Term
| What is the functional unit of the kidney? |
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Definition
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Term
| What are the two types of nephrons and what distinguishes them? |
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Definition
1. Cortical (mostly in cortex)
2. Juxtamedullary (long loop of Henle extends down into inner medulla) |
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Term
| Name the sections of the nephron in the order that the filtrate passes through them. |
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Definition
| Bowman's capsule, Proximal convoluted tubule, Loop of Henle (descending and ascending limbs), Distal convoluted tubule, collecting duct |
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Term
| What are the "vasa recta"? |
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Definition
| This is a special name for the long peritubular capillaries that extend down to the inner medulla, surrounding long loops of Henle and collecting ducts |
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Term
| What percent of the blood passing through the kidney is filtered? |
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Definition
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Term
| How is the net filtration pressure out of the glomerulus calculated and what value is it typically? |
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Definition
Capillary pressure - (hydrostatic pressure of filtrate in tubule + colloid osmotic pressure)
10 mmHg |
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Term
| What are the three intrinsic pathways by which glomerular filtration is regulated? |
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Definition
| Myogenic regulation, tubuloglomerular feedback, and mesangial control |
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Term
What is myogenic control of glomerular filtration?
How would this system respond to an increase in blood pressure? |
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Definition
Constriction/dilation of the afferent arteriole
The arteriole would sense stretch if blood pressure increased and would respond by constricting |
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Term
| What components are involved in tubuloglomerular feedback of glomerular filtration? |
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Definition
| The juxtaglomerular apparatus, which consists of macula densa cells in the distal tubule and juxtaglomerular cells in the afferent arteriole. |
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Term
| What do macula densa cells control? |
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Definition
| The diameter of the afferent arteriole |
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Term
| How does mesangial control affect GFR? |
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Definition
| It alters the permeability of the glomerulus |
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Term
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Definition
| The initial filtrate in Bowman's capsule. It is isosmotic to blood. |
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Term
| Glucose is reabsorbed via secondary active transport along with what ion? |
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Definition
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Term
| Why is Inulin useful in determining GFR? |
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Definition
| It is not reabsorbed or secreted |
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Term
| What equation can be used to calculate GFR when the amount of Inulin in blood plasma (Pin), the concentration of inulin in the urine (Uin), and the rate of urine production (V) are known? |
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Definition
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Term
| Where in the nephron does most of the solute and water reabsorption take place? |
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Definition
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Term
How does the descending limb of the Loop of Henle differ from the ascending limb?
What effect does this difference have? |
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Definition
Descending: Water permeable
Ascending: Water impermeable
This establishes an osmotic gradient from cortex to medulla. |
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Term
| Sodium reabsorption is regulated by aldosterone in what part of the nephron? |
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Definition
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Term
| Where is reabsorption completed for most solutes? |
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Definition
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Term
| The epithelial water permeability of the collecting duct is regulated by what hormone? |
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Definition
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Term
| How does vasopressin (ADH) affect the collecting duct? |
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Definition
| It makes it more permeable to water |
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Term
| What type of hormone is vasopressin (ADH)? |
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Definition
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Term
Where is ADH produced?
Where is it released? |
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Definition
Hypothalamus
Posterior pituitary gland |
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Term
What stimulates the release of vasopressin?
What inhibits its release? |
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Definition
Stimulates: Increasing plasma osmolarity detected by osmoreceptors in the hypothalamus
Inhibits: Increasing blood pressure detected by stretch receptors in the atria and baroreceptors in the carotid and aortic bodies |
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Term
| When is renin secreted (general)? |
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Definition
| When the blood pressure or GFR is lower than normal |
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Term
| Renin is secreted by what cells? |
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Definition
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Term
| The secretion of renin is controlled in what three ways? |
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Definition
1. Baroreceptors in juxtaglomerular cells release renin in response to low blood pressure
2. Sympathetic neurons in cardiovascular control center of medulla oblongata trigger renin secretion in response to low BP
3. Macula densa cells in distal tubule respond to decreases in flow by releasing a paracrine signal that induces juxtaglomerular cells to release renin
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Term
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Definition
| Converts angiotensinogen to angiotensin I |
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Term
What converts angiotensin I to angiotensin II?
Where is it found? |
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Definition
Angiotensin converting enzyme (ACE)
On the epithelia of blood vessels |
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Term
| What function does Angiotensin II have? |
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Definition
| It causes the synthesis and release of aldosterone from the adrenal cortex |
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Term
| What type of hormone is aldosterone? |
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Definition
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Term
| What else stimulates the production and secretion of aldosterone? |
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Definition
| Increases in circulating K+ |
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Term
| What cells does aldosterone target and what does it do? |
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Definition
Targets cells in the distal tubule and collecting duct
Stimulates Na+ and water reabsorption from the urine (thereby increasing blood pressure by increasing blood volume)
Enhances K+ excretion |
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Term
| How does Angiotensin II increase blood pressure? |
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Definition
| It is a vasoconstrictor and increases blood pressure by increasing resistance |
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Term
| Where does aldosterone act in the distal tubule epithelial cells and what does it do? |
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Definition
It diffuses into the cell and acts in the nucleus on the cell's DNA (steroid hormone)
It acts to insert sodium channels and provide energy to fuel sodium pumps |
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Term
| What hormone regulates thirst? |
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Definition
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Term
| Where does ADH act on the cells of the collecting duct? |
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Definition
| Membrane receptors (peptide hormone) |
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Term
Where is Atrial Natriuretic Peptide (ANP) produced?
It is secreted in response to what stimulus? |
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Definition
The atria of the heart
Stretch associated with increased blood volume |
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Term
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Definition
Increases urine output (consequently lowering blood volume and pressure)
Increases excretion of Na+ in urine (acts as an antagonist to the RAA pathway)
Increases GFR by relaxing contractile cells that control the size of filtration slits in the glomerulus
Inhibits secretion of vasopressin |
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Term
| Name the two general types of diuretics and give the location where each has its action. |
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Definition
Loop diuretics - Act on the Na+/K+/2Cl- symporter in the thick ascending limb of the loop of Henle
Distal tube diuretics - Distal convoluted tubule |
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Term
| What effect does a loop diuretic have and how does it achieve that effect? |
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Definition
Decreased blood volume and pressure
Inhibits sodium and Chloride reabsorption
Disrupts the creation of a hypertonic renal medulla
Without a concentrated medulla, water has less of a driving force to leave the collecting duct system
Increased urine production |
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Term
| What is the effect of a distal tube diuretic? |
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Definition
Inhibits the sodium-chloride symporter in the distal convoluted tubule.
Causes a retention of water in the urine |
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Term
| What three systems regulate GI function? |
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Definition
| Enteric nervous system, autonomic nervous system, and endocrine system |
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Term
| The enteric nervous system consists of what two nerve plexi? |
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Definition
Myenteric nerve plexus
Submucosal nerve plexus |
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Term
| What are the three motility patterns in the gut and what is the function of each? |
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Definition
Peristalsis: Propulsion
Rhythmic segmentation: Mixing
Tonic contraction: (Sphincters) Compartmentalization, blocking passages, maintaining pressure |
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Term
| The major gastrointestinal hormones are all what type of hormone? |
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Definition
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Term
| What stimulates the release of gastrin from G-cells in the stomach? |
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Definition
| Peptides and amino acids in the stomach, gastric distension, vagal input |
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Term
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Definition
| Stimulates gastric secretions (acid and pepsin) |
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Term
Where is cholecystokinin (CCK) produced?
What stimulates its production/secretion? |
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Definition
I-cells of the duodenum
Peptides, aminoacids, fatty acids in the duodenum |
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Term
| What does cholecystokinin (CCK) do? |
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Definition
Stimulates gall bladder contraction (bile)
Stimulates pancreatic enzyme secretions
Inhibits gastric emptying |
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Term
Where is secretin produced?
What does it do?
What stimulates its production/release? |
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Definition
S-cells in the duodenum
Stimulates: Pancreatic HCO3- secretion and inhibits gastric acid secretion
Stimulated by: Acid in the duodenum |
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Term
Where is GIP produced?
What does it do?
What stimulates its release? |
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Definition
K-cells in the duodenum
Stimulates insulin secretion from the pancreas
Glucose, aminoacids, fatty acids in duodenum |
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Term
| Gastric juice is secreted from _____ glands. |
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Definition
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Term
| HCl in the stomach is secreted by what type of cells? |
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Definition
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Term
| What else do parietal cells secrete (other than HCl)? |
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Definition
| Intrinsic factor (vitamin B12 absorption) |
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Term
| What do chief cells secrete? |
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Definition
| Pepsinogen (precursor for pepsin) and lipase |
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Term
| What enzyme is associated with the production of H2CO3 from CO2? |
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Definition
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Term
How do parietal cells generate hydrogen ions?
What does it do with those hydrogen ions?
Where does Cl- come from to make HCl? |
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Definition
CO2 => H2CO3 => dissociates into => HCO3- and H+
It pumps them into the lumen of the stomach in exchange for K+ ions witha H+/K+-ATPase Pump
Cl- ions are pumped into the cell from the blood in exchange for HCO3- and are then exported into the lumen of the stomach. |
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Term
| What are the three phases of gastric secretion regulation? |
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Definition
| Cephalic phase, gastric phase, intestinal phase |
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Term
| What are the two means by which the vagal nerve stimulates gastric secretion during the cephalic phase? |
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Definition
Direct vagal stimulation of parietal cells
Indirect stimulation via stimulation of G-cells (to produce gastrin) |
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Term
| What do gastric chief cells secrete? |
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Definition
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Term
| Where are intercalated duct cells found and what do they produce? |
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Definition
In the pancreas
Aqueous alkaline juice (containing bicarbonate to neutralize stomach acid) |
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Term
| What do acinar cells produce? |
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Definition
| zymogen vesicles containing digestive enzymes (in an inactive precursor form) |
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Term
| What happens to the pro-enzymes contained in zymogen vesicles? |
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Definition
| They are secreted into the duodenum where they are converted into active enzymes by trypsin |
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Term
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Definition
| It's produced from trypsinogen by enteropeptidase of the duodenal brush-border |
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Term
| What two hormones regulate the exocrine pancreas' secretions and where is each produced? |
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Definition
Secretin: S-cells of the duodenum
Cholecystokinin (CCK): I-cells of duodenum and jejunum |
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Term
| What does secretin stimulate? |
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Definition
| The secretion of alkaline aqueous secretion from pancreatic duct cells |
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Term
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Definition
| The secretion of zymogen vesicles by acinar cells |
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Term
| What do hepatocytes produce bile from? |
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Definition
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Term
| What is the function of bile? |
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Definition
| Aids in the absorption of lipids from the small intestine into the blood stream |
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Term
| What three components does bile contain? |
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Definition
Ions (Na+, K+, Ca2+, Cl-, HCO3-)
Bile salts
Bilirubin |
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Term
| What regulates the release of bile from the gall-bladder into the small intestine? |
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Definition
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Term
| What are the absorptive cells of the small intestine called? |
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Definition
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Term
| What cells secrete mucus into the small intestine? |
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Definition
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Term
Where is the absorption of sugars (saccharides) completed?
How does the absorption of fructose differ from that of glucose and galactose? |
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Definition
In the jejunum
Fructose absorption is a passive process, while glucose and galactose use secondary active transport (cotransport) |
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Term
What is the name of the transporter that facilitates the absorption of glucose? What ion does it use?
How does glucose leave the enterocyte? |
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Definition
sodium-glucose transporter 1 (SGLT 1)
Uses the sodium gradient as a force (transports two Na+ and one glucose into the cell)
Leaves the cell via facilitated diffusion through the basolateral membrane |
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Term
| Where does most of the absorption of peptides and aminoacids take place? Describe the method of transport into and out of the enterocytes. |
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Definition
jejunum and duodenum
Co-transport (secondary active transport) using H+ gradient as a force to get aminoacids into the cell
Facilitated diffusion out of the basolateral membrane of the cell |
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Term
| The portions of the pancreas that secrete hormones (endocrine) are called what? |
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Definition
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Term
| What are the two major hormones produced by the endocrine pancreas and what type of cells is each produced by? |
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Definition
Insulin - Beta cells
Glucagon - Alpha cells |
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Term
What do delta cells in the endocrine pancreas produce/secrete?
What does it do? |
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Definition
Somatostatin
Inhibits insulin/glucagon secretion |
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Term
| How does glucose directly regulate the secretion of insulin from beta cells? |
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Definition
1. Glucose is transported into the beta cell by the GLUT-2 transporter
2. Glucose is metabolized in the cell to produce ATP
3. ATP closes ATP-sensitive K+ channels
4. The beta cell membrane becomes depolarized
5. The depolarization opens voltage-gated Ca2+ channels
6. Ca2+ influx into the cell
7. Increased intracellular calcium causes exocytosis of insulin-containing vesicles |
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Term
| Describe the structure of insulin. How is it created? |
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Definition
2 amino acid chains linked by two bisulfide bridges
Synthesized as preproinsulin (4 peptides). Then, two of the peptides are cleaved off (C-peptides). These are packaged along with insulin in vesicles. |
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Term
| What are the major effects of insulin on its target cells in regards to glucose? |
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Definition
1. Increase the number of GLUT-4 glucose transporters in the membrane (so that more glucose can be removed from the blood stream into cells)
2. Promote the formation of glycogen from glucose in liver and muscle cells
3. Inhibition of glycolysis (the breakdown of glycogen)
4. Inhibition of gluconeogenesis (production of glucose by the cell) |
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Term
| Describe the structure of an insulin receptor |
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Definition
Two alpha subunits (bind insulin)
Two Beta subunits (cross the membrane and connect to secondary messenger systems) |
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Term
| What effects does insulin have on fatty acid metabolism? |
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Definition
1.Inhibition of mobilization and oxidation of fatty acids (lipolysis)
2.Increase in storage of fatty acids in form of neutral fat
3.Inhibition of ketoacid (beta-hydroxybutyric acid & acetoacetic acid in liver)
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Term
| What effects does insulin have on aminoacid metabolism? |
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Definition
1.Increase in aminoacid and protein uptake into tissue (muscle)
2.Increase in protein synthesis
3.Inhibition of protein degradation
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