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outline 15

Comparative Physiology- Renner Lecture 15

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
Created by: rusulali97



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