Chap 17 Circulatory Function Flashcards
If the output of the left heart were to fall below that of the right heart, blood would accumulate in the?
Pulmonary circulation.
If the output of the right heart were to fall below that of the left heart, blood would accumulate in the?
Systemic circulation.
Which side of heart pumps lower pressure?
pulmonary circulation
pressure is highest in what part of circulatory system?
capillaries
most important factors governing flow of blood..
Pressure, resistance and flow (CO)
what % of RBCs in blood?
40-45%
what happens in circulatory shock?
decrease in bld vol, vessel radii, and BP.
As result many sml vessels collapse as BP drops to the point that it cant overcome the wall tension. Collapse makes it hard to insert venous lines.
What is Dispensability?
ability of vessel to stretch and accommodate am increased vol of bld. veins more so.
Pericardium?
fibrous covering around the heart. Protection and lubrication.
Myocardium?
muscle layer of atria and ventricles, produce pumping action. Intercalated disks btwn cardiac muscles contain gap junctions and allow for immediate communication of electrical signals.
Intercalated disks in heart muscle are for?
gap junctions serve as low-resistance pathways of ions and electrical impulses from one cardiac cell to another.
What proteins are used to diagnose myocardial infarct?
Troponin T, I and C
cardiac muscle relies on what heavily for contraction?
calcium
Digoxin (cardiac glycosides) are?
inotropic drugs that increase cardiac contractility by increasing the free intracellular calcium concentration in cardiac muscle.
Normal properties of heart cells and how they relate to action potential. (learn obj 1).
have striations and composed of sarcomeres that have actin and myosin filaments and contain many large mitochondria bc of continuous energy needs. Also have intercalated disks…
proteins that regulate actin and myosin binding?
Tropomyosin and troponin complex
What is an ECG?
Electrocardiogram- recording of the electrical activity of the heart that can be obtained when electrodes are applied to various positions on the body and connected to electrocardiograph monitor.
What are specialized pacemaker cells?
generate impulses at a faster rate than do other types of heart tissue, and conduction tissue transmits impulses faster than other types of heart tissue. these control rhythm of heart.
SA node
where rhythmic impulse is generated.
- fastest intrinsic rate of firing (60-100 BPM)
- “the Pacemaker”
AV node
impulse from atria is delayed before passing to ventricles.
AV bundle
conduct impulse from atria to ventricles
Purkinje system
conducts impulse to all parts of ventricles
Action potential def:
3 main parts:
sequential change in electrical potential that occurs across a cell membrane when excitation occurs.
3: resting, depolarization and repolarization.
Action Potential resting state:
when membrane is polarized (+ on outside, -inside)
Action potential depolarization:
change in direction of polarity (+ inside, -outside)
Action potential repolarization:
reestablishment of polarity of resting membrane potential.
what are the major charge carriers in cardiac muscle cells?
Na, Ca, K
The action potential of cardiac muscle is divided into 5 phases:
0- the upstroke or rapid depolarization 1- early repolarization 2- plateau 3- rapid repolarization 4-restinting membrane potential
cardiac muscle has 3 types of membrane ion channels:
1-fast sodium channel
2-slow calcium-sodium channel
3-potassium channel
Phase 0 of action potential:
in atrial, ventricular muscle and in purkin fibers, open fast Na channels. responsible for spike onset of AP
Phase 1 of AP:
occurs at peak of AP and signifies inactivation of fast Na channel with abrupt decrease of Na permeability
Phase 2 of AP:
plateau of AP. caused by slower opening of Ca channels. Ca ions enter muscle during this phase and play a key role in contractile process of muscle fibers.
Phase 3 of AP:
reflects final rapid repolarization and begins with the down slope of the AP. Slow channels close and the influx of Na and Ca ceases. Sharp rise in K permeability= rapid outward movement of K facilitating reestablishment of resting mem pot.
-distribution of Na and K returns to normal rest state.
Phase 4 of AP:
Resting mem potential. the Na/K pump is activated, transporting Na out of cell and K back in.
-the pacemaker cells in SA and AV nodes are spontaneous
2 main types of AP in heart:
1-slow response: initiated by slow Ca channels and found in SA node (pacemaker) and in AV node conduction fibers.
2-fast response: because of the opening of the fast Na channels, occurs in normal myocardial cells of the atria, ventricles, and purkin fibers.
- doesn’t initiate AP
- originate in special slow-response of cells of SA mode and are conducted to fast response myocardial cells in atria and vent
- effect change in mem pot to the threshold level. when reach threshold, Na channels open to initiate rapid upstroke of the phase 1 AP.
The amplitude and rate of phase 1 are important to?
conduction velocity of fast response.
What catecholamine’s increase heart rate and how?
epinephrine and norepinephrine. By increasing the slope or rate of phase 4 depolarization.
What is absolute refractory period?
phase 0-2 and part of 3. cell cant depolarize here
The longer length of the absolute refractory period of cardiac muscle is important in?
maintaining the alternating contraction and relaxation that ate essential to the pumping action of the heart and for prevention of fatal arrhythmias.
Bradycardia and manifestations:
slower than 60 bpm. less blood to body tissues.
- damage to electrical system
- aging
- infections
- medications
- too much K
- low thyroid
- electrolyte imbalance
Tachycardia and manifest:
BPM higher than 100.
-
Atrial Fibrillation
rapid irregular beat.
- fever
- COPD
- sleep apnea
- obesity
- excess alcohol
- diabetes
Atrioventricular blocks
heart bloch between atria and ventricles. message from AV node doesn’t reach vents.
- ischaemia,
- infarction,
- fibrosis
- drugs
Premature ventricular contraction
where the heartbeat is initiated by Purkinje fibers in the ventricles rather than by the sinoatrial node, the normal heartbeat initiator.
- In a PVC, the ventricles contract first and before the atria have optimally filled the ventricles with blood, which means that circulation is inefficient. However, single beat PVC abnormal heart rhythms do not usually pose a danger and can be asymptomatic in healthy individuals
- adrenaline excess
- high bld CA
- smoking
- lack sleep
- drugs/caffeine
Ventricular tachycardia
a rapid heart beat that arises from improper electrical activity of the heart presenting as a rapid heart rhythm, that starts in ventricles.
-Life threatening bc can cause low BP
ventricular fibrillation
uncoordinated contraction of the cardiac muscle of the ventricles in the heart, making them quiver rather than contract properly.
-most commonly identified arrhythmia in cardiac arrest patients
Asystole
known as flatline, is a state of no cardiac electrical activity, hence no contractions of the myocardium and no cardiac output or blood flow. Asystole is one of the conditions that may be used for a medical practitioner to certify clinical or legal death.
- treated by cardiopulmonary resuscitation (CPR) combined with an intravenous vasopressor such as epinephrine (adrenaline)
-Possible underlying causes include the Hs and Ts.
Hypovolemia
Hypoxia
Hydrogen ions (acidosis)
Hypothermia
Hyperkalemia or Hypokalemia
Hypoglycemia
Tablets or Toxins (drug overdose)
Cardiac Tamponade
Tension pneumothorax
Thrombosis (myocardial infarction or pulmonary embolism)
Trauma (hypovolemia from blood loss)
Explain the impact of atrial fibrillation on CO
hello
What is stenosis
Stiffening of valve flaps. Narrow of valves- impedes flow
Ischemia
Blockage of coronary arteries leads to deficient O2 supply to myocardium
Heart P wave
Depolarization of atria. What triggers contraction
QRS complex
Depolarization of ventricles
T wave
Repolarization of ventricles
