Introduction To Medical Physiology Lect 1

Physiology for Pharmacology

General Introduction Lecture ONE [email protected]

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Human Physiology Study of how the human body functions. Physiology = NORMAL Pathophysiology:  How

physiological processes are altered in disease or injury.

Main Goal of Physiology.  The

main goal is achievement of HOMEOSTASIS.  This is Maintaining constancy of internal environment.  Dynamic consistency.  Maintained by feedback loops. 

Definition of Homeostasis  Homeostasis,

from the Greek words for "same" and "steady," refers to any process that living things use to actively maintain fairly stable conditions necessary for survival…

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Internal components of homeostasis

1.Concentration of oxygen and carbon dioxide 2.pH of the internal environment 3.Concentration of nutrients and waste products 4.Concentration of salt and other electrolytes 5.Volume and pressure of extracellular fluid 

Control Systems Open systems are linear and have no feedback, such as a light switch. Closed Systems has two components: a sensor and an effector, such as a thermostat (sensor) and furnace (effector). Most physiological systems in the body use feedback to maintain the body's internal environment.

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Extrinsic Control System Most homeostatic systems are extrinsic: they are controlled from outside the body. Endocrine and nervous systems are the major control systems in higher animals.  The nervous system depends on sensors in the skin or sensory organs to receive stimuli and transmit a message to the spinal cord or brain.  Sensory input is processed and a signal is sent to an effector system, such as muscles or glands, that effects the response to the stimulus. 

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Intrinsic Control System  Local,

or intrinsic, controls usually involve only one organ or tissue.  When muscles use more oxygen, and also produce more carbon dioxide, intrinsic controls cause dilation of the blood vessels allowing more blood into those active areas of the muscles.  Eventually the vessels will return to "normal". 

Feedback Loops Sensor:  Detects

deviation from set

point. Integrating

center:

 Determines

the response.

Effector:  Produces 

the response.

The LOOP (Negative Phase)

The LOOP (Negative Phase)

Negative Feedback Mechanisms   

Defending the set point. Reverse the deviation. Produces change in opposite direction.

Example (Insulin Injection) {Negative FB}

So, in summary… Negative FB  

Positive Feedback  Action

of effectors amplifies the change.  Is in same direction as change.  Examples:  Oxytocin

(parturition).  Blood Cloting  Voltage gated Na+ channels (depolarization)

Note that… !! Most

of body activities and mechanisms for homeostasis are (( Negative FeedBack)), few are (( Positive FeedBack)).

In Positive FeedBack  

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Next Lecture

Cell

Physiology

Questions

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