Human Bio - Homeostasis

• Role of the Liver:

  removed from blood to provide energy for liver

  removed + converted into glycogen for storage (glycogenesis)

  continue to circulate blood - available as energy for cells

  converted into fat for LT storage
• Role of the Pancreas:

  Islets of Langerhan - Alpha + Beta cells

  chemoreceptors in IOL detect change in BGL

  • Alpha: secrete glucagon = increase BGL
  • Beta: secrete insulin = decrease BGL
• Role of Adrenal Gland:

  increase BGL -> stimulate glycogenolysis

  Cortex: secrete glucocorticoids (cortisol)

  Medulla: secrete adrenaline + noradrenaline
• Control of Breathing:

  require stimulation from nerve impulses

  nerve impulses controlled by respiratory centre (medulla oblongata)

  • diaphragm - phrenic nerves
  • intercostal muscles - intercostal nerves
• Chemoreceptors:

  • Peripheral: in walls of aortic + carotid arteries sensitive to changes in O, CO2 + H+ in blood
  • Central: in medulla oblongata sensitive to changes in CO2 in blood + H+ in CSF
• Oxygen:

  1. stimulate peripheral chemoreceptors
  2. nerve impulses transmitted to respiratory centre
  3. nerve impulse to diaphragm + intercostal muscles
• Carbon Dioxide:

  increase = H+ increase

  1. stimulates peripheral + central chemoreceptors
  2. transmit nerve impulse to respiratory centre
  3. nerve impulse to diaphragm + intercostal muscles
• Hydrogen Ions:

  increase = pH decrease

  1. stimulates peripheral chemoreceptors
  2. transmit nerve impulse to respiratory centre
  3. nerve impulse to diaphragm + intercostal muscles
• Kidneys + Antidiuretic Hormone:

  Controls permeability of walls of DCT + CD

  High ADH concen = high permeability to water

  1. Decreased water concen = increased osmotic pressure
  2. Osmoreceptors in hypothalamus detect change in OP
  3. Hypothalamus stimulates posterior pituitary to release ADH
  4. Permeability to water in DCT + CD increases
  5. More water reabsorbed into blood from DCT + CD
  6. Reabsorption of water = increased water concen = decreased OP
• Kidneys + Aldosterone:

  increase amnt of Na reabsorbed into blood + K excreted in urine

  uses sodium-potassium pump

  water is reabsorbed w/ Na
• Thirst Response:

  stimulus: water concen decreases = OP increase/dry mouth

  receptor + modulator: osmoreceptors in hypothalamus stimulated

  effector: feel thirsty

  response: drinks water

  water reabsorbed -> fluids return to normal level
• Dehydration: insufficient water levels, can be fatal - body can't carry out functions

  Water Intoxication: excessive amount of water = fluids too dilute + cells swell due to osmosis
• Voluntary Breathing:

  controlled by cerebral cortex

  bypasses respiratory centre

  protective device = enable prevention of irritating gases + water entering lungs

  if CO2 concen rises = respiratory centre overrides = forced to breathe
• Hyperventilation:

  rapid + deep breathing = increase O concen + remove more CO2 than necessary

  corrects itself - reduction in CO2 = no urge to breathe until returned to normal levels
• Type 1 Diabetes:

  inherited, autoimmune

  excess glucose unable to be stored as glycogen - instead excreted in urine
• Type 2 Diabetes:

  lifestyle factors: obesity, low exercise, smoking, high BP, diet high in fat, sugar + salt, low in fibre

  Insulin Resistance: pancreas produces insulin, but cell membrane doesn't respond to it = glucose not absorbed
• Hyperthyroidism:

  too much thyroxine = high BMR

  symptoms: weight loss, increased heart rate + appetite, fatigue

  Treatment -

  1. Surgery: remove thyroid cells
  2. Anti-thyroid medication: blocks iodine uptake
  3. Radioactive Iodine: kills thyroid cells
• Hypothyroidism:

  too little thyroxine = low BMR

  occurs due to lack of iodine in diet

  symptoms: goitre (enlarged thyroid), feeling cold, fatigue

  no cure - take synthetic thyroxine in tablet
• Conduction: direct contact between particles

  Convection: movement of liquid or gas

  Radiation: infrared radiation emitted by object

  Evaporation: process of liquid forming a gas (absorbs heat)
• Shivering:

  hypothalamus stimulates brain regions controlling muscle tone

  muscle tone increased = rhythmic tremors = shivering

  no external work, all energy from metabolic activity goes toward heat
• Vasoconstriction:

  hypothalamus stimulates sympathetic nerves to constrict BVs

  decrease flow of blood to skin = decrease transfer of heat
• Sweating:

  sympathetic nerves stimulated by hypothalamus, impulse sent to sweat glands, sweat glands pump fluid to skin

  sweat evaporates off skin = cooling effect
• Vasodilation:

  hypothalamus stimulates sympathetic nerves to dilate BVs

  increases blood flow to skin = increase transfer of heat
• 3 cellular processes in response to insulin

  Increase glucose uptake by cells = increase cellular respiration

  Promotes glycogenesis = more glucose converted to glycogen

  Promotes lipogenesis = more glucose converted to lipid

  Increase protein synthesis = glucose used as energy