bio 150 exam 2

Study guide

Skin and Hair

• Skin functions: Protection from the environment, thermoregulation, sensory function, and vitamin D synthesis.

• Stratum basale: The deepest layer in the epidermis, most active layer for mitosis.

• Dead keratinocytes: Located in the stratum corneum.

• Dendritic cells: Found in the stratum spinosum.

• Keratinocytes’ life cycle: As they progress through layers, their shape changes from cuboidal to squamous, flattening out and losing their nuclei as they reach the surface of the skin.

• Melanin and skin color: Eumelanin (brown to black pigment) and pheomelanin (yellow to red pigment) determine skin color.

• Hair growth stages:

• Anagen: Growth stage (2-7 years).

• Catagen: Degenerative stage (2-3 weeks).

• Telogen: Resting stage (2-4 months).

• Nail growth: Occurs from the basal cells in the nail matrix at the nail root.

• Lunula: White crescent at the proximal end of the nail.

• Eczema: An allergic reaction of unknown origin, presents as dry, itchy, rash-like patches.

Skin Issues and Burns

• Scarring: Fibrosis due to collagen formation instead of regeneration of cells, reducing mobility and normal tissue function.

• Bedsores: Constant pressure on bony areas of the skin decreases blood flow, leading to necrosis and potentially fatal infection.

• Skin cancer:

• Melanoma: Most lethal.

• Basal cell carcinoma: Least lethal.

• Burns:

• First-degree: Involves only the epidermis.

• Second-degree: Involves the epidermis and part of the dermis.

• Third-degree: Involves the entire dermis.

Bones

• Long bone anatomy:

• Shaft: Diaphysis.

• Ends: Epiphysis.

• Periosteum: The outer layer of bone, responsible for healing and connecting bone to other tissues.

• Bone cells:

• Osteogenic cells: Develop into osteoblasts.

• Osteoblasts: Bone formation.

• Osteoclasts: Bone resorption.

• Osteocytes: Bone maintenance.

• Calcium: The primary mineral responsible for bone hardening.

• Nutrient foramina: Small holes in the surface of bones that allow for entry and exit of nerves and blood vessels.

Bone Types:

• Long bones: Longer than wide, with expanded ends (e.g., femur).

• Short bones: Cube-shaped, equal in length and width (e.g., carpals).

• Sesamoid bones: Small and round, embedded in tendons (e.g., patella).

• Flat bones: Thin, wide surfaces, sometimes curved (e.g., sternum).

• Irregular bones: Complex shapes, often articulating with other bones (e.g., vertebrae).

Osteon Structure:

• Lamellae: Rings of calcified matrix surrounding the central canal.

• Central canal: Contains blood vessels, nerves, and lymphatic vessels running up and down the bone.

• Canaliculi: Mini canals that connect lacunae and allow osteocytes to exchange nutrients and waste with the central canal.

Bone Tissue:

• Hemopoietic tissue: Spongy bone contains red bone marrow responsible for blood cell production.

• Endochondral ossification: Forms bone by replacing hyaline cartilage (long bones).

• Intramembranous ossification: Forms flat bones (skull).

Bone Growth:

• Interstitial growth: Bone lengthening through growth at the epiphyseal plate (long bones).

• Appositional growth: Growth in diameter/thickness that occurs throughout life.

Bone Remodeling and Health:

• Osteoclasts: Break down bone to allow for mineral resorption.

• Parathyroid hormone (PTH): Causes the body to break down bone to increase calcium ion levels in the blood.

• Nutrients for bone health: Calcium, Vitamin D, Vitamin K, Magnesium, Fluoride, Omega-3 fatty acids.

Bone Fractures:

• Transverse fracture: Straight across the bone.

• Oblique fracture: At an angle, not 90°.

• Spiral fracture: Results from twisting.

• Comminuted fracture: Several breaks, producing many small pieces.

• Greenstick fracture: Partial fracture, one side of the bone is broken.

• Open (compound) fracture: Breaks through the skin, with a high risk of infection.

• Closed (simple) fracture: Bone breaks but does not penetrate the skin.

Fracture Healing:

• 6-8 hours: Formation of fracture hematoma.

• 48 hours: Internal callus forms inside the bone, external callus forms from periosteal cells.

• Several weeks: Bone resorption occurs, osteoblasts form, and cartilage is replaced by bony trabeculae through ossification.

• 6-8 weeks: Internal and external calli unite, compact bone forms around the edges of the bone, and remodeling begins.

Muscle Characteristics:

• Elasticity: Ability to recoil back to its original length.

• Extensibility: Ability to stretch or extend.

• Contractility: Ability to pull on attachment points and shorten with force.

Muscle Proteins and Sarcomeres:

• Tropomyosin: Blocks the active sites on actin.

• Z-line: Defines the boundaries of a sarcomere.

Muscle Structure:

• Endomysium: Surrounds individual muscle fibers.

• Perimysium: Surrounds groups of muscle fibers (fascicles).

• Epimysium: Surrounds the whole muscle.

Neurotransmitter in Muscle Contraction:

• Acetylcholine (ACh): The neurotransmitter responsible for initiating muscle contractions.

Calcium Storage:

• Sarcoplasmic reticulum: Stores calcium ions in muscle cells.

Types of Paralysis:

• Spastic paralysis: Rigid or stiff paralysis.

• Flaccid paralysis: Loose or floppy paralysis.

Muscle Fiber Types:

• High endurance fibers: Slow-twitch fibers, fatigue-resistant.

• High strength fibers: Fast-twitch fibers, glycolytic.

Resting Potential of Neurons:

• Resting membrane potential: -70 mV.

Muscle Contraction Strength:

• Strength depends on the number of motor units activated at once (recruitment).

Performance-Enhancing Substances:

• Anabolic steroids: Increase muscle mass by boosting testosterone.

• Erythropoietin (EPO): Increases red blood cell count, enhancing oxygen-carrying capacity.

• Human Growth Hormone (HGH): Increases muscle mass and helps heal tissue.

• Creatine: Increases short-term ATP availability.

Muscle Contraction Types:

• Isotonic: Contraction with movement.

• Isometric: Contraction without movement.

Sodium and Potassium in Neurons:

• Potassium concentration: High inside the neuron.

• Sodium concentration: High outside the neuron.

Gated Ion Channels:

• Types of gates: Voltage-gated, ligand-gated, and ATP-gated.

Action Potential Sequence:

• Sodium channels open, allowing Na+ to flow in, then close. Potassium channels open, allowing K+ to exit the cell. Potassium channels stay open until the resting state is restored, then they close.