Cardiovascular System Pt.2 Flashcards
What is flow proportional to
The pressure gradient / Resistance
What is resistance proportional to
1/radius^4
Where is pressure the highest
In the aorta (decreases with distance due to resistance)
What is the key property/role of arterioles
Alter their diameter (paracrine factors, ANS) to vary vascular resistance and regulate the flow/distribution of blood to tissues
What is the key property/role of capillaries
Exchange of nutrients, wastes, etc. between blood and cells
What is the key property/role of veins
Compliance (less elastic and expand easier) that serve as a volume reservoir (~60% of blood here) –> Venous return (SNS and venoconstriction)
What do the right and left heart do
Each side functions as an independent pump
What is the key property/role of arteries
Elasticity (expansion and recoil) that maintains driving pressure
What is the key property/role of venules
To collect blood from capillaries
Where is blood primarily distributed during rest
To the liver and kidneys
What allows for variations in blood flow
Parallel arrangement of arterioles and changes in their diameter (vasoconstriction or dilation)
What is muscle tone of arterioles
How constricted or dilated they are
Which blood vessel has the thinnest walls
Capillaries
What is capillary density related to
The metabolic activity of cells (more capillaries where more energy and nutrients is required)
Which blood vessels have elastic tissue
Arteries (most) and veins
Which blood vessels have smooth muscle
Arteries, arterioles, and veins
Which blood vessels have fibrous muscle
Arteries, venules, and veins
Where is velocity of blood flow the lowest and why
Capillaries because they have a large cross-sectional area (lots of them) and it allows more opportunities for exchange
What is transcytosis
Moving things across cells using blood vessels –> Combination of endocytosis, vesicular transport, and exocytosis
How is most solute exchanged
Small dissolved solutes and gases move by simple or facilitated diffusion, and the larger solutes or proteins move by vesicular transport
What is bulk flow of blood comprised of
Filtration and absorption
What is filtration
Net flow from plasma to interstitial fluid
What is absorption
Net flow from interstitial fluid into plasma
What is net filtration pressure (NFP)
Hydrostatic pressure (Ph) - colloid osmotic pressure (*pi)
What is hydrostatic pressure
Blood pressure (MAP) that pushes water and solutes out of capillaries
What is colloid osmotic pressure
Due to plasma proteins, pulls water and solutes into capillary
What is the lymphatic system and what are its 3 functions
Vessels and nodes that returns filtered fluid and proteins to blood, filters out pathogens (at nodes), and absorbs fat in the small intestine
What is blood pressure
The pressure exerted by blood on walls of blood vessels
What does systolic pressure represent
Blood pressure during ventricular systole
What does diastolic pressure represent
Blood pressure during ventricular diastole
What is pulse pressure
Systolic - diastolic pressure
What does pulse pressure represent
The overall strength of the pressure wave (high-low)
What is mean arterial pressure (MAP)
Diastolic pressure + 1/3 pulse pressure
What does MAP reflect and indicate
The average driving pressure for blood flow to tissues that indicates if there’s enough pressure to diffuse all organs
Why is MAP closer to diastolic pressure than systolic pressure
Because diastole usually lasts twice as long as systole
What is MAP proportional to
Cardiac output (CO) * Total peripheral resistance (TPR)
What determines cardiac output
Stroke volume (SV) * Heart rate (HR)
What is total peripheral resistance
Resistance to flow offered by arterioles (variable)
What causes venoconstriction and what is the end effect
SNS uses NE/E to bind to alpha receptors and decrease diameter of veins, increasing venous return and MAP
What causes venodilation and what is the end effect
SNS uses NE/E to bind to beta-2 receptors, increasing vein diameter, decreasing venous return, and decreasing MAP
What determines stroke volume
Force of contraction in the ventricular myocardium (influenced by contractility and EDV)
What increases venous return
Venoconstriction, skeletal muscle pump, and respiratory muscle pump
What affect does blood volume have on MAP
Proportional
Where is blood pressure controlled
Cardiovascular system (rapid) and kidneys (slower)
What influences arterial resistance
SNS, hormones, and local control
How is the diameter of arterioles related to MAP
It is an inverse relationship
Why do arterioles need local control
For tissues to regulate their own blood supply instead of the entire body’s (e.g. when you cut your finger, it vasoconstrictor)
What 7 signals are used for local control of arterioles
Paracrine signals (NO, histamine, and active hyperemia, O2, CO2, H+, adenosine)
What is histamine and what does it do
Immune allergy response that causes local vasodilation of arterioles
What does active hyperemia do
Increase blood flow due to increased metabolic activity (decreased Oxygen, increased CO2, H+, and adenosine)
Is arteriolar resistance under antagonistic or tonic control
Tonic (only innervated by SNS –> ongoing/tonic release of NE/E)
Do the beta-2 receptors on arterioles affect systemic BP
No, it only comes into play in fight-or-flight states because its innervated by the SNS (changes blood flow to heart, liver, and skeletal muscle)
What types of receptors do arterioles have
Alpha-adrenergic for BP variance (more stimulation = vasoconstriction, less stimulation = vasodilation) and beta-2 for stress states and directing blood flow
What pathway is activated when NE/E binds to alpha-adrenergic receptors on arterioles
PLC
What makes up the cardiovascular control system and what does it do
Medulla oblongata coordinates reflex control of BP, distribution of blood to tissues, and HR
What is the main goal of the CVS control system
To maintain MAP and ensure adequate blood flow
What are baroreceptors
Stretch-sensitive mechanoreceptors
Where are baroreceptors located
Carotid arteries (blood to brain) and aorta (blood to the rest of the body)
Is the baroreceptor reflex response tonic or phasic and what kind of control does it exert
Tonically active, exerts antagonistic control
What is cardiovascular disease
Any disease that affects the heart and/or blood vessels
What are the 3 most common types of CVD
Coronary heart/artery disease, high blood pressure (hypertension), and cardiac arrest
What is coronary heart/artery disease
Blood flow to the myocardium is decreased due to fatty deposits (plaques cause atherosclerosis that narrows the lumen of coronary arteries and increases BP)
What are the consequences of CVD
Stroke or heart attack which can lead to death, long-term disability, or inability to work
What is a stroke
Blood flow stopped or interrupted
What are the steps in atherosclerosis
LDL (fatty streak) causes inflammation and narrowing (stable fibrous plaque), that then forms a clot (vulnerable plaque)
How often does the risk of CVD double looking at BP
With each 20/10 mmHg increase
What is essential hypertension
No clear cause other than heredity, mostly associated with increased peripheral resistance, and an adaptation of baroreceptors (less sensitive to stimuli)
What is the purpose of hemostasis
To stop blood loss from damaged vessels until reparation occurs (opposite of hemorrhage)
What are the 3 main phases of hemostasis
Vascular, platelet activation, and coagulation cascade
What happens once a blood vessels is repaired
Fibrinolysis (the clot is dissolved)
What happens in the 1st phase of hemostasis
Vasoconstriction in response to paracrine released by endothelium decreases pressure and flow to minimize blood loss as well as allow the initial plug to form
What happens in phase 2 of hemostasis
Platelets bind to exposed collagen and become activated (release platelet factors called cytokines to recruit more platelets and increase their stickiness) that results in platelet aggregation (platelet plug is a temporary blockage)
What happens in the last phase of hemostasis
Exposed collagen and tissue factor (from damaged cells) start forming fibrin protein mesh that stabilizes the platelet plug to form a clot (fibrin meshes with trapped RBCs) via the coagulation cascade
What happens during fibrinolysis
Cell growth and tissue repair from fibroblasts and endothelial cells while plasmin from liver dissolves fibrin into fragments
