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Animal Physiology > Digestion > Flashcards

Digestion Flashcards

1
Q

What are the 7 classes of nutrients required by the animal body?

A

carbohydrates
lipids
proteins
vitamins
minerals
ions
water

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2
Q

What is required for animals to use these nutrients?

A

digestion - both mechanical and chemical

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3
Q

How does food provide sustenance for life?

A

food provides the structural and functional building blocks for materials, energy and heat

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4
Q

What are the 2 processes involved in digestion?

A

assimilation
egestion

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5
Q

What is assimilation?

A

processes involved in nutrient acquisition, digestion, and absorption

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6
Q

What is egestion?

A

the excretion of undigested food

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7
Q

Where does assimilation occur?

A

in the GI tract

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8
Q

What 4 types of cells are in the GI tract?

A

secretory cells
absorptive cells
muscle cells
neurons

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9
Q

Are nutrients reduced or oxidized from food to generate energy?

A

oxidized

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10
Q

What determines the amount of energy needed from food for an animal?

A

the metabolic requirements of the animal

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11
Q

What affects metabolic rates?

A

body size
activity
growth rate
reproductive state
environmental stress

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12
Q

What is the caloric equivalent?

A

the energy content per gram of a specific macromolecule

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13
Q

What is the caloric equivalent of proteins and carbs?

A

4 kcal/g

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14
Q

What is the caloric equivalent of fats?

A

9 kcal/g

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15
Q

What are vitamins?

A

a class of nutrients composed of unrelated molecules with diverse functions

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16
Q

What do most vitamins function in?

A

catalysis as cofactors for enzymes
some are antioxidants

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17
Q

How are most vitamins categorized?

A

solubility - in water or fat

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18
Q

Which vitamins are fat-soluble?

A

A
D
E
K

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19
Q

Which vitamins are water-soluble?

A

B
C

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20
Q

How are vitamins acquired in the body?

A

in diet or bacteria in the GI tract

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21
Q

What are minerals?

A

a class of nutrients composed of metallic elements involved in physiology and structure

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22
Q

What are 5 minerals involved in physiology?

A

calcium
phosphorous
iron
copper
zinc

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23
Q

Why is calcium important in animal bodies?

A

involved in intracellular cell signalling

bone structure

muscle contraction

neurotransmission

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24
Q

What is phosphorous important for in animal bodies?

A

bone structure
ATP
phospholipids

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25
Q

How is iron involved in animal physiology?

A

it is the metal ion contained in hemoglobin (respiratory pigments)

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26
Q

How is copper involved in animal physiology?

A

contained in cytochrome c oxidase in oxidative phosphorylation = production of ATP

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27
Q

How is zinc involved in animal physiology?

A

zinc has a functional role in enzymes and transcription factors

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28
Q

Where are most minerals absorbed in the body?

A

along the GI tract by specific transporters

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29
Q

What is the function of digestive enzymes?

A

they convert macromolecules into forms that can be absorbed and processed by the body

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30
Q

What are 4 classes of digestive enzymes?

A

lipases

proteases

amylases

nucleases

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31
Q

what are lipases

A

enzymes that break down (lipids) triglycerides and phospholipids into fatty acids

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32
Q

What are proteases?

A

enzymes that break down proteins into smaller polypeptides

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33
Q

What are 3 types of proteases?

A

trypsin
chymotrypsin
carboxypeptidase

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34
Q

What do peptidases do?

A

enzymes that cleave amino acids in succession

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35
Q

What do amylases do?

A

enzymes that break down (carbohydrates) polysaccharides into oligosaccharides

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36
Q

what are 3 types of disaccharidases?

A

maltase
sucrase
lactase

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37
Q

What are nucleases?

A

enzymes that break down DNA into nucleotides

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38
Q

Where does most enzymatic digestion occur?

A

extracellularly in the lumen of the GI tract

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39
Q

What usually aids animal digestion?

A

symbiotic organisms (ex. bacteria, fungi, photosynthetic organisms)

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40
Q

What are the 3 types of symbionts in digestion?

A

enterosymbionts
exosymbionts
endosymbionts

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41
Q

What are enterosymbionts?

A

symbionts that live in the lumen of GI tract - usually in the cecum

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42
Q

Where are enterosymbionts usually located?

A

within the lumen of the cecum of the GI tract

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43
Q

What are exosymbionts? what’s an example?

A

symbionts that are outside the body

ex. leaf cutter ants that cut down leaves from trees for fungi to digest the leaves so that nutrients are available to the ants

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44
Q

What are endosymbionts?

A

symbionts that live in the interstitial spaces or within host cells

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45
Q

What are examples of endosymbionts?

A

zoochlorellae (green algae) in sponges, cnidarians, and molluscs that produce the carbon skeleton, glucose, and maltose

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46
Q

What are the main types of carbohydrates consumed by animals?

A

polysaccharides (ex. glycogen, starch, cellulose, chitin) and disaccharides (ex. sucrose, lactose, maltose)

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47
Q

What are the 4 polysaccharides?

A

glycogen
starch
cellulose
chitin

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48
Q

What are the 3 types of disaccharides?

A

sucrose
lactose
maltose

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49
Q

What are 3 types of monosaccharides?

A

glucose
fructose
galactose

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49
Q

What are the main types of carbohydrates that can be absorbed by animals?

A

monosaccharides (ex. glucose, fructose, galactose)

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50
Q

How are monosaccharides absorbed by animals?

A

absorbed by the epithelial cells in the intestine (enterocytes) via secondary active transport and facilitated diffusion

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51
Q

What are enterocytes?

A

epithelial cells in the intestine

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52
Q

What transportation is involved in absorption of monosaccharides?

A

secondary active transport

facilitated diffusion

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53
Q

What is glycogen?

A

the storage form of carbohydrates in mammalian muscle and liver cells

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54
Q

What is starch?

A

the storage form of carbohydrates in plants

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55
Q

What is cellulose?

A

a form of carbohydrate found in plant cell walls that cannot be digested by human enzymes

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56
Q

How do herbivores digest cellulose?

A

the enterosymbionts in their guts

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57
Q

what is chitin?

A

the carbohydrate form that exists in exoskeletons of arthropods and in plankton

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58
Q

What is maltose?

A

a disaccharide of 2x glucose monomers

found in malt in beer

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59
Q

What is lactose?

A

a disaccharide of glucose and galactose monomers

carbs found in milk

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60
Q

What is sucrose?

A

a disaccharide of glucose and fructose monomers

found in sweeteners

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61
Q

What are the two types of starch?

A

amylose and amylopectin

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62
Q

describe the structure of starch vs glycogen

A

starches are less branched than glycogen

all composed of glucose polymers

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63
Q

Describe the steps of carbohydrate digestion

A

polysaccharides (glycogen and starch) are broken down by salivary amylase in the mouth into glycogen, oligosaccharides

pancreatic amylases digest glycogen, oligosaccharides and starch in the small intestine into disaccharides

disaccharidases breakdown disaccharides into monosaccharides in the small intestine

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64
Q

Where does most of carbohydrate digestion occur?

A

in the small intestineW

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65
Q

What enzymes are involved carbohydrate breakdown? where?

A

salivary amylases in the mouth

pancreatic amylases in the small intestine break down polysaccharides into disaccharides

disaccharidases in the small intestine break down disaccharides into monosaccharides

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66
Q

T or F: glucose and amino acids can diffuse across plasma membranes

A

false

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67
Q

what are the specific protein transporters involved in transporting carbohydrate monomers across membranes?

A

GLUT-2 and GLUT-5

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68
Q

What absorbs monosaccharides?

A

enterocytes of the small intestine

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69
Q

What does GLUT-5 do?

A

imports fructose into cells

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70
Q

What is SGLT-1? what does it do?

A

Na+ glucose cotransporter 1

transports glucose and galactose into enterocytes

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71
Q

What does GLUT-2 do?

A

when high [glucose], GLUT-2 transports glucose, galactose and fructose

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72
Q

What is the apical membrane?

A

the membrane of an enterocyte that has microvilli and closest to the lumen

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73
Q

What is the basolateral membrane?

A

the membrane of an enterocyte that does not have microvilli and is closest to the interstitial fluid

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74
Q

Which membrane(s) of an enterocyte have microvilli?

A

only the apical membrane

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75
Q

Which enterocyte membrane interacts with the lumen of the small intestine?

A

apical

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76
Q

Which enterocyte membrane interacts with the interstitial fluid?

A

basolateral

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77
Q

How many amino acids are there?

A

20

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78
Q

What are amino acids used for?

A

they’re the building blocks of proteins

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79
Q

What is an essential amino acid?

A

the amino acids that cannot be produced by the body and must be obtained through diet

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80
Q

T or F: most amino acids are essential

A

false, only 9/20 are essential and need to be obtained from diet

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81
Q

What happens to an animal if essential amino acids are not acquired in amounts needed?

A

developmental defects and reduced growth

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82
Q

What is protein quality?

A

the amino acid profile of proteins obtained from the diet

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83
Q

Does animal or plant tissue provide higher protein quality?

A

animal tissue

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84
Q

Why are plant and animal based diets good?

A

animal tissues supply the AA requirements and when combined with plants, all AA requirements can be fulfilled

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85
Q

What breaks down proteins into large polypeptides?

A

gastric pepsin

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86
Q

Where does protein digestion begin?

A

aside from the mechanical and salivary break down in the mouth to move food down esophagus

in the stomach

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87
Q

Where is gastric pepsin?

A

in the stomach

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88
Q

What happens after proteins are digested into large polypeptides?

A

polypeptides move to the small intestine where they are broken down into dipeptides and further into AAs

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89
Q

What breaks down polypeptides in the small intestine? What does it break down into?

A

trypsin
chymotrypsin
carboxypeptidase

break down polypeptides into dipeptides

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90
Q

What breaks down dipeptides in the small intestine? into what?

A

dipeptidases break down dipeptides into amino acids in the small intestine

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91
Q

In what form(s) can proteins be absorbed in?

A

dipeptides, tripeptides, and AAs

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92
Q

What organ releases the 3 proteases that break down polypeptides in the small intestine?

A

the pancreas

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93
Q

What enzymes liberate free AAs, dipeptides, and tripeptides?

A

peptidases: aminopeptidase, dipeptidylaminopeptidase, tripeptidase

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94
Q

In the pancreatic duct, what form do the pancreatic proteases take when not digesting?

A

inactive

procarboxypeptidase
chymotrypsinogen
trypsinogen

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95
Q

Why are the pancreatic proteases inactive in the pancreatic duct?

A

to prevent digesting the pancreas

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96
Q

What happens when the inactive proteases are released by the pancreas?

A
  1. the pancreas secretes inactive trypsinogen into the small intestine and binds to membrane-bound enterokinase which cleaves trypsinogen into active trypsin
  2. active trypsin cleaves inactive chymotrypsinogen released by pancreas into active chymotrypsin
  3. chymotrypsin cleaves inactive procarboxypeptidase into active carboxypeptidase
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97
Q

Where are the pancreatic proteases activated?

A

in the duodenum of the small intestine

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98
Q

What activates trypsonigen?

A

it binds to membrane-bound enterokinase on the small intestine membrane which cleaves trypsonigen into active trypsin

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99
Q

What activates chymotrypsinogen?

A

trypsin cleaving it into chymotrypsin in the small intestine

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100
Q

What activates procarboxypeptidase?

A

chymotrypsin cleaves it into carboxypeptidase in the small intestine

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100
Q

What are the products of protein digestion?

A

peptides (di and tri) and amino acids

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101
Q

Where are peptides and amino acids absorbed?

A

the enterocytes of the small intestine

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102
Q

How are peptides and AAs absorbed into enterocytes? is it the same system for both?

A

both are transported across the apical membrane but the transport systems are different

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103
Q

What transporters move peptides across the apical membrane of enterocytes?

A

PEPT1 transport di and tripeptides with the support of a proton transporter

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104
Q

How are most amino acids transported across the apical membrane of enterocytes?

A

amino acid-Na+ cotransporters

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105
Q

What process can directly digest proteins without digestion into peptides and AAs?

A

some proteins can be absorbed by endocytosis (ex. antibodies)

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106
Q

What are simple lipids?

A

fatty acids
triacylglycerol
sterols (cholesterol)

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107
Q

What are compound lipids?

A

phospholipids
lipoproteins

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108
Q

What are saturated fatty acids?

A

fatty acids without C=C

the fatty acid is saturated with H+

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109
Q

What are unsaturated fatty acids?

A

fatty acids with C=C

can be mono or poly

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110
Q

Describe the trans configuration of an unsaturated fatty acid

A

the fatty acid will remain linear

the Cs in the double bond are on opposite sides

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111
Q

Describe the cis configuration of an unsaturated fatty acid

A

the Cs of the double bond are on the same side

this introduces a kink in the chain

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112
Q

What is the hydrophobic component of a fatty acid?

A

the hydrocarbon chain

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113
Q

What is the hydrophilic component of a fatty acid?

A

the carboxylic end

HO-C=O

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114
Q

T or F: animals can make almost all fatty acids from acetyl CoA

A

true

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115
Q

What material can animals make most fatty acids from?

A

acetyl CoA

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116
Q

Which fatty acids can animals not produce from acetyl CoA?

A

omega-3
omega-6

both are unsaturated fatty acids

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117
Q

How is omega 6 ingested?

A

as gamma-linoleic acid

118
Q

What food stuff contains omega 6 FA?

A

plant seeds
poultry
eggs
nuts

119
Q

What type of fatty acid is omega 6? omega 3?

A

they’re both unsaturated

120
Q

How is omega-3 ingested?

A

as alpha-linolenic acid

121
Q

What foodstuff is omega-3 FA found in?

A

cold water fish

122
Q

Why is it called omega 3? or omega 6?

A

the number refers to the C number where the first double bond is from the omega start (opposite end to the carboxylic acid)

omega 6 - first double bond is located at C6

omega 3 - first double bond is at C3

123
Q

How many carbons are in omega-6? how many double bonds?

A

18:2

124
Q

How many carbons are in omega-3? how many double bonds?

A

18:3

125
Q

What is the omega?

A

C1 when starting counting from the methyl end of the carbon chain/opposite of the carboxylic end

126
Q

How is most body fat stored?

A

in the form of triacylglycerols (TAGs)

127
Q

What breaks down FAs?

A

lipases

128
Q

Describe the structure of a triacylglycerol

A

a glycerol backbone (3Cs) attached to 3 FA chains via an ester bond (-O-CO-FA)

129
Q

How are triacylglycerols broken down?

A

from glycerol by lipases

130
Q

Describe glycerol

A

H
|
H-C-OH
|
H-C-OH
|
H-C-OH
|
H

131
Q

What binds glycerol with fatty acids to make TAGs?

A

ester bonds

132
Q

What is an ester bond?

A

O
||
glycerol-O-C-FA

133
Q

What type of lipid dominates biological membranes?

A

phospholipids

134
Q

What are the 2 classes of phospholipids in animal cells?

A

phosphoglycerides
sphingolipids

135
Q

Describe phosphoglyceride

A

a class of phospholipid in animal cell membranes made from diacylglycerol (glycerol + 2 FAs)and has a polar group on the third glycerol carbon (usually phosphate + choline)

136
Q

Describe sphingolipids

A

a class of phospholipids in animal cell membranes containing a sphingosine backbone + 1 FA chain

usually has a polar group (phosphate + choline)

137
Q

What breaks down phospholipids?

A

phospholipases

138
Q

Are saturated fats more common in solid animal fats or liquid fats?

A

solid animal fats

139
Q

Are unsaturated fats more common in solid animal fats or liquid fats?

A

liquid fats

the kinks make it harder to solidify

140
Q

What breaks down sphingolipids?

A

sphingolipases

141
Q

Is cholesterol hydrophobic or philic?

A

phobic

142
Q

What is cholesterol a precursor to?

A

steroid hormones like glucacorticoids, mineralocorticoids and sex hormones

143
Q

What makes digestion and absorption of lipids challenging?

A

lipids are hydrophobic

144
Q

Where does digestion of lipids occur?

A

in the duodenum of the small intestine

145
Q

Describe the steps of lipid digestion

A

in the lumen of the duodenum:

1.a lipase breaks down a fat globule into monoacylglycerides and FAs

  1. FAs, mono and glycerol are broken down by the bile secreted by the gall bladder into fat droplets (micelles)
  2. micelles of FAs, glycerol, and tri, mono, and cholesterol diffuse across cell membrane into an enterocyte
  3. FA + glycerol diffuse directly into the bloodstream
  4. tri, mono, and cholesterol are packaged into the smooth ER and Golgi and are then released into the lymphatic system and then into the circulatory system
146
Q

What are micelles?

A

small droplets of fat produced when bile from the gall bladder breaks down lipids

147
Q

What breaks down dietary fats? What do they break down into?

A

lipases break down dietary fats into fatty acids, glycerol and monoglycerides

148
Q

What secretes lipases?

A

the pancreas

149
Q

What type of cell do lipids diffuse into?

A

enterocytes of the small intestine

150
Q

Once in the enterocyte, what happens to fatty acids and glycerol? why?

A

they diffuse directly into the blood vessels

they are short and medium chain lengths - easy to diffuse

151
Q

Once in the enterocyte, what happens to longer chained fatty acids, monoglycerides, triglycerides and cholesterol?

A

they are packaged in protein coats (lipoproteins) in the smooth ER and Golgi and are then transported into the

lymphatic system and then into the circulatory system

lipoprotein lipase breaks down triglycerides to be used by tissues

152
Q

What are chylomicrons?

A

the type of lipoprotein that forms the protein coat on the longer chain FAs, monoacylglycerides, triglycerides and cholesterol that enter the enterocyte

this occurs in the smooth ER and the Golgi

153
Q

What happens to chylomicrons?

A

they are transported into the lymphatic system and then the circulatory system

154
Q

What breaks down triglycerides once in the circulatory system?

A

lipoprotein lipases

155
Q

Which lipids do not directly enter the circulatory system from the enterocyte?

A

longer chain fatty acids
monoacylglycerides
triglycerides
cholesterol

156
Q

What direction does food flow through the GI tract of mammals (unidirectional, bidirectional)?

A

one way

157
Q

Where does mechanical digestion occur in the GI tract of mammals?

A

mouth
pharynx
esophagus

158
Q

What is the acidic compartment of the GI tract of mammals?

A

the stomach

159
Q

Where does the major digestion and absorption of nutrients and water occur in the GI tract of mammals?

A

upper or small intestines

160
Q

What occurs in the large intestines of mammals?

A

water absorption

161
Q

Where is waste released from the mammalian digestive tract?

A

through the anus

162
Q

Describe the regions of the GI tract of mammals from mouth onwards

A

mouth
esophagus
stomach
small intestine (duodenum, jejunum, ileum)
large intestine (cecum, colon, rectum)
anus

163
Q

What are the regions of the small intestine?

A

duodenum
jejunum
ileum

164
Q

What are the regions of the large intestine?

A

cecum
colon
rectum

165
Q

What feature ensures unidirectional flow of food?

A

sphincters

166
Q

What is the gut derived from?

A

the endoderm

167
Q

What are the 3 major regions of the gut?

A

foregut
midgut
hindgut

168
Q

What is included in the foregut?

A

esophagus
stomach
anterior part of duodenum

169
Q

What organs form from the foregut during development?

A

the pancreas and liver

170
Q

What is included in the midgut?

A

posterior end of the duodenum
jejunum
ileum
cecum
2/3 of the colon

171
Q

What is included in the hindgut?

A

the last 1/3 of the colon
rectum

172
Q

How do the liver, gall bladder, and pancreas interact with the small intestine?

A

the liver produces bile and secretes it into the gall bladder for storage

the gall bladder releases bile through the bile duct into the duodenum

the pancreas releases digestive enzymes through the pancreatic duct into the duodenum

173
Q

How do the liver, gall bladder, and pancreas aid in digestion?

A

the liver produces and sends bile to the gall bladder

the gall bladder releases bile into the duodenum of the small intestine

the pancreas releases digestive enzymes into the duodenum of the small intestine

174
Q

What major anatomical feature is involved in mammalian mechanical digestion?

A

teeth

175
Q

What are the 4 types of teeth?

A

incisors
canines
premolars
molars

176
Q

How can teeth be used to infer diet?

A

shape

incisors and canines are sharp and pointed for tearing and piercing flesh

premolars and molars are short and flat for grinding and chewing

177
Q

What are the 3 layers of teeth?

A

enamel (outer)
dentin (mid)
pulp (blood vessels and nerves)

178
Q

What aids teeth in the breakdown of food in the mouth to prepare for swallowing?

A

salivary glands

179
Q

What are the 4 salivary glands in mammals?

A

orbital
sublingual
mandibular
parotid

180
Q

What are salivary glands?

A

multicellular exocrine glands with ducts that open into the mouth to secrete saliva

181
Q

What is saliva? what is its purpose?

A

produced by the exocrine salivary glands and released into the mouth to

lubricate and dissolve food
clean mouth - antimicrobial
contains enzymes = initiates digestion

182
Q

What initiates digestion?

A

saliva

183
Q

What controls saliva production?

A

nerve signals of the

PNS = stimulates
SNS = inhibits

184
Q

How does saliva protect the GI tract?

A

it is antimicrobial = cleans the mouth

185
Q

Where are most nutrients chemically broken down in mammals?

A

in the lumen of the GI tract

186
Q

What absorbs nutrients in the GI tract?

A

enterocytes lining the small intestine

187
Q

How is nutrient uptake improved?

A

by increasing surface area:

increased gut length
increased surface undulations (circular folds, villi, microvilli)

188
Q

What are the 2 ways surface area of the GI tract can be increased?

A

increased gut length
increased surface undulations

189
Q

What are 3 ways the surface undulations of the GI tract is increased?

A

circular folds in the lining
villi on the folds
microvilli on the enterocytes

190
Q

How have ruminant mammals (ex. ungulates) evolved to digest complex plant materials like cellulose?

A

with the specialized compartments in their stomach

rumen
reticulum
omasum
abomasum

191
Q

Where does the breakdown of cellulose occur in ruminants?

A

in the rumen compartment of their stomach

192
Q

T or F; humans can break down cellulose

A

false, we don’t have specialized structures or symbiotic relationships to do that

193
Q

What type of cells line the surface of the stomach?

A

columnar epithelial cells

194
Q

What are the 5 specialized cells in the stomach?

A

tight junctions
mucous neck cells
parietal cells
chief cells
enteroendocrine cells

195
Q

what is the purpose of the tight junctions in the stomach?

A

they prevent acid from leaking across the epithelium

196
Q

what is the purpose of the mucous neck cells in the stomach?

A

they protect the stomach lining from the acidity by secreting mucus and bicarbonate

197
Q

what is the purpose of the parietal cells in the stomach?

A

they create the acidic (low pH) environment of the stomach by secreting hydrochloric acid (HCl)

198
Q

what is the purpose of the chief cells in the stomach?

A

they secrete pepsinogen (inactive) a digestive enzyme that when activated by low pH environment cleaves pepsin

199
Q

what is the purpose of the enteroendocrine cells in the stomach?

A

they secrete hormones into the blood like gastrin

200
Q

What muscle type lines the entire GI tract?

A

smooth muscle

201
Q

What are the 4 main layers of the small intestine?

A

mucosa
submucosa (blood, lymphatic vessels, nerves)
circular smooth muscle
longitudinal smooth muscle

202
Q

what 5 cell types make up the villi of the small intestine?

A

all mucosal cells

enterocytes
goblet cells
enteroendocrine cells
paneth cells
crypt of Lieberkuhn

203
Q

What is the purpose of enterocytes of the villi?

A

they are the cells that absorb nutrients and are coated with microvilli

204
Q

What is the purpose of goblet cells of the villi?

A

they protect food coming from the stomach by secreting mucus

205
Q

What is the purpose of enteroendocrine cellsof the villi?

A

they secrete hormones

206
Q

What is the purpose of paneth cells of the villi?

A

they secrete antimicrobial molecules called lysozyme

207
Q

What is the purpose of the crypt of Lieberkuhn of the villi?

A

it secretes digestive enzymes

sucrase, maltase, lactase, peptidase

208
Q

What exocrine cells of the pancreas secrete enzymes into the intestine?

A

acinar cells

209
Q

What 5 types of enzymes do acinar cells of the pancreas secreted into the intestine?

A

proteases to break down proteins (secreted as proenzymes / inactive)

amylases to break down carbohydrates

lipases to break down fats (TAGs)

nucleases to break down nucleic acids

phospholipases to break down phospholipids

210
Q

What is bile?

A

a solution of digestive chemicals and liver waste products that is produced in the liver and stored in the gall bladder

211
Q

What are the 3 major constituents of bile? what are their functions?

A

phospholipids to help uptake lipids

bile salts to break down fats

cholesterol

212
Q

How does bile enter the small intestine?

A

via a bile duct from the gall bladder into the duodenum

213
Q

How does food move down the GI tract?

A

by smooth muscle contractions

214
Q

What regulates the smooth muscle contractions of the GI tract?

A

nerves and hormones

215
Q

What is the optimal speed of food along the GI tract?

A

a speed that is fast enough to minimize indigestible material but slow enough to allow for digestion and absorpiton

this depends on diet

216
Q

What are the 2 layers of the smooth muscle cells in the gut?

A

longitudinal
circular

217
Q

What do longitudinal smooth muscles cells do in the GI tract?

A

they control peristalsis (the wavelike rhythmic contractions)

218
Q

What do circular smooth muscles cells do in the GI tract?

A

they help with peristalsis and control the diameter and segmentation of the GI tract

219
Q

Is smooth muscle contraction in the GI tract myogenic or neurogenic?

A

both

220
Q

What is the myenteric plexus?

A

the nerve network layer between the circular and longitudinal smooth muscle layers that is innervated by the SNS and PNS

221
Q

Describe the steps involved in the control of gastric secretions when sight/taste/smell are the stimuli

A

stimuli: sight/taste/smell triggers activity of parasympathetic neurons to activate

a) G Cells
b) parietal cells

G cells produce Gastrin
Gastrin targets:
a) ECF cells
b) Chief cells

ECF releases histamine, both histamine

histamine and parasympathetic neurons directly activate parietal cells

parietal cells release acid

Chief cells activate pepsinogen

222
Q

Describe the steps for control of gastric secretions when ingestion is the stimuli

A

chemo and mechanoreceptors sense the stimulus

activate
a) parasympathetic neurons
b) G cells
c) enteric nerves

the parasympathetic neurons and G cells follow the same pathway as described for taste/sight/smell

enteric nerves stimulate G cells which then release gastrin

gastrin targets ECF and Chief cells

ECF cells release histamine to target parietal cells which release acid

chief cells target pepsinogen

223
Q

What neurons receive taste/sight/smell stimuli?

A

parasympathetic neurons

224
Q

What neurons receive ingestion stimuli?

A

chemo and mechanoreceptors

225
Q

What cells do the parasympathetic neurons target when sight/taste/smell stimuli is received or when chemo/mechanoreceptors send signals about ingestion?

A

G cells
Parietal cells

226
Q

What cells do the chemo/mechanoreceptors target when there’s ingestion stimuli (not signals to PNS)?

A

enteric nerves
G cells

227
Q

What do G cells release when stimulated?

A

gastrin

228
Q

What cells do G cells target with gastrin?

A

ECF and chief cells

229
Q

What do ECF cells release when stimulated?

A

histamine

230
Q

What does histamine target?

A

parietal cells

231
Q

What do chief cells target?

A

pepsinogen

232
Q

What do parietal cells secrete?

A

acid

233
Q

What are the 2 products of stimuli for sight/smell/taste and ingestion?

A

either acid or pepsinogen

234
Q

What happens to acid in the control of intestinal secretion?

A

when acid is secreted it targets enteroendocrine cells

enteroendocrine cells release VIP or Secretin

VIP targets the pancreas and causes the release of bicarbonate (HCO3-)

Secretin targets the liver and causes the release of bile

235
Q

When acid is produced, what 2 substances do the enteroendocrine cells produce?

A

VIP
Secretin

236
Q

What organ does VIP target?

A

the pancreas

237
Q

What does VIP stimulating the pancreas cause?

A

the release of bicarbonate in the intestine

238
Q

What organ does secretin target?

A

the liver

239
Q

What does stimulation of the liver by secretin cause?

A

the release of bile in the intestine

240
Q

What are the steps following digestive products in the intestine regarding acidic gastric fluids?

A

enteroendocrine cells are stimulated to release CCK

CCK targets the
a) gall bladder to release bile
b) pancreas to release digestive enzymes (ex. amylase, protease, lipase)

241
Q

What do enteroendocrine cells release in response to digestive products in the intestine?

A

CCK

242
Q

What organs does CCK target?

A

gall bladder and pancreas

243
Q

What does the stimulation of the gall bladder by CCK cause?

A

the secretion of bile into the intestine

244
Q

What does the stimulation of the pancreas by CCK cause?

A

the secretion of digestive enzymes into the intestine

245
Q

What is VIP?

A

Vasoactive Intestinal Peptide

246
Q

What is CCK?

A

Cholecystokinin

247
Q

What is body mass controlled by?

A

energy balance

food intake - food expenditure

248
Q

What controls satiety and hunger?

A

the hypothalamus (CNS)

249
Q

How does the hypothalamus control and regulate hunger, appetite, and satiety?

A

the CNS receives information from adipose tissues (fat) and from the gut on energy reserves

250
Q

What 3 hormones control appetite?

A

leptin
ghrelin
peptide YY
CCK

251
Q

What is leptin?

A

an appetite-suppressing hormone in adipose tissue

252
Q

What is ghrelin?

A

an appetite-stimulating hormone released from gastric cells when the stomach is empty

253
Q

What is peptide YY?

A

an appetite-reducing hormone released from enteroendocrine cells when colon is full

254
Q

What hormones are released between meals (short term regulation of energy stores)?

A

ghrelin
PYY
CCK
vagus nerve is stimulated

255
Q

What hormones are released during long term regulation of body energy stores?

A

leptin

tells the brain you’ve just eaten, you’re satiated, and can survive not eating until breakfast for ex.

256
Q

Describe the set up of the mouse study and obesity, diabetes, body mass

A

mice with mutations for obesity and diabetes had their circulatory systems surgically connected to wild type mice or to another mouse with a condition (parabiosis)

257
Q

What was the mutation that caused mice to be obese? diabetic?

A

the obese and diabetic mice lacked or had damage to the genes that encoded for the production of hormones that tell the hypothalamus they are satiated (ex. leptin)

258
Q

what happened when the obese mouse was connected to the WT mouse? why?

A

the obese mouse lost weight
WT mouse remained same weight

the obese mouse was receiving signals from the circulatory system of the WT mouse for satiation and stopped feeding

259
Q

what happened when the diabetic mouse was connected to the WT mouse? why?

A

the diabetic mouse stayed obese
the WT mouse lost weight

the diabetic mouse did not stop feeding as a result of the hormone production by the WT mouse - the diabetic mouse must have damage or lack the receptors for satiation hormones

the WT mouse overproduced satiation hormones to stop the diabetic mouse from eating but just prevented itself from eating cause diabetic had no receptors

260
Q

what happened when the obese mouse was connected to the diabetic mouse? why?

A

the obese mouse lost weight
the diabetic mouse stayed the same weight

diabetic mouse must be able to produce the satiation hormones and circulate to the obese mouse with intact receptors

but the diabetic mouse must have damage to or lack the receptors for the satiation hormones

261
Q

Which hormone was the obese mouse unable to produce?

A

leptin (satiating hormone)

262
Q

Which receptor did the diabetic mouse lack?

A

leptin receptor

263
Q

Why did the diabetic mouse not lose weight in any of the studies?

A

it was able to produce leptin (satiating) but was not able to receive it so it continued eating

264
Q

Where are the receptors for hormones that control appetite?

A

in the hypothalamus

265
Q

What secretes leptin? when? what is its main function?

A

white adipose tissues when lipid content is high (reached enough energy content)

to suppress appetite

266
Q

What secretes ghrelin? when? what is its main function?

A

the stomach when it is empty

stimulates appetite

267
Q

What secretes PYY? when? what is its main function?

A

the colon when it is full

suppresses appetite

268
Q

What secretes CCK? when? what is its main function?

A

the duodenum when full

suppresses appetite

269
Q

Which of the 4 appetite hormones suppress appetite?

A

leptin (white adipose tissue)
PYY (colon)

270
Q

Which of the 4 appetite hormones stimulate appetite?

A

ghrelin (stomach)
CCK (duodenum)

271
Q

What part of the hypothalamus has the receptors for appetite control hormones?

A

arcurate nucleus

272
Q

What happens when the arcurate nucleus of the hypothalamus receives hormones from the gut or adipose tissues?

A

hypothalamic neurons release neurotransmitters to stimulate or inhibit appetite

273
Q

What hypothalamic neurons stimulate appetite?

A

neuropeptide Y (NPY)

274
Q

What hypothalamic neurons inhibit appetite?

A

pro-opiomelanocrotin (POMC)

275
Q

How is the vagus nerve related to digestion?

A

the vagus nerve innervates the stomach muscles causing them to churn food for digestion and release digestive enzymes and hormones

276
Q

T or F: gut microbiota is related to obesity

A

true, study suggests that there were different microbiota in obese vs. WT mice

277
Q

What is the response to short term starvation (over night, between meals)?

A

in adipose tissues:
- Triglycerides broken down into FAs
- FAs converted into CO2 (used for energy)

FAs from adipose tissues can be transported to the liver or muscles

in the liver:
a) triglycerides are broken down into FAs
or FAs from adipose tissues
both are converted into CO2 (used for energy)

b) glycogen is broken down into glucose which is transported to the brain and byproduct of energy production releases CO2

278
Q

Which organs are involved in the starvation responses?

A

adipose tissues
liver
muscles
brain

279
Q

What stores of energy are used in response to SHORT term starvation?

A

energy stored in triglycerides (lipids) and in glycogen (carbohydrates)

280
Q

What stores of energy are used in response to LONG term starvation?

A

triglycerides (lipids)
Amino acids

281
Q

What happens in the adipose tissue during short term starvation?

A

energy stored in triglycerides is broken down into fatty acids
energy production releases CO2

fatty acids can be sent to liver or muscles

282
Q

What happens in the liver during short term starvation?

A

energy stored in TGs broken down to FAs releases CO2 in energy production

energy stored in glycogen is broken down into glucose (releases CO2)

glucose is transported to the brain

283
Q

What happens in the muscle during short term starvation?

A

TGs broken down to FAs - release CO2
glycogen broken down directly to CO2 (no glucose sent to brain)

284
Q

What happens in the brain during short term starvation?

A

glucose is received from the liver and metabolized into CO2

285
Q

What happens in the adipose tissue during long term starvation?

A

TGs broken down into FAs and metabolized into CO2 or sent to liver

286
Q

What happens in the liver during long term starvation?

A

TG broken down into FAs or FAs received from adipose tissues metabolized into CO2 or ketone bodies

Amino acids in the liver or sent from muscles broken down into CO2 and ketone bodies

ketones sent to brain

287
Q

What happens in the muscle during long term starvation?

A

amino acids in muscles are either sent to liver to be metabolized into ketones OR
are metabolized directly in the muscle to CO2

288
Q

What happens in the brain during long term starvation?

A

ketones from the liver are metabolized into CO2

289
Q

What is the energy source for the brain during short term starvation vs long term?

A

short term = glucose
long term = ketones

290
Q

What produces and sends the energy source to the brain during short term vs. long term starvation?

A

short term: liver produces glucose and sends to brain

long term: liver produces ketones (from AAs, TGs -> FAs) and sends to brain

291
Q

What energy stores does the liver use to produce the energy sent to the brain during short vs long term starvation?

A

short: liver uses glycogen stored IN the liver to produce glucose to send to brain

long: liver uses AAs stored in the liver or sent from muscles to produce ketones to send to brain
or liver uses TGs stored in liver or FAs sent from adipose tissues to produce ketones

292
Q

What happens when the body enters long term starvation?

A

the glycogen stores in the liver and muscles have been used up

the liver now has to use amino acids and TGs to produce ketones to send to the brain for energy

basically a reorganization of metabolism

293
Q

How does the body reorganize metabolism for survival during long term starvation?

A

glucose stores are conserved to protect glucose-dependent tissues (nerves)

muscles start to use lipid metabolism

after lipid and glucose stores are depleted

liver converts AAs, FAs, lipids into ketones

muscular atrophy and structural degradation begins to occur as protein stores are depleted

Animal Physiology (13 decks)

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