BIOL 221 Final Exam

• Homeostasis


  Ability to maintain a relatively stable internal environment
• Homeostatic control mechanisms


  • Receptor
  • Control center
  • Effector
• Negative feedback


  Most common homeostatic control mechanism, reverses the direction of change that has occurred in the body
• Negative feedback example


  • You ate 2 doughnuts and drank a Café Mocha for breakfast, blood glucose has increased, pancreas releases insulin to direct muscle and fat cells to remove some glucose from the blood, blood glucose level decreases back to normal range
• Positive feedback


  The output increases the original stimulus
• Positive feedback examples


  • Blood clotting
  • Breast feeding
• Tonicity


  Ability of a solution to cause a cell to shrink or swell, dependent on particles that can't cross the cell membrane
• Types of tonicity


  • Isotonic
  • Hypertonic
  • Hypotonic
• Normally, our red blood cells are in an isotonic solution (0.9% NaCl)
• Red blood cell in isotonic solution

  Retains normal size and shape
• Red blood cell in hypertonic (1.8% NaCl) solution

  Loses water by osmosis and shrinks
• Red blood cell in hypotonic (distilled water) solution

  Takes on water by osmosis until it becomes bloated and bursts (lyses)
• Primary active transport


  Example: Solute pumping, requires enzyme to transport specific substances against their concentration gradient
• Example of primary active transport

  • Na+/K+ pump
• Secondary active transport


  Depends on creation of ion gradient to drive transport of other solutes against their concentration gradient
• Example of secondary active transport

  • Na+ gradient used to move glucose into the cell
• Resting membrane potential

  Voltage difference across a membrane due to separation of ions, ranges from -50 to -100 mV with the interior of the cell membrane being 50-100 mV less than the exterior
• Resting membrane potential results from diffusion and active transport of ions
• Functions of the integumentary system

  • Protection
  • Temperature regulation
  • Synthesis of Vitamin D
  • Sensation
  • Excretion
• Epidermis

  • Stratum corneum
  • Stratum granulosum
  • Stratum spinosum
  • Stratum basale
• Dermis

  • Papillary layer
  • Reticular layer
• Eccrine sweat glands


  Palms, soles, forehead, ducts empty into pores on skin
• Apocrine sweat glands


  Axillary and anogenital areas, become active during puberty, empty into hair follicles
• Sweat


  99% water, contains metabolic wastes, fatty acids and proteins (apocrine only), functions to dissipate excess heat and excrete waste products
• Modified sweat glands


  Cerumenous glands secrete cerumen, mammary glands secrete milk
• Sebaceous glands


  Secrete oily secretion to soften and lubricate hair
• Layers of the Epidermis

  • Stratum basale
  • Stratum lucidum
  • Papillary Layer
  • Reticular Layer
• Stratum basale


  • Deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers; see occasional melanocytes and epidermal dendritic cells
• Stratum lucidum

  Thin, transparent band; consists of a few rows of flat, dead keratinocytes; present only in hairless skin
• Layers of the Dermis

  • Papillary Layer
  • Reticular Layer
• Papillary Layer


  • Composed of areolar connective tissue; fibroblasts; elastic fibers; collagen fibers
• Reticular Layer

  • 80% of the thickness of the skin; dense irregular connective tissue
• Types of Sweat Glands

  • Eccrine sweat glands
  • Apocrine sweat glands
• Eccrine sweat glands


  Palms, soles, forehead; ducts empty into pores on skin
• Apocrine sweat glands

  Axillary and anogenital areas; become active during puberty; empty into hair follicles
• Sweat composition

  99% water; metabolic wastes; fatty acids and proteins (apocrine only); also depends on diet
• Functions of sweat

  • Dissipate excess heat; excrete waste products; acidic nature inhibits bacteria growth
• Modified sweat glands


  • Cerumenous glands
  • Mammary glands
• Cerumenous glands


  Secrete cerumen
• Mammary glands


  Specialized sweat glands that secrete milk