Final Exam Flashcards
Cystic fibrosis
Caused by a genetic mutation in the cystic fibrosis transmembrane regulator. This results in the building up of chloride inside the cell (which makes the cell more negative) and results in the reduction in the extracellular removal of cations –> causes water retention due to loading of ions. This causes a mucosal build up in the respiratory and digestive tract.
How does calcium move into the blood stream in a fresh water fish?
Ca moves passively into MRC and then can move into the blood circulation either through a Ca cotransporter on the basolateral membrane that transporter 1 Na in and 1 Ca out or through a calcium ATPase on the basolateral membrane that moves calcium into the blood stream.
How are marine animals able to gain water by drinking sea water?
They can actively transport 97% of the consumed NaCl into their blood stream, thereby favouring the movement of water into the blood stream along with them. They can then excrete these ions via the GILLS. We can’t drink salt water because we can’t actively transport enough ions into the blood plasma to get a favourable movement of water… we also don’t have a means of removing these ions.
NKCC Cotransporter
Transports one sodium, one potassium and two chloride ions into the cell from the blood circulation. It used the driving force of sodium moving down it’s concentration gradient to provide the energy for the transport of the other ions. The result is a build up in chloride inside the cell. The chloride will actually build up to a high enough [ ] that is will move passively out of the cell
What is so special about Elasmobranchs in terms of osmolarity regulation?
They are osmotic conformers but ionic regulators. They regulate concentrations of sodium and chloride but still their overall osmolarity matches that of the environment. They match the marine osmolarity by having high concentrations of both urea and trimethylamine N-oxide (organic solutes)
What is the renal corpuscle?
Bowman’s capsule + the glomerulus (blood vessels inside)
Afferent vessel
brings blood from the renal artery to the nephron and to the Bowman’s capsule
Efferent vessel
Brings blood out of the glomerulus to the renal vein
colloid osmotic pressure
The osmotic pressure caused by the solutes dissolved in bowman’s capsule. Slows down the rate of solute transfer from the plasma to the capsular fluid (higher the [solute] in bowman’s capsule, higher the colloid osmotic pressure and thus the slower the filtration rate into BC
Capsular fluid hydrostatic pressure
Hydrostatic pressure from the fact that the nephron and bowman’s capusle are full of a fluid and it is a fixed container. Adding a fluid to this fluid filled container – opposes fluid movement into BC
Permeability of descending thin segments
highly permeable to water and moderately permeable to most solutes
permeability of ascending thin segments
impermeable to water and moderately permeable to most types of solutes
Ascending thick segments
impermeable to water, active transport of Na and Cl
Single effect
The creation of a transverse osmotic pressure gradient based on the action of one pump, the sodium potassium ATPase on the cells of the thick ascending limb wall.
Transverse osmotic pressure gradient
Created by the Single Effect. Sodium is actively transported into the interstitium by the cells on the thick ascending limb. Water will move out of the descending limb walls, into the interstitium and Na and Cl will move into the descending limb. The effect is high solute concentration in the descending limb and interstitium, and lower concentration in the ascending limb - also the walls of the ascending limb are impermeable to water.
How is the release of ADH regulated?
Baroreceptors detect levels of blood plasma. Baroreceptors are located in the pulmonary venous system, cardiac atria, aortic arch, and carotid sinus. They are stretch activated receptors that reduce their firing with decreases in blood plasma volume (Less stretch)- but as they decrease in stretch, they change their firing frequency which stimulates the hypothalamus/pituitary gland to release ADH
There are also osmoreceptors in the hypothalamus that change their firing frequency in response to changes in osmolarity via shrinking / swelling. The amount of shrinking vs swelling will cause the hypothalamus to change the amount of ADH released.
What receptor does ADH activate on the cells lining the collecting duct wall?
Vasopressin receptor on the basolateral membrane (i.e. facing the blood/interstitial fluid)
How does ADH increase water absorption?
ADH presence will result in increased permeability of the collecting duct walls to water, thus increasing water reabsorption. ADH will bind to the vasopressin receptor –> which causes activation of adenylyl cyclase which in turn produced cAMP which activates protein kinase A. Protein kinase A, now activated, will initiate the exocytosis of aquaporin-water containing vesicles. The exocytosis of these will place aquaporin 2 proteins in the apical membrane of the collecting duct walls, thus allowing water to be absorbed from the tubular fluid.
What is the permeability of urea like in the nephron?
In the proximal, distal convoluted tubule, thick ascending loops of Henle –> permeability is very low
There is high urea permeability in the lower part of the collecting duct and the bottom of the loop of Henle (inner renal medulla)
What are the four basic processes of digestion?
Motility, Secretion, Digestion, Aborption``
Gut associated lymphoid tissue
GALT - produces immune cells that survey and protect the gastrointestinal regions. These immune cells function in adaptive and innate immunity. Respond to and protect from pathogens entering the body. 80% of immunoglobulin producing cells are in the small intestine
What are the parts and functions of the human stomach?
fundus: mostly functions to store food prior to digestion
body: where most of the digestion takes place
antrum: where chyme is stored.
What are disinfectant and protection characteristics of the stomach?
mucus, enzymes, acid
What does chyme consist of?
Bolus (ball of food) and gastric juices (enzymes and acids)
Why must the stomach be a low pH?
Because the enzymes produced to help break down proteins into smaller peptides function most optimally at a LOW pH (highly acidic environment)
Where does most digestion occur in a human?
Most digestion takes place in the small intestine. More specifically, in the duodenum.
What are the parts of the small intestine?
duodenum, jejunum, illeum.
How does the stomach increase it’s surface area?
There are rugae in the stomach. These foldings are inwards so that more of the cells are away from the corrosive lumen with potent enzymes within.
How does the intestine increase it’s surface area?
There are plicae in the intestine. Because their function is to absorb food products, they are outfoldings that stick out into the lumen. There are also microvilli on the enterocytes that further function to increase the SA.
What are the four layers of the GI tract wall?
Mucosa, submucosa, muscularis, serosa
What does the mucosal layer consist of?
Single line of epithelial cells, lamina propria, thin layer of muscle cells – muscularis mucosae. The single line of epithelial cells is the most variable part of the GI tract lining.
Parietal cells
Secrete HCl into the gastric lumen (stomach). These cells have proton ATPase pumps and carbonic anhydrase enzymes. HCl (acid) is very important for protein digestion. Secretes intrinsic factor which binds to vitamin B12 that can be absorbed into the small intestine.
Chief cells
Secrete pepsinogen, a zymogen. Pepsinogen gets converted into pepsin in the stomach lumen where it can then function to help breakdown proteins. Chief cells also secrete gastric lipase
G cells
cells of the stomach epithelial lining which produce a hormone called gastrin. Gastrin is secreted into the extracellular space and taken into the blood stream. It acts on cells which have a gastrin receptor and stimulates the release of pepsinogen and HCl from the chief and parietal cells. Gastrin also acts on enterochromafin-like cells to release histamine
What are the epithelial cells in the intestine?
Absorptive cells, endocrine cells, goblet cells, other secretory cells (i.e. mast cells secreting histamine)
What are the epithelial cells in the stomach mucosa?
mucus cells, parietal cells, chief cells, G-cells. Mucus cells secrete mucus that protects the cells lining the stomach.
What are goblet cells?
Cells in the epithelial lining of the mucosal lining in the stomach that function to secrete mucus, similarly to the mucus cells in the stomach.
How do the junctions between cells differ between the stomach and the intestine?
The stomach has tight junctions that protect from gastric juices getting into the tissues and the intestine has leaky junctions where stuff can slip through.
Lamina propria
Part of the mucosal layer. It is subepithelial connective tissue that contains nerve fibres, blood and lymphatic vessels, wondering immune cells like macrophages and lymphocytes.
Where do the absorbed intestinal food products enter the circulation?
In the lamina propria layer of the mucosal lining in the intestine.
Lymphatic vessel
In the lamina propria layer. Essential for fat absorption as the fats absorbed do not immediately enter the circulation but instead enter the lymphatic system. This vessel has immune cells present that survey for pathogens trying to enter the body. These immune cells are more abundant in the intestine as the stomach has other mechanisms that control the invading of pathogens.
Peyer’s Patches
Collections of lymphoid tissue/lymphoid modules which produce lymphocytes. Sends ‘messages’ to other lymphoid tissues to protect body from microbes.
muscularis mucosa
third layer of the mucosal lining of the GI tract. It is a thin layer of smooth muscle. It can contract and relax to alter the effective surface area of the GI tract. More important role in the small intestine. It can increase exposure of the digested products to the brush border membrane (enzymes and absorption)
What controls the muscularis mucosa?
Both the nervous AND the endocrine system can control the contraction and relaxation of the smooth muscle.
Control can be through the nervous plexus within the submucosal layer
Oblique muscles
A third layer of muscle, in addition to the circular and longitudinal muscles, found in the submucosal layer of the STOMACH and aids in the churning process - mixing of the bolus of food and gastric juices.
Serosa
Single squamous epithelium - connective tissue layer that is continuous with the visceral peritoneum - the peritoneal membrane that is lining the abdominal cavity. A sheet that holds the GI tract in place! It is connected to layers of the mesentaries/in some areas it is continuous with the mesentaries.
How do the parasympathetic nervous system and the sympathetic nervous system each affect the GI tract?
Parasympathetic NS - excitation (motility)
Sympathetic NS - inhibition (motility)
What is peristalsis?
Example of a PHASIC contraction. It functions to move food forward in the digestive tract. This task is mediated by the contraction of circular muscles and the relaxation of the muscles in the forward area
What is the purpose of segmental contractions?
To mix the food in the intestine. This is an example of a phasic contraction.
trypsinogen
zymogen that is a pancreatic exocrine secretion. Once activated in the lumen, it can cleave peptides into amino acids
What are the exocrine secretions of the pancreas?
Zymogens including: trypsinogen, chymotrypsinogen, procarboxypeptidase, procolipase, prophospholipase. These are all activated by active trypsin.
chymotrypsin
protein breakdown, activated by trypsin
colipase
important for activity of lipases. activated by trypsin
carboxypeptidase
breaks down peptide bonds
phospholipase
important for fat break down
parietal cell secretion
These acid producing cells have carbonic anhydrase and proton pumps! H20 and CO2 diffuse into cell and come together to form bicarbonate and H+. The bicarbonate is exchanged out of the cell into the blood circulation for a chloride ion via the bicarbonate-chloride exchanger. H+ is exchanged out into the lumen of the stomach (through the apical membrane) in exchange for a K+ ion - the K+/H+ ATPase. Thus both H+ and Cl- are secreted - thereby increasing the HCl in the lumen of the stomach. Because of the HCO3- being pushed into the blood, the blood becomes alkaline! This event is called the alkyline tide.
What are some factors that can increase acid secretion by the parietal cells?
- gastrin binding to gastrin receptors on the basolateral membrane of parietal cells
- histamine, produced by mast cells, has receptors on the basolateral membrane of parietal cells
- Acetylcholine binds to muscarinic receptors on the basolateral membrane of parietal cells.
amylase
Present in the saliva and the small intestine. It breaks down glucose polymers into disaccharides which are further broken down by other enzymes
maltose
2 x glucose, broken down by maltase
lactose
1 glucose and 1 galactose, broken down by lactase
sucrose
1 fructose and 1 glucose, broken down by sucrase
How is glucose absorbed?
It is absorbed into absorptive cells (epithelial intestinal cells) via a sodium glucose cotransporter. The Na+/K+ ATPase on the basolateral surface provides DF for sodium to want to move into the cell, bringing glucose with it. Glucose moves down it’s concentration gradient into the blood circulation via facilitated diffusion. It uses the GLUT2 transporter as a means to do so.
How is galactose absorbed?
Galactose can follow the exact same pathway as glucose
Fructose absorption
Fructose is absorbed into absorptive cells through the GLUT5 transporter (on the apical membrane). Once in the cell, it can go through the GLUT2 transporter, just like glucose and galactose.
endopeptidases
Protease (proteolytic enzyme) - Cleave the inner bonds of the peptide chain, giving rise to smaller peptide chain products. Cleave peptide bonds in the middle of the protein sequence
exopeptidase
Protease (proteolytic enzyme) - Cleave peptide bonds near the end of the peptide chain, giving amino acids as the products, plus maybe a few di or tri-peptides.
aminopeptidases
Target the amino end of the peptide molecule
carboxypeptidases
Target the carboxy end of the peptide molecule
amino acid absoroption
There are amino acid transporters on the apical membrane of absorptive cells. Amino acids are absorbed through a Na+/ amino acid symporter. Di and tripeptides are taken up typically through a H+/amino acid symporter. To enter the circulation, there is a Na+/ amino acid transporter on the basolateral membrane that is an ANTIPORTER. di and tri peptides can get into the circulation through an H+/amino acid antiporter
What is the primary source of fats we consume?
Triglycerides (90%)
What do lipases need in order to break down fats?
Bile, which is secreted from the liver and stored in the gall bladder
Colipase, which is secreted by the pancreas
These act to increase the surface area of the fat molecules to allow lipases to do their job.
What do lipases do?
They remove two fatty acids from triglycerides to give two free fatty acids and a monoglyceride that can the absorptive cells can then take in.
Lingual lipase
Released by the serous glands in the tongue. It breaks down triglycerides into 2 fatty acids and a monoglyceride. However only limited fat digestion occurs in the mouth.
Gastric lipases
secreted by the chief cells. These are also called acid lipases - they are functional at low pH levels. Break down triglycerides into fatty acids and monoglycerides.
Pancreatic lipases
Requires cofactors bile salts and colipase. Breaks down triglycerides into two free fatty acids and monoglyceride.
Bile salts
Bile acids combine with amino acids to form bile salts. Bile salts facilitate the enzymatic fat digestion by breaking fat into smaller molecules (increase SA).
Bile
contains salts, pigments, and cholesterol.
glucose dependents insulinotropic peptide
Secreted in response to glucose presence in the GI lumen. It acts on the pancreatic B-cells to release insulin
cholecystokinin CCK
Released in response to consumption of fats and proteins
- delays gastric emptying, gives more time for food digestion/absorption to occur at different parts
- Stimulates contraction of the gall bladder so that bile is released (helps in the digestion of fats)
- stimulates the exocrine pancreas to release proteases and lipases into the intestinal lumen to assist with digestion of fats and proteins.
Secretin
Released from cells lining the duodenum in response to the low pH of the incoming chyme from the stomach. Enteroendocrine cells release secretin into the circulation. Secretin binds to the exocrine pancreas which secretes bicarbonate into the intestinal lumen through a duct. Neutralizes the pH of the intestinal lumen.
enterostatin
Procolipase breaks down into colipase and enterostatin. Enterostatin gives the brain the sensation of feeling full and decreases fat consumption.
volume regulation
using water/salt concentrations to purposely swell/change volume. This can be done when invertebrates shed their old cuticle.
podocytes
Specialized epithelial cells on the capsular fluid side of the basement membrane separating the blood and the capsular fluid in Bowman’s Capsule. These cells have projections and they come together to form a mesh-like layer. These ensure that small dissolved solutes can pass but not large proteins.
slit diaphragms
Small openings between crossover areas of podocytes that allow small dissolved solutes to pass through =.
What allows an animals to have a higher U/P ratio?
Having an increased abundance of long loop nephrons (with long loops of Henle) AND having relatively long loops relative to the size of the kidney.
Where in the nephron is the permeability high to urea?
In the inner renal medulla (lower part of loops of Henle) and the lower parts of the collecting duct.
How are di/tri-peptides absorbed by epithelial cells?
Through a H+/amino acid symporter on the apical membrane of absorptive cells.
Nucleic acid digestion
Break down into nucleotides by pancreatic and intestinal enzymes. Furtherly broken down in bases and monosaccharides. Monosaccharides are absorbed via facilitated diffusion and bases are typically actively transported into absorptive cells.
How are minerals taken up?
Mostly taken up by active transport because they are moved against their concentration gradient
What hormones are part of the secretin family?
secretin, VIP, GIP, GLP-1
vasoactive intestinal peptide (VIP)
Secreted by cells of the enteric nervous system
enterochromafin cells
Release histamine in response to Ach. Histamine in turn activates parietal cells to secrete acid.
D cells
Present in the gastric mucosa (stomach). Increased acid in the lumen stimulates these cells to produce somatostatin. Somatostatin INHIBITS G-cells, ECL cells, and parietal cells. This gives a negative feedback loop!
peritonitis
Caused by a perforating ulcer. Inflammation of the peritoneum (serosal layer connecting to the abdominal cavity). This can be fatal.
How to decrease ulcers happening?
Inhibit proton pumps - omeprazole
Antacids, milk –> buffer the acid
Aspirin affect on the stomach
Aspirin and other non-steroidal anti-inflammatory drugs inhibit the production of mucus and bicarbonate in the stomach - can lead to erosion of the mucosal lining and cause stomach ulcers.
Vasa recta
Blood vessel that travels down into the renal medulla to to supply the nephron cells with oxygen and nutrients. Only about 1-2% of total renal blood flow travels through the vasa recta .
