ANAPHY: LESSON 9 - ENDOCRINE SYSTEM

LINURONG GUD TALAGA INI KAY DADAMO MAN NGAN MAGKURI PAT WORDS

endocrine system

is composed of endocrine glands and specialized endocrine cells located throughout the body.

Hormones

Chemical messengers secreted in small amounts by endocrine glands and cells into the extracellular fluid. It regulate physiological processes in the body.

target tissues

Hormones then travel through the general blood circulation to specific sites called

endocrine

derived from the Greek words endo, meaning within, and krino, to secrete, which appropriately describes this system.

Exocrine glands

have ducts that carry their secretions to the outside of the body, or into a hollow organ, such as the stomach or intestines. Examples of it are saliva, sweat, breast milk, and digestive enzymes.

endocrinology

study of the endocrine system

Chemical messengers

allow cells to communicate with each other to regulate body activities.

gland

is an organ consisting of epithelial cells that specialize in secretion, which is the controlled release of chemicals from a cell.

secretion

which is the controlled release of chemicals from a cell.

1. Autocrine chemical messengers

2. Paracrine chemical messengers

3. Neurotransmitters

4. Endocrine chemical messengers

four classes of chemical messengers

Autocrine chemical messenger

are chemical messenger that stimulates the cell that originally secreted it, and sometimes nearby cells of the same type.

Paracrine chemical messengers

chemical messengers that are secreted by one cell type into the extracellular fluid and affect surrounding cells.

Neurotransmitters

are chemical messengers secreted by neurons that activate an adjacent cell, whether it is another neuron, a muscle cell, or a glandular cell. They are secreted into a synaptic cleft, rather than into the bloodstream. In the strictest sense they are paracrine messengers.

Endocrine chemical messengers

chemical messengers that are secreted into the bloodstream by certain glands and cells, which together constitute the endocrine system. These chemical messengers affect cells that are distant from their source.

1. Regulation of metabolism

2. Control of food intake and digestion

3. Modulation of tissue development

4. Regulation of ion levels

5. Control of water balance

6. Regulation of cardiovascular functions

7. Control of blood glucose and other nutrients

8. Control of reproductive functions

9. Stimulation of uterine contractions and milk release

10. Modulation of immune system function

main regulatory functions of the endocrine system

Regulation of metabolism

The endocrine system regulates nutrient utilization and energy production.

Control of food intake and digestion

The endocrine system regulates satiety and the breakdown of food into nutrients.

Modulation of tissue development

The endocrine system influences the development of tissues, including those in the nervous system.

Regulation of ion levels

The endocrine system regulates ion levels in the body, including Sodium (Na+), Potassium (K+), and Calcium (Ca2+).

Control of water balance

The endocrine system regulates water balance by controlling solutes in the blood.

Regulation of cardiovascular functions

The endocrine system helps regulate heart rate and blood pressure, preparing the body for physical activity.

Control of blood glucose and other nutrients

The endocrine system regulates blood glucose and other nutrient levels in the blood.

Control of reproductive functions

The endocrine system controls the development and functions of the reproductive systems in males and females.

Stimulation of uterine contractions and milk release

The endocrine system regulates uterine contractions during delivery and stimulates milk release in lactating females.

Modulation of immune system function

The endocrine system helps control the production and functions of immune cells.

hormone

is derived from the Greek word hormon, which means to set into motion. They are very powerful molecules

1. lipid-soluble hormones

2. water-soluble hormones

two chemical categories of hormone

Lipid-soluble hormones

are nonpolar, and include steroid hormones, thyroid hormones, and fatty acid derivative hormones, such as certain eicosanoids.

lipid-soluble hormones

Because of their small size and low solubility in aqueous fluid, they travel in the bloodstream attached to binding proteins, which are proteins that transport the hormones.

binding proteins

proteins that transport the hormones.

Transport of lipid-soluble hormones

Lipid-soluble hormones travel in the bloodstream attached to binding proteins, extending their lifespan.

Water-soluble hormones

Polar hormones that include protein hormones, peptide hormones, and most amino acid derivative hormones.

water-soluble hormones

Hormones that can dissolve in blood,

free hormones

most of them dissolve directly into the blood and are delivered to their target tissue with-out attaching to a binding protein.

water-soluble hormones

are quite large, they do not readily diffuse through the walls of all capillaries; therefore, they tend to diffuse from the blood into tissue spaces more slowly.

water-soluble hormones

are quite small and require attachment to a larger protein to avoid being filtered out of the blood.

Water-soluble hormones

have relatively short half-lives because they are rapidly degraded by enzymes, called proteases, within the bloodstream.

1. Having a carbohydrate attached to them.

2. Having a terminal end protected from protease activity.

3. Having binding proteins

Three important modifications made to hormone molecules

Transport of water-soluble hormones

Water-soluble hormones dissolve directly into the blood and circulate as free hormones or attach to larger proteins for circulation.

1. humoral

2. neural

3. hormonal

Three types of stimuli regulate hormone release

humoral stimuli

molecules and ions in the bloodstream that can directly stimulate the release of some hormones.

humoral

a word that refers to body fluids, including blood.

neuropeptides

Some neurons secrete chemical messengers directly into the blood when they are stimulated, making these chemical messengers hormones.

releasing hormones

Specialized neuropeptides stimulate hormone secretion from other endocrine cells

releasing hormones

a term usually reserved for hormones from the hypothalamus.

hormonal stimuli

It occurs when a hormone is secreted that, in turn, stimulates the secretion of other hormones

tropic hormones

The most common examples are hormones from the anterior pituitary gland

Inhibition of hormone release

Hormone release can be inhibited by humoral, neural, and hormonal stimuli to maintain balance in the body.

Inhibition of Hormone Release by Humoral Stimuli

Often when a hormone’s release is sensitive to the presence of a humoral stimulus, there exists a companion hormone whose release is inhibited by the same humoral stimulus. Usually, the companion hormone’s effects oppose those of the secreted hormone and counteract the secreted hormone’s action.

Inhibition of Hormone Release by Neural Stimuli

Neurons inhibit targets just as often as they stimulate targets. If the neurotransmitter is inhibitory, the target endocrine gland does not secrete its hormone.

Inhibition of Hormone Release by Hormonal Stimuli

Some hormones prevent the secretion of other hormones, which is a common mode of hormone regulation.

Inhibiting hormones

Hormones from the hypothalamus that prevent the secretion of tropic hormones from the pituitary gland.

1. negative feedback

2. positive feedback

Two major mechanisms maintain hormone levels in the blood within a homeostatic range:

Negative feedback

A mechanism in which the secretion of a hormone is inhibited by the hormone itself once blood levels have reached a certain point and there is adequate hormone to activate the target cell.

Negative feedback

The hormone may inhibit the action of other, stimulatory hormones to prevent the secretion of the hormone in question.

Negative feedback

self-limiting system

Positive feedback

A mechanism in which hormones, when stimulated by a tropic hormone, promote the synthesis and secretion of the tropic hormone in addition to stimulating their target cell.

Positive feedback

stimulates further secretion of the original hormone.

Positive feedback

it is a self-propagating system

receptors

Hormones exert their actions by binding to target cell proteins

receptor site

The portion of each receptor molecule where a hormone binds and the shape and chemical characteristics of each site allow only a specific type of hormone to bind to it.

Specificity

The tendency for each type of hormone to bind to one type of receptor, and not to others.

1. Lipid-soluble hormones

2. water-soluble hormones

classes of receptors

Lipid-soluble hormones

bind to nuclear receptors

Lipid-soluble hormones

They diffuse through the plasma membrane and bind to nuclear receptors, which are most often found in the cell nucleus

nuclear receptors

which are most often found in the cell nucleus. It can also be located in the cytoplasm, but then move to the nucleus when activated.

Water-soluble hormones

bind to membrane-bound receptors

Water-soluble hormones

are polar molecules and cannot pass through the plasma membrane. Instead, they interact with membrane-bound receptors, which are proteins that extend across the plasma membrane, with their hormone-binding sites exposed on the plasma membrane’s outer surface

membrane-bound receptors

which are proteins that extend across the plasma membrane

Action of nuclear receptor

hormone-­response elements

The receptors that bind to DNA and recognize specific nucleotide sequences are called hormone-response elements. They have fingerlike projections that facilitate the binding process.

transcription factor

combination of the hormone and its receptor

messenger ribonucleic acid (mRNA)

when the hormone-receptor complex binds to the hormone-response element, it regulates the transcription of specific molecules

Membrane-bound receptors

have peptide chains that are anchored in the phospholipid bilayer of the plasma membrane

1. Some receptors alter the activity of G proteins at the inner surface of the plasma membrane

2. other receptors directly alter the activity of intracellular enzymes.

Membrane-bound receptors activate responses in two ways

Second messengers

Chemicals produced inside a cell once a hormone or another chemical messenger binds to certain membrane-bound receptors. They activate specific cellular processes inside the cell.

second-messenger system

This mechanism is usually employed by water-soluble hormones that are unable to cross the target cell’s membrane.

1. alpha

2. beta

3. gamma

3 subunits of G proteins

G proteins

are so named because one of the subunits binds to guanine nucleotides.

Membrane-Bound Receptors That Activate G Proteins

G Proteins That Interact with Adenylate Cyclase

adenylate cyclase

an enzyme that converts ATP to cAMP

phosphodiesterase

breaks down cAMP to AMP. Once cAMP levels drop, the enzymes in the cell are no longer stimulated.

second messengers

produce an almost instantaneous response because it influences existing enzymes. In other words, the response proteins are already present.

amplification

The process in which a single hormone activates many second messengers, leading to the production of an enormous amount of final product.

second­-messenger amplification

produce an almost instantaneous response because the second messenger influences existing enzymes. In other words, the response proteins are already present.

Endocrine System

consists of ductless glands that secrete hormones into the interstitial fluid.

Endocrine glands

orangs in the body with the richest blood supply

pituita

phlegm or thick mucous secretion

hypophysis

hypo, under + physis, growth

pituitary gland

is also called the hypophysis. It rests in a depression of the sphenoid bone inferior to the hypothalamus of the brain

Pituitary gland

A small gland located below the hypothalamus that controls the functions of many other glands in the body and secretes hormones that influence growth, kidney function, birth, and milk production.

Hypothalamus

An important autonomic nervous system and endocrine control center of the brain located below the thalamus.

infundibulum

The pituitary gland lies posterior to the optic chiasm and is connected to the hypothalamus by a stalk called the

1. anterior pituitary

2. posterior pituitary

two parts of the pituitary gland

Anterior pituitary

The front part of the pituitary gland, made up of epithelial cells derived from the embryonic oral cavity.

Posterior pituitary

The back part of the pituitary gland, an extension of the brain composed of nerve cells.

pituitary gland

also secretes hormones that influence growth, kidney function, birth, and milk production by the mammary glands.

pituitary gland

was known as the body’s master gland because it controls the function of so many other glands.

1. hormonal control

2. direct innervation

hypothalamus controls the pituitary gland in two ways