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Cardiovascular System

Key Concepts:

Terms in this set (78)

function of cardiovascular system
pump blood
Transport of substances such as
-O2 & nutrients to cells
- CO2 to the lungs
- wastes from cells to liver and kidneys
- hormones, immune cells, clotting proteins to specific target cells
the cardiovascular system is
A closed system of the heart and blood vessels
- the heart pumps blood
- blood vessels allow blood to circulate to all parts of the body
Blood is used for delivery
the heart
located in thoracic cavity
-the diaphragm separates abdominal cavity from thoracic cavity
- it's the size of fist
-valves present for unidirectional blood flow
-four chambers: 2 atria and 2 ventricles
properties of cardiac muscle
Intercalated disks
- gap junctions: so heart contracts as a unit
-desmosomes: resist stress
Aerobic muscle
No cell division after infancy, growth by hypertrophy
99% contractile cells
1% autorythmic cells
the pericardium
Pericardium is a double-walled
membranous sac surrounding heart
-serous fluid fills the space between the layers of pericardium
-this fluid lubricates heart decreasing friction
-pericarditis = inflammation of pericardium
the heart: 4 chambers
Right and left side act as separate pumps
Septa: separates chambers
-Interventricular septum: separates the
two ventricles
-Interatrial septum: separates the two atria
Four chambers
-atria are receiving chambers
-right atrium
-left atrium
-ventricles are discharging chambers
--right ventricle
--left ventricle
the heart: valves
Four valves
-atrioventricular (AV) valves are between atria and ventricles
bicuspid(mitral) valve (left side of heart)
-tricuspid valve (right side of heart)
-Semilunar valves are between ventricle and artery --pulmonary semilunar valve
--aortic semilunar valve
These valves operate opposite of
one another to force a one-way path of blood through the heart
AV valves
anchored in place by chordae tendineae "heart strings"
- open during heart relaxation and closed during ventricular contraction
SL valves
-closed during heart relaxation but open during ventricular contraction
vasulature
-Arteries are relatively large, branching vessels that conduct blood away from the heart
-Arterioles are small branching vessels with high resistance
- Capillaries are the site of exchange between blood and tissue
-Venules are small converging vessels
-Veins are relatively large converging
vessels that conduct blood to the heart
Closed system
Pressure drives blood flow
blood flow through the cardiovascular system
Parallel flow within the systemic and the
pulmonary circuits
Left ventricle-- aorta--systemic circuit-- venae cavae-- right atrium-- right ventricle-- pulmonary artery-- pulmonary circuit-- pulmonary veins--left atrium--left ventricle
pulmonary circuit
supplied by right heart
blood vessels from heart to lungs and lungs to heart
systemic circuit
supplied by left heart
blood vessels from heart to systemic tissues and tissues to heart
oxygenation of blood
Exchange between blood and tissue takes place in capillaries
pulmonary capillaries
-blood entering lungs is deoxygenated blood
-oxygen diffuses from tissue to blood
-blood leaving lungs is oxygenated blood
systemic capillaries
-blood entering tissues is oxygenated blood
-oxygen diffuses from blood to tissue
-blood leaving tissues is deoxygenated blood
coronary circulation
Blood in the heart chambers does not nourish the
myocardium
The heart has its own nourishing circulatory system consisting of:
- coronary arteries branch from the aorta to supply the heart muscle with O2 blood
-cardiac veins drain the myocardium of blood
-coronary sinus a large vein on the posterior of
the heart, receives blood from cardiac veins
Blood empties into the right atrium via the coronary sinus
differences between blood vessels
Walls of arteries are the thickest
Lumens of veins is largest
Larger veins have valves to prevent backflow
Skeletal pump squeezes blood in veins towards the heart
Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue
tunica intima
inner layer, endothelium
tunica media
-smooth muscle
-controlled by sympathetic nervous system
-radius can be altered
-may by used to control blood flow to individual
capillary beds
-used to regulate mean arterial pressure
tunica externa
mostly fibrous connective tissue
arteries and arterioles
Rapid transport pathway, large diameter. little resistance
Walls contain elastic and fibrous tissue, under high pressure
Smooth muscle regulates radius
systemic arteries
leaves left ventricle
pulmonary arteries
leaves right ventricle
capillaries
Site of exchange between blood and tissue
-Substances exchanged due to concentration gradients
-oxygen and nutrients leave the blood
-Carbon dioxide and other wastes leave the cells
-Walls are 1 cell layer, small diffusion barrier
-10-40 billion per body, total surface area =600m2
-Most cells within 1 mm of a capillary
-Pores between endothelial cells, protein free
plasma moves through pores
capillary exchange: mechanisms
Direct diffusion across plasma membranes
Endocytosis or exocytosis
Some capillaries have gaps (intercellular clefts), plasma membrane not joined by tight junctions
Fenestrations (pores) found on some capillaries
fluid movements at capillary beds
Blood pressure forces fluid and solutes out of capillaries
-osmotic pressure draws fluid into capillaries
Blood pressure is higher than osmotic pressure at the arterial end of the capillary bed
Blood pressure is lower than osmotic pressure at the venous end of the capillary bed
precapillary sphincters
Precapillary sphincters are rings of smooth muscle that surrounds capillaries on the arteriole end
-Contract/relax in response to local factors only
-Contraction
--constrict capillary
--decrease blood flow
-Relaxation
-increase blood flow
-Metabolites (waste products such as CO2) cause relaxation
capillary beds
1.vascular shunts that are vessels that directly connect an arteriole to a venule
2.true capillaries that area
regular exchange vessels
-oxygen and nutrients cross to cells
-carbon dioxide and metabolic waste products
cross into blood
factors affecting filtration and absorption across capillaries
Heart disease--pulmonary edema due to hypertension
Liver disease--decrease in plasma proteins since the liver synthesizes
the majority of these proteins
Kidney disease
--increases blood pressure
--decrease in plasma proteins, they are lost in urine
veins and venules
Veins are a volume reservoir
The anatomy is a factor that influences central
venous pressure and venous return
Large diameter, but thin walls
Valves allow unidirectional blood flow
Skeletal muscle pump generates pressure to
return blood to heart
veins are a volume reservoir because of high compliance
❁Compliance is a measure of how the pressure of a vessel will change with a change in volume
❁Low compliance arteries: small increase in blood volume causes a large increase in pressure
❁High compliance veins: large increase in blood volume required to produce large increase in pressure
❁Veins expand with little change in pressure and function as blood reservoir
❁60% total blood volume in systemic veins at rest, veins hold large volume with small pressure change due to high compliance
skeletal muscle pump
Most arterial blood is pumped by the heart
❁veins use the milking action of muscles to help move blood
- one-way valves in peripheral veins
- skeletal muscle contracts
-squeezes on veins increasing pressure
-blood moves toward heart
- blood cannot move backwards due to valves
-skeletal muscle relaxes
- blood flows into veins between muscles
autorythmic cells
❁The atria contract as a unit and then the ventricles contract as a unit
❁Atrial contraction precedes ventricle contraction
❁Autorhythmicity is the ability to generate own rhythm
❁Autorhythmic cells that provide pathway to spread excitation through the heart
-sinoatrial (SA)node is the pacemaker of the heart
-then the message goes to the atrioventricular (AV) node
❁Wave of contraction through cardiac muscle
conduction system
Special tissue sets the pace
❁ Sinoatrial node = SA node is the pacemaker of the heart, in the right atrium
❁ Atrioventricular node = AV node, is at the junction of the atria and ventricles
❁ Atrioventricular bundle = AV bundle (bundle of His), is in the interventricular septum
❁ Bundle branches are in the interventricular septum
❁ Purkinje fibers spread within the ventricle wall muscles
resting membrane potential
The resting potential is caused by the membrane's ability to maintain a positive charge on its outer surface opposing a negative charge on its inner surface
control of heart beat by pacemakers
❁Autorhythmic cells have pacemaker potentials
❁Spontaneous depolarization caused by closing K+ channels and opening of cation channels
❁Channels that open leading to depolarization:
-- If channels: Na+ moves in, net depolarization, then
-- Ca2+ T channels: further depolarization until threshold
-- Ca2+ L channels cause the action potential
electrical activity in pacemaker cells
❁Depolarize to threshold with funny Na+
channels and T type Ca2+ channels
❁sodium channels can open without a stimulus
❁Open fast L type Ca2+ channels- action potential
❁Repolarization: open VG K+ channels
steps of excitation-contraction coupling
1) Depolarization of cardiac contractile cell to threshold via gap junction
2) Opening of __________channels in plasma membrane
3) Action potential (AP) travels down T tubules
4) Calcium is released from sarcoplasmic reticulum by
- calcium-induced calcium release
- action potentials in T tubules
5) Calcium binds to troponin causing a shift in tropomyosin
6) Binding sites for myosin on actin are exposed
7) Crossbridge cycle occurs
cardiac cycle
❁The cardiac cycle describes the events associated with the flow of blood through the heart during a single complete heartbeat
❁2 main periods of cardiac cycle
-systole: ventricle contraction
-diastole: ventricle relaxation
❁Atria contract simultaneously
❁Atria relax, then ventricles contract
function of cardiac muscle
❁Rhythmic contraction and relaxation generates heart pumping action
❁Contraction pushes blood out of heart into vasculature
❁Relaxation allows heart to fill with blood
ECG
Measures the electrical activity of the heart
❁The P wave corresponds to atrial depolarization
❁The QRS complex corresponds to the
depolarization of the ventricles
❁T wave represents the repolarization of the
ventricles
lub dub
❁Lub sound is atrioventricular valves closing
❁Dub sound is semilunar valves closing
heart contractions
❁Tachycardia is a rapid heart rate over 100 beats
per minute
❁Bradycardia is a slow heart rate less than 60 beats per minutes
heart rate determined by SA node firing rate
❁SA node intrinsic firing rate = 100 beats/min, so with no extrinsic control on heart, HR = 100 beats/min
❁SA node under control of autonomic nervous system & hormones
-rest: parasympathetic dominates, HR = 75 beats per minute
-excitement: sympathetic takes over, HR increases
effects of sympathetic activity on heart rate
Increased sympathetic activity(NE/E from neurons)
--Beta 1 Receptors in SA Node-- Increase open state of If and calcium channels--Increase rate of spontaneous depolarization (increases APs)--Increase heart rate
effects of parasympathetic activity on heart rate
Increased parasympathetic activity (vagus nerve)--Muscarinic cholinergic receptors in SA Node--Increase open state of K+channels and closed state of calcium channels--Decrease rate of spontaneous depolarization & hyperpolarize cell (decreases APs)-- Decrease heart rate
hormonal control of heart rate
❁Epinephrine/norepinephrine have the same effect as sympathetic nervous system input (when released from adrenal gland)
❁Glucagon is a hormone that increases HR
regulation of heart rate
❁What increases heart rate?
- sympathetic nervous system
- hormones
- epinephrine
- thyroxine
- glucagon
-exercise
❁What decreases heart rate?
-parasympathetic nervous system
-decreased venous return
size of the heart
size also determines resting heart rate
physical laws determining blood flow and blood pressure
❁Pressure gradients in the cardiovascular system
❁Resistance in the cardiovascular system
❁Relating pressure gradients and resistance in the systemic circulation
flow rule
❁Circulatory system is a closed system
❁Pressure is the force exerted by blood when heart beats
❁Flow occurs from high pressure to low pressure, highest
near the heart and lowest farthest from the heart
❁R = resistance (diameter of the blood vessel)
❁Systemic vasodilation decrease blood pressure
systemic vasoconstriction increase blood pressure
❁Localized vasodilation increase local blood flow
localized vasoconstriction decrease local blood flow
factors affecting resistance to flow
Radius of vessel: in arterioles (and small arteries) can regulate radius
called vasoconstriction or vasodilation
❁Length of vessel: can't really change this
❁Viscosity of fluid = h, blood viscosity dependent on amount of RBCs and proteins
temperature
heat increases blood flow
cold decreases blood flow
regulating blood flow by regulating radius
❁Regulation of radius of arterioles (and small arteries)
- vasoconstriction decrease radius-- increase resistance
- vasodilation increase radius-- decrease resistance
❁Pulmonary circuit less resistance than systemic, lower pressure gradient required for blood flow
Distribution of Adrenergic Receptors
in Arterioles to Skeletal and Cardiac Muscle
❁Both a and b2 adrenergic receptors for sympathetic response
❁Norepinephrine and epinephrine bind to a1 receptors: vasoconstriction
❁Norepinephrine and epinephrine bind to b2 receptors: vasodilation at b2 receptors
❁Epinephrine has greater affinity for b2 receptors than norepinephrine
pulse
❁Pulse: pressure wave of blood
❁Monitored at pressure points in arteries where pulse is easily palpated
❁Pulse averages 70-76 beats per minute at rest
blood pressure
❁Measurements by health professionals are made on the pressure in large arteries
- systolic is the pressure at the peak of ventricular contraction
- diastolic is the pressure when ventricles relax
- write systolic pressure first and diastolic last
- 120/80 mm Hg
❁Pressure in blood vessels decreases as distance from the heart increases
❁Varies with cardiac cycle and measured with a sphygmomanometer
pressure gradient across systemic circuit
❁Pressure gradient = pressure in aorta minus pressure in venam cava just before it empties into
right atrium
❁Pressure in aorta = mean arterial
pressure (MAP) = 90 mm Hg
❁Pressure in vena cava =central venous pressure (CVP)= 0 mm Hg
❁Pressure gradient =MAP- CVP =90- 0 = 90 mm Hg
blood pressure: effects of factors
❁BP is blood pressure
❁BP is affected by age, weight, time of day, exercise, body position, emotional state
❁CO (cardiac output) is the amount of blood pumped out of the left ventricle per minute
-bigger hearts can pump more blood than smaller hearts
❁PR is peripheral resistance, or the amount of friction blood encounters as it flows through vessels: narrowing of blood vessels and increased blood volume increases PR
❁BP = CO x PR
neural factors
Autonomic nervous system adjustments (sympathetic division)
renal factors
regulation by altering blood volume
renin is released from the kidney to increase BP
effects of factors: temperature
heat has a vasodilating effect
cold has a vasoconstricting effect
chemicals
- various substances can cause increases (naproxen, ibuprofen) or decreases (diuretics)
- alcohol
diet
salt, water intake can alter BP
variations in blood pressure
❁Normal human range is variable
--normal
- Below 120 mmHg systolic
-80 mmHg diastolic
-- hypotension
- low systolic (below 90 mmHg)
- inadequate blood flow to tissues
- often associated with illness
- fainting
--hypertension
-elevated (above 120 mm Hg)
-high systolic (above 130 mm Hg)
-stress on heart and walls of blood vessels
-can be dangerous if it is chronic
neural control of MAP
Negative feedback loop to maintain blood pressure at normal level
❁Detector = baroreceptors are stretch receptors
-- location of baroreceptors: carotid sinus and aortic arch
❁Integration Center = cardiovascular centers
in the brainstem
❁Controllers = autonomic nervous system
❁Effectors = heart and blood vessels
intrinsic control-frank starling's law
Increase venous return--Blood filling the heart, stretches the heart-- Increase strength of
contraction (inotropy)-- Increase stroke volume
long-term regulation of blood pressure
❁Baroreceptor reflex quickly compensates for changes in blood pressure
❁It does not correct the problem
❁Long-term regulation occurs through renal regulation of blood volume
blood volume and blood pressure
Increase blood volume-- increases blood pressure
❁Decrease blood volume-- decreases blood pressure
❁Long-term regulation of blood pressure is through regulation of blood volume (ADH, aldosterone) by the urinary system
cardiac output
❁Cardiac output (CO)
-amount of blood pumped by each side (ventricle) of the heart in one minute
- =SV x HR
❁Stroke volume (SV)
- volume of blood pumped by each ventricle in one contraction (each heartbeat)
- usually remains relatively constant
-about 70 mL of blood is pumped out of the left ventricle with each heartbeat
❁Heart rate (HR) typically ~75 beats per minute
stroke volume (SV)
Volume of blood ejected by the ventricle each beat
Stroke volume = end diastolic blood volume (in the heart) - end systolic blood volume (in the heart) =
130 mL - 60 mL = 70 mL
ejection fraction
Fraction of end-diastolic volume ejected during a
heartbeat
Ejection fraction = stroke volume / end diastolic volume
= 70 mL / 130 mL = 0.54
cardiac output and its control
❁ Autonomic and endocrine input to
the heart
❁ Factors affecting cardiac output:
--changes in heart rate
--changes in stroke volume
❁ Integration of multiple factors affect
cardiac output
independent regulation of blood flow during exercise
❁Cardiac output increases during exercise
❁Distribution of blood does not increase proportionally
-LOCALIZED vasodilation to skeletal muscle and
heart: increases blood flow to these regions
-LOCALIZED vasoconstriction to GI tract and kidneys: decreases blood flow to these regions
Thermoregulatory Responses: Other Cardiovascular Regulatory Processes
❁Thermoregulatory responses (body temperature regulation)
❁Thermoregulation mediated through hypothalamus
❁Thermoregulation takes precedence over baroreceptor reflex
❁Chemoreceptor reflexes (carbon dioxide, pH, and oxygen levels
Developmental Aspects of the Cardiovascular System
❁Aging problems associated with the cardiovascular system include
-venous valves weaken
- varicose veins
- progressive atherosclerosis (plaques/deposits in the inner layer of the arteries)
-- loss of elasticity of vessels leads to hypertension (arteriolosclerosis: thickening of the intima of arterioles)
-- coronary artery disease results from vessels filled with fatty, calcified deposits
heart disease
❁ Caused by reduced blood flow or blockage of coronary artery
❁ Trans fats (aka partially hydrogenated oils)
increase LDL levels
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