Lecture 22 Flashcards Preview

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Flashcards in Lecture 22 Deck (56):
1

Large intestine: Smooth muscle =

mechanical digestion

2

Mechanical: Peristaltic waves:

haustral churning
gastroilial reflex
gastrocolic reflex

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haustral churning-

relaxed pouches are filled from below by muscular contractions

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gastroilial reflex =

when stomach is full, gastrin hormone relaxes ileocecal sphincter so small intestine will empty and make room

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gastrocolic reflex =

when stomach fills, a strong peristaltic wave moves contents of transverse colon into rectum

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Chemical Digestion in Large Intestine:

1.No enzymes are secreted only mucous
2.Bacteria ferment
3.Bacteria produce vitamin K and B in colon

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Bacteria ferment: 1st step

1. undigested carbohydrates into carbon dioxide & methane gas

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Bacteria ferment: 2nd step

2. undigested proteins into simpler substances (indoles)----odor

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Bacteria ferment: 3rd step

3. turn bilirubin into simpler substances that produce color

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Absorption in the Large Intestine:

1. Some electrolytes---Na+ and Cl-
2. After 3 to 10 hours, 90% of H2O has been removed from chyme

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Feces are

semisolid by time reaches transverse colon

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Feces =

dead epithelial cells, undigested food such as cellulose, bacteria

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Defecation: What moves feces into the rectum?

Gastrocolic reflex

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Defecation: What signals the sacral spinal cord?

stretch receptors

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Defecation: What contracts muscles of the rectum and relax the internal anal sphincter?

parasympathetic nerves

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Defecation: What is voluntarily controlled?

external sphincter

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Diarrhea =

chyme passes too quickly through intestine
H2O not absorbed

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Constipation--

decreased intestinal motility
too much water reabsorbed

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Dietary fiber- Insoluble fiber:

-woody parts of plants
-speeds up transit time & reduces colon cancer

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Dietary fiber- Soluble fiber:

-gel-like consistency = beans, oats, citrus white parts, apples
-lowers blood cholesterol

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How does soluble fiber lower blood cholesterol?

by preventing reabsorption of bile salts so liver has to use cholesterol to make more

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Functions of food:

source of energy
essential nutrients
stored for future use

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Metabolism is

all the chemical reactions of the body

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Absorptive state:

1. nutrients entering the bloodstream
2. glucose readily available for ATP production
3. 4 hours for absorption of each meal

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Postabsorptive state:

1. absorption of nutrients from GI tract is complete
2. body must meet its needs without outside nutrients
3. maintaining a steady blood glucose level is critical

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Body cells use glucose for

ATP production

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Storage of excess fuels occur in

hepatocytes, adipocytes & skeletal muscle

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most glucose entering liver cells is converted to

glycogen (10%) or triglycerides (40%)

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dietary lipids are stored in

adipose tissue

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amino acids are

deaminated to enter Krebs cycle or are converted to glucose or fatty acids

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amino acids not taken up by

hepatocytes used by other cells for synthesis of proteins

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Beta cells of pancreas release

insulin

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Insulin’s functions:

1. increases anabolism & synthesis of storage molecules
2. decreases catabolic
3. promotes entry of glucose & amino acids into cells
4. stimulates phosphorylation of glucose
5. enhances synthesis of triglycerides
6. stimulates protein synthesis along with thyroid & growth hormone

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Maintaining normal blood glucose level

(70 to 110 mg/100 ml of blood) is major challenge

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glucose enters blood from 3 major sources:

1. glycogen breakdown in liver produces glucose
2. glycerol from adipose converted by liver into glucose
3. gluconeogenesis using amino acids produces glucose

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alternative fuel sources are

1. fatty acids
2. lactic acid
3. oxidation of ketone bodies by heart & kidney

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Most body tissue switch to

utilizing fatty acids, except brain still need glucose

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As blood glucose level declines

pancreatic alpha cells release glucagon

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glucagon stimulates

gluconeogenesis & glycogenolysis within the liver

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Hypothalamus detects

low blood sugar

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sympathetic neurons release

norepinephrine

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adrenal medulla releases

norepinephrine & epinephrine

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determining factor of starvation;

amount of adipose tissue

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Nutritional needs:

1.nervous tissue & RBC need glucose
2. increase in formation of ketone bodies by liver cells

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Catabolic reactions breakdown

complex organic compounds
-providing energy

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Anabolic reactions synthesize

complex molecules from small molecules
-requiring energy

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Each cell has about 1 billion ATP molecules that last for

less than one minute

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Over half of the energy released from ATP is converted to

heat

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Energy is found in the

bonds between atoms

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Oxidation is a

decrease in the energy content

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Reduction is the

increase in the energy content

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Oxidation-reduction reactions are always coupled within

the body

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Phosphorylation is

ADP + P = ATP
3rd phosphate group

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Mechanisms of phosphorylation:

within animals

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Gluconeogenesis:

Liver glycogen runs low if fasting, starving forcing formation from other substances

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Gluconeogenesis stimulated by

cortisol (adrenal) & glucagon (pancreas)