Chapter 18: Endocrine Glands

The functional portions of the pituitary gland are the…

neurohypophysis and adenohypophysis

Which hormone is sometimes given to women to induce labor?

oxytocin

What role does oxytocin play in lactation?

ejection of milk

Oxytocin is responsible for

causing contractions of uterine smooth muscle during labor.

Which gland is located in the sella turcica?

pituitary (hypophysis)

Which of the following will inhibit the secretion of growth hormone?

Growth hormone-inhibiting hormone (GHIH)

Chronic hypersecretion of growth hormone as a child would result in…

gigantism

Which of the following characteristics is associated with hyposecretion of thyroid hormones?

Weight gain

Which of the following is involved in the regulation of thyroid hormone levels?

Thyroid-stimulating hormone from the anterior pituitary

The endocrine glands located on top of the kidneys are the _________ glands.

adrenal

Which of these hormones is NOT secreted by the adrenal cortex?

Norepinephrine

Which of the following glands is both an endocrine gland and an exocrine gland?

Pancreas

A _________ hormone stimulates the secretion of other hormones from the target tissues.

tropic

pituitary gland

• secretes at least nine hormones that regulate numerous body functions and other endocrine glands

• endocrine gland attached to the hypothalamus by the infundibulum; also called hypophysis

posterior pituitary

develops from the floor of the brain and consists of the infundibulum and the neurohypophysis

anterior pituitary

develops from the roof of the mouth

hypothalamus

regulates pituitary gland activity through neurohormones and action potentials

hypothalamohypophysial portal system

connects the hypothalamus and the anterior pituitary

neurohormones

• produced in hypothalamic neurons

• through the portal system, these inhibit or stimulate hormones production in the anterior pituitary

• move down the axons of the tract and are secreted from the posterior pituitary

hypothalamohypophysial tract

connects hypothalamus and posterior pituitary

Growth hormone-releasing hormone (GHRH)

Hormones of the Hypothalamus

• Structure: peptide

• Target Tissue: anterior pituitary cells that secrete growth hormone

• Response: increased growth hormone secretion

Growth hormone-inhibiting hormone (GHIH), or somatostatin

Hormones of the Hypothalamus

• Structure: small peptide

• Target Tissue: anterior pituitary cells that secrete growth hormonr

• Response: decreased growth hormone

Thyrotropin-releasing hormone (TRH)

Hormones of the Hypothalamus

• Structure: small peptide

• Target Tissue: anterior pituitary cells that secrete thyroid-stimulating hormone

• Response: increased thyroid-stimulating hormone secretion

Corticotropin-releasing hormone (CRH)

Hormones of the Hypothalamus

stimulates ACTH release; low blood glucose levels and stress stimulate this hormone’s' secretion

• Structure: peptide

• Target Tissue: anterior pituitary cells that secrete adrenocorticotropic hormone

• Response: increased adrenocorticotropic hormone secretion

Gonadotropin-releasing hormone (GnRH)

Hormones of the Hypothalamus

• Structure: small peptide

• Target Tissue: anterior pituitary cells that secrete luteinizing hormone and follicle-stimulating hormone

• Response: increased secretion of luteinizing hormone and follicle-stimulating hormone

Dopamine (prolactin-inhibiting hormone, PIH)

Hormones of the Hypothalamus

• Structure: amino acid derivative

• Target Tissue: anterior pituitary cells that secrete prolactin

• Response: decreased prolactin secretion

antidiuretic hormone (ADH)

Hormones of the Posterior Pituitary

promotes water retention by the kidneys

• Structure: small peptide

• Target Tissue: kidneys

• Response: increased water reabsorption (less water is lost in the form of urine)

Oxytocin

Hormones of the Posterior Pituitary

promotes uterine contractions during delivery and causes milk letdown in lactating females

• Structure: small peptide

• Target Tissue: uterus; mammary glands

• Response:

GH

Hormones of the Anterior Pituitary

stimulates gorwth in most tissues and regulates metabolism. regulated by GHRH and somatostatin

• Structure: protein

• Target Tissue: most tissues

• Response: increased growth in tissues

Thyroid-stimulating hormone (TSH)

Hormones of the Anterior Pituitary

description

• Structure: glycoprotein

• Target Tissue: thryoid gland

• Response: increased thyroid hormone secretion

Adrenocorticotropic hormone (ACTH)

Hormones of the Anterior Pituitary

stimulates cortisol secretion from the adrenal cortex and increases skin pigmentation

• Structure: peptide

• Target Tissue: adrenal cortex

• Response: increased glucocorticoid hormone secretion

Lipotropins

Hormones of the Anterior Pituitary

cause lipid breakdown

• Structure: peptides

• Target Tissue: adipose tissues

• Response: increased lipid breakdown

β (beta) endorphins

Hormones of the Anterior Pituitary

plays a role in analgesia

• Structure: peptides

• Target Tissue: Brain, but not all target tissues are known

• Response: analgesia in the brain; inhibition of gonadatropin-releasing hormone secretion

Melanocyte-stimulating hormone (MSH)

Hormones of the Anterior Pituitary

increases skin pigmentation

• Structure: peptide

• Target Tissue: melanocytes in the skin

• Response: increase melanin production in melanocytes to make the skin darker in color; memory functions in the CNS

Luteinizing hormone (LH)

Hormones of the Anterior Pituitary

• Structure: glycoprotein

• Target Tissue: ovaries; testes

• Response: ovulation and progesterion production in ovaries; testosterone synthesis and support for sperm cell production in testes

Follicle-stimulating hormone (FSH)

Hormones of the Anterior Pituitary

Structure: glycoprotein

Target Tissue: follicles in ovaries; seminiferous tubules in males

Response: follicle maturation and estrogen secretion in ovaries; sperm cell production in testes

prolactin

Hormones of the Anterior Pituitary

Structure: protein

Target Tissue: ovaries and mammary glands in females

Response: milk production in lactating females

tropic hormones

• many hormones from the anterior pituitary gland are this type of hormone

• stimulate the secretion of other hormones from the target tissues

• control the growth of target tissues

thyroid gland

• one of the largest endocrine glands

• located anterior neck

• composed of two lateral lobes connected by median tissue mass (isthmus)

• synthesizes and secretes three hormones: triiodothyronine, tetraiodothyronine, and calcitonin

Thyroid hormones (T3 & T4) secreted by thyroid follicles

Hormones of the Thyroid and Parathyroid Glands

Structure: amino acid derivative

Target Tissue: most cells of the body

Response: increased metabolic rate; increased protein synthesis; essential for normal growth and maturation

calcitonin secreted by parafollicular cells

Hormones of the Thyroid and Parathyroid Glands

Structure: peptide

Target Tissue: bone

Response: decreased rate of breakdown of bone by osteoclasts; prevention of a large increase in blood Ca2+ levels

parathyroid hormone (PTH)

Hormones of the Thyroid and Parathyroid Glands

increases bone breakdown and blood calcium levels

• Structure: peptide

• Target Tissue: bone, kidneys, small intestine

• Response: increased rate of breakdown of bone by osteoclasts; increased reabsorption of Ca2+ in the kidneys; increased absorption of Ca2+ from the small intestine; increased vitamin D3 synthesis; increase blood Ca2+ levels

mechanism of action and the effects of T₃ and T₄ in the body

• transported in the blood bound to thyroxine-binding globulin as well as other plasma proteins

• bind with nuclear receptor molecules and initiate new protein synthesis

• affect nearly every tissue in the body and increase metabolism in many tissues

• TRH and TSH regulate T3 and T4 secretion

calcitonin

• an increase in blood calcium levels stimulates [term] secretion by parafollicular cells

• decreases blood calcium and phosphate levels by inhibiting osteoclasts

parathyroid glands

four glandular masses embedded in the posterior surface of the thyroid gland

epinephrine (80%); norepinephrine (20%)

Hormones of the Adrenal Medulla

Structure: amino acid derivatives

Target Tissue: heart, blood, vessels, liver, adipose cells

Response: increased cardiac output; increased blood flow to skeletal muscles and the heart; preparation for physical activity

mineralocorticoids (aldosterone)

Hormones of the Adrenal Cortex

acts on the kidneys to increase sodium and to decrease potassium and hydrogen levels in the blood

Structure: steroids

Target Tissue: kidney

Response: increased Na+ reabsorption and K+ and H+ excretion; enhanced water reabsorption

glucocorticoids (cortisol)

Hormones of the Adrenal Cortex

Structure: steroids

Target Tissue: most tissues

Response: increased protein and lipid breakdown; increased glucose production; inhibition of immune response and decreased inflammation

androgens

Hormones of the Adrenal Cortex

Structure: steroids

Target Tissue: many tissues

Response: of minor importance in males; in females, development of some secondary sex characteristics, such as axillary and pubic hair

zona glomerulosa

Outer layer of the adrenal cortex that secretes aldosterone.

zona fasciculata

Middle layer of the adrenal cortex that secretes cortisol.

zona reticularis

Inner layer of the adrenal cortex that secretes androgens and estrogens.

pancreatic islets

• the endocrine portion of the pancreas

• each [term portion] is composed of alpha cells, beta cells, and delta cells, which each secrete their own different hormones

Alpha (α) cells

Hormones of the Pancreas

Hormone: glucagon

Structure: peptide

Target Tissue: primarily liver

Response: increased breakdown of glycogen for release of glucose into the blood; increased production of new glucose

Beta (β) cells

Hormones of the Pancreas

Hormone: insulin

Structure: peptide

Target Tissue: especially liver, skeletal muscle, adipose tissue

Response: increased uptake and use of glucose and amino acids

Delta (ẟ) cells

Hormones of the Pancreas

Hormone: somatostatin

Structure: peptide

Target Tissue: alpha and beta cells (some somatostatin is produced in the hypothalamus)

Response: inhibition of insulin and glucagon secretion

insulin

Hormones of the Pancreas

• target tissue: liver, adipose tissue, muscle, and the satiety center in the hypothalamus

• effects: increases the uptake of glucose and amino acids by cells for energy production

• secretion:

  • increases because of elevated blood glucose levels, an increase in some amino acids, parasympathetic stimulation, and GI hormones

  • decreases because of sympathetic stimulation

glucagon

Hormones of the Pancreas

• target tissue: mainly the liver

• effects: causes breakdown of glycogen and lipids for use as an energy source

• secretion: stimulated by low blood glucose levels, certain amino acids, and sympathetic stimulation

somatostatin

Hormones of the Pancreas

inhibits insulin and glucagon secretion

testosterone

Hormones of the Testes

• Structure: steroid

• Target Tissue: most cells

• Response: aids in spermatogensis, development of genitalia, maintenance of functional reproductive organs, secondary sex characteristics, and sexual behavior

inhibin

Hormones of the Reproductive Organs

• Structure: polypeptide

• Target Tissue: anterior pituitary gland

• Response: inhibits FSH secretion

estrogen

Hormones of the Ovaries

• Structure: steroid

• Target Tissue: most cells

• Response: aids in uterine and mammary gland development and function, maturation of genitalia, secondary sex characteristics, sexual behavior, and menstrual cycle

progesterone

Hormones of the Ovaries

• Structure: steroid

• Target Tissue: most cells

• Response: aids in uterine and mammary gland development and function, maturation of genitalia, secondary sex characteristics, and menstrual cycle

relaxin

Hormones of the Ovaries

• Structure: polypeptide

• Target Tissue: connective tissue cells

• Response: increases the flexibility of connective tissue in the pelvic area, especially the symphysis pubis