Endocrine System / Hormones

Cell differentiation

the process by which a less specialized cell becomes a more specialized cell type

Living cells group together to form

tissues

Tissues group together to form

organs

Different organs group together to form

an organ system

Organ systems group together to form

an organism

DNA is complexed with ___________ to form _____________

histones, nucleosomes

4 most abundant elements in the body

oxygen, carbon, hydrogen, nitrogen

Proteins are synthesized using

mRNA

What system is a communication system in the body?

nervous and endocrine system

Is the nervous system or endocrine system faster?

nervous system

endocrine system is slower, releases hormones

The ___________ part of the endocrine system also has neurologic origins and produces __________________ which is a neurotransmitter

adrenal medulla, norepinephrine

The hypothalamus is a _____________ tissue

neural

What does the hypothalamus produce?

peptide hormones ADH and Oxytocin

The hypothalamus also produces releasing or inhibiting factors that control...

endocrine system

Endocrine organs produce _______________ based on finely regulated ________________ systems that are tuned to set points

hormones, feedback control systems

What does the endocrine system regulate?

growth, metabolism, and sexual development

Hormone

chemical messengers of the body's endocrine glands

Paracrine function

chemical substances are released and act on neighboring cells

Autocrine function

chemical substances are released and act on the same cell

Exophthalmos

bulging eyes

Endocrine function

hormones are secreted by endocrine cells and carried through the blood stream where they affect far away target cells

Example of endocrine hormone

growth hormone (released by pituitary)

Example of paracrine hormone

testosterone (leydig cells)

Example of autocrine hormone

estradiol (supports reproductive system)

First hormone to be discovered

anti-diabetic factor

Cortisol is an

anti-inflammatory

Estradiol

supports uterine function

How are hormones regulated? What type of feedback?

negative

Half life

the amount of time that a substance exists until it is reduced by half

After 3 half-lives, the fraction of substance remaining is

1/8

Hormones have _______________ that produce opposing effects

counterparts

Insulin promotes...

glucose uptake into cells

Glucagon promotes...

glucose release from the liver

The shorter the half life...

the tighter the control

The half life of a hormone is an indicator of how tightly regulated their __________________________________________________

levels and effects are controlled

Blood hormone levels are

very low

How are hormones measured?

ELISA

enzyme linked immunosorbent assay

General hormone mechanisms

1. at the cell surface (peptide hormones)

2. at the cell nucleus (steroid hormones)

Hormones of the endocrine system are secreted directly where?

into the blood stream

Exocrine glands secrete products where?

into a duct (ex: sweat gland)

Pancreas is located where?

tucked under the stomach

Much of the pancreas is dedicated to the production of digestive enzymes which it secretes where?

into the intestine through a duct

exocrine secretion

Pancreas secretes enzymes in what way (endo or exo?)

exocrine secretions

Insulin is secreted into __________ and thus into _________________

blood capillaries, general circulation

endocrine secretion

The B cell of the pancreas contains

insulin

The B cell of the pancreas contains uncoated secretory granules that store ______________ and are released from the cell when?

insulin, if the level of glucose in the blood rises

3 types of hormones

endocrine, paracrine, autocrine

How are hormones tightly regulated?

bioavailability

half life

diurnal variation

rate of release

negative feedback

competing hormones

series of relays to target tissues

What makes measuring hormones challenging?

low blood levels and limited bioavailability

Where are hormones produced?

endocrine glands

What is the master regulator of hormones?

pituitary gland

Peptide hormone

a hormone made of amino acids (proteins)

What name has also been given to some peptide hormones dating from a time when their peptide/protein nature was unknown?

factor

Some of the smaller peptide hormones that exist are from...

the hypothalamus and anterior and posterior pituitary

Tripeptide hormone

a hormone containing 3 amino acids released in the hypothalamus

Example of a tripeptide

TRH - Thyroid releasing hormone

Growth hormone is released from the _________________ and targets ____________________

anterior pituitary gland

liver and bone

What does growth hormone do?

causes increase in metabolism and bone growth

What structure does growth hormone have?

considerable a-helical and random coil structure

Where do peptide hormones bind?

bind to cell surface receptor because they are charged and can't pass membrane

Small peptide hormones are

at low concentration and soluble enough to be transported unbound to any soluble carrier

Large protein hormones require

a soluble protein which is similar to the protein receptor it binds to on cell surfaces

Growth hormone is an example of

a large protein hormone

What happens to peptide hormones after binding to their receptors?

they are commonly taken up by the cells and are transported to lysosomes where they are broken down

Where is the fate of peptide hormones?

the lysosome where they are degraded

Are peptide hormones stable?

no- their fate is to be degraded by lysosomes

Insulin is an example of a (peptide/steroid) hormone

peptide

Peptide hormones are considered protein hormones if

they contain over 40 AA

Insulin structure

2 chains (A and B) joined by disulfide bonds

-3 disulfide bonds: 1 intrachain on the A chain and 2 interchain between the A and B chains

Insulin is associated with

diabetes

What is the major role of insulin?

to facilitate uptake of glucose into cells by means of glucose transport proteins

Where is insulin produced?

inslet cells of the B cells in pancreas

Where is glucagon made?

alpha cells of pancreas

Somatostatin

hormone that inhibits release of growth hormone and insulin

Endocrine glands of the pancreas secretes

insulin and glucagon

Preproinsulin

Protein cleaved to become proinsulin which is cleaved to become insulin

50% of insulin is lost to the first...

pass effect of the liver

Where is proinsulin degraded?

kidney

The insulin receptor protein

structure that lets insulin into the cell

Structure of the insulin receptor protein

tetrapeptide, made of 2 a and 2 b subunits

When insulin binds to its receptor protein, what happens?

it causes a conformational shape change that activates the tyrosine kinase activity on the inside of the membrane

When is glycogen produced?

when blood glucose levels are high

GLUT4

stimulated by insulin

Another example of a peptide hormone

thyroid stimulating hormone

TSH

thyroid stimulating hormone

cAMP mechanism

- Hormone binds to the extracellular side of G-protein coupled receptor

- Receptor activates intracellular G-protein

- G-protein activates adenylyl cyclase

- Adenylyl cyclase produces cAMP from ATP

-cAMP activates protein kinase cascade to cause intracellular response

What can break down cAMP before it enters any cascade?

cAMP phosphodiesterase (PDE)

cAMP + inactive pKA =

active pKA

PKA (protein kinase A)

activated by cAMP

The calcium/calmodulin mechanism's initial binding of the hormone to its membrane protein receptor and activation of the G protein goes on to activate _____________

PIP2

Are peptide hormones polar or nonpolar?

polar

Peptide hormones are synthesizes as...

prehormones or preprohormones

Peptide hormones are stored in

membrane bound granules

Can peptide hormones be administered orally?

no

Peptide hormones largely signal through

G protein receptors via PKA or CDAG

Types of steroid hormones

glucocorticoids, mineralocorticoids, androgens and estrogens

Glucocorticoids

promote increased metabolism of carbohydrates, lipids, and proteins

Mineralocorticoids regulate...

salt recovery and water volume

Androgens and estrogens affect...

development of sex organs

Synthesis of steroid hormones is stimulated by

pituitary gland