Endo/Repro Exam 1: Endocrine System General Principles

The endocrine system is responsible for the synthesis and secretion of __________. In conjunction with the nervous system, __________ coordinate and integrate the functions of all the physiological systems.

Hormones

Define the following:

A cell secretes a signaling molecule that binds to receptors on the same cell (signaling molecules can be growth factors, prostaglandins, etc.):

Autocrine signaling

t/f: autocrine signaling can coordinate decisions by groups of identical cells, it is most effective when carried out simultaneously by neighboring cells of the same type known as "community effect"

true

in tumors, groups of cancer cells can stimulate their own growth via ______________

Autocrine signaling

What type of singaling is observed in early embryonic development where a group of precursor cells can respond to a differentiation-inducing signal but a single isolated cell could not?

Autocrine signaling

Define the following:

A cell secretes molecules that diffuse locally and trigger a response in neighboring cells

Paracrine signaling

what are some examples of paracrine signaling?

- Neurotransmitters

- Cytokines from T cells to other lymphocytes

- Inflammatory cytokines

- Growth factors

- Histamine

- Nitric oxide

What signaling has the following characteristics?

- Long-distance communication

- Carried to distant target cells via the circulation

- Target cells have receptor proteins that tightly and specifically bind hormones

endocrine signaling

which type of signaling mechanism uses/releases hormones?

endocrine signaling

how do endocrine glands get their signals to their specified target cells?

circulatory system

What regulates the following things:

- Metabolism/nutrient supply

- Growth/development

- Maintenance of internal environment of the body

- Sexual function/reproduction

- Sleep and mood

hormones

hormones are produced by what organs?

brain, heart, GI tract, adipose tissue, placenta, liver

t/f: hormone secretion increases and decreases but is not turned off

true

Hormones are found in ___________ concentrations in plasma

Low (Have high binding affinity)

What is the half life of hormone plasma?

15 seconds to >7 days

Hormones exhibit pleiotrophy which means....

They exert multiple effects on their targets

most hormones exhibit a ______ (growth and function promoting) effect on their target cells

trophic

What is the control of hormonal secretion known as?

"Homeostatic feedback" or "negative feedback"

Define the following:

Regulation of hormonal secretion that reverses the direction of change back to physiological normal

Negative feedback

In negative feedback, if hormone level is too high, what will happen to the gland?

The gland is shut down

In negative feedback, if hormone level is too low, what will happen to the gland?

The gland is stimulated

Define the following:

Regulation of hormonal secretion that augments the direction of change

Positive feedback

In positive feedback, if hormone level is too low, what will happen to the gland?

The gland will shut down even further

In positive feedback, if hormone level is too high, what will happen to the gland?

The gland is stimulated

if a gland suffers hyperplasia or a functional tumor (adenoma or carcinoma), how will it affect secretion?

hypersecretion

if a gland suffers atrophy or a dysfunctional carcinoma, how will it affect secretion?

hyposecretion

In the feedback loop, a rise in blood glucose causes release of ___________ from beta cells the pancreas, promoting glucose uptake in cells and storage as glycogen in the liver.

Insulin

In the feedback loop, a fall in blood glucose stimulates __________ in the pancreas to secrete glucagon, which causes the liver to break down glycogen and release glucose.

Alpha cells

plasma concentration of a hormone is influenced by 5 things:

- Hormone secretion

- Peripheral hormone conversion

- Hormone transport

- Hormone inactivation

- Hormone excretion

What is an example of the peripheral hormone conversion?

T4 --> T3 (more active)

what are the 3 types of hormones?

- Peptides

- Steroids

- Amino acid derivatives

What is the length of peptides?

3-200 amino acids in length

peptide hormones: synthesis

synthesized in endocrine cells as precursor molecules and stored in vesicles

peptide hormones: secretion

use vesicle fusion to secrete the hormone

peptide hormones: storage

precursors during storage and get post-translationally modified into their active form

walk through the release of peptide hormones

1. Messenger RNA on the ribosomes binds amino acids into a peptide chain called a preprohormone.

The chain is directed into the ER lumen by a signal sequence of amino acids.

2. Enzymes in the ER chop off the signal sequence, creating an inactive prohormone.

3. The prohormone passes from the ER through the Golgi complex.

4. Secretory vesicles containing enzymes and prohormone bud off the Golgi. The enzymes chop the prohormone into one or more active peptides plus additional peptide fragments.

5. The secretory vesicle releases its contents by exocytosis into the extracellular space.

6. The hormone moves into the circulation for transport to its target.

At what step in the peptide synthesis and release does it become active?

When it is released

insulin is what type of hormone?

Peptide hormones

What type of hormones are electrically charged molecules and are soluble in plasma?

Peptide hormones

What type of hormones can be freely filtered glomerulus and have relatively short half lives (~30 minutes)?

Peptide hormones

What type of hormones do not pass through membranes, bind to cell surface receptors to cause an effect on the channels and inner membrane surface?

Peptide hormones

What is broken down into 6 TRH, other peptides, and a signal sequence through matruation?

Prepro TRH

What is broken down into ACTH, lipotropin, endorphin, and a fragment through maturation?

Pro-opiomelanocortin

How can you figure out how much insulin is in the blood?

Measure C-peptide

What type of hormones receptors couple to intracellular signaling pathways via G-proteins that activate intracellular pathways mediated by enzymes (adenylyl cyclase/phospholipase C)?

Peptide hormones

What type of hormones are derivatives of cholesterol - therefore they are lipids?

steroid hormones

steroid hormones: storage

not stored because they are lipids and would leak out of a vesicle or cell membrane- hence they are synthesized and secreted on demand

All of the following are derived from what precursor?

- Progesterone

- Cortisol

- Testosterone

- Estriol

Cholesterol

Why are steroid hormones not stored?

Because they are lipids and would leak out of a vesicle or cell membrane- hence they are synthesized and secreted on demand.

steroid hormones: transport

sparingly soluble in the plasma and typically over 90% of the hormone is carried in the plasma bound to a specific carrier protein or to albumin

a hormone that is free and able to cross membranes and enter target cells is _________

bioavailable

steroid hormones are only bioavaialble when they are…?

free (bound molecules are released from carrier proteins to replace free hormones)

What type of hormones are best described as transcription factors?

steroid hormones

What type of hormone binds to its receptor and dimerizes, binds to a specific DNA and generates new mRNA and new proteins that alter function of target cell?

steroid hormones

Where do zinc fingers attach to?

DNA binding region (fit in helical structure)

Thyroxine is what type of hormone?

amino acid derivative hormones

tyrosine is what type of hormone?

amino acid derivative hormones

Epinephrine is what type of hormone?

amino acid derivative hormones

Tryptophan is what type of hormone?

amino acid derivative hormones