ENDOCRINE SYSTEM - PART 2

Renin

secreted by the kidneys; helps regulate BP by increasing angiotensin II and aldosterone production

Glucocorticoids

o Help to provide energy for cells by stimulating the increased use of lipids and proteins
o Secretes cortisol

cortisol

▪ Reduce inflammation and break down proteins and lipids, making them available as energy sources to other tissues

Adrenal Androgens

o Stimulate the development of male secondary sex characteristics
o Secreted by the testes (males)
o Influence sex drive of females

Endocrine part of the pancreas

consist of pancreatic islets (islets of Langerhans)

Pancreatic islets

dispersed throughout the exocrine portion of the pancreas

three cell types of the pancreas

▪ Alpha cells
▪ Beta cells
▪ Delta cells
These three^ regulate blood levels of glucose

Alpha cells

secrete glucagon

Beta cells

secrete insulin

Delta cells

secrete somatostatin

Acidosis

blood glucose levels are very low; reduces the pH of body fluids below normal

Insulin

➢ Secreted by beta cells in response to elevated blood glucose levels

Two signals of insulin secretion

o Low blood glucose levels
o Stimulation of the sympathetic nervous system

Major target tissues for insulin

liver, adipose tissue, muscles, satiety center

Satiety center

area of the hypothalamus that controls hunger

Diabetes mellitus

body’s inability to regulate blood glucose levels within the normal range

Type 1 diabetes

too little insulin

Type 2 diabetes

either too few insulin receptors on target cells or defective receptors on target cells

Hyperglycemia

high blood glucose levels

Glucagon

➢ Released from the alpha cells when blood glucose levels are low
➢ Binds to membrane-bound receptors primarily in the liver
o Glycogen stored in the liver is converted to glucose

Somatostatin

➢ Released by delta cells in response to food intake
➢ Inhibits secretion of insulin and glucagon
➢ Inhibits gastric tract activity

Target Tissue: skeletal and cardiac muscle, cartilage, bone, fibroblasts, blood cells, mammary glands

insulin responses: Increases glucose uptake and glycogen synthesis; increases uptake of amino acids
glucagon responses: has little effect

target tissue: liver

insulin responses: increases glycogen synthesis; increases use of glucose for energy
glucagon responses: causes rapid increase in breakdown of glycogen to glucose and release of glucose into the blood; increases the formation of glucose from amino acids and from lipids; increases metabolism of fatty acids

target tissue: adipose cells

insulin responses: Increases glucose uptake, glycogen synthesis, lipid synthesis
glucagon responses: High concentrations cause breakdown of lipids

target tissue: nervous system

insulin responses: Has little effect except to increase glucose uptake in the satiety center
glucagon responses: Has no effect

Testes

secretes testosterone
o Regulates the production of sperm cells and development and maintenance of male reproductive organs and secondary sexual characteristics

Ovaries

secrets estrogen and progesterone
o Control the female reproductive cycle, prepare the mammary glands for lactation, maintain pregnancy
o Development of female reproductive organs and female secondary sexual characteristics

luteinizing hormone

a gonadotropic hormone that is secreted by the anterior pituitary; stimulates ovulation in female mammals and stimulates androgen release in male mammals

follicle-stimulating hormone

a gonadotropic hormone that is secreted by the anterior pituitary and stimulates growth of Graafian follicles in female mammals

Thymus

➢ Upper part of the thoracic cavity
➢ Function of the immune system
➢ Secretes thymosin

thymosin

Aids the development of WBC called T cells

T cells

help protect the body against infection by foreign organisms

Pineal Gland

➢ Small pinecone-shaped structure located superior and posterior to the thalamus of the brain
➢ Produces melatonin

melatonin

o Inhibit the reproductive hypothalamic-releasing hormone, gonadotropin-releasing hormone
▪ Prevents secretion of LH and FSH from the anterior pituitary
o Regulate onset of puberty by acting on the hypothalamus

hormones of the anterior pituitary gland

growth hormone, adrenocorticotropic hormone, thyroid-stimulating hormone, luteinizing hormone, follicle-stimulating hormone, melanocyte-stimulating hormone, prolactin

growth hormone

target tissue: most tissues
response: increases gene expression, breakdown of lipids and release of fatty acids from cells; increase blood glucose levels

thyroid-stimulating hormone

target tissue: thyroid gland
response: increases T3 and T4 secretion

adrenocorticotropic hormone

target tissue: adrenal cortex
response: increases secretion of glucocorticoid hormones such as cortisol; increases skin pigmentation at high concentrations

melanocyte-stimulating hormone

target tissue: melanocytes in skin
response: increases melanin production in melanocytes

luteinizing hormone

target tissue: ovary in females, testis in males
response: promotes ovulation and progesterone production in ovary; promotes synthesis and support for sperm cell production in testis

follicle-stimulating hormone

target tissues: follicles in ovary; seminiferous tubules in testis
response: promotes follicle maturation and estrogen secretion in ovary; promotes sperm cell production in testis

prolactin

target tissues: ovary and mammary glands in females; testis in males
response: stimulates milk production and prolongs progesterone secretion following ovulation and during pregnancy in women; increases sensitivity to LH in males

hormones of the posterior pituitary gland

antidiuretic hormone, oxytocin

antidiuretic hormone

target tissues: kidney
responses: conserves water; constricts blood vessels

oxytocin

target tissues: uterus, mammary glands
responses: increases uterine contractions; increases milk letdown from mammary galnds

hormones of the thyroid gland

thyroxine, triiodothyronine, calcitonin

T3 and T4 hormones

target tissues: most cells of the body
responses: increase metabolic rate, essential for normal process of growth and maturation

calcitonin

target tissues: primarily bone
responses: decreases rate of bone breakdown; prevents large increase in blood Ca2+ levels following a meal

hormones of the parathyroid gland

parathyroid hormone

parathyroid hormone

target tissues: bone, kidney
responses: increases rate of bone breakdown by osteoclasts; increases vitamin D synthesis, essential for maintenance of normal blood Ca levels

hormones of the adrenal medulla

epinephrine and norepinephrine

epinephrine and norepinephrine

target tissues: heart, blood vessels, liver, adipocytes
responses: increases cardiac output; increases blood flow to skeletal muscles and heart; increase of glucose and fatty acids into blood; prepares body for physical activity

hormones of the adrenal cortex

mineralocorticoids (aldosterone), glucocorticoids (cortisol), adrenal androgens

mineralocorticoids (aldosterone)

target tissues: kidneys; to lesser degree, intestine and sweat glands
responses: increase rate of sodium transport in the body; increase rate of potassium excretion; secondarily favor water retention

glucocorticoids (cortisol)

target tissues: most tissues (liver, fat, skeletal muscle, immune tissues)
responses: increases lipid and protein breakdown; increase glucose synthesis from amino acids; increase blood nutrient levels; inhibit inflammation and immune response

adrenal androgens

target tissues: most tissues
responses: insignificant in males; increase female sexual drivel growth of pubic hair and axillary hair