Exam III Study Guide - Biology 275

Spongy Bone

Located within the interior of a bone, contains a latticework structure of bone connective tissue, appears porous, makes up 20% of total bone mass.

Compact Bone

Appears solid but is perforated by neurovascular canals, formed from cylindrical structures called osteons, makes up 80% of total bone mass.

Red Bone Marrow

Contains reticular connective tissue, developing blood cells, and adipocytes, widely distributed in children, located in the spongy bone of most bones and medullary cavity of long bones.

Yellow Bone Marrow

Fatty appearing substance found in adults, adults have red bone marrow in selected portions of the axial skeleton and proximal epiphysis of each humerus and femur.

Periosteum

Covers the outer surface of the bone, outer fibrous layer protects the bone, inner circular layer includes osteoprogenitor cells, osteoblasts, and osteoclasts.

Endosteum

Thin layer of connective tissue containing osteoprogenitor cells, osteoblasts, and osteoclasts, covers internal surfaces of bone within the medullary cavity.

Interstitial Growth

Increase in length that occurs within the internal regions of cartilage, stimulated by chondrocytes undergoing rapid mitosis.

Appositional Growth

Increase in width along the periphery of cartilage, stimulated by stem cells dividing and differentiating into chondroblasts.

Intramembranous Ossification

Bone formation within a membrane, formation of flat bones of the skull, begins with mesenchyme becoming thickened and condensed with a dense supply of blood capillaries.

Endochondral Ossification

Bone formation that begins with a hyaline cartilage model, produces most bones of the skeleton, involves the formation of primary and secondary ossification centers.

Zones of Growth at the Epiphyseal Plate

Zone of Resting Cartilage, Zone of Proliferating Cartilage, Zone of Hypertrophic Cartilage, Zone of Calcified Cartilage, Zone of Ossification.

Long Bone Increases in Width

Osteoblasts in the periosteum produce and deposit bone matrix within layers parallel to the surface, osteoclasts resorb some bone matrix along the medullary cavity, continues throughout an individual's lifetime.

Hormones on Bone Growth and Remodeling

Growth Hormone, Thyroid Hormone, Calcitonin, Sex Hormones, Parathyroid Hormone, Calcitriol, Glucocorticoids, Serotonin.

Fracture Repair

Fracture Hematoma, Fibrocartilaginous Callus, Hard Callus, Bone Remodeling.

Types of Fractures

Simple, Compound, Stress, Pathological.

Classes of Bones

Long Bone, Short Bone, Flat Bone, Irregular Bone.

Vitamins

Vitamin C, Vitamin D.

Bone Functions

Support and Protection, Levers for Movement, Hematopoiesis, Storage of Mineral and Energy Reserves.

Tendon

Thick, cordlike structure composed of dense regular connective tissue, attaches a muscle to a skeletal component or fascia.

Aponeurosis

Thin, flattened sheet of dense regular connective tissue, attaches a muscle to a skeletal component or fascia.

Connectin

Skeletal muscle fiber elasticity, stabilizes the position of the thick filament within a sarcomere.

Dystrophin

Part of a protein complex that anchors myofibrils to proteins within the sarcolemma, links internal myofilaments to external proteins.

Epimysium

Layer of dense irregular connective tissue that surrounds the whole skeletal muscle.

Perimysium

Layer of dense irregular connective tissue that surrounds each fascicle.

Endomysium

Composed of areolar connective tissue that surrounds each muscle fiber. Function to electrically insulate the muscle fibers.

Fast Fibers

Most prevalent, largest in diameter. Contain fast myosin ATPase but can only contract for short bursts because ATP is provided through glycolysis.

Slow Fibers

Half the diameter of other skeletal muscle fibers. Contain slow myosin ATPase producing slower and less powerful contractions. Can contract over longer periods without getting fatigued as ATP is supplied through aerobic cellular respiration.

Intermediate Fibers

Least numerous and intermediate in size. Contain fast myosin ATPase and produce a fast and powerful contraction with ATP provided primarily through aerobic cellular respiration. Delivery of nutrients and oxygen is lower as it has a less extensive capillary network.

Oxidative Fibers

Specialize in providing ATP through aerobic cellular respiration. Extensive capillary network. Large numbers of mitochondria and myoglobin. Fatigue-resistant.

Glycolytic Fibers

Specialize in providing ATP through glycolysis. Less extensive capillary network. Fewer mitochondria and myoglobin. Fatigable.

Skeletal Muscle Contraction

The anatomic structures and associated physiological processes of skeletal muscle contraction include the events that occur at the neuromuscular junction, sarcolemma, T-tubules, sarcoplasmic reticulum, and sarcomeres.

Neuromuscular Junction, Excitation of a Skeletal Muscle Fiber

Release of neurotransmitter ACh from synaptic vesicle excites the skeletal muscle fiber.

Sarcolemma, T-tubules, and Sarcoplasmic Reticulum, Excitation-contraction Coupling

ACh binding triggers propagation of an action potential along the sarcolemma and T-tubules to the sarcoplasmic reticulum, which is stimulated to release calcium.

Sarcomere, Crossbridge Cycling

Sarcomeres shorten and the skeletal muscle fiber contracts.

Muscle Twitch

A single, brief contraction period and then relaxation period of a skeletal muscle in response to a single stimulation.

Subthreshold Stimulus

Minimum voltage needed to stimulate the skeletal muscle to generate a muscle twitch.

Latent Period

The time elapsed between stimulation of the muscle fiber and the generation of a contractile force.

Contraction Period

Repetitive power strokes pull the thin filaments past the thick filaments, shortening sarcomeres. Tension increases.

Relaxation Period

Release of crossbridges as calcium is returned to the sarcoplasmic reticulum. Tension decreases. Depends upon elasticity of connectin.

Wave Summation

Occurs in skeletal muscle during repetitive stimulation. Happens after an action potential arrives at the muscle fiber before the relaxation phase of muscle contraction is complete.

Incomplete Tetany

The muscle fiber has partially relaxed before the arrival of the next stimulus. The individual twitches or contractions can be observed separately, and there is a partial relaxation between them. This allows the muscle to partially recover and prevents sustained contraction.

Tetany

If the frequency of stimulation is high enough, the muscle does not have time to relax between stimuli. The individual twitches fuse into a sustained contraction, and the muscle does not return to its resting state. This type of contraction is more forceful and sustained compared to incomplete tetanus.

Skeletal Muscle Relaxation

Termination of rapid nerve signals propagated along the motor neuron, when it stops ACh is no longer released. ACh is hydrolyzed by acetylcholinesterase. ACh receptors close, end-plate potentials at the motor end plate and the action potentials along the sarcolemma and T-tubules cease. Calcium channels return to their original position. Calcium is returned to the terminal cisternae by pumps and returned to its storage within the sarcoplasmic reticulum. Troponin returns to its original shape when calcium is removed, with tropomyosin being simultaneously moved over to myosin binding sites on actin - prevents crossbridge formation. Muscle returns to its original position from the release of tension in connectin (springs).

Parts of a Neuromuscular Junction

Excitation of a Skeletal Muscle Fiber. The first physiologic event of skeletal muscle contraction.

Calcium Entry at Synaptic Knob

A nerve signal is sent along a motor neuron. The nerve signal triggers the opening of voltage-gated calcium channels within the synaptic knob and calcium moves down its gradient.

Release of ACh from Synaptic Knob

The binding of calcium to synaptic vesicles triggers the merging of synaptic vesicles with the synaptic knob. Exocytosis of ACh into synaptic cleft.

Binding

Wheelbarrow lever

Lifting the handles of a wheelbarrow allows it to pivot on its wheel and lift a load in the middle. The lifting motion is the effort.

Mechanical advantage

A small force can balance a larger weight in this type of lever because the effort is always farther from the fulcrum than the resistance.

Plantar-flexion

The contraction of the calf muscle causes a pull superiorly by the calcaneal tendon attached to the heel, resulting in the foot being on "tippy-toes."

Third-Class Levers

Levers where the effort is in the middle between the resistance and the fulcrum.

Forceps

Picking up a small object with a pair of forceps is an example of a third-class lever.

Elbow lever

In the body, the elbow acts as a fulcrum, the effort is applied by the biceps brachii muscle at its attachment to the radius, and the resistance is provided by any weight in the hand or the weight of the forearm itself.

Mandible lever

In the body, the temporomandibular joint acts as the fulcrum, the effort is exerted by the temporalis muscle, and the resistance is the food being bitten.