Survival

							       Survival




Requirements and Homeostasis
      Anatomy: Examination

Deals with structure (morphology) of the
 body parts

Parts and how they are arranged
  Physiology: Experimentation

Considers the function of the body parts

What they do and how they do it
Requirements for survival
    Requirements of Organisms

• Water: Most abundant substance in the body

• Nutrients: Substances that provide necessary
  chemicals (nutrients) in addition to H2O

• Oxygen: Gas that makes up 1/5 of the atmosphere

• Heat: Energy

• Pressure: Application of force on an object
– Variety of metabolic
  process

– Provides
  environment in
  which most take
  place

– Transports
  substances within
  organisms
                         Water
– Regulating body
  temperature
Nutrients

      – Energy supply

      – Raw materials for
        building new
        living matter
                Oxygen

– Use in releasing energy from nutrients
  (respiration/cellular)

– Energy in turn drives metabolism process
                    Heat
– Product of metabolic reactions
  • Rate of reactions governed by amount of heat
    present
     Pressure

– Breathing

– Heart action            blood pressure
  which forces blood through vessels
Homeostasis
                Homeostasis
• Internal environment protects body from
  changes in the external environment

  – Cells interact to keep internal environment relatively
    constant
  – Most of the body’s metabolic energy spent on
    maintaining homeostasis
     Feedback Mechanisms

• Homeostasis is maintained by a self-
  regulating control mechanism that can
  receive signals about changes away from
  the normal set-point
                    And
• Can cause reactions that tend to return
  conditions to normal
          Initiators/Controls
• Nervous system               • Endocrine system
  – Receptors to brain to        – Receptors to brain to
    receptors                      endocrine glands
  – Fast and immediate           – Slow

     • Body temp regulation         • Uterine contraction in
     • Blood pressure                 childbirth
     • Release of adrenaline        • Lactation
       by adrenal gland             • Release of insulin
     • Breathing
Nervous system is involved in
      both feedbacks
              Brain

    Nervous           Endocrine
       Negative Feedback
• Changes from Set Point stimulate
  responses in opposite direction
• Forces act upon one another


For every action there is an opposite
         and equal reaction
        Positive Feedback

• Changes from Set Point stimulate more of
  initial reaction

  – Usually produces unstable conditions for short
    periods of time


             Cascading Effect
Negative Feedback


       Regulation of body temperature
           Hypothalamus detects change
                Increase in sweating              Sweating and increased
            Dilation of skin blood vessels         blood flow = Heat loss




 Body temperature                                                 Body temp returns
    increases                                                       toward normal




Change from normal                                          Response


 Body temperature
                                    Normal body
                                                                  Body temperature
    decreases                       temp range                  returns toward normal




     Hypothalamus detects change
                                                    Decreased sweating
           Decreased sweating
                                              & skin blood flow = Heat retained
     Constriction of skin blood vessels
                                                  Shivering produces heat
                 Shivering
Positive Feedback

   Snowball Effect
• One example is the onset of contractions in childbirth, known as the
  Ferguson reflex. When a contraction occurs, the hormone oxytocin is
  released into the body, which stimulates further contractions. This
  results in contractions increasing in amplitude and frequency.[5]
• Another example is the process of blood clotting. The loop is initiated
  when injured tissue releases signal chemicals that activate platelets in
  the blood. An activated platelet releases chemicals to activate more
  platelets, causing a rapid cascade and the formation of a blood clot.[6]
• Lactation also involves positive feedback in that the more the baby
  suckles, the more milk is produced, via a surge in prolactin secretion.[7]
• Estrogen that functions during the follicular phase of menstruation is
  also an example of positive feedback.[8]
• The generation of nerve signals is another example, in which the
  membrane of a nerve fibre causes slight leakage of sodium ions through
  sodium channels, resulting in a change in the membrane potential,
  which in turn causes more opening of channels, and so on. So a slight
  initial leakage results in an explosion of sodium leakage which creates
   the nerve action potential.[9]
Positive Feedback


        Lactation
                                    Prolactin stimulates milk production
      After childbirth

                             Nipple or Areola of breast mechanically stimulated
      Baby suckling
       or pumping
                                    Nerve impulses to Hypothalamus


  Stimulated by baby
                                   Hypothalamus signals posterior lobe
 at breast sensory sites          of the pituitary gland to release oxytocin


  Oxytocin also causes             Oxytocin causes myoepithelial cells
     contraction of               surrounding alveolar glands to contract
    uterine muscles

                             Milk is ejected from ductile system through nipple
    Milk “lets down”
  Only by mechanical
   Squeezing of cells
                                             Breast is emptied


   As long as breasts
       are emptied                  Prolactin continues to be released
milk will continue to flow
Endocrinal feedback
Target
Tissue

                        Gland A



         Hormone A                  Hormone B
         Stimulates                  Inhibits
          Gland B                     Gland A




                      Gland B

                                  Inhibition of one gland to another
                                  (Negative effect)
      Target                               Gland A
      Tissue




                   Hormone A                         Hormone B
                   Stimulates                        Stimulates
                   Gland B                           Gland A


                                           Gland B



    Endocrine gland is stimulated to
 Increase its rate of hormonal secretion
            (Positive effect)
By a substance it causes to be produced