endocrine system

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Endocrine System

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What are endocrine

hormones?

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1. Chemical signals

from one cell to

remote target cells.

2. Chemicals for direct

cell-to-cell

communication.

3. Chemicals that cross

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Messenger Molecules

• _{Cells must communicate with one}

another to coordinate cell processes within tissues and to maintain

homeostasis.

• _{Cell-to-cell communication is carried out}

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Three types of chemical

signals are used for

cell-to-cell

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Four methods of cell-to-cell communication are found in the human body, ranging from

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A muscle cell needs to tell a neighboring

muscle cell to contract. This will be

accomplished by ___ communication:

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1. Direct.

2. Synaptic.

3. Paracrine.

(7)

When blood sugar is high, body cells must

be stimulated to take up sugar. This is

accomplished by ___ communication.

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25% 25% 25% 25%

1. Direct.

2. Synaptic.

3. Paracrine.

(8)

Aspirin helps relieve headaches

because it:

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50% 50%

1. Inhibits

prostaglandin synthesis.

2. Stimulates

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Endocrine hormones

• _{Produced by endocrine (“ductless”) glands and}

secreted into the bloodstream.

• _{Endocrine hormones may affect a wide array of}

target cells to produce multiple effects.

• _{Two types: peptides (small proteins) and}

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Peptide Hormones

• _{Peptide hormones do not enter the cell}

directly. These hormones bind to

receptor proteins in the cell membrane.

• _{When the hormone binds with the}

receptor protein, a secondary messenger molecule initiates the cell response.

• _{Because peptide hormones are water}

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(cytoplasm)

(nucleus)

peptide or amino acid-derived hormone (first messenger) (extracellular fluid) cyclic AMP-synthesizing enzyme cyclic AMP ATP inactive enzyme (second messenger) active enzyme reactant product plasma membrane nuclear envelope receptor

The hormone binds to a receptor on the plasma membrane of a target cell

1

The activated enzymes catalyze specific reactions4

The second messenger activates

other enzymes

3

Hormone–receptor binding activates an enzyme that catalyzes the synthesis of a second messenger,

such as cyclic AMP

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Steroid Hormones

• _{Steroid hormones enter through the cell}

membrane and bind to receptors inside of the target cell.

• _{These hormones may directly stimulate}

transcription of genes to make certain proteins.

• _{Because steroids work by triggering gene}

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gene plasma membrane ribosome hormone receptor steroid hormone mRNA (nucleus) RNA polymerase DNA (cytoplasm) new protein (extracellular fluid)

A steroid hormone diffuses through the

plasma membrane

The hormone binds to a receptor in the nucleus or to

a receptor in the cytoplasm that carries it into the nucleus

The hormone–receptor complex binds to DNA and causes RNA polymerase to bind to a nearby promoter

site for a specific gene

RNA polymerase catalyzes the transcription of DNA into

messenger RNA (mRNA) The mRNA leaves the

nucleus, then attaches to a ribosome and directs the synthesis of a specific protein

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If receptors for a hormone were

blocked, the effect would be the same

as if:

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1. More hormone was

added.

2. No hormone had

been released.

3. More receptors had

been added.

4. The receptors had

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Your doctor injects a hormone as a treatment for a condition, and says it won’t take effect

for at least 24 hours. What kind of hormone was used?

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1. Peptide

2. Steroid

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• _{How do endocrine hormones “know”}

which cells are their target cells?

W O

R K

T O G E T H

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Role of the

Hypothalamus

• _{The thalamus receives sensory}

information, relays some to the hypothalamus.

• _{Hypothalamus monitors the body for}

temperature, pH, other conditions.

• _{Hypothalamus signals pituitary gland if}

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Role of the Pituitary

• _{The pituitary is the “master gland” that signals other}

glands to produce their hormones when needed.

• _{The anterior lobe of the pituitary receives signals from}

the hypothalamus, and responds by sending out the appropriate hormone to other endocrine glands.

• _{The posterior pituitary receives oxytocin or}

(20)

hypothalamus pituitary (anterior lobe) capillary bed endocrine cell blood flow blood flow capillary bed pituitary (posterior lobe) Oxytocin and ADH

(blue triangles) are secreted into the blood

via capillaries in the posterior pituitary

Endocrine cells of the anterior pituitary secrete

hormones (red squares) in response to releasing hormones; the pituitary

hormones enter the bloodstream

Neurosecretory cells of the hypothalamus produce

oxytocin and ADH

Releasing or inhibiting hormones (green circles) are secreted into capillaries feeding the anterior lobe

of the pituitary Neurosecretory cells

of the hypothalamus produce releasing and

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Pituitary Hormones

Pituitary Hormone Functions

Follicle-stimulating hormone

Stimulates egg maturation in the ovary and release of sex hormones.

Lutenizing hormone Stimulates maturation of egg and of the corpus luteum

surrounding the egg, which affects female sex hormones and the menstrual cycle.

Thyroid-stimulating hormone

Stimulates the thyroid to release thyroxine.

Adrenocorticotropic hormone

Causes the adrenal gland to release cortisol.

Melanocyte-stimulating hormone

Stimulates synthesis of skin pigments.

Growth hormone Stimulates growth during infancy and puberty.

Antidiuretic hormone Signals the kidney to conserve more water.

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Endocrine Hormones

Gland Hormones Functions

Thyroid Thyroxine Regulates metabolism

Calcitonin Inhibits release of calcium from the bones

Parathyroids Parathyroid hormone Stimulates the release of calcium from the bones. Islet cells (in

the pancreas)

Insulin Decreases blood sugar by promoting uptake of glucose by cells.

Glucagon Increases blood sugar by stimulating breakdown of glycogen in the liver. Testes Testosterone Regulates sperm cell production and secondary sex characteristics. Ovaries Estrogen Stimulates egg maturation, controls secondary sex characteristics.

Progesterone Prepares the uterus to receive a fertilized egg. Adrenal cortex Epinephrine Stimulates “fight or flight” response.

Adrenal medulla

Glucocorticoids Part of stress response, increase blood glucose levels and decrease immune response.

Aldosterone Regulates sodium content in the blood. Testosterone (in both

sexes)

Adult body form (greater muscle mass), libido.

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• _{Use the table on the last slide to diagnose}

the following endocrine issues:

• _{A patient who feels cold and listless all}

the time.

• _{A patient who is constantly keyed up}

and nervous.

• _{An elderly patient who is having}

chronic trouble falling asleep at night.

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Homeostasis and

Hormones

• _Examples:

• _{Thyroid and temperature control}

• _{Thyroid, Parathyroid, and calcium}

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• _{Knowing the following:}

• _{The thyroid produces thyroxine, which}

increases metabolism.

• _{Thyroid-stimulating hormone is}

released by the pituitary.

• _{Sketch a negative feedback loop that}

controls body temperature regulation.

W O

R K

T O G E T H

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• _{Knowing the following:}

• _{Calcitonin from the thyroid inhibits}

calcium release from the bones.

• _{Parathyroid hormone stimulates}

release of calcium from the bones.

controls blood calcium level.

W O

R K

T O G E T H

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• _{Knowing that:}

• _{Insulin from the pancreas lowers blood}

glucose by stimulating body cells to take up glucose.

• _{Glucagon from the pancreas increases}

blood sugar by stimulating the liver to break down glycogen into glucose.

controls blood sugar.

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• _{Given this patient profile, can you make a}

diagnosis?

• _{Age – 14}

• _{Gender – Male}

• _{Exam: Normal weight, low blood}

pressure

• _{Lab tests: High blood glucose, low}

levels of insulin.

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• _{Now how about this patient?}

• _{Age – 40}

• _{Gender – Male}

• _{Exam: Obese, high blood pressure}

• _{Lab tests: High blood glucose, normal}

levels of insulin.

W O

R K

T O G E T H

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Other hormone roles

• _{Controlling sleep cycles (melatonin)}

• _{Controlling reproductive cycles}

(melatonin, sex hormones)

• _{Growth (growth hormone)}

• _{Responding to stress or emergencies}

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Hormones Everywhere!

• _{Many other organs besides the endocrine}

glands produce hormones.

• _{Kidneys produce several hormones that}

regulate blood pressure, which is essential for kidney function.

• _{The digestive system produces several}

(35)

Low body fat stimulates leptin production,

which stimulates appetite. The mouse is obese because its low leptin levels give it an

enormous appetite. Leptin injections return the mouse’s weight to normal. Humans sometimes

have a leptin issue, too, but the problem is a bad leptin receptor on body cells. Alas, leptin

injections won’t cure that.

The obese mouse on the

left does not produce enough

leptin, a hormone

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Finally…

• _{Summarize the roles of the pituitary and}