Physiology Lecture 23 & 24 – Endocrinology I & II

These flashcards cover key concepts from the lecture notes on endocrinology and neurophysiology, focusing on hormone functions, effects, mechanisms of action potentials, and sensory receptors.

What does the pineal gland produce, and what is its primary function?

The pineal gland produces melatonin, which regulates circadian rhythms.

What hormones are produced by the posterior pituitary gland, and what are their functions?

The posterior pituitary gland produces oxytocin (milk ejection, labor, social behavior) and vasopressin (water reabsorption in kidneys).

Which hormones are produced by the anterior pituitary gland, and what are their respective functions?

The anterior pituitary gland produces prolactin (milk production), growth hormone (GH) (growth factor secretion, growth, metabolism), ACTH (cortisol release), TSH (thyroid hormone synthesis), and gonadotropins (gamete and sex hormone production).

What is the function of calcitonin, produced by the thyroid gland?

Calcitonin lowers the levels of calcium ions in the blood plasma.

What effect does parathyroid hormone (PTH) have on calcium levels in the blood?

PTH increases the levels of calcium ions in the blood plasma.

What are the overall functions of the pancreas?

The pancreas regulates metabolism of glucose and other nutrients, and produces insulin (decreases blood plasma glucose), glucagon (increases blood plasma glucose), and somatostatin (inhibits gastric acid secretion).

What hormones are produced by the adrenal cortex and what are their functions?

The adrenal cortex produces aldosterone (sodium and potassium homeostasis), cortisol (stress responses), and androgens (sex drive in females).

Which hormones are involved in fight-or-flight responses, and where are they produced?

Epinephrine and norepinephrine are produced in the adrenal medulla and are involved in fight-or-flight responses.

What is the primary role of the hypothalamus in relation to the anterior pituitary?

The hypothalamus synthesizes trophic neurohormones that are transported to the anterior pituitary, where they stimulate the secretion of trophic hormones.

What are the two categories of hormones based on their solubility, and how do they differ?

Hydrophilic hormones (peptide hormones and catecholamines) exit cells through exocytosis and are transported dissolved in plasma, while hydrophobic hormones (steroid hormones and thyroid hormones) exit by simple diffusion and are transported attached to carrier proteins.

How does the hypothalamus regulate the posterior pituitary?

The hypothalamus synthesizes neurohormones (oxytocin and vasopressin) that travel down neurons to the posterior pituitary for secretion.

Define hypercortisolism and its causes.

Hypercortisolism is characterized by excessive cortisol levels, caused by adrenal tumors, pituitary tumors, or iatrogenic (physician-induced) effects.

What is the role of the Nodes of Ranvier in the conduction of action potentials?

Nodes of Ranvier are unmyelinated regions of an axon that have high concentrations of sodium and potassium channels, facilitating saltatory conduction of action potentials.

Describe the difference between action potentials and graded potentials in terms of their characteristics.

Action potentials are all-or-nothing events that occur at specific threshold levels and are conducted without loss of strength, while graded potentials vary in magnitude and can be summed.

What happens during hyperpolarization, and what causes it?

Hyperpolarization occurs when the membrane potential becomes more negative than the resting potential, typically due to the efflux of potassium ions.

How do Type II cells of taste buds detect sweet, bitter, and umami sensations?

Type II cells detect sweet, bitter, and umami sensations through G protein-coupled receptors that activate signaling pathways leading to neurotransmitter release.

Contrast the functions of the sympathetic and parasympathetic nervous systems.

The sympathetic nervous system is primarily involved in fight-or-flight responses, while the parasympathetic nervous system supports rest-and-digest functions.

What distinguishes the absolute refractory period from the relative refractory period in terms of action potential generation?

In the absolute refractory period, a second action potential cannot be generated regardless of stimulus strength, due to closed inactivation gates of sodium channels; in the relative refractory period, a stronger-than-normal stimulus is needed to initiate another action potential.