1. The Heart
Section 11.4

2. The Circulatory System Cont’d…
Learning Goal: To explore the circulatory system.
Success Criteria:
I know I am succeeding when I can…
describe the basic structure of the heart
trace the routes of both the pulmonary and systemic circuits
summarize the events that take place during a cardiac cycle

3. The Heart
the heart is made up of cardiac muscle, nerve and connective tissue
cardiac muscle contracts and relaxes to pump blood around the body (Beats times per day!)
since the heart requires a lot of energy it has its own coronary blood vessels that supply oxygen to the muscle cells
epithelial tissue called the pericardium covers the inside and outside of heart providing protection and low-resistance surfaces

4. The Heart Cont’d…

5. The Heart Cont’d…
septum: separates the heart into two parallel pumps, each with an atrium and a ventricle
atria: receives blood and pumps blood into the ventricles
ventricles: pumps blood out of the heart (have thicker walls because they have to pump the blood over much longer distances and through capillary networks)
valves: ensure that blood flows in only one direction

6. The Heart Cont’d…
the right side of the heart circulates blood to the pulmonary circuit, which delivers oxygen to the lungs
the left side of the heart receives this blood and pumps it out through the systemic circuit, which delivers the rest of the body

7. Circulation
deoxygenated blood from the body enters the right atrium of the heart
the right atrium contracts forcing the blood into the right ventricle
right ventricle contracts forcing the blood out through the pulmonary arteries to the lungs

8. Circulation Cont’d…
oxygen diffuses into the blood as it passes through the capillary networks in the lungs

9. Circulation Cont’d…
oxygenated blood from the lungs enters the left atrium through the pulmonary veins
left atrium contracts squeezing blood into the left ventricle
left ventricle contracts and forces blood out through the aorta (the largest artery)

10. Circulation Cont’d…
blood passes through the capillary networks in the body tissues and oxygen diffuses out of the blood into the cells
deoxygenated blood enters the veins and enter the right atrium
Then the cycle begins again!

11. The Cardiac Cycle
cardiac cycle: the contractions and relaxations of the heart muscles during a complete heartbeat
two basic phases:
diastole: the period of relaxation and filling of the heart with blood
systole: the period of contraction and emptying of the heart

12. Heart Sounds
the “lubb-DUBB” sound of the heartbeat is caused by the closing of the heart valves
first sound (“lubb”) occurs when the atrioventricular valves close as the ventricles begin to contract
second sound, the DUBB part, occurs as the ventricles relax and the semilunar valves snap shut

13. Regulation of Heart Rhythm Cont’d…
when a heart is removed from a live animal, it continues to beat for a short time
the heart has myogenic muscle, muscle that can contract and relax without input from an external source
safety mechanism that ensures that the heart will continue to beat even if the nervous system is damaged
Th is explains why the heart continues to beat in a person who has severe brain injury or has been pronounced “brain dead.”

14. Regulation of Heart Rhythm Cont’d…
sinoatrial (SA) node: a mass of muscle and nerve cells in the right atrium; initiates the heartbeat and maintains the regular rhythm
atrioventricular (AV) node: a mass of conducting cells that transmits the signals from the SA node to the muscles of the ventricles
purkinje fibre: a conducting fibre that carries the electrical signals from the AV node to the muscle cells of the ventricles
Th is explains why the heart continues to beat in a person who has severe brain injury or has been pronounced “brain dead.”

15. Regulation of Heart Rhythm
the heart rate can be adjusted by the nervous systems
Th is explains why the heart continues to beat in a person who has severe brain injury or has been pronounced “brain dead.”

16. Regulation of Heart Rhythm
sympathetic nervous system:
controls processes in the body in preparation for stress (“fight or flight” system)
signals from the brain through this system cause the heart rate to increase which increases the flow of blood and oxygen to areas of the body where it is needed
parasympathetic nervous system:
controls processes when the body is in rest(“rest and digest” system)
when stress is no longer present, the brain sends signals through the parasympathetic nervous system and the heart rate returns to normal
Th is explains why the heart continues to beat in a person who has severe brain injury or has been pronounced “brain dead.”

17. Regulation of Heart Rhythm
Th is explains why the heart continues to beat in a person who has severe brain injury or has been pronounced “brain dead.”

18. Regulation of Heart Rhythm Cont’d…
Factors that affect heart rate:
emotional stress
physical stress such as being overweight
physical activity
drugs (ex. caffeine and nicotine)
medical conditions
Th is explains why the heart continues to beat in a person who has severe brain injury or has been pronounced “brain dead.”

19. Homework
11.4 Questions #1-7