Exam 1

HOMEOSTASIS

REQUIRES INTEGRATION

NERVOUS SYSTEM

Fast, electrical/chemical, targeted, short-lived, impulses

ENDOCRINE SYSTEM

slower, chemical, widespread, often longer-lasting, hormones

Endocrine system

acts with nervous system to coordinate and integrate activity of body cells

A hormone can travel almost everywhere

Only cells with the appropriate receptor respond transported through blood. Responses slower but longer lasting than nervous system responses

Endocrine system controls and integrates:

Reproduction, growth and development, maintenance of electrolyte, water , and nutrient balance of blood, regulation of cellular metabolism and energy balance, mobilization of body defenses

Metabolism

all the chemical changes in your body that turn food into energy

Homeostasis

is the steady balance of your body's inner conditions

1. Endocrine cell ____ a hormone

secretes

2. Hormone enters the

bloodstream

3. Hormone travels through the blood to

target cells

4. Hormone binds to a _____ on the target cell

specific receptor

5. target cell responds producing a

specific effect

Exocrine

Gland → duct → surface/lumen
ex. Sweat, saliva, digestive enzymes

Endocrine

Gland → bloodstream → target cells

NO ducts

What are the endocrine glands

Pituitary, thyroid, parathyroid , adrenal, and pineal

What is a neuroendocrine gland

Works with nervous and endocrine system, Hypothalamus

These glands have exocrine and endocrine

pancreas, gonads, placenta

Other tissues and organss that produce hormones

adipose cells, thymus, and cells in Walls of small intestine, stomach, kidneys, heart

Endocrine message travel

Cell → bloodstream → distant target
Long distance signaling
ex: insulin

Paracrine

Cell → nearby cell
local signaling
ex: histamine

Autocrine

Cell stimulates itself
self-signaling
ex: some cytokines

Water soluble Peptides & protiens

Insulin, ADH, Growth Hormone

Water soluble Amines

Epinephrine, Norepinepherine

Water soluble

mix easily with blood but cannot freely cross the plasma membrane

Lipid soluble steroid hormones

Cortisol, aldosterone, estrogen, testosterone

Lipid soluble thyroid hormone

T3 & T4

Lipid soluble

Often carrier proteins in blood and can cross the plasma membrane

Prohormones

Inactive molecules converted to active hormones before or after they are secreted

Steroids are synthesized from what

cholesterol

What can cross easily in plasma membrane

Small, no polar, lipid soluble

If hormone cant enter cell its receptor is

on plasma membrane

if hormone can enter cell its receptor must be

inside the cell

Water soluble route

Hormone → Membrane receptor → signal relayed inside cell → existing protein change activity → cell response

Lipid soluble route

Hormone enters cell → intracellular receptor → DNA → new proteins are produced → cell response

Signal transduction pathway

Receptor → G protein → Adenylyn Cyclase → ATP → cAMP → protien kinase activates → target protien activates

GDP

Before the hormone arrives: the G protein has GDP attached, so the G protein is OFF.

GPCR

Hormone attaches to the receptor (GPCR) on the outside of the cell.

The receptor tells the G protein to release GDP.

GTP

replaces GDP on the G protein.

Now that GTP is attached, the G protein is ON/activated.

The activated G protein leaves the receptor and goes to activate the next protein in the pathway

cAMP

1. Activated G-protein bind adenylate cyclase

2. Adenylate cyclase becomes active

3. Produces cAMP (a second messenger)

• requires ATP

Kinases

are enzymes that add a phosphate group to another group (also called phosphorylation)

Phosphorylation

Addition of phosphate. plasma membrane proteins can, in turn, open ion channels

Phosphodiesterase

is an enzyme that inactivates CAMP by converting it to AMP (adenosine monophosphate)

Hormones that use the adenylate cyclase pathway include:

glucagon, ADH, epinephrine, TSH and FSH

PLC (phospholipase C)

1. Hormone → G protein → PLC → PIP₂ splits → DAG + IP₃ → protein activation

what is PLC

an enzyme attached to the inner surface of the plasma membrane.

DAG

Its major job is to help activate protein kinase C (PKC).

IP3

Unlike DAG, leaves the membrane and travels through the cytoplasm.

It reaches the ER and binds to IP₃ receptors.

That causes: ER releases Ca²⁺

CA2+

The released __is also a second messenger.

→ bind calmodulin → activate other enzymes/kinases → cell response

Why So Many Steps?

AMPLIFICATION

Examples of carrier proteins lipid soluble use

Albumin, Thyroxine-binding globulin, Corticosteroid-binding globulin, Sex hormone-binding globulin

1. Lipid soluble hormone ___plasma membrane

crosses

2. Binds _____ receptor

Intracellular

3. Forms a _________

Hormone -receptor complex

Hormone–receptor complex enters the nucleus and binds specific

DNA regulatory

Transcription produces____hat leads to production of new proteins by translation

mRNA

Which would you predict acts faster?

water Soluble

Which would you predict has a slower onset?

• lipid Soluble 

• Which might have longer-lasting effects?

lipid soluble

• How strongly a target cell responds depends on:

hormone concentration, number of receptors, receptor affinity (strong ness)

Most endocrine pathways are regulated by

negative feedback

- that influence hormone concentration:

The rate of synthesis/release, the rate of hormone degradation/removal

Hormone Half-Life (t½) Half-life

•  the time it takes for the blood concentration of a hormone to decrease by 50%.

• Synergistic

• Hormones can work together to produce a greater effect

Antagonistic

• Hormone actions oppose each other

Permissive

• One hormone enhances or enables a target tissue's response to another hormone.

• Cortisol must be present for glucagon to produce its full effect on blood glucose. What type of interaction is this?

Permissive

• Humoral stimulus

Changing blood levels of ions/nutrients leads to hormone release

Neural stimulus

Neuron directly stimulates endocrine cells

• Hormonal stimulus

One hormone stimulates another endocrine gland

The hypothalamus controls the posterior pituitary through

neurons
synthesizes ADH and Oxytocin

The hypothalamus controls the anterior pituitary through

hormones
uses Hypophyseal portal system

The hypothalamus also has

direct automatic control of some endocrine tissues

A student nearly gets hit by a car while crossing the street. Sympathetic neurons directly stimulate the adrenal medulla, causing epinephrine release.

Neural

• After a calcium-poor diet, a patient's blood Ca²⁺ level decreases. The parathyroid glands detect the change and release PTH.

Humoral

• The anterior pituitary releases TSH, which travels through the blood and stimulates the thyroid gland to release T₃ and T₄.

Hormonal

Anterior pituitary

Adenohypophysis

Glandular tissue

Posterior pituitary

Neurohypophysis

Neural tissue

Does the posterior pituitary synthesize its own hormones

No
Hypothlamic Neuron → axon → posterior pituitary → blood

ADH / vasopressin

Promotes water conservation by kidneys

Important in blood volume/osmolality regulation

Oxytocin

Uterine contraction

Milk ejection

Which organ SYNTHESIZES ADH and oxytocin?

Which organ RELEASES ADH and oxytocin?

Hypthalamus & Posterior pituitary

The Hypophyseal portal system

Hypothalamus → Primary Capillary Plexus → portal system → secondary capillary Plexus → anterior pituitary cells

TSH

Thyroid-stimulating hormone, thyroid gland

ACTH

Adrenocorticotropic hormone, adrenal cortex

FSH

Follicle-stimulating hormone, Gonads

LH

Luteinizing Hormone, Gonads

GH

Growth hormone, Many tissues/liver

PRL

prolactin; mammary glands

Tropic

Act primarily on another endocrine gland.
TSH
ACTH
FSH/LH

Nontropic

Direct effect
GH
PRL
ADH

primary Dysfunction:

Problem in the target endocrine gland 

secondary dysfunction

Problem in pituitary

What Does Thyroid Hormone Actually Do?

↑ cellular metabolic activity
↑ oxygen consumption

↑ ATP production/use 

↑ heat production 

Why do people with hyperthyroidism often feel hot?

Because increased metabolism means increased heat production.

• Why Can T₃/T₄ Change Cellular Activity?

because its lipid soluble

T₃

Iodines: 3
Biological activity: more active

Circulating amount in blood: less
role: major active form

T4

Iodines: 4
Biological activity: less active
Circulating: More/in reverse (Can pull out iodine to make T3)
Role: Major circulating form

Colloid

Protein-rich fluid filled within the thyroid follicles of thyroid gland

What do the Follicular Cells Do?

Synthesize Thyroglobulin (TGB)
secreted into colloid

Thyroglobulin = protein scaffold

TH (T3 & T4) is released from the colloid