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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.

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importance of homeostasis in mammals
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
slide3

Homeostasis

Definition: Keeping the internal environment in a Steady state

It is controlled by Negative Feedback Mechanism

slide4

Rise above

normal value

Corrective Mechanism

negative feedback

NEGATIVE FEEDBACK MECHANISM

normal value

normal value

negative feedback

Fall below

normal value

Corrective Mechanism

parts of body involved

tissue cells

blood

Parts of Body involved

skin

  • kidneys :
    • regulate water & mineral salts concentration
  • skin :
    • regulate body temperature
  • liver & pancreas :
    • regulate blood glucose level

kidney

liver

+

pancreas

osmoregulation water mineral salts
Osmoregulation (Water & Mineral salts)
  • Regulate water potential in Tissue Fluid
  • Organ involved: KIDNEYS
slide7

Concentrated Urine is produced

Normal Water Content in Blood

After Sweating

Concentrated Blood

Larger proportion of water is reabsorbed

slide8

Diluted Urine is produced

Normal Water Content in Blood

After Drinking

Diluted Blood

Smaller proportion of water is reabsorbed

osmoregulation water mineral salts9
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
Thermoregulation(Regulation of Body Temperature)
  • poikilotherms (cold-blooded animals)
    • body temperatures vary with that of the environment
    • e.g. reptiles, fish, amphibians
thermoregulation regulation of body temperature11
Thermoregulation(Regulation of Body Temperature)
  • Homoiotherms (warm-bloodedanimals)
    • keep body temperature constant even in winter by increasing metabolic rate
    • e.g. birds, mammals
slide13

Sebaceous gland

Receptors

Outermost layer

Hair follicle

Erector muscle

Middle layer

Epidermis

Innermost layer

Dermis

Sweat gland

Blood capillaries

Subcutaneous fat

Nerve fibres

Structure of Mammalian Skin

epidermis
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
epidermis15
Epidermis
  • 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
dermis
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
dermis17
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
dermis18
Dermis
  • Sebaceous gland
    • secretes oily substance
      • to make the skin waterproof
      • to prevent bacterial entry
  • Receptors
    • detect pain, pressure, temperature & touch
subcutaneous fat
Subcutaneous Fat
  • beneath the Dermis
  • for fat storage
  • acts as insulator of heat
functions of our skin
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 skin21
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)
slide23
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.
slide24
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)
slide25
Develop thinner subcutaneous fat & shed their fur
    • as long term responses
    • increase heat loss
  • Decrease metabolic rate & muscle contraction
    • gain less heat
slide27
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
slide28
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
slide29
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
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)
slide31

Pancreas secretes insulin

Liver coverts glucose to glycogen

Soon after a meal

Pancreas secretes less insulin

Long after a meal

Liver converts glycogen to glucose

Too High

Blood glucose level falls

normal blood glucose level

normal blood glucose level

Too Low

Blood glucose level rises