Endocrinology Quiz 1

Endocrine System

Helps to maintain homeostasis throughout the body along with the Nervous System

Homeostasis

Many different kinds of chemical messengers help to maintain ________ in the body

Homeostasis

Can be defined as the dynamic maintenance of internal environmental balance or equilibrium despite changing internal or external conditions

Endocrinology

• Study of the endocrine system which consists of endocrine glands and tissues that produce “chemical messengers” that regulate the activity of other cells in the body.

• Components of the endocrine system

Endocrine gland

• Ductless gland composed of cells which secrete into the extracellular fluid (interstitial fluid)

• Chemical messengers (hormones) that then diffuse into the blood

Ductless gland

Doesn’t have a tube and instead hormones are released directly into bloodstream

Exocrine gland

What is a gland with a duct called?

Hormone (classical definition)

Chemical messenger produced by an endocrine gland which is secreted into the blood and is carried to a target cell upon which it has a physiological effect

Hormone (recent definition)

Chemical products, released from the cell in very small amounts, that exert a biologic action on a target cell

Endocrine, paracrine, autocrine effect

What are the different classifications on basis of where hormones exert their effects?

Endocrine effect

Chemical messenger secreted into the bloodstream and travels to produce a biologic effect on distant target cells

Paracrine effect

Chemical messenger secreted into the interstitial fluid that exerts its effects in cells near its secretion site

Autocrine effect

Chemical messenger secreted into the interstitial fluid that acts upon the cell that secretes it

Adrenal and pituitary glands

Examples of endocrine glands

Oil and digestive glands

Examples of exocrine glands

Heterocrine gland

What term defines a gland that has both endocrine and exocrine?

Pancreas

Example of a heterocrine gland (because this produces insulin and pancreatic juice)

Neurohormone

A hormone produced by a nerve cell

Vasopressin

Example of a neurohormone

Neuropeptide

A peptidergic neurohormone

Vasopressin

Example of a neuropeptide

Peptide

Has to meet receptor on membrane as its a ______, can’t go through phospholipid bilayer

Pheromone

A chemical messenger released to the exterior of one animal to stimulate a response in another member of the same species

Parahormone

Other cell regulators that do not fit in the well-recognized classes of “hormones”

CO2 and lactic acid

Examples of parahormones

Pheromone and parahormones

Other chemical messengers that are not “true hormones'“

Hilda Bruce (1959)

From who did we first hear about pheromone?

Hilda Bruce

Who, in 1959, put two mice in the same cage, one being a pregnant female of a particular strain and another being a male of a different strain, in which the pregnant female mouse pregnancy got blocked/terminated after smelling an unfamiliar male (pheromones). Also called “Bruce effect.”

Pheromone

A Japanese beetle bag is an example of a ________ as its purpose is to lure male beetles which were attracted to the female ________ or a floral scent.

Japanese beetle bag

This ended up working as it collected male beetles which dropped in the bag preventing them eating on the garden, however also ended up causing an avalanche of beetles coming to the yard when the bag was occupied.

A.A. Berthold (1849)

Who removed the testes of a rooster by severing the nerves to it so that the nervous system has no role to play, then observing that the rooster turned to a Capon. Then conducted an experiment with the Capon by putting in testis graft (still no nerves) and turned back to a rooster.

Capon

A rooster with “no arrogance at all, a mess” as it has no testes

Rooster

A male chicken with combs and is very arrogant. Very attracted to females.

A.A. Berthold

Conclusion for this experimenter (1849): Testes releases “something” into the blood that maintains male behavior and secondary sex characteristics

A.A. Berthold (1849)

Never heard from him after this experiment so he is not referred to the father of endocrinology

Bayliss and Starling (1902)

Who used dogs and severed any nerves to the pancreas and to the small intestine so that the nervous system doesn’t play a role. Then added dilute HCl (simulating the acid coming from the stomach) which resulted in profuse flow of pancreatic juice into the small intestine.

Bayliss and Starling (1902)

Wanted to answer the question of how the pancreas and gallbladder knew when to release to the small intestine after acid chyme comes through.

No response

Critics explained what happened in this experiment by saying that there was increased flow due to absorption of HCl in the pancreas, so Bayliss and Starling took the pancreas with severed nerves and injected HCl directly into the pancreas intravenously, resulting in _________

Secretin

Intestine releases a substance into the blood which flows to the pancreas and causes secretion. What is this substance (hormone) called?

Dilute HCl

Used by Bayliss and Starling to simulate the acid coming from the stomach

A.A. Berthold

The first clear cut and successful experiment bearing on an endocrine gland was that of ______ published in 1849.

Nervous

During A.A. Berthold, the ________ system was considered the major regulating system in an organism

Addison’s disease

First clinical defect on an endocrine gland to be accurately described

Thomas Addison (1855)

First to connect the deterioration of cortex of adrenal gland which caused:

• impaired appetite

• low blood pressure

• extreme muscular weakness

• gastrointestinal upsets

• decolorization of skin

• eventual death

To a fatal clinical syndrome called Addison’s Disease

On top of kidney

Where is the adrenal glands located

Von Merling and Minkowski (1889)

Who took a dog and removed the pancreas, the dog then became diabetic developing diabetes mellitus

Murray (1891)

Took a sheep thyroid glands and mixed glycerin in it to create an emulsion in which he injected subcutaneously in a 46 year old women who was dying from hypothyroid condition. She was cured from this treatment and was the very first successful instance of helpful hormone replacement therapy.

Oliver and Schafer (1895)

Who injected adrenal extract in animals and witnessed an immediate rise in systemic blood pressure (epinephrine) as well as injecting animals with pituitary extract and witnessed arteries constricting (vasopressin)?

Function of the endocrine system

Maintenance of constant internal milleu through regulation of certain cellular processes in such a way as to promote homeostasis

Rates

Hormones govern the _____ of certain critical or rate-limiting reactions or processes

• Ex: 2 H + ½ O₂ —> H₂O is accelerated by thyroid hormone, but O₂ utilization does not cease after thyroidectomy

Small

Hormones are effective even when present in extremely _____ quantities

Higher

• Intramuscular injection - _____ doses

• Oral administration - still higher

10^-3

Milligram (mg) is ___ gram

10^-6

Microgram (μg) is ___ gram

10^-9

Nanogram (ng) is ___ gram

10^-12

Picogram (pg) is ___ gram

Microgram or nanogram

Intravenous injection (IV) are usually small doses and measured usually in ______ or ______

Balance

Under normal conditions there exists in the body a hormonal _______

Balance

A net result of total production and excretion or destruction

Destruction

Metabolic inactivation of hormone after which the broken down products are excreted from the body via urine or feces

Steroids

Majority of hormones are:

a) proteins or peptides

b) amino acid derivatives

c) ______

Steroids

_______ are part of the fat group (lipid) so its not soluble in water/hydrophobic. Can be carried by the plasma protein through bloodstream.

Inhibitory, synergistic, permissive

Numerous hormonal interactions and relations have been observed. They may be _______, _________, or ________ in nature.

Inhibitory interaction

Occurs when two hormones have opposite effects upon a target cell

• Ex: Insulin and growth hormone (in excess)

Synergistic interaction

Occurs when the effects of the simultaneous administration of two (or more) hormones produces a greater effect than the sum of either given alone, or a new effect produced by neither alone.

• Ex: Thyroid hormone and insulin —> Optimal growth effects

Insulin

Increases uptake and utilization of glucose in the cell

Permissive interaction

• Less synergistic than previous group

• One hormone “conditions” target cells for action of second hormone

• Ex: norepinephrine in a normal animal causes pressor effect to be more (more increase in blood pressure) than norepinephrine in a adrenalectomized animal (- glucocorticoids)

Function of Hormones

Influence reactions that aid in the maintenance of homeostasis

Aldosterone

Has an effect on electrolytes by helping bring sodium into body

Anti-diuretic

Vasopressin has a role to play in water also known as ___-_____, helps keep water in cell

Morphogenic

Hormones have a ________ action (means change in shape)

• Ex: growth process and development of sex characteristics

Autonomic

Hormones regulate ______ activity as well as central nervous system activity and behavioral patterns

Methods of Study of Hormones

1. Abiation by surgery or disease

2. Chemical abiation or impairment

3. Chemical extraction and cellular sources from gland or cell

4. Isotope tracer methods

5. In Vitro (outside of a living organism) techniques

6. Others

Chemical assay

Measurement of a hormone using chemical methods (e.g., extractions, separations)

Assay of Hormones

detection and quantitative determination

Bioassay

Method of measuring volume that uses a measurable change in a living system as an endpoint

Radioisotrope assays

Method of measuring hormones using radioactive isotope tracers

a. radioimmunoassay (RIA)

• combines the specificity of an immune (antigen-antibody) reaction with the use of radioactive isotope tracers

Chemical assay, bioassay, radioisotrope assay, others

What are the four different assay of hormones?

Protein and peptide production

DNA is copied into mRNA inside the nucleus. The mRNA then leaves the nucleus and enters the cytoplasm, where a ribosome binds to it and begins translating it into a protein. This initial, full-length protein chain containing the signal sequence is called the preprohormone. As the ribosome finishes making the protein, the chain is pushed inside the rough ER where an enzyme cuts off the signal sequence. Once it loses its signal sequence, it is now called a prohormone. The prohormone is then packed into a transport vesicle and sent to the Golgi apparatus where the prohormone is folded into its final, active shape. The finished protein is packed into a secretory vesicle that buds off the Golgi. The active protein is now finally called a hormone. It waits in the cell until a signal triggers the vesicle to fuse with the cell membrane, releasing the hormone out of the cell.

Amino acid derivatives

Synthesized from the amino acid tyrosine

• Catecholamines

• Thyroid hormone (discussed later)

Catecholamines

Structure features a benzene ring with two hydroxyl (-OH) groups

Amino acid

Tyrosine is an ______ _____

Dihydroxyphenylalanine (DOPA), Dopamine, Norepinephrine, Epinephrine

What are the four catecholamines?

Steroids

Synthesized from cholesterol by a series of enzymatic reactions

Steroid hormone synthesis from cholesterol

Cholesterol ends up becoming at the end:

• Mineralocorticoid: aldosterone

• Glucocorticoid: cortisol

• Androgen: testosterone/dehydroepiandrosterone

Aldosterone

Mineralocorticoid:

Cortisol

Glucocorticoid:

Dehydroepiandrosterone

Androgen:

Cholesterol

All of these steroids are synthesized from what?

Through receptor in target cell

How must the hormone be recognized?

Receptor

A specific protein in either the plasma membrane or interior of a target cell with which a hormone combines to exert its effect

Plasma membrane

Steroid hormone can meet receptor in cytoplasm or nucleus as it goes right through the _______ ________ and nuclear membrane

Receptors

• Cell membrane components

• Intracellular components

  • cytoplasmic

  • nuclear

Generated

An intracellular signal must be _________

Increased, decreased

One or more intracellular processes must be _______ or _______(e.g., enzyme reactions, ion movements)

Protein, polypeptide

First messenger is the _______, __________ hormone in which it binds to the membrane receptor on the plasma membrane which will relay the message to the 2nd messenger (another chemical/molecule) which binds to the effector protein resulting in cellular effects

Plasma membrane

Protein and polypeptide hormones can’t go through ________ ________ so it requires a membrane receptor and 2nd messenger

cAMP

Cyclic 3’-5’ adenosine monophosphate

Sutherland and Rall

• 1957 - first discovered cAMP (cyclic adenosine monophosphate) second messenger system

flight or fight

The release of glucose into the bloodstream provides fast energy your body needs to fuel a _____ or _______ response