GI Histopathology and Visceral Afferents Flashcards

Question

Identify which muscle type each one is

Answer 1

``` CNS: Neurons Supporting cells Oligodendroglia, astrocytes Schwann cells, microglia ``` PNS: Bundles of parallel elongated fibres Wavy, zig zag configuration

Answer 2

Nervous tissue

Answer 3

Microscopic examination of cells and tissue to study disease The gold standard diagnostic technique

Answer 4

Transformation of one differentiated cell type to another differentiated cell type

Answer 5

An abnormality of development Epithelial dysplasia- loss of maturation

Answer 6

Pale pink squamous mucosal lining

Answer 7

Basal cells (single layer) including stem cells

Answer 8

``` Hiatus hernia Obesity/pregnancy Gastric distension by food/gas Stress Alcohol and tobacco/drugs ```

Answer 9

Unprotected squamous mucosa

Answer 10

infiltration of the damaged surface epithelium by neutrophil polymorphs and eosinophils basal cell hyperplasia as epithelium proliferates to replace damaged cells

Answer 11

Inflammation, secondary to reflux of acidic gastric contents

Answer 12

Hyperplasia

Answer 13

Peptic ulceration, i.e. acid-induced benign ulceration Replacement of squamous mucosa by glandular mucosa. Columnar metaplasia = Barrett’s oesophagus Development of dysplasia in Barrett’s oesophagus Development of adenocarcinoma in Barrett’s oesophagus

Answer 14

Complete break in mucosa, discontinuation in mucosa. Inflammatory slough with fibrin on surface Base of ulcer formed from granulation tissue consist of early fibrosis with proliferation of new capillaries (later forms fibrosis or scar tissue)

Answer 15

As peptic ulcer heals scar tissue can form leading to peptic stricture in oesophagus

Answer 16

Complication of GORD The squamous mucosa undergoes metaplasia from the normal squamous epithelium to columnar epithelium (glandular type epithelium) (acid reflux causes metaplasia)

Answer 17

Metaplasia is the reversible replacement of one mature type of epithelium by another in response to adverse circumstances. Columnar cell metaplasia in oesophagus = Barrett’s oesophagus 2º v(secondary) to GORD/reflux oesophagitis Mucus barrier of columnar epithelium protects against acid Metaplasia is reversible if the stimulus is removed.

Answer 18

Metaplastic columnar epithelium

Answer 19

Barrett’s metaplasia is often a mixture of non-specialised gastric-type mucosa and intestinal metaplasia Intestinal metaplasia with goblet cells

Answer 20

Premalignant change within the epithelium Characterised by: Impaired cell differentiation : disorganised, often failing to mature towards surface Atypical nuclear features, eg pleomorphism Increased numbers of mitoses

Answer 21

Dysplasia in Barrett’s oesophagus: surface epithelium shows multilayering of nuclei, with hyperchromatism, pleomorphism and increased mitoses Non-dysplastic metaplastic columnar mucosa in Barrett’s oesophagus

Answer 22

Carcinoma of oesophagus presents with dysphagia due to luminal narrowing and infiltration of the wall, inhibiting peristalsis

Answer 23

Intestinal type formed by irregular glands Diffuse type (signet ring carcinoma)

Answer 24

Normal squamous mucosa shows orderly maturation from the basal layer to the surface. Squamous epithelial dysplasia in the oesophagus. Disordered maturation and increased mitotic figures.

Answer 25

Mid or upper oesophagus

Answer 26

lower oesophagus and GOJ (gastroesophageal junction)

Answer 27

Specialised gastric mucosa Mucous neck cells secrete a blanket of mucus over the surface which protects it from digestion by enzymes and acid.

Answer 28

Parietal cells (pink-staining) secrete gastric acid Chief cells (purple-staining) secrete pepsinogen, which is activated by acid in the lumen of the stomach to form the active protease enzyme pepsin.

Answer 29

Non-specialised gastric mucosa Glands formed by mucus producing cells

Answer 30

MUCUS BLANKET continually secreted by mucus neck cells BICARBONATE BUFFER LAYER secreted by epithelial cells in gastric neck/isthmus

Answer 31

Drugs, alcohol and H. pylori infection Mucus blanket relies on intact mucin neck cells for production so any inflammatory stimulus will interfere

Answer 32

Bicarbonate (HCO3-) secretion is stimulated by prostaglandins, produced from arachidonic acid by COX pathway, inhibited by NSAIDs

Answer 33

Pepsin forms from pepsinogen in acid-rich environment

Answer 34

Parietal: acid Chief: pepsinogen, not activated until pH is low

Answer 35

Infiltration by acute inflammatory cells like neutrophils and chronic inflammatory cells like plasma cells and lymphocytes

Answer 36

NSAIDs and H. pylori

Answer 37

Gastric peptic ulcer in stomach Duodenal peptic ulcer in duodenum Peptic-type ulceration is due to acid.Seen in oesophagus, stomach and duodenum

Answer 38

Intestinal-type adenocarcinomas usually present as ulcers or polypoid tumours. Ulcerated adenocarcinoma has a ‘rolled’ everted edge, unlike the overhanging edge of benign peptic ulcer

Answer 39

Gastric peptic ulcer: surface has granulation tissue with inflammatory slough, NO epithelial cells in submucosa Adenocarcinoma: nests of irregular glands invading from mucosa into submucosa and into muscularis propia

Answer 40

Gastric peptic ulcer: surface has granulation tissue with inflammatory slough, NO epithelial cells in submucosa Adenocarcinoma: nests of irregular glands invading from mucosa into submucosa and into muscularis propia

Answer 41

Stomach often shrunken, thickened and non-distensile; patient may present with early satiety.

Answer 42

musculoskeletal (joint pain, myofascial pain), cutaneous; often well localized

Answer 43

hollow organs and smooth muscle; usually referred

Answer 44

pain initiated or caused by a primary lesion or disease in the somatosensory nervous system.

Answer 45

Not all internal organs sensitive to pain e.g. liver, lungs, kidneys – no nociceptors Stretching of hollow viscera such as gall bladder, ureters, colon can cause excruciating pain no close relationship between severity of damage and severity of pain

Answer 46

Immune cells in gut wall

Answer 47

Pacemaker cells

Answer 48

``` Oesophageal distension Gastric distension – fullness Nutrient density in stomach/duodenum Nausea-toxins or excess nutrients Movement of gas Pain Awareness of rectal content Urgency ```

Answer 49

Vagal afferents Thoracolumbar (splanchnic) afferents (pain) Pelvic afferents (gut) Enteric afferents - viscerofugal neurons

Answer 50

Serosal/Muscular/Mesenteric – distension/contraction – mechanoreceptors Mucosal – entero-endocrine mediators ``` Musculo-mucosal Vascular afferents (serosal) ```

Answer 51

Intra-ganglionic – low threshold mechanoreceptors primarily in vagal and pelvic pathways (longitudinal muscle) Intramuscular afferents – mechanosensitive (muscular propria) Mucosal afferents – mucosal distortion and entero-endocrine cell mediators (vagal and spinal) (mucosa) Muscular-mucosal – mucosal stroking and distension/contraction – in vagal and pelvic pathways (submucosa) Vascular afferents – on extramural and intramural blood vessels – mechano-nociceptors – splanchnic and pelvic pathways (submucosa to longitudinal muscle) Entero-viscerofugal – interneurons with mechanosensitivity (LM)

Answer 52

Pain caused by ‘structural’ conditions - Inflammatory e.g. acid-peptic disease, - Neoplastic Pain caused by ‘functional’ conditions - Irritable bowel syndrome (include bloating) - Functional dyspepsia (include nausea)

Answer 53

``` Hollow organ distension Traction Ischaemia Acid/Irritant chemicals Inflammation Electrical stimulation ‘pinching’ does not cause pain except when hyperalgesic ```

Answer 54

‘Painful rib’ syndrome Spinal pain Pain from abdominal wall or inguinal ligaments Constant, can be sharp and momentary with movement or straining Well localised Unaffected by food, defaecation Affected by position, movement, straining Localised Tenderness, reproduces pain Subluxation of costal cartiledge tips causing impingement of the intercostal nerves

Answer 55

Acute appendicitis: - In early phase visceral intestinal pain – central abdominal, colicky - With onset of inflammation of parietal peritoneum, somatic pain localised to RIF - Worse with movement and straining - Tenderness at McBurney’s point

Answer 56

1. Treat disease e.g. peptic ulcer 2. Anti-spasmodics e.g. for irritable bowel syndrome 3. For visceral hypersensitivity use tricyclics e. g. Amitryptiline 4. Used in sub-anti-depressant doses 5. Start at low dose e.g. 10 mg nocte and step up 6. Main problem is sedation – take at 6 pm

Answer 57

Mild pain can become difficult to bear when patients are worried about it – leads to anxiety, panic etc Pain may not be noticed when engaged in other activities e.g. Watching TV ‘Painful rib’ syndrome – continuous pain day and night. Many patients cope with it much better once they understand it is not serious. Analogous to rheumatism

Answer 58

An oesophageal motility disorder causing dysphagia Degeneration of ganglion in myenteric plexus in oesophageal wall leading to motility disorder: - Aperistalsis - Incomplete lower sphincter relaxation - Treat by myotomy, pneumatic dilatation or botulinum toxin injection

Answer 59

Incompetent lower oesophageal sphincter, but resting pressure may be normal Gastric acid secretion usually within normal limits Oesophagitis seen at endoscopy but normal appearances in non-erosive gastro-oesophageal reflux Ambulatory lower oesophageal pH monitoring

Answer 60

Hypersensitivity | (hyperalgesia aka primary, local OR allodynia aka to non painful stimuli OR, secondary hyperalgesia aka generalised)

Answer 61

an increased sensitivity to feeling pain eg overuse of opiods ie exaggerated response

Answer 62

things that don’t normally cause pain eg very sensitive to touch/temperature

Answer 63

generalized response not just at the area of injury

Answer 64

1. Transient Receptor Potential Vanilloid-1 (TRPV-1) 2. Acid-Sensing Ion Channel (ASIC) Acid excites primary sensory neurons by activating TRPV1 and ASIC – leads to release of pro-inflammatory mediators and neurogenic inflammation Sensitive to mechanical, electrical and thermal stimuli

Answer 65

Erosive- mucosal damage | NERD- no mucosal damage

Answer 66

Lungs and trachea

Answer 67

NERD Posiitve result- abnormal acid exposure

Answer 68

Normal pH test May have symptoms associated with pH changes- hypersensitive oesophagus or just functional heartburn

Answer 69

Fundus – accommodates Antrum – grinding effect Food boluses converted into chyme Greasy and rich food delays gastric emptying Stomach secretes acid and pepsin Vagus, gastrin (secreted by G cells) and acetylcholine promotes acid secretion Proton pump - final common pathway for acid secretion

Answer 70

Often occurs in dysmotility type dyspepsia, sometimes associated with nausea, vomiting and weight loss Severe gastric emptying delay in gastro-paresis, often diabetic, sometimes post-infective Pro-kinetic drugs: domperidone, metoclopramide also helps nausea and vomiting Isotope gastric emptying study

Answer 71

``` 10-15% of the population 30% consult a physician Greater anxiety, lower quality of life Female preponderance No excess mortality Rome and Manning Criteria ```

Answer 72

Recurrent abdominal pain, on average, at least 1 day/week in the last 3 months, associated with two or more of the following criteria: Related to defecation Associated with a change in frequency of stool Associated with a change in form (appearance) of stool ``` Disorders of gut-brain interaction Related to: - Motility disturbance - Visceral hypersensitivity - Altered mucosal and immune function - Altered gut microbiota - Altered CNS processing ```

Answer 73

Distension in IBS -> abnormal sensory response, pain, urgency, feeling unwell normal sensory stimulus giving rise to different sensation increases with increasing distension (higher pressure = more sensitive to discomfort)

Answer 74

IBS with constipation >25% hard stools, <25% loose stools IBS mixed - both hard and loose stools IBS with diarrhoea >25% loose stools, <25% hard stools

Answer 75

Many possible causes: low fibre diet, medications such as opiates, hypercalcaemia, hypothyroidism Chronic constipation not a symptom of colon cancer Does not produce toxins, ill health or increase risk of colon cancer Functional types: colonic inertia – slow transit (can assess by marker studies), pelvic floor dys-synergia: pelvic muscles do not relax with defaecation Management similar for both types of constipation

Answer 76

More common in lower socioeconomic class Less fibre and less exercise F:M – 2.2:1

Answer 77

More common in lower socioeconomic class Less fibre and less exercise F:M – 2.2:1

Answer 78

Diet: Meta-analyses - Bran – less effect if constipated - Ispaghula RCTs - Prunes (sorbitol) - Kiwifruit - Vegetable and wholegrain powder - Fruit and fibre to porridge

Answer 79

Macrogol (polyethylene glycol) more effective and better tolerated than lactulose Macrogol - Proven efficacy in long term treatment - Improved stool frequency - Improved pain - Less need for other laxatives SE – diarrhoea, bloating

Answer 80

Osmotic: - Macrogol - Avoid lactulose Stimulant - Sodium picosulphate - Bisacodyl - Senna Stool softeners - Sodium docusate SE – osmotic – bloating SE – stimulant - cramps

Answer 81

``` Regular, small meals Fat reduction Caffeine Reduce lactose and fructose Reduce gas-producing foods Modify soluble/insoluble fibre Reduce wheat Low FODMAP diet (reduces bifidobacteria) ```

Answer 82

Gas related symptoms | Inverse relationship between pain and bifidobacteria

Answer 83

* Chest - oesophagus * Upper- oesophagus, stomach, duodenum, pancreas, gallbladder, colon * Mid – Small intestine * Lower – Colon, gynaecological Radiation to back with severe pain, biliary pain, pancreatic pain, spinal pain

Answer 84

Visceral pain lasts minutes/hours, intense can come and go Non visceral pain well localised, lasts for seconds or constant Exacerbated by movement, coughing, straining Nerve pains- shooting and needle-like, sharp Musculoskeletal- spinal, painful rib syndrome, pain over ligaments, bones and joints

Answer 85

Acid peptic: burning or dull (mild or moderately severe) Intestinal/colonic: colicky (extremely severe, bad or worse than labour pains) Biliary/pancreatic pain: constant or colicky (extremely severe)

Answer 86

heartburn, regurgitation, dysphagia, odynophagia

Answer 87

early satiety, post-prandial fullness, nausea

Answer 88

dark urine, pale stools, jaundice

Answer 89

diarrhoea, constipation, distension

Answer 90

* gastro-oesophageal reflux * functional dyspepsia * gastric ulcer/duodenal ulcer * ca stomach/oesophagus/pancreas/liver * cholelithiasis * acute or chronic pancreatitis * irritable bowel * Non-visceral pain: musculo-skeletal, neuralgic, cardiac * More than one cause of pain

Answer 91

* Oesophagitis – exacerbated by swallowing * Gastro-oesophageal reflux - exacerbated by food, drink, lying down, bending over, relieved by antacids, milk, sitting up * Peptic ulcer – nocturnal, worse on hunger, improved by food and antacids * Irritable bowel syndrome – pain gives an urge to defaecate, relieved by defaecation, distension

Answer 92

• ‘Test and treat’ for Helicobacter (if no alarm symptoms) • Blood count, ESR, LFTs, amylase • Plain X ray, urgent CT, if acute abdomen suspected • Ultrasound • CT • Upper endoscopy • Colonoscopy- not normally indicated for abdominal pain • Lower oesophageal pH study

Answer 93

* recurrent epigastric pain, heartburn or acid regurgitation, with or without bloating, nausea or vomiting * Also... postprandial fullness, early satiation and heartburn... * GORD and dyspepsia symptoms often overlap * Lower quality of life than pts with DM/CHF1

Answer 94

* Differential Diagnosis – cardiac and biliary disease * FBC * Medication review – calcium antagonists, nitrates, theophyllines, bisphosphonates, corticosteroids and NSAID’s * Offer H. pylori 'test and treat' to people with dyspepsia.

Answer 95

• H.Pylori Eradication – 83% had Symptoms (Sx) at 12 mths – 34% incurred further costs • PPI Therapy (proton pump inhibitor) – 84.5% had Sx at 12mths – 33% incurred further costs

Answer 96

``` • Fewer days of Sx during the 1st week of treatment • Age>40 • Symptoms > 3 mths • High Score for heartburn at baseline • Low Score for Epigastric Pain, bloating, diarrhoea at baseline • Low impairment of vitality at baseline ```

Answer 97

CT If expect a cancer, investigation done much more rapidly eg TWR- doesn't seem to be the case here Patient is under 5 so not seen as urgent to do this

Answer 98

dysphagia or aged 55 and over with WEIGHT LOSS and any of the following: • upper abdominal pain • reflux • dyspepsia (weight loss may be an indication of cancer- urgent)

Answer 99

A - 1 or more mucosal breaks no longer than 5mm, does not extend between tops of 2 mucosal folds B - 1 or more mucosal breaks more than 5mm long, does not extend between tops of 2 mucosal folds C - 1 or more mucosal breaks continuous between tops of 2 or more mucosal folds, involves less than 75% of circumference D - 1 or more mucosal break involving 75% at least of oesophageal circumference

Answer 100

8-12 weeks PPI works best over 8 week period Healing lasts up to 12 weeks

Answer 101

Better acid suppression when taken BEFORE a meal

Answer 102

Add in PPI BID (twice daily) and H2 receptor antagonist Improves gastric acid control and decreases nocturnal acid breakthrough (bc taken morning and night)

Answer 103

• Step 1 check adherence • Step 2 confirm diagnosis – Does the patent really have GORD? do endoscopy if necessary What % of patients with PPI refractory reflux symptoms (heartburn and regurgitation) do not have GORD? – 50%

Answer 104

If PPIs not tolerated (cause diarrhoea, headaches, dizziness, tiredness) or patient has concerns about long term use of tablets

Answer 105

* Anorexia * Weight loss * Persistent vomiting * Anaemia * Haematemesis and melaena * Abdominal mass

Answer 106

• Lifestyle – Wt loss, elevation of head of bed, smoking, meal times, (CBT, psychological therapies in dyspepsia) • Medical – Antacids, alginates, H2RA,PPI, prokinetics • Surgical – Fundoplication • New endoscopic and surgical techniques

Answer 107

• Lifestyle and postural measures: - Avoid alcohol, smoking, greasy food, caffeine, weight reduction - Small meals, eat and drink separately - No food or drink for 3 hours before going to bed - Elevate the head of the bed * Pharmacological treatment - PPI * (Endoscopic treatment) * Fundoplication

Answer 108

Non-erosive, Grade A and B – treat symptomatically Grade C and D – probably need long- term treatment When it does heal some patients will habe Barrett's oesophagus- 0.5% annual risk of adenocarcinoma, endoscopy to look for dysplasia

Answer 109

``` • Most common procedure • Under general anaesthetic • Upper portion of stomach is wrapped around distal oesophagus • Common side effects include: – dysphagia – belching – bloating – flatulence ```

Answer 110

Augment oesophageal sphincter and increase barrier function of lower sphincter

Answer 111

Metallic bead wrapped around lower sphincter to augment barrier function

Answer 112

* Gastric or duodenal * Most cases due to H pylori infection or aspirin/NSAIDs * ‘No acid, no ulcer’: reduction in gastric acid heals ulcers * Can be uncomplicated, Bleeding or perforated * Gastric ulcer can be malignant: need follow-up to healing, but not duodenal ulcer won't be

Answer 113

They can be malignant (cancerous), unlike duodenal ulcers

Answer 114

* Treat Underlying Cause: H pylori infection or aspirin/NSAIDs * Acid Suppression – PPI * Gastric ulcer to be followed up to healing, not necessary for duodenal ulcer * Check for Helicobacter eradication if history of complications * Bleeding ulcer – maintain haemodynamic stability, endoscopic treatment * Perforated ulcer - surgery

Answer 115

* H pylori infection associated with peptic ulcer which can be cured by antibiotic treatment * Most patients with H pylori infection do not have ulcer, only gastritis. Some have dyspepsia. * Dyspepsia cured by treatment of H pylori infection in <10% of patients with functional dyspepsia and H pylori.

Answer 116

``` BO occurs in patients with longstanding reflux symptoms (perhaps >10 years) But screening for BO not routinely justified ``` ``` Only consider if ≥3 risk factors: • Males • Obese individuals • those aged >50 • Caucasian • FH of Barrett’s or oesophageal ca, • Smoking ```

Answer 117

Length of lining of oesophagus Prague classification: Circumference length = C number Maximum length = M number image: C3M5

Answer 118

Take into account two endoscopic factors: presence/absence of Intestinal Metaplasia and length of segment: • Without intestinal metaplasia and <3cm – single repeat endoscopy in 3-5 years • With intestinal metaplasia: <3 cm - 3-5 yearly >3 cm – every 2-3 years • Patient co-morbidity and preference

Answer 119

Brainstem cranial nerves Sacral S2-S4

Answer 120

3- oculomotor 7- facial 9- glossopharyngeal 10- vagus

Answer 121

SHORT (close to end organs)

Answer 122

Acetylcholine at muscarinic receptors

Answer 123

Acetylcholine at nicotinic receptors

Answer 124

Acetylcholine at M2 receptors

Answer 125

SA node | AV node

Answer 126

Stimulation of vagus nerve releases Ach which acts at M2 receptors ↓ Pacemaker potential frequency at SA node leading to  in heart rate ↓ Electrical conduction through atria-ventricular node to balance ↓ heart rate to contraction Using : CO = HR x SV Stimulation of vagus nerve (↓ HR) will DECREASE CARDIAC OUTPUT

Answer 127

do not innervate ventricles, most blood vessels -> do not affect contractility (SV) or TPR

Answer 128

Exception : male genitalia, where release of NO (not Ach) causes dilatation of vessels to cause erection

Answer 129

Pacemaker cells have hyperpolarised Na channel (If) -> hyperpolarisation, then repolarisation influx of Na depolarises membrane and strikes up another AP Parasympathetic stimulates M2 receptors = activation of GPCRs (Gi class) Gi causes inhibition of Adenylate cyclase → decreased conversion of ATP to cAMP → less cAMP = ↓ If current = ↓ pacemaker potentials in SA node → reduced HR

Answer 130

Drugs that inhibit Mus receptors can increase HR by inhibiting parasympathetic action Mus antagonist, e.g. Atropine used to  HR following sinus bradycardia after MI Caution Tachycardia - potential side effect of Mus antagonists given for other reasons

Answer 131

Mus agonists, e.g. Bethanechol, used to treat urinary incontinence may induce bradycardia

Answer 132

Pupil diameter Intra-ocular pressure Accommodation (focusing)

Answer 133

Stimulation of M3 receptors lead to constriction of the circular smooth muscle of the iris (constrictor pupillae), constrict of the pupil (miosis)

Answer 134

Constriction of the pupil (M3) has a secondary action on opening the canal of Schlemm at the side of the pupil Drains aqueous humour from eye, reducing pressure within the eye

Answer 135

Mus agonist, e.g. Pilocarpine - lowers intraocular pressure in glaucoma Mus antagonists – dilate pupil to examine retina Eye drops have less systemic side effects

Answer 136

Ciliary muscle relaxed Suspensory ligaments taut - pulls lens Long thin lens Little refraction to focus

Answer 137

CLOSE VISION: stimulates parasympathetic nerves Stimulation of oculomotor nerve (3) → Ach release → acts on M3 receptors → contracts smooth muscle cells → Ciliary muscle contracted causes Ciliary bodies moving inwards/forwards so Suspensory ligaments relaxed Bulged lens shape → Increased refraction to focus

Answer 138

Both Muscarinic agonists and antagonists can cause blurred vision

Answer 139

Parasympathetic, sympathetic, motor and sensory afferent nerves

Answer 140

Coordinates bladder reflex to cause voiding

Answer 141

Lumbar region of spinal cord

Answer 142

Pre ganglionic SNS fibres get info from micturition centre -> send info via pre and post ganglionic fibres to bladder and innervate: 1. Muscle wall (detrusor muscle - smooth muscle cells) 2. Internal sphincter Release Noradrenaline to act on B2 receptors on detrusor muscle to cause relaxation, expanding bladder enabling bladder to fill more NA also at A1 receptors at internal sphincter constricting smooth muscle to 'close the tap' so no leaky bladder

Answer 143

Parasympathetic pre ganglionic fibres in Sacral region of spinal cord - receive info from micturition centre and send info via pre and post ganglionic fibres to detrusor muscle of bladder → Release Ach acting on M3 receptors of smooth muscle cells in bladder wall → contraction Increases pressure and helps eject urine from bladder

Answer 144

Motor nerves travel to smooth muscle cells of external sphincter of bladder, act at nicotinic receptors to contract (hold) or relax (void) Motor nerves travel from sacral region of spinal cord

Answer 145

Sensory nerves (mechanoreceptors) found in wall of smooth muscle of bladder wall, sense when bladder is full Stimulated when bladder is full → send info to micturition centre that bladder is full

Answer 146

When bladder full- SNS innervation = relaxation of wall + contraction of internal sphincter Stimulates sensory nerves = send info to micturition centre to switch off SNS, turn on PNS → M3 receptors in bladder wall contract So internal sphincter opens bc SNS gone and detrusor muscle wall contracts = increased pressure and tap open so able to void Motor system allows external sphincter to relax in order to void

Answer 147

Mus agonists, e.g. Bethanechol – urinary incontinence due to detrusor neuropathy Helps bladder to void in cases where PNS innervation may not be able to work (incontinence bc without contraction of detrusor muscle person can't void)

Answer 148

Mus antagonists, e.g. oxybutynin – urinary incontinence due to over activity bladder Overactive bladder, too much stimulation so bladder doesn't fill properly and always wants to void so block M3 receptors to slow down this frequency

Answer 149

Vagus nerve

Answer 150

M3 receptors

Answer 151

Stimulation of vagus nerve releases Ach which acts on M3 receptors ↓ Contraction of circular and longitudinal smooth muscle in GI tract ↓ Increased motility Vagus also contains afferent (sensory) fibres – peristaltic reflex control

Answer 152

Salivary glands- VII (facial) & IX (glossopharyngeal) Stimulate acinar cells ↑ Amylase / mucins

Answer 153

Gastric glands - X (vagus) Stimulate parietal cells ↑ Gastric acid

Answer 154

Pancreatic glands - X (vagus) Stimulate acinar + islet cells ↑ Pancreatic secretions, e.g. insulin

Answer 155

Mus antagonists, e.g. Hyoscine (Buscopan) – treat IBS-like symptoms May cause tachycardia, blurred vision etc

Answer 156

Stimulation of M3 receptors contracts bronchi smooth muscle cells causing bronchoconstriction Parasympathetic innervation

Answer 157

Stimulation of M3 receptors contracts bronchi smooth muscle cells causing bronchoconstriction- need to reduce this aka reduce M3 stimulation to increase airflow Thus, anti-muscarinic drugs are used as bronchodilators, e.g. Ipratropium Tiotropium Used in COPD (chronic obstructive pulmonary disease) Need to increase airway flow

Answer 158

In patients with bladder outflow problems and glaucoma Mus antagonist will reduce urine outflow, increase intraocular pressure Conditions also associated with elderly (as is COPD) These are potential contraindications

Answer 159

IN SM CELL: ``` Ach binds to M3 M3 is GPCR → Gq pathway stimulated → activates phospholipase C = PIP2 broken down into DAG + IP3 → IP3 water soluble so moves to cytoplasm → binds to IP3R on sarcoplasmic reticulum → opens ligand gated calcium channels (IP3 MEDIATED CALCIUM RELEASE) = rise of calcium in cell ``` (meanwhile DAG → activates protein kinase C → acts on ion channels to increase membrane excitability = depolarisation) Depolarisation = activation of voltage gated calcium channels → calcium enters cell = rise in calcium in cell ``` So now rise in calcium → Calcium calmodulin → myosin light chain kinase → myosin light chain- phosphorylated → actin-myosin interactions = contraction ```

Answer 160

Specialised sacral parasympathetic ‘vasodilator’ nerves innervate erectile tissue Stimulation of these nerves release nitric oxide (NO) NOT Ach Remember this is an exception to the normal rule NO is a lipophilic, membrane-permeable gas NO causes relaxation of vascular smooth muscle cells composing the corpus cavernosum Corpus cavernosum dilates and fills with blood Produces and maintains erection

Answer 161

Sildenafil (Viagra) - erectile-dysfunction, prevents breakdown of the actions of NO – increasing it vasodilator effects

Answer 162

M2 receptor

Answer 163

Muscarinic antagonist | remember M2 receptors in heart slow down HR

GI Histopathology and Visceral Afferents Flashcards

(200 cards)