Cardiovascular System Flashcards
heart anatomy
location:
-in the mediastinum btwn second rib and fifth intercostal space
- on the superior surface of diaphragm
- to the left of the midsternal line
- anterior to the vertebral column, posterior to the sternum
-enclosed in pericardium, a double-walled sac
pericardium
- superficial fibrous pericardium
- protects, anchors, and prevents overfilling
- Deep two-layered serous pericardium
- Parietal layer lines the internal surface of the fibrous pericardium
- Visceral layer (epicardium) on external surface of the heart
- Separated by fluid-filled pericardial cavity (decreases friction)
layers of the heart wall
- epicardium
* visceral layer of pericardium - myocardium
* cardiac muscle, layer that contracts
* connective tissue of heart (anchors cardiac muscle fibers, supports great vessels and valves, limits the spread of action potentials to specific paths - endocardium
* lines chambers, is continuous with vessels
chambers
4 chamber
-> 2 atria (receiving chambers; partition called interatrial septum
-> 2 ventricles (pumping chambers, separated by the interventricular septum)
atria: the receiving chambers (entranceway)
- > 3 veins entering right atrium
- superior vena cava
- inferior vena cava
- coronary sinus (from heart)
- > 2 veins entering left atrium
- right and left pulmonary veins
ventricles: the discharging chambers
- > vessel leaving the right ventricle
- pulmonary trunk (artery) to lung has limited oxygen
- > vessel leaving the left ventricle
- aorta to body- has oxygen
pathway of blood through the heart
- The heart is two side-by-side pumps
- Equal volumes of blood are pumped to the pulmonary and systemic circuits
-Pulmonary circuit (right)
is a short, low-pressure circulation
-Systemic circuit (left)
blood encounters much resistance in the long pathways
-Size of the ventricles reflects these differences
the pathway of blood flow through the heart
slide 16
coronary circulation
- Blood supply to the heart muscle itself
- Collateral routes provide additional routes for blood delivery
- O2 utilization – 70 to 80% extracted from blood supply
- If vigorous exercise must increase blood flow by dilating coronary vessels
- Practically one capillary per muscle fiber
- Impairment in flow = angina
- Partial/complete blockage of coronary = myocardial infarction (heart attack)
coronary artery disease
treatment:
- CABG- great saphenous vein
- ballon angioplasty
- cardiac stents-metal mesh tubes
heart valves
atrioventricular (av) valves:
- close when ventricles contract, prevents backflow
- tricuspid valve (right)
- mitral (bicuspid) valve (left)
semilunar (sl) valves:
- aortic semilunar valve(left)
- pulmonary semilunar valve (right)
-chordae tendineae (collagen strings) anchor AV valve cusps to papillary muscles (prevent valves from turning inside out)
valve disease
Faulty valves makes heart work harder, Either blood leaks backward or flow is restricted through valves. (murmurs, mitral valve prolapse, aortic valve stenosis)
cardiac muscle
gap junctions, striated, short
skeletal vs cardiac MM
- stimulation:
- skeletal MM is stimulated by nerve ending;
- cardiac MM are self excitable; intrinsic conduction system - contraction:
- skeletal MM contract from motor unit
- cardiac MM contracts as a unit or not at all (gap junctions) - absolute refractory:
- cardiac MM has longer period, prevents tetanic contractions (stop pumping action)
cardiac MM contraction
- depolarization: Na channels open and Na rushes in. Membrane potential rises from -90mV to +30mV
- Transmission of depolarization wave Opens special calcium channels in membrane to release 20% of calcium. Then T tubules cause SR to release the remaining calcium needed for contraction.
- Excitation-Coupling Ca provides signal for cross bridge activation (calcium channel blockers – HTN)
- Repolarization – Ca channels close and K channels open & returns to resting voltage
energy requirments
- heart is exclusively aerobic
- has more mitochondria than skeletal MM
- cardiac MM able to use whatever nutrient available, including lactic acid
- danger of inadequate blood supply to heart is not lack of nutrients but lack of O2
sequence of excitation:
Cardiac pacemaker cells are found:
1. Sino-atrial node
2. Atrioventricular node (delay for atria to finish contracting)
3. Atrioventricular bundle (bundle of HIS) (only electrical connection btwn atria and ventricle)
4. Right and Left bundle branches (intraventricular septum)
5. Subendocardial conducting network (Purkinje fibers)
SLIDE 31
Arrhythmias
- Irregular heart rhythms due to defects in intrinsic conduction system
- Atrial-fibrillation (a-fib) & ventricular fibrillation (v-fib), can be life threatening if not treated within minutes
extrinsic innervation of the heart
- heartbeat is modified by the ANS
- cardiac centers are located in the medulla oblongata
- Cardioacceleratory center innervates SA and AV nodes, heart muscle, and coronary arteries through sympathetic neurons
Cardioinhibitory center inhibits SA and AV nodes through parasympathetic fibers in the vagus nerves (note no heart muscle)
the vagus nerve (parasympathetic) decreases heart rate
true
sympathetic cardiac nerves increase heart rate and force of contraction
true
electrocardiography
- ECG or EKG
- a composite of all the action potentials generated by nodal and contractile cells at a given time
3 waves:
1. P WAVE: DEPOLARIZATION OF SA NODE (ATRIA)
- QRS COMPLEX: VENTRICULAR DEPOLARIZATION
- T WAVE: VENTRICULAR REPOLARIZATION
slide 36
depolarization, repolarization steps
- Atrial depolarization, initiated by the SA node, causes the P wave.
- with atrial depolarization complete, the impulse is delayed at the AV node
- ventricular depolarization begins at apex, causing the QRS complex. atrial repolarization occurs
- ventricular depolarization is complete
- ventricular repolarization begins at apex, causing the T wave
- ventricular repolarization is complete
Heart sounds
2 sounds (lub-dub) associated with closing of heart valves
- > first sound occurs as AV valves close and signifies beginning of ventricular systole (contraction)
- > second sound occurs when SL valves close at the beginning of ventricular diastole (relaxation)
heart murmurs
abnormal heart sounds most often indicative of valve problems
-swishing sound since valves are incompetent
Phases of the cardiac cycle:
1. ventricular filling
- takes place in mid-to-late diastole (relaxation)
- > AV valves are open, SL valves are closed
- > 80% of blood passively flows into ventricles
- > atrial systole occurs, delivering the remaining 20%
- > end diastolic volume (EDV): volume of blood in each ventricle at the end of ventricular diastole, maximum amount of blood
Phases of the cardiac cycle:
2. ventricular systole (contraction)
- atria relax and ventricles begin to contract
- rising ventricular pressure results in closing of AV valves
- Isovolumetric contraction phase (all valves are closed)
- in ejection phase, ventricular pressure exceeds pressure in the large arteries, forcing the SL valves open
- end systolic volume (ESV): volume of blood remaining in each ventricle
Phases of the cardiac cycle:
3. Isovolumetric relaxation
- occurs in early diastole
- ventricles relax
- backflow of blood in aorta and pulmonary trunk closes SL valves
- ventricles again are closed chambers because all valves are closed
This valve is found between the right atrium and the right ventricle
tricuspid valve
Which of the following structures is an exception to the general principle surrounding blood vessel oxygenation levels?
pulmonary artery and pulmonary veins
Atrial repolarization occurs during this period of time, seen on an ECG
QRS complex
Cardiac output (CO)
- volume of blood pumped by each ventricle in 1 minute
- CO=heart rate (HR) x stroke volume (SV)
HR = number of beats per minute
SV = volume of blood pumped out by a ventricle with each beat
Cardiac output is main indicator if the supply (circulation) is meeting demand (O2 at tissues)
cardiac output
with endurance training, the SA node comes under greater influence of acetylcholine (PNS) which has slowing effect on HR
regulation of stroke volume
SV= EDV- ESV ((amt of blood in ventricle during diastole vs and the volume of blood remaining after contraction)
Three main factors affect SV:
Preload
Contractility
Afterload
regulation of stroke volume
Preload: degree of stretch of cardiac muscle cells before they contract (frank-starling law of the heart). ENhanced cardiac filling
-> at rest, cardiac muscle cells are shorter than optimal length
- > slow heartbeat and exercise increase venous return
- > increased venous return distends (stretches) the ventricles and increases contraction force
regulation of stroke volume
contractility: contractile strength at a given muscle length
- positive inotropic agents increase contractility:
- increased calcium influx due to sympathetic stimulation
- hormones (thyroxine, glucagon, and epinephrine)
- drug digitalis
- negative inotropic agents DECREASE contractility:
- acidosis
- increased extracellular potassium
- calcium channel blockers
regulation of stroke volume
afterload: pressure that must be overcome for ventricles to eject blood
- hypertension increases afterload, resulting in increased ESV and reduced SV
regulation of heart rate
Sympathetic stimulation of pacemaker cells:
*norepinephrine causes the pacemaker to fire more rapidly (and at the same time increases contractility)
Parasympathetic NS- inhibits pacemaker
- the heart at rest exhibits vagal tone
- parasympathetic activity has little or no effect on cardiac contractility
- hormones
- ions
- age, gender, exercise, and temp
chemical regulation of heart rate
- hormones
* Epinephrine from adrenal medulla enhances heart rate and contractility
* Thyroxine increases heart rate and enhances the effects of norepinephrine and epinephrine - intra- and extracellular ion concentrations (e.g., Ca and K) must be maintained for normal heart function
other factors that influence heart rate
Age – fastest in fetus, declines with age
Gender – females faster than males
Exercise – increases HR, training decreases overall
Body temperature – heat increases HR
The “lub-dup” heart sounds are produced by _______.
the closing of the atrioventricular valves (“lub”) and the closing of the semilunar valves (“dup”).
Atrial systole occurs _______ the firing of the sinoatrial node.
after
Predict what would happen to the end systolic volume (ESV) if contraction force were to increase
it would decrease
