PRINCIPLES OF PHYSIOLOGY

Optimal patient care requires the EMT - I to understand the basic principles of human physiology. The following topics will be discussed during this lesson.

· Body fluid distribution and movement

· Compensatory mechanisms for fluid loss

· Electrolyte function and distribution in the human body

· Blood components and function

· Composition of gases

· Clinical and biological death

· Metabolism

LESSON OBJECTIVES

At the completion of this lesson the participants will be able to:

1. Discuss and define the term homeostasis.

2. Identify the fluid compartments in the human body and discuss the distribution of fluids in each compartment.

3. Describe the initial compensatory response to acute fluid loss.

4. Identify signs and symptoms that can by used to determine hydration.

5. Identify 4 electrolytes and their function.

6. Identify 4 components of blood and discuss the function of each.

7. Name the two substances that are essential for brain function.

8. Differentiate between biological and clinical death.

9. Discuss the composition of environmental gas.

10. Differentiate between anaerobic and aerobic metabolism.

11. Discuss organ perfusion and identify the approximate time limits that the brain, heart, kidneys, and muscles can survive without being perfused.

KEY VOCABULARY

The following terms will be used during this lesson:

Anatomy - study of the structure of the human body.

Biological death - permanent brain death due to lack of O₂ (irreversible).

Clinical death - heart beat and respirations have stopped (may be reversible).

Diffusion - fluids or gases moving from an area of higher concentration to an area of lower concentration.

Fontanelles - the “soft spot” on a baby’s head.

Homeostasis - activity required to maintain balance between all body systems.

Osmosis - fluid movement across a semi-permeable membrane from an area of lower concentration to an area of higher concentration.

Pathophysiology - abnormal function.

Perfusion - the flow of oxygenated blood into or through an organ.

Physiology - the study of the function of the body.

Tachycardia - rapid heart beat.

Vasoconstriction - narrowing of the blood vessels.

KEY CONCEPTS

The following section provides information and space for taking notes on the key concepts discussed by the instructor.

Homeostasis

· Balance between the systems

· Maintained by the integration of activities between the body’s systems.

· Maintained primarily by the nervous system and endocrine system.

Body Fluid Compartments

· Intravascular - determines perfusion and blood pressure

· Interstitial - space between the cells

· Intracellular - fluid within the cells

Fluid Distribution

· Intravascular - 7.5%

· Interstitial - 17.5%

· Intracellular - 75%

Fluid Movement

· Osmosis

· Diffusion

Compensatory Mechanisms for acute fluid loss

· Tachycardia

· Diaphoresis

· Pallor

· Sunken fontanelle in infants

· Dry mucous membranes

· Poor skin turgor

· Decreased urine output

Electrolytes

· Sodium (Na)

· most common electrolyte

· mainly extracellular

· attracts water

· Potassium (K)

· mostly inside the cells

· maintains electrical stability of the heart

· Calcium (Ca)

· important for mechanical function of the muscles

· Bicarbonate (HCO₃)

· helps to maintain acid-base balance

Blood components

· White blood cells - important in fighting infection

· Red blood cells - important in transporting oxygen to the cells

· Platelets - important in blood clotting

· Plasma - liquid portion of the blood which acts as a transport mechanism

Cell function

· Oxygen

· Glucose

Biological death

· The brain can survive for 5 - 10 minutes without being perfused

· Brain cells will permanently die if they are not perfused

· The brain cells can not be restored once they are dead

Clinical death

· Heartbeat and respirations are absent

· If circulation and ventilation can be restored within 5-10 minutes the brain cells may suffer no permanent damage

· The basis for initiation of CPR

Environmental gases

· Oxygen - 21%

· Nitrogen - 78%

· Other - 1%

Metabolism

· Aerobic - metabolism that occurs in the presence of sufficient oxygen. The end product is a weak acid (carbonic acid) which is easily broken down into CO₂ and H₂0. These elements are quickly eliminated from the body by the lungs and kidneys.

· Anaerobic - metabolism that occurs without sufficient oxygen. The end product is a strong acid (lactic acid) which is difficult for the body to excrete.

Organ perfusion

The following organs can survive for limited periods of time without perfusion. It is essential to restore adequate perfusion as soon as possible if the organs are to maintain normal function.

· Brain – 5 -10 minutes

· Heart – 1-2 hours

· Kidneys – 1-2 hours

· Muscles – 1-2 hours

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