2 - The human body. Homeostasis. General Principals of homeostatic regulation-control systems and their elements. Levels of physiological regulation.

sections

• what is homeostasis

• conditions of homeostasis

• regulation of homeostasis

• feedback regulation

• levels of physio regulation

• what is homeostasis

Homeostasis is the control and maintenance of a constant internal environment and physiological conditions

• conditions controlled by homeostasis

• temperature (37 degrees)

• salt

• CO2, O2

• blood pressure (systolic = 100-140 mmHg, Diastolic = 60-90 mmHg)

• pH (7.35-7.45 mmol = through bicarbonate ions in blood)

• water balance (amount of water entering body and total output of water lost from the body)

• Specific blood conditions or other variables within living organism:

  • maintain RBC and WBC count

  • pH of blood

  • viscosity of blood

• regulation of homeostasis

• Can involves hormones (ADH-kidney/ vasopressin - blood vessels)

• Involves three mechanism:

  • stimulus - signal that detects a change has occurred

  • receptor - receives information of environment changes

  • control centre receives and processes info from receptor

  • effector - responds t commands of control centre, opposes or enhances stimulus

• it is a ongoing process that continually works to restore and maintain homeostasis

• feedback regulation

1. NEGATIVE FEEDBACK - regulatory mechanism where ‘stimulus’ causes opposite ‘output’ in order to maintain ideal level of whatever is being regulated

   • occurs when rate of process decreases

   • as concentration of product increases

     • hypothalamus responds to temperature flucturations. Temp low - shiver to bring temp up. Temp hot - sweat, evaporation to cool body

     • Blood pressure increases, signal sent to brain from blood vessels causing dilation

2. POSITIVE FEEDBACK - output enhances original stimulus (e.g during labour, hormone oxytocin released)

   • intensifies and speeds up contraction

   • increase in contractions causes more oxytocin to be released and cycle goes on until the baby is born - stimulus stretch - hypothalamus

   • another example - blood clotting

• levels of physio regulation

• There Is Bad Cats

1. There Is Bad Cats

   1. Thermoregulation: shiver etc, denature, sweating , aggregate vasodilation

2. Iron and sodium balance: iron is needed in haemoglobin and v important,

   • high levels toxic.

   • Most iron is contained in red blood cells, → Fe²⁺ central metal ion in heme

   • iron deficiency is the most common cause of anaemia. in ion metal heme

   • When body levels of iron are too low, hepcidin in the duodenal epithelium decreases, causing an increase in ferroportin activity, stimulating iron uptake in the digestive system.

     Sodium is an important cation distributed primarily outside the cell used during AP

3. Blood composition: glucose- insulin, glucagon, plasma → via kidney → controls plasma valve and RBC mass

4. Cardiovascular System- co2/o2 levels

other - RAS, calcium-PTH, calcitonin, ADH-water volume, skeletal