Endocrine System

Define endocrine

“internal secretion” - hormones are released into the blood or interstitial fluid and travel to their target

What is the function of the endocrine system?

Produce and secrete hormones that help the body’s tissues communicate with each other

Both the nervous and endocrine systems are used for communication. How do they differ?

Nervous - Signals are sent along neurons and signals travel very fast; chemical signal is a neurotransmitter

Endocrine - signals are sent through the blood and are slower acting compared to nervous system; chemical signal is a hormone

Define hormone

Substance produced and secreted by an endocrine organ that will travel via blood or interstitial fluid to its target cell

Define target cell in the endocrine system

Cells that contains receptor for a specific hormone

What is the structure of a steroid hormone?

A complex ring of carbon and hydrogen atoms that is derived from cholestrol

What type hormone is estrogen classified as?

Steroid

What type of hormone is testosterone classified as?

Steroid

What type of hormone are androgens classified as?

Steroid

What type of hormone is cortisol classified as?

Steroid

What type of hormone is aldosterone classified as?

Steroid

What type of hormone is progesterone classified as?

Steroid

Describe an amine hormone

Nonsteroid hormone derived from the amino acid tyrosine

What type of hormone is epinephrine classified as?

Amine hormone

What type of hormone is norepinephrine classified as?

Amine hormone

Describe a protein hormone

Long chain of amino acids that form a 3D shape

Ex. Growth hormone, FSH

Describe a peptide hormone

A hormone that is a short chain of amino acids

Ex. Prolactin, insulin

Describe a prostaglandin

Lipid-based substances that affect neighboring cells (paracrine substances)

What are two lobes of the pituitary gland?

Anterior and posterior lobes

Which part of the brain controls the pituitary?

Hypothalamus

How does the hypothalamus control the anterior pituitary?

The hypothalamus secrets releasing hormones or inhibitory hormones that control the release of hormones from the anterior pituitary gland.

How does the hypothalamus control the posterior pituitary hormones?

Nerve impulses from the hypothalamus control the release of posterior pituitary hormones

List 7 hormones released from the hypothalamus that control the anterior pituitary

• Growth hormone-releasing hormone (GHRH)

• Somatostatin (SS)

• Prolactin-releasing factor (PRF)

• Prolactin-releasing inhibiting hormone (PIH)

• Thyrotropin-releasing hormone (CRH)

• Gonadotropin-releasing hormone (GnRH)

What is the function of releasing hormones that are secreted by the hypothalamus

They control the release of hormones from the anterior pituitary

List 6 hormones that are produced and secreted by the anterior pituitary

• Growth hormone (GH)

• Prolactin (PRL)

• Thyroid stimulating hormone (TSH)

• Adrenocorticotropin hormone (ACTH)

• Luteinizing hormone (LH)

• Follicle stimulating hormone (FSH)

Growth hormone (GH):

• Where is it secreted from?

• What does it target?

• What is/are its effect(s)?

• Anterior pituitary

• All tissue, but specifically bone and muscle cells

• Stimulates cells to enlarge and divide

Prolactin (PRL):

• Where is it secreted from?

• What does it target?

• What is/are its effect(s)

• Anterior pituitary

• Mammary gland

• Stimulates milk production

Thyroid-stimulating hormone (TSH):

• Where is it secreted from?

• What does it target?

• What is/are its effect(s)

• Anterior pituitary

• Thyroid gland

• Stimulates the release of thyroid hormones (T4 and T3) and can stimulate growth of thyroid gland

Adrenocorticotropic hormone (ACTH):

• Where is it secreted from?

• What does it target?

• What is/are its effect(s)

• Anterior pituitary

• Adrenal cortex (outside layer of adrenal gland)

• Stimulates release of certain hormones, including cortisol and androgens in adrenal cortex

Luteinizing hormone (LH):

• Where is it secreted from?

• What does it target?

• What is/are its effect(s)

• Anterior pituitary

• Ovaries and testes (leydig cells in testes)

• promotes secretion of sex hormone in both sexes and ovulation in females

Follicle-stimulating hormone (FSH):

• Where is it secreted from?

• What does it target?

• What is/are its effect(s)

• Anterior pituitary

• Ovaries and testes

• Development of follicles that house eggs in ovaries; stimulates follicles to secrete estrogen; stimulates production of sperm in testes (Sertoli cells)

List 2 hormones secreted by the posterior pituitary

• Oxytocin

• Antidiuretic hormone (ADH)

Antidiuretic hormone (ADH):

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• Posterior pituitary

• High blood concentration of solutes (high osmolality), decrease in blood volumes/pressure

• Kidneys

• Kidneys reduce water excretion, vasoconstriction can increase blood pressure

Oxytocin:

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• Posterior pituitary

• Stretch of uterine wall/stimulation of breasts

• Uterine smooth muscles and mammary glands

• Uterine contractions and mild secretion (milk “let down”)

Where is the thyroid gland located?

Below the larynx and anterior to the trachea

List 3 hormones secreted by the thyroid gland

• T4 (thyroxine)

• T3

• Calcitonin

What is the difference between T4 and T3

T3 contains (3) iodine atoms, while T4 contains (4) iodine atoms.

T4 is the INACTIVE form of T3 (active form)

T4/T3:

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• Thyroid gland

• Secretion stimulates by TSH

• Most cells

• Increases metabolism/rate of energy consumption

Which elements is important for thyroid function? Why?

Iodine - T4 and T3 hormones incorporate iodine into their structure

Calcitonin:

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• Thyroid glad

• Secretion stimulated by HIGH blood calcium levels

• Bone, kidneys

• DECREASES calcium blood levels by inhibiting osteoclasts, indirectly stimulating osteoblast, increasing calcium excretion in kidneys

Describe the location of the parathyroid glands

4 small glands embedded on posterior side of thyroid gland

What hormone is released by the parathyroid glands?

Parathyroid hormone (PTH)

Parathyroid hormone (PTH):

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• Parathyroid gland

• Secretion stimulated by LOW blood calcium levels

• Bones, kidneys

• INCREASES blood calcium levels by inhibiting osteoblasts but stimulating osteoclasts, and kidneys conserve calcium

Which hormone is in a negative feedback loop with calcitonin?

Parathyroid hormone

What are two hormone that regulate calcium ion homeostasis

Calcitonin and Parathyroid hormone (PTH)

Describe the location of the adrenal glands

The adrenal glands sit on top of the kidneys

Describe the structure of the adrenal glands

• Shaped like pyramid

• The central portion is called the adrenal medulla

• The outer portion is called the adrenal cortex

Which hormones are released from the adrenal medulla?

• Epinephrine (adrenaline)

• Norepinephrine (noradrenaline)

Epinephrine and Norepinephrine:

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• Adrenal medulla

• Secretion stimulated by nerve signals from sympathetic nervous system

• Many organs including heart, blood, vessels, airways, liver

• Fight or flight effects - ex: increased heart rate, dilated airways, liver breaks down glycogen to glucose

List 3 hormones secreted by the adrenal cortex

• Aldosterone (mineralocorticoid)

• Cortisol (glucocorticoid)

• Sex hormones (adrenal androgens)

Aldosterone:

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• Adrenal cortex

• Stimulated by increase in blood potassium levels, but also, secreted in presence of angiotensin II (part of renin-angiotensin system) during low blood volume and blood pressure

• Kidneys conserve sodium and water (by osmosis) and increase potassium excretion

• Increase in blood volume and pressure

Cortisol:

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• Adrenal cortex

• Secretion caused by ACTH from anterior pituitary

• All tissue

• Metabolism - decreases protein synthesis, increases fatty. acid release, converts glucose form noncarb sources

How are adrenal androgens used in the body?

They are thought to supplement sex hormone production.

Androgens can be converted into estrogen and testosterone before puberty and after menopause

List 3 hormones that are produced by the pancreas

• Insulin

• Glucagon

• Somatostatin

List the three types of cells in the pancreatic islets

• Alpha cells

• Beta cells

• Delta cells

What is secreted by the alpha cells in pancreatic islets?

Glucagon

What do pancreatic beta cells secrete?

Insulin

What do pancreatic delta cells secrete?

Somatostatin

Glucagon:

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• Alpha cells of pancreatic islets in pancreas

• In response to LOW blood glucose

• Liver

• Increases blood glucose levels by breaking down glycogen to glucose

  • it can also cause noncarbs to covert to glucose and convert fats into fatty acids and glycerol

Insulin:

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• Beta cells of pancreatic islets in prancreas

• In response to HIGH blood glucose

• Most tissues, liver

  • Decrease blood glucose levels by (1) increasing diffusion of glucose across cell membrane (tell cells to take in glucose) (2) Stimulating liver to convert glucose into glycogen

Somatostatin (from pancreas):

• Where is it secreted from?

• What does it target?

• What is/are its effect(s)

• Secreted from delta cells in pancreatic islets

• Alpha and beta cells in pancreas

• Can inhibit secretion of glucagon and insulin to help regulate carbohydrates

Which hormone is in a negative feedback loop with insulin?

Glucagon

Where is the pineal gland located?

In the brain

What hormone does the pineal gland secrete?

Melatonin

Melatonin:

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• Pineal gland

• Secreted when eyes detect low light levels

• Various tissues

• Helps regulate circadian rhythm and sleep/wake cycles

Where is the thymus gland located?

In the mediastinum above the heart

What does the thymus gland secrete?

Thymosins

Thymosins:

• Where is it secreted from?

• What does it target?

• What is/are its effect(s)

• Thymus gland

• T lymphocytes

• Affect immune response by affecting development and differentiation of T lymphocytes

What hormone is secreted by the testes?

Testosterone

What hormones are secreted by the ovaries?

Estrogens and Progesterone

List three hormones secreted by the placenta

• Estrogens

• Progeesterone

• Human chorionic gonadotropin (hCG)

Testosterone:

• Where is it secreted from?

• What does it target?

• What is/are its effect(s)

• Primarily by testes

• Many tissues including bones, muscles, and vocal cords

• Male secondary sexual characteristics and reproductive functions

Estrogen:

• Where is it secreted from?

• What does it target?

• What is/are its effect(s)

• Mainly ovaries

• Many tissues including the uterus and adipose tissue

• Female secondary characteristics, regulates menstrual cycle

Progesterone:

• Where is it secreted from?

• What does it target?

• What is/are its effect(s)

• Ovaries and placenta

• Uterus

• Pregnancy hormone - maintains uterine wall and prevents contractions

Describe the renin-angiotensin system

Decrease in BP and/or sodium blood concentration causes renin to be released from kidney

Renin reacts with angiotensinogen in the blood that releases angiotensin I

ACE (enzyme) converts angiotensin I to angiotensin II

Angiotensin II stimulates release of aldosterone

Aldosterone stimulates kidneys to conserve sodium and water

BP and sodium ion levels return because negative feedback stops the production of renin

Where is erythropoietin produced?

Kidneys

Erythropoietin (EPO):

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• Kidneys

• Released in response to low oxygen in the blood

• Red bone marrow

• Increases red blood cell production

Atrial natriuretic peptide (ANP):

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• The heart

• Released when atrial wall stretches when blood volume/pressure increases

• Kidneys and adrenal cortex

• Blocks release of renin kidneys and aldosterone from adrenal cortex

RESULT: excretion of sodium ions and water from kidneys to lower blood volume and blood pressure

Gastrin:

• Where is it secreted from?

• What does it target?

• What is/are its effect(s)

• Stomach and upper small intestine; secreation stimulated by parasympathetic nerve fibers

• Gastric glands

• Release of gastric juices

Cholecystokinin (CCK):

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• Upper small intestine

• Stimulated by arrival of fats and proteins to the duodenum

• Gallbladder, Pancreas (main target)

• Release of bile from gallbladder and release of digestive enzyme from pancreas (it also slows down empyting of stomach contents into small intestine)

Secretin:

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• Duodenum

• Stimulated in response to acid in the chyme

• Pancreas

• Release of pancreatic juice that contains bicarbonate ion to neutralize the acid in chyme

Intestinal somatostatin:

• Where is it secreted from? And why?

• What is/are its effect(s)

• Intestinal cells, released in response to fats in small intestine

• Inhibits release of gastric juice

Ghrelin:

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• The stomach (primarily the gastric cells)

• Empty stomach or fasting (low nutrient levels)

• The hypothalamus in the brain

• Stimulates hunger and increases food intake; also promotes growth hormone release

Leptin:

• Where is it secreted from?

• What stimulates it to be secreted?

• What does it target?

• What is/are its effect(s)

• Adipose tissue

• Increased fat storage in the body

• They hypothalamus in the brain

• Reduces appetite and signals satiety (feeling full)