physiology Flashcards
1
Q
what is the alimentary canal
A
serious of hollow tubes running from mouth to anus (oral to aboral) separated by sphincters
2
Q
what are the components of the GI tract
A
mouth and oropharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus
3
Q
where is the principle site of digestion and absorption
A
small intestine
4
Q
what happens in the large instestine
A
holds the colon where fluids and electrolytes are reabsorbed and stored as faeces
5
Q
what are the assessory features of the alimentary canal
A
salivary glands, pancreas, liver and gall bladder
6
Q
how long is the GI tract
A
7-10m
7
Q
what are the components of the digestive tract wall
A
mucosa, submucosa, muscularis externa, serosa
8
Q
what is the function of the mucosa
A
fat absorption
9
Q
what dies the muscularis externa do
A
changes shape to facillitate absorption
10
Q
what are the 4 major functions of the alimentary canal
A
motility, secretion, digestion, absorption
11
Q
what is the main type of muscle in the GI tract and what are the exceptions
A
mostly smooth, skeletal in mouth, pharynx, upper oesophagus and external anal sphincter
12
Q
when does secretion occur and what does it do
A
in response to food, hormones or nerves, needed for digestion, protection and lubrication
13
Q
what happens during digestion
A
chemical breakdown by hydrolysis of complex food to absorbable units
14
Q
what happens during absorption
A
transfer from digestive tract to blood
15
Q
when circular muscles contract what happens to the lumen
A
narrower and longer
16
Q
when longitudinal muscles contract what happens to the lumen
A
shorter and fatter
17
Q
adjacent cells are coupled by?
A
gap junctions
18
Q
when the cells depolarise in a synchronous wave what is this called
A
single unit smooth muscle
19
Q
what type of wave occurs in stomach, small and larger intestines
A
slow wave
20
Q
what type of cells cause slow wave depolarisation
A
interstitial cells of Cajal (ICC’s), these are pacemakers
21
Q
where are ICCs found
A
between circular and longitudinal muscle
22
Q
when does depolarisation of slow waves result in contraction
A
when there are frequent enough AP’s to get to the threshold. (AP’s increase force not speed)
23
Q
the upstroke is due to an influx of what
A
Ca++
24
Q
what are short waves also known as
A
basic electrical rhythm
25
what type of outflow is involved in the PARASYMPATHETIC autonomic innervation and which nerves are involved
cranio-sacral, vagus and pelvic nerves
26
where to preganglionic fibres synapse with ganglion cells in parasympathetic.
enteric nervous system.
27
what are the excitatory influences of parasympathetic outflow
increased gastric, pancreatic and small intestinal secretion, increased blood flow and increased muscle contraction
28
what are the inhibitory influences of parasympathetic outflow
relaxation of sphincters, relaxation of stomach
29
what is more significant in the GI tract parasympathetic or sympathetic
parasympathetic
30
where to preganglionic fibres synapse in SYMPATHETIC outflow
prevertebral ganglia, (post release NA)
31
what are excitatory influences of sympathetic outflow
increased sphincter tone
32
what are inhibitory influences of sympathetic outflow
decreased motility, decreased secretion, decreased blood flow
33
what does the enteric nervous system act on
the gut
34
give an example of local, short and long nerve reflexes
local: peristalsis, short: intestino-intestinal inhibitory reflex, long: gastroileal
35
what is peristalsis
wave of relaxation followed by a contraction, usually over short distances and oral-->aboral
36
in the oral section, what muscle relaxes and what contracts
longitudinal relaxes and circular contracts
37
in the aboral section, what muscle relaxes and what contracts
longitudinal contracts and circular relaxes
38
what causes relaxation of longitudinal/ circular muscle
NO and VIP
39
what causes contraction of longitudinal/ circular muscle
ACh and substance P
40
what are the 5 major motility functions of the GI tract
peristalsis, segmentation, colonic mass movement, migrating motor complex (MMC), tonic contractions
41
what happens in segmentation, what is it called in large intestine
rhythmic contractions of circular muscle for mixing/ churning. Occurs in small and large intestine (haustration)
42
what are the 6 sphincters
upper oesophageal, lower oesophageal, pyloric, illeocacal, internal anus, external anus
43
which sphincters are controlled by skeletal
upper oesophageal and external anus
44
food entering the oesophagus does what to stomach
relaxes receptively to prepare, vagus activity
45
What are the 4 main anatomical areas of the stomach?
Fundus
Body
Antrum
Pylorus
46
what are the 2 mechinal sections of stomach
orad and caudad
47
what happens in orad section
relaxes in preparation for food, tonic contractions
48
what happens in caudad section
slow waves (3/min) when threshold met, peristalsis i antrum, propels chyme towards pylorus. also retropulsion of chyme
49
where does mixing occur
antrum
50
What is the substance produced when food mixes with gastric secretions
chyme
51
Name a substance which can be absorbed by the stomach
ethanol
52
What occurs in Retropulsion?
Peristaltic wave forces chyme against closed pyloric sphincter, so chyme bounces back and undergoes more mixing
53
what are some gastric factors promoting gastric emptying
volume of chyme, consistency of chyme, muscle strength, increases vagus nerve and gastrin release
54
Which 2 duodenal factors delay gastric emptying?
```
Enterogastric reflex (decreases antral activity)
Release of enterogastrones (inhibit stomach contractions eg CKK)
```
55
What is the enterogastric reflex?
Duodenum signals to stomach that it has enough chyme so slow down emptying/peristaltic contraction
56
which stimuli in duedendum can decrease stomach emptying
fat, acid, hypertoncity, osmotically active, distension
57
Where is the oxyntic mucosa area located?
fundus and body
58
Where is the pyloric gland area located?
antram
59
Which cells are contained in the oxyntic mucosa amd what do they secrete?
Parietal cells: HCL
Enterochromaffin-like cells (ELC): histamine
Chief cells: pepsinogen
60
Which cells are contained in the pyloric gland area and what do they secrete?
D cells: somatostatin
| G cells: gastrin
61
What does autocatalytic mean with regards to pepsinogen and pepsin?
Pepsin formation triggers further pepsin formation from pepsinogen
62
what does HCL do (oxyntic mucosa)
converts pepsinogen to pepsin, denatures enzymes and kills bacteria (parietal cell)
63
what does histamine do (oxyntic mucosa)
stimulates HCL release (ECL cell)
64
what does pepsinogen do (oxyntic mucosa)
converted to pepsin which breaks down proteins (chief cells)
65
What is the role of intrinsic factor and in the oxyntic mucosa?
Binds vitamin B12
66
What is the role of gastrin in the pyloric gland area?
Stimulates HCl secretion (G cell)
67
What is the role of somatostatin in the pyloric gland area?
Inhibits HCl secretion (D cell)
68
in the parietal cell, which enzyme forms H2CO3 from which to substrates
carbonic anhydrase, Co2 and H2O
69
what does H2CO3 dissociate to
HCO3 (bicarbonate) and H+
70
what does H/KATPase do
actively pumps K in and H+ out at apical end to canaliculus
71
How does bicarbonate exit cell, what enters in the exchanger
antiporter into plasma, chlorine enters
72
what channel does Cl exit to canaliculus
CFTR
73
CL and H then form to make acid true/false
true :)
74
What are Secretagogues?
Substances promoting secretion of HCl (gastrin, ACh, histamine)
75
What are the 3 phases of gastric secretion?
Cephalic
Gastric
Intestinal
76
What is involved in the cephalic phase?
Stomach is prepared to receive food by conditioned reflex, chewing or swallowing, leading to gastric secretion through ACh and GRP
77
What is involved in the gastric phase?
Distension of stomach causes G cells to be activates and D cells to be inhibited
78
what inhibits gastric secretion in cephalic stage
vagal nerve activity once you've stopped eating
79
what inhibits gastric secretion in gastric stage
fall in antral pH after eating, prostaglandin E2 removing histamine
80
what inhibits gastric secretion in intestinal stage
Gastric secretion is halted through secretin, CCK and somatostatin as the stomach empties
81
What is the importance of the mucus gel layer on the surface of mucous secreting cells?
Prevents pepsin/HCl reaching the apical surface of the cells and damaging the cells
82
how does the mucus gel layer prevent damage
produces PGE2 and PGL2 to reduce acid, increases mucous and bicarbonate secretion, increased mucous blood flow
83
Place the parts of the small intestine in order from shortest to longest
Duodenum (0.25m)
Jejunum (2.5m)
Ileum (3m)
84
what does the small intestine recieve
chyme, pancreatic juices, bile from gallbladder
85
Which 3 components increase the SA of the small intestine?
Circular folds
Villi
Microvilli
86
Where is gastrin secreted from?
G cells of stomach + duodenum
87
Where is secretin secreted from?
S cells of duodenum
88
Where is CCK secreted from?
I cells of duodenum + jejunum
89
Where is motilin secreted from?
M cells of duodenum + jejunum
90
Where is ghrelin secreted from?
Gr cells of stomach, small intestine + pancreas
91
what factors increases small intestine secretion
gastrin, CCKm distension and parasympathetic stimulation
92
does segmentation occur in small intestine
yes, to mix chyme,
93
what is the migrating motor complex
strong peristaltic contraction between meals, clears stuff from stomach to ileum, activated by motilin
94
what does the endocrine pancreas secrete
insulin and glucagon
95
what does the exocrine pancreas secrete and from which cells
anicar cells: digestive enzymes
| duct cells: aqueous salts (NaHCO3)
96
where do exocrine secretions go
duodenum
97
explain neutralisation in small intestine (involving pancreas)
duodenum has high acid which causes S cells to release secretin. Secretin travels in blood to pancreas, it then releases aqueous salts from duct cells (NaHCO3) to duodenum lumen
98
explain digestion in small intestine (involving pancreas)
fat and protein in duodenum causes I cells to release CKK in blood to pancreas, it then releases digestive enzymes from anicar cells to duodenum lumen
99
name some forms of carbs
starch, cellulose, disaccharides, glycogen
100
name some types of lipids
triglycerides, free fatty acids, cholesterol, phospholipids
101
what is luminal digestion
digestion by pancreatic enzymes secreted into duodenum
102
what is membrane digestion
by enzymes at brush of epithelial cells
103
what is the combined term for digestion and absorption
assimilation
104
Name two polysaccharides
starch glycogen
105
what are 2 forms of starch
amylose, amylopeptin
106
what bonds does amylose have
alpha 1,4
107
what bonds does amylopeptin have
alpha 1,4 and 1,6 in branches
108
Name two disaccharides (oligosaccharides)
Sucrose
| Lactose
109
Name three monosaccharides
Glucose
Fructose
Galactose
110
what do carbs have to be broken into for absorption
monosaccharides
111
what happens in intraluminal hydrolysis
eg starch --> ogliosaccharides by alpha amylase
112
what happens in membrane hydrolysis
ogliosaccharides --> monosaccharides by ogliosaccharidases
113
what does lactase do
breaks down lactase to glucose and galactose
114
what does maltase do
degrades alpha 1,4 bonds
115
what does isomaltase do
only enzyme that breaks down alpha 1,6
116
what does sucrose hydrolyse
sucrose + glucose --> fructose
117
What is lactose intolerance?
Inability to digest lactose, caused by lactase insufficiency
118
what side of enterocytes are monosaccharides absorbed
apical
119
how doe glucose and galactose enter enterocytes
secondary transport, by SGLT1
120
how does fructose enter enterocytes
facilitated diffusion by GLUT 5
121
how do all monosaccherides exit monocytes
GLUT 2
122
What denatures proteins in the stomach?
HCl
123
Which enzyme cleaves protein into peptides in the stomach and is it essential for digestion
pepsin, no.
124
What are the active enzymes that digest protein in the duodenum from the pancreas
```
Trypsin
Chymotrypsin
Elastase
Procaroxypeptidase A
Procaroxypeptidase B
```
125
What are the ranges for normal BMI?
18.5-25
126
What are the ranges for BMI classed as overweight?
25-29.9
127
What are the ranges for BMI classed as obese?
30-39.9
128
What are the ranges for BMI classed as morbidly obese?
>40
129
How is obesity "a disease of the brain"?
The brain sees new fat/weight as normal, and attempts to lose weight are seen as a threat to survival, so the new weight is defended
130
what part of the brain regulates body weight
hypothalamus
131
Which lesioning part of the hypothalamus causes leanness?
lateral
132
Which lesioning part of the hypothalamus causes obesity
ventromedial
133
define satiation
feeling full during/ end of a meal
134
define satiety
fasting between means
135
when do satiation signals increase and why
when you are eating, Increased signals limit meal size, i.e. you can't eat anymore
136
name some satiation singals
CKK, peptide YY, GLP1, OXM, obestatin
137
What is ghrelin?
a hunger signal
138
what are adiposity signals, give examples
signal fat stores to the brain, leptin and insulin, higher levels = more fat
139
how can obesity affectin leptin and insulin
alter transduction, damage receptors
140
what is the 'food reward'
hedonistic affect, releases dopamine
141
name some ways to tackle obesity
drugs: orlistat
gastric bypass
heat therapy
142
name some types of lipids
Fats/ oils, phospholipids, fatt acids, cholesterol
143
what is emulsion
creating droplets suspending lipids in water to increase surface area.
144
what are the stages of lipid digestion
lingual phase --> gastric phase (gastric lipase in stomach) --> intestinal (small intestine, most important)
145
what is released to the duodenum from the gall bladder in lipid digestion
bile salts
146
what are bile salts released in response to and what do they do
CCK, emulsify lipids
147
what cofactor is needed for pancreatic lipase so it can access triglycerides
colipase
148
how is colipase activated
procolipase --> colipase by trypsin
149
what is a mixed micelle
product of digestion, emulsified globule containing TAGs, esterified cholesterol, bile salts, phospholipids and fatty acids
150
where do short/ medium exit enterocytes to capillaries and how do they do this
basolateral membrane by passive diffusion and membrane fatty-acid translocase
151
how are long fatty acid chains and monoglycerides digested
resnythesized to triglcyerides in the ER and made to chylomicrons
152
how are chylomicrons formed
triglycerides synthesised to cholesterol esters --> chylomicrons and coated with apolipoproteins
153
where are chylomicrons released to
lymphatic system by exocytosis
154
how is cholesterol absorbed
NPC1L1
155
how does NPC1L1 move around the cell
by myosin
156
how is Ca absorbed
passive diffusion in small intestine, is regulated by calcitrol
157
what does Vit D do in relation to Ca absorption
increased expression for Ca channels when Ca conc is low
158
what binds to Fe2+ in the stomach
gastroferrin
159
how does Fe2+ enter cells
contransporter iron
160
which acid is absorbable ferric or ferrous
ferrous (Fe2+) is bit ferric (Fe3+) is not, must be converted
161
how does haem increase iron levels in the blood
degradation of haem oxidase
162
what is the storage form of iron
ferratin
163
what are the fat soluble vitamins
ADEK
164
how is vit B12 absorbed
haptocorin binds to vitB12 in stomach, stomach parietal cells release intrinsic factor and in small intestine the intrinsic factor binds to it. It is then absorbed by endocytosis
165
what diet can lead to vit B12 deficiency
vegans, only present in animal produce
166
what is the large intestine made up of
caecum and appendix, ascending, transverse, descending and sigmoid colon, rectum, anal canal and anus
167
what type of muscle is in the caecum and colon
longitudunal smooth muscle that divides into 3 strands called taeniae coli
168
what surrounds the internal anal sphincter
the external skeletal sphincter
169
what does the colon mainly absorb
Na, Cl and H2O, also short chain fatty acids
170
what does the colon mainly secrete
K, HCO3 and mucus
171
what are the 4 functions of the colon
absorption, secretion, storing faeces and eliminating faeces
172
what does the colon have instead of villi
colonic folds, crypts and microvilli
173
what do epithelial cells (colonocytes) mediate in the colon
electrolyte absorption
174
what do crypt cells mediate
ion secretion
175
what do goblet cells secrete
mucous
176
what are haustra
saccule in colon from haustration
177
what is the mass movement of the colon, what reflex causes it
contraction of large sections of the colon at the same time towards the rectum, gastrocolic response
178
describe the defaecation reflex
reflex stretch receptors activate pelvic nerve, activates parasympathetic efferents causing internal sphincter to relax (rectum not normally filled with faeces)
179
which nerves control the external anal sphincter
pudenal nerve (S2,3,4)
180
why are colonic flora important
compete with pathogenic microbes, promote motility,, synthesise vit K2 and free fatty acids
181
what is flatus
intestinal gas, from swallowed air, bacteria and gases
182
what can cause constipation
enhances absorption of H20, suppressing the need, decreases motility obstruction, hirschprung disease
183
what can hardened calcified matter cause
appendicitis
184
how does chyme enter the caecum
through ileocal valve by gastroileal reflex in response to gastrin and CCK
185
what does the caecum relax in response to
distension of the duodenum
186
where is the appendix attached to the caecum
distal via appendiceal orifice
187
what can happen if appendiceal orifice is obstructed by faecalith
appendicitis
188
when should laxatives and purgatives not be used
bowel obstruction
189
what can laxatives be used for
to increase peristalsis and soften faeces, clean bowel before surgery, when pooing is sore
190
name 2 chronic bowel disease
irritable (IBS) and inflammatory (IBD)
191
what causes vomiting and nausea
reverse peristlasis from upper
192
where is the vomiting centre (VC)
medulla oblongata
193
describe how the mediator is released in the vomiting pathway
toxic materials in gut lumen stimulate enterchromaffin cells in mucosa to release mediates (5-HT)
194
describe how the nerves cause vomiting in pathway
sensory afferent terminals in mucosa depolarise, AP discharge in vagal nerve afferents to brainstem, VC causes you to throw up
195
what are the events of vomiting
sphincters relax and retrograde contractions from ileum to stomach. proceeded by lack of saliva, sweating, high BP and nausea
196
what are some consequences of severe vomiting
dehydration, loss of protons and chloride (met alkalosis), raised pH, hypokalaemia
197
how much water is lost on faeces, what else does it contain
100ml, cellulose, bilirubin and bacteria
198
what is the main solute that drives absorption of water
Na
199
what are the major mechanisms in postorandiral period in jejunum
Na/glucose co-transport and Na/ amino acid co-transport
200
do cAMP and cGMP increase or decrease NaCl absorption
decrease
201
what is the definition of diarrhoea
loss of fluid and solutes in excess of 500ml a day
202
what can cause diarrhoe
infectious agents, chronic disease, toxins, impaired absorption of NaCl, excession secretion of Cl and Na (cholera), poorly absorbable intestinal lumen
203
what are some consequences of diarrhoea
dehydration (Na+H2O loss), metabolic acidosis (HC03 loss), hypokalaemia
204
how does rehydration therapy work
Na and glucose translocate from extracellular to intracellular and water follows
205
how do opiods act as anti-diarrhoeal
increase fluid absorption, contrict pyloric, iliocaecal and anal sphincters and decrease peristalsis
206
name some opiods
codeine, diphenoxylate (least abuse potential), loperamide
207
what 3 things does the liver metabolise
carbs, fat and protein
208
describe carb metabolism in the liver
gluconeogenesis, glycogenesis, glycogenolysis
209
describe fat metabolism in the liver
processes chylomicron remains and synthesises lipoproteins and cholesterol, ketogenesis
210
what does the liver degrade
insulin, glucagon, ADH, steroid hormones
211
what does the liver activate
thyroid --> throxine, vit D
212
what does the liver store
fat soluble vitamens (ADEK), water soluble vit b12, iron copper, glycogen
213
what does the liver synthesis
coagulation factors (II, VII, IX, X), albumin, apoliproteins
214
what does the liver do for protection
kupffer cells digest and destroy old and bad stuff. produce immune cells
215
what does the liver detoxify
bilirubin, drugs and ethanol
216
where is bile stores and concentrated between meals
gall bladder
217
how is bile released during a meal
chyme stimulates gall bladder to contract (via CCK and vagal impulses), sphincter of Oddi opens via CCK and bile exits
218
where is primary bile secreted and what does it contain
hepatocytes: cholic + chenodeoxycholic acids
219
what is the most common bilary system problems
cholelithiasis (gall stones), happens when bile crystallises
220
what is best treatment for gall stones
laparoscopic cholectystectomy
221
how are bile salts recycled
enterohepatic recycling
222
how are some primary bile acids converted to secondary
dehydroxylated by bacteria and returned to liver
223
what does the liver do to drugs
converts them to less pharmacologically active metabolites
224
where does phase 1 happen and what does it do
right side, makes drugs more polar eg oxidation, reduction, hydrolysis
225
where does phase 2 happen and what does it do
conjugation, adding something. glucuronidation is common
226
what mediates oxidation reactions in phase I
CYP450
