ANAPHY: U8.2 Endocrine System (Endocrine Glands)

WITH MURFGI

Acronym for the 10 Main Regulatory Functions of the Endocrine System

1. Control of Water Balance

2. Regulation of Ion Levels

3. Modulation of Tissue Development

4. Changes in Heart Rate and Blood Pressure

5. Regulation of Metabolism

6. Stimulation of Uterine Contractions & Milk Release

7. Control of Reproductive Functions

8. Control of Food Intake & Digestion

9. Control of Blood Glucose & Other Nutrients

10. Modulation of Immune System Function

10 Main Regulatory Functions of the Endocrine System

satiation

The endocrine system regulates the level of ___ and the breakdown of food into individual nutrients.

Hypothalamus

Regulates the secretory activity of the pituitary gland in response to other hormones, sensory information, and emotions

Pituitary Gland

Connected to the base of the brain, just inferior to the hypothalamus

Infundibulum

A stalk of tissue that connects the pituitary gland to the hypothalamus

Sella Turcica of Sphenoid Bone

Where pituitary gland rests in

1 cm

Diameter of pituitary gland

0.5-1.0 g

Weight of pituitary gland

Posterior Pituitary Gland/Neurohypophysis & Anterior Pituitary Gland/Adenohypophysis

2 Lobes of the Pituitary Gland

Neurohypophysis

Another name for the posterior pituitary gland

Adenohypophysis

Another name for the anterior pituitary gland

Outgrowth of the brain

Forms the infundibulum

Posterior pituitary

Formed by the distal end of the infundibulum

Neurohormones/Neuropeptides

Because the posterior pituitary is a part of the nervous system, its hormones are called ____

Pituitary Diverticulum/Rathke Pouch

The outpocketing of the roof of the embryonic oral cavity that the anterior pituitary develops from

Pars Intermedia

Thin band of tissue of the anterior pituitary that acts as its border with the posterior pituitary

Hypothalamus

Small region of the brain just superior to the pituitary that regulates the pituitary

True

True or false: The hypothalamus differentially regulates the anterior and posterior pituitary

A specialized set of blood vessels

The hypothalamus regulates the anterior pituitary through this

A specialized neural pathway

The hypothalamus regulates the posterior pituitary through this

Neurosecretory neurons whose cells bodies are in the hypothalamus but axons extend through the infundibulum into the posterior pituitary

Produces the neurohormones released from the posterior pituitary

Hypothalamohypophysial Tract

The axons of the neurosecretory neurons that extend from the hypothalamus through the infundibulum into the posterior pituitary form this tract

Hypothalamohypophysial portal system

The specialized set of blood vessels connecting the hypothalamus and anterior pituitary

Releasing Hormones

___ ___ from the hypothalamus stimulate anterior pituitary hormone secretion

Inhibiting Hormones

___ ___ from the hypothalamus decrease secretion of particular anterior pituitary hormones

Growth hormone-releasing hormone (GHRH), Growth hormone-inhibiting hormone (GHIH)/Somatostatin, Thyrotropin-releasing hormone (TRH), Corticotropin-releasing hormone (CRH), Gonadotropin-releasing hormone (GnRH), Prolactin-releasing hormone (PRH), Dopamine (Prolactin-inhibiting hormone, PIH)

7 Hormones of the Hypothalamus

Growth Hormone-Releasing Hormone (GHRH)

Hypothalamic hormone; small peptide that stimulates the secretion of growth hormone from the anterior pituitary gland

Growth Hormone-Inhibiting Hormone (GHIH)/Somatostatin

Hypothalamic hormone; small peptide that inhibits growth hormone secretion from the anterior pituitary gland

Thyrotropin-Releasing Hormone (TRH)

Hypothalamic hormone; small peptide that stimulates the secretion of thyroid-stimulating hormone from the anterior pituitary gland

Corticotropin Releasing Hormone (CRH)

Hypothalamic hormone; peptide that stimulates the secretion of adrenocorticotropic hormone from the anterior pituitary gland

Gonadotropin-Releasing Hormone (GnRH)

Hypothalamic hormone; small peptide that stimulates the secretion of both luteinizing hormone and follicle stimulating hormone from the anterior pituitary gland

Prolactin-Inhibiting Hormone (PIH)/Dopamine

Hypothalamic hormone; inhibits the secretion of prolactin from the anterior pituitary gland

Posterior & Anterior Pituitary Hormones

2 Categories of Hormones Secreted from the Pituitary Gland

Antidiuretic Hormone (ADH) & Oxytocin

2 Posterior Pituitary Hormones

Antidiuretic Hormone (ADH)

Posterior pituitary hormone; water conservation hormone that prevents the output of large amounts of urine (diuresis) and constricts blood vessels and raises blood pressure when large amounts are released

Vasopressin

Alternate name for ADH since it also constricts blood vessels and raises blood pressure when large amounts are released

Hypothalamic neurosecretory neurons in the supraoptic nuclei

What ADH molecules are predominantly synthesized by?

Action potentials in the supraoptic nuclei neurons

What directly stimulates the release of ADH into the blood

Kidney Tubules

What ADH acts on, which are the sites of urine production; promotes the reabsorption of water from these, which reduces urine volume

Alterations in blood osmolality and blood volume

The secretion rate for ADH changes in response to this

Osmolality; osmoreceptors

The ___ of a solution increases as the concentration of solutes in the solution increases. Specialized neurons, called ___, synapse with the ADH neurosecretory neurons in the hypothalamus

Blood osmolality increases —> frequency of action potentials in the osmoreceptors increases —> greater frequency of action potentials in the axons of ADH neurosecretory neurons —> ADH secretion increases

The process of how ADH secretion increases

Blood osmolality decreases —> the action potential frequency in the osmoreceptors and the neurosecretory neurons decreases —> less ADH is secreted from the posterior pituitary gland —> increased volume of water to be eliminated in the form of urine

The process of how ADH secretion decreases

Oxytocin

Posterior pituitary hormone; Reproductive hormone that stimulates labor in pregnant mammals, facilitates the movement of sperm cells through the uterus after sexual intercourse, responsible for milk letdown in breastfeeding women and other lactating mammals

Stimulate labor, movement of sperm cells, milk letdown

3 main functions of oxytocin

Hypothalamic neurosecretory neurons in the paraventricular nuclei

What type of neuron predominantly synthesizes oxytocin?

Uterus & mammary glands

Target tissue of oxytocin

Growth hormone (GH)/Somatotropin, Thyroid-stimulating hormone (TSH), Adrenocorticotropic hormone (ACTH), Lipotropins, B endorphins, Melanocyte-stimulating hormone (MSH), Luteinizing hormone (LH), Follicle-stimulating hormone (FSH), Prolactin

9 Hormones of the Anterior Pituitary Gland

Growth Hormone

Anterior pituitary hormone; Stimulate growth in most tissues, regulates metabolism, regulating blood nutrient levels after a meal and during periods of fasting; increases the movement of amino acids into cells, favors their incorporation into proteins, and slows protein breakdown, increases lipolysis (lipid breakdown) and the release of fatty acids from adipocytes into the blood; increases glucose synthesis by the liver, which releases glucose into the blood

Overall, activates the use of lipids to promote growth and protein synthesis.

1. Tissue growth

2. Metabolism

3. Blood nutrient levels after eating/not eating

4. Movement of amino acids into cells incorporation into proteins

5. Slow protein breakdown, lipolysis

6. Glucose synthesis

6 main functions of growth hormone/somatotropin

Somatotropin

Another name for growth hormone

Pituitary Dwarfism

Hyposecretion of GH leading to reduced growth

Gigantism

Hypersecretion of GH leading to excessive growth

Prolactin

Anterior pituitary hormone; Important in milk production by the mammary glands of lactating females and regulation of the ion composition of blood and immune function

Ovaries and mammary glands

Target tissue of prolactin

Thyroid Stimulating Hormone (TSH)

Anterior pituitary hormone; Stimulates the synthesis and secretion of thyroid hormones from the thyroid gland

Thyrotropin

Another name for Thyroid Stimulating Hormone

glycoprotein dimer

TSH is a ___ ___ consisting of two subunits, a and B, which bind to membrane-bound receptors of the thyroid gland

TRH; Thyroid hormones

___ stimulates TSH secretion, ___ ___ inhibits TSH secretion

Adrenocorticotropic Hormone (ACTH)

Anterior pituitary hormone; Stimulates secretion of the hormone cortisol from the adrenal cortex

Proopiomelanocortin (POMC)

ACTH is one of four smaller molecules derived from a large precursor protein called ___

ACTH, lipotropins, B-endorphins, and melanocyte- stimulating hormone

The 4 smaller molecules derived from proopiomelanocortin (POMC)

Adrenal Cortex

Target tissue of ACTH

Addison disease

Pathological condition in which there is chronic adrenocortical insufficiency leading to the degeneration of the adrenal cortex

Melanocyte-Stimulating Hormone (MSH)

Anterior pituitary hormone; Binds to membrane-bound receptors on skin melanocytes and stimulates increased melanin deposition in the skin

Gonadotropins

Glycoprotein hormones capable of promoting the growth and function of the gonads, the ovaries and testes

Luteinizing Hormone (LH) & Follicle-Stimulating Hormone (FSH)

The two major gonadotropins secreted from the anterior pituitary

Luteinizing Hormone (LH) & Follicle-Stimulating Hormone (FSH)

Anterior pituitary hormones; Both play an important role in regulating reproduction; Secreted into the blood bind to membrane-bound receptors, increase the intracellular synthesis of cAMP through G protein mechanisms, and stimulate the production of gametes-sperm cells in the testes and oocytes in the ovaries; control the production of reproductive hormones-estrogens and progesterone in the ovaries and testosterone in the testes

Luteinizing Hormone (LH)

Anterior pituitary hormone; Ovulation and progesterone production in ovaries; testosterone synthesis and support for sperm cell production in testes

Follicle-Stimulating Hormone (FSH)

Anterior pituitary hormone; Follicle maturation and estrogen secretion in ovaries; sperm cell production in testes

Gonadotropin Releasing Hormone (GnRH)

LH and FSH are released from anterior pituitary cells under the influence of this hypothalamic hormone

Ovaries (F) & Testes (M)

Target tissues of luteinizing hormone

Follicles in ovaries (F) & Seminiferous tubules (M)

Target tissues of follicle-stimulating hormone

Triiodothyronine, Tetraiodothyronine, Calcitonin

3 Hormones of Thyroid Gland

Isthmus

The thyroid gland is composed of two lobes connected by a narrow band of thyroid tissue called the ___

trachea; larynx

The lobes of the thyroid are lateral to the upper portion of the ___ just inferior to the ___

Thyroid Gland; 20g

___ ___ is one of the largest endocrine glands with a weight of ___

Highly vascular

Due to being this, thyroid gland is darker red than surrounding tissues

follicles

The thyroid gland contains numerous ___, which are small spheres whose walls are composed of a single layer of cuboidal epithelial cells

colloid

The center of each thyroid follicle is filled with a gelatinous material called ___.

thyroglobulin

Colloid of the thyroid gland is composed of a high concentration of a protein called ___ which is the precursor to thyroid hormones

Parafollicular Cells

Thyroid gland; cells scattered between the follicles and the cells that make up the walls of the follicle

Calcitonin

Thyroid hormone; What the parafollicular cells secrete, which plays a role in reducing the concentration of calcium in the body fluids when calcium levels become elevated

T3 & T4

Thyroid hormones; Increased metabolic rate; increased protein synthesis; essential for normal growth and maturation

Triiodothyronine

Name for T3

Tetraiodothyronine

Name for T4

Thyroxine

Common name for tetraiodothyronine

T4; T3

Thyroid hormones; ___ is the precursor for ___

80%

Percent of the secretions of the thyroid gland that T4 accounts for

10%

Percent of the secretions of the thyroid gland that T3 accounts for

Bone

Primary target tissue for calcitonin

Decreases osteoclast activity, and lengthens the life span of osteoblasts —> Decreases in blood calcium and phosphate level

Effect of calcitonin

Posterior part of each lobe of the thyroid gland

Location of parathyroid glands

Chief cells & oxyphils

2 cells types that make up parathyroid glands

Chief Cells

Cells of the parathyroid gland that secrete parathyroid hormone

Oxyphils

Cells of the parathyroid gland whose function is unknown

Cords

Densely packed masses that parathyroid glands’ cells are usually organized as, rather than in follicles

Parathyroid Hormone (PTH)

Parathyroid gland hormone; Regulates calcium levels in body fluids: calcium reabsorption within the kidneys, so that less calcium leaves the body in urine; increases the enzymatic formation of active vitamin D in the kidneys

Stimulates osteoclast activity, can cause osteoclasts to increase —> bone reabsorption and the release of calcium and phosphate —> increase in blood calcium levels

Effect of PTH