Medsci205

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Medsci205
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2011-04-21 03:27:41
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physiology
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Medical Physiology
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  1. When your all dizzy from othostatic hypotension, what does your body do to help you feel better?

    A. Sympathetic activity increases. Parasympathetic decreases.

    B. Parasympathtic activity increases. Sympathetic decreases.

    C. Abdominal and leg muscles relax.
    A. Sympathetic activity increases. Parasympathetic decreases.

    • The fall in arterial blood pressure that happens when you get orthostatic hypotension, cause the baroreceptors in the carotid and aortic areas to DECREASE their firing rate. The cardiovascular control centre doesnt get as many signals anymore, so now it's time to increase SNA and decrease PSA. Heart rate, force of contraction, Vasoconstriction, Cardiac Output, TPR the "WHOLE WORKS" INCREASE, hence increasing our initially fallen arterial blood pressure back to normal. What even more amazing, is all this stuff happens within TWO heartbeats! Just shows how quick the neural/extrinsic baroflex pathway
    • is. Just so you know, skeletal muscle pumps also contribute to the recovery from orthostatic hypotension by enhancing venous return when
    • abdominal and leg muscles contract to maintain an upright position.
  2. The foundations for the New York Brooklyn Bridge are made from caissons. These are essentially upside-down containers that are
    submerged, keeping the air pocket inside them. When they reach the bottom, workers can excavate from the bottom while a structure is built ontop to weigh it down. The caissons were air-tight so that air could not escape through the top, allowing water in the bottom. To maintain the air-tight seal, there were air-locks. A system similar to two air-tight doors where at least one had to be shut at all times was in place. The workers would have gone through the first, shut it and gone through the second. Air pumps were employed to make up for any lost pressure. The
    workers often had shifts lasting hours before the sicknesses got worse.
    At the later stages of the excavation, workers returning to the surface became ill with caisson's disease, now known as the bends.
    Earlier in construction, though, workers coming to the surface only felt dizzy and some fainted.
    Which of the following is incorrect?


    A) The worker's parasympathetic/sympathetic nervous system balance would be tilted further towards the parasympathetic while they are in the caisson than if they were in the open air.

    B) Baroreceptors will begin to fire less frequently when the worker first enters the caisson.

    C) By the time the worker has gone home, their EBV has decreased compared to when they were in the caisson. (assume no change in actual blood volume, i.e no fluid intake or
    excretion)

    D) The workers would have quickly learnt to take a slash before heading down for their shifts (sounds like a joke, but take another look).

    E. When immediately entering the caisson,
    peripheral resistance is increased but not because of nervous input.
    B) Baroreceptors will begin to fire less frequently when the worker first enters the caisson.

    • The air pressure they experienced entering the caisson would have put increased
    • pressure on their extremities, increasing blood pressure and pushing blood into
    • the great veins, increasing EBV. Increased blood pressure would have
    • caused baroreceptors to be more stretched and fire more often.
    • Parasympathetic stimulation would have increased as a result of this.
    • The decrease in ADH release would also have increased diuresis, so
    • workers would have filled their bladders quite quickly


    • The caisson is a high pressure environment.
    • The air pressure is similar to the hydrostatic pressure of the water at
    • the same depth at the bottom of the caisson. This means that as soon as
    • you enter a caisson whose bottom is 20m below the surface, it is like being 20m
    • underwater. When you swim underwater and back up you don't get the bends
    • because you ultimately don't go that deep (without an aqualung). The
    • workers stepped out of that pressure almost instantaneously.
    • The air pressure they experienced entering
    • the caisson would have put increased pressure on their extremities, increasing
    • blood pressure and pushing blood into the great veins, increasing EBV.
    • Increased blood pressure would have caused baroreceptors to be more
    • stretched and fire more often. Parasympathetic stimulation would have
    • increased as a result of this. The decrease in ADH release would also
    • have increased diuresis, so workers would have filled their bladders quite
    • quickly. It is a sad probability that during their long shifts the
    • workers would have learnt this the hard way and their were no toiliting
    • facilities in the caissons.
  3. Gilbert is out running through the forest one
    day when he is distracted by a beautiful parrot in a tree. Before he realises what is happening, he is flat on the ground after tripping over a large branch blocking the trail. Unfortunately for Gilbert, he has landed on a sharp rock which has pierced his leg and created a large gash that is oozing lots of blood.

    Since Gilbert has been taking a physiology
    course at university, he knows that his blood volume will be decreasing and that will cause his blood pressure to drop. However, during lectures Gilbert is constantly distracted by the guy sitting in front of him who plays a cool flight simulator game on his laptop. Gilbert has no idea how his body will cope with the drop in blood pressure and begins to panic. Suddenly, Simon Malpas
    comes running along the trail and rushes to help Gilbert. Which of the following statements could Simon use to explain to Gilbert that he's not going to die from his low pressure?

    A) Don't worryGilbert, the loss in blood volume will cause there to be a rapid increase in the frequency of carotid sinus nerve impulses. This will cause vasoconstriction and decreased heart contractility. Before you know it, your blood pressure will be through the roof.

    B) Well...it's a long story but the baroreceptors in your carotid sinus and aortic arch will sense that there's been a drop in blood pressure and this will cause an increase in parasympathetic nerve output from the brain. This will cause your
    heart rate to sky rocket and your arteries to constrict. Pretty soon you'll be right back at 120/80.

    C) Gilbert, don't fret. Your baroreceptors in your carotid sinus and aortic arch will sense the decrease in blood pressure. The nifty thing is that the frequency of nerve impulses sent to the brain from these receptors will decrease. There will be a big increased sympathetic nerve activity. Soon you'll have vasoconstriction,
    increased heart contractility and increased heart rate all contributing to raising your blood pressure!! You'll be right as rain in no time!

    D) Lucky I ran into you. I'm just the man to tell you all about this! There's no need to worry
    about a silly thing like this. Parasympathetic nerve activity has already kick-started the response and caused a whole lot of vasoconstriction in your arteries. Ventricular preload will drop and then your stroke volume will hit the roof.
    • B) Well...it's a long story but the baroreceptors in your carotid sinus and aortic arch will sense that there's been a drop in blood pressure and this will cause an increase in parasympathetic nerve output from the brain. This will cause your
    • heart rate to sky rocket and your arteries to constrict. Pretty soon you'll be right back at 120/80.



    • Explanation
    • A decrease in blood pressure will cause the baroreceptors in the carotid sinus and aortic arch to sense this as they are stretched less. There is an decrease in carotid sinus and vagus nerve impulses to the brain. That decrease causes an increase in sympathetic nerve activity which causes vasoconstriction. In addition to this heart rate increases and so does the contractility of the heart. These factors all cause the blood pressure
    • to rise.
  4. Which of the following statements is true

    A) The release of ANP decreases flow rate of tubular fluid.

    B) an increase in Na Cl delivery sensed by macula densa causes an increase in Nitric oxide release.

    C) angiotensin 2 vasoconstricts the afferent arteriole to increase the GFR.

    D) vasoconstriction of efferent arteriole increases the GFR.

    E) an increase in filtration fraction means the colloid osmotic pressure of the peritubular capillaries decreases.
    D) vasoconstriction of efferent arteriole increases the GFR.

    ANP relaxes mesangial cells and increases the surface area for filtration. flow rate increases.

    increase in NaCl delivery causes a decrease in NO so vasoconstriction of afferent arteriole will cause GFR to drop

    angiotensin 2 has a more profound vasoconstricting effect on efferent arteriole and will cause increase in GFR (or resist the drop in GFR when arterial pressure drops)

    TRUE, vasoconstriction of efferent arteriole will build up pressure in the glomerulus. GFR will increase.

    an increase in filtration fraction means more fluid is being filtered out into the Bowmans capsule. This means the un-filtered protein leftover in the efferent arteriole (eventually leading to peritubular capillaries) will be more concentrated. proteins increase the colloid osmotic pressure.
  5. One efferent pathway of the baroreflex follows the sympathetic division of the autonomic nervous system. The cell bodies of pre-ganglionic sympathetic neurons are found in:

    A) The paravertabral sympathetic chain.
    B) The intermedio-lateral column of the spinal cord between segents T.1 to L.3
    C) The right atrial wall of the heart
    D) The rostral ventro-lateral medulla
    B) The intermedio-lateral column of the spinal

    Cell bodies of pre-ganglionic sympathetic neurons are found in
    all thoracic segments of the spinal cord and in the first three lumber
    segments of the spinal cord.

    post-ganglionic sympathetic neurons' cell bodies are found in the paravertebral ganglia or "sympathetic chain" or in the prevertebral
    ganglia (between the sympathetic chain and the organ the post-ganglionic neuron innervates).
    (this multiple choice question has been scrambled)
  6. Increasing afterload means....
    A) An increase in Stroke Volume and decreased ESV
    B) Just an increase in SV and no change in ESV
    C) An increase in SV and increase in ESV.
    D) A decrease in SV and an increase in ESV
    E) A decrease in Stroke Volume and decreased ESV.
    D) A decrease in SV and an increase in ESV

    eventually, the blood from the ventricle pushes through the artery openings. Except due to the high pressure from the aorta, the blood ejection from the ventricle is slowed down and less of the
    ventricular blood is able out through the aorta, which means more blood
    than usual will drop back down into the ventricle. Which is why they say, this increased afterload will cause a smaller stroke volume, LESS BLOOD IS PUMPED OUT. aaand because there is more blood left back in the ventricle now, the END SYSTOLIC pressure will INCREASE
    (this multiple choice question has been scrambled)
  7. An increase in baroreceptor firing inhibits activity in which two areas of the medulla?

    A) C1 of the rostral ventrolateral medulla and the cardioacceleratory area.
    B) A1 of the rostral ventrolateral medulla and the cardioinhibitory area.
    C) A1 of the rostral ventrolateral medulla and the cardioacceleratory area.
    D) The cardioacceleratory area and the cardioinhibitory area.
    E) The cardioinhibitory area and the dorsal motor nucleus of the vagus.
    A) C1 of the rostral ventrolateral medulla and the cardioacceleratory area.

    Baroreceptor firing inhibits the action of the C1 area in the rostral venterolateral medulla via the interneurons of its afferent pathway,
    the nucleus tractus solitarii (NTS). Normally the C1 area would produce a tonic output to induce vasoconstriction but with this inhibition vasodilation occurs.Some of these inhibitory neurons of the NTS also project onto another part of the medulla called the cardioacceleratory area.
    Page 558 of Boron explains this much better
    (this multiple choice question has been scrambled)

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