Human physiology

Human physiology IntroductionPrepared by:

Dr.Sayed Zulfiqar Ali Shah

LECTURER RMI-CRSDPT KMUMSPT KMU

LECTURE-1What is physiology?

10/6/20152Introduction The word Physiology is derived from Ancient greek (physis)meaning "nature, origin", and (logia), meaning "study of

Physiology is the study of the human body functions under normal conditions.

You use physiology when you exercise, read, breathe, eat, sleep, move or do just anything.

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The goal of physiology is to explain the physical and chemical factors that are responsible for the origin, development, and progression of life. Each type of life, from the simple virus to the largest tree or the complicated human being, has its own functional characteristics (Guyton, 11th ed page 3)Why we study physiology?10/6/2015

The basic living unit of the body is the cell Each type of cell is specially adapted to perform one or a few particular functions. The entire body, then, contains about 100 trillion cells.Great acts are made up of small deeds.-Lao Tzu 10/6/2015 Subatomic Particles electrons, protons, and neutrons Atom hydrogen atom, lithium atom, etc. Molecule water molecule, glucose molecule, etc. Macromolecule protein molecule, DNA molecule, etc. Organelle mitochondrion, Golgi apparatus, nucleus, etc. Cell muscle cell, nerve cell, etc. Tissue epithelia, connective, muscle and nerve Organ skin, femur, heart, kidney, etc. Organ System skeletal system, digestive system, etc. Organism the humanLevel of organization10/6/2015Levels of Organization

Subatomic particlesatommoleculesmacromoleculesorganellecellTissue Organ System Organism 10/6/2015organismOrgan Systems

Cardiovascular systemLymphatic system10/6/2015Organ Systems

Digestive systemRespiratory systemUrinary system10/6/2015 Movement change in position; motion Responsiveness reaction to a change Growth increase in body size Respiration obtaining oxygen; removing carbon dioxide; releasing energy from foods Reproduction production of new organisms and new cellsCharacteristics of life10/6/2015Characteristics of Life Absorption passage of substances through membranes and into body fluids Circulation movement of substances in body fluids Assimilation changing of absorbed substances into chemically different forms Excretion removal of wastes produced by metabolic reactions Digestion breakdown of food substances into simpler forms 10/6/2015 Maintenance of Life Life depends on five (5) environmental factors: Water Food Oxygen Heat Pressure10/6/2015HOMEOSTASISHomeostasis means 'keeping things constant', and comes from two Greek words homeo, meaning 'similar' and stasis, meaning 'stable'.

It is characteristic of an organism that regulates its internal environment.

Homeostasis is a condition of equilibrium in the bodys internal environment produced by the nonstop activity of all the bodys regulatory systems.

Maintaining the internal environment within physiological limits

Exampleblood glucose level is kept within narrow range

10/6/2015Body FluidsFor the bodys cells to survive, the composition of the surrounding fluids must be precisely maintained at all times.

INTRACELLULAR FLUID:Fluid inside body cells is called intracellular fluid.

EXTRACELLULAR FLUID:Fluid outside body cells is called extracellular fluid (ECF) and is found in two principal places.

ECF filling the narrow spaces between cells of tissues is called interstitial fluid, intercellular fluid, or tissue fluid.

ECF in blood vessels is termed plasma.

Since ECF is in constant motion throughout the body and also surrounds all body cells, it is often called the bodys internal environment.10/6/2015Control of HomeostasisHomeostasis is continually being disrupted byexternal stimuliintense heat, cold , and lack of oxygeninternal stimulipsychological stressesExercise

Disruptions are usually mild & temporary

If homeostasis is not maintained, death may result10/6/201515CONTROL OF HOMEOSTASISHomeostatic imbalances occur because of disruptions from the external or internal environments.Homeostasis is regulated by the nervous system and endocrine system, acting together or independently.

The nervous system detects changes and sends nerve impulses to counteract the disruption.

The endocrine system regulates homeostasis by secreting hormones.

Whereas nerve impulses cause rapid changes, hormones usually work more slowly.

Examples: CO2, O2, temperature, pH, blood pressure, 10/6/2015Components of Feedback LoopReceptor monitors a controlled conditionControl center determines next actionEffectorreceives directions from the control centerproduces a response that changes the controlled condition

Feedback SystemsGeneral PrinciplesA self-regulatory biological system in which the output or response affects the input, either positively or negatively.

A feedback system is a cycle of events in which information about the status of a condition is continually monitored and fed back (reported) to a central control region .Any disruption that changes a controlled condition is called a stimulus.

10/6/2015Feedback SystemsA feedback system consists of three basic components.A receptor: monitors changes in a controlled condition and sends input in the form of nerve impulses or chemical signals to a control center.

The control center: Set the range of values within which a controlled condition should be maintainedevaluates the input it receives from the receptors, and generates output commands when they are needed.

An effector: Is a body structure that receives output from the control center and produces a response or effect that changes the controlled condition.

10/6/2015Feedback SystemsWe have two types of feed back systems:

NEGATIVE FEEDBACK SYSTEM.If a response reverses the original stimulus, the system is a negative feedback system.

POSITIVE FEEDBACK SYSTEM.If a response enhances the original stimulus, the system is a positive feedback system.10/6/2015Negative Feedback SystemsA negative feedback system reverses a change in a controlled condition.

Example of Negative Feedback Homeostasis of Blood Pressure (BP): The activity of the effector produces a result, a drop in blood pressure, that opposes the stimulus, an increase in blood pressure.10/6/2015Homeostasis of Blood PressurePressure receptors in walls of certain arteries detect an increase in BP

Brain receives input and then signals heart and blood vesselsHeart rate slows and arterioles dilate (increase in diameter)

BP returns to normal

Positive Feedback SystemThe positive feedback system reinforces a change in a controlled condition

Normal childbirth provides a good example of a positive feedback system

10/6/2015Positive Feedback during ChildbirthStretch receptors in walls of the uterus send signals to the brain

Brain releases a hormone (oxytocin) into bloodstream

Uterine smooth muscle contracts more forcefully

More stretch more hormone more contraction etc.

The cycle ends with birth of the baby & decrease in stretch

10/6/2015Homeostatic ImbalancesHomeostatic imbalance occurs when the human bodys internal environmental variables become disturbed. The homeostatic imbalance can be caused byaging of the persons organs the organs control systems or feedback mechanismsPathological situations(diseases)10/6/201525Aging and HomeostasisAging is characterized by a progressive decline in the bodys responses to restore homeostasisThese changes are apparent in all body systems.crinkled skin, gray hair, loss of bone mass, 10/6/201510/6/2015