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USMLE Step 1 flashcards > Physiology > Flashcards

Physiology Flashcards

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USMLE® Step 1 flashcards
1
Q

Which are the characteristics and murmurs in aortic stenosis and regurgitation?

A
  • Aortic stenosis: Crescendo-decrescendo systolic ejection murmur (ejection click may be present)—-Syncope, Angina, and Dyspnea on exertion.
  • **calcification in older patients (> 60 years old) or in younger patients with bicuspid aortic valve.
  • Aortic regurgitation: diastolic decrescendo murmur— hyperdynamic pulse, and head bobbing when severe and chronic.
  • ** Often due to aortic root dilation, bicuspid aortic valve, endocarditis, rheumatic fever.
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2
Q

What is the colipase?

A

is a proteic cofactor necessary to pancreatic lipase activity

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3
Q

A patient that has a lung region that is underventilated but well perfused, is similar to what kind of shunt?

A

Physiologic shunt different to physyologic dead space—- not blood flow yes ventilated

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4
Q

Which is the compound that serves as a precursor of uroporphyrin? and which are the enzymes that result damaged in porphyria?

A

is succinyl coA + Glycin——– amilovulinic acid
1. Acute intermittent porphyria—– Porphobilinogen
deaminase
2. porphyria cutanea tarda—-Uroporphyrinogen
decarboxylase

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5
Q

Which symptoms and signs could you suspect a methanol poisoning? and which is the enzyme that metabolized it?

A

Exposure to paint thinner + ophtalmologic and neurologic symptoms + anion gap metabolic acidosis
—it is metabolized by formaldehyde dehydrogenase

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6
Q

Where it derives Von willebrand factor ?

A
  • from weibel palade bodies in endothelial cells

- alpha granules of platelets

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7
Q

Thrombotic thrombocytopenic purpura is due to?

A

decreased ADAMTS13 (enzyme that normally cleaves vWf multimers into monomer for eventual degradation)—–causes abnormal platelet adhesion (microthrombi)

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8
Q

which are the substances are required to coagulation factors for activation?

A
  • exposure to an activating substances: tissue thromboplastin activates factor VII (extrinsic pathway)
    subendothelial collagen activates fractor XII (intrinsic)
  • phospholipid surface of platelets
  • calcium (derived from platelets dense granules)
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9
Q

Released Ca2+ in cytoplasm of muscle cell leading to

A

Binds to troponin C, causing a conformational change that moves —-tropomyosin out of the myosin-binding groove on actin filaments = contraction.

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10
Q

Is ejection fraction equal to

A
  • stroke volume/ end diastolic volumen

- SV= end distolic volumen - end systolic volume

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11
Q

Lung recoil vs lung compliance

A

Lung recoil— rebound of the lungs after having been stetched by inhalation
Lung compliance— ability to stetch and expand

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12
Q

GFR autoregulation

A

decrease of GRF — leading to decrease the sodium to be sensed by macula densa in distal tubule—afferent arteriolar dilation and constriction of efferent arteriolar due to RAS activation.

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13
Q

The increase in systemic vascular resistance and decrease in venous capacitance are due to sympathetic stimulation of…

A

vascular sympathetic alpha 1 receptor: inadequate compensatory stimulation—- is the major cause of orthostatic hypotension.

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14
Q
  • Stroke volume

- changes in exercise

A

end dyatolic volume- end systolic volume
*In exercise EDV (preload) incresed trying to increase stretch in myocytes leading to increased contractility
and ESV decreased because peripheral vascular resistance (afterload decrease) because vasodiltation of muscles leading to heart emptying quickly

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15
Q

Incretins

A

GI hormones produced by gut mucosa —- stimulate pancreatic insulin secretion (in response to sugar cotaining meals). Independent of glucose blood level

  • Glucagon like peptide 1 (GLP-1)
  • Gastric inhibitory peptide
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16
Q

elastase

A
  • Protease

- Contained in alveolar macrophages lysosomes and azyrophilic granules of neutrophils.

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17
Q

Hyperventilation

A

Decrease PCO2— respiratory alkalosis

secondary to hypoxia for example

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18
Q

Vomiting reflex

A

the postrema area in the IV ventricle —– has a chemorecpetor trigger zone— respond to neurotransmitters, drugs and toxins.
the nucleus tractus solitarius (NTS) in medulla (receives information of area postrema, GI tract through vagus nerve, vestibular system and CNS.
Neurons of NTS projects to medulla nuclei and coordinate vomiting process

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19
Q

Five major receptors in vomiting

A
  • serotonin 5HT3
  • Neurokinin (NK1)
  • Histamine H1
  • Dopaminegic D2
  • Muscarinic M1
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20
Q

Minimal alveolar concentration MAC

A

Is the % of anesthesic in inspired gas to produce 50% of patients unresponsive to painful stimuli.
Potency is inversely related to MAC

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21
Q

What happened with in HPO4 in diabetic ketoacidosis?

A

HPo4 acts as buffer, Binds with H to form H2PO4— excreted in urine (increased)

22
Q

Sarcomere

A

overlapping filaments of myosin and actin

Single sarcomere is the distance between two Z lines

23
Q

Which is the reason for loss bone mass in menopausal women?

A

low estrogen level—– increased production of inflammatory cytokines (IL-1 and TNF Alpha) —–increased expression of the receptor activator of Nf-Kappa Beta ligand (RANK-L)—– increasing osteoclast activity

24
Q

Micturation reflex

A
  • Sacral micturation center: S2-S4—- responsible of bladder contraction
  • Pontine micturation center: in pontine reticular formatio, relaxation of externar urethral esphincter
  • Cerebral cortex: inhibits sacral micturation center
25
Q

Action potential of pacemaker

A

phase 0, upstroke: opening calcium channels (L- channels)
phase 3, repolarization: begin with closure of L type calcium channels, opening K channels, efflux potassium
phase 4: slow influx of sodium

26
Q

Which are the three major components of RAA system regulation?

A
  • macula densa (distal tubule sodium sensor)
  • Intrarenal baroreceptors
  • beta adrenergic receptors
27
Q

Romberg test

A

is a propioception test—- ATAXIA
Difference between cerebellar and sensory:
- sensory: with eyes closed the patienet lost equilibrium (damaged is in posterior columns or peropheral nerves)—- tabes dorsalis or vit b12 deficiency

28
Q

Normal left atrial pressure?

A

10 mmhg

29
Q

Which are the main muscle fiber types in the body?

A

Type I: Slow twitch — postural maintenance, aerobic metabolism
Type II: fast twitch, rapid forceful pulses of movements, anaerobic metabolism.

30
Q

Insulin receptor

A
  • Tetramer: 2 alpha subunit, 2 beta
  • Alpha extrecellular: bind to insulin
  • Beta: intracellular, contain tyrosine kinase domain
    • when insuline attaches—- autophosphorylation of insulin receptor ————— translocation of GLUT-4 to cell membrane.
  • TNF- Alpha—————— induces insuline resistance– activation serine kinases that inhibits tyrosine phosphorylation.
31
Q

Pulmonary capillary wedge pressure

A

almost equal to left atrial pressure and left ventricular end diatolic pressure.
** Normally are equal in diastole but in mitral stenosis the left atrial pressure increase

32
Q

Alveolar hyperventilation

A

low pco2
persistent Hypoxemia
Acute onset Dyspnea

33
Q

Central and peripheral chemoreceptor

A
  • central: most stimulated by PCO2
  • peripheral: by po2
    • COPD patients have decreased sensitivity to changes in PCO2, detects only changes in PO2 (peripheral chemoreceptors)
34
Q

wich Pulmonary artery catheterization measured?

A

pulmonary artery occlusion pressure (the catheter is inflated in pulmonary artery) — reflects left atrium and left ventricular end diastolic pressure

35
Q

In which pulmonar volume the pulmonar vascular resistance is lowest?

A

at functional residual capacity————- PVR takes the shape of “u”———- alveolar and extraalveolar resistance are increased at high and low volumes (max inspiration and max expiration)

36
Q

Respiratory work in restrictive and obstructive disease

A
  • Restrictive: deep and rapid respiratory frequency = decreased respiratory woek
  • Obstructive: slow and deep breaths—- minimized respiratory work
37
Q

Diffusing capacity for carbon monoxide

A
  • obstructive: asthma (normal), emphysema (decreased)

- restructive: instrinsic (decreased), extrinsic (normal)

38
Q

Pancreatic exocrine secretions

A

Na and K are constant: as plasma concentrations

HCO3 and Cl varies with pancreatic fluid rate, increases in reponse to secretin

39
Q

Metabolic changes in diabetic ketoacidosis

A

hyperk: because acidemia drives cells H/K exchange
hypoNa: osmotic activity of glucosa, (serum sodium drops 1.6 meq for every 100 mg rise of blood glucose)

40
Q

I band and H band

A

I Band: thin (actin) filaments, contain Z lines—- lengthens during muscle relaxarion and shortens during contraction.
H band: inverse I band, thick (miosin fibers) both relaxes as the same time

41
Q

Which is the reason to myocyte hypertrophy in myocardial infarction?

A

Decrease aerobic metabolism
Na/K ATPase pump and sarcoplasmic reticulum Ca ATPase——–doesn´t work well———acummulation of sodium and calcium intracellular————- attract free water and cause cellular an mitochondrial swelling

42
Q

Which of the nephron segments responds to vasopressin by increasin absorption of a specific solute?

A

medullary segment of collecting duct

urea concentration increases

43
Q

why is the reason of a rise in glomerular filtration rate during pregnancy?

A

a rise of plasma volume
increased renal circulation mediated by hormone relaxin, stimulated by Bhcg
Dimished bladder capacity because fetus (increased intraabdominal pressure)
Pregnancy hormones increase urethral tone and relax pelvis muscle floor = stress incontinence

44
Q

First objective sign of puberty

A

Breast bud development

45
Q

Most important factor involved in coronary blood flow autoregulation

A

Adenosine and nitric oxide (acst via guanylate cyclase enzyme— increase production of cGMP —- causing smooth muscle relaxation)

46
Q

Secretin

A

release from duodenum in response to cid and fat—- incresing pancreatinc HCO3 secretion and inhibits release of gastrin.
Paradoxically stimulates gstrin release in gastrinomas

47
Q

Diastolic heart failure

A

normal left ventricular ejection fraction > 50%
Normal end diastolic volume
Increased left ventricular filling pressures

48
Q

which is the position of vocal cords while cough

A

open

49
Q

CFTR mutantt channel in cystic fibrosis encodes which kind of gate?

A

ATP gated Cl - channel

50
Q

Hepcidin

A

acute phase reactant, synthesized in lover

  • central regulator homeostasis of iron
  • Influenced iron storage
  • inhiboting ferroportin (protein that tranfering intracellular iron into circulation)

USMLE Step 1 flashcards (10 decks)

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