere length change: A-band

Remains constant during muscle contraction.

Myofibrils

Bundles of sarcomeres attached end-to-end within a muscle cell.

Sarcoplasmic reticulum (SR)

A modified endoplasmic reticulum in muscle cells that contains a high concentration of $Ca^{2+}$ ions.

Sarcoplasm

A modified cytoplasm located just outside the sarcoplasmic reticulum in a myocyte.

Sarcolemma

The cell membrane of a myocyte, capable of propagating an action potential.

Transverse tubules (T-tubules)

A system oriented perpendicularly to myofibrils that distributes action potentials to all sarcomeres.

Muscle fiber

Another name for a myocyte, which contains many myofibrils arranged in parallel.

Neuromuscular junction

The site where the nervous system communicates with muscles via motor neurons.

Motor end plate

The nerve terminal (synaptic bouton) in the context of the neuromuscular junction.

Motor unit

The combination of a single nerve terminal and all the myocytes it controls.

Acetylcholine

The neurotransmitter released at the neuromuscular junction to trigger muscle depolarization.

Sliding filament model

The theory describing how thin filaments slide along thick filaments, causing sarcomere shortening.

Powerstroke

The movement of the myosin head that pulls the actin filament, triggered by the dissociation of $ADP$ and $P_i$ from myosin.

Acetylcholinesterase

The enzyme that degrades acetylcholine in the synapse to terminate the contraction signal.

Rigor mortis

A condition after death where muscles cannot relax because $ATP$ production has ceased, preventing myosin from detaching from actin.

Simple twitch

The response of a single muscle fiber to a brief stimulus at or above threshold.

Latent period

The time between reaching the threshold and the onset of muscle contraction.

Frequency summation

The result of muscle fibers being exposed to frequent stimulation, causing contractions to combine and become stronger.

Tetanus

A state of constant muscle contraction where the muscle is unable to relax at all due to frequent stimulation.

Tetanospasmin

A toxin that blocks the release of GABA, leading to overexcitable motor neurons and constant muscle contraction.

Creatine phosphate

An energy reserve in muscle created by transferring a phosphate group from $ATP$ to creatine during rest.

Oxygen debt

The difference between the amount of oxygen needed by the muscles and the actual amount present.

Red fibers (slow-twitch)

Fibers with high myoglobin content and many mitochondria that primarily derive energy aerobically.

White fibers (fast-twitch)

Fibers with low myoglobin content that contract rapidly and fatigue quickly.

Tonus

A constant state of low-level contraction seen in smooth muscle, particularly in blood vessels.

Myogenic activity

The ability of a muscle cell to contract directly in response to stretch or other stimuli without nervous system input.

Intercalated discs

Connections between cardiac muscle cells that contain gap junctions for rapid ion flow.

Gap junctions

Protein channels between adjacent cells that allow for the flow of ions and coordinated depolarization.

Vagus nerve

The nerve that provides parasympathetic outflow to the heart, slowing the heart rate.

Sinoatrial (SA) node

The starting point of depolarization in the heart's myogenic activity.

Axial skeleton

The central framework of the body consisting of the skull, vertebral column, rib cage, and hyoid bone.

Appendicular skeleton

The bones of the limbs, the pectoral girdle, and the pelvic girdle.

Compact bone

A dense and strong type of bone that provides the characteristic strength of the skeleton.

Spongy (cancellous) bone

Bone with a lattice structure consisting of bony spicules called trabeculae.

Red marrow

Bone marrow filled with hematopoietic stem cells.

Yellow marrow

Bone marrow composed primarily of fat and is relatively inactive.

Diaphyses

The cylindrical shafts of long bones.

Metaphyses

The swelling regions at each end of the diaphysis in long bones.

Epiphyses

The terminal ends of long bones that contain a spongy core for force dispersion.

Epiphyseal plate

A cartilaginous structure at the internal edge of the epiphysis where longitudinal growth occurs.

Periosteum

A fibrous sheath surrounding long bones that protects the bone and serves as a site for muscle attachment.

Tendons

Connective tissue that attaches muscle to bone.

Ligaments

Connective tissue that holds bones together at joints.

Hydroxyapatite

The inorganic crystalline component of bone matrix, formulated as $Ca_{10}(PO_4)_6(OH)_2$.

Osteons (Haversian systems)

The structural units of compact bone consisting of concentric lamellae surrounding a central channel.

Lamellae

Concentric circles of bony matrix within an osteon.

Haversian canals

Longitudinal channels in bone that run parallel to the axis of the bone.

Volkmann’s canals

Transverse channels in bone that run perpendicular to the axis of the bone.

Lacunae

Small spaces between lamellar rings that house mature osteocytes.

Canaliculi

Tiny channels that interconnect lacunae and Haversian/Volkmann’s canals for nutrient/waste exchange.

Osteocytes

Mature bone cells involved in bone maintenance.

Osteoblasts

Cells responsible for building bone.

Osteoclasts

Polynucleated resident macrophages of bone that resorb (break down) bone.

Bone remodeling

The vigorous equilibrium between bone construction by osteoblasts and bone destruction by osteoclasts.

Parathyroid hormone

A peptide hormone that promotes bone resorption to increase blood calcium and phosphate levels.

Calcitonin

A peptide hormone released by the thyroid that promotes bone formation to lower blood calcium levels.

Vitamin D

An activated substance that promotes bone resorption, leading to the growth of new, stronger bone.

Chondrin

The firm but elastic matrix that makes up cartilage.

Chondrocytes

The cells that secrete the chondrin matrix for cartilage.

Endochondral ossification

The process of creating bone by hardening cartilage, typical for most long bones.

Intramembranous ossification

The process where undifferentiated embryonic connective tissue (mesenchymal tissue) is replaced by bone.

Immovable joints

Joints where bones are fused together, such as the sutures in the skull.

Movable joints

Joints that permit bones to shift relative to one another, strengthened by ligaments.

Synovial capsule

A structure that encloses the joint cavity in a movable joint.

Synovium

A layer of soft tissue that secretes synovial fluid.

Synovial fluid

A fluid that lubricates the movement of structures within the joint space.

Articular cartilage

Cartilage that coats the articular surfaces of bones to restrict impact to the lubricated cartilage.

Origin

The end of a muscle with a larger attachment to bone, usually the proximal connection.

Insertion

The end of a muscle with a smaller attachment to bone, usually the distal connection.

Antagonistic pairs

Pairs of muscles where one relaxes while the other contracts (e.g., biceps and triceps).

Synergistic muscles

Muscles that work together to accomplish the same function.

Flexor

A muscle that decreases the angle across a joint.

Extensor

A muscle that increases or straightens the angle across a joint.

Abductor

A muscle that moves a part of the body away from the midline.

Adductor

A muscle that moves a part of the body toward the midline.

Medial rotation

Rotation of the axis of a limb toward the midline.

Lateral rotation

Rotation of the axis of a limb away from the midline.

Genetics

The study of DNA sequences (genes) that code for heritable traits.

Alleles

Alternative forms of a gene.