Cardiovascular system - Beye Flashcards
What is the cardiovascular function of vessels?
- distribution of blood to meet metabolic demands
- enable exchange/ delivery of nutrients, wastes, hormones
- role in heat regulation
- essential for hemostasis (clotting)
- modulating inflammatory responses
What is the organization of the CV system?
- arteries carry blood away from the heart -> can become/ branch arterioles then capillaries
- capillaries is where exchange occurs -> capillaries reunite to form venules and then veins
- veins carry blood back to the heart
Describe where the highest and lowest blood pressure occur?
- highest pressure in arteries, lowest in veins -> high to low, blood will flow
- highest at systolic pressure = ~120
- lowest at diastolic pressure= ~80
- 120/80 = normal
How do blood pressure cuffs work?
If inflated above systolic pressure -> don’t hear anything = no blood flow
-> then slowly release -> pressure drops until reaches systolic pressure = blood starts to flow during artery opening, can hear turbulent flow because of partial opening - how you know you’ve reached systolic pressure
-> then flow becomes smooth (don’t hear anything = laminar flow)
-> artery will collapse again during diastole -> start to hear vessel sounds because blood flows in turbulent manner in partially collapsed vessel
How do you calculate mean arterial pressure?
MAP = diastolic + 1/3 (systolic - diastolic)
* systole is shorter than diastole, thus diastole has greater influence on MAP
What is the pressure like in the pulmonary cardiovascular system?
- pulmonary circulation is very low pressure
- systole pressure usually 20 or less
- not a lot of resistance
- no gravitation force against
- not much distance to go
What is the anatomy of a blood vessel?
- Outer layer = tunica adventitia. Fibrous connective tissue. Blood vessels, nerves, lymphatics.
- Middle layer = tunica media. Smooth muscle (innervated by SNS), elastin (stretching fiber), collagen. Where changes to blood flow can occur.
- Innermost layer = tunica intima. Endothelial cells.
- tunica means layer
- exception: capillaries only have the innermost layer
What is endothelium cross talk?
Critical for homeostasis
- possess many receptors (respond to signals)
- secrete vasoactive substances (influence activity of smooth muscles)
- also act as force sensors (know the pressure blood is under + whether laminar/ turbulent flow) -> can change structure, gene expression based on flow dynamics
Describe the structure, blood characteristics and purpose of arteries
Distribution vessels
Structure: large diameter, thin walls compared to diameter (1/4 wall), lots of elastic fibres -> easy to distend/ stretch -> get continous flow, comes in, arteries stretch, heart pumps blood, then you get recoil from the stretch so blood continues to flow even without heart
Blood characteristics: very high blood pressure, high blood flow, small drop in pressure (low resistance), high blood velocity (highest)
Purpose: “shock absorbers” -> absorb pulsatile wave (absorb energy)
What is atherosclerosis? List some examples.
An artery disease
- deposits occur already in first decade of life
- as it progresses, it can impede blood flow - usually due to rupture/ clot -> important organs don’t get blood
- consequences depend on artery: coronary artery disease = heart attack/damage, cerebrovascular disease = stroke, peripheral artery disease = leg pains, muscles don’t get appropriate flow)
- in innermost layer, get build-up of cholesterol -> then white blood cells come in, try to phagocytose the cholesterol, become bigger and become foam cells -> can die and cholesterol is deposited -> cholesterol can harden to form calcium deposits
Describe the structure, blood characteristics and purpose of arterioles
Resistance vessels
Structure: small diameter, thick walls compared to diameter (50% of lumen diameter), lots of smooth muscle -> SNS
Blood characteristics: large drop in pressure (compared to arteries), slower blood velocity
Purpose: controls blood flow (vasoconstriction, vasodilation)
What is the relationship between pressure, blood flow and resistance?
- blood flows down a pressure gradient (high to low)
- but resistance decreases flow
Blood flow = P1 - P2 or
Blood flow = pressure gradient/ resistance
How do you calculate resistance?
resistance = (8Ln) / (pi r^4)
Where, L= length of the vessel, n= viscosity of the fluid, r= radius of the vessel
Describe the structure, blood characteristics and purpose of veins
Capacitance vessels
Structure: large diameter (larger than arteries), very thin walls compared to diameter (10% of lumen diameter), some elastic fibers and smooth muscle -> SNS innervates smooth muscle (can undergo vasoconstriction/dilation), contain valves to prevent backflow
Blood characteristics: very low blood pressure, medium blood velocity
Purpose: “blood reserve” -> 70% of all systemic blood is in our veins, ability to store blood, can increase venous return (maximize) because there is so much
What is the relationship between blood velocity and total cross-sectional area? What is the significance?
- more total cross-sectional area = slower flow
- slower flow = maximize exchange
- capillaries = most cross sectional area because there are so many - this influences blood velocity
- velocity (speed) does not equal flow (total amount)
What are varicose veins?
- backflow of blood, presses on wall, stretches veins
- happens in superficial veins (can see them)
- valve and elastin failures
- can be painful
- genetically predisposed
- obesity and smoking predispose
- not dangerous -> still have deep veins that can return blood
- spider veins are a type of varicose veins, seen in 50% of people
- can have them surgically removed
Why do we need to regulate blood flow?
- to increase blood supply to active tissues and decrease it to inactive tissues
- to maintain blood supply to vital organs - heart and brain at all times
- to maintain blood pressure (MAP)
- to increase or decrease heat loss from the body by redistributing blood
What is Hagen-Poiseuille’s equation?
Blood flow = (pressure gradient* pi* r^4) / (8 L n)
How can you change blood viscosity?
- blood doping: take blood out then add all back right before competition, get more red blood cells - more oxygen (e.g. Lance Armstrong), carry more oxygen to muscle cells - good for sports. Erythropoietin (peptide hormone) acts on bone marrow to increase red blood cell production - blood doping increases erythropoiesis -> increases blood viscosity, increases resistance to flow, heart has to work harder
- dehydration -> decreased plasma volume -> increased viscosity
- body temperature -> higher temp. small decrease in visocisty (body temp highly regulated, don’t see huge changes = small changes in viscosity
Describe vasoconstriction
Increases resistance thus decreases flow
-> decrease radius, decrease bloodflow, increase resistance
Describe vasodilation
Decreases resistance thus increases flow
-> increase radius, increases bloodflow, decreases resistance
What are the mechanisms used to regulate blood flow?
- Local (intrinsic) -> tissue environment (temp, gases, pressure)
- Humoral (extrinsic) -> substances in blood (e.g. hormones, inflammatory mediators, paracrine factors)
- Neural (extrinsic) -> nervous system, autonomic
Describe the local (intrinsic) mechanism used to regulate blood flow
Autoregulatory mechanisms (tissue itself regulates blood flow - no nervous system input)
1. Myogenic derived -> involves smooth muscle stretch (muscle derived)
2. Metabolic derived -> involves matching metabolic needs (metabolic needs of the tissue)
What is the myogenic theory?
Sudden increase in blood pressure -> this stretches walls of arterioles -> triggers opening of stretch-sensitive cation channels -> smooth muscle in arteriole walls contracts (reduce radius) -> decreases blood flow and pressure AFTER constriction
*this protects and maintains normal blood flow