Endocrine System Notes

A &P 2

__Overview of the Endocrine System__

* A system of glands that produce hormones, which are chemical messengers that control:
* Reproduction
* Growth and development
* Rallying the body’s defenses
* Maintenance of homeostasis
*   Regulation of metabolism

Two major types of glands in the human body:

* %%Endocrine glands%%
* Release hormones *directly* into the bloodstream
* Ex: Pituitary gland, ovary, testes, pancreas
* Exocrine glands
* Release chemicals via *ducts*
* Ex: Salivary glands, sweat glands, pancreas

Hormone Action

* Hormones act on target cells, which are the cells that will respond to hormones, by either crossing the target cell’s plasma membrane or by binding to receptors on the cell surface
* Hormones are released to help respond to changes in the environment, and once homeostasis has been restored, hormone release is terminated

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Two major types of hormones:

Steroid hormones and Amino acid-based hormones

Amino acid-based hormones

* Made from amino acids, so they dissolve in water
* Bind to receptors on the target cell’s plasma membrane to trigger secondary messengers within the cell that produce an effect
* Acts quickly, but its effects are short-lived

o  Homeostatic Imbalances (Problems) with Endocrine Glands

Hyposecretion, Primary hyposecretion, Secondary hyposecretion%%, Hypersecretion%%

Hyposecretion

decreased secretion of hormones from endocrine glands

Primary hyposecretion:

defect in gland causes hyposecretion

Secondary hyposecretion:

defect in another gland usually

Hypersecretion:

increased secretion of hormones from endocrine glands

__Pituitary Gland__

Small gland located inferior to the brain and sits in the sella turcica of the sphenoid bone

Two parts of the Pituitary gland:

Anterior and Posterior lobes

Posterior Lobe

* Oxytocin: increases the frequency and force of uterine contractions during labor, and stimulates milk letdown/release from the breast tissue
* Antidiuretic Hormone (ADH/Vasopressin): promotes body water retention/conservation, and increases blood pressure by inhibiting and/or reducing urination and sweating

Pathologies of the pituitary gland

Pituitary Dwarfism, Gigantism, Acromegaly, Diabetes Insipidus,

Pituitary Dwarfism

hyposecretion of growth hormone during childhood and puberty, resulting in reduced stature

Gigantism

hypersecretion of growth hormone during childhood and puberty, resulting in large stature

Acromegaly

hypersecretion of growth hormone during adulthood, resulting in growth of soft tissues

Diabetes Insipidus

 hyposecretion of antidiuretic hormone, resulting in increase frequency and volume of urination, and excessive thirst

__Thyroid Gland__

o   Small butterfly-shaped gland located in the anterior neck

Thyroid Composed of two groups of cells:

Follicular cells, Parafollicular cells

Follicular cells

* lines fluid-filled follicles, and produce two hormones
* Thyroxine (T4) and Triiodothyronine (T3): T4 is converted into T3 within the target cell, which will:
* Stimulates breakdown of glucose and fatty acids for ATP
* Promotes heat generation
* Increases protein synthesis
* Increases cholesterol excretion
* Stimulates body growth

Parafollicular cells

* found between follicles, and produce:
* Calcitonin: *decreases blood calcium* levels by inhibiting osteoclasts, and increasing calcium excretion in the kidneys

Pathologies of the thyroid gland

Hypothyroidism, Congenital/Primary hypothyroidism, Myxedema/Secondary hypothyroidism, Hashimoto’s disease, Hyperthyroidism, Graves disease:

Hypothyroidism

hyposecretion of thyroid hormones, which is treated by synthetic T4

Congenital/Primary hypothyroidism

follicular cell defects at birth, resulting in reduced and/or abnormal development and mental retardation

Myxedema/Secondary hypothyroidism

caused by hyposecretion of TSH from the pituitary gland, resulting in muscle weakness, cold intolerance/sensitivity, and puffiness in face

Hashimoto’s disease

caused by an autoimmune attack by antibodies on the thyroid gland that destroy the thyroid gland

Hyperthyroidism

hypersecretion of T4

Graves disease

* caused by an autoimmune attack by antibodies on the thyroid gland that mimic the effects of TSH, resulting in the excessive release of thyroid hormones
* Symptoms include exophthalmos (bulging eyes) due to increased fat growth behind the eyes, and goiters (increase in thyroid gland size)

__Parathyroid Glands__

o   Four small peas-sized glands located on the posterior aspect of the thyroid gland, which produce Parathyroid hormone

Parathyroid Hormone (PTH): *increases blood calcium levels* by

* Stimulating osteoclasts in bone
* Inhibiting calcium excretion in the kidneys
* Increasing calcium absorption in the intestines

Pathologies of the Parathyroid glands:

* Hypoparathyroidism: hyposecretion of PTH, resulting in low blood calcium levels, and nerve and muscle dysfunction
* Treated with calcium and Vitamin D supplements

__Pancreas__

o   An endocrine and exocrine gland of the endocrine and digestive system

Endocrine function

  Pancreatic Islets (Islets of Langerhans), Alpha cells. Glucagon, Beta cells, Insulin

Pancreatic Islets (Islets of Langerhans)

§  contain two groups of cells that produce hormones:

Alpha cells

produce the hormone *glucagon*

Glucagon

*increases blood glucose levels*, by stimulating the breakdown of glycogen in the liver

Beta cells

produce the hormone *insulin*

Insulin

*decreases blood glucose levels*, by stimulating glucose uptake by body cells

Pathologies of the pancreas

Hypoglycemia:

Hyperglycemia:

Diabetes mellitus:

Symptoms:

Hypoglycemia

lower than normal blood glucose levels

Hyperglycemia

higher than normal blood glucose levels

Diabetes mellitus

* a hyperglycemia (high blood glucose level)
* Symptoms: excessive thirst, frequent urination

Consequences:

* Dehydration, circulatory system failure, kidney damage
* Monitor with frequent blood glucose checks

Type I/Juvenile Diabetes

* a lack of insulin caused by autoimmune destruction of pancreatic beta cells early in life
* Treated with Insulin administration

Type II/Adult-Onset Diabetes

* an intolerance or decreased sensitivity to insulin later in life
* Usually associated with obesity
* Treated with diet and exercise, and medications that stimulate insulin secretion

Gestational Diabetes

* caused by placental hormones that block maternal insulin
* Results in delivery of large babies
* Risk factors for Type II Diabetes

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__Adrenal Glands__

* Small glands located in the abdominal cavity superior to the kidneys
* Divided into two regions, each of which produces their own hormones:

  Cortex

\: outer region of the adrenal glands that produces three groups of hormones

*Mineralocorticoids*

class of steroid hormones that regulate salt and water balances

Aldosterone

* increases Na, water, and blood pressure; decreases K
* Increases sodium reabsorption in the kidneys
* Increases potassium excretion in the kidneys

*Glucocorticoids*

cholesterol-derived steroid hormones synthesized and secreted by the adrenal gland

Cortisol

* Promotes the breakdown of skeletal muscle into amino acids
* Stimulates the conversion of amino acids into glucose
* Stimulates triglyceride breakdown into fatty acids for ATP production
* Anti-inflammatory
* *Androgens*

Testosterone, Estrogen, and Progesterone

* Promotes the development of secondary sex characteristics during puberty
* Height growth
* Hair growth in axillary and pubic regions, as well as on the face
* Muscle growth
* Deepening of voice
* Breath development in females
* Increases sex drive
* Stimulates sperm production in the testes

Medulla

\: inner region of the adrenal gland that produces two hormones

Epinephrine and Norepinephrine

* promotes the “fight or flight” response of the sympathetic nervous system during emergencies
*   Increased heart rate and blood pressure
*    Increased respiratory rate, and dilation of airways
*   Promotes breakdown of glycogen into glucose, and breakdown of fat into fatty acids for ATP production

Pathologies of the adrenal glands:

* Cushing’s syndrome: hypersecretion of ACTH from the pituitary gland that causes hypersecretion of cortisol from the adrenal glands
* Symptoms:
* Muscle breakdown, and weakness
* “Moon faces” (round face)
* Humped back from fat and water retention in the upper back
* Large abdomen from fat redistribution
* Increased blood pressure, and blood glucose
* Treated with cortisol synthesis blockers or surgical removal of part or all of the adrenal or pituitary glands

Addison’s disease

* hyposecretion of cortisol and/or aldosterone, caused by hyposecretion of ACTH from the pituitary gland
* Symptoms:
* Low blood pressure, and blood glucose
* Weight loss
* Muscle weakness
* Dehydration and cardiovascular system dysfunction
* Treated with synthetic glucocorticoids and/or mineralocorticoids

Gonads

* Testes in males produce two hormones
* Testosterone:
* Inhibin
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Testosterone

produces same effects as testosterone from the adrenal glands

Inhibin

inhibits the secretion of FSH from the pituitary gland

Ovaries

in females produces two hormones

Estrogen and Progesterone

produces same effects as estrogen and progesterone from the adrenal glands

__Pineal Gland__

Small gland located in the diencephalon of the brain

Pinealocytes

the cell of the pineal gland responsible for producing the hormone *melatonin*

Melatonin

hormone responsible for regulating the sleep/wake cycle (body clock or circadian rhythm) – makes you sleepy at night

Pathologies of the pineal gland

Seasonal Affective Disorder (SAD):, Jet Lag:

Seasonal Affective Disorder (SAD):

* hypersecretion of melatonin, usually during winter due to decreased daylight hours
* Symptoms: depression, fatigue
* Treated with full-spectrum bright-light therapy

Jet Lag

* hypersecretion of melatonin, usually associated with crossing over several time zones
* Symptoms: fatigue
* Treated with full-spectrum bright-light therapy

__Endocrine Cell in Other Organs:__

Heart, stomach, small intestine, adipose tissue, placenta,

Heart

Atrial natriuretic peptide: decreases Na, water, blood volume, and blood pressure by promoting sodium excretion in the kidneys

Stomach

Gastrin: stimulates gastric glands to secrete components of gastric juice, and increases motility

Small intestine

* Secretin: stimulates the release of bicarbonate from the pancreas
* Cholecystokinin (CCK): stimulates the release of bile from the gallbladder, and the release of enzyme from the pancreas

Adipose tissue

Leptin: suppress the appetite

Placenta

Human chorionic gonadotropin (hCG):

promotes and maintains an early pregnancy

__Three Stages of the Endocrine System’s Response to Stress:__

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* Fight or flight
* Resistance stage


* Exhaustion Stage

Fight or Flight Stage

Sympathetic nervous system increases heart rate and blood pressure, dilates the airways, and increases respiratory rate via epinephrine and norepinephrine

Resistance Stage

Increased energy reserve usage via breakdown of proteins and fat into their monomers via thyroid hormones, and cortisol

Exhaustion Stage

Depletion of energy resources, accompanied by muscle wasting and immune system suppression from overexertion and stress

__Effects of Aging on the Endocrine System__

As cells of the endocrine system (endocrine cells) age, their production of hormones also decreases, leading to difficulty maintaining homeostasis

Gonads

* Ovaries two hormones
* Estrogen and Progesterone

Endocrine glands

* Glands that secrete a chemical signal directly into the bloodstream
* roles in other organ systems
* Ex. hypothalamus, pancreas
* Endocrine cells can also be found in tissues
* Ex. adipose tissue

Exocrine glands

secret chemicals through ducts or tubes

Hormones function by

Released into blood stream and act on target cells and interact at the hormone receptor on cell surface

Steroid Hormones consists of

* Dissolve in fats or lipids, therefore can go through target cell membrane
* Made from cholesterol
* Takes longer to act, but generally effects last longer than non-steroid hormones
* Alter DNA which is why their signal last longer
* slow action times longer affects
* Alter cell activity

Amino acid based hormones function

* Dissolve in water
* Made from small amino acids, peptides, or large proteins
* Bind to hormone receptor on the target cell membrane
* Act faster, but effects are more short-lived than steroid hormones

Nonsteroid hormones can be

* Epinephrine and Norepinephrine
* (ADH) secreted by kidneys to reabsorb water

Pituitary Gland

* Inferior to the brain
* size of a grape
* 9 hormones

Pituitary gland is composed of what two parts

anterior lobe and posterior lobe

Anterior lope 9 hormones list is

hGh, TSH, FSH, LH, PRL, ACTH

MSH

hGh is

Growth Hormone (GH): stimulates tissue and cellular growth

Thyroid Stimulating Hormone (TSH)

stimulates the release of thyroid hormones from the thyroid gland

Follicle Stimulating Hormone (FSH)

\: stimulates sperm and ova/egg development in the gonads (testes and ovaries)

Luteinizing Hormone (LH)

triggers ovulation in the ovaries

Prolactin (PRL)

stimulates the production of milk in the breast tissue

Adrenocorticotropic Hormone (ACTH)

stimulates the release of glucocorticoids like cortisol from the adrenal glands

1\.     Melanocyte Stimulating Hormone (MSH)

stimulates the release of melatonin from the pineal gland

Posterior Pituitary consists of what two hormones.

Oxytocin and Antidiuretic Hormone

Oxytocin

increases the frequency and force of uterine contractions during labor, and stimulates milk letdown/release from the breast tissue

Antidiuretic Hormone (ADH/Vasopressin)

promotes body water retention/conservation, and increases blood pressure by inhibiting and/or reducing urination and sweating

T3/T4 properties

* Promote ~~Protein~~ synthesis,
* breakdown sources of energy sugar/fats, etc.
* Used to generate heat
* excrete cholesterol
* growth