Download 10.3 assignment answers

Chapter 10
Name:______________________________Date:_________Period:___________
1. Describe the steps in the cardiac cycle:
1)The two atria contract
2)The two ventricles contract
3)The heart relaxes
2. How are heart sounds generated during a cardiac cycle (see Fig 10.13)?
a. When the atria contract, the ventricles are relaxed and filling with blood.
b. When the ventricles contract, the atrioventricular valves close and vibrate, preventing blood from
flowing back into the atria and producing the longer, low-pitched “lub” sound of the heartbeat.
c. After the ventricles contract, the shorter and sharper “dub ” sound of the heartbeat results from the
closing of the semilunar valves to when the back pressure prevents arterial blood from flowing back
into the ventricles.
3. Define
a) systole:
• contraction of the heart muscle (ventricle)
b) diastole
• relaxation of the heart muscle (ventricle)
4. The heart is able to contract and relax rhythmically due to the presence of nodal tissue, a type of
cardiac muscle (with both muscle and nerve characteristics). Describe the impulses in the SA node
and the AV node. Include the AV bundle in your description in describing the conduction system of
the heart.
a) Sinoatrial Node:
The SA node (the pacemaker located in the upper dorsal wall of the atrium) initiates the heartbeat. It
sends out a stimulus (an excitation electrical impules, every 0.85s), which causes the atria to
contract. It also stimulates the AV node
b) Atrioventricular node
Th SA stimulus reaches the AV node in the base of the right atrium near the septum. The AV node
signals the ventricles to contract. Impulses pass down the two branches of the atrioventricular bundle
to the Purkinje fibres, and thereafter the ventricles
5. Draw the diagram of a normal ECG (electrocardiogram). Label P,Q,R,S,T as in Figure 10.14 and
describe what happens at P, QRS, and T
Electrical stimulation just prior to:
P: atrial contraction (in atrial muscle nerve fibres)
QRS: ventricle contraction (in ventricle muscle nerve fibres)
T: system reset as ventricles (in ventricle muscle nerve fibres)
6. Describe the arrhythmias (abnormalities) below that can be detected by an ECG:
a) Atrial Fibrillation
multiple, chaotic impulses are generated from the AV node, causing an irregular, fast heartbeat
b) Ventricular Fibrillation
uncoordinated contraction of the ventricles; This is more serious as blood is not being pumped out
of heart effectively. It can occur after a heart attack, injury, or drug overdose
7. What can be used to administer an electrical shock to the chest?
Automatic external defibrillators(AEDs) can be used to administer an electrical current/shock to the
chest
Use this area to practice drawing all the blood vessels and heart chambers that blood passes through
on its journey through the heart.