Chapter 18/19 Cardiovascular System Flashcards
an increase in the volume of a container filled with air would have what effect on the pressure of the container
- increase the pressure
- decrease the pressure*
- no effect
- a temporary effect
which of the following delivers air to the lobes of the lungs
- primary bronchi
- secondary bronchi* -> lobar bronchi
- tertiary bronchi
- terminal bronchioles
heart anatomy
- approx the size of a fist
- in the mediastinum between 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 overfiling
- deep two layered serous pericardium:
- parietal layer
- visceral layer
- separated by fluid pericardial cavity (decreases friction)
parietal layer of heart
- lines the internal surface of the fibrous pericardium
- serous pericardium
visceral layer of the heart
- epicardium
- on external surface of the heart
- serous pericardium
- visceral layer of the pericardium
myocardium
- cardiac muscle
- layer that contracts
- connective tissue of heart
- anchors cardiac muscle fibers
- supports great vessels and valves
- limits spread of action potentials to specific paths
endocardium
- lines chambers
- is continuous with vessels
chambers
- 4 chambers
- two atria- receiving chambers, partition called interatrial septum
- two ventricles- pumping chambers, separated by the interventricular septum
atria: receiving chambers (entraceway)
- 3 veins entering right atrium: superior vena cava, inferior vena cava, coronary sinus (from heart)
- veins entering left atrium- right and left pulmonary veins
ventricles: 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 system circuits*
- pulmonary circuit (right)- short, low pressure circulation
- systemic circuit (left)- blood encounters much resistance in the long pathways
- size of the ventricles reflect these differences
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
- CABG (coronary artery bypass graft)- great saphenous vein
- balloon angioplasty
- cardiac stents- metal mesh tubes
atrioventricular (AV) valves
- close when ventricles contract
- prevent back flow
- tricuspid valve (right)
- mitral (bicuspid) valve (left)
semilunar (SL) valves
- aortic semilunar valve (left)
- pulmonary semilunar valve (right)c
semilunar (SL) valves
- aortic semilunar valve (left)
- pulmonary semilunar valve (right)
chordae tendineae (collagen strings)
- anchor AV valve cusps to papillary muscles
- prevents valves from turning inside out
valve disease
- faulty valves make heart work harder
- either blood leaks backward or flow is restricted through valves
- murmurs, mitral valve prolapse, aortic valve stenosis
which of the following statements is true
- all arteries transport oxygen rich blood
- the right side of the heart is the systemic circuit pump
- equal volumes of blood are pumped to the pulmonary and system circuits at any moment*
- the left side of the heart pumps blood to the lungs
- all of the above is true
blood being pumped out of the left ventricle enters the ____
- pulmonary artery
- aorta*
- coronary sinus
- venae cavae
- pulmonary vein
skeletal vs cardiac MM
- stimulation- skeletal MM is stimulated by nerve endings; cardiac MM are self-excitable, intrinsic conduction system
- contraction- skeletal MM contract from motor unit; cardiac MM contracts as a unit or not a tall (gap junctions)
- absolute refractory- cardiac MM has longer period, prevents tetanic contractions (stop pumping action)
cardiac MM contraction
- depolarization
- transmission of depolarization wave
- excitation-coupling
- repolarization
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)
repolarzation
-Ca channels close and K channels opens and returns to resting voltage
energy requirements
- heart is exclusively aerobic
- has more mitochondria than skeletal MM
- cardiac MM able to use whatever nutrient is 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:
- sinoatrial node- generates impulses
- atrioventricular node (delay for atria to finish contracting
- atrioventricular bundle (bundle of HIS) (only electrical connection between atria and ventricle)
- right and left bundle branches (intraventricular septum)
- subendocardial conduction network (purkinje fibers)- depolarize the contractile cells of both ventricles
arrhythmias
- irregular heart rhythm due to defects in intrinsic conducting system
- atrial fibrillation (a-fib) and 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
- cardioaccelerator 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)
electrocardiography
- electrocardiogram (ECG or EKG)- a composite of all the action potentials generated by nodal and contractile cells at a given time
- 3 waves:
- p wave- depolarization of SA node (atria)
- QRS complex- ventricular depolarization
- T wave- ventricular repolarization
elevated ST segment
- MI
- prolonged QT interval could increase risk of ventricular arrhythmias
heart sounds
- two sounds: lub-dup -> 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 valve 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
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
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
isovolumetric relaxation
- occurs in early diastole
- ventricles relax
- backflow of blood in atria 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
- mitral
- tricuspid*
- bicuspid
- semilunar
- aortic
which of the following structures is an exception to the general principle surrounding blood vessel oxygenation levels
- pulmonary artery
- aorta
- pulmonary veins
- both a and c*
- all of the above
atrial repolarization occurs during this period of time seen on a ECG
- P wave
- QRS complex*
- T wave
- S-T segment
cardiac output (CO)
- volume of blood pumped by each ventricle in one 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)
- 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 (amount of blood in ventricle during diastole vs and the volume of blood remaining after contraction)
- three main factors affect SV:
- preload
- contractility
- afterload
preload
- degree of stretch of cardiac muscle cells before they contract (frank starling law of the heart). Enhanced cardiac filling
- contributor to stroke volume
- at rest, cardiac muscle cells are shorter than optimal length
- slow heartbeat and exercise increase venous return
- increase venous return distends (stretches) the ventricles and increases contraction force**
contractility
- regulation of stroke volume
- contractile strength at a given muscle length
- positive inotropic agents increase contractility:
- increased Ca2+ influx due to sympathetic stimulation
- hormones (thyroxine, glucagon, and epinephrine)
- drug digitalis
- negative inotropic agents decrease contractility:
- acidosis
- increased extracellular K+
- calcium channel blockers