The Human Heart

Question 1

The heart

Answer 1

• The pump responsible for circulating blood throughout the body
• a hallow, muscular organ

Question 2

The heart is surrounded by what double layered protective sac

Answer 2

The pericardium (and the pericardial fluid)

Question 3

The three circulatory system subsystems

Answer 3

1. Systemic subsystem
2. Pulmonary subsystem
3. Cardiac subsystem

Question 4

Heart anatomy

Answer 4

• acts as a double pump
• Septum: muscular wall separating the right side (deoxygenated) from the left side (oxygenated)

Right side -> lungs (pulmonary subsystem)
Left side -> body (systemic & cardiac subsystems)

Question 5

4 chambers of the heart

Answer 5

• 2 atria: thin walled upper chambers
- receive blood from body via vines
- send blood to the ventricles
• 2 ventricles: thick walled lower chambers
- receive blood from atria
- send blood to body via arteries

Question 6

2 sets of valves

Answer 6

1. Atrioventricular valves (A-V)
   - between atria & ventricles
   - tricuspid (right)
   - bicuspid or mitral (left)
   - function: prevent back flow into atria when ventricles contract
2. Semilunar valves (S-L)
   - in arteries leaving ventricles
   - pulmonary S-L (right)
   - aortic S-L (left)
   - function: prevent back flow into ventricles as the arteries snap back

Question 7

Heart tissues

Answer 7

• myocardium = heart muscle
• endocardium = inner lining of the heart
• nervous tissue = there are 2 bundles of nerves that create electrical current that cause the walls of the heart to contract

Question 8

Blood pressure

Answer 8

• force of the blood in the walls of the arteries
• measured with a sphygmomanometer
• blood pressure reading:

Systolic pressure Average = 120
Diastolic pressure 80

-systolic: highest pressure caused when ventricles contract (blood is pushed out of heart)
-diastolic: lowest pressure when ventricles relax (heart fills with blood)

Question 9

Factors that influence blood pressure

Answer 9

• blood volume
• heart rate
• size of arteries
• elasticity of vessels
• viscosity of blood

Question 10

Heart rate and sound

Answer 10

• stethoscope: used to listen to heart
• average resting heart rate: 60-70 bpm; exercising 150 bpm

Heart sounds steps:
1. 2 atria contract -> A-V valves -> ventricles
2. 2 ventricles contract
a. A-V valves shut -> lub
b. S-L valves open into the -> arteries
3. High blood pressure in arteries forces S-L valves shut -> dub

Question 11

Cardiac cycle

Answer 11

• period between the start of one heartbeat and the beginning of the next (less than 1 sec)
• includes 2 phases for both atria & ventricles
- systolic (contraction)
- diastolic (relaxation)
• must be synchronized
• node - cluster of specialized nerve cells

Question 12

SA (sinoatrial) Node

Answer 12

➢ in the wall of the right atrium
➢ pacemaker
➢ sends out wave-like stimuli which :
1. cause both atria to contract
2. stimulate AV node

Question 13

AV (atrioventricular) node

Answer 13

➢ in the wall between right atrium & ventricle
➢ right & left atria contract
➢ stimuli travel quickly down Purkinje fibres
(down septum)
➢ cause both ventricles to contract

Question 14

Control of the Cardiac Cycle

Answer 14

SA node controlled by:
1. hormones (adrenaline)
2. balance of 2 nervous systems
a) sympathetic NS
● speeds up pacemaker during times of stress
(fight or flight)
b) parasympathetic NS
● slows down pacemaker during times of relaxation