Basic Science MRCS Physiology Flashcards

Question

Surfactant functions

Answer 1

Lower surface tension- increase compliance- reduce work of breathing Prevent fluid accumulation Reduce tendency to collapse

Answer 2

Laplace Alveolar pressure= 2 Tension/R So smaller alveoli more prone to collapse - since generate larger pressure causing air to travel to larger alveoli Therefore smaller alveoli have more surfactant to lower their Tension more

Answer 3

change in volume/change in pressure

Answer 4

Increase- emphysema due to destruction of elastic tissue Decrease- fibrosis, oedema, reduced surfactant, supine, mechanical ventilation due to reduced blood flow

Answer 5

1/3 nose, pharynx, larynx 2/3-tracheobronchial tree little distally

Answer 6

Change in pressure/change in volume

Answer 7

Helium dilution method

Answer 8

Fowler method- breath of pure O2 nitrogen components measured - as alveolar has nitrogen from old breathing Calculated from Bohr equation

Answer 9

Anatomical- increase size of patient Standing Bronchodilation Physiological Hypotension Hypoventilation Emphysema and PE PPV

Answer 10

Volume at which small airways at base start to close Usually 10% of VC Breathes out to FRC- takes 100% O2 Point between phase 3+4 on curve- there is an increase in 4 as only the poorly ventilated upper lobes are open

Answer 11

Obstructive- concave expiration phase Restrictive- normal shape, volume lower

Answer 12

Apex Due to weight- causing pleural fluid - more negative intrapleural pressure and compliance differences

Answer 13

Hydrostatic pressure in PA Pressure in PV Pressure of air in alveoli

Answer 14

1- apex- alveolar pressure similar to PA- smaller vessels compressed- low flow 2-PA is higher- increased flow 3- PA greatly exceeds These are only true with standing up

Answer 15

Changes very little Due to increase in CO Causes Recruitment of additional vessels- many caps at rest closed Vessels getting distended

Answer 16

3 at apex- ventilated more than perfused 2/3 up chest-1 Base- 0.6- better perfused than ventilated

Answer 17

Interstitial oedema- doesnt affect ventilation at first- but once large enough to affect lymph to cause alveolar oedema Alveolar oedema- fill with fluid- increasing surface tension and shrinking alveoli leading to vasoconstiction due to hypoxia Airway oedema- causing blood tinged frothy sputum

Answer 18

Known cause Acute Fluffy infiltrates PWP- <18

Answer 19

1- Intially active exudate- inflammtory mediators, proteases Damage lung and Increase cap perm Thrombosis and haemorrhage in alveolar capillaries- alveolar collapse - decreased lung compliance 2-Regeneration of type 2 pneumocytes- organisation with fibrosis, and obliteration of alveolar space

Answer 20

Pressure gradient - partial pressure Diffusion coefficient- how well it can diffuse- determined by solubility and molecular weight Tissue factors- large SA, short diffusion distance -

Answer 21

Pulmonary surfactant Alveolar epithelium BM Pulmonary endothelium

Answer 22

Travel through lungs without contact with ventilated alveoli Bronchial veins Pneumonia

Answer 23

Fetal comprimised of 2a 2y- shift to left Myoglobin- even further left to provide additional O2 in anaerobic

Answer 24

HCO3- 60-70% formed in red cell and diffuses out- Cl- replaces it in red cell- reversed in alveoli Carbamino- between proteins mostly globin- 20-30% Dissolved 10%

Answer 25

Co2 solubility greater Normal range of PaCo2 smaller Blood cannot be saturated with CO2- so no plateau

Answer 26

CO2 carried increases as O2 levels fall At given partial pressure Co2 carried increases

Answer 27

Central- close to medulla Change relative to pH Increase resp rate if CO2 increases Peripheral Carotid bifurcation and aortic arch pH and PO2 Only PO2 when abnormally low- <8

Answer 28

Strech receptors in lung - prevent over inflation via vagus

Answer 29

Increased HR Increased CO Vasoconstriction in skin and splanchnic

Answer 30

Increased minute volume RBC CO Vascularity of organs

Answer 31

* ventilator-induced injury * volutrauma * barotrauma * hypotension and decreased cardiac output: decreased venous return due to positive intrathoracic pressure * respiratory muscle atrophy * nosocomial infections * technical complications, e.g. disconnection * increase in intracranial pressure (ICP) due to the increase in intrathoracic pressure.

Answer 32

Controlled mandatory ventilation- no resp effort- set volume Synchronised intermittent MV- less sedation- some breath initiated by patient Pressure controlled ventilation- reduces risk of barotrauma Pressure support ventilation- used in combo- allows weaning by triggering breath

Answer 33

In the absence of calcium the troponin/tropomysin complex inhibits cross-bridging between actin and myosin filaments. * When calcium binds to troponin, formation of cross-bridging occurs between the filaments. The filaments then slide over one another to cause contraction

Answer 34

Arrival of the action potential allows Ca2+ to move from the sarcoplasmic reticulum into the cytoplasm. * Ca2+ binds to troponin C, eventually activating the actin–myosin complex, resulting in contraction. * The plateau phase, the result of further calcium influx, prolongs and enhances contraction. * The cardiac action potential is very long (200–300 ms). After the contraction there is a refractory period when no further action potentials can be initiated and therefore no contraction occurs. The long action potential and refractory periods ensure contraction and relaxation of the heart, allowing the chambers to fill during relaxation and empty during contraction. * Intracellular Ca2+ is the most important factor controlling myocardial contractility: * increased intracellular Ca2+ increases force of myocardial contraction * decreased intracellular Ca2+ decreases the force of myocardial contraction

Answer 35

SA- right atrium near SVC entrance AV_ fibrous ring on right side of atrial septum

Answer 36

Ability to depolarise at regular intervals- self excitation Long refractory period- so cells with highest frequency (SA node) control HR

Answer 37

RA- 0-4 RV- 25/0-4 PA- 25/15 LA-5-10 LV- 120/0-10

Answer 38

EF= SV/LVEDV

Answer 39

Coronary flow occurs mainly during diastole. * Conditions resulting in low diastolic BP or increased intramyocardial tension during diastole (e.g. an increased end diastolic pressure) may compromise coronary blood flow. * Subendocardial muscle, where the tension is highest, is particularly vulnerable. * Diastolic time is important. At fast rates, inadequate myocardial perfusion occurs.

Answer 40

* venous return * atrial systole (fibrillation) * myocardial distensibility

Answer 41

central venous pressure (CVP) * pulmonary artery occlusion pressure (PAOP).

Answer 42

* raised aortic pressure * aortic valve resistance (aortic stenosis) * ventricular cavity size; increased ventricular volume; requires greater tension to contract (Laplace’s law) * raised systemic vascular resistance (SVR), e.g. shock

Answer 43

Amount of substance taken up by an organ per unit time is equal to the blood flow multiplied by the difference in concentration of that substance between arterial and mixed venous blood.

Answer 44

Systolic pressure increases when there is an increase in: * stroke volume * ejection velocity (without an increase in stroke volume) * diastolic pressure of the preceding pulse * arterial rigidity (arteriosclerosis). Diastolic pressure increases when there is an increase in: * total peripheral resistance * arterial compliance (distensibility) * heart rate.

Answer 45

If disparity between right and left ventricles Right infarction PE LV disease

Answer 46

Estimates LA pressure Can estimate CO from catheter

Answer 47

* irregular pulse: atrial fibrillation * venous pulsation (tricuspid incompetence) * hypotension * vasoconstriction * abnormal Hb (carboxy-), and methaemoglobin * bilirubin * methylene blue dye

Answer 48

B effects only Vasodilation in skeletal muscle- reduce SVR Tachycardia Use in HB while awaiting pacemaker

Answer 49

B1 and 2 Increased HR and contraction Mild vasodilation Cariogenic shock- with low dose dopamine

Answer 50

Low dose- dilates renal, cerebral, coronary, splanchnic - via D1+2 and B1 increases contractility and HR High dose- a-vasoconstriciton

Answer 51

B2 and D mild-Inotrope, chronotrope Peripheral vasodilator

Answer 52

Decrease the rate of breakdown of cAMP by phosphodiesterase III. Increased contractility with reduced PAOP and SVR

Answer 53

Myenteric (auer) lies between circular and longitudinal - motor Meissner- submucosa- sensory

Answer 54

Symp- vasoconstriction Inhibit glandular secretion Contract sphincters Inhibits muscle- motility

Answer 55

Parotid- watery- amylase and IgA Submandibular- 70%, mucous Sublingual- mucoproteins 5%

Answer 56

Isotonic fluid secreted by acinar component As moves along duct- NaCl removed K HCO3 added During high rates of secretion- Na Cl HCO3 more concentrated

Answer 57

the right crus of the diaphragm compresses the oesophagus as it passes through the oesophageal hiatus * the acute angle at which the oesophagus enters the stomach acts as a valve * mucosal folds in the lower oesophagus act as a valve * closure of the sphincter is under vagal control- physiological sphincter

Answer 58

fundus and body: peptic and parietal cells predominate * antrum and pylorus: parietal cells are less common; mucus and neuroendocrine (secreting gastrin) cells predominate * cardia: gastric glands are composed almost completely of mucus cell

Answer 59

H+ ions are pumped from the cell by the H+/K+ ATPase system. * Cl− ions are pumped from the cell by two routes: one is a chloride channel, the other is a Cl−/K+ co-transport system (K+ is thus cycled into the cell via the H+/K+ ATPase system and out via the Cl−/K+ system).

Answer 60

Mucus secretion barrier over gastric epithelium Alkaline Tight epithelial junctions prostaglandin E secretion has a protective role by increasing the thickness of the mucus layer, stimulating HCO3− production and increasing blood flow in the mucosa (bringing nutrients to any damaged areas).

Answer 61

Cepahlic- 30%- sight and smell VIa- Ach from Vagus Gastrin from G cells Histamine from mast cells- stimulate H2 Gastric- 60%- food entering Ach Intestinal- presence in duodenum-5% Releases Gastrin

Answer 62

* the secretion of gastrin is inhibited when the pH falls to around 2–3 * somatostatin secreted from neuroendocrine cells (D-cells) inhibits gastrin secretion * secretin from the duodenal mucosa is released in response to acid in the duodenum; it inhibits gastrin release * fatty food in the duodenum leads to the release of CCK and GIP; both inhibit gastrin secretion.

Answer 63

-gastric volume:↑volume then more rapid emptying * fatty food: CCK and GIP are released by the small intestine in response to fatty foods; they increase contractility of the pyloric sphincter * proteins: proteins and amino acids stimulate gastrin release; gastrin increases contractility of the pyloric sphincter * acid: acid entering the duodenum results in a vagally mediated delay in gastric emptying and also leads to secretin release. Secretin inhibits antral contractions and increases contractility in the pyloric sphincter. Secretin also stimulates HCO3− release from the pancreas to neutralize the acid * hypertonic chyme: delays gastric emptying.

Answer 64

H2 receptors- cimetidine- block H2 on parietal PPI- block H/K Activated in acidic pH

Answer 65

* sucralfate: formed from sulphated sucrose and aluminium hydroxide, it polymerizes at pH < 4 to form a sticky layer that adheres to the base of the ulcer * bismuth chelate: acts in a similar manner to sucralfate; in addition it has been shown to eradicate Helicobacter pylori * misoprostol: a synthetic analogue of prostaglandin E2. This prostaglandin is thought to protect gastric mucosa by stimulating the secretion of mucus and bicarbonate, and increasing the mucosal blood flow.

Answer 66

* sodium bicarbonate * magnesium hydroxide and magnesium trisilicate * aluminium hydroxide.

Answer 67

Iron- wrong state for absorption B12 Billious vomittng Dumping Diarrhoea Infection- reduced ability to destroy bacteria Carcinoma

Answer 68

* Reduced gastric acid secretion. * Delayed gastric emptying. * Failure of the pylorus to relax prior to gastric peristaltic wave. * Reduced pancreatic exocrine secretions. * Diarrhoea secondary to loss of vagal control of the small bowel. * Increased risk of large bowel cancer due to excessive bile salts reaching the colon.

Answer 69

* undifferentiated cells that constantly replace enterocytes * Goblet * Paneth * D-cells: produce somatostatin * S-cells: produce secretin * N-cells: produce neurotensin * Enterochromaffin cells: produce 5-hydroxytryptamine.- serotonin

Answer 70

Only in duodenum Secrete bicarbonate rich mucus

Answer 71

* disaccharidases: maltase, sucrase * peptidases * phosphatases * enteropeptidase or enterokinase (activates pancreatic trypsinogen) * lactase (under 4 years).

Answer 72

Glucose and galactose via Na dependent Fructose independent

Answer 73

Coated in bile salts in duodenum - smaller droplets Lipases- monoglycerides and FFA These combine with bile salts to form micelles Diffused into enterocyte- bile salts stay in lumen SER- reforms Triglycerides- formed into chylomicrons- diffuse into lacteals - then return to venous

Answer 74

C- by Na dependent in jejunum B12- IF- ileum Remaining B diffuse freely ADEK- micelles

Answer 75

Duodenum and jejenum in Fe2+ not 3+ Gastric acid responsible for converting Absorbed by transferrin Into by endocytosis then to plasma

Answer 76

Segmentation- circular muscle- circular movement of chyme Peristalsis- propulsion triggered by distention- longitundinal muse MMC- contraction across full length of small bowel, lasts several hours- move remaining food to colon

Answer 77

* ileogastric reflex: distension of the ileum decreases gastric motility * gastroileal reflex: increase in gastric secretion or contractility increases ileal motility.

Answer 78

Ulceration of small bowel- no Brunner gland Malasorption- Fe, Ca, P Dumping

Answer 79

Decreased Bile salt reabsorption- more gallstones Bile salts in colon- malignancy B12 def reduced water reabs- diarrhoea

Answer 80

Epithelial cells- HCO3 secreted in exchange for Cl Na K exchanged for H formed by carbonic anhydrase

Answer 81

Enterokinase- secreted by duodenum

Answer 82

Activates other enzymes * chymotrypsinogen: chymotrypsin (cleaves peptide bonds) * proelastase: elastase (cleaves peptide bonds) * trypsinogen: trypsin (cleaves peptide bonds) * procarboxypeptidase: carboxypeptidase (cleaves peptides at the C-terminus).

Answer 83

starch digestion; it splits α-1,4-glycosidic bond

Answer 84

Tyson actviates Lipase- TG- to FFA and glycerol Co lipase- binds lipase to lipids Phospolipase- FFA from PL Cholesterol esterase

Answer 85

Cephalic- vagal Gastric- vagal Intestinal- CCK and secretin CCk- release of fluid rich in enzymes from acing cells Secretin- bicarb rich Lipid and peptides- increase CCK Acid- secretin

Answer 86

>90% of secreted bile is absorbed in distal ileum

Answer 87

gluconeogenesis- produce glucose form amino acids Synthesises albumin, clotting factors Handles degradation products such as ammonia- converted to urea

Answer 88

Glucose is converted to FFAs; this is then transported to adipose tissue. It is then combined with glycerol and stored as triglycerides. During starvation these stores are released, providing fatty acids (provides energy as ATP for gluconeogenesis) and glycerol (acts as a non-carbohydrate substrate for gluconeogenesis) * synthesizes lipoproteins and cholesterol

Answer 89

* peptide hormones: insulin, Anti-Diuretic Hormone (ADH), growth hormone * steroid hormones: testosterone, oestrogen, adrenal cortex hormones * catecholamines * drugs * toxins. Via-1- increasing water solubility via p450 2- reducing biological activity

Answer 90

Iron Copper Vit ADEK, B12 Glycogen Fats

Answer 91

Kupffer cells

Answer 92

* no bilirubin in the urine (unconjugated bilirubin is not water-soluble) * ↑urobilinogen in the urine (as a result of more bilirubin being broken down in the intestine) * reticulocytosis: in response to the need to replace destroyed blood cells * anaemia * ↑lactate dehydrogenase (LDH) * ↓haptoglobin: protein that binds free haemoglobin and transfers it to the liver.

Answer 93

unconjugated hyperbilirubinaemia: * Gilbert’s syndrome: due to an abnormality in bilirubin uptake * Crigler–Najjar syndrome: due to the absence of glucuronyl-transferase conjugated hyperbilirubinaemia: * Dubin–Johnson and Rotor’s syndrome: defects in the handling of bilirubin.

Answer 94

* liver enzymes, i.e. ↑ aspartate amino transferase (AST) and ↑ alanine amino transferase (ALT); this reflects liver damage and thus release of these enzymes from hepatocytes * ↑alkaline phosphatase: reflects the partial cholestasis * abnormal clotting tests reflect the impaired hepatocyte function.

Answer 95

* bilirubin in the urine (characteristic dark colouration); this occurs as the bilirubin is conjugated and thus water-soluble * no urobilinogen in the urine; due to the obstruction, no bilirubin enters the bowel to be converted to urobilinogen * ↑canalicular enzymes: alkaline phosphatase and γ-Glutamyl Transferase (GT) * ↑liver enzymes ALT and AST;

Answer 96

Sphincter of oddi CCK- gallbladder to contract, reduce tone of oddi and pancreatic secretions CCK release stimulated bu fats and acid in duodenum Small amount of contraction due to vagus

Answer 97

Na absorbed Causing water absorption

Answer 98

Fermentation of indigestible carbs- producing fatty acids used by mucosa Degredation fo blurbing to uro and sterco Synthesis of vit K, B12, thiamin and riboflavin

Answer 99

Released in response to glucose and dat in ileum and colon Inhibits gastric and small bowel motility

Answer 100

Copper- Synthesis of Hb and coenzyme in electron transport chain Zinc- cofactor, synthesis of RNA, DNA

Answer 101

A- night blindness D- rickets, osteomalacia E- haemorrhage anaemia K- clotting B1-thiamine- beriberi 2- riboflavin- dermatitis 3- pellagra- dermatitis, diarrhoea, dementia 6- convulsions, anaemia, skin lesions- pyridoxine 9- folate- anaemia B12- cobalamin- anaemia C- scurvy

Answer 102

Renal artery- branches to interlobar artery between pyramids- form acuate- form interlobular - form afferent arterioles Efferent arterioles -either form peritubular capillaries to renal tubules Or descend as vasa recta- to medulla

Answer 103

Systolic <80

Answer 104

Prostaglandin NO

Answer 105

Angiotenin 1+2 Noradrenaline Adrenaline

Answer 106

Ednothelium- fenestrated Glycoproteins negative charge in BM- greater permeability of positive/neutral more than negative Podocytes- do not form continuous layer

Answer 107

Hydrostatic pressure- greater than normal capillaries of 50mmg Since proteins not filtered- opposing osmotic pressure of 10 Net 40

Answer 108

PCT as many ATP dependent pumps

Answer 109

NaCl and water But due to high osmolality surrounding- water moves out

Answer 110

JXG cells- specialised smooth muscle cells in afferent arteriole- secrete renin - responds to decrease afferent pressure, stimulation by sympathetic nerves and macula densa Macula densa- DCT- responded to reduction of Na

Answer 111

Actively absorbed in PCT Remaining in DCT Regulation by PTH in DCT

Answer 112

Majority of HCO3 absorbed in PCT HCO3 +H is formed in tubular epithelium by CA after absorption of H2O and CO2 HCO3 absorbed and H+ secreted into lumen

Answer 113

Waste product not actively reabsorbed But as water moves out- conc increases so small is passively reabsorbed

Answer 114

* must be filtered by the glomerulus * must not be reabsorbed * must not be secreted * must not be metabolized

Answer 115

Para- sacral outflow S2-4- innervate bladder, internal sphincter. Also run in pudendal nerve and control external sphincter Symp- L1-2 -hypogastric plexus - inhibit detrusor and increase contraction of internal

Answer 116

Reflex/autonomous Bladder – Spinal Cord Transection Above T12 In this case, the afferent signals from the bladder wall are unable to reach the brain, and the patient will have no awareness of bladder filling. There is also no descending control over the external urethral sphincter, and it is constantly relaxed. There is a functioning spinal reflex-the bladder automatically empties as it fills – known as the reflex bladder. Flaccid/atonic Bladder – Spinal Cord Transection Below T12 A spinal cord transection at this level will have damaged the parasympathetic outflow to the bladder. The detrusor muscle will be paralysed, unable to contract. The spinal reflex does not function. In this scenario, the bladder will fill uncontrollably, becoming abnormally distended until overflow incontinence occurs.

Answer 117

Forebrain Floor of third ventricle

Answer 118

Anterior- ectoderm in oral cavity - linked to hypothalamus via hypophyseal portal system Posterior- continuous with hypothalamus

Answer 119

* tumours, e.g. lung, pancreas, lymphomas * TB * lung abscess * CNS lesions, e.g. meningitis, abscess, head injury * metabolic, e.g. alcohol withdrawal * drugs, e.g. carbamazepine.

Answer 120

* active pumping of iodide ions in from the extracellular space to the follicular epithelium * iodide ions enter the colloid and are converted to iodine by TPO * iodine is combined with tyrosine. * Two forms are produced: monoiodotyrosine (1 MT) and diiodotyrosine (2 DT); these then combine to form the two thyroid hormones: * triiodothyronine (T3): MT + DT * thyroxine (T4): × 2 DT. * More T4 is produced but T3 is more biologically active. * Thyroid hormones are stored in the colloid of the follicle and released into the circulation as needed (the thyroglobulin is detached).

Answer 121

T3 and T4 cross the cell membrane via diffusion; most of the T4 is converted to T3 in the cell. * Thyroid hormone then bonds to nuclear receptors and initiates increased DNA transcription and protein production.

Answer 122

Competitively inhibit TPO Block coupling of iodotyrosine PTU_ inhibits deionisation fo T4

Answer 123

Metabolic- increased Increased catabolism of FA and protein Increased absorption of glucose Increase HR, PVR, CO Increased GI motility

Answer 124

Very rare Pituitary tumour Metastatic thyroid- well differentiated Choriocarcinoma- usually HCG but can produce susbstances similar to TSH Ovarian teratoma

Answer 125

TSH and T3/4 can both be abnormally low

Answer 126

* congenital, e.g. DiGeorge syndrome * autoimmune * iatrogenic: following total thyroidectomy or parathyroidectomy * hypomagnesaemia: low magnesium levels prevent the release of PTH.

Answer 127

* dietary insufficiency: particularly common in vegans * lack of sunlight: common in elderly patients and Asian women * malabsorption: particularly after gastric surgery, coeliac disease and disorders of bile salt production * renal disease: leads to inadequate conversion to the active form 1,25-dihydroxycholecalciferol * hepatic failure * Vitamin-D-resistant rickets: a familial condition with hypophosphataemia, phosphaturia and rickets.

Answer 128

* confusion * convulsions * muscle weakness: acute hypophosphataemia can lead to significant diaphragmatic weakness and delay weaning from a ventilator in patients in the intensive treatment unit * left shift of oxyhaemoglobin curve: this results in decreased oxygen delivery to tissues and is due to the reduction in 2,3-DPG.

Answer 129

Nerve fibres from the splanchnic nerves innervate the medulla; these release acetylcholine, which stimulates hormone release. - pre ganglionic - Ach * The chromaffin cells release a variety of hormones when stimulated to do so; they are stored in granules and exit the cells into the circulation via exocytosis. * The adrenal medulla produces: * epinephrine (adrenaline)- made from tyrosine * norepinephrine (noradrenaline) * dopamine * β-hydroxylase (enzyme involved in catecholamine synthesis) * ATP * opioid peptides (metenkephalin and leuenkephalin).

Answer 130

Cholesterol is converted to pregnenolone in mitochondria Can go to progesterone- corticosterone- aldosterone Or to progesteroneto 17a progesterone- cortisol Or 17progester to Testosterone via 20 then to- oestradiol

Answer 131

Transcortin 75% Albumin 15% Rest active or free

Answer 132

ACTH Circadian rhymth- highest in the morning * stress * trauma * burns * infection * exercise * hypoglycaemia.

Answer 133

Metabolic- opposite to insulin- breakdown of protein, converted to glucose- stored as glycogen Lipolysis Euphoria Anti-inflammatory - synthesis of lipocortin- inhibits phospholipase A2

Answer 134

* renal artery stenosis * congestive cardiac failure * cirrhosis.

Answer 135

* Na+ and water retention, leading to ↑ blood pressure * renal K+ loss, leading to hypokalaemia * renal H+ loss, leading to metabolic alkalosis.

Answer 136

The commonest defect affects the enzyme 21-hydroxylase. decrease in cortisol secretion and as a result increases in ACTH secretion; this has the effect of driving the unused cortisol precursors into the androgenic hormone synthetic pathways. * The clinical effects depend on the sex of the affected individual: * male: there is rapid growth in childhood and early sexual development (precocious puberty); due to early fusion of the epiphysis, these patients are often shorter than average * female: there is masculinization of the external genitalia with hypertrophy of the clitoris, a male body shape and hair distribution.

Answer 137

Gigantism- childhood- before epiphyseal fusion Acromegaly- after

Answer 138

* ↑glycogenolysis * ↓glucose uptake by cells * promotes amino acid uptake into cells * promotes protein synthesis * ↑lipolysis and release of free fatty acids (FFAs) * ↓LDL cholesterol.

Answer 139

Prominent supra orbital ridges Visual defects Broad nose Heart failure High BP Galactohoea Carpal tunnel

Answer 140

Anabolic hormones Promotes glucose uptake - except brain Glycogen storage Amino acid uptake Protein synthesis Inhibits lipolysis Stimulates lipogenesis

Answer 141

* ↑ plasma glucose * ↑ plasma amino acids * ↑ plasma glycerol.

Answer 142

Catabolic hormones Increase glycogenolysis Gluconeogenesis Lipase- to increase FFA and glycerol

Answer 143

* inhibits the release of insulin and glucagons * ↓ gastrointestinal motility, secretion and absorption.

Answer 144

GC-hypo- anti insulin Promote lipolysis, gluconeo, glycogen GH- fasting Anti inuslin Promote lipolysis, glucogenolysis TH- low conc- anabolic High- catabolic- hyperglycaemia Catecholamines- when hypo Glycogenolysis Lipolysis

Answer 145

pancreatic disease: * pancreatitis * pancreatic cancer * pancreatectomy * cystic fibrosis antagonists to insulin: * acromegaly (GH) * Cushing’s syndrome (glucocorticoids) * hyperthyroidism (thyroid hormone) * phaeochromocytoma (catecholamines) * glucagonoma (glucagon) * drugs, e.g. corticosteroids, thiazide diuretics * liver disease * genetic syndromes, e.g. Down’s syndrome, Friedreich’s ataxia * insulin receptor abnormalities, e.g. congenital lipodystrophy

Answer 146

Insulinoma- B cell- whiles triad - 10% malignant Gastrinoma- G cells- Malignant >50% VIPoma- watery diarrhoea, low K, achlorhydria Glucagonoma- a cell- 75% malignant- secondary diabetes mellitus; other symptoms include anaemia, weight loss and a characteristic rash called necrolytic migratory erythema Somatostatinoma- d cells- diabetes, cholethiasis, steatorrhoea

Answer 147

divided into two phases: the ebb phase and the flow phase: * the ebb phase is the initial response to injury and is a phase of reduced energy expenditure and metabolic rate that lasts for approximately 24 h * the flow phase follows: this is a catabolic phase with increased metabolic rate, hyperglycaemia, negative nitrogen balance and increased O2 consumption. The flow phase has significant effects on the metabolism of carbohydrates, lipids and proteins: * carbohydrates: hyperglycaemia- this is stimulated by catecholamines and glucocorticoids (insulin resistance prevents cell uptake). After 24 h the glycogen is exhausted and the hyperglycaemia is maintained by gluconeogenesis * lipids: lipolysis is stimulated by catecholamines, the sympathetic nervous system, cortisol and growth hormone. * proteins: the demand for amino acids is met by skeletal muscle breakdown; the greater the insult, the greater the breakdown and nitrogen loss. The amino acids are used in gluconeogenesis and synthesis of acute phase proteins.

Answer 148

-hypovolaemia: this type of fluid loss is referred to as ‘third space’ loss; the vasodilatation and increased vascular permeability lead to fluid being sequestered in the interstitial space * renal changes: following injury there is reduced excretion of free water and sodium; this continues for about 24 h and is due to the release of aldosterone and ADH * fever: injury (even in the absence of infection) is associated with a rise in temperature; this is due to changes in the thermoregulatory set point in the hypothalamus by IL-1 * haematological changes: there is a leukocytosis; albumin levels fall due to decreased production and loss into injured tissue. The coagulation system is activated. This is primarily to reduce bleeding after the injury; however, it leads to a state of hypercoagulability and an increased risk of deep vein thrombosis (DVT) * electrolyte and acid–base changes: the electrolyte changes include ↓Na+ (due to dilution from retained water), ↑K+ (as a result of cell death and tissue injury), metabolic alkalosis (the absorption of Na+ stimulated by aldosterone leads to K+ and H+ excretion) and metabolic acidosis (this occurs with more severe injuries with hypotension, poor perfusion and consequent anaerobic metabolism). -hyperglycaemia, lipolysis, ketones - form sympathetic innervation - increased resp drive - resp alkalosis - CO increases

Answer 149

Low in ebb phase Increase in flow phase- but hyperglycaemia due to resistance

Answer 150

Astrocytes- form BBB Microglia- phagocytose Oligodendrolgia- myelin in CNS

Answer 151

Occurs between 60-160mmHg Myogenic - When the blood pressure rises, the vessels constrict, thus decreasing flow; when the blood pressure falls, the cerebral vessels dilate in order to increase flow. Metabolic- increased activity results in a decrease in PaO2 and increase in PaCO2 and H+, the changes resulting in local vasodilatation of cerebral blood vessels and thus increased perfusion. Neural- some sympathetic vasoconstrictor and parasympathetic vasodilator innervation, but their effect is very weak Local- Increases in PaCO2 are associated with an increase in CBF due to marked cerebral vasodilatation; however, just as hypercapnia results in vasodilatation, then a fall in PaCO2 (hypocapnia) results in cerebral vasoconstriction. The effect of changes in PaO2 is not as marked; hypoxia has a significant effect only when it falls below 8 kPa. Increases in PaO2 can cause mild cerebral vasoconstriction; indeed hyperbaric oxygen therapy can reduce CBF by 20–30%.

Answer 152

DBP+1/3(systolic-diastolic) -ICP

Answer 153

Hydraulic cushion Stable ionic environment

Answer 154

Arachnoid villi- which drain into venous sinuses

Answer 155

Lipid soluble molecules can pass freely Rather than the freely permeable fenestrated capillaries found in other tissues, the cerebral capillaries have very tight cell-to-cell junctions in the endothelium. In addition, the end-feet of astrocytes cover the basement membrane. the endothelium contains transport proteins (carriers) for nutrients such as sugars and amino acids * certain proteins, e.g. insulin and albumin, may be transported by endocytosis and transcytosis

Answer 156

third and fourth ventricles: allow drugs and noxious chemicals to trigger the chemoreceptor area in the floor of the fourth ventricle; this in turn triggers the vomiting centre. In addition angiotensin II passes to the vasomotor centre in this region to increase sympathetic outflow and causes vasoconstriction of peripheral vessels * posterior lobe of pituitary: allows the release of oxytocin and antidiuretic hormone (ADH) into the circulation * hypothalamus: this allows the release of releasing or inhibitory hormones into the portal–hypophyseal tract.

Answer 157

7 areas- all must be absent 1. No pupillary response to light, direct or consensual: this reflex involves cranial nerves II and III. 2. Absent corneal reflex – normally would result in blinking; this reflex involves cranial nerves V and VII. 3. No motor response in the cranial nerve distribution to stimuli in any somatic area, e.g. supraorbital or nailbed pressure leading to a grimace. 4. No gag reflex: back of the throat is stimulated with a catheter; this reflex tests cranial nerves IX and X. 5. No cough reflex: no response to bronchial stimulation with a suction catheter; this reflex tests cranial nerves IX and X. 6. No vestibulo-ocular reflex: head is flexed to 30° and 50 mL of ice-cold water is injected over 1 min into each external auditory meatus; there should be no eye movements; this reflex tests cranial nerves III, VI and VIII. 7. Apnoea test: the patient is preoxygenated with 100% O2 for 10 min; PaCO2 is allowed to rise to 5 kPa (before testing); the patient is disconnected from the ventilator and O2 is insufflated at 6 L/min; PaCO2 is allowed to rise to 6.5 kPa; there should be NO respiratory effort.

Answer 158

Raised ICP Incracranial shift and herniation Hydrocephalus- as will interrupt CSF flow

Answer 159

* transtentorial: the lesion lies within one hemisphere; leads to herniation of the medial part of the temporal lobe over the tentorium cerebelli (uncal) * tonsillar: caused by a lesion in the posterior fossa; the lowest part of the cerebellum pushes down into the foramen magnum and compresses the medulla * subfalcial: caused by a lesion in one hemisphere; leads to the herniation of the cingulate gyrus under the falx cerebri * diencephalic: generalized brain swelling; leads to the midbrain herniating through the tentorium; this is termed coning

Answer 160

* Cushing’s response: ↓ respiratory rate, bradycardia and hypertension * neurogenic pulmonary oedema * Cushing’s ulcers * preterminal events include bilateral pupil constriction followed by dilation, tachycardia, ↓ respiratory rate, and hypotension. * headache * nausea and vomiting * papilloedema * decreased conscious level.

Answer 161

* oculomotor nerve compression: ipsilateral pupil dilation (transtentorial) * cerebral peduncles: contralateral hemiparesis (transtentorial) * posterior cerebral artery: cortical blindness (transtentorial) * cerebral aqueduct: hydrocephalus (transtentorial)

Answer 162

Tonsillar All can cause compression of midbrain resulting in death

Answer 163

The Na+ channel activates much faster than the K+ channel. This explains the rapid influx of Na+; the channel also closes much faster; the K+ channel remains open over a longer period than the Na+ channel and is responsible for repolarization as K+ is released and the membrane potential falls back to its negative value.

Answer 164

Resting -70mv Depolarised- +50

Answer 165

Axon diameter Myelination

Answer 166

Nodes of Ranvier Causes AP to jump- saltatory conduction

Answer 167

Aα Motor proprioception 100m/s 15–20um Aβ Touch and pressure 50 5–10 Aγ Muscle spindles 30 3–6 Aδ Pain, temperature and touch 20 2–5 B Autonomic 10 3 C Pain 1 0.5–1

Answer 168

* the action potential depolarizes the presynaptic membrane by opening voltage-gated Ca2+ channels * Ca2+ enters the axon down an electrochemical and concentration gradient * the increase in Ca2+ results in the vesicles fusing with the presynaptic membrane and releasing neurotransmitters into the synaptic cleft * the neurotransmitters then bind with receptors on the post-synaptic membrane * binding of neurotransmitters initiates secondary signals within the cell and opens ion channels, thus generating a depolarizing current * the transmitter is released from the receptor and is broken down by specific breakdown pathways.

Answer 169

Ach- excitatory - broken down to acetate and choline by acetylcholinesterase * amines: this group includes catecholamines (adrenaline, noradrenaline, and dopamine), 5-hydroxytryptamine (serotonin) and histamine. The catecholamines are formed from the amino acid tyrosine. Two enzymes degrade catecholamines: monoamine oxidase breaks down transmitter taken up by the presynaptic neuron; and catechol-O-methyl transferase breaks down catecholamines taken up by the postsynaptic neuron Amino acids: several amino acids act as neurotransmitters; these include: * glycine: inhibitory * glutamate: excitatory or inhibitory (can be converted to GABA) * aspartate: excitatory Peptides: examples of peptide transmitters include: * substance P: involved in the transmission of pain sensation * endorphins: inhibit pain pathways

Answer 170

* Aδ fibres: these are myelinated nerves; as a result, they have a high conduction speed and diameter. They are responsible for the sharp initial pain * C fibres: these are unmyelinated nerves and thus have a smaller diameter and lower conduction velocity. They are responsible for the longer-lasting dull pain. here they synapse in lamina I and III in the dorsal horn.

Answer 171

Transduction- involves the production of electrical impulses; following tissue damage there is the release of inflammatory substances, i.e. prostaglandins, histamine, serotonin, bradykinin and substance P. Transmission- pain sensation is along Aδ and C fibres to the spinal cord; here they synapse in lamina I and III in the dorsal horn. Modulation of pain involves the ‘gate control theory’- These include inhibitory inputs from the periaqueductal grey matter and nucleus raphe magnus (both releasing serotonin) and the locus coeruleus (releases noradrenaline). In addition there is the release of the naturally occurring enkephalins and endorphins.

Answer 172

Pre- found in- in the thoracic and upper 2–3 lumbar segments of the spinal cord * preganglionic neurons lie in the lateral horn of the spinal grey matter * preganglionic axons leave via the ventral root of the spine to join the spinal nerve * post-ganglionic neurons have their cell bodies either in the sympathetic chain or in a named plexus along the aorta, i.e. coeliac, superior and inferior mesenteric. * Spinal nerves are connected to the sympathetic chain by two small branches: the lateral white ramus communicantes (myelinated), and the medial grey ramus communicantes (unmyelinated). * The sympathetic innervation of the head and neck is via preganglionic neurons synapsing with post-ganglionic bodies within the sympathetic chain; the post-ganglionic neurons then leave via the grey rami communicantes to join the spinal nerve.

Answer 173

* The sympathetic innervation of the abdominal and pelvic organs differs from that of the head and neck. Preganglionic neurons pass straight through the sympathetic chain to their individual plexuses and synapse with post-ganglionic cell bodies within the plexus.

Answer 174

- Pre are Ach * The neurotransmitter of the sympathetic nervous system is noradrenaline (except sweat glands; these are innervated by cholinergic fibres).

Answer 175

PNS pre ganglion longer Cell bodies of post ganglion- lie closer to organ

Answer 176

* the dark bands or A bands are composed of the thicker myosin filaments * the light bands or I bands are composed of the thinner actin filaments * the I band is divided by the Z line; the space between Z lines is called a sarcomere * at the Z lines the membrane of the muscle cell (sarcolemma) forms narrow tubes that traverse the sarcomere; these are called the T-tubules

Answer 177

* actin: a thin contractile protein, arranged in a double-stranded helix * tropomyosin: lies in the groove between the actin filaments * troponin: lies at regular intervals along the filament, attached to both actin and tropomyosin; it also has binding sites for Ca2+ and is involved in the regulation of contraction. Troponin and tropomyosin block the myosin-binding site on actin.

Answer 178

* type I or slow twitch: act as postural muscles, e.g. in the back; they are designed to perform slow, sustained contractions and resist fatigue well. They rely on aerobic metabolism and contain myoglobin * type II or fast twitch: * type IIa or fast oxidative fibres, e.g. calf muscles: they rely on aerobic metabolism and contain myoglobin; they have moderate resistance to fatigue * type IIb or fast glycolytic fibres, e.g. extraocular muscle: do not contain myoglobin and thus appear white; they contain a large amount of glycogen and rely on anaerobic metabolism.

Answer 179

* When ATP binds to the head section of myosin it dissociates from its binding site on the actin filament. * The ATP is hydrolysed (by ATPase on head) and changes the angle of the myosin head (relative to its tail); as the ATP has been hydrolysed, the myosin is again able to bind to the actin filament. * The release of phosphate from the myosin head restores the angle and moves the actin filament along the myosin filament; this is called the power stroke. * ATP will bind to myosin and start the process again. * Creatine phosphate is present in very high concentrations within muscle and provides sufficient energy reserves for the above processes to take place. The enzyme creatine kinase catalyses the transfer of the phosphate group from creatine phosphate to ADP, thus replenishing ATP stores.

Answer 180

Depolarization of the cell leads to the release of Ca2+ from the sarcoplasmic reticulum within the cell. The rise in Ca2+ activates contraction by binding to troponin on the thin filaments; this leads to a conformational change and removes troponin and tropomyosin from the myosin binding site on actin. * As the cell repolarizes, the Ca2+ is actively pumped back into the sarcoplasmic reticulum. * The Ca2+ is removed from the troponin and thus the troponin and tropomyosin block the myosin binding site.

Answer 181

* muscle spindle is stretched: this causes the receptor region to depolarize; this generates an action potential in the afferent nerve (Ia afferent) * the afferent impulse enters the spinal cord via the dorsal horn and synapses with an α motor neuron that supplies the stretched muscle * the action potential in the α motor neuron signals the muscle to contract to oppose the stretch * the afferent impulse also synapses with inhibitory neurons that synapse with α motor neurons that supply antagonist muscles (reciprocal inhibition). This reduces resistance to contraction of the stretched muscle.

Answer 182

After stretch Intrafusal muscle fibres stretched- 1a efferent then type 2 slower- to provide proprioception info - causing a motor to contract Gamma neurons to cause contractions of these fibres - causing stretching of mid portion that doesn't have contractility- opening stretch Na channels- increasing resting potential- increasing likelihood of AP

Answer 183

The reflex they are involved in is an inhibitory response. It involves: * afferent impulse 1b - acting on interneuron- via glutamine Interneuron via glycine acts on α motor neurons that supply the contracting muscle * reduction in the level of active contraction * the reflex is protective and limits muscle/tendon tension

Answer 184

- withdrawal to painful stimulant- detected by cutaneous afferent neuron * α motor neurons: this results in stimulation of flexors in the limb in which the painful stimulus was experienced, thus withdrawing the affected limb * inhibitory signals are passed to α motor neurons in the opposing extensor muscles * this pattern is reversed in the opposing limb: flexor muscles are inhibited and extensor muscles are stimulated; this is called the crossed extensor reflex

Answer 185

* corticobulbar tracts: supply the motor portions of the cranial nerves * corticospinal tracts: supply the spinal motor neurons; they are concerned with voluntary movements.

Answer 186

Extrapyrimidal- involuntary control 1. The rubrospinal tract: originates in the red nucleus- cross over and primarily innervates distal limb muscles.- fine control in hands 2. The tectospinal tract: fibres arise in the superior colliculus of the midbrain; it receives inputs from the visual cortex and is believed to control reflex activity in response to visual stimuli. 3. The vestibulospinal tract: originates in the vestibular nuclei; it supplies muscles of the ipsilateral side of the body. It innervates muscles concerned with balance and posture in response to inputs from the vestibular apparatus. 4. The reticulospinal tract: fibres -The medial reticulospinal tract arises from the pons. It facilitates voluntary movements, and increases muscle tone. The lateral reticulospinal tract arises from the medulla. It inhibits voluntary movements, and reduces muscle tone.

Answer 187

a1 agonsit Used for acute hypotension

Answer 188

Hepatocytes

Answer 189

Crypt of Lieberkuhn

Answer 190

Short length, large diameter, low viscosity and high pressure

Answer 191

Initial increase due to prostaglandin and vasodilators Then decrease due to vasoconstriction

Answer 192

U x V/P urine conc x urine production /plasma conc

Answer 193

a- atrial contraction just before carotid pulse x- rapid atrial filling c- ventricles begin to contract- bulge tricuspid back v- atrial filling y- opening of tricuspid

Basic Science MRCS Physiology Flashcards

(218 cards)