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Homeostasis Anatomy & Physiology
Nursing Theory and Role Development 8/12/2023 Homeostasis Anatomy & Physiology Muhammad Ziad Lecturer INS-KMU Peshawar
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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’
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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.
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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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8/12/2023 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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8/12/2023 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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Nursing Theory and Role Development
8/12/2023 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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8/12/2023 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
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Nursing Theory and Role Development
8/12/2023 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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Nursing Theory and Role Development
8/12/2023 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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8/12/2023 Cont…
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8/12/2023 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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8/12/2023 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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8/12/2023 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.
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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.
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Negative feedback cont…
Nursing Theory and Role Development 8/12/2023 Negative feedback cont…
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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
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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.
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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
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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
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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
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Positive Feedback Mechanism:
Nursing Theory and Role Development 8/12/2023 Positive Feedback Mechanism:
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Nursing Theory and Role Development
8/12/2023 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.
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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
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