Gastrointestinal System + Neurophysiology Flashcards
(434 cards)
1
Q
Why do we have a digestive system?
A
We need nutrients (chemical energy, building new body tissues, repair damaged tissues)
Foods need to be broken down into smaller molecules to be absorbed by cells
Digestive system optimised for processing food (extensive surface area, in contact with external environment)
2
Q
What is the gastrointestinal tract (GI) tract?
A
A continuous tubular system
Extends from mouth to anus
5-7 metres long
Physiological barrier between the outside world and the body
Segmental heterogeneity (different parts adapted for different functions)
3
Q
What are the 6 processes of the digestive system?
A
Ingestion
Secretion
Motility
Digestion
Absorption
Defecation
4
Q
The mucosa layer of the GI Tract is a mucous membrane.
It is formed of 3 layers. What are they?
A
- Epithelial Layer - direct contact with contents of GI tract. Simple columnar epithelium with tight junctions to restrict leakage. Exocrine cells secrete mucus and fluid. Enteroendocrine cells secrete hormones
- Lamina Propria
Connective tissue. Blood and lymphatic vessels for nutrient absorption. Mucosa associated lymphatic tissue MALT - Muscularis mucosae
Smooth muscle fibres. Creates folds in the mucous membrane
5
Q
What are the layers 2-4 of the GI Tract?
A
Submucosa
Muscularis
Serosa
6
Q
What are the accessory organs of the GI tract?
A
Teeth
Tongue
Salivary glands
Liver
Gall bladder
Pancreas
7
Q
Digestive system is composed of the … and …
A
GI tract
Accessory organs
8
Q
What does the GI tract include?
A
Mouth, pharynx, oesophagus, stomach, small intestine, large intestine and anus
9
Q
What 4 layers is the GI tract composed of?
A
Mucosa
Submucosa
Muscularis
Serosa
10
Q
What are the functions of the stomach?
A
Mix saliva, food and gastric juice = CHYME
Act as a reservoir for food before release into small intestine
Secrete gastric juice
Digestion starts - protein, triglycerides…
Secrete gastrin into blood (peptide hormone, stimulates secretion of gastric juice)
11
Q
What is gastric juice composed of?
A
HCL - kills bacteria and denatures protein
Pepsin - start protein digestion
Intrinsic factor - absorption of vitamin B12
Gastric lipase - digestion of triglycerides
12
Q
What cells make up the gastric pits?
A
Surface mucous cell - secretes mucus
Mucous neck cell - secretes mucus
Parietal cell - secretes hydrochloric acid and intrinsic factor
Chief cell - secretes pepsinogen and gastric lipase
G cell - secretes the hormone gastrin
13
Q
Movement through the stomach is driven by 3 processes. What are they?
A
Propulsion - peristaltic wave moves gastric contents from body to antrum
Retropulsin - food particles too large to fit through pyloric sphincters. Forced back into body of stomach
Gastric emptying - chyme passes through pyloric sphincter. 3ml chyme at a time.
14
Q
What is the small intestine?
A
Adapted for digestion and absorption
Large surface area (circular folds, villi, microvilli)
Three regions (duodenum, jejunum, ileum)
15
Q
What are the functions of the small intestine?
A
Segmentations - mix chyme with digestive juices. Bring food into contact with mucosa for absorption
Peristalsis - propels chyme through small intestine
Digestion’s - completes digestion of carbohydrates, proteins and lipids. Starts and ends nucleic acid digestion
Absorption - 90% nutrients and water passing through digestive system
16
Q
Peyer’s patches in the ileum are located in the lamina propria layer of the mucosa.
What are their function?
A
GALT - gut associated lymphoid tissue
They catch microorganisms and other antigens entering the intestinal tract. Dendritic cells, B lymphocytes and T lymphocytes
Peyer’s patches are covered by a special epithelium that contains micro fold cells (M cells)
17
Q
What do Brunner’s glands in the duodenum do?
A
Secrete alkaline mucus
Neutralises gastric acid in the chyme
18
Q
Where does most of the digestion and absorption take place?
A
Small intestine
19
Q
What are the Teniae Coli of the large intestine?
A
3 bands of thickened longitudinal muscle
Separated by portions of the wall with less or no longitudinal muscle
Tonic contractions gather the colon in pouches called HAUSTRA
20
Q
What is the function of the large intestine?
A
Haustral churning and peristalsis
Drive contents into rectum
Bacteria are present in large intestine (micro biome). Convert proteins to amino acids. Breakdown amino acids. Produce some B vitamins and vitamin K
Absorption of some water, ions and vitamins
Formation of faeces
Chyme in the large intestine for 3-10 hours
Defecation
21
Q
What are the 4 major regions of the large intestine?
A
Cecum, colon, rectum and anal canal
22
Q
What cells make up the small intestine?
A
Absorptive cell - digests and absorbs nutrients
Goblet cell - secretes mucus
Enteroendocrine cell - secretes hormone secretin, cholecystokinin or GIP)
Paneth cell - secretes lysozyme abs is capable of phagocytosis
23
Q
What cells make up the large intestine?
A
Absorptive cell - absorbs water
Goblet cell - secretes mucus
24
Q
What does the mouth do / what does it contain?
A
Mechanical digestion - mastication. Food > bolus
Salivary glands - food dissolves. Amylase = digestion of starch
Swallowing - extrinsic and intrinsic tongue muscles
25
The pharynx is a funnel shape tube with skeletal muscle lined by a mucous membrane.
What does it consist of?
3 parts
Nasopharynx - respiratory function
Oropharynx + Laryngopharynx - respiratory and digestive function
Swallowed food goes from mouth to Oro and Laryngo
26
What is deglutition (swallowing)?
Movement of food from mouth to stomach (via pharynx and oesophagus)
3 stages of swallowing:
Voluntary - into oropharynx
Pharyngeal - into the oesophagus
Oesophageal - into the stomach
27
What is the central nervous system CNS?
Brain and spinal cord
28
What is the peripheral nervous system PNS?
Nerves and ganglia OUTSIDE the CNS. Connect the CNS to the limbs and organs
Somatic nervous system - voluntary muscular.
Autonomic nervous system - largely unconscious. Smooth muscle and glands
29
What is the autonomic nervous system?
Sympathetic ‘fight or flight’
Parasympathetic ‘feed and breed’ or ‘rest and digest’
Enteric nervous system - GI tract
30
What does the myenteric plexus regulate?
GI tract motility
31
What does the submucosal plexus regulate?
Regulates GI secretion
32
What do parasympathetic fibres of GI tract do?
Increase GI tract secretion and motility
Increase activity of ENS neurons
33
What do sympathetic fibres of GI tract do?
Decrease GI tract secretion and motility
Inhibit ENS neurons
34
Neural regulation is a gastric phase of digestion where food enters the stomach.
What else happens?
Stretch receptors stimulated by gastric distension
Chemoreceptors activated if pH increases with protein
Nerve impulses to the submucosal plexus (secretions)
Negative feedback loop
35
What are the stages of gastric phase of digestion?
1. Food enters the stomach. Ph increases and activates chemoreceptors. Stomach walls are stretched and activates stretch receptors
2. Nerve impulses sent to submucosal plexus. Parasympathetic neurons activated. OUTPUT: stomach (parietal cells, smooth muscle)
3. Parietal cells secrete HCL. Smooth muscle contracts
4. Increase in acidity of stomach chyme. Stomach contents are mixed. Stomach empties.
5. Negative feedback loop. pH reduces. Stomach returns to pre eating state
36
Gastrin is released from the G cells of the gastric glands in response to:
Distension of the stomach by chyme
Partially digested proteins in chyme
High pH of chyme due to the presence of food in the stomach
Caffeine in gastric chyme
Acetylcholine released from parasympathetic neurons
37
Gastrin is released into bloodstream and stimulates gastric glands which:
Secrete large amounts of gastric juice
Strengthens the contraction of lower oesophageal sphincter
Prevents reflux of acid chyme into oesophagus
Increases motility of stomach
Relaxes the pyloric sphincter to promote gastric emptying
38
Gastrin secretion is inhibited when… and is stimulated when…
It ensures optimal low pH for…
pH of gastric juice drops below 2.0
pH rises
Functioning of pepsin, killing of microbes, denaturing of proteins in the stomach
39
Smooth muscle contractions are initiated at the Interstitial cells of Cajal (pacemaker).
What do they generate?
Spontaneous electrical slow waves
40
Slow waves differ between regions. What do slow waves generate?
Phasic contractions - Peristalsis
Peristaltic wave moves gastric contents from body to antrum (propulsion)
41
What is absorption?
What substances can be absorbed without undergoing digestion?
Movements of products via digestion from lumen of GI tract into blood or lymph
Water, vitamins, ions, cholesterol
42
The small intestine has less … so more …
Tight junctions
Paracellular movement
43
What is passive transport of molecules?
No energy required
Moving down the concentration gradient
Diffusion - simple / facilitated
Transmembrane proteins
44
What is active transport of molecules?
Energy required
Move against concentration gradient
ATP hydrolysis - ATPase Na+ / K+ exchange
Ion gradient - energy released during movement of inorganic ion down a gradient
Pump solutes against their gradient - anti Porter, symporter
45
What is the importance of sodium and potassium?
Two primary electrolytes
Important for maintaining fluid balance in the body
Blood pressure
Nerve and muscle function
46
What are the 3 mechanisms of sodium absorption from the lumen?
Co transport with nutrients (1 glucose: 2 Na+)
In exchange for H+
Specific sodium channels
47
What happens during sodium transport?
Na+ actively transported out of absorptive cells
Basolateral sodium potassium pumps (Na+ - K+ ATPases)
Most of Na+ ions in GI secretions are reclaimed (not lost in faeces)
48
What happens during potassium transport?
Small intestine absorbs potassium
Large intestine secretes potassium
Potassium balance regulated by aldosterone
Loss of potassium in faeces
49
What is aldosterone?
Mineralcorticoid
Secreted by adrenal cortex
Regulates homeostasis of Na+ and K+
50
Water is bi directional, moves due to osmosis, diffusion and through aquaporins.
What is the paracellular and trans cellular route?
Paracellular - between cells. Through tight junctions. SLOW
Transcellular - through cells. Water channels. Aquaporins increase trans cellular flux. FAST
51
Summary of Sodium:
Sodium absorption is efficient with only 0.5% of intake lost in faeces
Primary mechanism for absorption - coupled transport to movement of glucose, amino acids and fatty acids after a meal
Absorbed sodium rapidly leaves the basolateral side of the cell (sodium pumps)
Increases the osmolarity in the intracellular space
52
Summary of potassium:
Small intestine absorbs potassium
Large intestine secretes potassium
Potassium balance regulated by aldosterone
53
Summary of water:
Diffuses in response to osmotic gradient established by sodium
Most movement is trans cellular through aquaporins
54
What are the dietary carbohydrates?
Monosaccharide - glucose, fructose, galactose
Disaccharide - maltose, sucrose, lactose
Polysaccharide - starch
Most carbohydrates we eat are starches
Only monosaccharides can be absorbed into bloodstream
Ingested disaccharides and starch must be broken down into monosaccharides
55
Starch is a polysaccharide of glucose monomers joined by glycosidic bonds.
What are amylose and amylopectin?
Amylose - linear polymer. 200-1000 glucose units
Amylopectin - branched polymer. 2000-200 000 glucose units.
Increased surface area.
High in rice, potato and sweet potato.
Glycogen (storage in animal tissues) has same structure
56
What is the carbohydrate digestion pathway?
Mouth to stomach (not all starch is broken down in mouth, food swallowed too quickly)
Salivary glands
Salivary amylase continues to act on swallowed food for -1hr
Stomach acid (low pH) inhibits enzymatic activity
Breakdown of starch into:
Maltose - disaccharide
Maltotriose - trisaccharide
a dextrin - short chain glucose polymer
57
What bonds is a dextrin linked by?
D glucose units linked by a (1-4) or a (1-6) glycosidic bonds
58
What is the purpose of the liver in the carbohydrate digestion pathway?
Maintains normal blood glucose level
Low: breakdown glycogen to glucose. Convert certain amino acids, lactic acid, fructose and galactose to glucose
High: glucose to glycogen and triglycerides for storage
59
What is the purpose of the small intestine in the carbohydrate digestion pathway?
Intestinal juice
Absorptive cells synthesise several digestive enzymes:
Brush border enzymes, plasma membrane of microvilli, a dextrinase, maltase, sucrase, lactase
60
Absorption of monosaccharides:
120g/h of monosaccharides absorbed in the …
All dietary carbohydrates absorbed except … and …
Small intestine
Cellulose
Fibre
61
How is fructose absorbed?
How are glucose and galactose absorbed?
Facilitated diffusion
Secondary active transport
62
What is the purpose of the large intestine in the carbohydrate digestion pathway?
Bacteria - ferment any remaining carbohydrates. Hydrogen, carbon dioxide and methane gas
63
Mumps is inflammation and enlargement of the parotid glands.
What is cause, symptoms and treatment?
Cause: mumps virus (paramyxovirus)
Symptoms: moderate fever, extreme pain in the throat, swelling on side of face
Treatment: vaccine
64
Gastro oesophageal reflux disease GORD is where the stomach contents reflux into oesophagus.
What is cause, symptoms and treatment?
Cause: lower oesophageal sphincter fails to close properly after food enters stomach
Symptoms: burning sensation in oesophagus (heartburn)
Hydrochloric acid HCL
Treatment: avoid drinking alcohol and smoking. Antacids. Avoid foods that stimulate stomach acid secretion - coffee, chocolate, orange juice
65
What is the mechanism of vomiting?
Nerve impulses to medulla oblongata
Returning impulses result in squeezing the stomach between diaphragm and abdominal muscles
Contents expelled through open oesophageal sphincters
66
Prolonged vomiting can be serious. Why?
Loss of gastric acid juice = alkalosis (higher than normal blood pH). Dehydration. Damage to the oesophagus and teeth
67
Pancreatitis is inflammation of the pancreas.
What is cause, symptoms and treatment?
Cause: primary - alcohol abuse (70% of cases). Chronic gallstones.
Mechanism: heavy alcohol intake or biliary tract obstruction, pancreatic cells release trypsin. Trypsin begins to digest pancreatic cells.
Treatment: fluids, oxygen, painkillers. Long term avoid alcohol, diet, surgery
68
Hepatitis is inflammation of the liver.
What is cause, symptoms and treatment?
There is Hepatitis A, B, C, D, E
Causes: viruses, drugs, chemicals, alcohol
Treatment: Vaccines
69
Peptic ulcers are are lesion in the GI tract membrane.
What is cause, symptoms and treatment?
Cause: helicobacter pylori bacteria - urease enzyme splits urea into ammonia and CO2, ammonia shields bacterium from acidity and damages mucosal layer
NSAIDS
Hypersecretion of HCL
Treatment: avoid smoking, caffeine, alcohol, antibiotics. Proton pump inhibitors eg. Omeprazole blocks secretion of H+ from parietal cells (HCL hypersecretion)
70
Crohn’s disease is inflammation of the GI tract. A chronic condition.
What is cause, symptoms and treatment?
Symptoms: diarrhoea, stomach aches and cramps, blood in stool, fatigue, weight loss
Causes: autoimmune, smoking, genetics
Treatment: immunosuppressants eg steroids. Surgical procedures
71
Diarrhoea is increase in frequency, volume and fluid content of faeces
What is cause, symptoms and treatment?
Outcome: dehydration, electrolyte imbalances
Causes: lactose intolerance, stress, microbes irritating gastrointestinal mucosa
72
Constipation is infrequent or difficult defection.
What is cause, symptoms and treatment?
Mechanism: decreased motility of intestines, faeces remain in colon for prolonged periods, excessive water absorption leading to dry and hard faeces
Causes: poor habits, colon spasms, insufficient dietary fibre and fluid intake
Treatments: mild laxative eg milk of magnesia, increase dietary fibre and fluid intake
73
Why do we have biological clocks?
Anticipate and prepare for predictable environmental changes
Optically synchronised with the environment
Adapt to changing environments
74
What does circadian mean?
Circadian: drive 24hr rhythms in physiology and behaviour
75
What are rhythms in physiology?
Lung function
Cardiovascular
Muscle function
Metabolism
76
Sleep deprivation can be…
Acute - single night of sleep loss
Chronic - persistently short sleep episodes
77
Health risks in shift work? (Night shifts etc)
Obesity and weight gain
Type 2 diabetes
Coronary heart disease
Breast, prostate and colorectal cancer
Occupational accidents
78
Sleep restriction affects metabolism by:
Impairs glucose tolerance
Reduced acute insulin response
Risk factor: diabetes, obesity, hypertension
79
The appetite hormones:
What is ghrelin?
Leptin?
Ghrelin - produced by enteroendocrine cells of GI tract (stomach). Hunger hormone. Highest levels before meals
Leptin - adipose cells and enterocytes in small intestine. Inhibits food intake. Increases energy expenditure.
80
How does sleep restriction affect appetite?
Sleep restriction for 2 days: increases ghrelin, decreases leptin
Increased food intake
Decreased energy expenditure
81
Proteins are polymers of amino acids linked via peptide bonds.
Describe primary, secondary, Tertiary, quaternary structure.
Primary - linear (not branched) chain with defined amino acid sequence
Secondary - local folding of peptide chain (alpha helix,beta pleated sheet)
Tertiary - overall 3D structure
Quaternary - interaction of multiple proteins in complexes
82
What are the proteolytic enzymes, exopeptidase and endopeptidases?
Exopeptidase enzymes - carboxy or amino peptidases. Liberate free amino acids
Endopeptidases - liberate smaller peptide chains
83
The digestion of proteins involves the mechanical disruption by chewing and gastric motility. What else does it involve?
Protein denaturation by HCL
Combined effect of chemical and enzymatic digestion
84
Stomach is where enzymatic digestion of proteins begins. What is the role of pepsin there?
Secreted by chief cells. Most effective in the very acidic environment of the stomach (around pH2). Becomes inactive at higher pH
Cleaves certain peptide bonds between amino acids. Breaks peptide bonds adjacent to phe, try, tyr, aps, glu, leu, met
85
What prevents pepsin from digesting the protein in stomach cells?
1. Pepsin is secreted in an inactive form = pepsinogen. Pepsinogen is converted into active pepsin when it comes into contact with HCL secreted by parietal cells + active pepsin molecules.
2. Stomach epithelial cells protected from gastric juices. Later 1-3mm thick of alkaline mucus. Secreted by surface mucous cells and mucous neck cells
86
The small intestine contains pancreatic juice in an inactive form to protect the pancreas.
How?
Trypsin secreted in an inactive form called trypsinogen
Pancreatic acinar cells secrete trypsin inhibitor
Blocks enzyme activity of any trypsin formed accidentally in the pancreas or in pancreatic juice
87
How are proteins digested in the small intestine?
Trypsinogen reaches the lumen of the small intestine. Activates brush border enzyme = enterokinase. Splits off part of trypsinogen = trypsin
Trypsin acts on other inactive precursors:
Chymotrypsinogen = chymotrypsin
Procarboxypeptidase = carboxypeotidase
Proelastase = elastase
88
How is protein digestion completed by 2 peptidases in the brush border?
Aminopeptidase - cleaves off the amino acid at the amino end of a peptide
Dipeptidase - splits dipeptides (two amino acids joined by peptide bond) into single amino acids
89
Most proteins are absorbed as amino acids via active transport process in duodenum and jejunum.
Where are these absorbed AA found?
50% of absorbed AA are present in food
50% from the body - proteins in digestive juices + dead cells sloughed off mucosal surface
95-98% of the protein present in the small intestine is digested and absorbed
90
How are proteins absorbed?
Na+ dependant amino acid transport
H+ co transport with small peptides
Larger peptides moved by transcytosis
91
Amino acids are transported in blood to … (hepatic portal system)
Hepatocytes … (remove NH2) amino acids
Toxic ammonia NH3 converted to mixh less toxic … (excreted in the urine)
Hepatocytes … most plasma proteins - alpha and beta globulins, albumin, prothrombin and fibrinogen
Liver
Deaminate
Urea
Synthesise
92
How is the mouth involved in lipid digestion?
Lingual glands in the lamina propria of tongue
Secrete mucus and lingual lipase
Acts on 30% of dietary triglycerides (fats and oils)
Converts them to simpler fatty acids and diglycerides)
93
How is the stomach involved in lipid digestion?
Chief cells
Gastric lipase - operates best at pH 5-6
Splits triglycerides into fatty acids and monoglycerides.
Monoglyceride = glycerol molecule + one fatty acid molecule
94
How is the small intestine involved in lipid digestion?
Most lipid digestion occurs here
Pancreatic juice - pancreatic lipase
Bile salts - emulsification
Triglycerides broken down into fatty acids and monoglycerides
Short chain fatty acids = fewer than 10-12 carbons. Hydrophilic - more water soluble.
Long chain fatty acids - hydrophobic = not water soluble
95
Pancreatic lipase is made up of 3 different enzymes what are they?
Triglycerol hydrolase
Cholesterol ester hydrolase
Phospholipase A2
96
What is the action of pancreatic lipase?
(Triaglycerol hydrolase)
Specific for 1st and 3rd ester bonds
Maximal enzymatic efficiency requires:
Colipase - stabilises active catalytic site, prevents inactivation by bile salts
Alkaline pH
Bile acids for emulsification
97
Bile salts are sodium and potassium salts of bile acids.
They are amphipathic what does this mean?
What does emulsification mean?
Amphipathic - hydrophobic non polar region
Hydrophilic polar region
Emulsification - hydrophobic region interacts with large lipid globule
Hydrophilic region interacts with watery intestinal chyme
Large lipid globule broken apart into several small lipid globules (1um in diameter)
98
Emulsification is crucial for … the surface area for … action
Increasing
Lipase
99
What are micelles and what do they do?
Increase solubility
20-50 bile salt molecules
Hydrophobic regions of bile salts interact with fatty acids and monoglycerides
Hydrophilic regions interact with watery intestinal chyme
100
Summary of lipid digestion:
Emulsification by…
Formation of mixed …
Micelle breaks down close to … low pH of acid microclimate zone
Fatty acids are …
Bile salts
Micelles
Luminal surface
Released
101
Summary of lipid absorption :
All dietary lipids are absorbed via …
Adults absorb about … of lipids present in small intestine
Small short chain fatty acids pass through absorptive cells via …
Micelles move to … of absorptive cells
Long chain FA and monoglycerides diffuse out of cell into …
Micelles remain in …
Micelles continually repeat … function
- pick up more short chain, long chain FA and monoglycerides
Micelles also solubilise other large … molecules. Fat soluble vitamins (A,D,E,K) and cholesterol.
Simple diffusion
95%
Simple diffusion
Brush border
Absorptive cells
Chyme
Ferrying
Hydrophobic
102
What happens inside absorptive cells - lipid absorption?
Long chain FA and monoglycerides combine to = triglycerides
Aggregate into globules along with phospholipids and cholesterol to become coated with proteins
Chylomicrons - large spherical masses. Leave absorptive cells via exocytosis - cannot enter blood capillaries as too large!
103
What does the hydrophilic protein coat do in lipid absorption?
Keeps chylomicrons suspended in blood, prevents them from sticking to eachother
Within 10 minutes 50% chylomicrons have been removed from blood
2-3 hours after a meal few chylomicrons remain in the blood
104
What does lipoprotein lipase do?
Breaks down triglycerides in chylomicrons and other lipoproteins into fatty acids and glycerol
105
What is enterohepatic circulation?
What happens when there’s insufficient bile salts?
Most bile salts are reabsorbed by active transport in the iluem
Returned by the blood to the liver through hepatic portal system
Re secreted into bile
Insufficient bile salts - obstruction of bile ducts, removal of gall bladder, diminished lipid absorption, loss of up to 40% of dietary lipids in faeces
106
What happens during lipid metabolism in the liver?
Hepatocytes store some triglycerides
Break down fatty acids to generate ATP
Synthesise lipoproteins - transport FA, triglycerides and cholesterol to and from body cells
Synthesise cholesterol
Use cholesterol to make bile salts
107
What is the importance of healthy fats in the diet?
Delay gastric emptying - helps a person feel full
Enhance the feeling of fullness by triggering the release of CCK
Necessary for absorption of fat soluble vitamins
108
Amino acids are processed by the …
Liver
109
Dietary fat consists mainly of …
Triaglycerol
110
Majority of lipid digestion involves:
Pancreatic enzymes
Bile
111
Bile salts are critical for forming …
Micelles
112
Absorbed lipids form into … within the enterocyte are are released into the lacteals
Chylomicrons
113
What is cholecystokinin CCK and what is it released in response to?
Released from CCK cells of intestinal glands in small intestine
Released in response to chyme containing - amino acids (partially digested proteins) and fatty acid (partially digested triglycerides)!
114
What does cholecystokinin CCK simulate?
Satiety via hypothalamus
Slows gastric emptying - contraction of pyloric sphincter
Secretion of pancreatic juice (digestive enzymes)
Contraction of the wall of the gallbladder
Promotes normal growth and maintenance of the pancreas
Enhances the effects of secretin
115
Secretin is released from S cells of intestinal glands in small intestine.
What is it released in response to?
Acidic chyme entering the duodenum
116
What does secretin do?
Inhibits secretion of gastric juice
Increases flow of pancreatic juice - high in bicarbonate HCO3- ions to buffer acidic chyme
Promotes normal growth and maintenance of the pancreas
Enhances the effects of CCK
117
What are segmentations?
(Small intestinal motility)
Portions of intestine distended by chyme
Do NOT push contents along the tract
Localised, mixing contractions
Mix chyme with digestive juices
Bring food into contact with mucosa for absorption
Speed varies
Duodenum = 12 per minute
Iluem = 8 per minute
118
Peristaltic contractions are responsible for … in small intestine.
Forward movement
119
What are the phases of the migrating motor complex?
Phase 1: quiescence
Phase 2: intermittent and irregular activity
Phase 3: short period of intense activity
Phase 4: quiescence
120
What are the general principles of GI tract motility?
All segments have 2 forms of motility: mixing and propulsion
Main stimulus for contraction is distension: enteric nervous system
Distension in the region of GI tract immediately before a sphincter causes it to open - otherwise it’s toncially contracted
Distension and absorption in 1 segment will inhibit contraction and motility in preceding segment
Eg SI activity inhibits the stomach.
Makes the gut more energetically efficient
121
What are the 3 phases of secretion in the GI tract?
Cephalic Phase: pre ingestion and food in mouth
Gastric phase: food in stomach
Intestinal phase: food in small intestine
122
What is the cephalic phase?
Initiated when receptors in the head (cephalic) are stimulated - thought, sight, smell and taste of food
Involves parasympathetic nervous system
Prepares body for influx of food
‘Pavlov’s Dog’
123
What secretions are stimulated during cephalic phase?
FEED FORWARD MECHANISM
Salvia production
Gastric acid
Gallbladder contraction - releasing bile into SI
Exocrine pancreatic secretions - releasing HCO3 and enzymes into SI
124
What happens during the gastric phase?
Food now in the stomach
Secretion of HCL
Pepsinogen (protease enzyme)
Intrinsic factor - to allow ileal abosrption of vitamin B13
Production of the mucus bicarbonate layer
125
What is the purpose of HCO3 - and prostaglandins in the gastric phase?
HCO3 - creates a micro environment around surface cells to prevent damage
It is inhibited by sympathetic NS
Prostaglandins - increase mucus production. Inhibition of enzymes of prostaglandin production results in gastric damage eg NSAIDS
126
What is the intestinal phase?
Inhibition of gastric acid secretion
HCO3- secretions neutralise acidic chyme from stomach
Bicarbonate can come from pancreas and duodenal brunners gland
Secretion of digestive enzymes (pancreas) and bile (liver)
127
What does pancreatic exocrine secretion contain?
Acini clusters contain Zymogen granules with digestive enzymes
Pancreatic juice, watery solution of enzymes and HCO3-
Proteases secreted in an inactive form to prevent auto digestion
Amylase (starch) and lipases (Triaglycerol) secreted in ACTIVE form
128
What are primary bile salts?
What is bile fluid?
Synthesised from cholesterol in hepatocytes
Cholic acid
Chenodeoxycholic acid conjugated with glycine or taurine - secreted as Na+ salts which increase solubility
Bile fluid - watery secretion
Contains HCO3- from epithelial cells lining the bile canaliculi
129
What is enterohepatic circulation?
Bile salts released into small intestine
Little reabsorption from duodenum or jejunum
90-95% reabsorbed from ileum (passive + active)
Bile salts returned to liver via portal vein and taken up by hepatocytes and re secreted
Bile salt pool recycled up to 10 times per day, at least 3-8% lost in faeces per day
130
Secondary bile salts are formed by bacteria by dehydroxylation of primary bile salts.
Examples?
Deoxycholate from cholic acid
Lithocholate from chenodeoxycholic acid - poorly absorbed, TOXIC
131
3 reasons why the body needs nutrients
Energy
Building
Repair
132
Name 3 accessory organs to the GI tract
Salivary glands
Tongue
Teeth
133
Two functions of the stomach
Produce chyme, act as a reservoir, produce gastric juice, secrete gastrin
134
Four components of gastric juice
HCL
Pepsin
Gastric lipase
Intrinsic factor
135
What structures in small intestine increase surface area
Circular folds
Villi
Microvilli
136
What is function of segmentations
Mix chyme with digestive juices
Bring chyme into contact with mucosa for absorption
137
What is located in Peyer’s patches?
Gut associated lymphoid tissue
138
What are the 3 stages of swallowing?
Voluntary
Pharyngeal
Oesophageal
139
What does the myenteric plexus layer of the enteric nervous system control?
GI tract motility
140
What receptors are activated when food enters the stomach?
What are the 2 outcomes of this activation?
Stretch and chemoreceptors
Increased secretion of HCL and stomach wall contractions
141
What impact does gastrin have on sphincter muscles?
Lower oesophageal contraction strengthens, pyloric relaxes
142
Where are the spontaneous slow waves initiated in the stomach?
Interstitial cells of Cajal
143
What are the 2 actions of CCK?
Indicate satiety
Slows gastric emptying
Secretion of pancreatic juice
144
What is the function of the mucosal layer in the stomach?
Protect against damage - from HCL and pepsin
145
What does sensation mean?
The conscious or subs conscious awareness of changes in the external or internal environment
146
What does perception mean?
Conscious interpretation of sensations
Primarily a function of the cerebral cortex
147
What are the general senses?
Somatic - tactile (touch, pressure) , thermal, pain and proprioceptive sensations
Visceral - conditions within internal organs eg stretch, chemicals, nausea, hunger
148
What are the special senses?
Discrete specialised organs
Eg. Smell, taste, vision, hearing and balance
149
Describe the process of sensation
1. Stimulation of sensory receptor
2. Transduction of stimulus
3. Generation of nerve impulses
4. Integration of sensory input
150
What is the microscopic structure of sensory receptors?
1. Free nerve endings of first order sensory neurons
Eg pain, temperature, tickle, itch
2. Encapsulated nerve endings of first order sensory neurons
Eg pressure, vibration
3. Separate cells that synapse with first order neurons
Eg hair cells for hearing, gustatory receptors in taste buds, photoreceptors in retina of eye for vision
151
Where are exteroreceptors, interoceptors and propioceptors located?
Extero - located at or near external surface of body
Intero - located in blood vessels, visceral organs, muscles and nervous system
Proprio - located in muscles, tendons, joints and inner ear
152
Mechanoreceptors
Sensitive to mechanical stimuli eg deformation, stretching or bending of cells
153
Thermo receptors
Detect changes in temperature
154
Nocieptors
Respond to painful stimuli from physical or chemical damage to tissue
High density in skin, low density in bone, muscle, joints, blood vessels
155
Photoreceptors
Detect light that strikes the retina of the eye
156
Chemoreceptors
Detect chemicals in the mouth, nose and body fluids
157
Osmoreceptors
Detect the osmotic pressure of body fluids
158
Properties of a sensory stimulus
Modality
Location
Intensity
Duration
159
Phasic receptors
Rapidly adapt
Specialised for signalling changes in a stimulus
Eg pressure touch smell
160
Tonic receptors
Slowly adapting receptors
Continue to trigger nerve impulses as long as stimulus persists
Eg pain body composition chemical composition of blood
161
What is the receptive field ?
Region where presence of a stimulus will alter firing of that neuron
IMPORTANT for the discrimination of 2 stimuli
Smaller receptive fields at higher density enhance discrimination between 2 stimuli
162
Proprioceptive receptors
Provide info about body position and movements (kinaesthesia)
Embedded in muscles and tendons
Hair cells of inner ear
163
Gustation means taste. What are the 5 primary tastes?
Sweet - sugars and artifical sweetness
Sour - H+ released when acids dissolved in water
Salty - Na+ ions eg from sodium chloride
Bitter - eg caffeine, quinine, morphine
Umami - Japanese for delicious - amino acids particularly glutamate. MSG = mono sodium glutamate
164
Taste receptors are located in taste buds. What are the 3 types of epithelial cells found in taste buds?
Supporting cells
Gustatory receptor cells
Basal cells
165
Individual gustatory cells only respond to 1 type of tastant.
What are tastants?
Chemicals that stimulate gustatory receptor cells
Dissolve in saliva and make contact with gustatory microvilli
Taste transduction - depolarising receptor potential
Exocytosis of synaptic vesicles from gustatory receptor cell
166
How are salt receptor potentials generated?
Na+ ions enter gustatory receptor cells via Na+ channels
167
How are acid receptor potentials generated?
H+ ions enter gustatory receptor cells via H+ channels - depolarisation and release of NT
168
How are sweet, bitter and umami receptor potentials generated?
Bind to G protein coupled receptor
Activate enzymes and produce IP3 (inositol trisohosphate) leading to depolarisation
169
Olfaction (smell)
Olfactory receptors (1st order neurons) are located in the … of the nose
Transduction occurs at the …
Olfactory epithelium
Olfactory cilia
170
What are odorants?
Chemicals that bind to and stimulate receptors in the cilia
171
What is the lifespan of olfactory receptor cells?
2 months
172
Summary of Olfaction
Olfactory receptor cells are first order neurons
Receptor cells respond to one odorant
-400 functional types
Receptor potentials generated: G protein coupled receptors
173
What is the function of the cornea of the eye?
Physical protection
Refracting (focusing) incoming light - fine tuning is provided by the lens
174
What happens to pupil of the eye in bright light?
Constricts as the circular muscles of the Iris CONTRACT (parasympathetic)
175
What happens to the pupil of the eye in dim light?
Pupil dilates as the radial muscles of the Iris contract (sympathetic)
176
The lens of the eyeball
Formed of proteins called crystallins
Transparent, connective tissue
No blood vessels
Enclosed by a clear connective tissue capsule
Held in position by encircling zonular fibres
Focus images on retina to facilitate clear vision
177
What is myopia?
(Image formation)
Focus in front of retina
See close objects clearly but NOT distant objects
178
What is hyperopic?
(Image formation)
Focus behind retina
See distant objects clearly but NOT close objects
179
What is astigmatism?
(Image formation)
Irregular curvature of lens or cornea
Blurred vision!
180
What are rods?
Dim light (scotopic? Vision
Human retina has -120 million rods
181
What are cones?
Bright light (photopic) vision
Trichromatic colour vision
Human retina has -6 million cones
182
What is the fovea centralis?
Contains only cones
Area of highest visual acuity (resolution)
183
Photopigments
Each type of photoreceptor contains a specific photo pigment:
Rhodopsin (rods)
Red / green / blue cone pigments
Photopigment:
Opsin (glycoprotein)
Retinal (derivative of vitamin A)
184
Describe the process of phototransduction
1. Isomerisation - cis retinal absorbs photons of light. Isomerises to trans retinal
2. Bleaching - trans retinal dissociates from opsin protein. Change in opsin protein
3. Conversion - retinal isomerase converts trans to cis retinal
4. Regeneration - cis retinal binds to opsin protein
185
What happens in the dark - phototransduction?
Dark = depolarising receptor potential
Cis retinal associated with opsin
High cGMP (guanylyl Cyclase)
cGMP gated Na+ channels are open
Dark current - depolarises (-40mv)
Voltage gated Ca+ channels open
Exocytosis of synaptic vesicles
Glutamate release (inhibitory NT)
Hyperpolarises bipolar cells
No signals to ganglion cells
186
What happens in the light - phototransduction?
Light = hyper polarising receptor potential
Cis retinal isomerised to trans retinal
Activation of G protein - transducin
Transducin activates enzyme cGMP phosphodiesterase
Breakdown of cGMP
cGMP gated Na+ channels close
Decreased Na+ flow
Membrane potential reduces (-65mv)
Hyper polarising receptor potential
Voltage gated Ca+ channels close
Decreased NT release
Excited bipolar cells
Ganglion cells are stimulated - action potentials
187
Visual processing in the retina
Rods and cones are connected to 2nd order retinal neurons, bipolar cells
Bipolar cells in turn connect to 3rd order retinal neurons, ganglion cells
At both of these levels, photic info is processed and integrated
If this retinal processing did NOT take place, handling the info from the photoreceptor would exceed the capacity of the Brain!
188
Visual pathway
The axons of the ganglion cells leave each retina via the optic nerve
A partial crossing over of the optic nerves takes place at the optic chiasm so that info from both eyes can enter both hemispheres
Most optic nerve fibres project to the lateral geniculate nucleus
The lateral geniculate nucleus projects to the visual cortex, the centre of subjective vision
189
Non visual effects of light - neurophysiological
Increase core body temp
Increase heart rate
Pupillary light reflex
190
Non visual effects of light - neurobehavioural
Increase alertness
Increase performance
Increase mood
191
What does synchronising the circadian clock mean?
Resetting the effects of light!
192
The ear can detect changes in balance.
Receptor organs are the vestibular apparatus. What are they?
Utricle
Saccule
Semi circular ducts
193
The ear and balance: Hair Cells
Sensory receptors
Stereocilia of graduated height
One kinocilium (tallest)
Hair bundle = stereocilia and kinocilium
194
What are the columnar supporting cells of the ear?
Secrete otolithic membrane
Thick, gelatinous, glycoprotein layer
195
What are the otoliths of the ear?
Dense calcium carbonate crystals
196
What does the utricle respond to?
Linear acceleration or deceleration in horizontal direction
Eg when body is being moved in a car that is speeding up or slowing down
197
What does the saccule respond to?
Linear acceleration or deceleration in vertical direction
Eg when body is being moved up or down in an elevator
198
What happens when head tilts forward?
Otolithic membrane and otoliths are pulled by gravity
Slide over hair cells in direction of tilt
Bend hair bundles
199
What happens when head jerks forward?
Otolithic membrane lags behind head movement (inertia)
Bends in other direction - opens cation channels / depolarising receptor potentials
Bending in opposite direction closes the cation channels - hyperpolarisation
200
Hair cells depolarise and hyper-polarise which…
Release NT at a faster or slower rate
201
Ampulla =
Dilated portion of the duct
202
The vestibular apparatus is involved in…
Balance
203
Utricle
Linear acceleration or deceleration in horizontal direction
Head tilts forward or backward
204
Saccule
Linear acceleration or deceleration in vertical direction
205
Semi circular ducts
Rotational acceleration and deceleration
206
Protein digestion begins in the …
HCL denatures …
Pepsin begins …. Digestion
Stomach
Proteins
Enzymatic
207
Pancreatic juice is secreted into the …
Pro enzymes are …
Peptidases in …
Small intestine
Activated
Brush border
208
Amino acid and peptides are absorbed by three mechanisms of …
Active transport
209
Amino acids are processed by the …
Liver
210
Dietary fat consists mainly of …
Triaglycerol
211
Lipid digestion begins in the …(lingual lipase) and continues in the … (gastric lipase)
Mouth
Stomach
212
Majority of lipid digestion occurs in the … (pancreatic lipase)
Small intestine
213
Bile salts are … for emulsification and forming …
Critical
Micelles
214
Small fatty acids diffuse into … and the capillaries
Absorptive cells
215
Large fatty acids form into …and are released into the …
Chylomicrons
Lacteals
216
What are the different causes of GI tract disturbance?
Viral
Bacteria
Inflammation
Disrupted processes
Medications
Behaviours
217
Transport of molecules
Water - osmosis
Sodium - cotransporters, H+ exchangers, sodium specific channels
Potassium - diffusion
Carbohydrates - facilitated diffusion, cotransporters
Proteins - cotransporters, transcytosis
Lipids - diffusion
218
Name 2 substances that can be directly absorbed WITHOUT undergoing digestion
Water, vitamins, ions and cholesterol
219
Name 1 mechanism by which sodium is absorbed from the lumen
Co transporter (glucose / amino acids), hydrogen exchange, sodium channels
220
Where is potassium secreted?
Large intestine
221
Where is aldosterone secreted from
Adrenal cortex
222
Name a monosaccharide
Glucose
Fructose
Galactose
223
Where does salivary amylase act on carbohydrates?
Mouth and stomach until it is denatured by acidic environment
224
Where is maltase located?
Brush border of absorptive cells in small intestine
225
How is fructose absorbed?
Facilitated diffusion by GLUT5 and GLUT2
226
Which class of enzymes creates short peptide chains
Endopeptidases
227
What format is pepsin secreted in
Pepsinogen - activated to pepsin when in contact with HCL
228
What do pancreatic acinar cells secrete?
Trypsin inhibitor
229
What does aminopeptidase do?
Cleaves off an amino acid at the amine end of a peptide chain
230
How do larger peptide chains get absorbed
Transcytosis
231
What is a triglyceride formed of
Glycerol + 3 fatty acids
232
What pH does gastric lipase operate best at
pH 5-6
233
What 2 actions do bile salts have in the process of lipid digestion
Emulsification and micelles
234
How are short chain fatty acids absorbed
Simple diffusion
235
What issues can vomiting cause
Dehydration, alkalosis, damage to oesophagus and teeth
236
What causes jaundice
Build up of bilirubin
237
What is the treatment for Crohn’s disease?
Immunosuppressants
238
What is movement?
When living organisms moves a body part without a change in the position of the organism
239
What is locomotion?
When the movement of a part of the body leads to a change in the position and location of the organism
240
Movement and locomotion are both brought about by the joint efforts of… systems
Neuronal, skeletal, muscular
241
What is smooth muscle?
Lines the digestive tract and arteries, innervated by the autonomic nervous system
242
What is striated muscle?
Cardiac (heart muscle innervated by ANS) and skeletal muscle
Skeletal muscle makes the bulk of muscle in the body
Controls ALL aspects of movements: eyes, breathing, speech, move bones around joints
243
Motor neurons control muscle
They collect signals that initiate movement
Signals travel down axon
Neuronal signal crosses to the muscle at neuromuscular junction (chemical synapse)
Muscle contracts
244
What is the resting membrane potential?
When a neuron is inactive ions are asymmetrically distributed across the membrane
Outside: Na is high, K is low, Ca high, Cl - is high
Inside: Na is low, K is high, Ca is low, Cl- is low
245
Ionic concentrations are different because of the … inside the neuronal membrane
Active transport mechanisms
246
The action potentials
We can record neuronal signals by entering a neuron with a small glass pipette
We can simultaneously enter the cell with a stimulating electrode to mimic activation by injecting current
Injecting current into the cell evokes distinct electrical signatures = ACTION POTENTIALS
247
Each action potential is characterised by 5 phases:
Resting potential, rising phase (depolarisation), overshoot, falling phase (repolarisation), undershoot (after hyperpolarisation)
248
Action potential conduction
The process of rest, depolarisation, repolarisarion is dependant on the spatial arrangement of ion channels
Action potentials travel along the axon as 1 region is depolarised by excitation in the neighbouring segment
249
Action potential conduction confers a … from the neuronal cell body via the … to the synapse
Signal
Axon
250
The chemical synapse
Action potentials travel down the axon
Axon terminal forms a synapse onto another neuron (or muscle)
Electrical excitation causes release of synaptic vesicles
Neurotransmitter is released into synaptic cleft
Neurotransmitter bind to post synaptic receptors to trigger activation = action potential
251
Neurotransmitter - excitation actions:
Excitatory transmitter binds to post synaptic ligand gated ion channel
Ion channel mainly conducts Na
Na influx causes rapid depolarisation (excitatory)
= Excitatory post synaptic potential EPSP
252
Neurotransmitter - inhibition actions:
Inhibitory transmitter binds to post synaptic ligand gated ion channel
Ion channel mainly conducts chloride
Chloride influx causes rapid hyperpolarisation (inhibition)
= Inhibitory post synaptic potential IPSP
253
Neuromuscular junction and muscle contraction
NJ is the axon terminal of the motor neuron
Acetylcholine is the excitatory NT of the NJ
Binding of ACh to nicotinic ACh receptors causes depolarisation of the muscle and calcium release inside post synaptic muscle fibres
Muscle contracts
254
Muscle spindle
Sits inside muscle fibres
Covered in fibrous capsule
A stretch receptor
Innervated by la sensory neurons that feedback muscle tension
255
Alpha, la and gamma neurons work together
After alpha motor neuron activation, extra fusal muscle fibres TENSE
Intra fusal fibres elongate, which inhibits la sensory neurons
Gamma motor neurons fire = intra fusal neurons shorten to balance tension
256
What is reflex?
The simplest control of movement
257
A reflex is a simple perception cycle:
Perceive aversive stimuli
Activate motor neuron
Move away from stimulus
258
The brain is NOT involved in…
Reflexes
259
Example of monosynaptic stretch reflex:
(Knee jerk reflex)
Tap the tendon under the knees cap
Tendon stretches the quadriceps muscle of thigh
Muscle contracts
Leg extends
260
During stretch reflex:
Elongate 1 muscle and antagonist muscles must be relaxed (flexor vs extensor)
Reciprocal inhibition of antagonistic muscles by inhibitory inter neurons
261
The flexor withdrawal reflex:
Polysynaptic reflex
Speed of withdrawal depends on amount of pain
Direction of withdrawal depends on location of pain stimulus
Flexor reflex is slower than stretch reflex
Activated by Nocieptor neurons
Nocieptor activate multiple excitatory inter neurons (IN) in the spinal cord
IN activate nociceptor
Nociceptor activate flexor muscles
262
When flexor reflex is activated there is a need to … movement on the other side of the body
Reciprocal inhibition causes … movement in the other half of the body
Compensate
Opposite
263
One main function of the brain is to…
Direct the purposeful intervention with its environment
264
Adaptive neural circuitry allows mammals to..
Interact in sophisticated ways
265
Voluntary movements differ from reflexes, they are…
Initiated by a deliberate internal decision
266
Motor cortices control …
Voluntary movement
267
What are lateral pathways
Voluntary movement of limbs
Direct cortical control
268
What are ventromedial pathways
Control of posture and locomotion
Controlled by the brain stem
269
What are the lateral pathways?
Corticospinal tract and rubrospinal tract
270
Multiple sclerosis incurs demyelination of spinal cord axons
Demyelination of axons leads to impaired signalling
Demyelination is visible as lesions in fMRI imaging
Lesions cause slow worsening of motor impairments in patients as it mainly affects corticospinal tracts
271
What are the ventromedial pathways?
Vestibuli spinal, tectospinal, reticulospinal, pontine and medullary tracts
272
Primary motor cortex
Electrical stimulation (during brain surgery) will elicit movements
Detailed application of stimulation revealed a somatotopic map
Important movements have bigger representation: hand, face, lips
273
Cortical motor neurons encode directions of …
Movement
274
Movement is NOT encoded by single neurons but collectively by a large number of neurons =
Population coding
275
Premotor area PMA
Has somatotopic organisation like M1
Part of motor planning network
Specific functions determined in monkey experiments
276
Mirror neurons help to …
Plan movements and learning of complex motor programs
277
Supplementary motor area SMA
Somatotopic map
Connected to pre frontal cortex
Involved in motor planning of complex movements
278
PFC, SMA for … and … motor planning
Deliberate
Abstract
279
Parietal , somatosensory and PMA for integrating sensory info with …
Motor planning
280
M1 executes … by activating appropriate muscles
Motor plan
281
The brain sends axons directly to .. in the spinal cord
Motor neurons
282
Descending pathways are separated by originating areas into …
Lateral and ventromedial pathways
283
Corticospinal tract essential for …
Voluntary movement
284
Multiple areas in the frontal cortex contribute to …
Voluntary movement
285
Motor areas are organised into…
Somatotopic maps
286
Deep layer pyramidal cells send axons to the spinal cord (forming the corticospinal tract) and contribute to movement in …
Multiple directions
287
PMA neurons signal preparation for ..
Movement
288
Mirror neurons in the PMA help to understand motor actions and support … motor planning and learning
Complex
289
Subcortical control of movement - key brain areas are…
Thalamus, cerebellum, basal ganglia, brain stem
290
2 loops influence motor function via the thalamus…
Cerebellar loop and basal glanglia loop
291
Cerebellar loop contributes to…
Motor function by processing additional sensory info
292
Basal ganglia loop is crucial for …
Action selection / inhibition via direct and indirect pathways
293
Brain stem controls many fundamental motor activities like …
Breathing, cardiovascular function and posture
294
Lesions to the thalamus have been used to reduce tremor in patients for …
Thalamotomy
295
The cerebellum
A large structure near the bottom of the brain (cerebellum = little brain)
Damage to the cerebellum cause ATAXIA = patients show inaccurate and crude movements
Effect of alcohol on movement largely due to inhibition of cerebellar function
296
Basal ganglia function
Control and regulate complex movement patterns
Supports action selection and habitual movements
NO projections to the spinal cord
297
What diseases are due to affected basal ganglia?
Parkinson’s disease
Huntington’s chorea
Tics
Dystonia = muscles contract uncontrollably
298
Basal ganglia support motor function through 2 main pathways:
Direct and indirect pathways
299
Parkinson’s disease
A complex neurodegenerative disorder
Main pathology is neurodegeneration in the SNc
Cells that produce the NT dopamine die
Balance between direct and indirect pathway disturbed = tremor
300
Deep brain stimulation in the STN reduces … Parkinson’s disease
Tremor
301
Brain stem
Control of respiration
Smooth muscle
Gastrointestinal function
Stereotyped movements of the body
Reticular and vestibular nuclei control whole body movement and posture
302
Anencephaly is a rare developmental disorder where the newborn is missing…
All the brain structures ABOVE the brain stem
303
What is perception?
Conscious interpretation of sensations
304
What do visceral senses detect?
Conditions within internal organs
305
Name the 4 modalities of somatic sensation
Tactile, thermal, pain, proprioceptive
306
What do we mean by a transduction of a signal?
Conversion of the energy into a stimulus into a graded potential
307
Name the micro structures of a receptor cell
Free nerve endings of 1st order sensory neurons
Encapsulated nerve endings of 1st order sensory neurons
Separate cells that synapse with 1st order sensory neurons
308
How is the intensity of a stimulus encoded?
Frequency of action potentials
309
What are phasic receptors specialised for?
Rapidly adapt and specialised for signalling changes in a stimulus
310
What is the ligand for a sour gustatory receptor?
Hydrogen ions
311
What type of cell is a olfactory receptor cell?
Bipolar neuron
312
What type of cell is involved in olfactory transduction?
G protein coupled receptor
313
What is the iris of the eye concerned with?
Regulation of pupil size
314
What structures are important for focussing light?
Cornea, lens, zonular fibres and ciliary muscles
315
Name the cell types in the retina
Photoreceptors, horizontal cells, bipolar cells, amacrine cells, ganglion cells
316
What is the membrane potential of a rod in the dark?
Depolarised
317
Examples of a NON visual response to light
Pupil light reflex
Increased HR and temperature
Improved alertness and performance
Melatonin suppression
Resetting the clock
318
What does the amplitude of a sound wave describe?
How loud the sound is (decibels)
319
Name the structures of the middle ear
Malleus, incus and stapes
320
What are the key features of the hair cells in the inner ear that are involved in sound transduction?
Stereocilia with tip links and cation channels
321
What structures are involved in monitoring head tilt?
Utricle and saccule
322
What structures are involved in monitoring head rotation?
Semi circular ducts with ampulla
323
EEG allows to record changes in … due to electrical signalling in the …
Voltage
Brain
324
The brain shows … when recorded with EEG
Several rhythms
325
EEG rhythms are divided by their …
Frequency
326
Synchronisation and oscillations can be established through a … or feedback inhibition
Pacemaker
327
… manifests as episodes of hypersynchronous EEG activity
Epilepsy
328
Sleep is divided into different sleep …
Stages
329
Sleep stages are identified based on characteristic …and other physiological signatures
EEG
330
Spectral analysis allows … analysis of sleep EEG dynamics
Detailed
331
Neuromodulators control sleep through the change of …. Patterns
Neuronal firing
332
Sleep plays a crucial role in …
Memory consolidation
333
EEG amplitude depends on how … neuronal activation is
If synaptic inputs arrive at different times the sum of activity is … If arrive at the same time it is …
Synchronised
Small
Large
334
Brain rhythms exist in all …
Mammals
335
What are the 2 mechanisms of brain rhythms?
Central pacemaker (conductor)
Feedback inhibition (collective)
336
Epilepsy can be caused by mutations that cause an imbalance between excitation and inhibition, such as:
Mutant sodium channels with increased excitation
Mutant GABA channels with reduced inhibition
337
EEG is the routine diagnostic test for …
Epilepsy
338
What are the 3 main stages of sleep?
WAKE
Non REM
REM sleep
339
Spindle oscillations occur in EEG recordings during …
Sleep
340
Acetylcholine, serotonin and cortisol distinguish non REM from … sleep
REM
341
Emotions exist in … and …
Animals
Humans
342
Basic emotions can be described in …
Humans
343
Emotions evoke typical bodily …
Reactions
344
Subconscious emotions evoke … and brain …
ANS
Activation
345
Emotional processing is a distributed brain feature, key areas are:
Frontal cortex
Cingulate cortex
Amygdala
Hypothalamus
346
The amygdala is crucially involved in the processing of …
Eg during classical conditioning
Fear
347
The hypothalamus is a key brain area involved in the regulation of … behaviour
Aggressive
348
What are the 5 basic emotions?
Happiness
Sadness
Anger
Fear
Disgust
349
What is the Cannon Bard theory?
Emotional experience is generated by the brain first and may be independent of emotional expression
= physiological changes
350
What is the James Lang theory?
Emotional experience appears as a response to physiological changes in our body
351
What does the limbic system include?
Amygdala
Hippocampus
Cingulate gyrus
Pre frontal cortex
Thalamic nuclei
352
What was Antonio Damasio’s somatic marker hypothesis?
Somatic markers (SM) are signals from the body which are regulated in the emotion circuity of the brain - particularly pre frontal cortex
SM may influence info processing in may areas of brain - eg motor and sensory cortices
SM help to regulate decision making in situations of complexity and uncertainty
353
Sham rage only occurs if the posterior hypothalamus is left …
Intact
354
Affective aggression is due to the …
Medial hypothalamus
355
Predatory aggression is due to the …
Lateral hypothalamus
356
Mental health science links …mechanisms to pathological changes in behaviour
Genetic, molecular and brain
357
Developing novel treatments will rely on … approaches
Eg induced pluripotent stem cells
Molecular medicine
358
Anxiety disorders are characterised by constant and … anxiety and worry
Excessive
359
Anxiety can be due to activation of the …
HPA
360
Amygdala enhances / hippocampus reduces … activation
HPA
361
Psychotherapy and pharmacotherapy are used to treat …
Anxiety
362
Major depression occurs to about … of the general population
5-10%
363
Antidepressants include … and more recently …
SSRI
Ketamine
364
MD is a complex disorder caused by … factors
Genetic, developmental and environmental
365
Reduced serotonin signalling is a major cause of …
Depression
366
Most current antidepressants block re uptake of … at the synaptic cleft = increased serotonin
Serotonin
367
How does ketamine work?
Blocks NMDA receptors on inhibitory inter neurons
Activates other signalling pathways for protein translation and synaptogenesis
368
What are the 2 main types of muscle tissue in the body?
Striated and smooth
369
What is the name of the synapse between a motor neuron and a muscle?
Neuromuscular junction
370
What is the difference between EPSP and IPSP?
Excitation and inhibition
371
What is the post synaptic receptor of the neuromuscular junction?
Nicotinic acetylcholine receptor
372
Which neuron fires first during the stretch reflex?
La neuron
373
What are the main descending motor pathways in the spinal cord?
Lateral and ventromedial pathways
374
What is the function of the tectospinal tract?
Support eye movements
375
What is somatotopic representation?
The mapping of motor function to different parts of M1
376
What is a function of the premotor area?
Preparation for movement
377
When does a mirror neuron (MN) fire?
MN fire when observing movements in others
378
What brain structures form the 2 main sub cortical loops that support motor function?
Cerebellum + basal ganglia + thalamus
379
What is ataxia?
Impairments in movement
380
What are neurons that form a large part of cerebellum?
Purkinje cells
381
What is the net effect of the direct pathway on the motor cortex?
Excitation
382
What is the final effect of deep brain stimulation in PD patients?
Disinhibition of the thalamus
383
What is located in peyer’s patches of the ileum?
Gut associated lymphoid tissue GALT
384
During emulsification of large lipid globules, the … region of bile salts interacts with the lipid and the … region interacts with chyme
Hydrophobic
Hydrophilic
385
When blood pressure … this leads to … aldosterone secretion
Decreases
Increased
386
What is the mechanism by which dipeptides are absorbed in the small intestine?
Hydrogen co transporters
387
Enterokinase is a brush border enzyme .
If it was ABSENT which is the following processes would be inhibited?
The conversion of trypsinogen into trypsin
388
Increased pressure in which segment of the gastrointestinal tract results in ‘reverse’ peristalsis?
Rectum
389
The direction of a sound source is computed in the …
Cerebrum by comparing the signal from both ears
390
The … of a sound wave indicates the pitch and the … indicates the loudness
Frequency
Amplitude
391
An action potential is elicited in a sensory neuron during a reflex movement.
Order the events that occurs during
1. Na+ channels open leading to
2. Depolarisation
3. K+ channels open leading to
4. Repolarisation
5. Returns to resting state potential
392
Which brain areas are part of the Papez circuit?
Amygdala
Cingulate gyrus
Hippocampus
393
What are the basic emotions?
Disgust
Anger
Fear
Happiness
Sadness
394
Which brain area is involved in deliberate and abstract motor planning?
Supplemental motor area SMA
395
What neurons form a large part of cerebellum?
Purkinje cells
396
What is the function of the tectospinal tract?
Support body orientation based on visual information
397
What is the name of the 1st brain rhythm described?
Alpha
398
What are the 2 mechanisms for generating synchronised activity in neuronal networks?
Pacemaker and feedback inhibition
399
What is a cause of epilepsy?
Mutant sodium channels that cause increased excitation
400
What is a sleep stage?
N3
401
What is a characteristic oscillation linked to NREM 2 sleep?
Spindle
402
Which neuromodulator concentration is increased during REM sleep?
Acetylcholine
403
What parts of the nervous system are involved in processing emotions?
Amygdala and ANS
404
Which part of the amygdala integrates sensory and aversive stimulus info during fear conditioning?
Basolateral nuclei
405
Which part of the brain mediates sham rage?
Hypothalamus
406
Which neural pathways is crucially involved in anxiety disorder?
HPA
407
What is the effect of the amygdala on the HPA?
Excitatory
408
What is the mechanism of action of anti depressants?
Blocking re uptake of serotonin
409
What are pre cursors for induced pluripotent stem cells?
Somatic cells
410
What is the effect of Benzodiazepine on GABA receptors?
Increase chloride influx
411
EEG amplitude depends on … inputs to cortical neurons
Synchronous
412
A clinical disorder which results in the autoimmune destruction of GASTRIC PARIETAL CELLS would prevent the absorption of what nutrient?
Vitamin B12
413
What enzyme is located at the brush border of the small intestine and plays a role in carbohydrate digestion?
Lactase
414
What nutrient in the diet would NOT be soluble in water?
Triaglycerol
415
Correct order of layers in the gastrointestinal wall
Mucosa
Submucosa
Muscularis externa
Serosa
416
What is FALSE about the peristaltic contractions in the GI wall?
Their main function is mixing of food bolus with digestive enzymes
417
What is true about gastric acid secretion?
The secretion is initiated in the cephalic phase before food enters the stomach
418
What are the main descending motor pathways in the spinal cord?
Lateral and ventromedial pathways
419
What is NOT an accessory organ to the GI tract?
Ileum
420
Which of the following cell types is essential for the digestion of proteins?
Parietal cell - secretes hydrochloric acid and intrinsic factor - denatures protein and activates pepsinogen
421
During the pharyngeal stage of swallowing, the medulla oblongata sends a signal to trigger the movement of what structures?
Uvula
Soft palate
422
What is true about gastrin?
Strengthens the contraction of the lower oesophageal sphincter muscle
423
Presence of chyme in the duodenum stimulates what?
Sympathetic nervous system
424
What can cause an increase in pH of the GI tract?
Secretin
425
Examples of active transport?
Sodium glucose co transporters in small intestine
Transcytosis of small peptide chains
426
What enzymes are located at the brush border?
Lactase
Aminopeptidase
427
Decreased blood pressure leads to increased aldosterone levels which leads to … absorption of sodium and … vasodilation
Increased
Decreased
428
Gastrin does NOT directly influence what enzyme?
Trypsin
429
Thermo receptors are …
Phasic receptors
Constant prolonged stimulus
430
What special sense has a receptor that is 1st order neuron?
Olfactory
431
Put the retinal layers in order that light passes through them
Ganglion cell layer
Inner synaptic layer
Bipolar cell layer
Outer synaptic layer
Photoreceptor cell layer
432
What would NOT apply to a touch receptor in the skin?
It is a visceroceptor
433
What special sense does NOT involve a G protein coupled receptor?
Detection of a sour gustant
434
In a cone photoreceptor, what is the consequence of a depolarising membrane potential?
Increase in NT release
Hyperpolarisation of bipolar cells
