Unit 8: Endocrine System

Exocrine

Ducted

Endocrine

Ductless

Nervous and Endocrine Systems

Act together to coordinate functions of all body systems

Nervous System

• Nerve impulses/neurotransmitters

• Faster responses, briefer effects, acts on specific target

Endocrine System

• Hormone mediator molecule released in one part of body but regulates activity of cells in other parts

• Slower responses, effects last longer, broader influence

Major Endocrine Glands

• Pituitary

• Pineal Glands

• Thyroid

• Parathyroid

• Thymus

• Adrenal

Endocrine and Other Functions

• Hypothalamus

• Pancreas

• Ovaries

• Testes

Produce Hormones But Not Main Function

• Kidneys

• Small intestine

• Heart

• Adipose tissue

“Hormon”

To excite or get moving

Hormone

• Secretion of endocrine cells that alters physiological activity of target cells in body

• Affect specific target tissue with specific receptors

• Receptors constantly synthesized and broken down

Down Regulation

• Decrease in receptors

• If hormone in excess, # target cell receptors decrease

Up Regulation

Increase in receptors

Hormone Types

• Circulating

• Local Hormones

Circulating Hormones

Circulate in blood throughout body

Local Hormones

• Act locally

• Paracrine

• Autocrine

Paracrine

Act on neighbouring cells

Autocrine

Act on same cell that secreted them

Chemical Classes

• Lipid soluble

• Water soluble

Lipid Soluble

• Use transport proteins

• Steroid hormones

• Thyroid hormones

• Nitric oxide (NO)

• Synthesized from cholesterol

Water Soluble

• Circulate in “free form”

• Amines

• Peptides/proteins

• Eicosonoids

• Most hormones belong to this group

  • Amino based hormones

Hormones Targeting Specific Tissues

• Specific cells respond to a hormone have receptor sites for that particular hormone

• “Lock and key mechanism”

Steroid Hormones Reactions

React with receptor sites inside a cell and reactions are slow

Protein Hormones Reactions

React with receptors on surface of cell and reactions are rapid

Hormone Regulation

• Signals from nervous system (neural stimuli)

• Chemical changes in blood

• Other hormones (hormonal stimuli)

• Most hormonal regulation by negative feedback

Neural Stimuli

• Sympathetic NS

• Adrenal medulla

• Epinephrine

Chemical Changes in Blood

• Increases blood glucose

• Pancreas

• Insulin

Hormonal Stimuli

• TSH

• Thyroid gland

• T3 and T4

Positive Feedback

• Contraction

• Release of oxytocin

• Increase force of contractions

Hypothalamus

Major link b/w nervous and endocrine system

Infundibulum

Attachment of pituitary to hypothalamus

Adenohypophysis

Anterior pituitary

Neurohypophysis

Posterior pituitary

Anterior Pituitary

• Human growth hormone

• Thyroid stimulating hormone

• Follicle stimulating hormone

• Luteinizing hormone

• Prolactin

• Adrenocorticotropic hormone

hGH

Human growth hormone

Human Growth Hormone

• Somatostatin

• Stimulates secretion of insulin like growth factors that promote growth

• Protein synthesis

IGFs

Insulin like growth factors

TSH

Thyroid stimulating hormone

Thyroid Stimulating Hormone

• Thyrotropin

• Stimulates synthesis/secretion of thyroid hormones by thyroid

FSH

Follicle stimulating hormone

Follicle Stimulating Hormone

• Stimulate maturation area of ova and production of estrogen

• Stimulate sperm production

LH

Luteinizing hormone

Luteinizing Hormone

• Stimulate ovulation and estrogen and progesterone production

• Stimulate testosterone production

PRL

Prolactin

Prolactin

Promotes milk secretion by mammary glands

ACTH

Adrenocorticotropic hormone

Adrenocorticotropic Hormone

Stimulates glucocorticoid secretion by adrenal cortex

Posterior Pituitary

• Does not synthesize hormones

• Stores/releases hormones made by hypothalamus

• Transported along hypothalamophyseal tract

• Oxytocin and ADH

OT

Oxytocin

Oxytocin

• During and after delivery of baby

• Affects uterus and breasts

ADH

Antidiuretic hormone or vasopressin

Antidiuretic Hormone

• Decreases urine production by causing kidneys to return more water to blood

• Decreases water lost through sweating and constricting of arterioles which increases blood pressure (vasopressin)

Thyroid Gland

• Located inferior to larynx

• 2 lobes connected by isthmus

Isthmus

Connects two thyroid lobes

Thyroid Follicles

Produce thyroid hormones

Thyroid Hormones

• Tetraiodothyronine (T4)

• Triiodothyronine (T3)

T4

Tetraiodothyronine

T3

Triiodothyronine

T4 and T3

Both increase BMR, stimulate protein synthesis, increases use of glucose and fatty acids for ATP production

Parafollicular Cells

• C cells

• Produce Calcitonin

• Lower blood Ca2+ by inhibiting bone resorption

Parathyroid Glands

• Embedded in lobes of thyroid gland (2 pairs)

• Blood Ca2+ level directly controls secretion of both calcitonin and PTH via negative feedback

PTH

Parathyroid hormone or parathormone

Parathyroid Hormone

• Regulator of Ca2+, Mg2+, phosphate ions in blood

• Increases # and activity of osteoclasts

• Elevates bone resorption

Adrenal Glands

• Two structurally and functionally distinct regions

• Adrenal cortex

• Adrenal medulla

Adrenal Cortex

• Mineralocorticoids

• Glucocorticoids

• Gonadocorticoids

Mineralocorticoids

Regulate H2O balance (aldosterone)

Glucocorticoids

Affect glucose homeostasis (cortisol) and inhibit inflammation

Gonadocorticoids

• Adrogens

• Increase female sex drive

Adrenal Medulla

• Intensifies sympathetic responses

• Epinephrine and norepinephrine

Pancreatic Islets

• Exocrine and endocrine gland

• ~99% of cells produce digestive enzymes

• Alpha (A) cells

• Beta (B) cells

Islets of Langerhans

Pancreatic islets

Alpha (A) Cells

• Secrete glucagon

• Raise blood sugar

Beta (B) Cells

• Secrete insulin

• Lower blood sugar

Gonads

Produce gametes and hormones

Ovaries

• Two estrogens and progesterone

• LH and FSH

Two Estrogens in Ovaries

Estradiol and estrone

Progesterone

Uterine lining for pregnancy

LH Hormones

Estrogen and progesterone

FSH Hormones

Just estrogen

LH and FSH in Ovaries

• Regulate menstrual cycle

• Maintain pregnancy

• Prepare mammary glands for lactation

• Maintain female secondary sex characteristics

Inhibin

Inhibits FSH

Relaxin

Produced during pregnancy

Testes

Produce testosterone

Testosterone

• Regulates sperm production

• Maintains male secondary sex characteristics

• Inhibin inhibits FSH

Pineal Gland Location

Attached to roof of 3rd ventricle of brain at midline

Pineal Gland Composition

Masses of neuroglia and pinealocytes

Melatonin

Amine hormone derived from serotonin

Pineal Gland

• Contribute to setting biological clock

• More melatonin in darkness than light

Thymus Location

Behind sternum b/w lungs

Thymus Produces

• Thymosin

• Thymic humoral factor

• Thymic factor

• Thymopoietin

THF

Thymic humoral factor

TF

Thymic factor

Thymus

All hormones produced involved in T cell maturation

Stomach

Produces gastrin

Gastrin

Stimulates release of HCl

Duodenum

Produces intestinal gastrin

Intestinal Gastrin

Inhibits secretion of HCl in stomach

Kidneys

Produces erythropoietin

Erythropoietin

Stimulates bone marrow to produce RBCs

Skin

Produce cholecalciferol (vit D3)

Cholecalciferol

• Vitamin D3

• Stimulates active transport of dietary Ca2+ into bloodstream