homeostasis

• Excretion


  Getting rid of metabolic waste, substance in excess and toxic substance
• Excretion organs


  • Lung
  • Liver
• Excretion by lungs


  Excretion of CO2
• Urinary system structure


  • Kidney
  • Ureter
  • Bladder
• ureter carries urine to bladder
• Bladder stores urine
• renal artery supplies blood to the kidney
• Renal vein collects blood from the kidneys
• Kidney has a capsule, cortex, medulla, and single nephrons
• Homeostasis


  Keeping the internal environment constant
• Osmoregulation


  Maintenance of the water and salt concentration of internal environment relatively constant
• Ultrafiltration in the nephron


  1. Passage of the plasma and small molecules (glucose, amino acid, urea, uric acid, water, mineral ions) out of the pores of the glomerulus into the Bowman's capsule under high pressure

  2. Blood cells and large proteins can't pass out as they are too large to pass out from the capillary pores
• Selective reabsorption in the nephron


  1. Reabsorption of all glucose and amino acid by active transport back into the blood

  2. Water is reabsorbed by osmosis back into the blood
• Loop of Henle


  Site of reabsorption of water into the blood
• Desert animals have a long loop of Henle to ensure maximum reabsorption of water
• Osmoregulation in the collecting duct

  ADH (Anti-diuretic Hormone) from the hypothalamus binds to receptors on the collecting duct, increasing water reabsorption resulting in concentrated urine
• Skin


  • Tough outer layer to resist mechanical damage
  • Act as a barrier for entrance of pathogens
  • Impermeable surface to prevent loss of water
  • Act as a sense organ for touch and temperature change
  • Controlling the loss of heat through body surface
• Thermoregulation


  Thermoregulatory center in hypothalamus detects temperature changes and sends nerve impulses to:

  Higher temperature - Sweat glands release sweat, vasodilation of arterioles, hair erector muscles relax

  Lower temperature - Shivering, vasoconstriction of arterioles, hair erector muscles contract
• Hormone


  Chemical secreted by a gland and travels through blood plasma to target organs, altering their activity
• Adrenaline


  Hormone secreted by the adrenal gland in response to fear, fight or flight, causing increased heart rate, breathing, glucose release, pupil dilation, and increased muscle respiration
• Blood glucose regulation


  Pancreas detects changes in blood glucose level

  Increased glucose - Insulin stimulates liver to store glucose as glycogen, stimulates glucose breakdown in aerobic respiration

  Decreased glucose - Glucagon stimulates liver to break down glycogen into glucose
• Nervous system


  Central nervous system (brain and spinal cord)

  Peripheral nervous system (relay sensory information to and motor impulses from the CNS)
• Reflex action


  Automatic rapid response that protects against tissue damage
• Structure of the eye

  • Lens controls amount of light entering

  Lens refracts light onto retina

  Retina contains rods (for dim light, no color) and cones (for bright light, color vision)

  Optic nerve carries nerve impulses to the brain
• Eye reflex to bright and dark

  Pupil constricts in bright light, dilates in dim light
• Accommodation of the eye

  Ciliary muscles contract to thicken the lens for near vision, relax to flatten the lens for distant vision
• Hypothalamus contains osmorecptors that

  detect the water potential of the blood • If the water potential of the blood drops

  Osmoreceptor shrink stimulate posterior

  pituitary gland to secrete ADH• that travel through blood plasma and bind to

  receptors on the membrane of the collecting • increasing water reabsorption resulting in

  concentrated urine