Chapter 11 PHYSIO

Endocrine system function

Regulates body, metabolism, growth and reproduction

The Endocrine system consist of?

Endocrine glands and Hormones

Endocrine glands

-Produce, store and/or release hormones into blood.

-Is ductless

Hormones

Chemical messengers of the endocrine system

The three classes of Hormones based on chemical structure

Amine hormones, Peptide hormones, and Steroid hormones

Amine hormones relationship with water and lipids?

Can be lipid or water soluble

Peptide hormones relationship with water and lipids?

Are water soluble only ( hydrophilic / polar hormones )

Steroid hormones relationship with water and lipids?

Are lipid soluble only ( Hydrophobic / non-polar hormones )

Anime hormones is how long?

only one amino acid long

Peptide hormones is how long?

Several amino acid long

Amine hormones derivatives of?

Amino acid tyrosine and tryptophan

Examples of Amine hormones

-Norepinephrine and epinephrine ( both derived from tyrosine )

- Serotonin ( both derived from tryptophan )

Examples of Peptide hormones

Insulin, glucagon, oxytocin, growth hormone ( GH )

Peptide hormones include what ?

Also includes glycoprotein hormones such as LH and FSH

Steroid hormones derivatives of?

Cholesterol

Examples of Steroid hormones

Testosterone, aldosterone, estrogen, cortisol, thyroid, hormone

Explain why water soluble hormones are not able to passively diffuse through the cell membrane, and why lipid soluble hormones are able to passively diffuse through

The cell membrane is composed of phospholipid bilayer. It repels charged or polar molecules

The Hormone Classification by action

Polar hormones and Nonpolar hormones

Polar hormones are soluble or insoluble water ?

They are water soluble ( dissolve in water )

Nonpolar hormones are soluble or insoluble water ?

They are insoluble in water ( no dissolve in water )

Where can you find the Polar hormones receptors?

Receptors found on the targets cell surface ( outside the cell )

Where can you find the Nonpolar hormones receptors?

Receptors are found inside the target cell

Can polar hormones pass through the cell membrane?

Polar hormones cannot pass through cell membrane because charged/polar things cannot cross the cell membrane

Can Nonpolar hormones pass through the cell membrane?

Can enter the target cell directly

Nonpolar hormones are often called?

Lipophilic Hormones ( Lipid soluble )

Anterior pituitary

produces and secretes 6 different hormones; hangs from the base of the brain

The 6 different hormones in the anterior pituitary

-Human Growth Hormone ( hGH )

-Thyroid Stimulating Hormone ( TSH )

-Adrenocorticotropic Hormone ( ACTH )

-Prolactin ( PRL )

-Follicle Stimulating Hormone ( FSH )

-Luteinizing Hormone ( LH )

Human Growth Hormone ( hGH )

- Controls body growth

- Targets bone, muscle and adipose tissue

Thyroid Stimulating Hormone ( TSH )

Controls secretion of hormones by thyroid gland

Adrenocorticotropic Hormone ( ACTH )

Controls secretion of hormones by adrenal cortex

Prolactin ( PRL )

Stimulates production of milk in mammary gland

Follicle Stimulating Hormone ( FSH )

- In females: Stimulates maturation of an ovarian follicle and ovum

- In males: Stimulates maturation of sperm in testes

Luteinizing Hormone ( LH )

- In females: Causes ovulation

- In males: causes secretion of testosterone

Where is posterior pituitary located?

Behind the anterior pituitary

Posterior pituitary

- Does not produce hormones

- Stores and secretes 2 hormones produced by the hypothalamus

Posterior pituitary 2 hormones

Anti-Diuretic Hormone ( ADH ) and Oxytocin ( OT )

Anti-Diuretic Hormone ( ADH )

Controls water balance and increases blood pressure ( causes water to be reabsorbed into blood )

Oxytocin ( OT )

Causes uterine muscle contraction and milk release ( letdown reflex )

Where is Thyroid Gland located?

Located below larynx and around trachea

Thyroid gland

Produces 3 hormones and involved in iodine uptake

The 3 hormones that Thyroid gland produce

Thyroxine (T4), Triiodothyronine (T3), and Calcitonin (CT)

Thyroxine ( T4 )

Inactive thyroid hormone

Triiodothyronine ( T3 )

- Active thyroid hormone

- Increase metabolic rate by stimulating production of ATP

Calcitonin ( CT )

Regulates ( decreases ) Ca++ levels in blood and functions in bone formation

Adrenal gland located?

located atop the kidney

Adrenal gland divided into

Adrenal medulla and adrenal cortex

Adrenal medulla

produces 2 closely related hormones that function in the sympathetic nervous system. Central portion of adrenal gland

The 2 hormones that Adrenal Medulla produce

- Epinephrine ( adrenaline )

- Norepinephrine ( noradrenaline )

Adrenal cortex

Produces many steroid hormones when stimulated by ACTH, Outer portion of adrenal gland

Adrenal cortex produces what steroid hormones?

Aldosterone and Cortisol

Aldosterone

increases blood pressure

Cortisol

Increases blood pressure, weakens immune activity

Pancreas Function

function as both endocrine and exocrine gland ( digestion )

Pancreas location

Located behind stomach on left side of abdomen

Pancreas contain what structure?

Contain structures called Islets of Langerhans

Islets of Langerhans produce what 2 hormones?

Insulin and Glucagon

What are islets of Langerhans

They are clusters of cells in the pancreas that secrete hormones.

Insulin produced by?

Produced by beta cells in Islets of Langerhans

Glucagon produced by?

Produced by alpha cells in Islets of Langerhans

explain how insulin lowers blood glucose levels

Insulin moves glucose from blood into cells to form glycogen in liver and skeletal muscles.

Explain how glucagon raises blood glucose levels.

Glucagon causes breakdown of glycogen and releases glucose into blood to raise blood glucose

Ovaries produce

Estrogen and Progesterone

Testes produce

Testosterone

Some hormones can also be neurotransmitters (NTs). What determines whether a hormone will  act as a hormone vs a NT?

Epinephrine and norepinephrine can act as both NT and hormone. However, when they are released by a neuron then they’re acting as NT. However, when they are released by the adrenal medulla into the bloodstream, then they are acting as a hormone.

 What mechanism can be used to regulate the amount of hormone released from an endocrine gland. (hint – what mechanism stops further release of a hormone?) 

Negative feedback

TRUE or FALSE: A target cell can only respond to one hormone.

False. A target cell has receptors for many hormones and can respond to more than one hormone.

Half-life

Time it takes for hormone concentration in blood to be reduced by ½

Synergistic effect of 2 hormones

Two hormones have the same function; their combined effect is greater than the sum of their individual effects

If both epinephrine and norepinephrine affect the heart at the same time, does their combined effect increase heart rate by 30%

No! Its much higher

Example of Synergistic effect of 2 hormones

Epinephrine and norepinephrine

Antagonistic effect of 2 hormones

One hormone opposes/inhibits another hormone

Example of Antagonistic effect of 2 hormones

- Insulin and glucagon both involve regulation of blood glucose levels; but both have opposite effects

- Calcitonin and parathyroid hormone PTH both involve regulation of blood calcium levels, but both have opposite effects

Insulin

Lowers blood glucose levels by storing it and making glycogen

Glucagon

Increases blood glucose levels by breaking down glycogen

Permissive effects of 2 hormones

Presence of one hormone is required for another hormone to exert its full effect on a target cell; one hormone enhances the effect of another hormone

What is thyroid hormone doing to permit the effect of epinephrine?

Thyroid hormone increases the number of epinephrine receptors on target cell ——> epinephrine will now have a greater effect

Example of Permissive effects of 2 hormones

 Epinephrine strongly stimulates lipolysis when there’s presence of T3. Because T3 increases receptors for epinephrine on target cells

Priming effect of a hormone ( aka upregulation )

Increasing the number of receptors on the target cell for the same hormone or for a different hormone

If the number of receptors are increased for a different hormone, the the priming effect may be an example of

permissive effect

Example of priming effect

T3 ( thyroid hormone ) and epinephrine; leads to an increased response to epinephrine

Desensitization effect of a hormone (aka down regulation )

Decreasing the number of receptors on the target cell

Desensitization effect leads to

a decreased response to hormone after prolonged exposure to a hormone——> to prevent overstimulation of target cell by lingering hormone

 Explain how negative feedback is involved in thermoregulation

Excess T3/T4 or excess heat produced would inhibit the hypothalamus from releasing TRH and the anterior pituitary from releasing TSH. A process of end product inhibition

Water Soluble Hormones Hydrophilic or Hydrophobic?

Hydrophilic ( polar hormones )

Where does water soluble hormone receptor bind to?

water soluble hormone receptor

Where are water soluble hormone receptor located?

on target cell surface

What category/type of hormone binds to extracellular/cell surface receptors? Why is the receptor located on the cell surface?

Polar hormones bind to extracellular/cell surface receptors because they cannot pass through the cell membrane.

What two pathways that water soluble hormones use?

Adenylate Cyclase - cAMP Pathway

Phospholipase C- Ca++ Pathway

Adenylate Cyclase - cAMP Pathway ( G protein coupled receptor pathway )

pathway activated by various hormones

- LH

- glucagon

- epinephrine

Phospholipase C- Ca++ Pathway

Pathway activated by TSH, ADH, Angiotensin

What category/type of hormone binds to intracellular receptors? Why is the receptor located inside the cell?

Nonpolar hormones bind to intracellular receptors. The receptor is located inside the cell because the hormones can easily pass through the cell membrane to get into the cell but they cannot stay outside of the cell.

Describe how the adenylate cyclase – cAMP pathway works. What is the function/action of  active protein kinase? 

Polar hormone binds receptor on cell surface → Gprotein’s alpha subunit dissociates → activated Adenylate cyclase → ATP converted to cAMP → cAMP activated PK → active PK phosphorylates enzymes to deactivate or activate them.

Describe how the phospholipase C – Ca++ pathway works. What happens to the Ca++ that gets released into the cytoplasm (what does it bind to)?

Polar hormone binds receptor on cell surface → Gprotein’s alpha subunit dissociates → activated Phospholipase C → IP3 and DAG → IP3 binds to its receptor on ER/SR → Ca++ released from ER/SR → Calmodulin-Ca++ → activated PK → active PK phosphorylates enzymes to deactivate or activate them.

TRUE or FALSE: calmodulin is an active compound

False. Calmodulin is only active when bound to Ca++

A 2-system pathway for Glycogenolysis

One hormone may activate 2 or more pathways in a single cell; sometimes pathways can converge

Glycogenolysis

Process of breaking down glycogen into glucose

what 2 hormones promote glycogenolysis

Glucagon and epinephrine promote glycogenolysis

what is the end product of glycogenolysis?

End product is Glucose

Liver cell has 2 types of epinephrine receptors

Alpha adrenergic receptor and Beta adrenergic receptor

Alpha adrenergic receptor activates

the Phospholipase C pathway