homeostasis

• cells are the basic unit of life and capable of performing requirments for life - celllular physiology
• aggregate - to collect or gather into a mass or whole
• all cells have eight basic functions:

  1. obtain nutrients and O2
  2. creat energy from nutrients and O2
  3. eliminating waste products
  4. synthesising proteins for cell functions and growth
  5. controlling movement of material in and out of the cell
  6. effectively moving material inside the cell
  7. responding to surroundings
  8. reproduction - ability to divide
• the ability to divide or reproduction is an exception in some specialised cells
• there are four types of primary tissues formed from cells of similar structure and specialised function
• the four types of primary tissues:

  • connective tissue
  • epithelial
  • muscle
  • nervous
• amoeba and other single celled organisms can obtain nutrients directly from their immediate environment whereas in complex organisms do not have direct contact to their external environment but still has the same requirements as amoeba with each cell in the complex organism contributing to the organisms survival and the environment has to be suitable
• ECF - extracellular fluid
• ECF is the watery external elelment that surrounds cells and an internal environment of the body as well as a fluid environment that cells can live in
• ECF has two compartments:

  • plasma
  • interstitial fluid (fluid surrounding/bathes cells)
• ECF provides a medium for life which where cells make crucial exchanges
• there are specialist systems that are rquired to maintain ECF
• systems that help regulate the ECF:

  • digestive - supply nutrients
  • respiratory - provides oxygen removes carbon dioxide
  • cardiovascular - distribution of nutrients and oxygen
  • renal - removal of waste
• cells must maintian the composition of ECF through these vital processes
• The ECF must be compatible with cell xurvival and its composition should be maintained within narrow limits
• the ECF requires consistent replenishment of oxygen and nutrients as well as removal of waste products and mainting the temperature for biochemical reactions
• homeostasis is dynamic
• homeostasis is the continuous variation around the optimal value with the fluctuations never great enough to be life threatening
• the internal environment of an organism is required to be relatively stable but this is easily disrupted by both internal and external stimuli - homeostasis helps to counteract these changes
• homeostasis regulated functions:

  1. [nutrient molecules]
  2. [oxygen and carbon dioxide]
  3. [waste products]
  4. pH
  5. [water, salts and other electrolytes]
  6. blood volume and pressure
  7. temperature
• for a certain parameter to be obtained:

  • deviations from the normal must be detected
  • relevant info must be integrated together
  • adjustments should be made
• two types of homeostatic regulation:

  • intrinsic - autoregulation
  • extrinsic
• intrinsic/autoregulation is the automatic adjustment to some environmental change
• extrinsic regulation is the intervention by the nervous and/or endocrine system
• intrinsic is the direct adjustment as a response by cell/organ/tissue/physiological system to the environmental change
• intrinsic occurs by:

  • symptom
  • response
  • result
• extrinsic regulation made by the nervous system is short and rapid as well as very specific
• extrinsic regulation by the endocrine system is not immediately apparent and can last for days or for longer
• homoestatic control mechanisms have three independent components:

  1. sensor
  2. control centre
  3. effector
• 1. SENSOR - sensitive to environmental change or stimulus
• 2. control centre - recieves anf processes info which is supplied by the sensor
• 3. EFFECTOR - cell or organ which responds to the commands of the control centre and whose activity either opposes or exaggerates the stimulus
• homeostatic system - detects and responds to a change
• feedback - change made after intial change id detected
• feedforward - any change that is made in anticipation of a change
• set point - the optimum state
• controlled variable will oscillate around the set point because of time delay between sensing the change and the correction
• how sensitive the sensor is determined by the importance of the feature that is being regulated
• Negative feedback couteracts the intial change
• antagonisitic effectors work on push-pull principle and alternate and counteract each other to prevent deviating from the norm too much