Chapter 42: The Endocrine System

What is a hormone?

A hormone is a biologically active chemical substance secreted from ductless glands that circulates through the bloodstream to act on target cells or organs.

Endocrine System response time

The endocrine system is slow in response, with hormones traveling through the bloodstream, leaving long-lasting effects.

Nervous System response time

The nervous system has a fast response, uses nerve impulses, and has short-term and rapid effects.

Classical Endocrine Signaling

Endocrine cells release hormones that are transported to target cells by the blood.

What supplement can you take to promote the production of T3 and T4 in your body?

Iodine.

Which of the following are NOT secreted by the anterior pituitary?

Antidiuretic Hormone and Oxytocin.

What are the primary differences between the Endocrine and Nervous system?

The endocrine system has a slow response and long-lasting effects, while the nervous system has a fast response and short-term effects.

What are the four major types of cell signaling in the endocrine system?

Classical endocrine, neuroendocrine, paracrine, and autocrine.

What are the four types of hormones and local regulators?

Amine derivatives, peptide hormones, lipid derivatives, and fatty-acid derivatives.

How do hydrophilic hormones elicit cellular responses?

Hydrophilic hormones bind to cell surface receptors and act via activating receptor tyrosine kinase activation.

How do hydrophobic hormones elicit cellular responses?

Hydrophobic hormones can pass through the plasma membrane and bind to intracellular receptors.

What are the major endocrine glands of the human body?

Hypothalamus, pituitary, thyroid, parathyroid, adrenals, pancreas, and gonads.

What are the physiological processes regulated by hormones?

Metabolism, energy production, growth, development, reproductive functions, and responses to stimuli.

What are the amine derivative hormones?

Epinephrine, norepinephrine, dopamine, and thyroxine.

What are the peptide hormones?

Insulin, glucagon, oxytocin, ADH, prolactin, TSH, and LH.

What are the lipid derivative hormones?

Steroid hormones and fatty-acid derivatives (eicosanoids).

What is the negative feedback regulation of hormone action?

A process where increased hormone levels inhibit further hormone secretion.

What is hormone amplification?

A mechanism where a small amount of hormone can produce a large effect.

What are hydrophilic hormones?

Water-soluble hormones that bind to cell surface receptors.

What are hydrophobic hormones?

Lipid-soluble hormones that can pass through the plasma membrane.

What is the role of the hypothalamus?

The hypothalamus is an interlink between the nervous and endocrine systems and plays a significant role in maintaining homeostasis.

What is the hypophyseal portal system?

A system that ensures the connectivity of hypothalamic hormones with the pituitary gland.

What hormones are produced by the hypothalamus and stored in the posterior pituitary?

ADH and oxytocin.

What is the function of the adrenal medulla?

It produces epinephrine and norepinephrine (catecholamines) for the fight or flight response.

What is the function of cortisol?

Cortisol is a glucocorticoid that is used as an anti-inflammatory agent in autoimmune disorders and can suppress the immune system.

What are the exocrine and endocrine parts of the pancreas?

The exocrine part secretes digestive enzymes, while the endocrine part consists of the Islets of Langerhans that produce hormones.

What do α-cells in the pancreas produce?

Glucagon.

What do β-cells in the pancreas produce?

Insulin.

What is the role of the pineal gland?

The pineal gland produces melatonin, which is responsible for maintaining your circadian rhythm.

What is the function of thyroxine (T4) and triiodothyronine (T3)?

They increase the metabolic rate, oxygen consumption, and are essential for growth and development.

What is the function of calcitonin?

Calcitonin is involved in regulating the calcium level in the blood.

What is the function of parathyroid hormone (PTH)?

Parathyroid hormone is involved in calcium homeostasis and increases blood calcium levels.

What is the effect of underproduction of parathyroid hormone?

Muscle twitches and cramps due to decreased calcium.

What is the effect of overproduction of parathyroid hormone?

Brittle bones, osteoporosis, and calcium deposits in soft tissues.

What are mineralocorticoids?

Hormones that regulate electrolyte balance, such as aldosterone.

What is the function of aldosterone?

Aldosterone is responsible for regulating sodium and potassium levels in the body.

What are glucocorticoids?

Metabolic hormones such as cortisol.

What are gonadocorticoids?

Hormones such as testosterone.

What are catecholamines?

Epinephrine and norepinephrine, stress hormones produced by the adrenal medulla.

How is the secretion of glucocorticoids regulated?

By a negative feedback loop involving the hypothalamus, anterior pituitary, and adrenal cortex.

What is the effect of increased cortisol levels?

Increased blood glucose, fat deposition, and protein breakdown, causing weakness and fatigue.

What is the effect of decreased cortisol levels?

Decreased blood glucose and inability to tolerate stress.

What are the anti-inflammatory properties of cortisol?

Suppresses the immune system and the production and activity of inflammatory cytokines

How does aldosterone work at a cellular level?

It binds to a cytoplasmic receptor, changes mRNA transcription, and increases sodium transporter proteins.

What is the role of progesterone?

It prepares and maintains the uterus for the implantation of the embryo and subsequent growth.

What are the exocrine functions of the pancreas?

Production and secretion of digestive enzymes through the pancreatic duct.

What are the endocrine functions of the pancreas?

Secretion of glucagon and insulin from the islets of Langerhans.

What is the function of glucagon?

Glucagon is a hyperglycemic hormone that elevates glucose levels in the blood.

What is the function of insulin?

Insulin is a hypoglycemic hormone that lowers glucose levels in the blood.

What are the chronic effects of diabetes?

Diabetic retinopathy, heart attacks, nerve damage, and kidney damage.

What is the function of the pineal gland?

The pineal gland is part of the epithalamus and produces melatonin.

What are the cells in the nervous system?

Neurons and glial cells.

What is the function of protothoraxotropic hormone (PTTH)?

A neuropeptide hormone secreted by neurosecretory neurons that controls the length of the larval phase through regulation of ecdysone production

What is the function of ecdysone?

A steroid hormone secreted by prothoracic glands that promotes molting in insects.

What is the function of juvenile hormone?

A terpenoid hormone secreted by corpora allata that affects molting in insects (Determines if insect is a large larva or adult)

What is the role of ecdysteroids in crustaceans?

These hormones regulate molting in crustaceans.

What is the difference between exocrine and endocrine glands?

Exocrine glands secrete substances through ducts, while endocrine glands secrete hormones directly into the bloodstream.

What are target cells?

Cells that have receptors for specific hormones.

What is neuroendocrine signaling?

Neurons release neurohormones into the circulatory system to reach target cells.

What is paracrine signaling?

Hormones act on neighboring cells.

What is autocrine signaling?

Hormones act on the same cell that secreted them.

What are tyrosine derivatives?

Epinephrine, norepinephrine, dopamine, and thyroxine.

What are the actions of aldosterone?

It increases sodium reabsorption and potassium secretion.

What is the role of the juxtaglomerular apparatus?

It senses changes in blood pressure and sends information to the hypothalamus.

What are the effects of epinephrine binding to alpha receptors in smooth muscle cells?

Vasoconstriction.

What are the effects of epinephrine binding to beta receptors in cardiac muscle cells?

Increased heart rate.

What is the fight or flight response?

A physiological response to stress mediated by epinephrine and norepinephrine.

How does epinephrine increase energy availability during stress?

It mobilizes glucose and fatty acids by breaking down glycogen and fats.

What is the role of the hypothalamus in the stress response?

It sends signals to the adrenal glands to release epinephrine and norepinephrine.

What is the role of receptors in hormone action?

Hormones must bind to specific receptors to produce an effect on target cells.

What is the role of the hypothalamus?

It is a major neuroendocrine center that integrates nervous and endocrine systems.

What is the pituitary gland also known as?

The hypophysis.

What are the two lobes of the pituitary gland?

The anterior (adenohypophysis) and posterior (neurohypophysis).

What is the role of the posterior pituitary?

It stores and releases hormones produced by the hypothalamus.

What are the two nuclei in the hypothalamus responsible for producing oxytocin and vasopressin?

The supraoptic (ADH) and paraventricular (Oxytocin) nuclei.

What is the hypophyseal portal system?

A vascular link that transports hormones from the hypothalamus to the anterior pituitary.

What are releasing hormones?

Hormones produced by the hypothalamus that stimulate the release of hormones from the anterior pituitary.

What are inhibiting hormones?

Hormones produced by the hypothalamus that inhibit the release of hormones from the anterior pituitary.

What are the hormones of the anterior pituitary?

TSH, ACTH, FSH, LH, prolactin, and growth hormone.

What is the role of melanocyte-stimulating hormone (MSH)?

It increases the production of melanin.

What is the role of endorphins and enkephalins?

They are natural pain relievers.

How does the hypothalamus regulate the posterior pituitary?

By producing and storing hormones (oxytocin and ADH) that are then released by the posterior pituitary.

What is the role of oxytocin in childbirth?

It stimulates uterine contractions.

What is the role of oxytocin in lactation?

It helps in the release of milk from mammary glands.

What is the function of follicle-stimulating hormone (FSH)?

It acts on the ovaries to promote development of the oocyte and also acts on the testes to promote spermatogenesis.

What is the function of luteinizing hormone (LH)?

It induces ovulation and increases testosterone production in males.

What is the function of thyroid-stimulating hormone (TSH)?

It acts on the thyroid to produce thyroxine and triiodothyronine.

What is the function of adrenocorticotropic hormone (ACTH)?

It acts on the adrenal cortex to produce mineralocorticoids and glucocorticoids.

What is the function of prolactin?

It activates mammary glands to produce milk.

What is the function of melanocyte-stimulating hormone (MSH)?

It stimulates melanocytes to produce melanin.

What is the role of the thyroid gland?

The thyroid gland produces thyroxine and calcitonin, which are important for regulating metabolism, and calcium levels.

What is a goiter?

An enlargement of the thyroid gland.

What is cretinism?

A condition resulting from hypothyroidism in children that causes mental retardation and developmental issues.

What is Grave's disease?

An autoimmune disease where antibodies attack the thyroid gland, causing hyperthyroidism.

What is Hashimoto's thyroiditis?

An autoimmune disease that causes hypothyroidism.

What is the role of the parathyroid gland?

The parathyroid gland regulates blood calcium levels.

What is the relationship between calcitonin and parathyroid hormone (PTH)?

Calcitonin lowers blood calcium, while PTH increases blood calcium.

What is the adrenal gland?

A gland located on top of each kidney.

What are the two main parts of the adrenal gland?

The adrenal cortex and the adrenal medulla.

What does the adrenal cortex secrete?

Mineralocorticoids, glucocorticoids, and androgens.