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A&P Ch.8: Cardiovascular System


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What are the three different blood vessels?
What do capillaries do?
-connect smallest veins to smalles arteries.
What are the two circuits of cardiovascular system?
What is the fibrous pericardium?
-the part of pericardium that fuses with diaphragm
What is the serous pericardium?
Double layer around heart providing protection against friction
-outer parietal layer
-inner visceral layer (around heart)
-pericardial space between, filled with pericardial fluid
What are the three layers of the heart?
-epicardium (outer: visceral pericardium. Consists of mesothelium and an underlying layer of loose connective tissue)
-myocardium (thick contractile layer, consists of concentric layers of cardiac muscle tissues, blood vessels and nerves)
-endocardium (continuous with endothelium, delicate inner layer of membranous tissue)
What are intercalacted discs?
-interconnect cardiac muscle cells
-secured by desmosomes
-linked by gap junctions
-convery force of contraction
-propagate action potentials
Describe fetal blood circulation.
-foramen ovale allows blood to flow freely from right to left atrium (closes at birth)
-ductus arteriosus short-circutis the pulmonary trunk (constricts at birth)
What is the fibrous skeleton?
-consists of four dnese bands of tough, elastic tissue that encircle the bases of the pulmonary trunk and aorta and the heart valves
What wraps each cardiac muscle cell?
-A strong but elastic sheath
-connected to adjacent cells by fibrous cross-links
What is coronary circulation?
-meets high ocygen and nutrient demands of cardiac muscle cells (coronary arteries and cardiac veins).
What are coronary arteries?
-originate at base of ascending aorta with highest blood pressure
What are cardiac veins?
-blood exits these into the coronary sinus to drain into the right atrium
What are the five classes of blood vessels?
Besides attaching veins and arteries, what do capillaries do?
-smallest blood vessels
-location of exchange between blood and interstitial fluid
What are the three layers of the arteries and veins?
-tunica adventitia (externa)
-tunica media
-tunica interna (intima)
Why can't diffusion occur in arteries and veins?
Walls are too thick.
Describe the tunica adeventitia.
-outermost layer of veins and arteries
-strong, flexible fibrous connective tissue (collagen and elastic fibers)
Describe the tunica media.
-middle layer of arteries and veins
-contains concentric sheets of smooth muscle in loose connective tissue
Describe the tunica interna
-innermost layer of veins and arteries
-includes sendothelial lining and connective tissue layer
See page 7 for difference between arteries and veins.
Features, typical artery, typical vein.
What are the different size/structures of blood vessels?
-elastic, muscular, arterioles
-large, medium, venules
What is the function of capillaries?
-lacation of all echange functions of cardivasuclar system
-materials diffuse between blood and interstitial fluid
Describe the capillary structure.
-endothelial tube, inside thin basal lamina
-no tunica media
-no tunica externa
-diameter similar to red blood cell
What are the two types of capillaries?
Describe continuous capillaries.
-have complete endothelial lining
-found in all tissues except epithelia nad cartilage
-permit diffusion of water, small solutes, and lipid-soluble materials.
Describe fenestrated capillaries.
-have pores in endothelial lining
-found in choroid plexus, endocrine organs, kidneys, intestinal tract
-permits rapid exvhange of water and larger solutes between plasma and interstitial fluid
What are sinusoids?
-have gaps between adjacent endothelial vells
-permit free exchange of water and large plasma proteins between blood and interstitial fluid
-located in liver, spleen, bone marrow, and endocrine organs.
What are some capillary networks?
-arteriovenous anastomoses
-vapillary sphincter
What is arteriovenous anastomoses?
-direct connections between arterioles and venules
-bypass the capillary bed
What is capillary sphincter?
-Guards entrance to each capillary
-Opens and closes, causing capillary blood to flow in pulses
What is vasomotion?
-contraction and relaxation cycle of capillary sphincters
-causes blood flow in capillary beds to constantly change routes
What pushes blood toward heart in veins?
Since pressure is reduced the further blood is from heart, compression serves as movement of blood.
What prevents blood from passing back into capillaries once in the venules?
What do venules do?
-collect blood from the capillaries and merge into medium-sized veins and then large veins.
Where is the majority of blood located?
In the veins (60-65%).
*1/3 of venous blood is in liver, bone marrow, and skin as a venous reserve.
How much blood is in heart, arteries, and capillaries?
-30-35% of blood volume
What is a heartbeat?
-a single contraction of the heart which occurs in series
What are the series that occur in a heartbeat?
-first the atria
-then the ventricles
*must be coordinated so blood flows in right direction at proper time
What are two types of cardiac muscle cells and what do they control?
-conducting system: controls and coordinates heartbeat
-contractile cells: produce contractions
Where is the sinoatrial node located and what is its purpose?
-In the wall of the right atrium. This node depolarizes first, establishing a heartrate.
Where is the atrioventricular node located and what is its purpose?
-At junction between atria and ventricles
-not sure what it is for yet
What are conducting cells for?
-interconnect the two nodes and distribute the contractile stimulus throughout the myocardium (uses internodal pathways, AV bundles, bundle branches, purkinje fibers)
What is prepotential?
AKA pacemaker potential
-resting potential of conducting cells which gradually depolarize toward threshold.
What is the conducting system?
-Action potential transmitted through conducting system to SA node
-produces action potentials in cardiac muscle cells (contractile cells)
-occurs with automaticity
-its has three parts: SA node, AV node, and cunducting cells.
How many action potentials per minute does the SA node generate?
AV node?
-80 to 100
-40 to 60
What does parasympathetic stimulation do to the heart?
Slows heart rate down
How long does it take for AV node to pass its impulse into AV bundles?
100 msec
What are contractile cells?
How is the stimulus moved from atria to ventricle?
-form bulk of atrial and ventricular walls
-produce powerful contractions that propel blood
-99% of muscle cells in the heart
*purkinje fibers distribute the stimulus to the contractile cells in ventricles
Describe steps 1 of 5 of impulse conduction throughout heart.
SA node activity and atrial activation begin
Time= 0 mseconds
Describe steps 2 of 5 of impulse conduction throughout heart.
Stimulation spreads across the atrial surfaces reaching the AV node
Time= 50 msec
Describe steps 3 of 5 of impulse conduction throughout heart.
100 msec delay at AV node. Atrial contraction begins
Time= 150 msec
Describe steps 4 of 5 of impulse conduction throughout heart.
The impulse travels along the interventricular septum within the AV bundles and these branch to the Purkinje fibers, and through the moderator band, to the papillary muscles of the right ventricle.
Time= 175 msec
Describe steps 5 of 5 of impulse conduction throughout heart.
The impulse is distributed by Purkinje fibers and relayed throughout the ventricular myocardium. Atrial contraction completed and ventricular contraction begins.
Time= 225 msec.
What are the four parts of action potentials in contractile cells?
-step 1
-step 2
-step 3
-refractory period
What occurs in step 1 of contractile cell action potentials?
Rapid depolarization:
-voltage-regulated sodium channels open quickly
What occurs in step 2 of contractile cell action potentials?
The Plateau:
-valtage-regulated calcium channels slowly open
-pressence of a plateau is the MAJOR difference between cardiac and skeletal action potentials
What occurs in step 3 of contractile cell action potentials?
-slowly, potassium channels open
What occurs in last part of contractile cell action potentials?
Refractory period: long with no tetanic contrations
What is an electrocardiogram?
-a recording of electrical events in the heart
-obtained by electrodes at apecific body locations
-abnormal patterns diagnose damage
What are the important landmarks of an ECG?
-P wave
-QRS comples
-T wave
What happens in the P wave?
-atria depolarizes
What happens in the QRS wave?
-ventricle depolarizes
What happens in the T wave?
-ventricle repolarizes
What is the definition of the cardiac cycle?
The period between the start of 1 heartbeat and the beginning of the next (4 phases).
-atrial systole
-atrial diastole
-ventricular systole
-ventricular diastole
What are the six steps in the cardiac cycle?
-atrial systole
-atrial systole ends
-ventricular systole
-ventricular ejection
-ventricular diastole
-atrial pressure higher than ventricular pressure
What happens in atrial systole?
-atrial contraction begins
-right and left AV valves are open
-atria eject blood into ventricles
-filling of ventricles
What happens in atrial systole ends?
-ventricles contain maximum volume
-atrial diastole begins
What happens in ventricular systole?
-pressure in ventricles rise
-AV valves shut
-isovolumetric ventricular contration
What happens in ventricular ejection?
-semilumar valves open
-blood flows into pulonary and aortic trunks
What happens in ventricular diastole?
-ventricular pressure falls
-semilunar valves close
-ventricular pressure is high than atrial pressure
-all valves closed
-ventricles relax (isovolumetric relaxation)
What happens during atrial pressure is higher than ventricular pressure?
-AV valves open
-passive atrial filling
-passive ventricular filling
-cardiac cycle ends
What are the different heart sounds?
S1: loud, produced by AV valves
S2: loud, produced by semilunar valves
S3, S4: quiet, produced by atrial contraction and filling of ventricles
What is cardiodynamics?
The movement and force generated by cardiac contractions
What are some important cardiodynamic terms?
End-diastole volume (EDV)
End-systoic volume (ESV)
Stroke volume (SV)
Ejection faction.
What is EDV?
-the amount of blood in each ventricle at the end of ventricular diastole
What is ESV?
-the amount of blood remaining in each ventricle at the end of ventricular systole
What is SV?
-the amount of blood pumped out of each ventricle during a single beat, SV=EDV-ESV
What is ejection fraction?
-the percentage of the EDV represented by the SV: SV/EDV x 100
What is cardiac output (CO)?
-the amount of blood pumped by each ventricle in one minute
- CO=SV x HR
CO: ml/min
SV: ml/beat
HR: beats/min
How can cardiac output be controlled?
Changes in either stroke volume or heart rate:
-heart rate: adjusted by autonomic nercous system or hormone
-stroke volume: adjusted by changing EDV or ESV
What factors affect the heart rate?
-cardioacceleratory center
-cardioinhibitory center
-epinephrine, norepinephrine, thyroid hormones increase heart rate
What are the cardioacceleratory and cardioinhibitory centers part of?
-medulla oblongata
What does the cardioacceleratory center do?
Controls sympathetic neurons
-increase heart rate
-produce more powerful contractions (reduce ESV)
What does the cardioinhibitory center do?
Controls parasympathetic neurons
-slows heart rate
-reduces contractile strength (reduce the ESV)
What is circulatory pressure and it's three components?
-The pressure difference between the base of the ascending aorta and the entrance to the right atrium
-blood pressure, capillary pressure, venous pressure.
What is blood pressure?
-refers to arterial pressure. In humans, ranges from an average of 100mm Hg to 35 mm Hg at start of capillary network
What is capillary hydrostatic pressure?
-pressure within capillary beds, range from 35-18 mm Hg
What is venous pressure?
-the pressure withing the venous system, about 18 mm Hg
What is normal atmospheric pressure?
760 mm Hg
What is total peripheral distance?
-resistance of the entire cardiovascular system that opposes the movement of blood.
-peripheral resistance (PR) referred to as resistance to arterial system.
*There is very little resistance in venous system
What is the connection between PR and blood flow rate?
The higher the PR, the lower the rate of blood flow.
-flow is directly proportional tothe pressure gradient and inversely proportional to resistance
What are three sources of peripheral resistance?
-vascular resistance
What is vascular resistance?
-most important: friction between blood and walls
-friction depends on length and diameter of vessels
*diameter of arterioles most important determinant of PR
How can diameter and length change in a body?
-adult vessel length is constant
-vessel diameter varies by vasodilation and vasoconstriction
-R increases exponentially as vessel diameter decreases
What is viscosity?
-whole blood viscosity about 5 times more than water
-should be stable under normal conditions
What is blood turbulence?
-the phenomenon that high flow rates, irregular surfaces, and sudden changes in vessel diameter upset the smooth flow of blood, creating eddies and swirls.
What does arterial blood pressure change?
-it rises during ventricular systole
-falls during ventricular diastole
-as distance from heart increases, pulse becomes weaker and arterial pressure decreases
What is systolic pressure?
-the preak blood pressure measured during ventricular sytole
What is diastolic pressure?
-the minimum blood pressure during diastole
What is pulse pressure?
-the difference between these two blood pressures
What is mean arterial pressure (MAP)?
diastolic pressure + (pulse pressure/3)
What is capillary exchange?
What determines water movement?
-processes that move materials across typical capillary walls (filtration, diffusion, reabsorption)
-direction of water movement is determined by the balance between the hydrostatic pressure and osmotic pressure
What three things move blood through veins towards the heart?
-muscular compression
-respiratory pump
How does diffusion work in capillary exchange?
-driving by concentration gradient
How does filtration work in capillary exchange?
-driving by hydrostatic pressure
How does reabsorption work in capillary exchange?
-driving by osmotic pressure
What is the respiratory pump?
a mechanism by which changes in the pressures of teh thoracic cavity during the respiratory cyle assist the venous return to the heart
What are some ways of cardiovascular regulation?
-central neural mechanisms
What is autoregulation?
Local factors change the pattern of blood flow within capillary beds in response to chemical changes in interstitial fluids
What is central neural mechanisms?
Respond to changes in arterial pressure or blood gas level
What part to hormones play in cardiovascular regulation?
-assist in short-term adjustments (changes in cardiac output and peripheral resistance)
-long term adjustments (changes in blood volume that affect cardiac output and gas transport)
How is peripheral resistance adjusted?
-adjusted at tissues by local factors (vasodilation) that result in the dilation or constriction of precapillary sphincters.
What are local vasodilators?
-decreased tissue oxygen, or increased CO2 levels
-the generation of lactic acids or other acids by tissue cells, which lower local pH
-the release of nitric oxide
-rising conc. of K ions or H ions in interstitial fluid
-Chemicals released during local inflammation, including histamine and NO
-elevated local temperature
What are the cardiovascular centers in the medulla oblongata?
-cardiac centers (cardioacceleratory and cardioinhibitory centers)
-vasomotor centers
*both centers indistinguishable anatomically
What do vasomotor centers do?
-control the activity of sympathetic motor neurons
-control vasoconstriction of peripheral vessels in most tissues and vasodilation in skeletal muscles and brain
What are baroreceptors?
-in aortic sinuses, the carotid sinuses, and the right atrium
-autonomic reflexes that adjust cardiac output and peripheral resistance to maintain normal arterial pressures.
What are chemoreceptors and how do they work?
-sensory neurons located in the carotid bodies, situated in the neck near the carotid sinus, and the aortic bodies, near the arch of the aorta
-respond to changes in the oxygen oxygen or CO2 levels in the blood and cerebrospinal fluid

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