Exam 2: Heart
Systole
Contraction of the heart ESV-end systolic volume contractility/afterload
Define ventricular diastole and ventricular systole. Which event lasts longer? Why?
Diastole is relaxation and fills heart with blood, lasts longer because of the time for atrial contraction, blood fill, creates ability to modulate diastole to increase HR, let cardiac muscle rest. Diastole allows for blood flow through coronary arteries for nourishment. Systole is contraction, eject blood.
What are the three factors of stroke volume? Explain each one.
EDV, and ESV EDV-preload=degree of stretch ESV: contractility and after-load (inverse) Contractility-contractile strength at a given length Afterload: pressure overcome to eject blood
What are the types of arterial vessels?
In 'branching into' order: Elastic made of a thick walled layer near heart, large lumen, lots of elastin. They serve as pressure reservoirs that reduce fluctuations between contractions from diastole to systole, and maintain pressure gradient. Muscular-smooth muscle Arterioles-smooth muscle, site of regulation
What are the types of capillaries?
In order of least leaky pores to most leaky pores: Continuous- endothelium connected together, tight junctions bw cells (skins, muscles, lungs), most common, basement membrane, Fenestrated- flow of fluids and solutes (Kidneys,SI), increase permeability, basement membrane Sinusoids-free exchange (liver, spleen), incomplete basement membrane
Diastole
Relaxation of the heart EDV-end diastolic volume
Describe the structures that contribute to the propagation of electrical potential through the heart.
SA node generates impulses -> AV node via internodal pathways. Impulse briefly pauses -> AV bundle electrically connects atria to ventricles -> L/R Bundle branches conduct impulses through the interventricular septum-> Subendocardial connecting network depolarizes the contractile cells of both ventricles.
What is the most important blood vessel in maintaining blood pressure within the cardiovascular system? Describe its functionality.
The arterial pressure of the arterial vessel containing the elastic artery contributes the most to the pressure gradient in the cardiovascular system. The arterial blood pressure is affected by the ability of the elastic arteries to stretch when forced with volume of blood. The systolic pressure is 120 mmHg and diastolic pressure is 80 mmHg. The mean diastolic pressure is proportionate to cardiac output and resistance and is equivalent to diastolic + 1/3 (systolic-diastolic). AEB declines as blood moves further from heart and it looses pulsatile nature in less elastic vessels.
How does blood flow through the cardiovascular system?
The cardiovascular system is made up of the heart+blood vessels+blood. The blood flows through this system by its hydrostatic pressure, from a high to low pressure gradient created by the heart. BP increases in arteries during ventricle systole and decreases during diastole.
Synctium
The individual cells of the myocardium that collectively function so that the heart contracts as a unit
What are the inotropic factors of contractility?
The positive inotropic factors are: sympathetic activity, Ca2+, norepinephrine/epinephrine, and glucagon. The negative inotropic factors are: excess H+ and K+, and calcium channel blockers
Cardiovascular system is closed, so how does blood move?
Through the contractions caused by the increased pressures of the fluid within the system. When ventricles contract, they drive blood out and push the blood in front of them creating a driving pressure, which causes a change in vessel walls that affects pressure.
Stroke Volume (SV)
amount of blood pumped by one ventricle during a contraction end diastolic volume (EDV) - end systolic volume (ESV) relaxation volume- contraction volume preload- contractility/afterload
How do you speed up heart rate?
block parasympathetic branch and increase sympathetic input
systemic capillaries
capillaries in all the body tissues where gas exchange occurs internally (internal respiration)
hydrostatic pressure
fluid is not moving, force is exerted equally in all directions
blood pressure
hydrostatic pressure exerted by blood on vessel walls or (heart chambers)
filibritation
myocardial cells contracting in a disorganized manner
inferior ventricles
pumps blood into circulation (left)
superior atria
receives blood from circulation (right)
pulmonary circuit
transports blood to and from the lungs where it picks up oxygen and delivers carbon dioxide for exhalation
systemic circuit
transports oxygenated blood to all of the tissues of the body and returns deoxygenated blood and carbon dioxide to the heart to be sent back to the pulmonary circulation
What are the factors that contribute to cardiac output? How do changes in these factors occur and how do they influence cardiac output?
An increase in sympathetic activity and skeletal muscle with a decrease in heart rate increases venous rate which increases EDV(preload). Positive inotropic factors: Bloodborne, epinephrine, thyroxine, excess Cterm-21a2+, glucagon increases contractility and decreases ESV (afterload). The increase in EDV and the decrease in ESV increases the Stroke Volume. Exercise, fright, and anxiety increases sympathetic activity and increases contractility and decreases parasympathetic activity. Combined these increase heart rate. An increase in stroke volume and an increase in heart rate increases cardiac output.
Compare and contrast the blood vessels
Arteries, veins and capillaries have a lumen surrounded by the endothelial cells of the tunica intima. Arteries and veins are also surrounded by smooth muscles/elastic of the tunica media and the blood vessels/nerves. of the tunica externa. Arteries have a thicker wall, more smooth muscle, smaller lumen diameter, and higher pressure fluid then veins. Veins are a convergence of venules, can contain one-way valves, and distribute 64% of blood. Capillaries connect arteries to veins, tunica intima layer, small lumen, and site of exchange bw blood and interstitial fluid.
Compare that vessel-pressure relationship with the rest of the vessels.
AEB super important in maintaining the blood pressure within the cardiovascular system due to its elastic nature. Capillary Blood Pressure is very low in pressure and would erupt if there was high pressure. There is enough pressure to push fluid into surrounding tissue. Venous blood pressure lose pulsatile flow, very low pressures and adapts to increase flow. It has valves (muscular pump, respiratory pump), sympathetic venoconstriction, and a large lumen.
List and describe the structures or mechanism that facilitate venous return
Adaptions to increase flow through the venous blood vessel with low pressure: Valves- skeletal muscle (pump), respiratory (pump), large lumens of veins (less resistance), venoconstriction. Venous return (VR) is the flow of blood back to the heart. Under steady-state conditions, venous return must equal cardiac output (CO) when averaged over time because the cardiovascular system is essentially a closed loop (see figure). Otherwise, blood would accumulate in either the systemic or pulmonary circulations.
Trace the path of a red blood cell through a complete round of circulation, starting and ending in the left atrium.
Left atrium -> left ventricle via bicuspid/L AV valve-> aorta via aortic semilunar valve -> body (elastic arteries, muscular arteries, arterioles, capillaries, venules, veins) -> vena cavae -> -> right atrium -> right ventricle via triscuspid/R AV -> pulmonary trunk via pulmonary SL valves -> lungs (pulmonary arteries, arterioles, pulmonary capillaries -> pulmonary venules) -> pulmonary veins -> left atrium Heart has 2 pumps acting in coordinated manner (atrium and ventricle)
What is the relationship between the cellular and organ level electrical events in the heart?
The cellular and organ level electrical events in the heart are responsible for the heart beat. Electrical APs in pacemaker cells located in the SA node, AV node, AV bundle, left/right bundle branches, purkinjie fibers and APs in contractile cell in the cardiac muscle causing a synchronized contraction. The heart decreases its volume (systole), increases in its pressure and blood moves away.
What is the relationship between electrical and mechanical events in the heart?
The electrical and mechanical events in the heart act together in the heartbeat as the cardiac cycle. 1. P wave: atrial depolarization 2.PQ segment: atrial systole/contraction, impulse delay at the AV node 3.QRS complex: ventricular depolarization 4..ST segment: ventricular contraction 5. T wave: ventricular repolarization 6.T-P segment: ventricular repolarization
What are the factors that influence blood flow through the cardiovascular system? How are these factors modified to maintain homeostasis?
The factors that influence the flow are pressure, volume and resistance. Blood flow is equal to net pressure change/resistance in the cardiovascular system Resistance of the blood vessels decreases flow: If length increases r increases If viscosity increases r increases decreases If radius increases Pressure gradient caused by heart increases flow: blood moves only if there is a + pressure pressure gradient. These factors are modified to maintain homeostasis by ensuring that a pressure gradient is created by through the contractions of the heart.
What are the different types of blood vessels and their specific functions?
There are there different types of blood vessels: Arteries that branch and decrease in diameter as they take blood away from heart to capillaries. Veins that converge and increase in diameter as they bring blood to the heart from the capillaries. Capillaries the site of blood/tissue exchange
Compare and contrast sympathetic and parasympathetic innervation of the heart and the mechanism of HR modulation.
Parasympathetic targets the AV node and SA node via vagus nerve. ACh binding on muscarinic receptors activate G proteins -> Activates G protein -> K+ channels open and hyperpolarize membranes -> Resting membrane potential decreases, takes longer to reach threshold -> Heart rate decreases Sympathetic targets AV node, SA node, cardiac muscle, coronary arteries via cardiac nerve. NE binding on B1 adrenergic receptors activates G proteins -> Activates adenylate cyclase -> Adenylate cyclase turns ATP to cAMP -> Ca2+ channels open and depolarizes membranes -> Resting membrane potential increases, reaches threshold faster -> Heart rate increases. Sympathetic also innervates adrenal medulla to cause NE release. Parasympathetic only modulates pacemakers. Sympathetic modulates pacemakers and factors that affect contractility and venous return.
Trace the pathway of oxygenated and deoxygenated blood through the chambers of the heart
Blood moves the heart using two pumps simultaneously: the systemic circuit and the pulmonary circuit. Oxygen rich blood is delivered to the body tissues via the systemic circuit, systemic capillaries Oxygen-poor blood returns from the body tissues back to the heart. The blood goes through the IVC and SVC through the coronary sinus. The blood goes into the right atrium through the tricuspid valve into the right ventricle through the pulmonary semilunar valve into the pulmonary trunk. The oxygen-poor blood is carried in two pulmonary arteries to the lungs via the pulmonary circuit to be oxygenated. The blood goes through the pulmonary capillaries where it is oxygenated. The oxygen rich blood returns to the heart via the four pulmonary veins. It then moves into the left atrium through the mitral valve into the left ventricle through the aortic semilunar valve into the aorta. The oxygen rich blood enters the systemic circuit and repeats the cycle.
