Physio exam review Flashcards
What is the consequence of a septal defect between the L and R ventricles?
Blood flow from L to R because the L ventricle is under much greater pressure than the right.
What is the difference in pressure between the L and R atria?
Zero. If there is a septal defect in the atria, there is no blood flow between the two chambers.
What prevents the mitral and tricuspid valves from everting to lower pressure regions in the atria during ventricular systole?
Chordae tenineae
Which has a greater volume, the right or the left heart?
They are equal
What is the pressure in the left atrium while standing?
Sub-atmospheric, -2 to -4 atm. This makes it easy for blood to return from the lungs to the heart.
Which muscles in the heart keep the valves from everting?
The papillary muscles prevent eversion in conjunction with the chordae tendineae.
What prevents mitral regurgitation?
Chordae tendineae
What is the ultimate fate of the valve leaflets after a myocardial infarction?
A myocardial infarction causes dilation of the heart muscles (they become loose), which increases their size. However, the leaflets remain the same size and, therefore, regurgitation occurs.
What is the most posterior structure in the heart?
Left atrium
What makes up most of the anterior surface of the heart?
Right ventricle
What other vessels following the aortic valve would be compromised in the case of a clogged aortic valve?
Coronary arteries –> They supply blood to the myocardium.
Which valves are larger and why? The AV valves, or the aortic and pulmonary valves?
The AV valves are larger. The aortic and pulmonary are smaller because they are send the same volume of blood through a smaller opening and thus achieving a greater velocity.
Give the relative percentages of blood output to organs
Renal 25%, GI 25%, Muscles 25%, Cerebral 15%, Coronary 5%, and skin 5%.
Why does the brain require such a relatively high percentage of cardiac output?
Because it does not store glucose and needs a continuous flow.
Do arteries have valves? Veins?
Arteries NO. Veins YES, one-way valves.
Where is blood found at its highest velocity?
Aorta
Which blood vessels have the greatest surface areas?
Capillaries
Which blood vessels hold the greatest volume of blood?
Veins, 2/3
Which blood vessels exert the greatest control of BP? Why?
Arterioles, because they display the greatest change in size. Capillaries don’t change size, arteries don’t change size, veins change SLIGHTLY, but not as much as arterioles.
Through which blood vessels does the greatest drop in blood pressure occur?
Arterioles.
What is the only part of the vasculature that moves? What receptors mediate this movement?
Arterioles. Alpha-1 receptors constrict, Beta-2 receptors dilate.
If the pressure can be dropped at the ____ of a system, the total flow will go up.
At the END of a system –> Blood flow = (Arterial pressure - VENOUS PRESSURE)/Vascular resistance. NOTE how increasing the pressure at the beginning of the system WITHOUT reducing the end pressure will DECREASE TOTAL FLOW.
What is the range of cycles per second the human voice is capable of, in Hz?
300-
Define autoreceptor and what they do
Alpha 2 receptors on the sympathetic postganglionic nerve terminals. They are activated by norepinephrine from presynaptic nerve terminals and INHIBIT FURTHER RELEASE of norepinephrine from the SAME TERMINAL.
Define “heteroreceptors” and what they do
Alpha 2 receptors found on the parasympathetic postganglionic nerve terminals in the GI tract. Norepinephrine is released from sympathetic postganglionic fibers that synapse on these parasympathetic postganglionic nerve terminals. When activated by norepinephrine, the alpha 2 receptors cause inhibition of release of Ach from the parasympathetic nerve terminals. IN THIS WAY, the SNS indirectly inhibits GI function by inhibiting the parasympathetic activity.
What substance(s) activate alpha 1 receptors?
Equally sensitive to epi and nor, HOWEVER, only norepinephrine released from adrenergic neurons is present in high enough concentrations to activate alpha 1 receptors.
What is the general action, mechanism of action, and G protein for the following:
- ) Alpha 1
- ) Alpha 2
- ) Beta 1
- ) Beta 2
1.) Alpha 1: Excitatory (constricting), increase IP3 and intracellular [Ca2+], Gq.
2.) Alpha 2: Inhibitory (relaxing), inhibition of adenylyl cyclase and thus decrease cAMP, Gi.
3&4.) Beta 1 AND Beta 2 (they have the same action): Stimulation of adenylyl cyclase and thus decrease cAMP, Gs.
What happens when Beta 1 receptors are activated in the kidney?
Renin is secreted, which activates angiotensin (constricts blood vessels). Also increases secretion of ADH and aldosterone. Essentially, IT INCREASES BLOOD PRESSURE.
What compound phosphorylates proteins at the end of the Alpha 1 mechanism?
Protein kinase C
In the final step for the mechanism of action for Beta 1&2, what action does adenylyl cyclase perform?
It catalyzes the conversion of ATP to cAMP.
Where is norepinephrine primarily released from?
Postganglionic sympathetic adrenergic nerve fibers.
What action does Beta 2 stimulation have on its target tissues?
Relaxation/dilation. Dilates vessels to skeletal muscle (for fight or flight), dilates GI tract wall (so it doesn’t squeeze shit out), dilates bladder wall (so it doesnt squeeze peepee out), and dilates bronchioles (so you can breathe more better).
Describe the effects of catecholamines on alpha 1&2, and beta 1&2 receptors.
Alpha 1: Nor and epi equipotent, though compared to beta receptors, it is relatively insensitive. HIGHER CONCENTRATIONS of catecholamines are necessary to activate alpha 1. Physiologically, the only way to achieve such high levels is when norepinephrine is released from postganglionic sympathetic nerve fibers, NOT when it (nor OR epi) is systematically released from the adrenal medulla.
Alpha 2: ? Book doesn’t say.
Beta 1: Reacts equally well to norepinephrine from postganglionic sympathetic nerve fibers, and from epinephrine from nerve fibers.
Beta 2: Preferentially activated by epinephrine. Therefore, epi released from adrenal medulla is expected to activate Beta 2, whereas norepinephrine released from sympathetic nerve endings is not.
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What is the mechanism of action for nicotinic receptors?
When Ach binds to BOTH alpha subunits (it has 2 alpha, 1 beta, one delta, and one gamma), the associated ion channel opens, allowing Na+ to flow iN, and K+ to flow out. This depolarizes the membrane.
Where are nicotinic receptors found?
Motor end plate of skeletal muscle, and on all postganglionic neurons of both the SNS and PSNS, AND on chromaffin cells of the adrenal medulla.
What is the coupled enzyme in alpha 1 receptors? After the G protein subunit activates it, what happens to complete its actions?
Phospholipase C.
- ) This enzyme then catalyzes the liberation of IP3 and diacylglycerol from PIP2.
- ) IP3 then causes the release of Ca2+ from intracellular stores in the ER or SR, increasing the intracellular [Ca2+].
- ) Together, the Ca2+ and diacylglycerol activate PROTEIN KINASE C, which phosphorylates proteins.
- ) These phosphorylated proteins execute the final physiologic actions.
Which, if any, sympathetic effector organs are muscarinic receptors found on? Where else?
Sweat glands. Also, heart, GI tract, bladder, bronchioles, and male sex organs.
What are the three (3) mechanisms of action for muscarinic receptors? Be specific and give example for the unusual one!
There are three (3):
- ) Exactly like alpha 1.
- ) Like alpha 2? (inhibit adenylyl cyclase and lower intracellular cAMP).
* **3.) Alter physiologic processes with DIRECT ACTION ON THE G PROTEIN with NO SECOND MESSENGER–> E.G. Muscarinic receptors in the SA node, when activated by Ach, produce activation of a Gi protein (alpha 2 style) and release of the alpha i subunit, WHICH BINDS DIRECTLY TO K+ CHANNELS OF THE SA NODE. When this happens, the K+ channels open and SLOW THE RATE OF DEPOLARIZATION OF THE SA NODE, thus DECREASING THE HEART RATE.
For the following sense receptors, give: Location, what it senses, adaptive speed, and phasic or tonic:
- ) Hair receptor
- ) Merkel’s
- ) Pacinian
- ) Ruffini’s
- ) Meissner’s
- ) Tactile disc
- ) Hair: Hairy skin. Senses velocity, direction. Rapid, PHASIC.
- ) Merkel’s: Non-hairy skin. Senses vertical indentation. Slow, TONIC. VERY SMALL RECEPTIVE FIELD. Response proportional to stimulus.
- ) Pacinian: Subcutaneous, intramuscular. Senses vibration, tapping. Very rapid, PHASIC. VERY LARGE STRUCTURE, opens sodium channels on its own.
- ) Ruffini’s: Hairy skin. Skin stretch, joint rotation. Slow, TONIC. LARGE receptive field.
- ) Meissner’s: Non-hairy skin. Two-point discrimination, tapping, flutter. Rapid, PHASIC.
- ) Tactile disc: Hairy skin. Vertical indentation of skin. Slow, TONIC. VERY SMALL RECEPTIVE FIELD.
Give the structure (i.e. where it crosses) and function (what senses it carries) for 1.) Dorsal column, and 2.) Anterolateral (spinothalamic) system.
- ) Dorsal column: Crosses at brain stem (IPSILATERAL to side of perception). Carries fine touch, vibration, and proprioceptive sensations.
- ) Anterolateral (spinothalamic) system: Crosses at spinal cord (CONTRALATERAL to side of perception). Carries pain and temperature sensation.
What does “lateral inhibition” allow for?
Greater focus and precision of sense. SO YOU CAN TELL WHERE STIMULUS IS COMING FROM.
Blood vessel compliance is highest when…
They hold a large volume at a low pressure. C = V/P
List 4 anatomical structures with high compliance (fill rapidly with little change in pressure).
List 2 with low compliance (fill slowly with LARGE increase in pressure)
High compliance: Lungs, veins, lymphatics, stomach.
Low compliance: Skull, old arteries
What is a consequence of low compliance in blood vessels?
Hypertension
Compliance is the opposite of…
Elasticity: To retain shape and increase pressure
What does high compliance essentially mean in words?
That you can take a lot of volume without a big change in pressure
What happens to pressure and compliance as you go from arteries to veins?
Decreasing pressure, increasing compliance.
What does high compliance do to BP?
Keeps BP low