Homeostasis

• What is homeostasis?

  The maintenance of a relatively constant internal environment, steady state.
• What is the plasma potassium concentration?

  Normal plasma K+= 3.5-4.5mM

  Hyperkalaemia = K+ > 5.0mM

  Above 6.5mM this is a medical emergency
• What is the body composition in a 22 yr old male.

  Water 61%

  Protein 16.8%

  Fat 16.6%

  Minerals 4.5%

  Carbohydrate 0.7%/Nucleic acid 0.4%
• What is the percentage of the fluid inside the body?

  Intracellular water 66.7%- 28 litres

  (Interstitial water 24.7%- 10.4 litres

  Plasma 6.7%- 2.8 Litres

  Transcellular water 1.9%- 0.8 litres) - extracellular water (14 litres)
• What is regulated/nonregulated variable?

  Regulated- sensor exists to keep variable within limits/body controls to keep within range e.g. temperature, pressure

  Nonregulated- can change to achieve control of regulated variable/fluctuates e.g. heart rate, hormones
• An example of negative feedback:

  1. Starts at sensors: Carotid and aortic Baroreceptors
  2. Nucleus of tractus solitarius (brainstem)
  3. Effectors: Cardiac muscle increase CO2, smooth muscle vasoconstriction
  4. Back to normal blood pressure 120/80
• What happens when someone has a fever (Pyrexia)

  1. Bacteria (Pyrogens), CKS interacts with organum vasculosum of the lamina terminalis (front of hypothalamus controls temp)
  2. Stimulate production of PGE2
  3. PGE2 inhibits warm neurons in the hypothalamus and blood temperature increases.
• Give an example of positive feedback:

  1. Uterus contracts
  2. Foetus presses on cervix
  3. Signal to hypothalamus
  4. More oxytocin by posterior pituitary
  5. Back to 1. more contraction
  6. Birth of baby
• What is feedforward?

  Anticipatory behaviour- e.g. smell food before eating stimulates enzymes, this minimises disruption to set points.
• What is anatomy, physiology, physiological, pathalogy?

  Anatomy- Physical structure of organism parts

  Physiology- functioning of organisms, processes of all part of organism

  Physiological- normal healthy functioning

  Pathology/pathological- branch of medicine concerned with the cause, origin and nature of disease, and changes in tissues/organs.
• What internal fluid compartments is the body composed of?

  Total body volume (60-80 litres):

  Total body water (40-50), '

  Intracellular fluid (28-30),

  Extracellular fluid (14-15): Plasma in blood (3), interstitial fluid (11).
• What are the 4 tissues with its functions?

  Epithelial tissue- exposed surfaces, lines internal passageways and chambers, produces glandular secretions.

  Connective tissue- fills internal spaces, provides structural support, stores energy.

  Muscle tissue- contracts to produce movement

  Nervous tissue- electrical impulses, carries information.
• What are the 4 types of cells that is divided from the 200 cell types?

  Neural- excitable signalling cells

  Muscle- excitable contractile cells

  Epithelial- sheet like external body covering, internal cavity linings and renal tubules, specialised endocrine cells (hormones)

  Connective tissue cells- cells found in blood, lymph, fat, tendons, bone.
• What are simple epithelial cells?

  ingle layer of cells,

  Simple Squamous: Thin, flat cells; ideal for diffusion (e.g., lungs, blood vessels)

  Simple Cuboidal: Cube-shaped cells; involved in secretion and absorption (e.g., kidney tubules)

  Simple Columnar: Tall, column-like cells; may have microvilli for absorption or cilia for movement (e.g., intestinal lining).
• What are stratified epithelial cells?

  Multiple layers of cells,

  • Stratified Squamous: Protects against abrasion; found in skin, mouth, and esophagus.
  • Stratified Cuboidal: Rare; provides structural support (e.g., sweat gland ducts).
  • Stratified Columnar: Rare; found in some glands and the male urethra.
• What are glandular epithelial cells?

  Specialized epithelial cells that form glands and are involved in secretion,

  • Exocrine Glands: Secrete products like sweat, saliva, or digestive enzymes through ducts.
  • Endocrine Glands: Secrete hormones directly into the bloodstream (e.g., thyroid, adrenal glands).
• What disorders caused by failure of homeostasis?

  diabetes (insulin failure)

  neuroendocrine disorders

  hypertension (high blood pressure)

  obesity

  heat stroke