Energy Balance Flashcards
Energy in equals…
Energy out
*bucket theory?
What is positive energy balance?
More energy coming in than going out
 what is negative energy balance?
More energy out than coming in
energy is…
The capacity to do work
Energy is…
The capacity to do work
What is the energy currency that cells use?
Adenosine triphosphate (ATP) 
ATP provides the “fuel” to perform what three types of work?
- Mechanical work (muscle contraction, ciliary and flagellar movement)
- Transport work (moving ions and other molecules across cell membranes, absorption and secretion)
- Chemical work (building molecules)
ATP is synthesize metabolically by cellular respiration. As a result, energy balance is centered around the….
Chemical reaction to synthesize ATP
C6H12O6 + 6(H2O) + 6(O2) ——> 6(CO2) + 12(H2O) + ATP + Heat 
Note that the metabolic process generates H2O and produces heat. Not our immediate concern but these are important for later topics related to fluid balance and thermal balance
What are the physiological systems needed to provide the “inputs” for cellular respiration?
• digestice system to provide glucose and other chemical intermediates
• accessory glands to aid the digestive system and digestive process
• endocrine and nervous system to regulate
• respiratory system to provide the O2 and eliminate CO2


Metabolic processes generate ____ and produce _______
H2O, heat
What are the four major layers of the G.I. tract?
- Mucosa
-  submucosa
- Muscularis externa
- Serosa
What does the mucosa (1) include?
Mucus membrane (epithelium) Lamina propria (connective tissue) Muscularis mucosa (smooth muscle)
What kind of tissue is the submucosa (2)? What is located here?
Connective tissue, the location of most glands
What is the muscularis externa composed of? What type of tissue is it?
- Circular muscle (diameter shrinkage)
- longitudinal muscles (length shrinkage)
Smooth muscle
What are the three main serosal membranes?
- Pleura
- Pericardium
- Peritoneum
All habe a visceral peritoneum (Serosa), this is what faces the organ
And parietal peritoneum
What are the four types of epithelial membranes? 
- Cutaneous (skin)- Epidermidis is the epithelial part, and dermis the connective tissue part
- Mucous membrane- wet membrane that faces the external environment of hollow structures of the body that connect to the surface
- Serosa membrane- wet membrane that lines closed cavities not connected to surface -two layers, parietal lines outer cavity and visceral lines outside of organs
What are the four main divisions of the digestive system?
- Motility-mix or move contents along
- Digestion- Breaking the bonds mechanically and chemically
- Secretion- enzymes, mucus
- Absorption- movement outside to inside the body ex: glucose, amino acids, fatty acids, water
Where are proteins mostly digested? Begin to be digested? 
Stomach
Where does most of the chemical digestion take place? 
Small intestine.
Taken into cells for fuel or to store energy
Digestion begins in the oral cavity by what two main mechanisms? 
- mastication-grinding and chewing of food with teeth mechanically
- salivary amylase- enzyme to digest starch into glucose
What are the regions of the stomach?
What are the two sphincters of the stomach?
-Fundus (top), body, atrium (bottom)
Lower Esophageal sphincter and pyloric sphincter
How much chyme is released into the small intestine at a time in order to slowly process nutrients
Only 1 mm at a time
What are the folds of the stomach called?
Rugae 
What are the main functions of the stomach?
• Control movement of chyme (chewed food mixed with gastric juice) into small intestine
• kill bacteria by low pH
• begin protein digestion (denature proteins by acid and low pH, and protein digestion by secreted proteolytic enzymes)

What are the important cells of the gastric mucosa?
Gastric glands
What protects the lining of the stomach from hydrochloric acid?
Neck cells that secrete mucus (located in gastric pits) 
What do chief cells secrete?
What do you parietal cells secrete?
Pepsinogen 
Acid 
What do G cells secrete? 
The hormone gastrin
What is the list of important cells in the stomach? 
-  neck cells
- chief cells
- parietal cells
- G cells
- gastic glands 
Acid secretion in the stomach is regulated by….
Parietal cells
What is the function of tight junctions?
Prevents inter-paracellular movement
(Think of plastic that goes around six pack of soda)
What is the function of acid in the stomach?
To denature proteins and facilitate protein digestion and kill bacteria
Parietal cell:
apical membrane…
Basolateral membrane…
Apical membrane: portion of the membrane faces lumen, the portion that forms tight junctions
Basolateral membrane:
zymogen…
Is an enzyme precursor, the protein you have left changes the function
- partially denatured pepsinogen (by HCL) has some proteolytic activity that cleave some pepsinogen into pepsin*
This is a long-term regulator of appetite that is produced by fat 
Leptin
Protease digests _______
Peotiens
Enzyme secretion in the stomach is regulated by _____ cells 
Chief
What are the two phases in the control of enzyme and acid secretion?
- Cephalic phase
2. Gastric phase 
What is the cephalic phase? 
Thought and smell of food stimulates parasipathetic neural inputs (ACh) to G-cells and parietal cells
a. ACh directly stimulates acid secretion from parietal cell
b. ACh stimulates gastrin secretion from G cell which in turn acts hormonally on parietal cells to simulate acid secretion
What is the gastric phase?
Once food is in the stomach, mechanically distention of the stomach and presence of proteins and protein breakdown products act on mechanoreptors and chemo receptors that in turn act through the enteric nervous system to further simulate both G-cells and parietal cells.  they also feedback to autonomic to further stimulate the parasympathetic nervous system. 
Most digestion and absorption of nutrients occurs in the…
Small intestine
____________ of the small intestine is particularly important because secretions from the gallbladder and pancreas make their way into the lumen by way of common bile duct and pancreatic duct respectively
Duodenium (most digestion happens here)
What does bile digest?
Fat (triglycerides) 
Pancreatic (exocrine) secretion of ___________ rich solution helps neutralize chyme coming from the stomach so digestive enzymes from the pancreas will work to digest fats, carbohydrates, and proteins
Bicarbonate 
What does the apical membrane of the small intestines have?
Brush border composed of microvilli*
The opposite side is the basolateral membrane
What are the three segments of the small intestine?
Duodenum, jejunum, ileum
The dips between villi are called…
Are they secretory or absorb?
Crypt of Lieberkühn
Euterocytes (secretory) 
What are the projections from the small intestine called? 
Is it secratory or absorptive?
Villi (on the villi is a bunch of microvilli)
Entrocytes (absorptive) 

What is the lymph vessel associated with the Villus called? What is its purpose?
Lacteal
Fat absorption
Where does the pancreatic duct and the CBD merge?
And what is the associated sphincter?
Ampulla of Vater 
Sphincter of Oddi
What are the endocrine associated cells of the pancreas?
What is the exocrine associated cells of the pancreas?
Islet cells (secrete hormones)
Aclinar cells (secrete enzymes), duct cells (secrete bicarbonate rich fluid)
How many glucose molecules are in maltose? And what kind of saccharide is it?
Two, disaccharide
What two enzymes digest carbohydrates in the small intestine?
 salivary amylase glands, and pancreatic amylase (secreted from exocrine pancreas) breakdown polysaccharides like glycogen and starch into maltose or “limit dextrins” 
What breaks down maltose into 2 glucose. 
Brush border enzymes (stuck in cell membrane) such as maltase
Glucose is absorbed into the mesenteric blood capillaries by ___________ Cotransport with _____
Secondary active, Na+
H2O always follows ________ transport by osmosis
Solute***
It does not matter where, it always happens! 
What is primary active transport?
- pump; ATP used to move solute “uphill”
- Na+,K+ pump (keep [Na+] inside low) 
What is secondary active transport?
- One solute is “pumped” uphill while one solute diffuses downhill
- Cotransport —> both move in same direction
- Na+ flows down
- glucose pumped uphill 
What are some examples of other enzymes the brush border has for small carbs and dextrins? 
•Sucrase for sucrose (glucose plus fructose)
• lactase for lactose (galactose plus glucose)
• dextrinase for dextrins (small glucose polysaccharides)
* simple sugars like fructose and galactose are absorbed similar to glucose
Brush border enzymes
Enterokinase
Where are zymogens produced? 
Pancreas
3 precursors in the lumen of the small intestine that’s produced pancreas? 
Zymofens: trypsinogen, chymotrysinogen, procarboxypetidase
What does the zymogen trysinogen lead to?
(Enterokinase)—-> Trypsin —> chymotrypsin —-> proteins
(Enterokinase) —-> Trypsin —> carboxypeptidase —>proteins
What does the zymogen chymotrypsinogen lead to?
Chymotrypsin —-> proteins
what does procarboxypeptiase lead to?
Carboxypeptidase —> proteins
What are the cells that line the small intestine?
Enterocytes
This is cuts in the middle of protein (trypsin and chymotrysin)
Endopeptidases
Cuts amino acid of the carboxyl end
Carboxypeptidase
Once proteins are digested to individual amino acids, the amino acids are absorbed into the _____________ by the same mechanism as _________.
Mesenteric capillaries, glucose
- secondary active cotransport of amino acids with Na+ 
What is synthesized by the liver and stored in the gallbladder that plays an important role to emulsify fats (keep in small droplets) which allows lipases that are secreted from exocrine pancreas to work more efficiently
Bile salts
Bike salts are ___________, meaning they are both polar and nonpolar
Amphipathic
By the salts are made up of cholesterol and _________. 
Phospholipids
As gut motility breaks fat globules into smaller droplets, _________ attaches to fat droplets and allow them to stay small
Bile salts
What is it called when fat globules are broken down into smaller amphipathic droplets?
Emulsification
This produces somthing like miclles
What is enterhepatic circulation of bile salts?
After the fat are digested and absorbed, biosalts are reabsorbed (by capillaries) into the ileum and returned to the liver (via portal vein) for reprocessing and storage in the gallbladder.
Digestion and absorption of triglycerides is _____-stage 
Multistaged
What are the 6 steps of digestion and absorption of triglycerides?
- Pancreatic lipase digest triglycerides into monoglyceride and fatty acids (FA)
- Micelles foreign in the gu lumen
- Monoglycerides and fatty acids absorbed from micelle by simple diffusion across apical membrane of enterocyte because plasma membranes are fat soluble
- Once inside interocyte, monoglyceride and FAs reform into triglyceride and added to a larger molecule called a chylomicron.
- Chylomicron moved across basolateral membrane by exocytosis
- Diffuses into lacteal (lymph vessel of villus)  and eventually returns to venous circulation
______________ is a triglyceride, apolipoprotein, cholesterol (similar to a low density lipoprotein or what we call “bad” cholesterol
Chylomicron
Monoglycerides and fatty acids are absorbed from micelles by _________ diffusion
Simple
Because plasma membranes are fat soluble
How are chylomicrons moved across basolateral membranes? 
By exocytosis
Stimulates gastric secretion and motility; stimulates ileal motility and relaxes ileocecal sphincter; stimulates mass movement of the colon
Gastrin
What is the site of secretion for gastrin? 
Stomach (G cells) 
What is the stimulus for gastrin?
Proteins and protein digestion products in stomach; distention of stomach; parasympathetic input to stomach
Inhibits gastric secretion and motility, potentates actions of secretion on pancreatic bicarbonate secretion; stimulates pancreatic enzyme secretion; stimulates bile secretion by liver; stimulates gallbladder contraction and relaxation of the sphincter of Oddi
Cholecystokinin (CCK) 
What is the site of secretion for cholecystokinin (CCK)? 
Endocrine cells of the small intestine
What is the stimuli for secretion of cholecystokinin (CCK)? 
Fat or protein digestion products in the duodenum
Inhibits gastric secretion and motility, stimulates pancreatic bicarbonate secretion, potentates actions of CCK on pancreatic enzyme secretion, stimulate bile secretion by liver 
Secretin
What is the site of secretion for secretin?
Endocrine cells of small intestine
What is the stimuli for secretion of secretin?
Acid in the duodenum
Inhibits gastric secretion in motility, stimulates insulin secretion by endocrine pancreas
Glucose dependent insulinotropic peptide (GIP)
- feedforward mechanism
 what is the site of secretion for GIP?
Endocrine cells of small intestine
What is the stimuli for secretion of GIP?
Glucose, fats, or acid in duodenum and stretch of duodenum
 large intestine mainly for last absorption of _________
Water
Intestine is NOT an __________ organ. Feces is simply the part of food that is undigestible 
Excretory 
 metabolism, or synthesis of ATP as needed, is a rather _________ process
Constant
Whereas eating is episodic
What are the two states of metabolism?
-  absorptive state-  The time after meal when digestion and absorption is occurring, 3 to 4 hours
- Postabsorptive state- The time after absorption before the next meal
Hormonal regulation of absorptive state and post absorptive state heavily centers on the regulation of _________. Why?
Plasma glucose
The brain can only use glucose as an energy source 
Everything must be orchestrated to keep plasma __________ add a reasonly constant level for neurons. 
Glucose
(this is not completely true, but it is generally true, and it makes the pattern of response make sense) 
Assuming a mixed diet of carbs, proteins, and fats….
________ is the primary hormone of the absorptive state
Insulin
Assuming a mixed diet of carbs, proteins, and fats….
________, __________, and _________ are the main hormones involved in the post absorb of state
Glucagon, growth hormone, and cortisol
After a meal, plasma glucose increases above _____ mg/dl.
90
Insulin is secreted from _________ cells of endocrine pancreas
Pancreatic Beta 
Insulin works on ______ cells in the body
Most
What does insulin do? 
Shifts towards glucose utilization and storage of extra
_______ stimulates only GIP
Sugar
Making glucose from non-glucose sources
Gluconeogoenisis
This opposes protein breakdown and acts to spare proteins
Growth hormone 
Metabolically, _________ allows full use of proteins as an energy source
Cortisol 
If no food continues, about eight hours post absorptive and beyond, Mika Jen stars become to pleated imagining plasma glucose becomes more critical. It becomes a physiological stress – starvation. Cortisol often called stress hormone is secreted from the adrenal cortex
Postabsortive #2
When plasma glucose dips below setpoint of 90 mg/dl, insulin secretion essentially stops and glucagon secretion (endocrine alpha pancreas cells) begins to rise
Postabsorptive #1
When glucose is stored in liver and muscle
Glycogenesis
When glucose or fatty acids are stored in the liver and or adipose tissue
 lipogenesis 
What are the short term regulators of food intake and Energy balance?
- CCK
- ghrelin 
- insulin
What is the long-term regulator of food intake and energy balance?
Leptin- stimulates sympathetic nervous system
What hormone increases appetite and which one decreases appetite? 
NPY
AgRP
