Organ system overviews (endocrine, nervous, immune, circulatory) at the level MCAT tests them.
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- What is the pituitary gland's location, and what are its two main divisions?
- Located at the base of the brain in the sella turcica, below the hypothalamus. Anterior pituitary (adenohypophysis) and posterior pituitary (neurohypophysis).
- Name three hormones released by the anterior pituitary and one function each.
- Growth hormone (growth/metabolism), TSH (stimulates thyroid), and ACTH (stimulates adrenal cortex). Prolactin, FSH, and LH are also anterior pituitary products.
- What two hormones are produced in the hypothalamus and stored/released by the posterior pituitary?
- ADH (antidiuretic hormone, regulates water reabsorption) and oxytocin (stimulates uterine contractions and milk letdown).
- Describe the main effect of thyroid hormone on the body.
- Increases metabolic rate, oxygen consumption, and heat production across most tissues. Essential for growth and development, especially in childhood.
- What is the relationship between parathyroid hormone (PTH) and blood calcium?
- PTH increases blood calcium by promoting calcium reabsorption in the kidney, activating vitamin D, and stimulating osteoclast activity in bone.
- Name the three main hormones produced by the adrenal cortex and their primary effects.
- Cortisol (glucocorticoid, stress response and glucose metabolism), aldosterone (mineralocorticoid, sodium retention and blood pressure), and androgens (weak androgen production).
- What does the adrenal medulla release, and what is its primary effect?
- Releases epinephrine (adrenaline) and norepinephrine, which activate the sympathetic nervous system response: increased heart rate, blood pressure, and glucose mobilization.
- How does insulin regulate blood glucose?
- Insulin lowers blood glucose by promoting glucose uptake into cells, stimulating glycogen synthesis, and inhibiting gluconeogenesis and glycogenolysis.
- How does glucagon regulate blood glucose?
- Glucagon raises blood glucose by stimulating glycogenolysis (breakdown of glycogen) and gluconeogenesis (synthesis of new glucose), primarily in the liver.
- What is a negative feedback loop in the endocrine system, and give one example.
- A response decreases the stimulus that triggered it, maintaining homeostasis. Example: high blood glucose stimulates insulin release, which lowers blood glucose, reducing the stimulus for insulin.
- Describe the hypothalamic-pituitary-thyroid (HPT) axis.
- The hypothalamus releases TRH, which stimulates the anterior pituitary to release TSH, which stimulates the thyroid to release T3 and T4. High T3/T4 inhibits both hypothalamus and pituitary (negative feedback).
- What is the central nervous system (CNS), and what are its two main components?
- The CNS processes and integrates information. Its two components are the brain (cerebrum, cerebellum, brainstem) and spinal cord.
- What is the peripheral nervous system (PNS), and how is it divided?
- The PNS transmits signals between the CNS and the body. It is divided into the somatic nervous system (voluntary control of skeletal muscles) and autonomic nervous system (involuntary control of organs).
- List the main effects of sympathetic nervous system activation.
- Increased heart rate, increased blood pressure, pupil dilation, decreased digestion, increased respiration, and glucose mobilization. The fight-or-flight response.
- List the main effects of parasympathetic nervous system activation.
- Decreased heart rate, decreased blood pressure, pupil constriction, increased digestion, increased salivation, and increased urination. The rest-and-digest response.