DAT Biology: Endocrine System, Digestive System, Excretory System

Main Hormone Types (3)

1. Peptide Hormones

2. Steroid Hormones

3. Amino Acid Derived Hormones

How to peptide hormones pass along their signals?

Proteins are large and polar, water soluble, flow through blood but NOT lipid soluble so they cannot pass through a cellular membrane

Bind to cell surface receptors rather than through cellular membranes

Goes through indirect stimulation (hormone is not directly binded to the receptors)

IP3/DAG Pathway

Regulates the release of stored Ca2+ from th eER into the cell cytosol

1. Pathway activated when peptide hormone binds the GPCR

2. GPCR activates the associated G protein via the binding of one GTP molecule

3. G protein activates the enzyme phospholipase C

4. Activated phospholipase C cleaves the lipid PIP2 into 2 separate secondary messengers (IP3 and DAG)

5. IP3 binds ligand gated Ca2+ channels on the surface of the ER

6. ER calcium channels open, releasing Ca2+ into the cytosol

7. Free Ca2+ goes on to affect multiple other pathways

Steroid Hormones Process

Based on cholesterol, so they are lipophilic, able to directly pass through a cellular membrane (lipid, not water soluble, so needs a water soluble transport protein to travel through the blood)

Directly binds intracellular receptors of the cytoplasm or the nucleus, resulting in steroid-receptor complexes directly binding DNA to affect transcription

Cause slow and gradual genetic change, directly stimulating

Polar-Water Soluble Amino Acid-Derived Hormones

Epinephrine and nonepinephrine

Secondary Messengers Relaying Signals from Cell Surface Receptors to Effector Proteins

cAMP, IP3, DAG, Ca2+

Anterior Pituitary Gland Stimulating Hormones — Hypothalamic Releasing Hormones

GnRH, TRH, CRH, and GRH

Anterior Pituitary Gland Hormones

Hormones released by the anterior pituitary gland once stimulated

Tropic and direct hormones

Tropic Hormone Examples

FSH (Follicle Stimulating Hormone)

LH (Lutenizing Hormone)

ACTH (Adrenocorticotorpic Hormone)

TSH (Thyroid Stimulating Hormone)

Direct Hormone Examples

Prolactin, Growth Hormone (Somatotropin)

Mneumonic for Anterior Pituitary Gland Hormones

FLAT PIG

F: Follicle Stimulating Hormone (FSH)

L: Lutenizing Hormone (LH)

T3 and T4 Similarities

Thyroid Gland Hormones

Released in response to TSH stimulation from the anterior pituitary, derived from the amino acid tyrosine, negative feedback effect on TSH and TRH secretion

Thyroid Disorders

Hypothyroidism, Hyperthyroidism

Goiter from Hypo and Hyperthyroidism

1. Hypothyroidism: Low T3 and T4: Oversecretion of TRH to compensate for missing T3 and T4 = enlarged thyroid gland

2. Hyperthyroidism: High T3 and T4: hyperactive thyroid gland = enlarged thyroid gland

Endocrine Islets of Langerhans Releasing

Secretion of the peptide hormones glucagon, insulin, and somatostatin

• Glucagon: released by alpha cells

• Insulin: released by beta cells

• Somatostatin: released by delta cells

Insulin Process

Peptide hormone associated with RTKs

Resulting second messengers trigger the release of glucose transporters along the cellular membrane

Glucose flows out of the blood and into cells via the glucose transporters, decreasing blood glucose levels

Adrenal Gland General Anatomy

Bodies house 2 distinct adrenal glands (adrenal cortex and adrenal medulla), each associated with the superior surface of one of the body’s kidneys

Overall adrenal gland function is associated with stress combatting

Steroids vs. Amino Acids

Steroids: lipid soluble

Amino Acids: not as lipid soluble, use signal transduction pathways, transmitting signals faster

How to get hormones to the testes and ovaries?

Anterior pituitary gland producing tropic/direct hormones

LH and FSH — tropic hormones targeting the testes in males and ovaries in females

Hypothalamus releasing a hormone known as gonadotropin (GnRH) stimulating the release of other hormones

Creates estrogen and progesterone in ovaries, while it creates testosterone in testes

Human Digestive System Accessory Organs

Pancreas, liver, gallbladder

Aid digestive system, but not in the digestive system

Two Openings of the Human Digestive Tract

Mouth and Anus

Two Key Structures of the Stomach

Sphincters

Cardiac Sphincter, Pyloric Sphincter

Why do we have an inactive enzyme precursor for gastric pits in stomach cells and not just have an enzyme that breaks stuff down?

It will go ahead and break down the proteins of the chief cells itself if it is an enzyme breaking stuff down, which may degrade our own stomach cells

Therefore, we keep them in a dormant state (zymogen) and release them, interacting with an activator like stomach acid, activates them and targets env

Trip Through Stomach

Food Ball Here Through Esophagus → Cardiac Sphincter (making sure we have no backup problems) → Stomach where gastric lipase is gonna break down fats, pepsin is gonna activate + interacts with the gastric juices + breaks down proteins → churning and mechanical digestion breaks down food as well → turn food into chyme, exiting through the phyloric sphincter → deposit into the first part of the small intestine (duodenum)

Responses to Chyme Entering the Duodenum

Small intestine and digestive system accessory organs (pancreas, gallbladder, liver) work together to properly respond to and process acidic chyme from the stomach

How the Small Intestine Responds to Chyme

Releases hormone cholecystokinin (CCK) when proteins/fats are recognized in the duodenum

• Slows the amount of chyme exiting the stomach and entering the duodenum (slowing gastric emptying)

• Stimulate pancreas to release digestive enzymes

• Stimulate gallbladder to release bile

• Release hormone secretin: stimulates pancreas to release bicarbonate ion

Pancreas Response to Chyme

Releases digestive enzymes due to stimulation by the hormone CCK

• Pancreatic Amylase: digests carbs (starch into maltose)

• Tripsin and Chymotrypsin: proteases (digests proteins)

  • Released as trypsinogen and chymotrypisogen zymogens

  • Enteropeptidase converts trypsinogen to trypsin, trypsin converts chymotrypsinogen to chymotrypsin

• Secretes HCO3- (bicarbonate ion) due to secretin because it is basic and nuetralizes the highly acidic environment

Liver Responses to Chyme

Produces bile which emulsified fats, important for the absorption of fats

Gallbladder Responses to Chyme

Stores and concentrates bile from the liver, releasing bile into the duodenum when stimulated by CCK

Mnemonic for Liver Functions

PUSH DOG

1. Protein Synthesis

2. Urea Synthesis

3. Storage

4. Hormone Synthesis

5. Detoxification

6. Glucose and Fat Metabolism

Liver Detoxification

Metabolizes chemicals/drugs in the blood to detoxify body

1. Detoxification Byproducts: Bile → Intestines ; Urea → Kidneys

2. Kupffer Cells: phagocytes of the body

Liver Function: Glucose Metabolism

1. Glycogenesis: creates glycogen from glucose monomers

2. Glycogenolysis: breaks down glycogen into glucose monomers

3. Gluconeogenesis: creates glucose from glycerol and amino acids

Liver Function: Protein Metabolism

Synthesis of Plasma Proteins from Amino Acids: creation of albumin and blood clotting factors

Conversion of Ammonia → Urea: Converting the dangerous byproduct of protein metabolism into a safer version for excretion

Structures of the Large Intestine

Functions of the Large Intestine

1. Water absorption

2. Mineral (salt absorption)

3. Vitamin production and absorption (reliant on a mutualistic relationship with certain bacterial species)

NOT nutrient absorption (SMALL intestine)

Microbiome Bacteria Responsbility

1. Produce B and K vitamins

2. Metabolism of Biel Acid (key indication of healthy intestinal microbiome)

3. Fermentation of fiber

Where is water reabsorbed

Kidney

Kidney Structure

1. Outer Cortex

2. Inner Medulla

Kidney Key Functions

1. Regulation of blood pressure

2. Regulation of pH

3. Stimulate generation of red blood cells

Nephron Main Structures

1. Glomerulus

2. Proximal convoluted tube

3. Loop of Henle

4. Distal convoluted tube

5. Collecting Duct

Pathway of Urine Post-Nephron

Collecting Duct → Renal Pelvis → Ureter → Bladder → Urethra

Angiotensin II: How does it do what it does?

Increases blood pressure and volume

1. Stimulates additional aldosterone release

2. Increases Na+ reabsorption at the proximal tubules (water follows, increasing bp)

3. Systemic vasoconstriction, condensing the vessels to increase pressure

4. Increase thirst, increasing liquid intake

Atrial Natriuretic Peptide (ANP): How does it do what it does

Reduces blood pressure and volume

1. Increasing the glomerular filtration rate (GFR): filters more fluid from the blood into the kidneys, and since the kidneys cannot reabsorb all the extra fluid, it excretes into urine, reducing blood volume

1. Decreasing sodium reabsorption so less water follows so less pressure overall

2. Increasing sodium excretion so more water follows and leaves through urine

3. Inhibiting renin and the renin-angiotensin-aldosterone-system so that you don’t increase pressure through angiotensin II

B. Increased levels of aquaporin channels at the collecting duct is not a direct effect of Angiotensin II. This action is primarily mediated by ADH (vasopressin), whereas Ang II directly causes sodium reabsorption, aldosterone release, and vasoconstriction.

ADH is responsible for water movement

Explain Osmoregulation/Adaptations of Marine (Saltwater) Fish

Hypotonic to their environment, so environment has higher solute concentration, and passive water loss to the environment, they are lower concentration than surroundings

Adaptations: constant drinking, rare urination, secretion of salt through the gills

Explain Osmoregulation/Adaptations of Freshwater Fish

Hypertonic to their environment, environment has a lower solute concentration so passive water gain from environment and water moves into the fish

Adaptations: rarely drink water, constant urination, absorption of salt through their gills