Ch. 20-2 Blood Vessels Flashcards
What is essential for body organs to function properly?
Maintaining a steady flow of blood from the heart
This is vital for homeostasis.
What three factors determine blood pressure?
- Cardiac output
- Peripheral resistance
- Blood volume
How are changes in blood pressure compensated?
Changes in one variable are compensated by changes in another variable to maintain homeostasis.
What are the two types of blood pressure regulation?
- Short-term regulation by the nervous system and hormones
- Long-term regulation by the kidneys
What are the two goals of neural controls in short-term blood pressure regulation?
- Maintaining adequate BP by altering blood vessel diameter
- Altering blood distribution to respond to specific organ demands
What do baroreceptors detect?
Mechanical pressure through stretch in blood vessels.
Where are baroreceptors primarily located?
- Aorta
- Carotid sinus
- Major arteries of neck and thorax
What happens when baroreceptors sense too much pressure?
Stimulates vasodilation of arteries, decreasing return of blood to the heart.
What do chemoreceptors generally detect?
Changes in blood levels of O2, H+, or CO2.
What is the effect of increased H+ levels detected by chemoreceptors?
Causes vasoconstriction and increased resistance, leading to a rise in blood pressure.
What are some key hormones involved in short-term blood pressure responses?
- Norepinephrine
- Epinephrine
- Angiotensin II
- Antidiuretic hormone (ADH)
- Atrial Natriuretic Peptide (ANP)
What is the role of angiotensin II in blood pressure regulation?
Stimulates intense vasoconstriction and increases blood pressure rapidly.
What does ADH do in terms of blood pressure?
Makes kidneys conserve water and can increase blood pressure by causing vasoconstriction.
What is the direct renal mechanism for blood pressure control?
High blood volume or BP leads to increased urine production.
What triggers the release of renin in the indirect renal mechanism?
When blood pressure falls.
What are the four ways angiotensin II stabilizes arterial blood pressure?
- Stimulates aldosterone release
- Causes ADH release
- Triggers thirst sensation
- Acts as a potent vasoconstrictor
What is tissue perfusion?
Blood flow through body tissues.
What are the functions of tissue perfusion?
- Delivery of O2 and nutrients
- Removal of CO2 and waste
- Lung gas exchange
- Absorption of nutrients in digestive tract
- Urine formation in kidneys
What is autoregulation in blood flow?
Each tissue regulates its own blood supply by varying resistance of arterioles.
What are the two mechanisms of autoregulation?
- Myogenic (physical)
- Chemical (metabolic)
What triggers the myogenic response?
Stretching of smooth muscle in arterioles.
What conditions stimulate the opening of precapillary sphincters?
- Decreased O2 concentrations
- Increased CO2 concentrations
- Increased levels of lactic acid
- Increased concentrations of K+ or H+
- Inflammatory chemicals and increased body temperature
What is the role of nitric oxide in blood flow?
It is a powerful vasodilator released from endothelial cells.
What causes the closing of precapillary sphincters?
Opposite levels of regulators, prompting the release of endothelin.
