32 Questions
What is the highest point of blood pressure during the cardiac cycle?
During ventricular systole
What is the main reason for the surge in blood pressure during ventricular contraction?
Blood enters the arteries faster than it can leave
What happens to the arterial walls during ventricular contraction?
They stretch to a wider diameter
What is the term for the rhythmic bulging of the artery walls with each heartbeat?
Pulse
What happens to the arterial blood pressure during diastole?
It decreases
What is the effect of vasoconstriction on blood pressure?
It increases blood pressure
What happens to the arterioles when smooth muscles relax?
Vasodilation occurs
What is the role of nitric oxide in blood vessels?
It induces vasodilation
What is the effect of gravity on blood pressure in the brain?
It decreases blood pressure
What is the typical blood pressure in the systemic circuit of a healthy 20-year-old human at rest?
120/70 mm Hg
What is the function of one-way valves and sinuses in a giraffe's neck?
To decrease blood pressure in the head
Why do some biologists believe that long-necked dinosaurs fed close to the ground?
Because they didn't have a heart powerful enough to generate high blood pressure
What is the function of valves inside veins?
To maintain unidirectional flow of blood
What happens to blood flow in the muscles during heavy exercise?
It increases
What is the role of the nervous system in regulating blood pressure?
It regulates the production of NO and endothelin
What is the function of rhythmic contractions of smooth muscles in the walls of venules?
To enhance the return of blood to the heart
What is the effect of vasodilation on blood pressure?
It decreases blood pressure
What is the primary function of endothelin in blood vessels?
To induce vasoconstriction
What happens to cardiac output during heavy exercise?
It increases to support increased blood flow
What is the significance of one-way valves in veins?
To prevent backflow of blood
What is the relationship between blood pressure and gravity?
Gravity decreases blood pressure
What is the term for the relaxation of smooth muscles in arterioles?
Vasodilation
What is the primary mechanism to maintain blood flow to the brain during changes in posture?
Fainting response
What is the significance of nitric oxide in blood vessels?
It induces vasodilation
What is the significance of rhythmic contractions of smooth muscles in venules?
To enhance return of blood to the heart
What is the significance of gravity on blood flow in the legs?
Gravity decreases blood flow
What causes the rhythmic bulging of the artery walls with each heartbeat?
The contraction of the ventricles
What is the term for the higher blood pressure that occurs when the heart contracts?
Systolic pressure
What happens to the diameter of arteries during ventricular systole?
It increases
What is the result of vasoconstriction on arterioles?
Increased blood pressure
Why is there a lower but still substantial blood pressure during diastole?
Because the arteries are elastic
What happens to blood flow into arterioles and capillaries during the cardiac cycle?
It remains continuous
Study Notes
Blood Pressure During the Cardiac Cycle
- Arterial blood pressure is highest during ventricular systole, known as systolic pressure
- Each ventricular contraction causes a spike in blood pressure, stretching the walls of the arteries, and can be felt as a pulse
- The pressure surge is partly due to the narrow openings of arterioles impeding the exit of blood from the arteries
- During diastole, the elastic walls of the arteries snap back, resulting in a lower but still substantial blood pressure (diastolic pressure)
Regulation of Blood Pressure
- Homeostatic mechanisms regulate arterial blood pressure by altering the diameter of arterioles
- Vasoconstriction (narrowing of arterioles) increases blood pressure upstream in the arteries
- Vasodilation (widening of arterioles) decreases blood pressure upstream in the arteries
- Nitric oxide (NO) is a major inducer of vasodilation, while endothelin is the most potent inducer of vasoconstriction
- Cues from the nervous and endocrine systems regulate the production of NO and endothelin in blood vessels
Blood Pressure and Gravity
- Blood pressure is generally measured for an artery in the arm at the same height as the heart
- For a healthy 20-year-old human at rest, arterial blood pressure is typically about 120 mm Hg at systole and 70 mm Hg at diastole
- Gravity has a significant effect on blood pressure, with blood pressure decreasing with increasing height
- The relationship between blood pressure and gravity is key to understanding fainting
- Fainting is triggered when the nervous system detects that the blood pressure in the brain is below the level needed to provide adequate blood flow
Adaptations to Gravity
- Animals with long necks require high blood pressure to overcome gravity and get blood to their brains
- A giraffe requires a systolic pressure of more than 250 mm Hg to get blood to its head
- Dinosaurs with long necks would have required even greater systolic pressure, but calculations suggest they did not have a heart powerful enough to generate such high pressure
- Some biologists believe that long-necked dinosaurs fed close to the ground rather than on high foliage
Blood Flow in Veins
- Gravity draws blood downward to the feet and impedes its upward return to the heart
- Valves inside the veins have an important function in maintaining the unidirectional flow of blood within these vessels
- The return of blood to the heart is further enhanced by rhythmic contractions of smooth muscles in the walls of venules
Learn about the changes in blood pressure during the cardiac cycle, including systolic pressure and arterial pressure. Understand how ventricular contractions affect blood pressure and how to feel the pulse. Test your knowledge with this quiz!
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