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Human Physiology and Homeostasis

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  • Human physiology is the branch of biological science that explains the specific characteristics and mechanisms of our body that help it to function as a living organism.
  • Homeostasis is the process by which the body maintains its internal environment at optimum conditions to function as a living being

Homeostasis: maintenance of near-constant internal conditions in the body’s internal environment, making sure all tissues and organs function under right conditions


Control system of homeostasis

  • All tissues and organs of the body perform functions that help in homeostasis.
  • Homeostasis maintains the amount of ions, nutrients, wastes. etc. at a range, not a specific value. This range may be large or small depending on the substance.
  • The systems used by the organs is known as the feedback loop.
  • This feedback loop has three main components
  1. Receptors: sensory organs of the nervous system which obtain stimuli that the organism is exposed to. {Stimuli are defined as detectable changes in the organism’s internal or external environments}
  2. Control Center: parts of the CNS, specially the reflex arc, which decide which stimuli must be replied to, and in what method
  3. Effectors: mainly muscles and glands, these receive instructions from control center to respond to the stimuli


  • The afferent pathway takes signals from the receptors to the control center.
  • The efferent pathway takes signals from the control center to the effectors.


  • These pathways are controlled by two main systems; the nervous and endocrine systems.

Nervous system

Endocrine system
Electrical signals

Quick effect

Specific response

Hormonal signals

Prolonged effect

Global respose


Homeostatic feedback systems

  • Most commonly used system is the negative feedback mechanism
  • When a certain entity is in excess, or is deficient, this brings it back to the normal range by initiating processes negative to the stimulus.

Ex: when blood glucose levels increase, body takes measures that will reduce the amount of glucose in blood

  • Positive feedback mechanism is very rarely used for homeostasis, because it could lead to death in most cases.
  • Even in the few cases where its used, its seen only as part of a negative feedback mechanism

Ex: increment of nerve potential when creating action potential

Ex: continuous placement of platelets to make blood clot


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Categorised in: Medicine, Physiology

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