Animal Physiology and Endocrinology
Core concepts
Build a systems view: neural signaling (resting potential, action potential, saltatory conduction, synaptic transmission), muscle contraction (sliding filament, calcium and troponin), circulation (cardiac cycle, pacemaker, blood pressure regulation), respiration (gas exchange, oxygen dissociation curve, Bohr effect), excretion and osmoregulation (nephron segments, countercurrent multiplier, hormones such as ADH and aldosterone), digestion, and thermoregulation. For endocrinology, know hormone classes (peptide, steroid, amine), receptor location (surface versus intracellular), and the hypothalamic-pituitary axes with negative feedback. Key hormones include insulin and glucagon, thyroid hormones, cortisol, adrenaline, and the tropic hormones FSH and LH.
Common traps
Steroid hormones act on intracellular receptors; peptides use surface receptors. The posterior pituitary stores and releases oxytocin and ADH but does not synthesize them - the hypothalamus does. Insulin lowers blood glucose; glucagon raises it. Do not confuse the Bohr effect (shift right with high CO₂, low pH, higher temperature, releasing oxygen) with a leftward shift. ADH increases water reabsorption; aldosterone increases sodium reabsorption.
Worked example
Rule of thumb: follow the feedback loop. If blood calcium falls, parathyroid hormone rises, increasing bone resorption, renal reabsorption, and intestinal absorption via calcitriol, restoring calcium and suppressing PTH. Any question about a hormone's effect should be answered by naming the sensor, the effector, and the direction of the feedback.