Histology Quiz 4 (p 19-23)

Muscle Physiology

• The atrioventricular delay is contributed to by slow-response myocytes.
• Not all muscles are controlled by one nerve cell.
• The most common free nerve endings are found in the dermis.
• Each hair follicle receives blood from one source, not two.

Muscle Contraction

• The term used for the enlargement of a muscle is hypertrophy.
• Calcium ions are responsible for exposing the binding sites in the actin filament during muscle contraction.
• Creatine phosphate is the molecule responsible for storing ATP energy in muscle cells.
• Disuse or denervation can cause muscle atrophy.
• The main factor that causes muscle fatigue is the depletion of ATP and phosphocreatine.
• The term for the sustained contraction of a muscle resulting from a rapid succession of nerve impulses is tetany.

Motor Unit

• The motor unit with the highest ratio is the eye muscle.

Bone Composition

• Calcium, phosphate, and hydroxide ions are present in significant amounts in bone mineral.
• Magnesium and sodium have a role in bone mineral, but they are not as prominent as calcium.
• Strontium and radium isotopes can substitute for stable isotopes in the hydroxyapatite crystal.
• Lead, radium, and strontium can substitute for calcium in bone if ingested.

Bone Development

• During growth, the amount of organic material and water in bone decreases.
• Inorganic minerals make up 65% of fat-free dry weight in adults.
• Osteoblasts, osteoclasts, and osteocytes are derived from embryonic mesenchymal cells and persist throughout postnatal life.
• The main function of osteoblasts is to produce bone matrix.
• Osteocytes reside within the lacunae of bone.
• The main function of osteoclasts is to break down bone matrix.

Bone Structure

• The interstitial substance of bone is composed of ground substance and fibers.
• The main component of the organic portion of the bone matrix is collagen.
• The type of contraction that produces movement is isotonic contraction.

Bone Functions

• The functions of bones include support, protection, movement, and blood cell formation.
• The structure of compact bone is a dense, compact arrangement of Haversian systems.
• Osteocalcin is involved in the regulation of bone mineralization.
• Spongy bone is composed of trabeculae and interstitial substance.
• The trabeculae of spongy bone are organized in a way that maximizes strength and minimizes weight.