D’YOUVILLE COLLEGE
BIOLOGY 659 - INTERMEDIATE PHYSIOLOGY I
INTRODUCTION, HOMEOSTASIS
1.
Introduction: (chapter 1)
• cells – occupy central position in hierarchy of living systems (consult any A & P
text): atoms, molecules & ions, macromolecules, organelles, cells, tissues, organs,
organ systems, organism (ppt. 1)
- trillions of cells include wide variety of different types (e.g. epithelial cell,
neuron, muscle fiber, osteocyte, fibroblast); comprise four different tissue types (ppt. 2)
- cells all share common needs: need nutrients supplied: oxygen, glucose,
certain ions, amino acids, fats; also need wastes removed: carbon dioxide, nitrogenous
wastes
2.
Internal Environment:
• extracellular fluid (ECF – includes interstitial fluid & plasma) differs from
intracellular fluid (ICF): ECF contains oxygen, nutrients, carbon dioxide & electrolytes –
mainly sodium, chloride, & bicarbonate (table 1 - 1); ICF contains metabolites of
nutrients, proteins & electrolytes – mainly potassium, magnesium, & phosphate
3.
Homeostasis:
• maintenance of constant composition (basis of virtually all physiology)
• contributions of various systems to homeostasis:
- circulation and microcirculation of blood: cardiovascular system
distributes plasma – borne nutrients + red cells (with oxygen) to all parts of body &
delivers plasma – borne waste products to organs for their disposal (e.g., carbon
dioxide to lungs) (fig. 1 – 1 & ppt. 3); microcirculation carries on exchange with
interstitial fluid surrounding cells (fig. 1 – 2 & ppts. 4 & 5)
Bio 659 lec 1
- p. 2 -
Bio 659 lec 1
- p. 3 -
- hemoglobin & bicarbonate ion buffer each other to facilitate appropriate gas
exchange (both in lungs and in tissues) (ppt. 6)
- respiratory system: lungs take up oxygen (that is bound by hemoglobin) &
remove carbon dioxide
- digestive system: acquires nutrients & disposes of certain wastes
- renal system: removal of wastes, excesses (electrolyte & acid-base balance)
- musculoskeletal: locomotion (escape from hostile environments; access to
amicable environments)
- reproduction: cell growth & replacement or production of new generations
(organisms)
Bio 659 lec 1
- p. 4 -
• nervous & endocrine systems regulate activities of other systems via reflexes
Bio 659 lec 1
4.
- p. 5 -
Control Systems:
• negative feedback (principle feature of most control systems) – response of
living system offsets stimulus (ppt. 7), e.g. baroreceptor reflex (ppt. 8),
thermoregulation (ppt. 9), insulin & glucagon regulation of blood sugar (endocrine
reflex) (ppt. 10), renin-angiotensin system (ppt. 11), chemoreceptor reflex
• positive feedback - sometimes beneficial, e.g. blood clotting (ppt. 12),
childbirth
- usually harmful – ‘vicious cycle’ may develop, e.g. hemorrhage and declining
cardiac output may cause death (fig. 1 – 3 & ppt. 13)