chapter 21 Flashcards
what are the 5 classes of blood vessels?
- Arteries:
- carry blood away from the heart - Arterioles:
- are smallest branches of arteries - Capillaries:
- are smallest blood vessels
- location of exchange between blood and interstitial fluid - Venules:
- collect blood from capillaries - Veins:
- return blood to heart
The Largest Blood Vessels
Attach to heart
Pulmonary trunk:
- carries blood from right ventricle
- to pulmonary circulation
Aorta:
- carries blood from left ventricle
- to systemic circulation
Arteries and Veins
Walls have 3 layers:
- tunica intima
- tunica media
- tunica externa
Tunica Externa
In arteries:
- contain collagen
- elastic fibers
In veins:
- contain elastic fibers
- smooth muscle cells
Arteries vs. Veins
Arteries and veins run side-by-side
- Arteries have thicker walls and higher blood pressure
- Collapsed artery has small, round lumen
- Vein has a large, flat lumen
Arteries vs. Veins pt. 2
Vein lining contracts, artery lining does not
Arteries more elastic
Veins have valves
Contractility
- Arteries change diameter
- Controlled by sympathetic division of ANS
Vasoconstriction - DECREASING the diameter of a blood vessel
Vasodilation - INCREASING the diameter of a blood vessel
Artery Characteristics
From heart to capillaries, arteries change:
- from elastic arteries
- to muscular arteries
- to arterioles
Elastic Arteries
Also called conducting arteries
- large vessels (e.g. pulmonary trunk and aorta)
- Tunica media has many elastic fibers and few muscle cells
- elasticity evens out pulse force
Muscular Arteries
- Also called distribution arteries
- are medium-sized ( most arteries )
- Tunica media has many muscle cells
Arterioles
Are small
- have little or no tunica externa
- have thin or incomplete tunica media
Aneurysm
- A bulge in an arterial wall
- is caused by weak spot in elastic fibers
- pressure may rupture vessel
Capillary Function
location of all exchange functions of the cardiovascular system
- materials diffuse between blood and interstitial fluid
Capillary Structure
- Endothelial tube, inside thin basal lamina
- No tunica media
- No tunica externa
- Diameter is similar to red blood cell
Veins vs. Arteries
Veins:
- are larger in diameter
- have thinner walls
- Carry lower blood pressure
3 Vein Categories (1.)
Venules:
- very small veins
- collect blood from capillaries
3 Vein Categories (2.)
Medium-sized veins:
- thin tunica media and few smooth muscle cells
- tunica externa with longitudinal bundles of elastic fibers
3 Vein Categories ( 3.)
Large veins:
- have all 3 tunica layers
- thick tunica externa
- thing tunica media
Vein Valves
- Folds of tunica intima
- Prevent blood from flowing backward
- Compression pushes blood toward heart
Blood Distribution
Heart, arteries, and capillaries:
- 30-35% of blood volume
Venous system:
- 60-65%
Pressures in the Systemic Circuit
Systolic pressure:
- peak arterial pressure during ventricular systole
Diastolic pressure:
- minimum arterial pressure during diastole
Pressures in the Systemic Circuit
(pt.2 )
Pulse pressure:
systolic pressure - diastolic pressure = pulse pressure
Mean arterial pressure (MAP):
MAP = diastolic pressure + 1/3 pulse pressure
Cardiovascular regulation
Change blood flow to a specific area:
- at an appropriate time
- in the right area
- without changing blood flow to vital organs
3 regulatory mechanisms
Control cardiac output and blood pressure:
1. AutoregulationL
- causes immediate, localized homeostatic adjustments
- Neural mechanism:
- respond quickly to changes at specific sites - Endocrine mechanisms:
- direct long-term changes
The Endocrine System
- Hormones have short-term and long-term effects on cardiovascular regulation
- e.g. E and NE, hormones produced by adrenal medullae
ANP and BNP
Atrial natriuretic peptide (ANP):
- produced by cells in right atrium
Brain natriuretic peptide (BNP):
- produced by ventricular muscle cells
ANP and BNP
Respond to excessive diastolic stretching
- lower blood volume and blood pressure
- reduce stress on the heart
Patterns of Cardiovascular Response
blood, heart, and cardiovascular system:
- work together as unit
- respond to physical and physiological changes (e.g. exercise, blood loss)
- to maintain homeostasis
3 Effects of Light Exercise
- Extensive vasodilation occurs:
- increasing circulation - Venous return increases:
- with muscle contractions - cardiac output rises:
- due to rise in venous return and atrial stretching
5 Effects of Heavy Exercise
- Activates the sympathetic nervous system
- Cardiac output increases to maximum:
- about 4 times the resting level - Restricts blood flow to “nonessential” organs (e.g. digestive system)
- Redirects blood flow to skeletal muscles, lungs, and heart
- Blood supply to brain is unaffected
Responses to Severe Blood Loss
Also called hemorrhaging
- Entire cardiovascular system adjusts to:
- maintain blood pressure
- restore blood volume
3 short-term responses to hemorrhage
To prevent a drop in blood pressure:
1. carotid and aortic reflexes:
- increases cardiac output (increasing heart rate)
- cause peripheral vasoconstriction
3 short-term responses to hemorrhage (pt.2)
Sympathetic nervous system:
- triggers hypothalamus
- further constricts arterioles
- vasoconstriction improves venous return
3 short-term responses to hemorrhage (pt.3)
Hormonal effects:
- increase cardiac output
- increase peripheral vasoconstriction (E, NE, ADH, angiotensin II)
Shock
- Short-term responses compensate up to 20% loss of blood volume
- Failure to restore blood pressure results in shock
4 long-term responses to hemorrhage
Restoration of blood volume can take several days:
1. Recall of fluids from interstitial spaces
2. Aldosterone and ADH promote fluid retention and reabsorption
3. Thirst increases
4. Erythropoietin stimulates red blood cell production
Blood Flow to the Brain
- is top priority
- the brain has high oxygen demand
- when peripheral vessel constrict, cerebral vessels dilate, normalizing blood flow
Blood Flow to the Heart
- through coronary arteries
- oxygen demand increases with activity
Lactic acid and low O2 levels: - dilate coronary vessels
- increases coronary blood flow
Blood flow to the heart
Epinephrine: Adrenaline
- dilates coronary vessels
- increases heart rate
- strengthens contractions
Heart Attack
- A blockage of coronary blood flow
Can cause: - angina
- tissue damage
- heart failure
- death
Aging and the Cardiovascular System
Cardiovascular capabilities decline with age
Age-related changes occur in:
- blood
- heart
- blood vessels
5 Age-related changes in the heart
- Reduced maximum cardiac output
- Changes in nodal and conducting cells
- Reduced elasticity of fibrous skeleton
- Progressive atherosclerosis
- Replacement of damaged cardiac muscle cells by scar tissue
3 Age-related changes in blood
- Arteries become less elastic:
- pressure change can cause aneurysm - Calcium deposits on vessel walls:
- can cause stroke or infarction - Thrombi can form:
- at atherosclerotic plaques
