BIOL1421: Final Review (Chapters 17-19)

17.3 The hypothalamus regulates anterior pituitary hormone secretion of seven important hormones

→ “releasing, tropin'“ hormones: released from hypothalamus, to stimulate secretion of anterior pituitary hormones

(1) ADRENOCORTICOTROPIC HORMONE (ACTH)
-corticotropin-releasing hormone (CRH) secreted from hypothalamus → secretion of ACTH from anterior pituitary → secretion of cortisol, aldosterone, androgens from adrenal cortex (release of SUGAR, SALT, SEX hormones)

-elevated cortisol inhibits secretion of ACTH from anterior pituitary + CRH from hypothalamus

(2) HUMAN GROWTH HORMONE (hGH)
1.) LOW BLOOD GLUCOSE PATHWAY: growth hormone releasing hormone (GHRH) secreted from hypothalamus → secretion of hGH from anterior pituitary → secretion of IGF from liver, muscles + increase in blood glucose

2.) HIGH BLOOD GLUCOSE PATHWAY: growth hormone inhibiting hormone (GHIH) secreted from hypothalamus → stops secretion of hGH from anterior pituitary → stops secretion of IGF from liver, muscles + decrease in blood glucose (returns back to normal)

-IGF stimulates body growth and repair, protein synthesis, and increases blood glucose levels

(3) THYROID-STIMULATING HORMONE (TSH)
-thyropin-releasing hormone (TRH) secreted from hypothalamus → secretion of TSH from anterior pituitary → release of T3 and T4 from thyroid gland

-T3 and T4 regulates metabolism and brain development

(4) FOLLICLE-STIMULATING HORMONE (FSH)
1.) IN FEMALES: gonadotropin-releasing hormone (GnRH) from hypothalamus → secretion of FSH from anterior pituitary → secretion of estrogen from ovaries, for ovarian follicle maturation

2.) IN MALES: gonadotropin-releasing hormone (GnRH) from hypothalamus → secretion of FSH from anterior pituitary → stimulates sperm production from testes

-blood estrogen and testosterone level regulates secretion of FSH from anterior pituitary + GnRH from hypothalamus

17.3 The hypothalamus regulates anterior pituitary hormone secretion of seven important hormones

→ “releasing, tropin'“ hormones: released from hypothalamus, to stimulate secretion of anterior pituitary hormones

(5) LUTEINIZING HORMONE (LH)
1.) IN FEMALES: gonadotropin-releasing hormone (GnRH) from hypothalamus → secretion of LH from anterior pituitary → secretion of progesterone from ovaries, to regulate ovulation

2.) IN MALES: gonadotropin-releasing hormone (GnRH) from hypothalamus → secretion of LH from anterior pituitary → secretion of testosterone from testes

(6) PROLACTIN (PRL)
prolactin-releasing (PRH) secreted from hypothalamus → secretion of PRL from anterior pituitary, which stimulates milk production by mammary glands

1.) POSITIVE FEEDBACK: infant sucking mammary glands for milk → stops secretion of PIH + increases secretion of PRL

2.) EXCESS IN MALES: causes erectile dysfunction

(MELANOCYTE-STIMULATING HORMONE (MSH)
-corticotropin-releasing hormone (CRH) and prolactin-inhibiting hormone (PIH) from hypothalamus → release of MSH from anterior pituitary, which causes darker pigment in skin

17.5 The thyroid gland secretes thyroxine, triiodothyronine, and calcitonin.

Which cells of the thyroid gland secrete T3 and T4? Which secrete calcitonin? Which of these hormones are also called thyroid hormones?

T3 and T4 (thyroxine and triidothyronine)
-also known as thyroid hormones
-produced by follicular cells, which are glandular cells found on thyroid follicles

Calcitonin
-produced by parafollicular hormones
-regulates Ca+ homeostasis

17.5 The thyroid gland secretes thyroxine, triiodothyronine, and calcitonin

How is T3 and T4 synthesized and secreted?

Synthesis and Secretion of T3 and T4
1.) Iodide trapping: thyroid follicular cells trap iodide ions (I-)
2.) Synthesis of thyroglobulin: thyroglobulin synthesized by rough endoplasmic reticulum; then secreted into lumen of follicle where iodide ions are trapped
3.) Oxidation of iodide: oxidation of iodide ions (2I- → I2) converted into iodine molecules
4.) Iodination of tyrosine: iodine molecules bind w/ tyrosine → converted into colloids in lumen of follicle
-attachment of one iodine molecule = T1
-attachment of two iodine molecules = T2
5.) Coupling of T1 and T2: one T1 + one T2 join together = T3; one T2 + one T2 join together = T4; last step of thyroid hormone synthesis

6.) Pinocytosis and digestion of colloid: digestive enzymes in lysosomes break down tyrosine component; separating T3 and T4 molecules
7.) Secretion of thyroid hormone: diffuse through plasma membrane → interstitial fluid → enter bloodstream
8.) Transport in the blood: T3 and T4 travel through bloodstream, attached to transport protein thyroxine-binding globulin (TBG)

17.5 The thyroid gland secretes thyroxine, triiodothyronine, and calcitonin

How is the secretion of T3 and T4 regulated?

POSITIVE FEEDBACK:
low blood levels of T3 or T4 + low metabolic rate → stimulates secretion of TRH from hypothalamus → stimulates secretion of TSH from anterior pituitary → stimulates synthesis, secretion of T3 and T4 (until metabolic rate returns to normal)

NEGATIVE FEEDBACK:
high blood levels of T3 or T4 → inhibits secretion of TRH from hypothalamus → inhibits secretion of TSH from anterior pituitary

17.5 The thyroid gland secretes thyroxine, triidothyronine, and calcitnonin

How is the secretion of calcitonin regulated?

Calcitonin works against osteoclasts, which are cells that break down bone extracellular matrix.

POSITIVE FEEDBACK:
high blood levels of Ca2+ → stimulates secretion of calcitonin (CT) from parafollicular cells (until calcium blood levels return to normal)
-result: accelerates uptake of Ca2+ into bone extracellular matrix

NEGATIVE FEEDBACK:
low blood cells of Ca2+ → inhibits secretion of TRH from hypothalamus → inhibitions secretion of CT from parafollicular cells
-result: accelerates breakdown of Ca2+ in bone extracellular matrix

17.8 The pancreatic islets regulate blood glucose level by secreting glucagon and insulin.

What are pancreatic islets? What two types of cells found be in the pancreatic islets? What hormones do they release?

Pancreatic islets are tiny clusters of endocrine tissue in the pancreas, containing both alpha and beta cells.
-alpha cells secrete the glucagon hormone
-beta cells secrete the insulin hormone

Functions of glucagon and insulin:
1.) Glucagon increases blood glucose level when it is low.
2.) Insulin decreases blood glucose level when it is high.

17.8 The pancreatic islets regulate glucose level by secreting glucagon and insulin.

How is the secretion of glucagon and insulin regulated?

1.) LOW BLOOD GLUCOSE PATHWAY: stimulates secretion of glucagon from alpha cells → glucagon targets liver cells to accelerate breakdown of glycogen + formation of glucose → glucose released into blood, increase in blood glucose level (until blood glucose returns to normal)

2.) HIGH BLOOD GLUCOSE PATHWAY: stimulates secretion of insulin from beta cells → insulin targets body cells to accelerate synthesis of glycogen + accelerate uptake of glucose → glucose enters body cells, decrease in blood glucose level

17.10 The pineal gland, thymus, and other organs also secrete hormones

What hormone does the pineal gland secrete?

The pineal gland secretes the melatonin hormone, which regulates our body’s biological clock for sleeping patterns.
-during sleeping hours, melatonin blood level increases
-during waking hours, melatonin blood level decreases

18.2 Hemopoiesis is the production of formed elements in the blood

What is hemopoiesis?

Hemopoiesis is the formation of blood cells, from hemopoietic stem cells in red bone marrow controlled by hormones.

Steps of hemopoiesis:
1.) Red bone marrow contains pluripotent stem cells, which are cells that further develop into many different types of cells.
2.) Pluripotent cells develop → into myeloid stem cells OR lymphoid stem cells

3a.) Myeloid stem cells differentiate → into precursor cells (blasts) including RBCs, platelets, three kinds of granulocytes + monocyte
3b.) Lymphoid stem cells differentiate → into precursor cells (lymphoblasts) including two kinds of lymphocytes + natural killer cells