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OBJECTIVES OF THE INTRODUCTORY COURSE Functional organization of the human body. Homeostasis. Describe the divisions of body fluids into intracellular, extracellular and intravascular compartments. Describe the structure of the cell membrane. Processes of transport across membranes. Resting Membrane Potentials Action Potentials Neuromuscular Transmission and Muscle Contraction. Skeletal muscles, properties Smooth Muscle, Special Properties Describe the general organization of the autonomic nervous system

Homeostatic Control Systems and cell membrane By Dr. Nazish

OBJECTIVES 1. Functional organization of the human body. 2. Homeostasis 3. Physiological control systems, negative feedback, positive feed back and feed forward mechanisms.

Maintenance of constant internal environment is called as homeostasis.

ECF 33% (14 liters) ICF Interstitial fluid 11.2 liters Plasma 2.8 liters

Factors homeostatically maintained Concentration of nutrient molecules. Concentration of oxygen and carbon dioxide. Concentration of waste products. Concentration of water salts and electrolytes. Volume and pressure Temperature.

Contribution of the body systems to homeostasis Circulatory system Digestive system Respiratory system Urinary system Skeletal system Integumantory system Nervous system Immune system Endocrine system Reproductive system

Extrinsic control system Intrinsic control system

Negative feedback opposes an initial change. The commonest control system. It maintains homeostasis. Components are: Sensor: monitors the magnitude of a controlled variable. Control center compares a sensor’s input with a set point. (Comparator) The effector makes a response to produce a desired effect.

Amna was performing tawaf in the month of June when she started feeling very hot because of increased body temperature. But after a lapse of few minutes she sweated profusely and started feeling better.

Compensatory response Deviation in controlled variable Controlled variable restored to normal Negative feedback Integrator (sends instructions to) Effector(s) Negative feedback to shut off the system responsible for the response (detected by) Sensor relieves

Fall in temperature below set point Increased heat production Through shivering and other means Negative feedback Temperature monitoring nerve cells Temperature control center Negative feedback mechanism Fall in the temperature below set point relieves

Amna was performing tawaf in the month of June when she started feeling very hot because of increased body temperature. But after a lapse of few minutes she sweated profusely and started feeling better. Which mechanism helped in bringing amna’s body temperature back to normal.

Fall in Blood Pressure below set point Increase in Blood Pressure to normal Negative feedback Cardiovascular control centers Heart and blood vessels Negative feedback to shut off the system responsible for the response Pressure monitoring nerve cells relieves

A 25 years old full term pregnant lady started having labour pains, she was taken to the gynecologist, after being examined she was admitted to the labour room. Intensity and severity of the labour pains kept on increasing, resulting in the dilatation of cervix. Cervix was dilated fully after strong labour pains of three hours. Finally she gave birth to a baby girl after a very strong uterine contraction

Positive feedback amplifies an initial change. An output is enhanced. A controlled variable moves in the direction of an initial change. Moves the controlled factor away from a steady state Less frequent Examples: 1.During the birth of a baby. 2.Depolarization beyond threshold during an action potential

Positive feedback Initial stimulus Response Positive feedback cycle Outside factor required to shut off + feedback cycle stimulus ↑ stimulus +

A 25 years old full term pregnant lady started having labour pains, she was taken to the gynecologist, after being examined she was admitted to the labour room. Intensity and severity of the labour pains kept on increasing, resulting in the dilatation of cervix. Cervix was dilated fully after strong labour pains of three hours. Finally she gave birth to a baby girl after a very strong uterine contraction. Which mechanism is responsible for causing increased intensity and frequency of labour pains?

Feed-forward control Allows the body to anticipate change and maintain stability Examples: 1.Watering of mouth ( Salivation ) as a result of sight, smell or thought of food 2.Rise in respiration before exercise 3.Increased secretion of Insulin as a result of presence of food in digestive tract  avoids excessive rise of glucose in blood after meal

Disruption in homeostasis can lead to illness and death. Pathophysiology is the abnormal functioning of the body during disease.

Summary Negative feedback: a change in a controlled variable triggers a response that opposes the change – driving the variable in opposite direction of the initial change. Positive feedback: a change in a controlled variable triggers a response that reinforces the change – driving the variable in the same direction as of the initial change. Feed forward: brings about a response in anticipation of a change in regulated variable

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