PRINCIPLES OF HUMAN PHYSIOLOGY
COMPREHENSIVE PAPER 2026 QUESTIONS
AND SOLUTIONS GRADED A+
◉Steroid ligands. Answer: Lipophilic
All are derived from cholesterol
All steroid messengers (ligands) function as hormones
◉Eicosanoid ligands. Answer: Lipophilic
Intracellular target receptors
Most are derived from arachidonic acid, a cell membrane
phospholipid
Examples: Prostaglandins, leukotrienes
◉Paracrines, autocrines, neurotransmitters, and most cytokines are
transported this way:. Answer: Diffusion through the interstitial
fluid
, ◉Hormones, neurohormones, and some cytokines are transported
this way:. Answer: Bloodborne transport
◉Function of cytokines. Answer: Coordinate the body's defense
against infections
◉Cytokines. Answer: Peptides; usually released from immune cells.
◉Messenger half-life. Answer: Time for a chemical to decrease its
concentration by half
◉These have a relatively short half-life:. Answer: Messengers
dissolved in plasma
◉These have a relatively long half-life:. Answer: Messengers bound
to plasma protein
◉Magnitude of target response depends on 3 factors:. Answer: 1.
concentration of the messenger (ligand)
2. number of receptors per target cell
3. Receptor affinity for the messenger
◉Up-regulation. Answer: target cells form more receptors in
response to the hormone
COMPREHENSIVE PAPER 2026 QUESTIONS
AND SOLUTIONS GRADED A+
◉Steroid ligands. Answer: Lipophilic
All are derived from cholesterol
All steroid messengers (ligands) function as hormones
◉Eicosanoid ligands. Answer: Lipophilic
Intracellular target receptors
Most are derived from arachidonic acid, a cell membrane
phospholipid
Examples: Prostaglandins, leukotrienes
◉Paracrines, autocrines, neurotransmitters, and most cytokines are
transported this way:. Answer: Diffusion through the interstitial
fluid
, ◉Hormones, neurohormones, and some cytokines are transported
this way:. Answer: Bloodborne transport
◉Function of cytokines. Answer: Coordinate the body's defense
against infections
◉Cytokines. Answer: Peptides; usually released from immune cells.
◉Messenger half-life. Answer: Time for a chemical to decrease its
concentration by half
◉These have a relatively short half-life:. Answer: Messengers
dissolved in plasma
◉These have a relatively long half-life:. Answer: Messengers bound
to plasma protein
◉Magnitude of target response depends on 3 factors:. Answer: 1.
concentration of the messenger (ligand)
2. number of receptors per target cell
3. Receptor affinity for the messenger
◉Up-regulation. Answer: target cells form more receptors in
response to the hormone