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38 Cards in this Set
- Front
- Back
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Is there higher arterial pressure in the systemic or pulmonary circulation? What are the pressures?
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The systemic circulation has a higher pressure of 93mm/Hg. Pulmonary circulation 12mm/Hg
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Describe the direction of blood flow through the heart
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1. Blood flows through the superior and inferior vena cava into the right atrium
2. The pressure build up opens the right AV (tricuspid) valve, the right ventricle contracts, and blood is pushed through the pulmonary semilunar valve. 3. Blood travels through the pulmonary arteries and veins to end up in the left atrium 4. Blood then travels throught the left AV (bicuspid) valve (mitral), the ventricle contracts, and then the blood goes throught the aortic semilunar valve to the rest of the body. |
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How long do AV nodal cells delay conduction and what is the purpose of this?
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They delay conduction by 0.1 seconds and this is to assure that the atrium contracts fully before the ventricle starts its contraction.
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What is a P-wave?
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This is the change of membrane potential in atrial depolarization of muscle cells(myocytes) in the heart.
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What does the QRS complex represent?
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This represents the time period of ventricular excitation
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What is a T-wave?
What % of cardiac cells are conducting cells? |
This is the repolarization of ventricular muscle.
- 1% |
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What happens during the ST segment?
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The ventricles contract
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What is Pouiseulle's Law?
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delta-P= F x R
delta- P= pressure gradient along the length of a rigid tube F= flow of fluid R= resistance to fluid flow |
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What is the formula for cardiac output?
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CO= HR x SV
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What are some properties os SA nodal cells?
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These pacemaker cells lack voltage-gated Na+ channels found in myocardium. The upstroke of AP is due to the opening of voltage gated Calcium (L) type channels.
- The repolarization is due to opening of voltage-gated K+ channels. |
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Describe Ach's action on muscarinic receptors in the heart
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The Ach is released from parasympathetic neurons and binds to the muscarinic receptors. This increases K+ efflux and decreases Ca2+ influx which hyperpolarizes the cell and decreases HR.
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Actions on the AV and SA nodes are described as what type of effects?
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actions on the SA node are (Chronotropic effects) and the AV node is (Dromotropic effect)
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Which cells are the pacemaker cells?
What is the difference between NE activation of B1 receptors on the SA node compared to the ventricles? |
SA and AV nodes are both pacemaker cells however the AV nodes is so at a much lower rate (20 to 40 bpm)
NE activation of B1 receptors on the SA node increase HR while activation on the ventricles increases contractility |
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What is the formula for MAP?
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MAP= CO x R
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What is systole and diastole?
What is the formula for SV? |
systole: period of contraction
diastole: period of relaxation SV= EDV- ESV |
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What is the Frank Starling Mechanism?
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Increasing sarcomere length of cardiac muscle fibers increases SV
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What happens to blood volume during isovolumetric contraction?
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The blood volume is equal to EDV
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When does the Aortic valve close and the mitral valve open?
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When the pressure in the aorta exceeds the pressure in the ventricle. This results in Isovolumetric relaxation
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When does the Aortic valve open and the mitral valve close?
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When the pressure in ventricle exceeds pressure in aorta. This results in Isovolumetric contraction.
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What is the relationship between venous pressure and cardiac output?
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There is a direct relationship between the two.
- an increase in venous pressure would increase EDV |
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what % of blood volume makes up different areas of the heart?
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-9% is in the heart
-11% is in the arteries -7% is in the arterioles and capillaries -61% is in the veins and venules!!! |
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What does the skeletal muscle pump do?
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It increases venous return by contracting muscles
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what are 4 factors that increase venous pressure?
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1. sympathetic nerve activity
2. increased blood volume 3. increase activity of skeletal muscle pump 4. increase in inspiration movements. |
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define what is meant by an "increase in contractility"
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An increase in developed tension w/o a concomitant change in resting muscle length.
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What is the Ejection Fraction (EF)?
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This is the ratio of stroke volume (SV) to end-diastolic volume (EDV).
EF= SV/EDV. |
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What does beta1 adrenergic stimulation directly affect?
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Contractility!!
-This in turn will increase SV |
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What are the two ways cardiac muscle can alter its contractility and how does it do it?
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It can do so by either phosphorylation of voltage gated ca2+ channels or by phosphorylation of the regulatory protein Phosphotamban.
-The phosphorylation of Phosphotamban increases the Ca2+-ATPase activity of the SR, ca2+ is than removed from the cytosol faster which makes the time of ca-troponin binding shorter; this creates a shorter duration of contraction. |
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What part of the heart does the parasympathetic system affect?
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only the conducting system.
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What are some novel properties of Cardiac Muscle compared to Skeletal muscle?
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-20% change in muscle length changes force development 5-fold
-can increase contractility -cannot be tetanized |
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what property of cardiac muscle prevents tetanus?
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Its long refractory period.
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What are the two major roles that Arterioles play in the vascular system?
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1. Determine the relative distribution of blood flow to individual organs
2. Determine resistance to blood flow across the entire cardiovascular system. |
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What are some properties of Smooth muscle?
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-it is not striated
-innervated by the autonomic nervous system -contains actin, myosin, tropomyosin, but not troponin -has 1/3 the conc. of myosin as striated muscle but 2x the actin content. -can develop as much tension as striated muscle but it takes more time. |
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What are some differences between smooth and skeletal muscle contraction?
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-contraction or relaxation of smooth muscle can be initiated by hormones and paracrines
-smooth muscle contraction can be triggered by myogenic stimuli -smooth muscle lacks a specialized end plate region associated with the release of neurotransmitter -some smooth muscle plasma membranes generate pacemaker potentials leading to spontaneous contraction (ex. stomach) |
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Describe the organization of contractile proteins in smooth muscles
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-The actin and myosin are arranged in long diagonal bundles.
-Consequently, no striations and no sarcomeres -Cross bridge cycling is much slower. |
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Describe the process of transmitter binding to agonist receptors on smooth muscle
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1. The receptor will recognize the transmitter and the alpha subunit will bind to phospholipase C which cleaves pip2 into IP3.
2. ca2+ will enter voltage-gated channels located in caveoli while ca2+ release from the SR can either be induced through ca2+ triggered ca2+ release or via IP3. 3. When the SR stores become depleted, the SR signals a store operated ca2+ channel to open, allowing ca2+ to enter |
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Describe the process of smooth muscle contraction
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1. Intracellular levels of ca2+ increase and binds to calmodulin (CaM)
2. Calmodulin than activates myosin light chain kinase (MLCK) 3. MLCK phophorylates light chains in myosin heads and increases myosin ATPase activity 4. Active myosin crossbridges slide along actin and create muscle tension. |
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Describe the process of Smooth muscle relaxation
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1. ca2+ in cytosol decreases when ca2+ is pumped out of the cell or back into the SR
2. ca2+ unbinds from calmodulin (CaM) 3. Myosin phosphatase removes phosphate from myosin, which decreases myosin ATPase activity. 4. The reduction in myosin ATPase results in decreased muscle tension. |
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How are smooth and cardiac muscle similar in the way that they are controlled?
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-They are both under involuntary control of the ANS
-They both contain fibers that are electrically linked via gap junctions. |
