Module 5 Cardiovascular anatomy and physiology Flashcards
What is the Pericardium
Double walled sac surrounding the heart
List the layers of the pericardium 3
- Fibrous Pericardium - tough, loose fitting inextensible sac. surrounding heart
- Serous Pericardium - 2 layers
- Parietal layer (inside fibrous pericardium)
- visceral layer (epicardium) - integral part of heart wall.
- A pericardial Space with pericardial fluid separates the two layers, -this provides protection from friction
How much does the heart weigh?
250-300 grams
List and describe the three distinct layers of the heart
- Epicardium - Outer layer of heart wall
- Myocardium - Thickest, contractile middle layer, compresses heart cavities
- Endocardium - delicate inner layer of endothelial tissue
Note what is between the visceral and parietal layers of the heart?
Fluid
Describe the Atria, function and structure
- Two superior chanbers - receiving chambers because they receive blood from the veins
- They alternately contract and relax to receive blood, then push it into the ventricles
- Myocardial wall of atrium not that thick, they don’t need to exert much pressure, not moving blood very far.
- Auricle - earlike flap protruding from each atrium
Describe the Ventricles, form and function 3
- Two lower chambers, pumping chambers
- Ventricular myocardium thicker than Atrial
- Myocardium on L is thicker than on R
Look at the figure of the chamber and valves of the heart
Patton
List the heart valves and describe what they do.
- Atrioventricular (AV) valves: prevent blood from flowing back into atria
- Tricuspid valve - (Right AV valve): guards the R atrioventricular orifice; free edges of three flaps of endocardium are attached to papillary muscles by chordae tendineae
- Bicuspid or Mitral valve (left AV valve): similar to structure of tricuspid valve except has only two flaps
- Semilunar valves: half moon shaped flaps growing out from the lining of the pulmonary artery and aorta;
- Prevent blood from flowing back into the ventricles from the aorta and pulmonary artery
- Pulmonary valve: valve at enterance of the pulmonary artery
- Aortic Valve: valve at enterance of the aorta
What is the direction of blood flow through the heart?
Where does the heart receive its blood from?
- right and left coronary arteries, the first branches to come from the aorta
- Ventricles receive blood from both the right and left coronary arteries
- Most abundant blood supply goes to the myorcardium of the L ventricle
- Few anastomoses exist between the larger branches of the coronary arteries ( making it really bad if one is blocked)
Names of Coronary arteries (both names) And where they are located, as well as what parts of the heart they feed
- Anterior interventricular artery (Left anterior descending artery)
- Posterior interventricular artery ( posterior descending artery? or Right Posterior decsending artery?)
- Right marginal artery
- Right coronary artery
- Left coronary artery
- Circumflex artery
what routes do the Coronary Veins follow, where does the blood go after it flows through the coronary veins
- follow a course that parallels that of the coronary arteries
- after going through cardiac veins, blood enters the coronary sinus to drain into the right atrium.
What are the cardiac plexuses?
- They are part of the conduction system of the heart, and are locatedthe** near the arch of the aorta**
- They are composed of sympathetic and parasympathetic fibers
- Fibers from the cardiac plexus accompany the right and left coronary arteries to enter the heart
- Most of these fibers end in the SA node, but some end in the AV node, and in the atrial myocardium; the nodes are the hearts pacemakers
- Sympathetic nerves: Accelerator nerves
- Vagus fibers: inhibitory, or depressor, nerves
SA node (pacemaker) What does it do, what is it composed of?
- initiates each heartbeat and sets its pace
- Specialized pacemaker cells in the node possess an intrinsic rhythm (automaticity)
What is the difference between ordinary cardiac muscle tissue and the conduction system structures within the muscle?
- The conduction system fibers are more highly specialized and permit only rapid conduction of an Action Potential through the heart.
See diagram of the conduction system of the heart on paper.
in my notes.
Where do the coronary arteries branch off from?
They branch off from the aorta directly above the semilunar valve.
Angina Pectoris
characteristic pain felt beneath the sternum and in the left arm and neck when the coronary artery is occluded ( blocked )
In anatomical terms, where is the heart located?
- Mediastinum, or middle region of the Thorax, just behind the body of the sternum between the points of attachment of the second through sixth ribs.
- Posteriorly it rests against the bodies of the 5th to 8th vertebrae
- Lower border, or apex, rests on the diaphragm
- upper border - base, lies just below the second rib.
When does the heart reach its adult size and weight?
Between puberty and 25 years old
List the direction of blood flow through the heart. 14
- Right atrium ⇒2. Right atrioventricular (tricuspid) valve⇒3. Right ventriicle⇒pulmonary semilunar valve⇒4. pulmonary trunk, first portion of pulmonary artery⇒5. left and right pulmonary arteries⇒6. gas exchange tissue of the lungs⇒7. pulmonary veins⇒8. left atrium⇒9. left atrioventricular (mitral) valve⇒10. left ventricle⇒11. aortic semilunar valve⇒12. Aorta⇒branches of the aorta supply all the tissues of the body except the gas-exchange tissues of the lungs. ⇒13. Blood from the head, neck and upper extremities empties into the superior Vena Cava, blood from the lower body empties into the inferior vena cava. ⇒14. both these large vessels empty blood into the right atrium, and the cycle starts over again.
How do atrioventricular valves differ from semilunar valves?
- AV valves prevent blood flow from flowing back up into the atria from the ventricles,
- semilunar valves prevent it from flowing back down into the ventricles from the aorta and pulmonary trunk.
List the way blood flows through the heart
Look at figure 21-11 in patton
What is the reason that the Coronary arteries are placed behind the flaps of the aortic valve?
blood flow is diverted from these openings during ventricular contraction when valve leaflets are against the wall of the aorta. During ventricular relaxation, when the coronary arteries expand, blood flow is diverted into the coronary artery openings by the closing of the aortic valve, allowing the aortic arteries to fill.
Backflow of blood closes valve and the coronary arteries fill, see figure 21-10 in patton
Coronary Sinus
Common venous channel on the right atrium
What does it mean that the myocardium is Autorhythmic?
- Heart muscle can produce it’s own action potentials without the influence of afferent nerve signals.
- To coordinate effective self activation, the heart has a system of myocardial fibers specialized for rapid electrical conduction along a pathway extending from the top to the bottom of the heart
- This is called the conduction system of the heart
How does the heart adjust rate to the body needs?
- In addition to it’s own conduction system, the heart recieves efferent motor nervesThat permit regulations of the contractions of the heart.
- The heart receives impulses from both the sympathetic and parasympathetic divisions of the autonomic nervous system
- Sympathetic are contained in the middle, superior and inferior cardiac nerves.
- Parasympathetic fibers are in branches of the vagus nerve
- The parasympathetic and sympathetic combine to form cardiac plexuses located close to the arch of the aorta
- Fibers terminate in the SA node, the Av node and in the atrial myocardium. some fibers extend to the ventricular part of the hearts conduction system
What are sympathetic nerves also known as?
Accelerator nerves
What are parasympathetic nerves also known as?
Vagus fibers to the heart are inhibitory or depressor nerves
What is a portal system?
What is a vascular anastomosis?
- Movement of blood follows a general rule of thumb often used when studying the circulatory system,
- that it passes through only one capillary network in the systemic circulation from the time it leaves the heart until it returns
However, though this is usually true,
there are exceptions
- Portal system - blood flowing through the systemic circulation passes through two consecutive capillary beds rather than one. For example, blood coming from digestive organs passes through a second capillary network in the liver before returning to the heart.
- Vascular Anastomosis - Direct connection or merger of blood vessels to one another. Blood moves through veins to other veins without passing through an interveining capillary network.
SA node 5 points
- sinoatrial node- embedded in the right atrial muscle near the superior vena cava
- responsible for initiating the electrical impulses that produce sequential atrial and ventricular contraction
- SA nodes impulses travel over special internodal pathways to the AV node (atrioventricular node)
- pacemaker
- specialized cells in the node posess an intrinsic rhythm called automaticity
AV node
- Atrioventricular node - recieves impulses from the SA node velocity of 1m/sec (regular impulses are .3m/sec)
- The AV node and the AV bundle slow the impulse velocity considerably before transmitting it to the ventricles
- The delay prevents impulses from arriving at the ventricles too rapidly in succession, so that they have enough time to fill between contractions.
Bundle of His
- AV bundle
- electrical connection between the atrial and ventricular muscle
- Conducts impulses to the right and left Bundle Branches in the forward direction only.
- one way transmission prevents impulses from traveling backwards from ventricles to atria
Purkinje fibers
- Formed by the subdivisions of the bundle of His
- spread out diffusely from the apex throughout the ventricles transmitting impulses up to a velocity of 4m/sec 6x faster than the impulses can travel over regular ventricular muscle
myocyte
muscle fiber cell
Sarcolemma
Cell membrane that surrounds the cardiac muscle fiber cell or MYOCYTE
Cardiac muscle contraction
- numerous mitochondria in cytoplasm generate ATP
- the Sarcolema (covering) dips deep into the cell forming T-tubules; this allows intracellular transmission of electrical impulses
- The Sarcoplasmic Reticulum is an intercellular network of tubules spread throughout muscle fiber, stores Ca2+
- electrical impulses within the T-tubule stimulate adjacent sarcoplasmic reticulum= Ca2+ release
How does cardiac muscle contract, describe cardiac muscle contraction
- the MYOFIBRIL contains many MYOFILAMENTS
- Myosin (thick) and Actin (thin) contractile proteins.
- Z-line to Z-line defines the sarcomere
- Titin = elastic protein molecule, tethers myosin fiber to Z-line. - The more Titin stretches, the more vigorous the recoil (stronger contraction of the heart muscle)
- During contration, Actin slides over myosin and shortens the sarcomere
Sarcomere
- The basic contractile unit
- Extends from Z-line to Z-line
Titin
- Elastic protein molecule that tethers myosin fiber to the Z-line
Myosin and Actin
- Contractile proteins
- Myosin is thick
- Actin is thin
Muslce fiber is composed of numerous myofibrils, which in turn are composed of numerous myofilaments.
myofilaments are mainly composed of the contractile proteins myosin and actin
Troponin-I
- inhibits actin-myosin interaction during relaxation; keeps tropomyosin over myosin binding sites.
Describe cardiac muscle contraction.
- nerve impulse causes Acetylcholine to stimulate the muscle cell sarcolemma.
- impulse travels deep into the T-tubules causing the sarcoplasmic reticulum to release Ca++ ions
- Ca++ ions bind with and activate troponin C
- Activated Troponin C initiates a complex interaction among all three troponin subunits that REMOVES THE INHIBITORY EFFECT OF TROPOTONIN I
- This allows tropomyosin to move and uncover binding sites
- myosin then binds to actin pull together
- as long as Ca++ ions are present, the attration between actin and myosin persists
- But ATP molecules react with the myosin heads, pulling them back to their resting position
Cross-bridge Cycling
- Sequence of events from nerve pulse through to the myosin and actin pulling together, ending with the ATP pulling the myosin back to its relaxed position
Frank Starling Mechanism
- The inherent ability of the heart to increase its force of contraction as increasing amounts of blood flow into it.
- the greater the diastolic volume of the heart (to a point) - the greater the force of contraction. ( think of an elastic band)
- still occurs if heart is removed from the body, so is independant of neural mechanisms
Preload
- precontraction length of cardiac muscle fiber
- The greater the preload, the greater the force of contraction.
- but too much fiber stretch decreases the force of contraction
Cardiac plexuses 3 points
(conduction system of the heart)
- Located near the arch of the aorta; composed of sympathetic and parasympathetic fibers
- fibers from cardiac plexus accompany right and left coronary arteries to enter the heart
- most fibers end in the SA node, but some end in the AV node and in the atrial myocardium; the nodes are the Hearts pacemakers
Sympathetic nerves in the heart are also known as:
Accelerator Nerves
Vagus fibers are also known as …. In the heart
Inhibitory, or depressor nerves
In what way are conduction system structures in the heart different from ordinary cardiac muscle tissue?
They are more highly specialized than ordinary cardiac muscle tissue and permit only rapid conduction of an ACTION POTENTIAL through the heart
Automaticity
Intrinsic rhythm possessed by the specialized cells in the SA node
Intercalated disks
- gap junctions between muscle cells that are extremely permeable to ions; so the stimulus is easily passed to adjacent cells.
Syncytium
- means muscle mass acts as one fiber
- if one fiber contracts then all the others will contract
Systolic sound
- First heart sound
- believed to be caused primarily by the contraction of the ventricles, and vibrations of the closing AV valves
Diastolic Sound
- Short, sharp sound
- caused by closing of the SL valves (semilunar valves)
Why does blood flow
- Blood flows because of pressure, pressure gradient
- circulates from the left ventricle to the right atrium of the heart because of?
- perfusion pressure…. pressure gradient needed to maintain blood flow through a local tissue
Cardiac output (CO)
The volume of blood pumped out of the heart per unit of time (ml/min or L/min)
Stroke Volume (SV)
- Volume pumped per heartbeat
Calculating Cardiac Output
CO (volume/min)=SV(volume/beat) x HR(beats/min)
Computed by Fick’s formula
Stroke Volume
- The amount of blood pumped by the left ventricle of the heart in one contraction
What influences the contractility of the heart?
- Preload
- chemical factors such as neural, norepinephrine, endocrine, epinephrine
- triggered by stress, exercise, cheap chocolate
List factors that affect heart rate:
Cardiac Pressor reflexes
- Aortic baroreceptors and carotid baroreceptors (located in the aorta and carotid sinus)
- affect the autonomic cardiac control center, and therefore the parasympathetic and sympathetic outflow to help control blood pressure
know the nerves going into and out of heart, controling heart rate etc
Carotid sinus Reflex
- Sensory fibers from the carotid sinus baroreceptors run through the carotid sinus nerve and the glossopharyngeal nerve to the cardiac control center
- parasympathetic impulses leave the cardiac control center, travel through the vagus nerve to reach the SA node
Aortic Reflex
Sensory fibers extend from baroreceptors located in the wall of the arch of the aorta, through the arotic nerve, and through the vagus nerve to terminate in the cardiac control center
peripheral resistance
is the resistance to blood flow imposed by the force of friction between blood and the walls of it’s vessels
What are some factors that influence peripheral resistance?
Blood viscosity
- high hematocrit (percentage of red blood cells)
- anemia, hemorrhage, or other abnormal conditions may also affect blood viscosity
Diameter of arterioles
Vasomotor mechanism: muscles in walls of arteriole may constrict or dilate, changing diameter of arteriole
what happens to resistance and blood pressure with small changes in blood vessel diameter?
- small changes in vessel diameter cause large changes in resistanc, making the vasomotor mechanism ideal for regulating blood pressure and blood flow.
- if you decrease the size of a vessle by 1/2 the resistance increases x16!!!! if you increase the diameter x2, you decrease resistance x16!
changes in blood vessel diameter have a huge impact on BP
What is a Vasomotor Control Mechanism
- Controls changes in the diameter of arterioles
- plays role in maintenance of the general blood pressure and re-distribution of blood
what are vasomotor pressor reflexes?
- a sudden increase in arterial blood pressure stimulates aortic and carotid baroreceptors; results in arterioles and venules of the blood reservoirs dilating
- decrease in arterial blood pressure results in stimulation of vasoconstrictor centers, causing vascular smooth muscle to constrict
what are vasomotor chemoreflexes?
- chemoreceptors located in aortic and carotid bodies are sensitive to hypercapnia, hypoxiqa, and decreased arterial blood pH
Medullary ischemic reflex:
acts during emergency situation when blood flow to the medulla is decreased; causes marked arteriole and venous constriction
Describe vasomotor control by higher brain centres
- Impulses from centers in cerebral cortex and hypothalamus areva** transmitted to vasomotor** centers in the medulla to help control vasoconstriction and dilation;
- Local control of arterioles: several mechanisms produce localized vasodilation; called reactive hyperemia
venous return
the amount of blood returned to the heart by the veins
stress-relaxation effect:
occurs when a change in blood pressure causes a change in vessel diameter (because of elasticity) and adapts to the new pressure to keep blood flowing (works only within certain limits)
gravity
the pull of gravity on venous blood while sitting or standing tends to cause a decrease in venous return (orthostatic effect)
orthostatic hypotension
venous return decreases when standing as opposed to lying down
venous pumps
blood pumping action of respirations and skeletal muscle contractions facilitate venous return by increasing pressure gradient between peripheral veins and venae cava.
Respirations - inspiration increases pressure gradient between peripheral and central veins by decreasing central venous pressure and increasing peripheral venous pressure
Skeletal Muscle contractions: promote venous return by squeezing veins through a contracting muscle and milking the blood toward the heart
One way valves in veins prevent backflow
starlings law of the capillaries
- governs capillary exchange
- at the arterial end of capillary, outward hydrostatic pressure is the strongest force, it moves fluid out of plasma and into intracellular fluid
- at the venous end of capillary, inward osmotic pressure is intracellular fluid; 90% of fluid lost by plasma at arterial end is recovered
- lymphatic system recovers fluid not recovered by capillary and returns it to the venous blood before it is returned to the heart
ADH mechanism changes total blood volume by __________________________
what triggers ADH?
- Antidiuretic Hormone mechanism; ADH - decreases the amount of water lost by the body by increasing the amount of water that the kidneys resorb from urine before it is excreted from the body.
- ADH is triggered by input from baroreceptors and osmoreceptors
Renin-angiotensin-aldosterone system
what does each part do?
Renin- released when blood pressure in the kidney is low, leads to increased secretion of
Aldosterone - stimulates retention of sodium, causing increased retention of water and an increase in blood volume
Angiotensin ll - intermediate compound that causes vasoconstriction, which complements the volume-increasing effects of renin and promotes an increase in overall blood flow
ANP
- Atrial natriuretic peptide mechanism; ANP
- adjusts venous return from an abnormally high level by promoting the loss of water from plasma, causing a decrease in blood volume
- increases urine sodium loss, which causes water to follow osmotically
korotkoff sounds
sounds we hear when using the sphygmomanometer and stethoscope, they appear as the pressure in the cuff is gradually decreased
Systolic blood pressure
the force of the blood pushing against the artery walls while ventriclesw are contracting
diastolic blood pressure
force of blood pushing against the artery walls when ventricles are relaxed
pulse pressure
difference between systolic and diastolic pressure
n around 40
velocity of blood
when a liquid flows from an area of one cross sectional size to an area of larger size, its velocity decreases.
blood flows more slowly through arterioles than arteries because total cross sectional area of arterioles is greater than that of arteries and capillary blood flow is slower than arteriole blood flow.
venule cross-sectional area is smaller than capillary cross sectional area, causing blood velocity to increase in venules and then veins with a still smaller cross-sectional area
pulse
what is it,
what does it indicate
what causes it
- alternate expansion and recoil of an artery
- indicates adequacy of perfusion and blood voume as well as heart function
- alternating increase and decrease of pressure in the vessel
- elasticity of arterial walls allows walls to expand with increased pressure and recoil with decreqawsed pressure
pulse wave
each pulse starts with ventricular contraction and proceeds as a wave of expansion throughout the arteries
gradually dissipates as it travels, disappearing in the capillaries
venous pulse
only detectable in large veins, most prominent near the heart, not of clinical importance
