MRCS Part A > Physiology > Flashcards

Physiology Flashcards

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1
Q

How much does a pancreas secrete

A

Pancreatic secretions are usually 1000-1500ml per 24 hours and have a pH of 8.

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2
Q

Regulation of pancreas

A

The cephalic and gastric phases (neuronal and physical) are less important in regulating the pancreatic secretions. The effect of digested material in the small bowel stimulates CCK release and ACh which stimulate acinar and ductal cells. Of these CCK is the most potent stimulus. In the case of the ductal cells these are potently stimulated by secretin which is released by the S cells of the duodenum. This results in an increase in bicarbonate.

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3
Q

Normal ICP

A

<15mmHG

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4
Q

causes of hyponatraemia

A

carbamazepine, sulfonylureas, SSRIs, tricyclics

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5
Q

Define anatomical dead space

A

Volume of gas in the respiratory tree not involved in gaseous exchange: mouth, pharynx, trachea, bronchi up to terminal bronchioles
Measured by Fowlers method
Increased by:
Standing, increased size of person, increased lung volume and drugs causing bronchodilatation e.g. Adrenaline

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6
Q

Define Physiological dead space

A

150 mls, increases in ventilation/perfusion mismatch e.g. PE, COPD, hypotension
Volume of gas in the alveoli and anatomical dead space not involved in gaseous exchange.

Alveolar ventilation is the volume of fresh air entering the alveoli per minute.

Alveolar ventilation = minute ventilation - Dead space volume

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7
Q

Prolactin role

A

TRH stimulates it - milk production and inhibits gonadal activity
Dopamine inhibits it

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8
Q

Which part of adrenal cortex produces Cortisol?

A

Fasciculata

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9
Q

How does cardiac muscle contract

A

Cardiomycyte gets depolarised which increases calcium extracellular through T tubules which then attaches to sarcoplasmic reticulum to increase calcium further into cytoplasm. This then attaches to troponin C which uncovers the binding site for myosin head to attach. This is cross bridging to allow contraction. ATP is required for detachment.

Myocytes consist of actin and myosin filaments which is responsible for contraction. Contain myofibrils which are made up of sarcomeres.

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10
Q

Define myocytes

A
  • voltage operated ion channels
  • myofibirls made up of sarcomeres
  • sarcomeres consist of actin and myosin filaments
  • large numbers of mitochondria.
  • T-tubles and sarcoplasmic reticulum
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11
Q

Define action potential and how it works in cardio

A

Electrical signal that travels throughout the cardiac muscle to initiate contraction

Phase 0 when sodium influx happens and it goes above -70. Depolarisation occurs.

Phase 1 When it reaches 20 K channel opens and Na closes -> initial repolarisation

Phase 2 - slow replorasation where calcium channel opens and there is an influx to allow platuea and contraction of muscle. Empty during contraction.

Phase 3 - rapid repolarisation where all channels close and K leaves - heart relax o allow chambers to fill

Phase 4 resting membrane potential of ventricular muscle. SA node and onducting system are constantly depolarising

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12
Q

Role of SA + AV node

A

right atrium near the entrance of the SVC. Determines heart rate.
AV node -> AV fibrous ring on the right side of the atrial septum.

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13
Q

Define EF

A

Stroke volume/end diastolic volume

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14
Q

What is first heart sound, second, third + fourth

A

Closure of AV valves

second - closure of aortic and pulmonary

Third - rapid ventricular filling heard in children

Fourth - stiff ventricle - LVH, heart failure

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15
Q

Cardiac output define

A

CO = stroke volume x heart rate

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16
Q

Starlings law of heart

A

greater the stretch of the ventricle in diastole, greater the stroke volume

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17
Q

What affects cardiac output

Causes of increased contractility

A

stroke volume
- increased contractility
- increased Preload
- reduced Afterload

Contractility
-> increased catecholamine stimulation via B1 receptor
-> decreased beta blocker, HF w systolic dysfunction, acidosis, hypoxia/hypercapnia, calcium channel blockers

Preload -> end diastolic volume depends on venous tone and circuating blood volume. venous vasodilators GTN

Afterload - increased wall tension per Laplace’s law -> increased pressure -> increase afterload.

LV compensates for increased afterload by thickening (hypertrophy) in order to reduce wall stress.

Reduce afterload -> arterial vasodilators, ACEi and ARBs reduce, chronic HTN increase MAP leading to LV hypertrophy

Cardiac oxygen demand
increased -> increased contractility, afterload, HR, diameter of ventricle

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18
Q

Define pulse pressure

A

Systolic BP - Diastolic BP

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19
Q

MAP

A

Cardiac output x total peripherla resistance

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20
Q

cerebral blood flow

A

Factors affecting the cerebral pressure include; systemic carbon dioxide levels, CNS metabolism, CNS trauma, CNS pressure
The PaCO2 is the most potent mediator
Acidosis and hypoxaemia will increase cerebral blood flow but to a lesser degree
Intra cranial pressure may increase in patients with head injuries and this can result in impaired blood flow
Intra cerebral pressure is governed by Monroe-Kelly Doctrine which considers skull as closed box, changes in pressure are offset by loss of CSF. When this is no longer possible ICP rises

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21
Q

causes of hypokalemia with alkalosis

A

Vomiting
Diuretics
Cushing’s syndrome
Conn’s syndrome (primary hyperaldosteronism)

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22
Q

causes of hypokalaemia with acidosis

A

Diarrhoea
Renal tubular acidosis
Acetazolamide
Partially treated diabetic ketoacidosis

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23
Q

how do we assess upper airway compression

A

flow volume loop

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24
Q

composition of CSF

A

Glucose: 50-80mg/dl
Protein: 15-40 mg/dl
Red blood cells: Nil
White blood cells: 0-3 cells/ mm3

approx 150ml

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25
The role of tranexamic acid
anti fibrinolytic that competitively inhibits the conversion of plasminogen to plasmin. Plasmin degrades fibrin and therefore rendering plasmin inactive slows this process.
26
causes of normal anion gap acidosis
H - Hyperalimentation/hyperventilation A - Acetazolamide R - Renal tubular acidosis D - Diarrhoea U - Ureteral diversion P - Pancreatic fistula/parenteral saline
27
Phases of wound healing
Haemostasis - Vasospasm in adjacent vessels Platelet plug formation and generation of fibrin rich clot. Erythrocytes and platelets. Inflammation - Neutrophils migrate into wound (function impaired in diabetes). Growth factors released, including basic fibroblast growth factor and vascular endothelial growth factor. Fibroblasts replicate within the adjacent matrix and migrate into wound. Macrophages and fibroblasts couple matrix regeneration and clot substitution. Neutrophils, fibroblasts and macrophages Regeneration - Platelet derived growth factor and transformation growth factors stimulate fibroblasts and epithelial cells. Fibroblasts produce a collagen network. Angiogenesis occurs and wound resembles granulation tissue. Fibroblasts, endothelial cells, macrophages remodelling - Longest phase of the healing process and may last up to one year (or longer). During this phase fibroblasts become differentiated (myofibroblasts) and these facilitate wound contraction. Collagen fibres are remodelled. Microvessels regress leaving a pale scar. myofibroblasts.
28
Where does the trachea start
just below the cricoid upto T4-T5
29
Define Borchardts triad
epigastric pain, retching without vomiting and inability to pass NG tube
30
Where is tracheostomy inserted
second and fourth tracheal rings. 2cm incision. 2 cm above sternal notch.
31
Predominant cell types in chronic inflammation
macrophages and lymphocytes
32
what type o cells seen in parasitic infections
eosinophils
33
Process of healing intention
within 48 hours epithelialisation associated with immediate cellular reaction. proliferative phase
34
what elements needed for collagen synthesis
iron, oxygen, vitamin C, alpha ketogluterate
35
what are the elbow flexors and which nerve supplies
biceps brach, brachilaise MSK nerve brachioradialis - radial nerve
36
which cells store heparin anticoagulant
basophils + mast cells
37
monroe-kellie doctrine
1550-1700ml intracranial volume
38
example of a permanent cell
erythrocyte
39
common PTH secreting malignancies
squamous cell tumours breast kindey
40
absoprtion of calcium occurs where
duodenum or jejunum
41
what is absorbed in the jejunum
calcium, carbohydrates and amino acids
42
pulmonary artery occlusion pressure represents what
left atrium
43
Hypothermia ECG changes
J waves
44
which vessels are most sensitive to the vasodilator effect nitrates?
large veins
45
which organ has the most blood flow
kidneys
46
How long does the ST segment last for
0.08s
47
percentage of blood in weight
7%
48
how would the pulse feel in a heart transplant
tachycardia as vagus nerve is severed
49
define EF
stroke volume/end diastolic volume
50
mechanism of paget disease
Hyperplasia of osteoblasts and osteoclasts
51
in which conditions do we see granuloma in
syhphilis, crohns, TB, GPA + sarcoidosis
52
what is barrets oesophagus
stratified epithelium to simple columnar epithelium
53
most common complication after doing a FNA of lung
pneumothorax
54
55
which IV med used in bier block
prilocaine
56
which organisms can cause rarely AAA
salmonella/staph aureus
57
which skin structure acts as slowly adapting receptor
merkels
58
parasympathetic fibres
3,7,9,10 2,3,4th sacral segments of the spinal cord.
59
How to assess pancreas exocrine function
lundh meal
60
commonest location anal fissure
distal posterior
61
When else can CEA be raised
smokers UC pancreatitis cirrhosis
62
Vitamin A is necessary to maintain epithelia in the respiratory tract and squamous metaplasia can occur if there is a deficiency.
63
what process does the brain go through after stroke
liquefactive necorsis
64
Endotoxins role and triggers
ipopolysaccharides forming integral parts of the cell walls of Gram-negative bacteria. Interleukin-1 and tumour necrosis factor which are released by macrophages, mediate most of the biological effects of endotoxins.
65
cmoponents of saliva
electrolytes epithelial cells white blood cells maltase, lipase and amylase, which commence the process of digestion of dietary fats and starches respectively in the mouth. Antimicrobial agents found in saliva include IgA antibodies and lysozyme.
66
Where is fat mostly absorbed
Fat is emulsified in the proximal small intestine (duodenum and jejunum) and free fatty acids are taken up into the enterocytes, via a protein-dependent active transport, in the form of fatty acids, glycerol and mono- or di-glycerides. Once in the enterocyte they reform triglycerides and are packaged with cholesterol into chylomicrons, which are transported outside the cells. Some short chain fatty acids are transported via diffusion.q
67
commonest organisi=m for balanitis
candida
68
Terminal ileum
The terminal ileum is an important site of bile salt re-absorption as well as lipid soluble vitamins including Vitamin A, D, E and K.
69
Stomach enzymes and role
The stomach produces 1200–1500 ml of highly acidic (pH 0.9–1.2) secretions daily. Gastric juice contains many enzymes that help in the breakdown of nutrients. These include proteolytic enzymes (pepsin, rennin), gastric lipase, gelatinase, gastric amylase and urease. Their action is as below: pepsinogen secreted in the gastric juice is activated to pepsin by hydrochloric acid. Pepsin breaks down proteins into peptones, polypeptides and proteoses. It also causes curdling of milk protein casein gastric lipase has a weaker lipolytic action in comparison to pancreatic lipase. It digests tributyrin or butterfat into fatty acid and glycerol. The optimum pH for its action is between 4 and 5 and it becomes inactive at pH < 2.5 gelatinase breaks down gelatin type I and V and collagen type IV and V contained in consumed meat into peptides. Rennin promotes curdling of milk. Gastric amylase helps in the digestion of starch. Urease acts on urea to produce ammonia.
70
Pnacreas
trypsin and chymotrypsin -> most powerful proteolytic enzyme and converts proteins into proteoses and polypeptides trypsinogen is normally activated after it reaches the duodenum
71
small intestine role
6m in lenght mucosa, submucosa, muscular layer (inner circular, outer longitudinal) and serosa (peritoneal layer). villi are about 1 mm tall and are lined by columnar cells or enterocytes. argentaffin cells or enterochromaffin cells – secrete serotonin that stimulates peristaltic activity goblet cells – secrete mucin and create a protective mucus layer paneth cells – secrete cytokines called defensins; these peptides have antimicrobial properties. brunner’s glands – mucus-secreting glands present in the first part of the duodenum. They are deeper than the common mucosal glands, as they penetrate the muscularis mucosa to reach the submucosal layer. CCK is synthesised in the I cells
72
Role of CCK
it inhibits gastric emptying by reducing gastric motility and increasing the tone of the pyloric sphincter it stimulates secretion of pancreatic enzymes it promotes gall bladder emptying by stimulating contraction of the gallbladder wall and simultaneous relaxation of the sphincter of Oddi. This occurs in response to the presence of fats in the duodenum induces satiety and reduces food consumption through vagal afferents and direct central action via CCK receptors in the brain it stimulates somatostatin and pancreatic polypeptide release.
73
What is the primary site of insulin production in the pancreas?
tail of pancreas beta cells
74
How does TXA work
binding to lysine binding sites on plasminogen, which prevents plasminogen from binding to fibrin. This inhibits the conversion of plasminogen to plasmin, a molecule responsible for breaking down fibrin clots. By preventing fibrinolysis, TXA helps in stabilising blood clots and reducing bleeding. This mechanism is particularly useful in trauma and surgical patients where excessive bleeding is a concern.
75
Where is the site of magnesium storage in the body?
BONE
76
Management of keloid
-> Occlusive dressings, compression therapy and steroids are among the first-line treatments for keloids and hypertrophic scarring. -> Occlusive dressings function by decreasing the amount of blood, oxygen and nutrients delivered to the scar. Compression therapy applies local pressure to the affected region, causing the skin to thin and the collagen fibres to become less cohesive. Steroids (intralesional triamcinolone) reduces collagen production and proinflammatory mediators.
77
clearance formula
Clearance (ml/min) is calculated using the formula (U × V)/P where U = urine concentration in mg/ml, V = urine production in ml/min, P = plasma concentration in mg/ml.
78
fluid pres children
100 mL/kg/day for the first 10 kg of weight 50 mL/kg/day for the next 10 kg of weight 20 mL/kg/day for weight over 20 kg
79
what is chronotropic v ionotropic
Chronotropic refers to the heart rate, while inotropic refers to the force of the heart's contractions
80
what does extracellular fluid have
Extracellular has higher sodium, chloride and bicarbonate levels when compared with intracellular fluid.
81
Which drug has ionotopic effect and selectiv of B1
dobutamine
82
where is iron absorbed
jejunum/duodenum
83
How to calculate to give fluids in burns
2 x weight x % of burn half of it in first 8 hours
83
What conditions can cause positive nitrogen balance and what does it mean
when you use more nitrogen to make proteins periods of growth, hypothyroidism, tissue repair and pregnancy
84
What is the primary method by which intracellular pH is regulated?
cytoplasmic proteins
85
The normal adult blood volume is approximately what percentage of the body weight?
7-8%
86
most likely to be associated with identification of Aschoff–Rokitansky sinuses?
chronic cholecystitis
87
commonest oseophageal tumor
leimyoma
88
Role of LH on testosterone
In men LH acts on the interstitial cells of the testes (Leydig cells) to secrete testosterone.
89
Role of calcitonin
Calcitonin, is a peptide hormone produced in the C-cells or parafollicular cells of the thyroid gland. The C-cells sense an increase in the concentration of calcium in the serum and then secrete calcitonin to bring about a reduction of calcium. Calcitonin inhibits the action of osteoclasts and therefore inhibits bone resorption and also inhibits the reabsorption of calcium and phosphate ions by the kidney, promoting their excretion in the urine.
90
How is T3 made in the thyroid glands
Coupling of mono-iodotyrosine (MIT) and diiodotyrosine (DIT)
91
FSH action in men
FSH stimulates testicular growth and enhances the production of an androgen-binding protein by the Sertoli cells. This androgen-binding protein causes high local concentrations of testosterone near the sperm. This high concentration is essential for the development of normal spermatogenesis. Hence, action of FSH is supportive and not antagonistic.
92
Role of ANP
ANP is released from atrial muscle cells when the atria are stretched due to increased circulating blood volume.
MRCS Part A
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