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Anatomy & Physiology Homeostasis

Tanveer Saeed

Assistant Professor

AKU-SON

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Homeostasis

• The ability and tendency of certain systems to maintain a relatively constant internal state in spite of changes in external conditions.

• Homeostasis (a Greek term meaning same state), homeo- similar or same. stasis- standing or stopping. is the maintenance of constant conditions in the internal environment of the body despite large swings in the external environment.

Homeostasis

• Extracellular fluids ( ECF): Fluid outside body cells.

• Intracellular fluids ( ICF) : Fluid inside body cells.

Body’s internal environment……Interstitial fluid.

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Homeostatic Condition

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Examples of Homeostasis

• The regulation of the amounts of water and minerals in the body. This is known as osmoregulation. This happens in the kidneys.

• The removal of metabolic waste. This is known as excretion. This is done by the excretory organs such as the kidneys and lungs.

• The regulation of body temperature. This is mainly done by the skin.

• The regulation of blood glucose level. This is mainly done by the liver and the insulin secreted by the pancreas.

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Factors Disrupting Homeostasis

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Factors Effecting Homeostasis

•Nutrition

• Toxin

• Physical: Adequate rest, sunlight &exercise

• Psychological • Genetic/Reproductive

• Medical

• Stress

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Internal Components of Homeostasis

• Concentration of oxygen and carbon dioxide

• pH of the internal environment

• Concentration of nutrients and waste products

• Concentration of salt and other electrolytes

• Volume and pressure of extracellular fluid

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Sections of Homeostasis

• Feedback Systems in Homeostasis

• Body Systems and Homeostasis

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Mechanisms of homeostasis: feedback

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Operation of feed back system

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Negative feed back reverse a change in control conditions

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Negative Feedback Cont’d

• Negative feedback loops require a receptor, a control center, and an effector.

• A receptor is the structure that monitors internal conditions. For instance, the human body has receptors in the blood vessels that monitor the pH of the blood. The blood vessels contain receptors that measure the resistance of blood flow against the vessel walls, thus monitoring blood pressure. Receptors sense changes in function and initiate the body's homeostatic response.

Principle of Negative Feedback

Control

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Negative Feedback System or loop

• Negative feedback loops have been compared to a thermostatically controlled temperature in a house where the internal temperature is monitored by a temperature-sensitive gauge in the thermostat.

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Positive Feed Back

Positive feed back tend to strengthen a change in one

of the body control conditions Tanveer Saeed

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Positive feedback control Occurs when information produced by the feedback increases and accelerates the response.

• Positive feedback is less common in naturally occurring systems than negative feedback, but it has its applications.

Examples?????????????????

Positive Feedback System cont’d

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During uterine contractions, oxytocin is

produced. Oxytocin causes an increase in

frequency and strength of uterine

contractions. This in turn causes further

production of oxytocin, etc.

Biochemical control where the

accumulation of the product stimulates

production of an enzyme responsible for

that product's production.

Positive Feedback System

cont’d

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Examples of Homeostasis

• Excretion: removal of metabolic wastes by lungs & Kidneys

• Regulation of body temperature. done by the skin.

• Regulation of blood glucose level is mainly done by the insulin secreted by pancreas.

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Examples of Homeostasis

• Functions such as blood pressure, body temperature, respiration rate, excretion and blood glucose levels are maintained within a range of normal values around a set point despite constantly changing external conditions.

• when the external temperature drops, the body's homeostatic mechanisms make adjustments that result in the generation of body heat, thereby maintaining the internal temperature at constant levels.

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Examples

• Thermal regulation: • The skeletal muscles can shiver to produce heat if the body

temperature is too low.

• Non-shivering thermogenesis involves the decomposition of fat to produce heat.

• Sweating cools the body with the use of evaporation.

• Chemical regulation • The pancreas produces insulin and glucagon to control blood-

sugar concentration.

• The lungs take in oxygen and give off carbon dioxide.

• The kidneys remove urea, and adjust the concentrations of water and a wide variety of ions.

• Most of these organs are controlled by hormones secreted from the pituitary gland, which in turn is directed by the hypothalamus.

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Advantages of Homeostasis

• Homeostasis has survival value because it means an animal can adapt to a changing environment. It can deal with the temperature difference you face when you step our your front door.

• The body will attempt to maintain a norm, the desired level of a factor to achieve homeostasis. However, it can only work within tolerable limits, where extreme conditions can disable the negative feedback mechanism

• In these instances, death can result, unless medical treatment is executed to bring about the natural occurrence of these feedback mechanisms

Resources

Ross, & Wilson. (2010). Anatomy & Physiology in Health & Illness

(11th ed). Edinburgh: Churchill.

Arthur C. Guyton, M.D. (2006). Medical Physiology (11th ed).

Washington: Kirokawa.

Tortora, Gerad J. (2006). Principles of Human Anatomy and

Physiology (12th ed).

New York: Happer & Row.

Scanlon, V.C., & Sanders. T. (2002). Essentials of Anatomy &

Physiology (8th ed).

Philadelphia: F.A. Davis Company.

http://higheredbcs.wiley.com/legacy/college/sarafino/0470129166/ani

mations/homeo1a/frameset.htm

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KEY TERMS

Receptor • —A structure that monitors the body's internal functions and conditions; detects changes in the

body's internal environment. Set point • —The range of normal functional values of an organ or structure. 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.

Effector • —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 and is typically active in low concentrations. Negative feedback loop • —A homeostatic mechanism that opposes or resists a change in the body's internal conditions. Positive feedback loop • —A mechanism that increases or enlarges a change in the body's internal conditions.

KEY TERMS FOR HOMEOSTASIS Cont’d

Hormone Chemical regulator or messenger of physiology,

growth, or development which is typically synthesized in one region of the body and active in another and is typically active in low concentrations.

Negative feedback loop A homeostatic mechanism that opposes or resists a

change in the body's internal conditions.

Positive feedback loop A mechanism that increases or enlarges a change in

the body's internal conditions.

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