Lecture 7: Endocrine System

Organs that secrete hormones → blood stream

• Controls the function of other target organs

• A form of long distance communication

1. Hypothalamus

   1. "head honcho”

   2. Found in brain

2. Pituitary

   1. “2 parts, anterior and posterior”

   2. Also found in the brain

3. Pineal

   1. Found in brain

4. Thyroid and parathyroid

5. Thymus

6. Adrenal gland

7. Pancreas

8. Testes and ovaries

Neural secretory cells and nuclei that connect to the pituitary gland

• Neural secretory cells: neurons that secrete hormones at axon terminal

• “Nuclei = anatomical nuclei = several soma, or cell bodies, in the CNS = nucleus

  • referring to several soma of the secretory cells

Controls release of pituitary hormones

• Secretes: releasing and inhibiting tropic hormones to the anterior pituitary gland

• Tropic hormones: secreted from one gland, causes another gland to secrete another hormone

“Hypothalamus controls the release of hormones in both the posterior pituitary and anterior pituitary. Anterior = uses different tropic hormones and specifically two capillary blood paths”

1. Posterior pituitary

2. Anterior pituitary

*no endocrine (green) cells

• Just axons and singular capillary bed

1. Neurons in hypothalamus synthesizes (produces) and secretes hormones

   1. Supraoptic nucleus (LHS): oxytocin

   2. Paraventricular nucleus (RHS): Anti-diuretic hormone (ADH)

2. Hormones stored in terminal vesicles (in PP, at the tip of axon terminals)

3. When stimulated (by hypothalamus) → vesicles release hormones in capillary beds of PP

• Produced by _______ nucleus in hypothalamus

  • Supraoptic nucleus (LHS)

  • Paraventricular (RHS)

• Stored in terminal vesicles of PP

• Released from PP even though it’s controlled by hypothalamus

Portal System

*Uses Tropic hormone to control AP

1. Stimulated neurosecretory cells release hormones in 1st capillary bed (found in infundibulum)

2. 1st capillary bed → portal vein → 2nd capillary bed (in AP)

3. Hormones exit capillaries → stimulate AP endocrine cells

4. AP endocrine cells secrete hormones in (second) capillaries → body for circulation

1. Posterior

2. Anterior

Neural tissue (axon terminals) from hypothalamus

• “Neural extension of the hypothalamus”

• “Not a true endocrine gland”

1. Anti-diuretic hormone (ADH) or vasopressin

   1. Targets: kidney

   2. Results: Increased water reabsorption, lower urine volume

      1. *Diuretic = makes you urinate more

      2. *Anti-Diuretic = not make you urinate as much

      3. *ADH = causes you to retain fluids vs. turning into urine = less urine

2. Oxytocin

   1. Targets: uterus and breasts

   2. Results:

      1. Uterine contraction

      2. Milk expulsion

         1. getting milk out of the breast, different from milk production

epithelial tissue

1. Prolactin

2. Thyroid stimulating hormone (TSH)

3. Adrenocorticotropic hormone (ACTH)

4. Growth hormone (GH)

5. Luteinizing hormone (LH)

6. Follicle stimulating hormone (FSH)

*Anterior pituitary gland always controlled by the hypothalamus, so another hormone (tropic) was released from hypothalamus that controlled release of ^

Controlled by hypothalamus:

• Prolactin releasing hormone (PRH) (TROPIC)

• Prolactin inhibiting hormone (PIH) or dopamine

Acts on: breasts

Result: milk secretion (production), mammary gland development (of breasts)

Controlled by hypothalamus:

• Thyrotropin releasing hormone (TRH) (TROPIC)

Acts on: thyroid gland

Results: release thyroid hormones → increased metabolism

Controlled by hypothalamus:

• Corticotropin releasing hormone (CRH) (TROPIC)

Acts on: adrenal gland

Results: releases glucocorticoids (cortisol) → stress responses

Controlled by hypothalamus:

• Growth hormone releasing hormone (GHRH) (TROPIC)

• Growth hormone inhibiting hormone (GHIH) or somatostatin

Acts on: Liver and cells

Results:

• Liver: releases insulin-like growth factors (somatomedins)

  • *will then act on cells and cause to grow

• Cells: signals growth and metabolism

*GH is only tropic if it goes to the liver

Controlled by hypothalamus:

• Gonadotropin releasing hormone (GnRH) (TROPIC)

Acts on: ovaries and testes

Results: ovulation, secretion of sex hormones

Controlled by hypothalamus:

• Gonadotropin releasing hormone (GnRH) (TROPIC)

Acts on: ovaries and testes

Results: development of egg and sperm

Epithelial tissue in brain

melatonin

Regulates circadian rhythm

*helps you sleep

*as it gets darker, pineal gland will secrete melatonin

Butterfly structure, ventral (front) surface of trachea

Secretes:

1. Tetraiodothyronine (T4) and Triiodothyronine (T3)

2. Calcitonin

   1. “tone down the Ca2+”

Results:

1. Increase metabolism

2. Lowers Ca2+ levels in blood, deposition in bone

   1. “puts Ca2+ from blood into bone”

4 small glands behind the thyroid

Secretes: parathyroid hormone (PTH)

Results: increase blood Ca2+ levels

• “thyroid produces calcitonin, decreases Ca2+ levels”

  • “parathyroid found on opposite side of the thyroid. PTH will increase Ca2+ levels”

• “PTH breaks down bone. Takes calcium from bone and it causes Ca2+ to be released back into the blood”

Two-lobed gland in front of the heart

Secretes: thymosin

Results: T-cell functional regulation

• “large when you are younger, smaller as you grow”

• “T-cells = type of WBC. Develops and gets training in thymus”

Multilayered glands above kidneys

1. Cortex

2. Medulla

“suprarenal gland”

Outer layer of adrenal gland

Secretes:

1. Mineral corticoids (aldosterone [regulates BP by increasing])

2. Glucocorticoids (cortisol)

3. Androgens (sex hormones that help promote sex drive)

Results:

1. Stimulate Na+ reabsorption, K+ secretion in kidneys

2. Catabolism of fats and proteins, raise blood glucose, stress response

3. Promotes sex drive

Inner core of adrenal gland

Secretes:

• Epinephrine

• Norepinephrine

Results:

• Increased heart rate

• Mobilization of energy sources

Exocrine and endocrine gland below stomach

1. Exocrine cells: acinar cells

   1. “releases things into external environment”

   2. “releases a lot of digestive enzymes”

2. Endocrine cells: Islets of Langerhans

*endocrine = release hormones into blood

Secrete enzymes to GI tract

• digestive enzymes

1. Alpha cells

2. Beta cells

3. Delta cells

4. F cells

Secretes: glucagon

• “…is secreted when glucose is gone to raise blood glucose levels”

Results:

• raises blood glucose

• glycogenolysis

  • “breakdown glycogen”

Secretes:

• insulin

Results:

• lowers blood glucose

• promotes energy storage

  • “stores as glycogen”

Secretes:

• somatostatin

  • “statin stops”

Results:

• Inhibits secretion of pancreatic hormone

  • “alpha and beta cells”

Secretes:

• pancreatic polypeptide

Results:

• Inhibits pancreatic exocrine secretions

  • “stop and work on your acinar cells and stop them from secreting digestive enzymes”

Secretes:

• Androgens

Results:

• Sperm production

• Sex drive

• Secondary sex characteristics (deepening of voice, muscle development)

Secretes:

• Estrogens

Results:

• Follicular development (development of follicle/egg)

• Secondary sex characteristics (widening of hips, development of breast tissue)

A) hypothalamus and posterior pituitary

B) anterior pituitary and posterior pituitary

C) hypothalamus and anterior pituitary

D) pineal gland and the hypothalamus

A) GnRH: Gonadotropin releasing hormone

B) TSH: Thyroid stimulating hormone

C) TRH: Thyrotropin releasing hormone

D) PTH: Parathyroid Hormone

A) Thyroid

B) Adrenal cortex

C) Adrenal medulla

D) Anterior pituitary

A) Beta cells

B) Delta cells

C) F cells

D) Alpha cells

A) originates from the paraventricular nucleus

B) is released by the posterior pituitary

C) is the same as vasopressin

D) all of the above