1. Homeostasis Anatomy & Physiology
Nursing Theory and Role Development
8/12/2023
Homeostasis Anatomy & Physiology
Muhammad Ziad Lecturer INS-KMU Peshawar

2. Homeostasis Definition
Nursing Theory and Role Development
8/12/2023
Homeostasis Definition
The term ‘homeostasis’ is derived from two Greek words; Homeo which means ‘same’ and Stasis which means ‘standing’.
In its simplest form it means ‘staying the same’.
It is an organism’s internal environment which ‘stays the same’

3. Nursing Theory and Role Development
8/12/2023
Cont…
The ‘internal environment’ refers to the conditions inside an organism. These conditions remain more or less constant despite changes in the outside environment.
In practice, it comes down to providing a stable environment for the cells of the body.
Definition:
The maintenance of the internal environment within narrow limits is called homeostasis.

4. Nursing Theory and Role Development
8/12/2023
Important Terms
Receptor
A structure that monitors the body's internal functions and conditions; detects changes in the body's internal environment and carry them to the control center.
Control center
The center that receives messages from receptors about a change in the body's internal conditions and relays messages to effectors to change their function to correct the deviation; in most homeostatic mechanisms, the control center is the brain.

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Important Terms Cont…
Effectors:
A muscle or organ that receives messages from the control center to change its function in order to correct a deviation in the body's internal conditions.
Hormone:
—Chemical regulator of physiology, growth, or development which is typically synthesized in one region of the body and active in another.

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Important Terms Cont…
Negative feedback loop:
—A homeostatic mechanism that opposes or resists a change in the body's internal conditions.
—A mechanism the Positive feedback loop increases or enlarges a change in the body's internal conditions.

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Needs Of Homeostasis
The living processes in the cells depend on the activity of enzymes.
These enzymes work best in specific conditions such as those of temperature and PH. Any change in these conditions affects the function of the enzymes and may lead to the death of the cells or, ultimately, the whole organism.

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Cont…
This is why the internal environment needs to be regulated and kept constant.
In fact, the internal conditions are not absolutely constant, but allowed to vary within very narrow limits. Human body temperature, for example, varies between 36.1 – 37.8 o C The average temperature is usually expressed as 36.8o C

9. Nursing Theory and Role Development
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Cont…
There is no specific organs which controls homeostasis except, possibly, the brain.
The skin, kidneys, liver, endocrine system, nervous system and sensory system all play a part in maintaining the internal environment within narrow limits
Examples of Homeostasis: The skin is a homeostatic organ which helps maintain the body temperature within the limits given in the previous slide

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Cont…
The external temperature varies during the day and from season to season, sometimes by as much as 40 degree C, but the human body temperature stays at about 37 degree C
This is achieved by sweating, vasodilation, vasoconstriction, and shivering

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Cont…

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Cont…
Vasodilation
Much Heat Loss
If the body temperature rises, the blood vessels in the skin dilate (become wider) and allow more blood to flow near the surface. The heat loss from the blood through the skin helps cool the circulating blood

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Cont…
Vasoconstrictions:
If the body temperature falls. The blood vessels in the skin constrict. Less warm blood flows near the surface so less heat is lost.
Little heat loss

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Cont…
Example # 2:
In the cells, the chemical breakdown of proteins produces the nitrogenous compound, urea. If this were allowed to accumulate in the cells it would damage or kill them.
This homeostatic functions are carried out by the kidneys through which urea are excreted from the body.

15. Negative feedback Mechanism:
Nursing Theory and Role Development
8/12/2023
Negative feedback Mechanism:
It applies to many systems in the body. Temperature regulation is one example
If the blood temperature rises, a ‘heat gain’ centre in the brain sends nerve impulses to the skin, which causes vasodilation and sweating, which cool the blood.

16. Negative feedback cont…
Nursing Theory and Role Development
8/12/2023
Negative feedback cont…

17. Negative feedback cont…
Nursing Theory and Role Development
8/12/2023
Negative feedback cont…
If the blood temperature falls, it stimulates a ‘heat loss’ centre in the brain which sends impulse to the skin causing vasoconstriction and the cessation of sweating. These changes reduce heat loss from the skin.
The warmer or cooler blood provides negative feedback to the thermoregulatory center in the brain

18. Negative feedback cont…
Nursing Theory and Role Development
8/12/2023
Negative feedback cont…
Negative feedback is the primary homeostatic mechanism that keeps a variable close to a particular value, or set point.
A homeostatic mechanism has three components: a sensor, a regulatory center, and an effectors. The sensor detects a change in the internal environment; the regulatory center activates the effectors; the effectors reverses the change and brings conditions back to normal again.

19. Negative feedback cont…
Nursing Theory and Role Development
8/12/2023
Negative feedback cont…
Another example of negative feedback is the control of the hormone estrogen
The pituitary body produces follicle-stimulating hormone (FSH) which promotes the development of the ovarian follicles and causes the ovaries to produce estrogen
Estrogen also acts on the uterus and causes its lining to thicken

20. Negative feedback cont…
Nursing Theory and Role Development
8/12/2023
Negative feedback cont…
When the estrogen reaches a certain level in the blood, it acts on the pituitary and stops the production of more FSH
In this case, oestrogen is exerting a negative feedback on the pituitary
If the oestrogen level in the blood falls, the pituitary begins to secrete FSH again

21. Positive Feedback Mechanism:
Nursing Theory and Role Development
8/12/2023
Positive Feedback Mechanism:
Positive feedback is a mechanism that brings about a change in the same direction.
Examples: Blood clotting
Release of oxytocin during delivery

22. Positive Feedback Mechanism:
Nursing Theory and Role Development
8/12/2023
Positive Feedback Mechanism:

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Disease
Disease is present when homeostasis fails and the body (or part of the body) no longer functions properly. The effects may be limited or widespread.
A Local disease is restricted to a specific part of the body, while, a systemic disease affects the entire body or involves several organ Systems.

24. Factors affecting Homeostasis
Nursing Theory and Role Development
8/12/2023
Factors affecting Homeostasis
Disease
Stress
Lifestyle
Injury
Dehydration
Genetic factors
Outside Temperature

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8/12/2023
References:
Waugh, A., Grant, A. (2009). Anatomy & Physiology (12th ed.). New york, USA: Elsevier