Physiology-Reflex Control Flashcards
What is the purpose of the reflex system?
To maintain blood pressure homeostasis during postural changes, exercise, hemorrhage, sexual activity.
Why do you usually have to pee in the morning?
When you are lying supine, venous blood becomes centralized, your body senses it has too much blood and generates urine.
What happens if you denervate the carotid arteriolar baroreceptors in this dog?
Blood pressure will go from being normal through all activities to having large peaks and valleys during different activities.
Where is the most sensitive pressure sensor in our body?
Carotid sinus, innervated by the sinus nerve. This area is very sensitive to stretch and increases and decreases in pressure.
What portion of the carotid sinus tells the brain about decreases in oxygen, causing increased pumping of blood and increased respiration?
Carotid body. It has an extremely high blood flow. It is a chemoreceptor that senses oxygen, carbon dioxide and pH of the plasma.
What happens to impulses to the brain from the carotid sinus as blood pressure increases?
Impulses are increased as pressure increases within the window of 50mmHg to 200mmHg. Because of the pulsatile nature of our heart, the brain is able to monitor systolic and diastolic pressure changes.
How does carotid massage work?
The sinus nerve is innervating the carotid area you massage. The sinus nerve uses two points of innervation to measure the stretch happening in the walls of the carotid artery to tell the brain to increase or decrease blood pressure. When you massage (stretch) the carotid arteries, the sinus nerve thinks BP is going up and tells the brain to decrease heart rate.
Where is the main blood pressure receptor integrator?
The vasomotor center in the medulla. Mediates vasoconstriction and vasodilation. Has a cardioinhibitor area with vagal output (when stimulated ACh is released and impinges on the SA and AV nodes, slowing the heart). It also decreases sympathetic stimulation when stimulated by the sinus nerve.
What integrating center in the brain causes changes in blood pressure in order to regulate body temperature? Regulate emotional responses (blushing, fainting)?
Hypothalamus=temperature control. Frontal cortex=emotional control.
A 46 year old patient with Cushing’s has heart failure and is in dire need of a new heart. You tell him that he cannot get a heart transplant, but can have a mechanical heart implanted instead. Why is this?
In heart transplant patients, the adrenal gland takes over in regulating blood pressure via NE and EPI secretions because the heart cannot be reinervated. If the patient’s adrenal glands are diseased and not working properly as they are in Cushing’s, they can only have a mechanical heart implanted.
What external organs play a role in blood pressure regulation?
Pituitary (vasopressin/ADH), Kidney (renin) and Adrenal gland (EPI/NE)
What part of the cardiovascular system is sensitive to low pressure stimuli? What signals do they send to the brain and what makes these signals fire?
Atria. They have receptors that fire during the a wave (atrial contraction) and the v wave (atrial filling). Signals increase as blood volume increases.
You sustain a gunshot wound to your left femoral artery and are bleeding out significantly. The baroreceptors in your atria sense there is decreased atrial stretch. How does your body respond to this?
Decreased atrial stretch = decreased baroreceptor stimulus to the brain. Decreased stimulus = activation of sympathetic nervous system (vasoconstriction and cardiac stimulation) and secretion of vasopressin (ADH: vasoconstriction) from the pituitary gland. Both of these actions will work to increase your blood pressure and maintain tissue perfusion.
A 66 year old patient comes to see you complaining of orthopnea and edema in his legs. He has never seen a doctor about this and you decide to order a blood test to see if he has heart failure. What molecules is the heart secreting to try to mitigate the effects caused by heart failure?
Atrial naturetic peptide (ANP) and brain naturetic peptide (BNP). The molecules are basically the opposite of vasopressin and promote excretion of water and sodium through the urine. ANP is secreted by the atria and BNP is secreted by the ventricles.
A patient calls you with a very high runaway heart rate. You tell them to fill the sink with cold water and dip their face in it. How does this decrease their heart rate?
This is the diving reflex initiated by cold and wet stimulus to the trigeminal nerve in our face. The brain elicits a sympathetic outflow causing GI vasoconstriction. The parasympathetic system is also activated, causing bradycardia. This conserves cardiac output by decreasing blood to the digestive system.
