The heart’s internal pacemaker beats by:
- an internal implant that sends an electrical impulse through the heart
- the excitation of cardiac muscle cells at the sinoatrial node followed by the atrioventricular node
- the excitation of cardiac muscle cells at the atrioventricular node followed by the sinoatrial node
- the action of the sinus
During the systolic phase of the cardiac cycle, the heart is ________.
- contracting and relaxing
- filling with blood
Cardiomyocytes are similar to skeletal muscle because:
- they beat involuntarily
- they are used for weight lifting
- they pulse rhythmically
- they are striated
How do arteries differ from veins?
- Arteries have thicker smooth muscle layers to accommodate the changes in pressure from the heart.
- Arteries carry blood.
- Arteries have thinner smooth muscle layers and valves and move blood by the action of skeletal muscle.
- Arteries are thin walled and are used for gas exchange.