Endocrine System
What gland secretes insulin?
Pancreas
What protein carries oxygen in red blood cells?
Hemoglobin
What valve separates the left atrium and left ventricle?
The mitral (bicuspid) valve.
What is cardiac output?
The amount of blood pumped by the heart per minute (HR × SV).
What type of feedback regulates most hormone systems?
Negative Feedback Loop
Why does hyperthyroidism increase heart rate?
Thyroid hormones increase metabolic rate and enhance sympathetic stimulation.
Why does a low hematocrit decrease oxygen delivery?
Because fewer red blood cells are available to carry oxygen.
Why does decreased stroke volume often increase heart rate?
To maintain cardiac output through compensation.
Define hematocrit.
The percentage of blood volume composed of red blood cells.
Why does aldosterone increase blood pressure?
It increases sodium and water reabsorption, increasing blood volume.
If blood glucose drops during fasting, which hormone increases and from what gland?
Glucagon from the pancreas.
A patient with type A blood receives type B blood. What happens?
Agglutination occurs due to anti-B antibodies.
If heart rate is 60 bpm and stroke volume is 90 mL, what is cardiac output?
5,400 mL/min (5.4 L/min).
Define stroke volume.
The amount of blood ejected from a ventricle with each contraction.
A sudden drop in blood pressure activates which receptors first?
Baroreceptors
A patient presents with high ACTH and high cortisol levels. Is this most likely a pituitary problem or an adrenal problem? Explain.
Most likely a pituitary problem (Cushing’s disease). Excess ACTH from the pituitary is stimulating the adrenal cortex to overproduce cortisol.
A patient has low RBC count but normal hemoglobin per cell. What condition is most likely present?
Anemia due to decreased RBC production or blood loss.
A patient has a prolonged PR interval on an ECG. What is occurring physiologically in the heart?
There is delayed conduction through the AV node (first-degree AV block), meaning electrical signals are slowed between the atria and ventricles.
Define negative feedback in endocrine regulation.
A mechanism where the final hormone produced inhibits earlier steps in its own production pathway.
Why would chronic hypertension suppress renin release?
Increased renal perfusion reduces renin secretion through negative feedback.
Why is negative feedback essential in the hypothalamic-pituitary-thyroid axis?
It prevents excessive thyroid hormone production and maintains metabolic stability.
Why is O negative considered the universal donor?
It lacks A, B, and Rh antigens, minimizing risk of agglutination.
Which would have a greater long-term impact on cardiac workload: chronic hypertension or bradycardia? Defend your answer.
Chronic hypertension, because increased afterload forces the heart to work harder continuously, leading to hypertrophy.
Define endocrine signaling and explain how it differs from paracrine signaling.
Endocrine signaling involves hormones released into the bloodstream to act on distant target cells.
Paracrine signaling involves chemical messengers that act locally on nearby cells without entering systemic circulation.
Why can chronic activation of the sympathetic nervous system contribute to long-term hypertension?
Chronic sympathetic stimulation causes persistent vasoconstriction and increased heart workload, which elevates peripheral resistance and blood pressure over time. This disrupts normal homeostatic balance.