Homeostasis In Mammals  Ar
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Homeostasis In Mammals Ar

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  • very informative...where do u get them from?..need more topics pls!
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Homeostasis In Mammals  Ar Homeostasis In Mammals Ar Presentation Transcript

  •  
  • Importance of Homeostasis in Mammals
    • metabolic reactions are controlled by enzymes
    • enzymes work best in a narrow range of temperature & pH only
    • ∴ important to keep internal environment as steady as possible
  • Homeostasis Definition: Keeping the internal environment in a Steady state It is controlled by Negative Feedback Mechanism
  • Rise above normal value Fall below normal value normal value Corrective Mechanism Corrective Mechanism NEGATIVE FEEDBACK MECHANISM normal value negative feedback negative feedback
    • kidneys :
      • regulate water & mineral salts concentration
    • skin :
      • regulate body temperature
    • liver & pancreas :
      • regulate blood glucose level
    Parts of Body involved kidney liver pancreas + skin tissue cells blood
  • Osmoregulation (Water & Mineral salts)
    • Regulate water potential in Tissue Fluid
    • Organ involved: KIDNEYS
  • After Sweating Concentrated Blood Larger proportion of water is reabsorbed Normal Water Content in Blood Concentrated Urine is produced
  • After Drinking Diluted Blood Smaller proportion of water is reabsorbed Normal Water Content in Blood Diluted Urine is produced
  • Osmoregulation (Water & Mineral salts)
    • After having a very salty meal
      • produce concentrated urine to remove excess salts in solution form
      • extra water is needed to be excreted along with the excess salts
      • sensation of thirst (drink more water to compensate for the water loss)
  • Thermoregulation (Regulation of Body Temperature)
    • poikilotherms ( cold-blooded animals )
      • body temperatures vary with that of the environment
      • e.g. reptiles, fish, amphibians
    • Homoiotherms ( warm-blooded animals )
      • keep body temperature constant even in winter by increasing metabolic rate
      • e.g. birds, mammals
    Thermoregulation (Regulation of Body Temperature)
  • Maintenance of Body Temperature SKIN
  • Structure of Mammalian Skin Epidermis Dermis Outermost layer Middle layer Innermost layer Sweat gland Blood capillaries Subcutaneous fat Receptors Erector muscle Nerve fibres Sebaceous gland Hair follicle
  • Epidermis
    • dead outer layer
      • relatively impermeable
      • easily peeled off
      • protect the underlying tissues
        • to prevent mechanical injury
        • to prevent bacterial entry
        • to reduce water loss
    • middle layer
      • made up of living cells
      • become dead as they approach the surface
    • black inner layer
      • with pigment (melanin) to absorb ultra-violet ray for sunlight
      • have cell division to repair the lost outer layers
    Epidermis
  • Dermis
    • Blood capillaries
      • to nourish the cells of the skin
      • branch into superficial blood capillaries
    • Sweat gland
      • surrounded by a network of capillaries
      • secrete sweat (consists of water, mineral salts, urea & some waste materials)
      • characteristic of mammals
  • Dermis
    • Hair follicles & Hairs
      • each hair has a nerve & a capillary attached to it
      • nerve: receives stimuli
      • capillary: supply food & oxygen
      • hairs reduce heat loss & assist in temperature regulation
    • Erector muscle
      • controls the hair movement for temperature regulation
  • Dermis
    • Sebaceous gland
      • secretes oily substance
        • to make the skin waterproof
        • to prevent bacterial entry
    • Receptors
      • detect pain, pressure, temperature & touch
    • beneath the Dermis
    • for fat storage
    • acts as insulator of heat
    Subcutaneous Fat
  • Functions of Our Skin
    • protect the body (epidermis)
      • to provide mechanical protection
      • to prevent bacterial entry
      • to reduce water loss
    • temperature regulation (hair)
  • Functions of Our Skin
    • excretion of sweat (sweat gland)
    • store fats (subcutaneous fat)
    • sensation (numerous receptors )
    • production of vitamin D under ultra-violet light (inner epidermis)
  • Control Body Temperature in Hot Conditions
    • More sweat is produced by sweat glands
      • evaporation of sweat takes away heat which produces a cooling effect
    • Vasodilation of skin arterioles
      • arterioles near the surface of the skin dilates
      • to let more blood flows near the skin surface
      • to have more heat lost by conduction & radiation.
    • Erector muscles relax
      • hairs lie flat on the skin
      • reduce thickness of air trapped among the hairs (not effective in human because human’s hairs are short)
    • Develop thinner subcutaneous fat & shed their fur
      • as long term responses
      • increase heat loss
    • Decrease metabolic rate & muscle contraction
      • gain less heat
  • Control Body Temperature in Cold Conditions
    • Vasoconstriction of skin arterioles
      • arterioles near the surface of the skin constrict
      • to let less blood flows near the skin surface
      • to have less heat lost by conduction & radiation
    • Erector muscles contract
      • pull hairs erect for trapping more air
      • thicker layer of air acts as a good insulator of heat
    • Less sweat is produced by sweat glands
      • reduce heat loss by evaporation
    • Develop thicker subcutaneous fat & thicker fur
      • as long term responses
      • reduce heat loss
    • Increase metabolic rate & muscle contraction
      • gain more heat
  • Regulation of Blood Glucose Level
    • controlled by Negative feedback mechanism
    • controlled by insulin secreted from the islets of Langerhans in pancreas
    • Diabetes - malfunction of pancreas (does not secrete enough insulin)
  • normal blood glucose level Blood glucose level falls Blood glucose level rises normal blood glucose level Too High Too Low Liver converts glycogen to glucose Soon after a meal Long after a meal Pancreas secretes insulin Pancreas secretes less insulin Liver coverts glucose to glycogen
  • ~ END ~