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Cardiovascular_LP
Cardiovascular_Physiology
| Question | Answer |
|---|---|
| What are the functional componenets of the cardiovascular system? | 1. Heart 2. Blood Vessels 3. Blood |
| What general fucntions do the heart/blood vessels/blood provide? | 1. Transportation (everything transported by blood 2. Regulation (intrinsic vs extrinsic) 3. Protection (against blood loss) 4. Production/Synthesis (production of ANP) |
| Describe cardiac muscle | 1. striated 2. short branched cells 3. uninucleated & central 4. intercalated discs 5. t-tubules larger, over z-discs & branched internally 6. high concentration of mitochondria |
| What are the 4 chambers of the heart? | 1. Left & Right Atrium 2. Left & Right ventricles |
| What are the 2 systems of the heart? | 1. Pulmonary (blood to lungs) 2. Systemic (blood to body) |
| T/F Contraction of the heart starts at the APEX | True, the apex is at the very bottom portion of the heart |
| T/F Fibrous membrane separates the chambers of the heart physically & electrically | TRUE |
| What are the functions of the valves in a heart? | Prevent backflow of blood |
| What are the major valves in the heart? | 1. Atrioventricular valve 2. Semilunar valve |
| What does the atrioventricular valve do? | prevent backflow to the atria |
| What does prolapse mean? | falling off/apart |
| How is prolapse prevented in the atrioventricular valves? | By the chordae tendinae (prevent flap from flipping down) * tensioned by the papillary muscles |
| What does the semilunar valves do? | Either aortic or pulmonic * Prevent backflow into ventricles |
| Describe the INTRINSIC conduction system | 1. Consists of 'pacemaker' cells and conduction pathways 2. Coordinate the contraction of the atria and ventricles |
| What are pacemaker cells also known as? | Autorhythmic cells |
| Describe the characteristics of pacemaker/autorhythmic cells | 1. smaller than contractile cells 2. don't contain any myofibrils 3. no organized sarcomere structure (do not contribute to contractile force of heart) 4. Unstable membrane potential 5. Mygoenic |
| Describe sympathetic activity among pacemaker cells | 1. Norepinephrine & Epinephrin increase I(f) channel activity a. binds to Beta 1 adrenergic receptors -> activate cAMP & increase I(f) channel open time b. Cause more rapid pacemaker potential & faster rate of action potentials |
| List the 3 effects of sympathetic activity in pacemaker cells | 1. increase heart rate 2. increase conduction of Action Potentials 3. increase contractility |
| How is the membrane potential of pacemaker cells unstable? | 1. 'bottoms out' at -60mV 2. 'drifts upwards' to -40mV, forming a pacemaker threshold potential (depolarization/extra leakage) |
| What does it mean for pacemaker cells to be MYOGENIC? | upward drift allows membrane to reach tresh. (-40mV) BY ITSELF |
| The upward drift allowing the membrane to reach threshold potential (-40mV) by itself is due to... | 1. slow leakeage of K+ out & faster leakage Na+ in 2. Ca2+ channels opening as membrane approaches threshold 3. slow K+ channels open as membrane depolarizes causing an EFFLUX of K+ and a repolarization of membrane |
| When slow leaker of K+ out & faster leakage of Na+ in happens, what does it cause? | 1. slow depolarization 2. occurs through I(f) channels (f=funny) that open at negative membrane potentials & start closing as membrane approaches threshold potential |
| What happens when Ca2+ channels open as membrane approaches threshold? | 1. at threshold additional Ca2+ ion channels open causing more rapid depolarization 2. these deactivate shortly after |
| Describe parasympathetic activity among pacemaker cells | Ach binds to muscarinic receptors 1. increase K+ permeability & decrease Ca2+ permeability - hyperpolarize membrane * results in longer time to threshold = slower rate of action potentials |
| What are the effects of parasympathetic activity in pacemaker cells | 1. decrease heart rate 2. decreased conduction of action potentials 3. decreased contractility |
| What are the special aspects of CONTRACTILE cells? | 1. intercalated discs 2. more mitochondria than skeletal muscle 3. Less sarcoplasmic reticulum (Ca2+ also influxes from ECF reducing storage needs) 4. larger t-tubules (internally branched) 5. myocardial contractions are GRADED |
| Describe intercalated discs in contractile cells | High convoluted & interdigitated junctions 1. joint adjacent cells with desmosome & fascia adherens 2. allow for synctial activity via gap junctions |
| What type of tissues are fascia adherens found in? | NON-EPITHELIAL CONNECTIVE TISSUE |
| Describe the action potential of a contractile cell | 1. Ca2+ plays a major role 2. Action potential is longer in duration than a 'normal' action potential due to Ca2+ entry Describe the phases of a contractile cell's action potential |
| What happens at depolarization in a contractile cell's action potential phase? | 1. Depolarization due to gap junctions or conduction fiber action 2. voltage gated Na+ channels open... close at 20mV |
| What happens at temporary repolarization in a contractile cell's action potential phase? | Open K+ channels allow some K+ to leave the cell |
| What happens at the plateau phase in a contractile cell's action potential phase? | Voltage gated Ca2+ channels are fully open (started during initial depolarization) |
| What happens at the repolarization phase in a contractile cell's action potential phase? | Ca2+ channels close & K+ permeability increase as slower activated K+ channels open, causng a quick repolarization |
| What is the significance of the plateau phase? | Helps to PREVENT SUMMATION which results in the lack of TETANUS, you don't want the heart to be in tetanus because that means the heart stop pumping and you're DEAD! |
| Describe the refractory period of a skeletal muscle's action potential | In a skeletal muscle fast-twitch fiber, the refractory period is VERY SHORT compared with the amount of time required for the development of tension |
| Describe the refractory period of a cardiac muscle's action potential | The Cardiac Muscle fiber's refractory period lasts almost AS LONG AS THE entire muscle twitch |
| List the phases of cardiac contraction | 1. Initiation - action pot. via pacemaker cells to conduction fibers 2. excitation-contraction coupling 3. contraction 4. relaxation |
| What happens during excitation-contraction coupling phase in cardiac contraction? | 1. starts with CICR (Ca2+ induced Ca2+ release) 2. Ca2+ signal (Ca2+ from SR and ECF) binds to TROPONIN to initiate myosin head attachment to actin |
| What happens at CICR (Ca2+ induced Ca2+ release)? | 1. AP spreads along sarcolemma 2. t-tubules contain voltage gated L-type Ca2+ chans open upon depol. 3. Ca2+ enter myocardial cell & opens RyR Ca2+ release chans 4. Release of Ca2+ from SR cause Ca2+ 'spark' 5. multiple 'sparks' form a Ca2+ signal |
| What happens at the contraction phase in cardiac contraction? | 1. same as skeletal but strength varies * sarcomeres are not all or none as it is in in skeletal musc. * REPONSE IS GRADED 2. length tension relationship exist |
| What does it mean when a response is GRADED? | Low levels of cytosolic Ca2+ will not activate as many myosin/actin interactions and the opposite |
| T/F The strongest contraction generated when stretced between 80 & 100% of maximum (physiological range) | TRUE |
| What causes stretching? | The filling of chambers with blood * Atria stretches first * Ventricles stretch next |
| What happens at the relaxation phase of cardiac contraction? | 1. Ca2+ transported back into SR 2. Ca2+ transported out of cell by a facilitated Na+/Ca2+ exchanger (NCX) 3. as ICF Ca2+ levels drop, interaction btw myosin/action stop 4. sarcomere lengthens |
| What is the definition of a cardiac cycle? | The sequence of events as blood enters the atria, leaves the ventricles & starts over |
| What synchronizes the cardiac cycle? | The intrinsic electrical conduction system |
| How is the rate of the cardiac cycle influenced? | Influenced by the sympathetic & parasympathethic systems of the ANS |
| Describe the electrical conduction pathway of the cardiac cycle | 1. Initiated @ SA Node 2. internodal pathways 3. AV Node 4. Atrioventricular bundle 5. Bundle branches 6. Purkinje cells |
| During the electrical conduction pathway, what happens at the internodal pathways? | Depolarization spread thru the atria via gap junctions & internodal pathways to the Atrio-Ventricular node (AV node) a. fibrous connective tissue matrix of heart prevents further spread of APs to ventricles b. slight delay at the AV node occurs |
| Why is there a slight delay at the AV Node? | 1. due to slower formation of action potentials 2. allows further emptying of the atria 3. want atria to complete contraction before ventricle starts |
| During electrical conduction pathway, what happens at the atrioventricular (AV) bundle? | AP travel down AV bundle which splits into L & R AV bundles (bundle branches) & then into conduction myofibers (Purkinje cells) |
| Describe Purkinje cells | They are large in diameter & conduct impulse very rapidly * causes the cells at the apex to contract near simultaneously (good for ventricular ejection) |
| What is the function of the ECG? | Same as EKG... a. recording of electrical activity b. can be mapped to the cardiac cycle |
| What is diastole? | period of relaxation |
| What is systole? | period of contraction |
| The cardiac cycle is an alternating period of systole's and diastole's, describe the cycle in terms of that | 1. rest 2. atrial systole 3. isovolumetric ventricular contraction 4. ventricular ejection 5. isovolumetric ventricular relaxation 6. back to atrial & ventricular diastole |
| @ Rest, what is diastole/systole? | 1. both atria & ventricles in diastole 2. blood is filling atria & ventricles due to low pressure conditions |
| @ Atrial Systole, what happens? | Ventricular filling completes |
| @ Isovolumetric ventricular contraction, what happens? | 1. increased pressure in ventricles cause AV valves to close (pressure building) - creates 'lub' heart sound 2. atria go back to diastole 3. no blood flow as semilunar valves are closed as well |
| @ Ventricular ejection, what happens? | Intraventricular pressure overcomes aortic pressure 1. semilunar valves open 2. blood is ejected |
| @ Isovolumetric ventricular relaxation, what happens? | 1. intraventricular pressure drops below aortic pressure * semilunar valves close = 'dup' sound 2. pressure still hasn't dropped enough to open AV valves so volume remains same (isovolumetric) |
Created by:
lophung
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