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outline 15
Comparative Physiology- Renner Lecture 15
| Question | Answer |
|---|---|
| what are the basic components of a circulatory system | pump delivery system transfer system return system |
| compare vertebrate and invertebrate circulatory system components | pump: heart is single vs. multiple delivery system: arteries vs arteries transfer system: capillaries vs hemocoel (open flow space) return system: veins vs ostia in the heart (1 way valves) |
| how is movement of blood achieved? | 1. heart contractions 2. elastic recoil of arteries–windkessel effect, keeps blood moving during diastole 3. body movement-verts-squeeze blood vessels. inverts-hemocoel to move hemolymph 4. contractions of muscle that surround heart |
| what is meant by elastic recoil of arteries ? | artery fills with blood during systole (ventricle contract) and during diastole (heart relaxation, low bp) it recoils to push blood through the artery |
| invertebrate blood is called that | hemolymph |
| how do muscular pumps aid in blood movement | contraction of muscles surrounding the vessels, it is aided by 1 way valves in veins |
| what is an open circuit system? | in invertebrates (not all), heart contraction delivers blood to artery which empties into the hemocoel |
| features of an open circuit system? | 1. large hemocoel (~40% body space) 2. low arterial pressure 3. limited control of velocity, distribution of blood flow 4. limited gas exchange capability 5. movements of fluid-body movement, contractions, auxiliary hearts in high demand areas |
| insects with open circuit system have low capability for gas exchange, how do they compensate for that? | insects use a tracheal system for gas exchange. Fine tubes which air goes into, no blood. |
| arthropod hearts are__________located and contain _____________which are perforations | dorsally, ostia |
| in arthropods, perforations in the dorsal tubular heart in arthropods, function in blood return | ostia |
| in arthropods, when hemocoel is compressed, what happens to the blood? | enters ostia through 1 way valves which seal as heart fils with blood |
| in arthropods, pulsatile organs that act as boosters to supply high O2 to energy consuming structures such as wings | auxiliary hearts |
| this functions as predominant gas exchange organ in insects | tracheal system |
| what is the hemolymph's function in insects? | nutrient/waste exchange |
| this provides directionality for hemolymph as it is emptied from the heart to hemocoel | septum |
| crustaceans have _____________ heart | chambered (single chamber) |
| arteries and aorta branch more extensively in crustaceans , emptying into localized spaces called _______________ and blood is directed by _________ | lacunae, sinuses |
| these structures in crustaceans direct blood to the gills then back to the heart | sinuses |
| type of circulatory system of vertebrates and some invertebrates (cephalopods: squids+octopi) | closed system |
| what is a predominant feature of closed circulatory system? | blood is always enclosed in a tube or blood vessel |
| what type of blood vessels are there in a closed circulatory system? rank in order of blood flow | arteries, arterioles, capillaries (exchange), venules, veins |
| what are some advantages to having a closed circulatory system? | 1. less body space for circulation~10-15% 2. #1 pumping mechanism is heart 3. exchange at capillaries happens by diffusion. branched to minimize distance from capillary to cell 4. redistribution of blood flow, thru capillaries 5. high exchange rate |
| prototype of vertebrate heart? where is a modified version found? | nearly straight tube consisting of four chambers. it is found, with minor modifications, in fish. |
| these valves prevent back flow when ventricles are in diastole (relaxed) | semilunar valves |
| when chambers contract in sequence, what happens? | heart delivers blood |
| in fish, blood flowing in a single stream forward to where? why? | stream flows forward to the gills for gas exchange, and to the body to deliver O2 and pick up wastes |
| atria are____________walled, while ventricles are ______________ | thin, thick |
| why are ventricles thick walled? | because they are high pressure pump requiring thick, muscular walls |
| in a single circuit pump, venous blood first enters _______________ via ____________________ | sinus venosus, common cardinal vein |
| contraction of sinus venosus results in what? | forces blood across the sinatrial valve into the atrium |
| atrium contracting forces blood across ______________________ into the ventricle | atrioventricular valve |
| the ventricle has enough power to pump the blood through the ______________________ and back to the heart | speripheral circulation |
| blood leaving the ventricle passes a series of ____________ and enters the _____________ | semilunar valves, truncus arteriosus |
| from the truncus arteriosus, the blood enters the _____________ for ________________ | gills, gas exchange |
| what is a benefit of having a single-circuit pump | highly efficient because concentrations of dissolved O2 in water are limited |
| gills in single circuit pump function as an exchange organ extracting oxygen from water use what kind of mechanism? | countercurrent mechanism |
| blood entering gills is _______________ and it moves in the _______________ direction as the water current | deoxygenated, opposite |
| why does countercurrent mechanism work? | because concentration gradient always favors O2 delivery from H2O to blood, and CO2 leaving the blood to the water |
| the transitional form of the heart represented is represented by this organism | air-breathing lung fish or Dipnoi |
| what is a feature unique to dipnoi ? | it can survive conditions of drought and water stagnation by using pulmonary ventilation. And use gill respiration when conditions exist with high oxygen tension in the water |
| pulmonary circulation resulted in this | double circuit pumping system that is found in birds and mammals |
| what are some features that birds and mammals share? | 1. high metabolic rates 2. endothermic 3. have lungs that are continuously ventilated 4. pumping system in both- equal amounts of blood pumped to systemic and pulmonary circulation at all times |
| in double circuit pumping system this pump operates at low pressure | pulmonary pump |
| the pulmonary pump pumps blood to the ______________ and back to the ______________ | lungs, heart |
| why does the pulmonary artery contain deoxy blood if its an artery? | because it carries blood away from the heart to the lungs so they can oxygenate it |
| superior and inferior vena cava collect deoxy blood from what parts of the body? | superior: head-heart inferior: feet-heart |
| describe the path of the blood in human heart | superior/inferior vena cava, coronary sinus>right atrium>tricuspid valve>right ventricle>pulmonary semilunar valve>right/left pulmonary arteries>lungs>left atrium via 4 pulmonary veins (oxy blood)>bicuspid valve>left ventricle>aortic semilunar valve>aorta |
| valves between atria and ventricles | atrioventricular valves |
| what are the three atrioventricular valves in vertebrate hearts? | mitral(bicuspid) valve, tricuspid valve, cordae tendineae |
| valve between left atrium and left ventricle | mitral (bicuspid) valve |
| the valve on the high pressure side of the heart | mitral valve |
| valve between right atrium and right ventricle | tricuspid valve |
| when do atrioventricular valves open? | when atrial pressure is greater than ventricular pressure. They close when ventricular pressure increases |
| strong bands of connective tissue that link the valves to ventricular myocardium | cordae tendinae |
| these structures function to prevent AV valve eversion during ventricular systole (contraction) | cordae tendinae |
| these valves are found between the ventricles and the aorta and pulmonary arteries | semilunar valves |
| these valves prevent back blood flow from pulmonary and aortic vessels during ventricular diastole (relaxation) | semilunar valves |
| what are the two semilunar valves in vertebrate hearts? | aortic valve, pulmonary valve |
| since valves are passive, what drives them to function? | change in pressure |
| what are the two kinds of valves? | atrioventricular and semilunar |
| how do the two sets of valves operate? | they operate out of sequence |
| when ventricles contract, AV valves close. What happens to semilunar valves? | semilunar valves open |
| what is meant by cardiac muscle operating as a functional syncytium? | it means they operate as a unit instead of a bunch of cells. Atria/ventricles function as units |
| low resistance pathways between cells which allow depolarization current to travel from one myocardium fiber to the next rapidly | intercalated discs |
| what are the two units of the functional syncytium that is the heart | atrial and ventricular units |
| how do intercalated discs provide low resistance pathways? | resting cell membrane resistance is ~300 ohms/cm^2. Intercalated discs' resistance is 50 ohms/cm^2 |
| how can the heart function as a syncytium? | due to low resistance pathways that are the intercalated discs |
| T/F: heart only maintains rhythm when neural and vascular connections are available | FALSE. the heart has a regular rhythm that can be maintained in the absence of vascular and neural connections |
| what causes the average heart rate of 72 beats per min | Sinoatrial node firing 70-80 times per minute |
| this structure has the fastest inherent rate of depolarization | Sinoatrial node |
| Atrioventricular node fires at ______________times per min, purkinjee system fires at _____________times per min | 40-60, 15-40 |
| in more primitive hearts, the pace of the rhythm is set by excitable cells found in this structure | sinus venosus |
| pacemaker of the mammalian heart | SA node |
| in mammals, the remnant of the sinus venosus makes up this structure in the posterior wall of the right atrium near the entracnce of the superior vena cava | sinoatrial node |
| in humans SA node is found at | junction of superior vena cava and right atrial wall |
| these cells are specialized cells that are inherently excitable found in the SA node. They are also not contractile and set the pace of the heart | P cell (pacemaker cells) |
| dimensions of P cells | 1.5 cm long 0.3-0.5 cm wide 1mm deep |
| how does resting potential of P cells compare to mycardial cells ? | P cells: -55 to -60 mV Myocardium: -80 to -90 mV |
| why can p cells polarize? | because due to the membrane potential of -55mV to -60mV, the cell is leaky to Na+, electrical and chemical gradients both favor Na+ in |
| this separates right and left atria | interatrial septum |
| the right atrium receives blood from all parts of the body except | the lungs |
| P cells are leaky to Na+ that will lead to what? | gradual decay of the resting potential |
| how long does it take for depolarization to reach threshold in P cells? | 750 mSec |
| P cells reaching threshold potential results in what? | opening of slow voltage gated Na+-Ca2+ channels, leading to an influx of Na+ and Ca2+ which in turn will result in an action potential |
| after an action potential has resulted in P cells, what happens to VgNa+/Ca2+ cells? What other channels activate? | channels inactivate in about 150 mSec, leading to Voltage gated K+ channels opening favoring K+ efflux |
| what repeats the cycle of AP in P cells? | passive influx of Na+ after VgK+ channels close |
| initial rise in membrane potential in myocardial is due to what? how long does that last? | opening of fast VgNa+ channels which last for 1-2mSec, then, they close. This causes the membrane potential to reach and cross threshold |
| Action potential in myocardial cells | 1. fast VgNa+ open (1-2mSec), then close. threshold reached 2. slow VgNa+ open (100-200mSec). keep depolarization. Ca2+ goes in, adding + and contributing to contractile process 3. slow VgNa+/Ca2+ close, VgK+ open. K+ efflux 4. Na+/K+ pump for gradient |
| what is relative refractory period in myocardial cells? | period during which an intense stimulus can lead to a premature ventricular contraction (extra systole) |
| at rest, what maintains ion gradient after AP has occurred in myocardial cells? | Na+/K+ pump, also Ca2+ ATPase pump clears Ca2+ from sarcoplasm |
| these channels are open briefly in Action potential in myocardial cells and can't be reactivated in a depolarized state | fast VgNa+ channels |
| in action potential in myocardial cells, what 2 functions does Ca2+ serve? | 1. add + charge to the inside of the cell 2. contribute to the contractile process |
| Action potential in myocardial cells, Fast VgNa+ channels open for _____________mSec, then slow VgNa+ respectively for ____________mSec | 1-2, 100-200 |
| Action potential in myocardial cells, when VgNa+/Ca2+ close, what happens after? | VgK+ channels open, increasing K+ efflux due to increased conductance to K+ driving membrane potential back to resting potential |
| what is the goal of the conduction pathway of the heart that conducts electrical signals? | to result in ordered contraction of the heart chambers |
| what generates electrical signal that travels through specialized conduction pathways? | in vertebrates; sinus venosus mammals; Sinoatrial node |
| what is the general pathway of electrical conduction in mammals? | SA node fires-->impulses travel across the atria along internodal pathways causing the atria to contract (get last 1/3 of blood out into ventricle) |
| SA node sends signals across atria via these structures | internodal tracts |
| regions that have a higher conduction rate than conduction rate from one atrial cell to another. contribute to unit atrial contraction | internodal tracts |
| from internodal tracts, signal reaches | AV node |
| acts as a "brake" slowing conduction from atria to ventricles, insures that atrial contraction is complete before initiating ventricular systole | AV node |
| from AV node signal travels down | bundle of His |
| split into two branches, helps signal travels along base of the heart and back up the lateral walls of the ventricle | bundle of His |
| from the lateral walls of the ventricle, the signal enters | the purkinjee system |
| non-contractile cells, large, also contain fast voltage gated Na+ channels, branch and excite myocardial cells | the purkinjee system |
| what regulates heart rhythm? how? | sympathetic and parasympathetic nervous system both systems innervate the SA node and AV node |
| __________________ nervous system has direct effect on the ventricle while ______________________ nervous system has minimal effects on the ventricle | sympathetic, parasympathetic |
| the amount of blood pumped by each ventricle per beat | stroke volume (SV) |
| average SV | 70 mL/beat |
| SV x Number of contractions/min | cardiac output (CO) |
| average CO | 70mL/beats x 72 beats/min= 5040 mL/min ~ 5mL/min |
| what happens when the sympathetic system is activated | 1. increased HR 2. increased contraction strength - CO with sympathetic= 2-3x resting value, in athletes, ~9x resting value |
| what happens when the parasympathetic system is activated | 1. increased HR 2. modest decrease in contraction strength |
| what happens when blood load is increased ? | the heart has the intrinsic ability to adapt to changing loads of blood- Starling's law of the heart |
| what does starling's law allow | adaptation of cardiac output to meet changing body needs |
| when blood entering venous return is increased, what happens to the heart? | heart contracts with increasing force |
| parallel elements are __________________________ in cardiac muscle than skeletal muscle | more pronounced |
| parallel elements are | sarcolemma, connective tissues |
| these are greater in cardiac muscle with respect to cell volume | sarcolemma and connective tissues |
| skeletal muscle fiber is ______________ in diameter while cardiac muscle fiber is ______________ in diameter | 10-100 microns, 5-20 microns |
| how are the actin-myosin in cardiac muscles relative to skeletal? what happens with stretch? | they are more disorganized with stretch, they line up better |
| why do actin-myosin line up during stretch? | to increase cross bridge formation to increase contraction strength |
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