Events in the cardiac cycle
-cardiac cycle is the rhythmic pumping action of the heart -one complete contraction (systole) and one complete relaxation (diastole) of all 4 heart chambers
Phases of the cardiac cycle
1. Atrial systole
2. Atrial diastole
3. Ventricular systole (ejection)
4. Ventricular diastole (filling)
Atrial systole
atria depolarize/contract
-P wave appears on ECG
Atrial diastole
-atria repolarize/relax.
-Wave is obscured by QRS complex
Ventricular systole
-ejection
-ventricles depolarize/contract
-QRS complex on ECG
-semilunar valves open
-AV valves close
Ventricular diastole
-filling
-ventricles repolarize/relax
-T wave on ECG
-AV valves are open
-semilunar valves are closed
The cycle
1. ventricle fills
2. isovolumetric contraction
3. ventricular ejection
4. isovolumetric relaxation
5. ventricle fills again
Pulmonary trunk goes from ___ to the _______.
-goes from lung to left atrium
Blood flow through heart
-heart
-arteries
-arterioles
-capillaries
-venules
-veins
** look at #2 on sheet
3 layers of the heart?
1. epicardium (outermost layer)
2. myocardium (middle)
3. endocardium (inner)
Visceral pericardium
-outer layer is parietal and inner is visceral
Visceral pericardium forms epicardium of the heart?
-true
Intrinsic conduction system of heart location
-SA node (Right atrium)
-AV node (inferior interatial septum)
-AV bundle (fibrous skeleton)
-Bundle branches (interventricular septum)
-Purkinje fibers (end of bunble branches throughout the ventricular myocardium)
Intrinsic conduction system of heart pathway:
-impulses from the atria enter the AV node which slows signal.
-delay gives the ventricles time to fill with blood before contraction
-impulse conduction is fastest in the AV bundle, bundle branches, and Purkinje fibers
Which one is the pace maker of the heart and why?
-SA node
-bc it initiates each heartbeat and determines the heart rate
Which sets sinus rhythm?
-75-80
End systolic volume
-the amount of blood left in each ventricle after systole (60mL)
End diastolic volume
-the amount of blood left in each ventricle after diastole (130mL).
- determines how much blood is expelled during systole
SV (stroke volume)
-the volume of blood ejected by one ventricle of the heart in 1 contraction.
-measured in mL
CO- (Cardiac output)
-the amount of blood ejected by each ventricle in 1 minute
Murmur/bruits
-any abnormal heart sound
Frank Starling Law
-stroke volume is proportional to the end diastolic volume
-the more ventricles fill with blood the more they are stretched and the harder they contract on the next beat in order to eject as much blood as received.
-changes in the SV (at rest is 70mL); af
Anastomosis
-a point where two blood vessels merge.
-make alternative way for circulation
-important in reducing heart attacks
Difference between cardiac and skeletal muscle
-page 2 of study guide
**cardiac is autorhythmic
Role of sympathetic system on heart
-postganglionic fibers are adrenergic and release norepinephrine that binds to fibers in the heart
-this speeds up the heart rate and increases the force of contraction.
-increases cardiac output
Role of Parasympathetic system on heart
-parasympathetic vagus nerves have cholinergic, inhibitory effects
-the heart rate slows down and ventricles have more time to fill with blood
-reduces the function of the heart
What are the supports for AV valves?
-these valves are restrained by chordae tendinae, which are in turn attached to papillary muscles
-AV valves tricuspid (right) and bicuspid (left).
What would happen if those supports were severed?
-well it initially prevents back flow so if the supports were severed then back flow would occur.
Structure of the heart: 3 layers?
-Epicardium
-Myocardium
-Endocardium
Epicardium
-external layer
-is visceral pericardium
-Myocardium
-middle layer
-cardiac muscle
-blood vessels
-fibrous skeleton
Endocardium
-internal layer
-simple squamous epithelium
-continuous with endothelia of blood vessels.
Equation of cardiac output and how to calculate SV or HR if 2 values are given.
-Cardiac output= heart rate x stroke volume
Convert L to mL for blood?
mL= 1L/.001
mL= 1 THOUSANDTHS of a Liter.
The waves of a normal EKG (ECG)
-P-Wave
-QRS complex
-T-wave
P-wave
-produced when a signal from the SA node spreads through the atria and depolarize the atria
-depolarize the atria= contraction (systole) of atria
-Repolarization happens during the QRS complex
QRS complex
-produced when the signal from the AV node spreads through the ventricular myocardium and depolarizes the ventricles
-depolarizes the ventricles=contraction (systole) of ventricles
-consists of a small downward deflection (Q), a tall sharp peak (R), and a
T-wave
-generated by ventricular repolarization
-ventricular repolarization= relaxation (diastole) of ventricles
-there is a rounded peak because the ventricles take longer to repolarize than to depolarize.
Factors that change cardiac output and stroke volume
-Preload
-contractility
-afterload
Preload
-amount of tension in the ventricular myocardium immediately before it begins to contract.
-the more tension the more blood ejected; depends on EDV
Contractilty
-refers to how strong the myocardium contracts.
-when contractiliy increases, Stroke volume increases
-when contractiliy decreases, Stroke volume decreases.
Afterload
-the blood pressure in the aorta and pulmonary trunk immediately distal to the semilunar valves, that has to be overcome to open the semilunar valves= resistance to opening the valves
-when afterload increases (hypertension), Stroke volume decreases.
-whe
Characteristics and examples of different types of blood vessels
-Arteries
-capillaries
-veins
Arteries
-carry blood away from the heart
-this blood is oxygenated (O2 rich and CO2 poor) or arterial
-can be elastic or muscular
-arterioles are the smallest arteries.
-pulmonary arteries are an exception
Capillaries
-smallest blood vessels for capillary exchange
-3 MAIN types: continuous, fenestrated, sinusoids
Veins
-carry blood toward the heart
-also known as venous return
-blood is DEoxygenated (CO2 rich and O2 poor) or venous
-pulmonary veins are an exception
What are the smallest veins
-venules
Capillaries: Continuous
-occurs in most tissues
-endothelial cells have tight junctions with intercellular clefts that form a continuous tube
-blood solutes will pass through endothelial cells or intercellular clefts.
Capillaries: Fenestrated
-have endothelial cells ridded with holes called fenestrations
-are important in organs that engage in rapid absorption or filtration such as kidneys
Capillaries: Sinusoids
-irregular blood-filled spaces in the liver, bone marrows, spleen and other organs
-fewer tight junctions
Heart sounds: 2 types
-S1
-S2
Heart Sound: S1
-the first heart sound comes from the closure of AV valves
-louder and longer
Heart sounds: S2
-the second heart sound comes from the closure of semilunar valves
-softer and sharper
Heart sounds are produced by?
-valve closure
Function of Heart Valves
-valves ensure a 1 way flow of blood through the heart
-prevent backflow of blood
-only can go atrium to ventricle
AV valves
-regulate the opening between the atria and ventricles
-attached with chordae tendina to papillary muscles to prevent valvular prolapse and blood backflow
Right AV valve
-tricuspid
-seperates RA from RV
Left AV valves
-bicuspid
-mitral
-separates LA from LV
Semilunar valve
-regulate blood flow from the ventricles into the arteries
pulmonary semilunar valve
-controls opening from right ventricle into the pulmonary trunk
Aortic semilunar valve
-controls the opening from the left ventricle into the aorta
Factors that influence blood flow?
-vicosity
-vessel length
-vessel radius
-vasoconstriction
-vasodilation
viscosity
-thickness of blood
-determined by proteins and red blood cells
vessel length
-pressure and flow decline with distance
vessel radius
-how wide the blood vessels are (most adjustable variable)
vasoconstriction
-the narrowing of a vessel
vasodilation
-the widening of a vessel
Mechanism of capillary filtration and reabsorption
-do worksheet (fill in blank paragraph)
mechanism of capillary filtration
-occurs at arterial end; due to high hydrostatic pressure
Mechanism of capillary reabsorption
-occurs at venous end; due to high oncotic pressure
Oncotic pressure
-negative pressure
-suction pressure
-draws fluid
Neural (BAROREFLEX) Control of Blood Pressure
-central and autonomic nervous systems control BP
-baroreflex
-chemoreflex
-medullary ischemic reflex
Baroreflex
-negative feedback response
Chemoreflex
-autonomic response to changes in blood chemistry
Medullary ischemic reflex
-medulla oblongata monitors its own blood supply and activates corrective reflexes when it senses insufficient perfusion
Hormonal control of Blood Pressure
-use of hormones to change BP through vasoactive effects or regulating water balance
-atrial natriuretic factor
-ADH
-Epinephrine & Norephinephrine
Atrial natriuretic factor
-high urinary sodium excretion and causes generalized vasodilation
-*
decreases BP!!
*
ADH
-causes vasoconstriction and reduces urine output
-increases BP
Epinephrine and Norepinephrine
-causes vasoconstriction in most blood vessels
-inceases BP
What is edema
-an abnormal increase in interstitial fluid volume that can result from:
-- increases capillary filtration
--decreased capillary reabsorption
--obstructed lymphatic drainage
Characteristics of veins
-thin walls
-low BP
-colapse when empty
-venules are the smallest
-expand easily
-blood vessels that carry blood toward either atrium of the heart
-capacitance vessels
-most vessels in the extremities have valves
Layers of blood vessel wall
-Tunica externa adventita
-Tunica media
-Tunica interna
*
know chart
*
Tunica externa adventita
-protects
-reinforces
-anchors
Tunica media
-essential in regulating hemodynamics
Tunica interna
-repels platelets and decreases friction
Tachycardia
-persistant, resting adult heart rate above 100 bpm.
-caused by stress, anxiety, drugs, heart disease or fever
-sympathetic control
Bradycardia
-persistant, resting adult heart rate below 60 bpm.
-common during sleep and in endurance trained athletes
-parasympathetic control
which artery is used to measure blood pressure?
-the brachial artery in the arm
Which artery is used to measure pulse?
-radial artery
Most common route of blood flow?
heart-->arteries-->arterioles-->capillaries-->venules-->veins
What is dextrocardia
-the heart is reversed and is in the right side of the chest
-a true anatomic reversal
-can be part of situs inversus
-anatomical reversal of heart
Sinus Rhythm
-is set by SA node
-70-80bpm
-influenced by temperature and drugs