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Physiology > Unit 5 - Digestion > Flashcards

Unit 5 - Digestion Flashcards

1
Q

How does HCl aid digestion?

A
  1. activates pepsinogen to pepsin (in stomach)
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2
Q

Production of HCl by parietal cells:

A
  1. CO2 diffuses into cells from blood
  2. Carbonic anhydrase catalyzes a reaction between CO2 & H2O to form carbonic acid (H2CO3)
  3. Carbonic acid dissociates into H+ and HCO3- (bicarbonate)
  4. Bicarbonate is transported back into blood stream & Cl- is brought into cell through the Cl-/HCO3- antiporter (secondary active transport)
  5. Cl- diffuse into stomach (down its concentration gradient)
  6. H+ is sent to stomach in exchange for a K+ ion through the H=-K+ ATPase pump (active transport - requires ATP)
  7. H+ and Cl- combine in stomach to form HCl
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3
Q

3 phases for regulation of gastric secretion in stomach

A
  1. cephalic (reflex) phase - prior to food entry
  2. gastric phase - once food enters the stomach
  3. intestinal phase - as partially digested food enters duodenum
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4
Q

disaccharides

A

“two sugar” molecule
sucrose
lactose

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5
Q

monosaccharides

A

glucose
fructose
galactose

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6
Q

polysaccharide

A

starch
amylose - unbranched chain of glucose
amylopectin - branched chain of glucose
cellulose - cannot be digested; indigestible fiber
glycogen - highly branched form of glucose storage in muscle

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7
Q

absorbable units of protein

A

amino acids

small polypeptides

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8
Q

dietary proteins

A

combinations of amino acids held together by peptide bonds

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9
Q

triglyceride

A
  • glycerol with 3 fatty acid molecules
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10
Q

absorbable units of fat

A

monoglycerides (glycerol w/one fatty acid)

free fatty acids (that have been freed from triglyceride)

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11
Q

hydrolysis

A
  • breakdown of dietary foodstuffs

- by adding H2O at bond site, enzymes in digestive secretions break them down to absorbable units

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12
Q

4 factors in regulating digestive system function?

A
  1. autonomous smooth muscle function
  2. intrinsic nerve plexuses
  3. extrinsic nerves
  4. GI hormones
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13
Q

What are the intrinsic nerve plexuses?

A

Together called: enteric nervous system - within the system itself

  1. submucosal plexus
  2. myenteric plexus
    - have motor, excitatory, inhibitory and inter-neurons
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14
Q

autonomous smooth muscle function

A
  • Have pacemaker cells that display slow wave potentials

- Are transmitted via gap junctions

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15
Q

extrinsic neural control

A
  • sympathetic nervous system: inhibits digestion

- parasympathetic: increases smooth muscle motility, promote secretion of digestive enzymes

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16
Q

GI hormones

A

excitatory or inhibitory effect on smooth muscle & exocrine glands cells

17
Q

chief cells

A

in stomach

release pepsinogen

18
Q

parietal cells

A

in stomach

secrete HCl- & intrinsic factor

19
Q

chylomicrons

A

after the micelles have been absorbed into the cell, the monoglycerides and free fatty acids form triglycerides. They gather into droplets & are coated with a layer of lipoprotein which makes them water soluble (called = chylomicrons).

20
Q

gastrin (hormone)

A
  • released in stomach

- stimulates pepsinogen production

21
Q

secretin (hormone)

A
  • released in duodenum
  • hormone
  • stimulated by ACID
  • stimulates pancreatic duct cells to produce NaHCO3 (sodium bicarbonate)
  • stimulates liver to secrete bile
22
Q

cholecystokinin (hormone)

A
  • produced in duodenum
  • stimulated by FATS or PROTEINS in duodenum
  • stimulates pancreas acini – pancreatic enzymes
  • stimulates contraction of gallbladder & relaxation of hepatopancreatic ampulla (sphincter of oddi)
23
Q

somatostatin

A

Produced by:

  • pancreatic D cells - inhibits digestion of nutrients & absorption
  • small intestine epithelial cells - inhibits most digestive processes
  • hypothalamus (aka GHIH) - inhibits secretion of GH & TSH
24
Q

insulin (hormone)

A
  1. facilitates glucose transport into most cells
  2. stimulates GLYCOGENESIS, production of glycogen from glucose (in both skeletal muscle & liver)
  3. inhibits GLYCOGENOLYSIS, breakdown of glycogen into glucose
  4. inhibits GLUCONEOGENSIS, conversion of amino acids into glucose in the liver
25
Q

glucose-dependent insulinotrophic peptide (GIP) (hormone)

A
  • produced in duodenum
  • stimulates pancreas to secrete insulin
  • feed-forward mechanism (vs. feedback)
  • released when food present, especially glucose in digestive tract
26
Q

glucagon (hormone)

A
  • secreted by Alpha cells of islets of Langerhans
  • raise blood glucose by increasing:
    1. rates of glycogen breakdown
    2. glucose manufacture by liver
27
Q

GLUT

A
  • glucose transporters
  • 14 varieties
  • GLUT 1 & 3 – brain
  • GLUT 2 - transfers glucose to blood from kidney & intestinal cells by SGLT
  • GLUT 4 - only one to respond to insulin
28
Q

Which tissues are not dependent on insulin for glucose uptake?

A

brain
liver
working muscles (are dependent at rest)

29
Q

How is insulin secreted?

A

Through EXCITATION-SECRETION COUPLING - change in membrane potential causes insulin secretion

  1. Glucose enters beta cell through GLUT-2
  2. glucose is immediately phosphorylated to GLUCOSE-6-PHOSPHATE
  3. it’s oxidized by beta cell to get ATP
  4. ATP binds to the open K+ channels, which CLOSES it
  5. K+ can’t leave so membrane depolarizes
  6. depolarization causes the VG-Ca2+ channel to OPEN
  7. Ca2+ comes in & tigers exocytosis of secretory vesicles containing insulin
30
Q

Diabetes mellitus

A

reduced levels of insulin
“sweet”
Type 1
Type 2

31
Q

Diabetes insipidus

A

reduced levels of vasopressin - so kidneys cannot conserve H2O
“tasteless”

32
Q

Type 1 diabetes

A

diabetes mellitus
insulin-dependent or juvenile-onset
lack of insulin secretion

33
Q

Type 2 diabetes

A

diabetes mellitus
non-insuline dependent or maturity-onset
normal or increased insulin, but reduced sensitivity of target cells
symptoms - sugar in urine, frequent urination, excessive thirst

34
Q

glucosuria

A

glucose in urine

35
Q

polyuria

A

frequent urination

36
Q

polydipsia

A

excessive thirst

37
Q

polyphagia

A

excessive food intake

38
Q

hyperglycemia

A

high blood sugar

Physiology (15 decks)

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