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Homeostasis (Fluids (Osmotic pressure determined by non-penetrating…

- - - - Epithelium
      - Muscle
      - Nerve
      - Connective Tissue
  - - - High conc of K+, low conc of Na+ and free Ca2+, higher conc of phosphates and proteins
    - - Interstital Fluid (ISF) = 3/4 ECF
      - Intravascular Fluid (IVF) = 1/4
      - Low conc of K+, high conc of Na+ and Ca2+
    - - 2 K+ in, 3 Na+ out, maintain negative potential of cell
      - Kept in such a steady state (as concentration across membrane is not equal)
- - - - O2, CO2, glucose and other metabolites, osmotic pressure, conc of H+, Ca2+, K+ and Mg2+, and temperature
    - - Neutral Balance: intake + production = outflow
      - +ve balance: intake + production > outflow
      - -ve balance: intake + production < outflow
- - - - Paracrine (neighbours) and autocrine (self)
      - Proteins called cytokines mediate local control
    - - Nervous (faster) or endocrine (slower)
        
        Reflex control loop:
        
        Stimulus
        
        Goes to sensor (afferent)
        
        Integration center (usually brain) where signal is evaluated, compares to set point and decides on appropriate response
        
        effectors (efferent path) to bring situation back to within normal limits
      - Respond to changes that are more widespread or systemic
  - - - Most common form of regulation
      - Stimulus > sensor > controller (set pt) > effector
        (simple)
      - E.g. changing body temperature, Arterial pH, Na+, K+, urea and glucose
      - Complex: involves a chain of multiple cells (that could activate downstream effectors but inhibit upstream cells) with multiple feedbacks
    - - Quite Rare
      - Consequence is to elicit a change, once sufficient biological momentum is reached, other influences including negative feedback will reduce or terminate the responses
      - Normally found during development, also associated with biological processes like a blood clot.
    - - Predict a change about to occur and primes the response loop
      - Doesnt accelerate the response nor increase sensitivity
      - e.g. salivation in response to smell of food
    - - Activity modulated up or down, not on/off, and is maintained over time, e.g. dilation and constriction of blood vessels
    - - Either nervous or endocrine system for activity that is modulated but not under tonic control
      - e.g. parasympathetic vs sympathetic nervous control
    - - Predictable, timed activity
      - Govern many biological functions, including BP, temperature and metabolic processes
      - Body temperature usually peaks in late afternoon and declines dramatically in early morning
      - Concentrations of certain hormones also change during the course of the day (in a 24 hour cycle)
      - Arise from a special group of cells in the brain that programmed by either light-dark or day-night cycle through input from retina or rest-activity periods
        
        allow bodies to anticipate behavior and coordinate body processes accordingly
      - Morning people have higher body temps in the morning while night people have lower body temp
      - Cortisol corresponds to waking time, so a person waking up in the evening will have elevated cortisol at 4pm, compared to a normal person that has it at 8am