Body Systems: Circulatory/Immune Systems (The Beating Heart)

Question 1

The beating heart:

Answer 1

The stimulus that triggers a heartbeat is an electrical signal that originates from within the heart itself.

Question 2

Sinoatrial node (SA node):

Answer 2

-Bundle of specialized nerves and muscle tissue.
-Acts as a Pacemaker—sets rate of heartbeat (~70 bpm).
-Located in the wall of the right atrium.
-Generates electrical signal that spreads over the two atria and makes them contract simultaneously.

Question 3

Atrioventricular node (AV node):

Answer 3

-Located in the bottom of the right atrium.
-Receives electrical signal from SA node.
-Transmits signal through the bundle of His (bundle of specialized nerve fibres).
-Fibres relay signal through two branches of conducting fibres called pukinjie fibres.
-Left and right ventricles contract simultaneously.

Question 4

Monitoring heart function:

Answer 4

-Electrocardiogram (ECG): a device that records the electrical activity of the heart as it contracts and relaxes.
-Electrodes placed on body surface, connected to a recording device.

Question 5

Electrocardiogram:

Answer 5

-Graph that displays electrical impulses.
-Used to diagnose specific heart problems.
-Dead heart tissue will not conduct impulses, and produce abnormal line tracings.

Question 6

Heart sounds:

Answer 6

-Diastole: refers to heart relaxation (heart fills with blood).
-Systole: refers to heart contraction (heart pumping blood out).
-Lubb: sound produced when AV valves close. (When ventricles contract, blood is forced up and cause the AV valves to close).
-Dubb: sound produced when the semi-lunar valves close.

Question 7

Measuring blood pressure:

Answer 7

-Blood pressure.
-Measured in mm of Hg.
-2 measurements: systolic blood pressure and diastolic blood pressure.
1. Systolic blood pressure: pressure blood exerts during ventricular contraction.
•(~120 mm Hg).
2. Diastolic blood pressure: pressure blood exerts during ventricular relaxation.
•(~80 mm Hg).
-(120/80).

Question 8

Cardiac output and stroke volume:

Answer 8

-Cardiac output = amount of blood flowing from the heart each minute.
-Affected by:
1. Stroke volume:
•The quantity of blood pumped with each heart beat (~70 mL/beat).
2. Heart rate:
•Number of heart beats per minute. (~70bpm).

Question 9

Measuring cardiac output:

Answer 9

Cardiac output = stroke volume•heart rate
=70 mL/beat•70 beats/min.
Cardiac output = 4900 mL/min.
Increased cardiac output = increased blood flow.
Decreased cardiac output = decreased blood flow.

Question 10

Factors affecting cardiac output:

Answer 10

-Size of individual:
-Large mass = higher cardiac output.
-Smaller mass = smaller cardiac output.

Question 11

Exercise and cardiac output:

Answer 11

-Energy demand.
-Exercise heart rate increases to meet increase O2 demands.
-Regular cardiovascular training enlarges ventricular chambers, which increases the power to push blood out with each contraction (increase stroke volume).
-Stronger heart/more fit = lower heart rate = higher stroke volume.

Question 12

Blood pressure (what is it?):

Answer 12

Blood pressure is the pressure of circulating blood against the walls of blood vessels. It’s measured with a sphygmomanometer (blood pressure cuff).

Question 13

Regulating blood pressure:

Answer 13

-Nerve messages send to medulla oblongata (brain).

Question 14

Exercise (circulatory system):

Answer 14

-Can cause an increase in the production of metabolic products. (Like CO2, lactic acid, etc.).
-Accumulation in active tissues (like muscle), increased blood flow to area, greater nutrient supply, removal of toxins.