1. Draw and label a diagram of the heart showing the four chambers, associated blood vessels, valves and the route of blood through the heart.

2. State that coronary arteries supply heart muscle with oxygen and nutrients.

3. Explain the action of the heart in terms of collecting blood, pumping blood, and opening and closing of valves.

A. the heart: composed mainly of contractile muscle tissue, supported by connective, nerve, and epithelial tissues

B. collecting of blood:

• deoxygenated blood enters the right atrium from the inferior and superior vena cava
• oxygenated blood enters the left atrium from the pulmonary vein

C. pumping of blood:

• contraction of the atria (right and left) pumps the blood into the ventricles (right and left)
• contraction of ventricles (right and left) pumps the blood into the pulmonary artery(right) and aorta (left)

D. opening and closing of valves:

• as a function of pressure differences, one-way valves prevent backflow of blood
• atrioventricular valves prevent backflow from ventricles into atria
• semilunar valves prevent backflow of blood from pulmonary artery into right ventricle and from aorta into left ventricle

3. Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain and epinephrine (adrenaline).

A. heartbeat: electrical impulses cause regular contractions of, first the two atria, and then the two ventricles

B. pacemaker and myogenic muscle contraction:

• the sino-atrial node (SAN), known as the pacemaker, is a specialized set of cells located on the right atrium
• SAN, not the brain, generates regular electrical impulses autonomously
• SAN impulses spread throughout both atria, causing simultaneous contraction
• impulse spread to ventricles only at the atrio-ventricular node (AVN) with a delay of about 0.1 seconds
• AVN transmits electrical signals to heart apex via bundles of His
• signals trigger powerful contractions of both ventricles from the apex toward the atria
• bundle of His transmits electrical signals throughout ventricles via Purkinje fibers, causing simultaneous contraction of ventricles

C. nerve stimulation:

• sympathetic nerves from brain release epinephrine, increasing heart rate
• parasympathetic nerves from brain via vagus nerve decrease heart rate

D. hormone stimulation:

• adrenaline (epinephrine) from adrenal medulla increase heart rate

5. Explain the relationship between the structure and function of arteries, capillaries, and veins.

vessel 		      structure 		              	 function 
                  -inner endothelium			move blood away from heart
artery            -thick walls of smooth muscle 	under very high pressure
                  with elastic fibers		        (80-120 mm Hg) & high speed
                  -outer layer of connective tissue 	(10-40 cm/sec)
                  with elastic fibers

                  -inner endothelium			  move blood toward the heart
vein              -thin walls of smooth muscle	          under very low pressure
                  with elastic fiber                      (10 mm Hg) & moderate 
                  -outer layer of connective tissue 	  speed (5-20 cm/sec)
                  with elastic fibers
                  -valves		                 prevent backflow of blood

                  -thin single layer of endothelium   	allow diffusion of dissolved 
capillary         -surrounded by basement  		materials between blood & tissues 
                  membrane 		              	
                  -numerous		                under low pressure (20-40 mm Hg) 
							& low speed (< 1 cm/sec)

6. State that blood is composed of plasma, erythrocytes, leucocytes (phagocytes and lymphocytes), and platelets

7. State that the following are transported by the blood: nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat.

6.4: Lecture Notes