CV System Physiology 1 Flashcards
What blood vessel is involved in nutrient and waste exchange?
Capillaries. Their walls are thin enough to allow for exchange.
What are the 3 types of capillaries?
Continuous
Fenestrated
Sinusoidal
What type of capillary excludes proteins and cells from passing through?
Continuous
What type of capillary excludes cells? Where are they found?
Fenestrated. Found in the kidney
What type of capillary allows cells and protein to pass through? Where are they found?
Sinusoidal/discontinuous. Found in liver, bone marrow, spleen
What three layers are found in all blood vessels except capillaries?
(1) Tunica intima or interna
(2) Tunica media
(3) Tunica adventitia or externa
What property of blood vessels helps push blood through arteriole system?
Elastic tissue
What property of blood vessels does smooth muscle provide?
Its ability to contract and dilate allows blood to be shunted from one area to another
What protects blood vessels against distention?
The fibrous nature of the tissue
Which blood vessel layer contains collagen and elastic fibers?
Tunica adventitia
Capillaries are comprised of only one of these layers; which is it?
Tunica intima
Which blood vessel layer contains smooth muscle and thus is responsible for vasoconstriction and vasodilation?
Tunica media
What types of blood vessels are resistance vessels due to their smooth muscle?
Arteries and arterioles. Veins lack smooth muscle.
Which layer holds the vaso vasorum seen in larger vessels?
Tunica adventitia
Cardiac muscle is what kind of muscle
Involuntary striated with light (I bands) and dark (A bands) cross bands
Myocardial cells have more of this organelle due to its high oxidative capacity
Mitochondria. Oxidative phosphorylation occurs within the mitochondria.
What cellular feature allows the heart to contract in unison?
The presence of gap junctions between muscle cells allows for easy communication between myocytes.
How do T-tubules differ between cardiac and skeletal muscle cells?
Cardiac: T-tubules contain extracellular fluid high in calcium
Skeletal: T-tubules contain extracellular fluid low in calcium
What structure brings depolarization inside the cardiac muscle and helps regulate cytoplasmic calcium?
T tubules
What prevents tetanic contraction in cardiac muscle?
The long cardiac action potential
What aspect of the action potential prevents a second action potential from taking place?
The long refractory period or plateau period
True or false: the signal for myocardial contraction comes from the nervous system?
False - it comes from auto-rhythmic cells, also called pacemakers.
What is the originator of the cardiac action potential?
The SA node
The majority of calcium used in the heart for muscle contraction comes from what source?
The sarcoplasmic reticulum
What is the name of a chemical that affects the contractility of the heart?
An inotropic agent
Give an example of an inotropic agent that has a positive inotropic effect
Epinephrine, norepinephrine, digitalis. These all increase the force of muscle contractions.
What property allows the SA node to function as the primary pacemaker?
The small size of the cells allow for it to spontaneously depolarize
What acts as a delay station for the action potential?
The AV node.
Why does the AV node delay the action potential?
To allow the atrial muscle to depolarize before the ventricular muscle
What can act as a secondary pacemaker in pathological conditions?
The AV node (Because the SA node is compromised)
What allows for rapid conduction of the action potential?
Bundle of his
Bundle branch
Purkinje fibers specialized tracts
What is the sequence of the electrical impulse in the heart?
SA node –> specialized tracts –> AV node and atrial muscle –> Bundle of his –> bundle branches –> Purkinje fibers –> ventricle muscle
From what system does the SA node get the signal to depress the heart rate?
Parasympathetic nervous system
How does the sympathetic nervous system affect conduction through the electrical system?
It speeds up conduction of the action potential and therefore increases heart rate
What nerve has the greatest influence on the heart?
The vagus nerve
What is the affect of vagal stimulation on the heart?
It serves to slow the conduction of action potentials through the AV node due to the parasympathetic nerve fibers it carries
What is the function of the papillary muscle?
They prevent the A-V valves from bulging too far backwards during the pressure of ventricular contraction and thus preventing lethal blood leaking
What causes the A-V valves to open after systole?
The difference between higher pressure in the atria and lower pressure in the ventricle
How does norepinephrine affect heart contractility?
It increases it. Norepi is a positive inotropic agent.
In which phase do the ventricles fill?
Late diastole
In which phase do we get isovolumic contraction?
Early systole. Isovolumetric contraction refers to the period when the ventricles contract but the volume does not change.
What phase of the cardiac cycle uses up most energy?
The isovolumic contraction of early systole. Because this is when the ventricles eject blood into the aorta and pulmonary trunk.
What is the purpose of isovolumic contraction?
To build up the pressure to overcome the high aortic pressure
In which phase is ejection?
In late systole
When is the relaxation phase?
Early diastole
What causes heart sound 1?
The closing of the atrial-ventricular valves
What causes heart sound 2?
The closing of the pulmonic and aortic valves
When in the cycle is heart sound 1?
Late diastole/early systole
When in the cycle is heart sound 2?
End systole begin diastole
What is end-diastolic volume?
The volume of blood remaining in the ventricles at the end of diastole, which is usually 110-120 milliliters
What is the end-systolic volume?
This refers to the 40-50 milliliters remaining in the ventricle after systole
What device records electrical activity of the heart?
Electrocardiograph
What information do we get from ekg?
Heart rate and rhythm
Axis of the heart
What on an ekg marks atrial depolarization?
The P wave
What on an ekg marks ventricular depolarization?
The QRS complex
What on an ekg marks ventricular repolarization?
The T wave
What effect does excess potassium ions have on cardiac function?
Excess potassium in extracellular fluid causes a dilated, flaccid heart with a slower weaker contraction rate
What effect does excess calcium ions have on cardiac function?
Excess calcium ions cause spastic heart contractions
A deficiency of calcium ions have what effect on cardiac function
A deficiency of calcium ions can cause flaccidity, similar to what is seen with an excess of potassium ions
What 2 heart characteristics influence cardiac output?
Heart rate and stroke volume
What type of circulation has few controls, and is a low pressure/low resistance system?
The pulmonary system
What blood vessels act as capacitance vessels?
Veins and venules. Capacitance vessels store electrical charge
What increases venous return?
Vasoconstriction
Which blood vessels have valves?
Veins and venules
What is the primary basis of blood flow in the human body?
Pressure gradients
Where is the highest pressure in the vessels of the cardiovascular system found?
Aorta and systemic arteries
Where is the lowest pressure in the vessels of the cardiovascular system found?
Venae cavae
What are the four pressures that affect capillary exchange?
(1) Plasma oncotic pressure
(2) Plasma hydrostatic pressure
(3) Interstitial oncotic pressure
(4) Interstitial hydrostatic pressure
Which of the four pressures favors filtration?
(1) Plasma hydrostatic pressure
(2) Interstitial oncotic pressure
(3) Interstitial hydrostatic pressure
Which of the four pressures is actually a negative pressure or “suction”?
Interstitial hydrostatic pressure
What are three mechanisms for edema?
(1) Increased plasma interstitial pressure
(2) Decreased plasma oncotic pressure
(3) Increased interstitial oncotic pressure
What is the Frank-Starling law?
The law states that the stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles, before contraction (the end, diastolic volume), when all other factors remain constant.
The Frank-Starling law or mechanism is controlled by which actions?
(1) Length-tension: pre-load volume causing initial cardiac myocyte stretching and tension
(2) Force-velocity: the stretching and tension within the muscles increases the velocity of fibre shortening and increases contractual force
How will decreased blood protein synthesis cause edema?
By decreasing plasma oncotic pressure
What will influence lymph flow?
Smooth muscle tone
Skeletal muscle contraction
Pressure in the right atrium or the vena cava at the level of the heart is known as what?
Central venous pressure
What will increase venous blood flow and decrease venous pressure?
Skeletal muscle contraction
Where are baroreceptors located?
In the aortic arch and carotids
What do baroreceptors sense?
Blood pressure changes
What cranial nerves innervate the baroreceptors?
Carotid sinus baroreceptor is innervated by CN IX
Aortic arch baroreceptor is innervated by CN X
What kind (not type) of neurotransmitters are released when baroreceptors are stimulated by high blood pressure?
Inhibitory neurotransmitters
What do these inhibitory transmitters accomplish?
Inhibition of vasomotor and cardioregulatory centre of the medulla oblongata
How does the stimulation of the Cardioregulatory centre affect blood pressure?
Increased parasympathetic stimulation to the heart causes a decreased heart rate and contractile force
How does stimulating the Vasomotor centre affect blood pressure?
Decreased sympathetic stimulation to blood vessels resulting in vasodilation
What is accomplished by stimulation baroreceptors?
A decrease in blood pressure due to the vasodilation
True or False: Baroreceptors can also increase blood pressure?
True, they can increase blood pressure along the same pathways
Where are chemoreceptors located?
Aortic arch and carotids
What are chemoreceptors sensitive to?
Low blood oxygen as a result of decreased blood flow due to low blood pressure
What are the 3 isoforms of creatine kinase and where is each isoform located?
(1) CK-MM in skeletal/cardiac muscle
(2) CK-BB in smooth/non-muscle cells
(3) CK-MB in cardiac muscle
What kind of neurotransmitter is released when chemoreceptors are stimulated by low pressure?
Excitatory neurotransmitters. These are released to induce a response to bring the blood pressure back up.
What do these excitatory neurotransmitters do?
They increase the sympathetic firing down neurons that innervate smooth muscle of blood vessels which causes vasoconstriction
What is accomplished by stimulation of chemoreceptors?
An increase in blood pressure by vasoconstriction
How does increased vagal output cause decreased blood pressure?
Via its parasympathetic effects that cause a decreased heart rate leading to a decreased cardiac output leading to a decreased blood pressure
How does the kidney affect blood pressure?
Via renin angiotensin system: Decreased BP –> decreased gfr –> release of renin –> eventually leads to release of aldosterone –> kidneys reabsorb Na+ and water –> increased Blood volume –> increased BP
How does adh affect BP?
Low BP –> adh release –> kidney holds onto water –> increase blood vol. –> increased BP
In metabolic control of blood flow decreased/lower oxygen causes release of metabolites e.g. carbon dioxide, lactate etc. These compounds cause what kind of change in the blood vessel?
Vasodilation of the blood vessels
What is the name of the control that protects against high pressure damage?
Autoregulation
What is the net result on blood vessels of autoregulation?
Vasoconstriction
What is the long term control of blood flow i.e. compensation for some type of tissue ischemia?
Angiogenesis
What is the primary catecholamine for alpha adrenergic receptors?
Norepinephrine. Alpha receptors have high affinity for norepinephrine and lower affinity for epinephrine. Beta 1 receptors have high affinity for isoprenaline. Beta 2 receptors have high affinity for epinephrine.
Which vascular beds have primarily alpha receptors?
Skin, renal and splanchnic vasculature
What affect does norepi have on smooth muscle cells in the vascular beds?
Vasoconstriction. Vascular smooth muscle have alpha 1, alpha 2, and beta 2 adrenergic receptors. Alpha receptors have high affinity for norepinephrine while beta 2 receptors have high affinity for epinephrine. Norepinephrine vasoconstricts while epinephrine vasodilates.
What is the primary catecholamine for beta 2 receptors?
Epinephrine
Which vascular beds have primarily beta 2 receptors?
Coronary and skeletal muscle vessels
What affect does epi have on smooth muscle in the vascular beds?
Vasodilation
Which of the ans branches has most control over circulation?
Sympathetics via Norepi and Epi (Vasoconstriction and vasodilation respectively)
Which vascular beds are over perfused at rest?
Skin, splanchnic, and renal
Brain ischemia caused by an increase in csf pressure is known as what?
Cushing’s reflex. Don’t confuse this with Cushing’s Disease which is when a tumor of the pituitary gland overproduces ACTH.
When, during the cardiac cycle, do the coronaries get their blood flow?
During diastole. Because pressure in the aorta is the highest and thus overcomes the pressure within the coronary arteries.
