Physiology Flashcards by Miranda King

What is the systemic response in vasculature to hypoxia?
Where is this NOT the case?

Hypoxia results in vasodilation in systemic arteries
e.g. brain, kidneys, gut and myocardium
Pulmonary arteries causes vasoconstriction
e.g. in lungs to allow blood to be re-directed within the lung to higher concentrations of O2: allows blood to flow to the most well ventilated parts of the lung = improve O2 delivery
Occurs via increased sympathetic tone

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Osmolality =
- Low osmolality

2(Na+ + K+) + glucose + urea
Low = dilution, low solute available

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Control of inspiration and expiration

Expiration = ventral medulla oblongata
Inspiration = dorsal medulla oblongata

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Anion Gap =

(Na+ + K+) - (Cl- + HCO3-)
Usually 10-16

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Causes of raised anion gap

MUDPILES
Methanol
Uraemia
Renal failure
DKA
Lactic Acidosis
Salicylate
Ethylene glycol

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Where does bicarbonate buffering occur (2)

Proximal tubules (most)
- H+ coupled with sodium/bicarbonate reabsorption
RBC (minor role)
- bicarbonate exchanged for chloride

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How is an acidosis compensated for? (2)

Acute = red blood cell buffering
Chronic = renal bicarbonate

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Causes of respiratory alkalosis (5)

Raised ICP
PE
Pneumonia
Anxiety
Pulmonary oedema

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Causes of metabolic alkalosis (4)

Vomiting
Hyperaldosteronism
Cushing’s syndrome
Bartter’s syndrome

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Hyperchloraemic acidosis

= occurs when there is loss of bicarbonate (rather than increased acid production)
e.g. renal tubular acidosis, acetazolamide

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Hypochloraemic Acidosis (3)

Loss of GI fluids
Over treatment with diuretics
Adrenal insufficiency

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Expiratory reserve volume

= maximum volume of air that can be forcibly expired in a normal breath

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Tidal volume =

approx. 500ml in males
= volume inspired at rest in a normal breath

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Inspiratory reserve volume

= maximum volume of air that can be inspired at the end of a normal tidal respiration

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Vital Capacity =

= TV + IRV + ERV

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Inspiratory capacity =

= tidal volume + inspiratory reserve volume

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VQ Ratio
- what does it mean if it is high?

Volume of air entering alveoli/blood flow through lungs
High = poor perfusion, wasted ventilation
Low = poor ventilation, wasted perfusion

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Production of pulmonary surfactant

Type II pneumocytes

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Types of resistance in work of breathing (2)

Static resistance - elastic recoil of lungs
Dynamic resistance - airways obstruction

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Transfer factor =

= rate at which gas will difuse from alveoli into the blood

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Effects of inspiration and expiration on the heart

Inspiration = increased RV filling and output increases
Expiration = increased LV filling and output

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What is the most important factor in the control of breathing?

pCO2 due to pH effect - central chemoreceptors respond to changes in H+

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Cardiac pacemaker potential

Slow Na+ in
Rapid Calcium in
Rapid K+ out

Hering Bruer Reflex

= distension of lung slows rate of breathing

Phases of Cardiac Action Potential

4,0,1,2,3,4 4 - plateau 0 = Na+ in, rapid depolarisation 1 = K+ out 2 = Ca2+ in/K+ out in balance 3 = K+ out

Cardiac output =

= heart rate x stroke volume

Cardiac contractility - term - positive - negative

= inotropy Positive inotropes = sympathetics, decrease in intracellular Na+, digoxin Negative inotropes = B-blockers, heart failure, hypoxia, acidosis

Preload =

= ventricular end diastolic volume, increased with increased venous return

Afterload =

= total peripheral resistance Altered by increasing/altering vessel calibre

Blood pressure =

= cardiac output x peripheral resistance

Trigger for release of insulin by vesicles

= influx of calcium

Inhibition of insulin secretion (3)

Sympathetics A-blockers B-blockers

Gastrin - where released - action

G cells in antrum of stomach = increased gastric acid production and emptying

Secretin - where released - action

S cells of duodenum/jejunum Action = inhibits gastric acid

CCK - where released - action

I cells of duodenum/jejunum Actions = gallbladder contraction, sphincter of oddi relaxation, satiety

Somatostatin - where released - action

D cells of pancreas/stomach Action = decreases acid secretion, decreases gastrin, insulin and glucagon secretion

VIP - where released - action

Small intestine Action = stimulates pancreatic secretions, inhibits acid secretion

What do parietal cells produce (2)?

HCl Intrinsic Factor

What do chief cells produce?

Pepsinogen (precursor of pepsin)

Pancreatic acinar cells produce...

Enzymes

What do the parafollicular cells produce?

Calcitonin

What does calcitonin do?

Reduces blood calcium levels

What does the zona glomerulosa produce?

Mineralocorticoids

Anterior Pituitary - hormones secreted from basophils

LH and FSH TSH ACTH MSH

Anterior Pituitary - hormones secreted from acidophils

GH Prolactin

Where is ADH synthesised? Where is ADH released from?

Synthesis = supraoptic and paraventricular nuclei of hypothalamus Release from posterior pituitary

Causes of SIADH (8)

Vincristine TB Ectopic focus e.g. small cell lung cancer Pleural effusion Stroke Head Injury Carbamazepine Encephalitis

Where is most sodium and potassium reabsorbed?

Proximal tubule

Distal tubule - secretion - reabsorption

Secretion = H+ and K+ under influence of aldosterone Reabsorption = Na+ and bicarbonate

Carbonic anhydrase inhibitors act on...

Na+/H+ channel in proximal tubule of kidney

Loop Diuretics act on...

Na+/Cl-/2K+ channel in ascending loop = NKCC2 channel

Where is BNP released from?

Ventricular myocytes = natriuresis

Hypervolaemic Hyponatraemia - causes (3) - biochemical findings

Low serum osmolality = dilution 1. Cirrhosis 2. Heart Failure Low urine sodium (kidney trying to reabsorb sodium to try and increase sodium levels) 3. Nephrotic Syndrome High urine sodium - unable to reabsorb

Euvolaemic Hyponatraemia - cause - biochemical findings

Usually SIADH = increased ADH, promotes water retention (lower levels of aldosterone/RAAS as increased ANP/BNP to try and counter water retention) Low serum osmolality High urine sodium (less reabsorption of sodium mediated by aldosterone)

Hypovolaemic Hyponatraemia - causes (4) - biochemical findings

1. Diuretics 2. Vomiting 3. Adrenal Insufficiency High urine Na+ - less reabsorption by aldosterone 4. Burns