endocrine system physio s

What is the endocrine system?

A system of ductless glands that secrete hormones into the bloodstream.

What is a hormone?

A chemical messenger that travels through blood to target cells.

What is the difference between endocrine and exocrine glands?

Endocrine glands are ductless and secrete into blood; exocrine glands secrete through ducts.

What are endocrine glands?

Ductless glands that release hormones into blood.

What are exocrine glands?

Glands that release products through ducts.

Name four endocrine glands.

Pituitary, thyroid, adrenal, pineal.

Name four exocrine glands.

Sweat glands, salivary glands, sebaceous glands, mammary glands.

Which organ has both endocrine and exocrine functions?

Pancreas.

What is the endocrine function of the pancreas?

Secretes insulin and glucagon into blood.

What is the exocrine function of the pancreas?

Secretes digestive enzymes into the small intestine.

What is the endocrine function of the ovaries?

Secrete estrogen and progesterone.

What is the exocrine function of the ovaries?

Release oocytes.

What is the endocrine function of the testes?

Produce testosterone.

What is the exocrine function of the testes?

Produce sperm.

How do endocrine glands secrete hormones?

Hormones enter interstitial fluid, diffuse into capillaries, then travel in blood.

What are the steps of hormone secretion?

Synthesis → storage → stimulus → interstitial fluid → capillaries → bloodstream → receptor → response.

What is a neurohormone?

A hormone produced by neurons and released into the bloodstream.

Name two neurohormones.

ADH and oxytocin.

Where are ADH and oxytocin produced?

Hypothalamus.

Where are ADH and oxytocin released?

Posterior pituitary.

Difference between neurotransmitters and neurohormones?

Neurotransmitters act at synapses; neurohormones travel through blood.

What does the endocrine system regulate?

Homeostasis.

Examples of homeostasis regulated by hormones?

Glucose, calcium, blood pressure, growth, metabolism, reproduction.

How are hormones classified?

By chemical structure.

Four hormone classes?

Peptide, glycoprotein, steroid, amine.

Examples of peptide hormones.

Insulin, glucagon, GH, ADH, oxytocin.

Examples of glycoprotein hormones.

TSH, FSH, LH.

Examples of steroid hormones.

Cortisol, aldosterone, testosterone, estrogen, progesterone.

Examples of amine hormones.

Epinephrine, norepinephrine, thyroid hormone, melatonin.

Characteristics of peptide hormones.

Water-soluble, membrane receptors, fast acting.

Characteristics of glycoprotein hormones.

Water-soluble, membrane receptors.

Characteristics of steroid hormones.

Lipid-soluble, intracellular receptors, gene activation.

Characteristics of thyroid hormones.

Amines that act like steroids.

Characteristics of catecholamines.

Water-soluble, membrane receptors.

Which hormones are water-soluble?

Peptides, glycoproteins, catecholamines.

Which hormones are lipid-soluble?

Steroids, thyroid hormones, melatonin.

Which hormones travel freely in plasma?

Water-soluble hormones.

Which hormones require transport proteins?

Lipid-soluble hormones.

Name three hormone transport proteins.

Albumin, thyroxine-binding globulin, corticosteroid-binding globulin.

Why are transport proteins important?

Protect hormones and increase half-life.

Where do peptide hormones bind?

Cell membrane receptors.

Where do steroid hormones bind?

Intracellular receptors.

Where do thyroid hormones bind?

Nuclear receptors.

Can peptide hormones cross the plasma membrane?

No.

Can steroid hormones cross the plasma membrane?

Yes.

What is a receptor?

A protein that recognizes and binds a hormone.

Can a hormone affect a cell without its receptor?

No.

What is the first messenger?

The hormone.

What is the second messenger?

An intracellular signaling molecule.

Most common second messenger?

cAMP.

Hormones that commonly use cAMP?

TSH, ACTH, glucagon, FSH, LH.

Which hormones commonly use IP3/DAG?

Oxytocin and ADH.

Functions of calcium as a second messenger?

Muscle contraction, secretion, gene regulation.

What is up-regulation?

An increase in receptor number.

When does up-regulation occur?

When hormone levels stay low.

What is down-regulation?

A decrease in receptor number.

When does down-regulation occur?

When hormone levels stay high.

Example of down-regulation.

Type 2 diabetes causing insulin resistance.

What determines target cell responsiveness?

Hormone concentration, receptor number, receptor affinity, intracellular signaling.

What is synergism?

Two hormones together produce a greater effect.

Example of synergism.

Glucagon + epinephrine.

What is permissiveness?

One hormone enhances another hormone's effect.

Classic example of permissiveness.

Thyroid hormone increases epinephrine receptor expression.

What is antagonism?

One hormone opposes another.

Example of antagonism.

Insulin vs glucagon.

Which hormone causes permissiveness?

Thyroid hormone.

Memory trick for peptides.

Peptides = Plasma membrane.

Memory trick for steroids.

Steroids = Straight through the membrane.

Memory trick for antagonism.

Against.

Memory trick for synergism.

Same direction.

Memory trick for permissiveness.

Permission.

Which hormones bind membrane receptors?

Peptides, glycoproteins, catecholamines.

Which hormones bind intracellular receptors?

Steroids and thyroid hormones.

True or False: Thyroid hormone is chemically an amine.

True.

True or False: Thyroid hormone behaves like a steroid.

True.

True or False: Melatonin can cross the plasma membrane.

True.

What causes signal amplification?

Second messenger systems.

Where is the thyroid gland located?

Anterior neck, below the larynx and in front of the trachea.

How many lobes does the thyroid have?

Two lobes connected by an isthmus.

What is the functional unit of the thyroid gland?

The thyroid follicle.

What cells produce T3 and T4?

Follicular cells.

What cells produce calcitonin?

Parafollicular (C) cells.

What is the colloid?

The material in the center of thyroid follicles that stores thyroglobulin.

What protein is stored in the colloid?

Thyroglobulin.

What is thyroglobulin?

A storage protein and scaffold for thyroid hormone synthesis.

What amino acid is used to make thyroid hormones?

Tyrosine.

Why is iodine necessary?

It is required to make T3 and T4.

Good dietary sources of iodine?

Seafood, dairy, and iodized salt.

What happens with iodine deficiency?

Decreased T3/T4, increased TSH, and goiter.

What is a goiter?

An enlarged thyroid gland.

What is Step 1 of thyroid hormone synthesis?

Iodide trapping.

How are iodide ions taken into follicular cells?

By the sodium-iodide symporter (NIS).

Does iodide trapping require ATP?

Yes.

What is Step 2 of thyroid hormone synthesis?

Oxidation.

Which enzyme performs oxidation?

Thyroid peroxidase (TPO).

What does TPO do?

Converts iodide into active iodine.

What is Step 3 of thyroid hormone synthesis?

Organification.

What happens during organification?

Iodine binds tyrosine on thyroglobulin.

What does MIT stand for?

Monoiodotyrosine (one iodine).

What does DIT stand for?

Diiodotyrosine (two iodines).