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.
What is vasomotion?
The on/off opening and closing of precapillary sphincters.
How does the velocity of blood flow change in the systemic circulation?
It is inversely proportional to the cross-sectional area of blood vessels.
What are the four routes of molecule movement across capillaries?
- Lipid soluble molecules diffuse through plasma membrane
- Small water soluble solutes move through intercellular capillary clefts or fenestrations
- Large molecules use active transport via pinocytotic vesicles
- Bulk flow occurs across capillary walls
What is net filtration pressure (NFP)?
The balance of all forces acting on a capillary bed.
What is hydrostatic pressure (HP)?
The force exerted by a fluid pressing against a wall.
What is colloid osmotic pressure (OP)?
The force created by large non-diffusible proteins in capillaries.
What is the effect of high blood pressure on urine production?
More urine is produced.
What is hypertension?
High blood pressure (130/80 or higher).
What is hypotension?
Low blood pressure (systolic pressure <100).
What is orthostatic hypotension?
Dizziness when getting up suddenly due to slow sympathetic response.
What is hypovolemic shock?
Shock due to large scale volume loss.
What is vascular shock?
Normal blood volume but poor circulation due to excessive vasodilation.
What is cardiogenic shock?
Shock resulting from an inefficient heart that cannot sustain adequate circulation.
