Physiology Final (Endocrine and Reproduction) Ahangari Endo A

Endocrine Glands Powerpoint A

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What is the name of the hormone that acts on a producer cell (itself)?

Autocrine

What is the name of the hormone that acts on target cells (including neurotransmitters) without entering circulation? (Hint: 2 names)

Juxtacrine and paracrine

Can a neurotransmitter be released to act as a hormone?

Yes

Chemical classification of hormones: Hormone Synthesis

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Protein hormone productions _____ require special machinery. (does or does not)

Does not

Examples of protein hormones?

Growth hormone, prolactin, PTH

How are peptide hormones produced?

Cleavage of a larger protein

Some examples of peptide hormones?

Insulin, ACTH, Glucagon

How are thyroid hormones produced?

By iodination and coupling of tyrosine residues of thymoglobulin

What are steroid hormones produced from?

Cholestrol

Do hormones need specific receptors on a target cell?

Yes

Mechanisms of hormone secretion

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Hormones are released by what gland?

Endocrine

Answers to the following will either be: endocrine, exocrine, paracrine, autocrine or intracrine

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Internal secretion of hormones into the circulation to convey info to a target cell? Ductless

Endocrine

Secretion outside of circulation, ex. sweat glands, has ducts

Exocrine

A hormone that acts on neighboring hormone-producing cells or non-hormone-producing cells, ex. action of sex steroids in ovary

Paracrine

Hormone that acts on receptors located on the same cell, may be important in promoting unregulated growth of cancer cells

Autocrine

Hormones that can also act inside the cell without being released?

Intracrine

Two examples of intracrine hormones are insulin and somatostatin, why? Also where are they secreted?

Insulin can inhibit its own release from pancreatic islet B cells and somatostatin can inhibit its own release from pancreatic D cells

Hormone interactions

Synergistic effect, permissive effect, anatagonistic effect

Action of one hormone causes the opposite effect of another, ex. insulin and glucagon

Antagonistic effect

Two or more hormones work to produce a particular effect, ex effect of epinephrine and norepinephrine on the heart

synergistic, both increase heart rate

Enhances responsiveness of target organ to the second hormone, ex cortisol and catecholamines

permissive

Examples of hormones that bind to cell surface receptor?

Insulin, growth hormone, prolactin

Examples of hormones that only bind to intracellular receptors?

Steriods, thyroid

G-protein coupled receptors (seven transmembrane domain receptors)

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G proteins are guanosine triphphate (GTP) bind proteins have how many domains?

7 transmembrane domain receptors

What do they do?

They couple receptors to adjacent effect molecules

When are they used?

Adenylated cyclase, Ca+, calmodulin and inositol 1, 4, 5 triphosphate (IP3) second messanger system

Do they have GTPase activity?

Yes

How many subunits do they have and what are the names?

3 = alpha, beta and gamma

T/F alpha subunit can bind to GDP or GTP?

True

What does the G protein have to bind to, to be active? Inactive?

GDP = inactive, GTP = active

What does Gi and Gs stand for?

Gs = stimulatory, Gi = inhibitory

G protein mediates actions of what? (Examples)

Catecholamines, prostagladins, ACTH, glucagons, PTH, TSH

Growth factor receptors contain what?

Amino terminal surface exposed to ligand binding domain, single membrane spanning domain and carboxyl terminal catalytic domain

Growth factor receptors, including those for insulin IGF and EGF possess what activity?

Tyrosine kinase

Ligand binding results in activation of ___ and autophosphorylation

tyrosine kinase

Growth hormone receptors lack what domain?

tyrosine kinase domain

Cytokine receptors mediate actions of what hormone?

Growth hormone

What is JAK2?

Protein with tyrosine kinase activity

Association of JAK2 with liganded growth hormone receptor leads to what?

Change in JAK2 and activation of its tyrosine kinase catalytic activity, triggers downstream signaling

Ligand regulated transporters are also called what?

Guanylyl cyclasereceptors

What do ligand regulated transporters do?

Can bind ligands and respond by opening the channel for ion flow

Example of ligand regulated transporter? ANP

Promotes vasorelaxation by increasing nitric oxide synthases, stimulates soluble guanylyl cyclase (GC) activity, elevation in cGMP activates cGMP-dependent protein kinases (PKG)

Nuclear receptor mediates actions of what?

Steriod hormones, vit D, thyriod hormones, retionoids, fatty acids and bile acids

How do nuclear receptors control gene expression?

Binding DNA response elements in the promoters of target gene or other transcription factors

What are the three nuclear receptor domains?

1. Animo domain (most variable and mediates effects on transcription)

2. DNA binding domain

3. Carboxyl terminal domain

Steroid hormone and thyroid hormone mechanisms

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Can they easily diffuse across cell membrane?

Yes

They can bind to the nuclear receptor which then exposes what?

DNA binding domain

This can lead to transcription and translation, which does what?

Makes proteins specific to the desired physiological effect