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Animal Physiology circulatory system

Terms in this set (39)

Systemic
Components of ____ circulatory system: heart, arteries, capillaries, & veins.
Heart
Propulsive organ.
Arteries
Act as a pressure reservoir and transport blood away from the heart.
Capillaries
Sites of transfer of substances from the blood to the tissues.
Veins
Return blood to the heart and serve as a blood reservoir.
Blood
___ is oxygenated in the organs of gas exchange (lungs or gills), returned by the veins to the heart, and pumped to the systemic arteries.
Open circulation
____ occurs in most invertebrates.
• blood (hemolymph) is empties from the arteries into an open space (hemocoel).
• blood bathes tissues directly (no capillaries).
Foot muscles
Blood pressure in bivalve mollusk a is generated by the contraction of ____.
Closed circulation
____ occurs in all vertebrates and some invertebrates. A continuous circuit of blood flow through arteries, capillaries and veins.
Dorsal aorta
Closed circulation in water-breathing teleost fishes.
The unidirectional flow of blood through the chambers of the heart is maintained by valves like those at the sinoatrial and atrioventricular junctions.
• blood is ejected from the ventricle into the bulbus and then into a short ventral aortaa*.
• respiratory (gill) circulationn*: blood flows through the gill capillaries and becomes oxygenated by absorbing O2 from the water.
• blood is then delivered to a long _____* which carries it to the somatic.
• systemic circulationn*: blood flows through all the tissues and becomes deoxygenated as cells absorb blood O2.
Systemic circulation
Closed circulatory system in mammals.
_____:
• oxygenated blood flows from the left side of the heart through the aorta and into systemic arteries
• the pressure in the arteries generated by the heart forces blood through the capillariess* (microcirculation)
• capillaries provide blood to every tissue
• *blood O2 is unloaded into tissues and replaced with CO2 (the waste product from metabolism)
• deoxygenated blood flows back to the right side of the heart through systemic veinss* (at lower pressure)
Respiratory circulation
Closed circulatory system in mammals.
______ (pulmonary or lung):
• deoxygenated blood flows from the right side of the heart to pulmonary arteries
• blood is circulated through lung tissue by pulmonary capillariess* and oxygenated
• during breathingg*: CO2 is removed from the blood and replaced with O2 from the atmosphere
• oxygenated blood returns to the left side of the heart through pulmonary veins
Lymphatic system
Closed circulatory system in mammals.
_____:
• recovers fluid lost from the blood to tissues and returns it to a low pressure point in the systemic venous system (close to the heart) through the thoracic duct
• lymphh*: contains white blood cells, no red cells
Pacemaker
____ cells in the sinoatrial node. The _____ is a group of cells capable of spontaneously generating electrical activity.
• cells may be neurons (in neurogenic hearts) or muscle cells (in myogenicc* hearts)
In vertebrates: the ____ are myogenic
• weakly contractile cells
The generation of a heartbeat: electrical impulses from ____ cells propagate to all the cells of the heart through gap junctions that connect all of them. Contractile myocardial cells contract in response to this electrical impulse.
Purkinje fibers
Propagation of electrical activity.
Propagation occurs through gap junctions between cells.
• begins at the sinoatrial node
• spreads through both atria and into the atrioventricular node
• the bundle of Hiss* branches into right and left bundles, which then subdivide into _____ that extend to both ventricles.
Pacemaker potential
The ____ is a depolarization of the membrane of a pacemaker cell that precedes an action potential.
• the ____ is not an AP
The generation of an action potential in pacemaker cells:
• after an AP: high K+ conductance and moderately high Ca2+ conductance
• Ca2+ conductance does not fall completely after an AP
• K+ conductance then drops and the membrane depolarizes steadily again (the _____)
• Na+ and Ca2+ channels open: rising phase of the AP
• K+ conductance then increases: falling phase of the AP
Acetylcholine
Parasympathetic regulation of heart rate.
______ is released from parasympathetic terminals of the vagus nerve (cranial nerve X).
• it increases K+ conductance and reduces Ca2+ conductance in pacemaker cells.
• the membrane remains near K+ equilibrium potential longer, delaying the onset of the pacemaker potential.
Norepinephrine
Sympathetic regulation of heart rate.
_____ is released from sympathetic terminals and binds adrenergic receptors on the pacemaker cells.
• it activates Ca2+ channels, accelerating depolarization (the pacemaker potential)
Cardiac muscle
Skeletal muscle contraction after an action potential.
Unlike in skeletal muscle, _____ contraction is never sustained.
• a sustained _____ contraction would lead to muscle paralysis and cardiac failure.
• the myocardial AP frequency is configured so that each AP will trigger a single, unsustained muscle contraction (a "twitch")
APs in skeletal muscles are very short in duration.
• each AP results in a brief muscle contraction (a twitch)
• increased frequency of APs results in sustained contraction
plateau phase
In the cardiac muscle there is a sustained depolarization (a _____) after the rising phase of the AP due to a sustained high Ca2+ conductance and a delay in the increase in K+ conductance.
Effects:
• membrane remains at the refractory period longer, preventing subsequent APs
• only one brief contraction occurs (no sustained contractionss*)
Right atrium; pulmonary veins
Circulation through the heart.
Right side: inferior and superior vena cava => _____ => right ventricle => pulmonary arteries
Left side: _____ => left atrium => left ventricle => aorta
Systole
The contraction of the ventricle (____) and the closing of the atrioventricular valve forces blood through the arteries with high pressure, and the atrium fills with blood with low pressure.
Diastole
The relaxation of the ventricle (____) and the opening of the atrioventricular valve forces blood from the atrium to the ventricle.
Chambers
Circulation through linear heart chambers.
If the heart were linear:
• bilateral circulation and the reversal of blood flowing into the atrium or the ventricle:
• pattern would be inappropriate for flow through ____.
Ventricle
Circulation through a sinuously looped heart.
There is no bilateral flow in a sinuously looped heart.
• collisions between streams of blood entering the heart are minimized
• the momentum of flow is maintained to direct the flow to next chamber
• blood vessels are also curved and receive the swirling blood from the ____ without flow disruption
Cardiac output
The volume of blood pumped from one ventricle per unit of time.
Stroke volume
The volume of blood ejected from a ventricle during one beat of the heart.
Norepinephrine
____ accelerates heart rate and cardiac output, but does not increase the stroke volume.
...
Cardiac output during increase in cellular oxygen requirement.
During exercise, as the heart rate increases, cardiac output increases. As oxygen demand increases, the difference in oxygen content between arteries and veins (A-V) _____ (as more O2 is consumed by the tissues, less O2 reached the veins).
Diastole shortening
Limits to heart rate.
_____:
• limited by the rates of filling and emptying of the ventricles.
Coronary circulation (systemic circulation within the heart):
• reduced during systole because of the occlusion of coronary capillaries
• increases during diastole
Therefore: a minimal diastole time is required to allow sufficient coronary circulation.
Ventricular ejection
Sequence of events in a heartbeat.
1. Mid diastole
2. Atrial contraction
3. Isometric ventricular contraction
4. _______
5. Ventricular diastole
Mid diastole
Relaxed ventricles, closed outflow valves, and high blood pressure in the outflow channels (aorta and pulmonary arteries).
Atrial contraction
High atrial pressure forces the blood into the ventricles.
Isometric ventricular contraction
The atrioventricular valves close when ventricle myocardial cells contract, but no change in volume occurs because the outflow valves are still closed.
Reasons for this:
• high pressure in the outflow arteries
• flow in the aorta is actually reversed
Ventricular ejection
(Systole) When the pressure in the ventricles exceeds the pressure inside the outflow channels, the aortic valves are forced to open and blood escapes through the outflow channels: isotonic contraction of the ventricle.
Ventricular diastole
When the pressure inside the outflow channels exceeds the pressure inside the ventricles, the aortic valves close (blood flow in the aorta is actually reversed).
Systole
Changes in pressure and volume during a heartbeat.
• more pressure builds on the left ventricle and aorta (systemic circulation) during _____.
• lower pressure in the right ventricle and pulmonary arteries (pulmonary circulation)
• stroke volume is the same for both sides
Aortic valve
Pressure-volume loops for the right and left ventricles of the mammalian heart.
The stroke volume is the same for both sides, but:
• the aortic pressure is higher than in the pulmonary arteries, so the left ventricle must reach a higher pressure to exceed the aortic pressure and open the _____.
• if there is high arterial blood pressure: the heart must do more work.
Electrocardiogram
An ______ is the summation of electrical activities of all cells within each region of the heart, detected as small potential changes from points all over the body.
• ventricular depolarization is higher because most of the cells in the heart are at the ventricles
• the atrial repolarization activity is masked by the ventricular depolarization activity.
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