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YEAR 2 - Physiology > Gastrointestinal System + Neurophysiology > Flashcards

Gastrointestinal System + Neurophysiology Flashcards

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)

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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)

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3
Q

What are the 6 processes of the digestive system?

A

Ingestion
Secretion
Motility
Digestion
Absorption
Defecation

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4
Q

The mucosa layer of the GI Tract is a mucous membrane.
It is formed of 3 layers. What are they?

A
  1. 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
  2. Lamina Propria
    Connective tissue. Blood and lymphatic vessels for nutrient absorption. Mucosa associated lymphatic tissue MALT
  3. Muscularis mucosae
    Smooth muscle fibres. Creates folds in the mucous membrane
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5
Q

What are the layers 2-4 of the GI Tract?

A

Submucosa

Muscularis

Serosa

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6
Q

What are the accessory organs of the GI tract?

A

Teeth
Tongue
Salivary glands
Liver
Gall bladder
Pancreas

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7
Q

Digestive system is composed of the … and …

A

GI tract
Accessory organs

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8
Q

What does the GI tract include?

A

Mouth, pharynx, oesophagus, stomach, small intestine, large intestine and anus

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9
Q

What 4 layers is the GI tract composed of?

A

Mucosa
Submucosa
Muscularis
Serosa

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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)

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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

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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

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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.

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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)

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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

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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)

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17
Q

What do Brunner’s glands in the duodenum do?

A

Secrete alkaline mucus

Neutralises gastric acid in the chyme

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18
Q

Where does most of the digestion and absorption take place?

A

Small intestine

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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

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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

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21
Q

What are the 4 major regions of the large intestine?

A

Cecum, colon, rectum and anal canal

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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

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23
Q

What cells make up the large intestine?

A

Absorptive cell - absorbs water

Goblet cell - secretes mucus

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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

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25
Q

The pharynx is a funnel shape tube with skeletal muscle lined by a mucous membrane.
What does it consist of?

A

3 parts
Nasopharynx - respiratory function
Oropharynx + Laryngopharynx - respiratory and digestive function

Swallowed food goes from mouth to Oro and Laryngo

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26
Q

What is deglutition (swallowing)?

A

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

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27
Q

What is the central nervous system CNS?

A

Brain and spinal cord

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28
Q

What is the peripheral nervous system PNS?

A

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

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29
Q

What is the autonomic nervous system?

A

Sympathetic ‘fight or flight’

Parasympathetic ‘feed and breed’ or ‘rest and digest’

Enteric nervous system - GI tract

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30
Q

What does the myenteric plexus regulate?

A

GI tract motility

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31
Q

What does the submucosal plexus regulate?

A

Regulates GI secretion

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32
Q

What do parasympathetic fibres of GI tract do?

A

Increase GI tract secretion and motility

Increase activity of ENS neurons

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33
Q

What do sympathetic fibres of GI tract do?

A

Decrease GI tract secretion and motility

Inhibit ENS neurons

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34
Q

Neural regulation is a gastric phase of digestion where food enters the stomach.
What else happens?

A

Stretch receptors stimulated by gastric distension

Chemoreceptors activated if pH increases with protein

Nerve impulses to the submucosal plexus (secretions)

Negative feedback loop

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35
Q

What are the stages of gastric phase of digestion?

A
  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
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36
Q

Gastrin is released from the G cells of the gastric glands in response to:

A

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

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37
Q

Gastrin is released into bloodstream and stimulates gastric glands which:

A

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

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38
Q

Gastrin secretion is inhibited when… and is stimulated when…

It ensures optimal low pH for…

A

pH of gastric juice drops below 2.0
pH rises

Functioning of pepsin, killing of microbes, denaturing of proteins in the stomach

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39
Q

Smooth muscle contractions are initiated at the Interstitial cells of Cajal (pacemaker).
What do they generate?

A

Spontaneous electrical slow waves

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40
Q

Slow waves differ between regions. What do slow waves generate?

A

Phasic contractions - Peristalsis

Peristaltic wave moves gastric contents from body to antrum (propulsion)

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41
Q

What is absorption?

What substances can be absorbed without undergoing digestion?

A

Movements of products via digestion from lumen of GI tract into blood or lymph

Water, vitamins, ions, cholesterol

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42
Q

The small intestine has less … so more …

A

Tight junctions
Paracellular movement

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43
Q

What is passive transport of molecules?

A

No energy required
Moving down the concentration gradient
Diffusion - simple / facilitated
Transmembrane proteins

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44
Q

What is active transport of molecules?

A

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

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45
Q

What is the importance of sodium and potassium?

A

Two primary electrolytes

Important for maintaining fluid balance in the body

Blood pressure

Nerve and muscle function

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46
Q

What are the 3 mechanisms of sodium absorption from the lumen?

A

Co transport with nutrients (1 glucose: 2 Na+)

In exchange for H+

Specific sodium channels

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47
Q

What happens during sodium transport?

A

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)

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48
Q

What happens during potassium transport?

A

Small intestine absorbs potassium

Large intestine secretes potassium

Potassium balance regulated by aldosterone

Loss of potassium in faeces

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49
Q

What is aldosterone?

A

Mineralcorticoid

Secreted by adrenal cortex

Regulates homeostasis of Na+ and K+

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50
Q

Water is bi directional, moves due to osmosis, diffusion and through aquaporins.
What is the paracellular and trans cellular route?

A

Paracellular - between cells. Through tight junctions. SLOW

Transcellular - through cells. Water channels. Aquaporins increase trans cellular flux. FAST

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51
Q

Summary of Sodium:

A

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

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52
Q

Summary of potassium:

A

Small intestine absorbs potassium

Large intestine secretes potassium

Potassium balance regulated by aldosterone

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53
Q

Summary of water:

A

Diffuses in response to osmotic gradient established by sodium

Most movement is trans cellular through aquaporins

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54
Q

What are the dietary carbohydrates?

A

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

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55
Q

Starch is a polysaccharide of glucose monomers joined by glycosidic bonds.
What are amylose and amylopectin?

A

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

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56
Q

What is the carbohydrate digestion pathway?

A

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

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57
Q

What bonds is a dextrin linked by?

A

D glucose units linked by a (1-4) or a (1-6) glycosidic bonds

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58
Q

What is the purpose of the liver in the carbohydrate digestion pathway?

A

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

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59
Q

What is the purpose of the small intestine in the carbohydrate digestion pathway?

A

Intestinal juice

Absorptive cells synthesise several digestive enzymes:
Brush border enzymes, plasma membrane of microvilli, a dextrinase, maltase, sucrase, lactase

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60
Q

Absorption of monosaccharides:

120g/h of monosaccharides absorbed in the …
All dietary carbohydrates absorbed except … and …

A

Small intestine
Cellulose
Fibre

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61
Q

How is fructose absorbed?

How are glucose and galactose absorbed?

A

Facilitated diffusion

Secondary active transport

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62
Q

What is the purpose of the large intestine in the carbohydrate digestion pathway?

A

Bacteria - ferment any remaining carbohydrates. Hydrogen, carbon dioxide and methane gas

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63
Q

Mumps is inflammation and enlargement of the parotid glands.
What is cause, symptoms and treatment?

A

Cause: mumps virus (paramyxovirus)

Symptoms: moderate fever, extreme pain in the throat, swelling on side of face

Treatment: vaccine

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64
Q

Gastro oesophageal reflux disease GORD is where the stomach contents reflux into oesophagus.

What is cause, symptoms and treatment?

A

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

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65
Q

What is the mechanism of vomiting?

A

Nerve impulses to medulla oblongata
Returning impulses result in squeezing the stomach between diaphragm and abdominal muscles
Contents expelled through open oesophageal sphincters

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66
Q

Prolonged vomiting can be serious. Why?

A

Loss of gastric acid juice = alkalosis (higher than normal blood pH). Dehydration. Damage to the oesophagus and teeth

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67
Q

Pancreatitis is inflammation of the pancreas.

What is cause, symptoms and treatment?

A

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

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68
Q

Hepatitis is inflammation of the liver.

What is cause, symptoms and treatment?

A

There is Hepatitis A, B, C, D, E

Causes: viruses, drugs, chemicals, alcohol

Treatment: Vaccines

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69
Q

Peptic ulcers are are lesion in the GI tract membrane.

What is cause, symptoms and treatment?

A

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)

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70
Q

Crohn’s disease is inflammation of the GI tract. A chronic condition.

What is cause, symptoms and treatment?

A

Symptoms: diarrhoea, stomach aches and cramps, blood in stool, fatigue, weight loss

Causes: autoimmune, smoking, genetics

Treatment: immunosuppressants eg steroids. Surgical procedures

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71
Q

Diarrhoea is increase in frequency, volume and fluid content of faeces

What is cause, symptoms and treatment?

A

Outcome: dehydration, electrolyte imbalances

Causes: lactose intolerance, stress, microbes irritating gastrointestinal mucosa

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72
Q

Constipation is infrequent or difficult defection.

What is cause, symptoms and treatment?

A

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

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73
Q

Why do we have biological clocks?

A

Anticipate and prepare for predictable environmental changes

Optically synchronised with the environment

Adapt to changing environments

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74
Q

What does circadian mean?

A

Circadian: drive 24hr rhythms in physiology and behaviour

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75
Q

What are rhythms in physiology?

A

Lung function
Cardiovascular
Muscle function
Metabolism

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76
Q

Sleep deprivation can be…

A

Acute - single night of sleep loss

Chronic - persistently short sleep episodes

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77
Q

Health risks in shift work? (Night shifts etc)

A

Obesity and weight gain
Type 2 diabetes
Coronary heart disease
Breast, prostate and colorectal cancer
Occupational accidents

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78
Q

Sleep restriction affects metabolism by:

A

Impairs glucose tolerance
Reduced acute insulin response
Risk factor: diabetes, obesity, hypertension

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79
Q

The appetite hormones:
What is ghrelin?

Leptin?

A

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.

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80
Q

How does sleep restriction affect appetite?

A

Sleep restriction for 2 days: increases ghrelin, decreases leptin

Increased food intake

Decreased energy expenditure

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81
Q

Proteins are polymers of amino acids linked via peptide bonds.
Describe primary, secondary, Tertiary, quaternary structure.

A

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

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82
Q

What are the proteolytic enzymes, exopeptidase and endopeptidases?

A

Exopeptidase enzymes - carboxy or amino peptidases. Liberate free amino acids

Endopeptidases - liberate smaller peptide chains

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83
Q

The digestion of proteins involves the mechanical disruption by chewing and gastric motility. What else does it involve?

A

Protein denaturation by HCL

Combined effect of chemical and enzymatic digestion

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84
Q

Stomach is where enzymatic digestion of proteins begins. What is the role of pepsin there?

A

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

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85
Q

What prevents pepsin from digesting the protein in stomach cells?

A
  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
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86
Q

The small intestine contains pancreatic juice in an inactive form to protect the pancreas.
How?

A

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

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87
Q

How are proteins digested in the small intestine?

A

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

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88
Q

How is protein digestion completed by 2 peptidases in the brush border?

A

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

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89
Q

Most proteins are absorbed as amino acids via active transport process in duodenum and jejunum.
Where are these absorbed AA found?

A

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

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90
Q

How are proteins absorbed?

A

Na+ dependant amino acid transport

H+ co transport with small peptides

Larger peptides moved by transcytosis

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91
Q

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

A

Liver
Deaminate
Urea
Synthesise

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92
Q

How is the mouth involved in lipid digestion?

A

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)

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93
Q

How is the stomach involved in lipid digestion?

A

Chief cells

Gastric lipase - operates best at pH 5-6

Splits triglycerides into fatty acids and monoglycerides.
Monoglyceride = glycerol molecule + one fatty acid molecule

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94
Q

How is the small intestine involved in lipid digestion?

A

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

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95
Q

Pancreatic lipase is made up of 3 different enzymes what are they?

A

Triglycerol hydrolase

Cholesterol ester hydrolase

Phospholipase A2

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96
Q

What is the action of pancreatic lipase?

(Triaglycerol hydrolase)

A

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

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97
Q

Bile salts are sodium and potassium salts of bile acids.
They are amphipathic what does this mean?

What does emulsification mean?

A

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)

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98
Q

Emulsification is crucial for … the surface area for … action

A

Increasing

Lipase

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99
Q

What are micelles and what do they do?

A

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

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100
Q

Summary of lipid digestion:

Emulsification by…
Formation of mixed …
Micelle breaks down close to … low pH of acid microclimate zone
Fatty acids are …

A

Bile salts
Micelles
Luminal surface
Released

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101
Q

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.

A

Simple diffusion
95%
Simple diffusion

Brush border
Absorptive cells
Chyme

Ferrying
Hydrophobic

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102
Q

What happens inside absorptive cells - lipid absorption?

A

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!

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103
Q

What does the hydrophilic protein coat do in lipid absorption?

A

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

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104
Q

What does lipoprotein lipase do?

A

Breaks down triglycerides in chylomicrons and other lipoproteins into fatty acids and glycerol

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105
Q

What is enterohepatic circulation?

What happens when there’s insufficient bile salts?

A

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

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106
Q

What happens during lipid metabolism in the liver?

A

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

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107
Q

What is the importance of healthy fats in the diet?

A

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

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108
Q

Amino acids are processed by the …

A

Liver

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109
Q

Dietary fat consists mainly of …

A

Triaglycerol

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110
Q

Majority of lipid digestion involves:

A

Pancreatic enzymes
Bile

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111
Q

Bile salts are critical for forming …

A

Micelles

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112
Q

Absorbed lipids form into … within the enterocyte are are released into the lacteals

A

Chylomicrons

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113
Q

What is cholecystokinin CCK and what is it released in response to?

A

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)!

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114
Q

What does cholecystokinin CCK simulate?

A

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

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115
Q

Secretin is released from S cells of intestinal glands in small intestine.
What is it released in response to?

A

Acidic chyme entering the duodenum

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116
Q

What does secretin do?

A

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

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117
Q

What are segmentations?

(Small intestinal motility)

A

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

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118
Q

Peristaltic contractions are responsible for … in small intestine.

A

Forward movement

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119
Q

What are the phases of the migrating motor complex?

A

Phase 1: quiescence

Phase 2: intermittent and irregular activity

Phase 3: short period of intense activity

Phase 4: quiescence

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120
Q

What are the general principles of GI tract motility?

A

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

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121
Q

What are the 3 phases of secretion in the GI tract?

A

Cephalic Phase: pre ingestion and food in mouth

Gastric phase: food in stomach

Intestinal phase: food in small intestine

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122
Q

What is the cephalic phase?

A

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’

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123
Q

What secretions are stimulated during cephalic phase?

FEED FORWARD MECHANISM

A

Salvia production

Gastric acid

Gallbladder contraction - releasing bile into SI

Exocrine pancreatic secretions - releasing HCO3 and enzymes into SI

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124
Q

What happens during the gastric phase?

Food now in the stomach

A

Secretion of HCL

Pepsinogen (protease enzyme)

Intrinsic factor - to allow ileal abosrption of vitamin B13

Production of the mucus bicarbonate layer

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125
Q

What is the purpose of HCO3 - and prostaglandins in the gastric phase?

A

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

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126
Q

What is the intestinal phase?

A

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)

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127
Q

What does pancreatic exocrine secretion contain?

A

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

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128
Q

What are primary bile salts?

What is bile fluid?

A

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

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129
Q

What is enterohepatic circulation?

A

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

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130
Q

Secondary bile salts are formed by bacteria by dehydroxylation of primary bile salts.
Examples?

A

Deoxycholate from cholic acid

Lithocholate from chenodeoxycholic acid - poorly absorbed, TOXIC

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131
Q

3 reasons why the body needs nutrients

A

Energy

Building

Repair

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132
Q

Name 3 accessory organs to the GI tract

A

Salivary glands

Tongue

Teeth

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133
Q

Two functions of the stomach

A

Produce chyme, act as a reservoir, produce gastric juice, secrete gastrin

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134
Q

Four components of gastric juice

A

HCL
Pepsin
Gastric lipase
Intrinsic factor

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135
Q

What structures in small intestine increase surface area

A

Circular folds
Villi
Microvilli

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136
Q

What is function of segmentations

A

Mix chyme with digestive juices
Bring chyme into contact with mucosa for absorption

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137
Q

What is located in Peyer’s patches?

A

Gut associated lymphoid tissue

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138
Q

What are the 3 stages of swallowing?

A

Voluntary
Pharyngeal
Oesophageal

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139
Q

What does the myenteric plexus layer of the enteric nervous system control?

A

GI tract motility

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140
Q

What receptors are activated when food enters the stomach?

What are the 2 outcomes of this activation?

A

Stretch and chemoreceptors

Increased secretion of HCL and stomach wall contractions

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141
Q

What impact does gastrin have on sphincter muscles?

A

Lower oesophageal contraction strengthens, pyloric relaxes

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142
Q

Where are the spontaneous slow waves initiated in the stomach?

A

Interstitial cells of Cajal

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143
Q

What are the 2 actions of CCK?

A

Indicate satiety

Slows gastric emptying

Secretion of pancreatic juice

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144
Q

What is the function of the mucosal layer in the stomach?

A

Protect against damage - from HCL and pepsin

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145
Q

What does sensation mean?

A

The conscious or subs conscious awareness of changes in the external or internal environment

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146
Q

What does perception mean?

A

Conscious interpretation of sensations
Primarily a function of the cerebral cortex

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147
Q

What are the general senses?

A

Somatic - tactile (touch, pressure) , thermal, pain and proprioceptive sensations

Visceral - conditions within internal organs eg stretch, chemicals, nausea, hunger

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148
Q

What are the special senses?

A

Discrete specialised organs

Eg. Smell, taste, vision, hearing and balance

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149
Q

Describe the process of sensation

A
  1. Stimulation of sensory receptor
  2. Transduction of stimulus
  3. Generation of nerve impulses
  4. Integration of sensory input
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150
Q

What is the microscopic structure of sensory receptors?

A
  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
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151
Q

Where are exteroreceptors, interoceptors and propioceptors located?

A

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

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152
Q

Mechanoreceptors

A

Sensitive to mechanical stimuli eg deformation, stretching or bending of cells

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153
Q

Thermo receptors

A

Detect changes in temperature

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154
Q

Nocieptors

A

Respond to painful stimuli from physical or chemical damage to tissue

High density in skin, low density in bone, muscle, joints, blood vessels

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155
Q

Photoreceptors

A

Detect light that strikes the retina of the eye

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156
Q

Chemoreceptors

A

Detect chemicals in the mouth, nose and body fluids

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157
Q

Osmoreceptors

A

Detect the osmotic pressure of body fluids

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158
Q

Properties of a sensory stimulus

A

Modality
Location
Intensity
Duration

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159
Q

Phasic receptors

A

Rapidly adapt
Specialised for signalling changes in a stimulus
Eg pressure touch smell

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160
Q

Tonic receptors

A

Slowly adapting receptors
Continue to trigger nerve impulses as long as stimulus persists
Eg pain body composition chemical composition of blood

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161
Q

What is the receptive field ?

A

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

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162
Q

Proprioceptive receptors

A

Provide info about body position and movements (kinaesthesia)

Embedded in muscles and tendons
Hair cells of inner ear

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163
Q

Gustation means taste. What are the 5 primary tastes?

A

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

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164
Q

Taste receptors are located in taste buds. What are the 3 types of epithelial cells found in taste buds?

A

Supporting cells
Gustatory receptor cells
Basal cells

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165
Q

Individual gustatory cells only respond to 1 type of tastant.
What are tastants?

A

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

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166
Q

How are salt receptor potentials generated?

A

Na+ ions enter gustatory receptor cells via Na+ channels

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167
Q

How are acid receptor potentials generated?

A

H+ ions enter gustatory receptor cells via H+ channels - depolarisation and release of NT

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168
Q

How are sweet, bitter and umami receptor potentials generated?

A

Bind to G protein coupled receptor

Activate enzymes and produce IP3 (inositol trisohosphate) leading to depolarisation

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169
Q

Olfaction (smell)

Olfactory receptors (1st order neurons) are located in the … of the nose
Transduction occurs at the …

A

Olfactory epithelium
Olfactory cilia

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170
Q

What are odorants?

A

Chemicals that bind to and stimulate receptors in the cilia

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171
Q

What is the lifespan of olfactory receptor cells?

A

2 months

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172
Q

Summary of Olfaction

A

Olfactory receptor cells are first order neurons

Receptor cells respond to one odorant

-400 functional types

Receptor potentials generated: G protein coupled receptors

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173
Q

What is the function of the cornea of the eye?

A

Physical protection

Refracting (focusing) incoming light - fine tuning is provided by the lens

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174
Q

What happens to pupil of the eye in bright light?

A

Constricts as the circular muscles of the Iris CONTRACT (parasympathetic)

175
Q

What happens to the pupil of the eye in dim light?

A

Pupil dilates as the radial muscles of the Iris contract (sympathetic)

176
Q

The lens of the eyeball

A

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
Q

What is myopia?

(Image formation)

A

Focus in front of retina
See close objects clearly but NOT distant objects

178
Q

What is hyperopic?

(Image formation)

A

Focus behind retina
See distant objects clearly but NOT close objects

179
Q

What is astigmatism?

(Image formation)

A

Irregular curvature of lens or cornea
Blurred vision!

180
Q

What are rods?

A

Dim light (scotopic? Vision

Human retina has -120 million rods

181
Q

What are cones?

A

Bright light (photopic) vision
Trichromatic colour vision
Human retina has -6 million cones

182
Q

What is the fovea centralis?

A

Contains only cones
Area of highest visual acuity (resolution)

183
Q

Photopigments

A

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
Q

Describe the process of phototransduction

A
  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
Q

What happens in the dark - phototransduction?

Dark = depolarising receptor potential

A

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
Q

What happens in the light - phototransduction?

Light = hyper polarising receptor potential

A

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
Q

Visual processing in the retina

A

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
Q

Visual pathway

A

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
Q

Non visual effects of light - neurophysiological

A

Increase core body temp
Increase heart rate
Pupillary light reflex

190
Q

Non visual effects of light - neurobehavioural

A

Increase alertness
Increase performance
Increase mood

191
Q

What does synchronising the circadian clock mean?

A

Resetting the effects of light!

192
Q

The ear can detect changes in balance.

Receptor organs are the vestibular apparatus. What are they?

A

Utricle

Saccule

Semi circular ducts

193
Q

The ear and balance: Hair Cells

A

Sensory receptors
Stereocilia of graduated height
One kinocilium (tallest)
Hair bundle = stereocilia and kinocilium

194
Q

What are the columnar supporting cells of the ear?

A

Secrete otolithic membrane
Thick, gelatinous, glycoprotein layer

195
Q

What are the otoliths of the ear?

A

Dense calcium carbonate crystals

196
Q

What does the utricle respond to?

A

Linear acceleration or deceleration in horizontal direction
Eg when body is being moved in a car that is speeding up or slowing down

197
Q

What does the saccule respond to?

A

Linear acceleration or deceleration in vertical direction
Eg when body is being moved up or down in an elevator

198
Q

What happens when head tilts forward?

A

Otolithic membrane and otoliths are pulled by gravity
Slide over hair cells in direction of tilt
Bend hair bundles

199
Q

What happens when head jerks forward?

A

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
Q

Hair cells depolarise and hyper-polarise which…

A

Release NT at a faster or slower rate

201
Q

Ampulla =

A

Dilated portion of the duct

202
Q

The vestibular apparatus is involved in…

A

Balance

203
Q

Utricle

A

Linear acceleration or deceleration in horizontal direction
Head tilts forward or backward

204
Q

Saccule

A

Linear acceleration or deceleration in vertical direction

205
Q

Semi circular ducts

A

Rotational acceleration and deceleration

206
Q

Protein digestion begins in the …
HCL denatures …
Pepsin begins …. Digestion

A

Stomach
Proteins
Enzymatic

207
Q

Pancreatic juice is secreted into the …
Pro enzymes are …
Peptidases in …

A

Small intestine
Activated
Brush border

208
Q

Amino acid and peptides are absorbed by three mechanisms of …

A

Active transport

209
Q

Amino acids are processed by the …

A

Liver

210
Q

Dietary fat consists mainly of …

A

Triaglycerol

211
Q

Lipid digestion begins in the …(lingual lipase) and continues in the … (gastric lipase)

A

Mouth
Stomach

212
Q

Majority of lipid digestion occurs in the … (pancreatic lipase)

A

Small intestine

213
Q

Bile salts are … for emulsification and forming …

A

Critical
Micelles

214
Q

Small fatty acids diffuse into … and the capillaries

A

Absorptive cells

215
Q

Large fatty acids form into …and are released into the …

A

Chylomicrons
Lacteals

216
Q

What are the different causes of GI tract disturbance?

A

Viral
Bacteria
Inflammation
Disrupted processes
Medications
Behaviours

217
Q

Transport of molecules

A

Water - osmosis

Sodium - cotransporters, H+ exchangers, sodium specific channels

Potassium - diffusion

Carbohydrates - facilitated diffusion, cotransporters

Proteins - cotransporters, transcytosis

Lipids - diffusion

218
Q

Name 2 substances that can be directly absorbed WITHOUT undergoing digestion

A

Water, vitamins, ions and cholesterol

219
Q

Name 1 mechanism by which sodium is absorbed from the lumen

A

Co transporter (glucose / amino acids), hydrogen exchange, sodium channels

220
Q

Where is potassium secreted?

A

Large intestine

221
Q

Where is aldosterone secreted from

A

Adrenal cortex

222
Q

Name a monosaccharide

A

Glucose
Fructose
Galactose

223
Q

Where does salivary amylase act on carbohydrates?

A

Mouth and stomach until it is denatured by acidic environment

224
Q

Where is maltase located?

A

Brush border of absorptive cells in small intestine

225
Q

How is fructose absorbed?

A

Facilitated diffusion by GLUT5 and GLUT2

226
Q

Which class of enzymes creates short peptide chains

A

Endopeptidases

227
Q

What format is pepsin secreted in

A

Pepsinogen - activated to pepsin when in contact with HCL

228
Q

What do pancreatic acinar cells secrete?

A

Trypsin inhibitor

229
Q

What does aminopeptidase do?

A

Cleaves off an amino acid at the amine end of a peptide chain

230
Q

How do larger peptide chains get absorbed

A

Transcytosis

231
Q

What is a triglyceride formed of

A

Glycerol + 3 fatty acids

232
Q

What pH does gastric lipase operate best at

A

pH 5-6

233
Q

What 2 actions do bile salts have in the process of lipid digestion

A

Emulsification and micelles

234
Q

How are short chain fatty acids absorbed

A

Simple diffusion

235
Q

What issues can vomiting cause

A

Dehydration, alkalosis, damage to oesophagus and teeth

236
Q

What causes jaundice

A

Build up of bilirubin

237
Q

What is the treatment for Crohn’s disease?

A

Immunosuppressants

238
Q

What is movement?

A

When living organisms moves a body part without a change in the position of the organism

239
Q

What is locomotion?

A

When the movement of a part of the body leads to a change in the position and location of the organism

240
Q

Movement and locomotion are both brought about by the joint efforts of… systems

A

Neuronal, skeletal, muscular

241
Q

What is smooth muscle?

A

Lines the digestive tract and arteries, innervated by the autonomic nervous system

242
Q

What is striated muscle?

A

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
Q

Motor neurons control muscle

A

They collect signals that initiate movement
Signals travel down axon
Neuronal signal crosses to the muscle at neuromuscular junction (chemical synapse)
Muscle contracts

244
Q

What is the resting membrane potential?

A

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
Q

Ionic concentrations are different because of the … inside the neuronal membrane

A

Active transport mechanisms

246
Q

The action potentials

A

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
Q

Each action potential is characterised by 5 phases:

A

Resting potential, rising phase (depolarisation), overshoot, falling phase (repolarisation), undershoot (after hyperpolarisation)

248
Q

Action potential conduction

A

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
Q

Action potential conduction confers a … from the neuronal cell body via the … to the synapse

A

Signal
Axon

250
Q

The chemical synapse

A

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
Q

Neurotransmitter - excitation actions:

A

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
Q

Neurotransmitter - inhibition actions:

A

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
Q

Neuromuscular junction and muscle contraction

A

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
Q

Muscle spindle

A

Sits inside muscle fibres

Covered in fibrous capsule

A stretch receptor

Innervated by la sensory neurons that feedback muscle tension

255
Q

Alpha, la and gamma neurons work together

A

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
Q

What is reflex?

A

The simplest control of movement

257
Q

A reflex is a simple perception cycle:

A

Perceive aversive stimuli
Activate motor neuron
Move away from stimulus

258
Q

The brain is NOT involved in…

A

Reflexes

259
Q

Example of monosynaptic stretch reflex:

(Knee jerk reflex)

A

Tap the tendon under the knees cap

Tendon stretches the quadriceps muscle of thigh

Muscle contracts

Leg extends

260
Q

During stretch reflex:

A

Elongate 1 muscle and antagonist muscles must be relaxed (flexor vs extensor)

Reciprocal inhibition of antagonistic muscles by inhibitory inter neurons

261
Q

The flexor withdrawal reflex:

A

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
Q

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

A

Compensate

Opposite

263
Q

One main function of the brain is to…

A

Direct the purposeful intervention with its environment

264
Q

Adaptive neural circuitry allows mammals to..

A

Interact in sophisticated ways

265
Q

Voluntary movements differ from reflexes, they are…

A

Initiated by a deliberate internal decision

266
Q

Motor cortices control …

A

Voluntary movement

267
Q

What are lateral pathways

A

Voluntary movement of limbs
Direct cortical control

268
Q

What are ventromedial pathways

A

Control of posture and locomotion

Controlled by the brain stem

269
Q

What are the lateral pathways?

A

Corticospinal tract and rubrospinal tract

270
Q

Multiple sclerosis incurs demyelination of spinal cord axons

A

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
Q

What are the ventromedial pathways?

A

Vestibuli spinal, tectospinal, reticulospinal, pontine and medullary tracts

272
Q

Primary motor cortex

A

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
Q

Cortical motor neurons encode directions of …

A

Movement

274
Q

Movement is NOT encoded by single neurons but collectively by a large number of neurons =

A

Population coding

275
Q

Premotor area PMA

A

Has somatotopic organisation like M1

Part of motor planning network

Specific functions determined in monkey experiments

276
Q

Mirror neurons help to …

A

Plan movements and learning of complex motor programs

277
Q

Supplementary motor area SMA

A

Somatotopic map

Connected to pre frontal cortex

Involved in motor planning of complex movements

278
Q

PFC, SMA for … and … motor planning

A

Deliberate
Abstract

279
Q

Parietal , somatosensory and PMA for integrating sensory info with …

A

Motor planning

280
Q

M1 executes … by activating appropriate muscles

A

Motor plan

281
Q

The brain sends axons directly to .. in the spinal cord

A

Motor neurons

282
Q

Descending pathways are separated by originating areas into …

A

Lateral and ventromedial pathways

283
Q

Corticospinal tract essential for …

A

Voluntary movement

284
Q

Multiple areas in the frontal cortex contribute to …

A

Voluntary movement

285
Q

Motor areas are organised into…

A

Somatotopic maps

286
Q

Deep layer pyramidal cells send axons to the spinal cord (forming the corticospinal tract) and contribute to movement in …

A

Multiple directions

287
Q

PMA neurons signal preparation for ..

A

Movement

288
Q

Mirror neurons in the PMA help to understand motor actions and support … motor planning and learning

A

Complex

289
Q

Subcortical control of movement - key brain areas are…

A

Thalamus, cerebellum, basal ganglia, brain stem

290
Q

2 loops influence motor function via the thalamus…

A

Cerebellar loop and basal glanglia loop

291
Q

Cerebellar loop contributes to…

A

Motor function by processing additional sensory info

292
Q

Basal ganglia loop is crucial for …

A

Action selection / inhibition via direct and indirect pathways

293
Q

Brain stem controls many fundamental motor activities like …

A

Breathing, cardiovascular function and posture

294
Q

Lesions to the thalamus have been used to reduce tremor in patients for …

A

Thalamotomy

295
Q

The cerebellum

A

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
Q

Basal ganglia function

A

Control and regulate complex movement patterns

Supports action selection and habitual movements

NO projections to the spinal cord

297
Q

What diseases are due to affected basal ganglia?

A

Parkinson’s disease
Huntington’s chorea
Tics
Dystonia = muscles contract uncontrollably

298
Q

Basal ganglia support motor function through 2 main pathways:

A

Direct and indirect pathways

299
Q

Parkinson’s disease

A

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
Q

Deep brain stimulation in the STN reduces … Parkinson’s disease

A

Tremor

301
Q

Brain stem

A

Control of respiration

Smooth muscle

Gastrointestinal function

Stereotyped movements of the body

Reticular and vestibular nuclei control whole body movement and posture

302
Q

Anencephaly is a rare developmental disorder where the newborn is missing…

A

All the brain structures ABOVE the brain stem

303
Q

What is perception?

A

Conscious interpretation of sensations

304
Q

What do visceral senses detect?

A

Conditions within internal organs

305
Q

Name the 4 modalities of somatic sensation

A

Tactile, thermal, pain, proprioceptive

306
Q

What do we mean by a transduction of a signal?

A

Conversion of the energy into a stimulus into a graded potential

307
Q

Name the micro structures of a receptor cell

A

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
Q

How is the intensity of a stimulus encoded?

A

Frequency of action potentials

309
Q

What are phasic receptors specialised for?

A

Rapidly adapt and specialised for signalling changes in a stimulus

310
Q

What is the ligand for a sour gustatory receptor?

A

Hydrogen ions

311
Q

What type of cell is a olfactory receptor cell?

A

Bipolar neuron

312
Q

What type of cell is involved in olfactory transduction?

A

G protein coupled receptor

313
Q

What is the iris of the eye concerned with?

A

Regulation of pupil size

314
Q

What structures are important for focussing light?

A

Cornea, lens, zonular fibres and ciliary muscles

315
Q

Name the cell types in the retina

A

Photoreceptors, horizontal cells, bipolar cells, amacrine cells, ganglion cells

316
Q

What is the membrane potential of a rod in the dark?

A

Depolarised

317
Q

Examples of a NON visual response to light

A

Pupil light reflex
Increased HR and temperature
Improved alertness and performance
Melatonin suppression
Resetting the clock

318
Q

What does the amplitude of a sound wave describe?

A

How loud the sound is (decibels)

319
Q

Name the structures of the middle ear

A

Malleus, incus and stapes

320
Q

What are the key features of the hair cells in the inner ear that are involved in sound transduction?

A

Stereocilia with tip links and cation channels

321
Q

What structures are involved in monitoring head tilt?

A

Utricle and saccule

322
Q

What structures are involved in monitoring head rotation?

A

Semi circular ducts with ampulla

323
Q

EEG allows to record changes in … due to electrical signalling in the …

A

Voltage
Brain

324
Q

The brain shows … when recorded with EEG

A

Several rhythms

325
Q

EEG rhythms are divided by their …

A

Frequency

326
Q

Synchronisation and oscillations can be established through a … or feedback inhibition

A

Pacemaker

327
Q

… manifests as episodes of hypersynchronous EEG activity

A

Epilepsy

328
Q

Sleep is divided into different sleep …

A

Stages

329
Q

Sleep stages are identified based on characteristic …and other physiological signatures

A

EEG

330
Q

Spectral analysis allows … analysis of sleep EEG dynamics

A

Detailed

331
Q

Neuromodulators control sleep through the change of …. Patterns

A

Neuronal firing

332
Q

Sleep plays a crucial role in …

A

Memory consolidation

333
Q

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 …

A

Synchronised
Small
Large

334
Q

Brain rhythms exist in all …

A

Mammals

335
Q

What are the 2 mechanisms of brain rhythms?

A

Central pacemaker (conductor)

Feedback inhibition (collective)

336
Q

Epilepsy can be caused by mutations that cause an imbalance between excitation and inhibition, such as:

A

Mutant sodium channels with increased excitation

Mutant GABA channels with reduced inhibition

337
Q

EEG is the routine diagnostic test for …

A

Epilepsy

338
Q

What are the 3 main stages of sleep?

A

WAKE
Non REM
REM sleep

339
Q

Spindle oscillations occur in EEG recordings during …

A

Sleep

340
Q

Acetylcholine, serotonin and cortisol distinguish non REM from … sleep

A

REM

341
Q

Emotions exist in … and …

A

Animals
Humans

342
Q

Basic emotions can be described in …

A

Humans

343
Q

Emotions evoke typical bodily …

A

Reactions

344
Q

Subconscious emotions evoke … and brain …

A

ANS
Activation

345
Q

Emotional processing is a distributed brain feature, key areas are:

A

Frontal cortex
Cingulate cortex
Amygdala
Hypothalamus

346
Q

The amygdala is crucially involved in the processing of …
Eg during classical conditioning

A

Fear

347
Q

The hypothalamus is a key brain area involved in the regulation of … behaviour

A

Aggressive

348
Q

What are the 5 basic emotions?

A

Happiness
Sadness
Anger
Fear
Disgust

349
Q

What is the Cannon Bard theory?

A

Emotional experience is generated by the brain first and may be independent of emotional expression
= physiological changes

350
Q

What is the James Lang theory?

A

Emotional experience appears as a response to physiological changes in our body

351
Q

What does the limbic system include?

A

Amygdala
Hippocampus
Cingulate gyrus
Pre frontal cortex
Thalamic nuclei

352
Q

What was Antonio Damasio’s somatic marker hypothesis?

A

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
Q

Sham rage only occurs if the posterior hypothalamus is left …

A

Intact

354
Q

Affective aggression is due to the …

A

Medial hypothalamus

355
Q

Predatory aggression is due to the …

A

Lateral hypothalamus

356
Q

Mental health science links …mechanisms to pathological changes in behaviour

A

Genetic, molecular and brain

357
Q

Developing novel treatments will rely on … approaches
Eg induced pluripotent stem cells

A

Molecular medicine

358
Q

Anxiety disorders are characterised by constant and … anxiety and worry

A

Excessive

359
Q

Anxiety can be due to activation of the …

A

HPA

360
Q

Amygdala enhances / hippocampus reduces … activation

A

HPA

361
Q

Psychotherapy and pharmacotherapy are used to treat …

A

Anxiety

362
Q

Major depression occurs to about … of the general population

A

5-10%

363
Q

Antidepressants include … and more recently …

A

SSRI
Ketamine

364
Q

MD is a complex disorder caused by … factors

A

Genetic, developmental and environmental

365
Q

Reduced serotonin signalling is a major cause of …

A

Depression

366
Q

Most current antidepressants block re uptake of … at the synaptic cleft = increased serotonin

A

Serotonin

367
Q

How does ketamine work?

A

Blocks NMDA receptors on inhibitory inter neurons

Activates other signalling pathways for protein translation and synaptogenesis

368
Q

What are the 2 main types of muscle tissue in the body?

A

Striated and smooth

369
Q

What is the name of the synapse between a motor neuron and a muscle?

A

Neuromuscular junction

370
Q

What is the difference between EPSP and IPSP?

A

Excitation and inhibition

371
Q

What is the post synaptic receptor of the neuromuscular junction?

A

Nicotinic acetylcholine receptor

372
Q

Which neuron fires first during the stretch reflex?

A

La neuron

373
Q

What are the main descending motor pathways in the spinal cord?

A

Lateral and ventromedial pathways

374
Q

What is the function of the tectospinal tract?

A

Support eye movements

375
Q

What is somatotopic representation?

A

The mapping of motor function to different parts of M1

376
Q

What is a function of the premotor area?

A

Preparation for movement

377
Q

When does a mirror neuron (MN) fire?

A

MN fire when observing movements in others

378
Q

What brain structures form the 2 main sub cortical loops that support motor function?

A

Cerebellum + basal ganglia + thalamus

379
Q

What is ataxia?

A

Impairments in movement

380
Q

What are neurons that form a large part of cerebellum?

A

Purkinje cells

381
Q

What is the net effect of the direct pathway on the motor cortex?

A

Excitation

382
Q

What is the final effect of deep brain stimulation in PD patients?

A

Disinhibition of the thalamus

383
Q

What is located in peyer’s patches of the ileum?

A

Gut associated lymphoid tissue GALT

384
Q

During emulsification of large lipid globules, the … region of bile salts interacts with the lipid and the … region interacts with chyme

A

Hydrophobic
Hydrophilic

385
Q

When blood pressure … this leads to … aldosterone secretion

A

Decreases
Increased

386
Q

What is the mechanism by which dipeptides are absorbed in the small intestine?

A

Hydrogen co transporters

387
Q

Enterokinase is a brush border enzyme .
If it was ABSENT which is the following processes would be inhibited?

A

The conversion of trypsinogen into trypsin

388
Q

Increased pressure in which segment of the gastrointestinal tract results in ‘reverse’ peristalsis?

A

Rectum

389
Q

The direction of a sound source is computed in the …

A

Cerebrum by comparing the signal from both ears

390
Q

The … of a sound wave indicates the pitch and the … indicates the loudness

A

Frequency
Amplitude

391
Q

An action potential is elicited in a sensory neuron during a reflex movement.
Order the events that occurs during

A
  1. Na+ channels open leading to
  2. Depolarisation
  3. K+ channels open leading to
  4. Repolarisation
  5. Returns to resting state potential
392
Q

Which brain areas are part of the Papez circuit?

A

Amygdala
Cingulate gyrus
Hippocampus

393
Q

What are the basic emotions?

A

Disgust
Anger
Fear
Happiness
Sadness

394
Q

Which brain area is involved in deliberate and abstract motor planning?

A

Supplemental motor area SMA

395
Q

What neurons form a large part of cerebellum?

A

Purkinje cells

396
Q

What is the function of the tectospinal tract?

A

Support body orientation based on visual information

397
Q

What is the name of the 1st brain rhythm described?

A

Alpha

398
Q

What are the 2 mechanisms for generating synchronised activity in neuronal networks?

A

Pacemaker and feedback inhibition

399
Q

What is a cause of epilepsy?

A

Mutant sodium channels that cause increased excitation

400
Q

What is a sleep stage?

A

N3

401
Q

What is a characteristic oscillation linked to NREM 2 sleep?

A

Spindle

402
Q

Which neuromodulator concentration is increased during REM sleep?

A

Acetylcholine

403
Q

What parts of the nervous system are involved in processing emotions?

A

Amygdala and ANS

404
Q

Which part of the amygdala integrates sensory and aversive stimulus info during fear conditioning?

A

Basolateral nuclei

405
Q

Which part of the brain mediates sham rage?

A

Hypothalamus

406
Q

Which neural pathways is crucially involved in anxiety disorder?

A

HPA

407
Q

What is the effect of the amygdala on the HPA?

A

Excitatory

408
Q

What is the mechanism of action of anti depressants?

A

Blocking re uptake of serotonin

409
Q

What are pre cursors for induced pluripotent stem cells?

A

Somatic cells

410
Q

What is the effect of Benzodiazepine on GABA receptors?

A

Increase chloride influx

411
Q

EEG amplitude depends on … inputs to cortical neurons

A

Synchronous

412
Q

A clinical disorder which results in the autoimmune destruction of GASTRIC PARIETAL CELLS would prevent the absorption of what nutrient?

A

Vitamin B12

413
Q

What enzyme is located at the brush border of the small intestine and plays a role in carbohydrate digestion?

A

Lactase

414
Q

What nutrient in the diet would NOT be soluble in water?

A

Triaglycerol

415
Q

Correct order of layers in the gastrointestinal wall

A

Mucosa
Submucosa
Muscularis externa
Serosa

416
Q

What is FALSE about the peristaltic contractions in the GI wall?

A

Their main function is mixing of food bolus with digestive enzymes

417
Q

What is true about gastric acid secretion?

A

The secretion is initiated in the cephalic phase before food enters the stomach

418
Q

What are the main descending motor pathways in the spinal cord?

A

Lateral and ventromedial pathways

419
Q

What is NOT an accessory organ to the GI tract?

A

Ileum

420
Q

Which of the following cell types is essential for the digestion of proteins?

A

Parietal cell - secretes hydrochloric acid and intrinsic factor - denatures protein and activates pepsinogen

421
Q

During the pharyngeal stage of swallowing, the medulla oblongata sends a signal to trigger the movement of what structures?

A

Uvula

Soft palate

422
Q

What is true about gastrin?

A

Strengthens the contraction of the lower oesophageal sphincter muscle

423
Q

Presence of chyme in the duodenum stimulates what?

A

Sympathetic nervous system

424
Q

What can cause an increase in pH of the GI tract?

A

Secretin

425
Q

Examples of active transport?

A

Sodium glucose co transporters in small intestine

Transcytosis of small peptide chains

426
Q

What enzymes are located at the brush border?

A

Lactase

Aminopeptidase

427
Q

Decreased blood pressure leads to increased aldosterone levels which leads to … absorption of sodium and … vasodilation

A

Increased
Decreased

428
Q

Gastrin does NOT directly influence what enzyme?

A

Trypsin

429
Q

Thermo receptors are …

A

Phasic receptors

Constant prolonged stimulus

430
Q

What special sense has a receptor that is 1st order neuron?

A

Olfactory

431
Q

Put the retinal layers in order that light passes through them

A

Ganglion cell layer

Inner synaptic layer

Bipolar cell layer

Outer synaptic layer

Photoreceptor cell layer

432
Q

What would NOT apply to a touch receptor in the skin?

A

It is a visceroceptor

433
Q

What special sense does NOT involve a G protein coupled receptor?

A

Detection of a sour gustant

434
Q

In a cone photoreceptor, what is the consequence of a depolarising membrane potential?

A

Increase in NT release

Hyperpolarisation of bipolar cells

YEAR 2 - Physiology (2 decks)

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