A&P Chapter 17 - Endocrine System

Mechanism of Hormone Action

Endocrine glands secrete chemicals (hormones) into blood

Hormone Functions

Communication and control but a slower, longer-lasting type of control than that provided by nerve impulses

Target Cells

Cells acted on by hormones

Target Organs

Organs containing target cells

Endocrine Glands

Ductless glands that produce and release hormones to the blood through diffusion

Which glands are strictly Endocrine glands?

Pituitary, thyroid, parathyroid, adrenal, pineal, and thymus

What organs have Endocrine and Hormone production?

Pancreas, gonads, hypothalamus

Two Major Control Systems of Body Functions

1. Nervous System

2. Hormonal/Endocrine System

Endocrine System Function

Primarily controls the different metabolic functions of the body

Results may take seconds or years

Two Types of Hormones

1. Water-Soluble Hormones

2. Lipid-Soluble Hormones

Water-Soluble Hormones

Nonsteroid hormones (first messengers) bind to receptors on target cell membrane, triggering second messengers to affect cell activities

Water-Soluble Hormone Examples

Amine hormones, peptide, and protein hormones

Lipid-Soluble Hormones

Bind to receptors within target cell nucleus and influence cell activity by acting on DNA

Lipid-Soluble Hormone Examples

Steroid hormones, and thyroid hormones

What are Steroid Hormones secreted by?

Adrenal cortex, ovaries, testes, and placenta

Regulation of Hormone Secretion

Hormone secretion is controlled by homeostatic feedback

-Negative Feedback

-Positive Feedback

Negative Feedback

Mechanisms that reverse direction of a change in a physiological system

Positive Feedback

Mechanisms that amplify physiological changes

Uncommon

Pituitary Gland (Hypophysis)

"Master" Gland

Infundibulum

2 Lobes

Infundibulum

Stalk connecting the pituitary gland to the hypothalamus

Two Lobes of Pituitary Gland

1. Anterior Pituitary

2. Posterior Pituitary

Anterior Pituitary

Adenohypophysis

Posterior Pituitary

Neurohypophysis

Six Anterior Pituitary (Adenohypophyseal) Hormones

1. Thyroid Stimulating Hormone (TSH)

2. Growth Hormone (GH or hGH)

3. Corticotrophin (Adrenocorticotrophin or ACTH)

4. Follicle-Stimulating Hormone (FSH)

5. Leutinizing Hormone (LH)

6. Prolactin (PRL)

Thyroid Stimulating Hormone (TSH)

Tropic hormone that stimulates normal development and secretion of the thyroid gland

Growth Hormone (GH or hGH)

Causes growth of all body tissue

Stimulates body cells to increase in size and divide

Gynecomastia

Development of breast tissue through high concentrations of GH

Corticotrophin - Adrenocorticotrophin (ACTH)

Development and maintenance of Adrenal Gland

Stimulates secretion of Adrenal Cortex hormones

Stimulates secretion of Cortisol

Follicle-Stimulating Hormone (FSH)

Stimulates gamete (ova) production

Leutinizing Hormone (LH)

Promotes ovulation in females and production of gonadal hormones

Prolactin (PRL)

Primary function only in pregnant females and females who breast feed

Stimulates development of mammary glands and stimulates milk production

*does not deal with milk release

Homeostatic Imbalance of GH

Gigantism

Acromegaly

Dwarfism

Gigantism

Excessive size

Usually caused by excessive secretion of GH from pituitary gland or tumor in pituitary gland in childhood

Increased cardiovascular disorders like cardiomegaly

Acromegaly

Chronic disease caused by hypersecretion of GH or tumor in pituitary

Enlargement of many parts of skeleton (especially nose, ears, jaws, fingers, and toes)

Excess GH after epiphyseal plate closure

Large hands, width only

Tufting of fingers (club fingers)

Headaches

Dwarfism

Due to hyposecretion of GH

Implies not just extreme shortness, but degree of disproportion

Can have regular-sized babies

Two Posterior Pituitary (Neurohypophysis) Neurohormones

Synthesized by hypothalamus

1. Oxytocin (OT)

2. Antidiuretic Hormone (ADH)

Oxytocin (OT)

Stimulates milk release from breasts

-Parturition, expulsion of fetus by contraction of myometrium (initiates contractions)

-shrinks uterus post-parturition

Has been link to decrease memory

Causes uterine contraction to help move sperm during intercourse

Luteotrophic Hormone

Type of Leutinizing Hormone

Causes milk to be produced

Antidiuretic Hormone (ADH)

Causes renal reabsorption of H2O

-Kidneys pull water out of precursor to urine to maintain homeostasis

Smooth muscle contractor, can increase blood pressure

-can cause vasoconstriction

Vasoconstriction

Makes blood vessels shrink in diameter

Can be caused from ADH

Thyroid Gland Hormones

1. Triiodothyronine (T3)

2. Thyroxines (T4)

3. Calcitonin

Thyroid Gland

Hormones produced by Follicular Cells

Action hormone- gets things going

-Stimulates growth

-Stimulates metabolism (Most potent hormone)

-Stimulates Neuromuscular system

-Increases blood glucose

-Increases calcium

-Increase Cardiovascular system

-Stimulates Integument

-Increase immune response

-Controlled by Hypothalamus and Pituitary

Triiodothyronine (T3)

3 Iodine atoms

Active form

20% of thyroid hormone production

Thyroxine (T4)

4 Iodine atoms

Inactive form

80% of thyroid hormone production

T4 is converted to T3

Calcitonin

Hormone that lowers blood/plasma calcium levels

Produced by Parafollicular cells

Keeps calcium and phosphate in bones

Increase rate at which calcium and phosphate are deposited in bone

Disorders of Thyroid Gland

Simple Goiter or Adenomatous (Nodular) Goiter

Colloidal/Endemic Goiter

Simple Goiter

Enlarged thyroid

May be caused by too little iodine in diet or by other conditions

Most goiters not cancerous

Adenomatous (Nodular) Goiter

Cancerous goiter

Colloidal/Endemic Goiter

Lack of iodine (salt)

Hypothyroidism Disorders

Myxedema

Infantile Hypothyroidism (Cretinism)

Hashimoto's Disease

Myxedema

Condition characterized by swelling of the skin and other tissues, particularly around the eyes and cheeks, caused by extreme deficiency of thyroid hormone

Infantile Hypothyroidism (Cretinism)

Type of mental retardation and bodily malformation caused by severe, uncorrected thyroid deficiency in infancy and early childhood

Hashimoto's Disease

Form of autoimmune thyroiditis that affects women 8x more often than men

Clinically there is an enlarged thyroid and hypothyroidism

Results in symptoms such as fatigue, weakness, weight gain, cold intolerance, and muscle ache

Treatment is life-long replacement therapy with thyroid hormone

Graves Disease

Autoimmune disease of the thyroid gland that results in the overproduction of thyroid hormone (hyperthyroidism)

Symptoms such as nervousness, heat intolerance, heart palpitations, and unexplained weight loss

Exopthalmos

Treated with medication, radiation, or removal of thyroid gland

10x more common in females

Exopthalmos

Bulging of one or more eyeballs

Parathyroid Hormone

Parathormone (PTH)

Produced by chief cells

Increase plasma calcium through bone resorption (destruction of bone)

Increase Vitamin D synthesis essential hormone for growth

Adrenal Glands

Located on top of kidneys

2 Distinct Structures

Two Distinct Structures of Adrenal Glands

1. Adrenal Medulla

2. Adrenal Cortex

Adrenal Medulla

Found in the center of gland (surrounded by adrenal cortex)

Adrenal Cortex

Outside portion, surrounds the medulla

Adrenal Cortex Hormones

Glucocorticoids (Cortisol)

Mineralocorticoids (Aldosterone)

Gonadocorticoids

Glucocorticoids (Cortisol)

Effects on body metabolism, raise sugar level in the blood, and reduce inflammation

(hydrocortisone)

Mineralocorticoids (Aldosterone)

Essential to regulation of electrolyte concentrations of extracellular fluids

It will conserve sodium, secrete potassium

Side effect will increase blood pressure/volume

Gonadocorticoids

Small amounts of male hormones (androgens) secreted by adrenal cortex of both sexes

Disorders of Adrenal Cortex

Addison's Disease

Cushing Syndrome

Addison's Disease

Condition that occurs when the adrenal glands fail to secrete enough corticosteroid hormones

Causes weakness, loss of weight, low blood pressure, gastrointestinal disturbances, and brownish pigmentation of the skin and mucous membranes

Cushing Syndrome

Caused by excessive secretion of the adrenal gland hormone cortisol

Characterized by accumulation of fat around the abdomen and the upper back, and a rounded face ("moon face")

Adrenal Medulla Hormones

Epinephrine (Adrenaline)

Norepinephrine (Noradrenaline)

Epinephrine and Norepinephrine

"Fight or Flight" Hormones

-Increase heart rate

-Convert stored glycogen to glucose

-Constriction of blood vessels

-Dilation of bronchioles

-Increases metabolism

Pancreas Exocrine Function

Produces 75% of all Digestive enzymes

Pancreas Endocrine Function

Produces hormones Glucagon and Insulin

Glucagon

Secreted by alpha cells

Increases blood glucose level by accelerating liver glycogenolysis (conversion of glycogen to glucose)

Insulin

Secreted by beta cells

Decreases blood glucose by accelerating movement of glucose out of blood into cells, which increases glucose metabolism by cells

Diabetes Mellitus

Group of disorders in which there is a defect in the transfer of glucose (sugar) from the bloodstream into cells, leading to abnormally high levels of blood sugar (hyperglycemia)

2 Major forms

Two Major Forms of Diabetes Mellitus

Type I (Insulin Dependent)

Type II (Non-Insulin Dependent)

Type I Diabetes Mellitus

Insulin Dependent

Genetic, autoimmune problem with pancreas

Type II Diabetes Mellitus

Non-Insulin Dependent

Used to be called 'Adult Onset' Diabetes

Comes from obesity and sugar rich diet

Gestational Diabetes

Condition in which the glucose level is elevated and other diabetic symptoms appear during pregnancy in a woman who has not previously been diagnosed with diabetes

Usually resolves at end of gestation but now have an increased risk for developing Type II Diabetes later on

What do Diabetics have an Increase Risk of?

-Coronary heart disease and stroke

-Peripheral neuropathy

-Amputation

-Retinal Detachment

-Abnormal fat metabolism

Symptoms of Diabetes

Polydipsia

Polyuria

Polyphagia

Polydipsia

Excessive thirst

Polyuria

Excessive urination

Polyphagia

Excessive eating

Pineal Gland

Secretes Melatonin

Melatonin

Derived from Serotonin

Increase production in low light levels

Regulates circadian rhythms (the awake, sleep cycles)

Problems with insomnia would occur here

Thymus

Located behind sternum

After puberty fills with fat and atrophy

What does the Thymus Produce?

Thymopoeitin, Thymic Factor, and Thymosin

Thymopoeitin, Thymic Factor, and Thymosin

All essential for development of T-Lymphocytes and Immune Response

Gonads

Ovaries and Testes

Ovaries

Release Estrogen and Progesterone

Testes

Release Testosterone

Estrogen

Initiation of menstrual cycle

Puberty: widening of hips, breast development, increase in fat to muscle ratio

Progesterone

Activated during pregancy

Testosterone

Puberty: facial hair, deepening of voice

Sperm production

Other Hormone Producing Structures

-Atria of Heart

-Skin

-Placenta

-Kidneys

-Adipose Tissue

Atria of Heart - Hormone

Contains specialized cells that secrete Atrial Naturetic Peptide (ANP)

Atrial Naturetic Peptide (ANP)

Decreases blood volume, blood pressure, and blood sodium concentration

Skin - Hormone

Produces Cholecalciferol

Cholecalciferol

Inactive form of Vitamin D3

Placenta - Hormone

Secretes estrogens, progesterone, and Human Chorionic Gonadotrophin (HCG)