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The plasma membrane is selectively permeable mainly due to the presence of:
Integral membrane proteins (e.g., channels, carriers, pumps) control selective transport. Lipids form the barrier but without proteins, permeability is limited to small nonpolar molecules.
Given: All omnivores are herbivores. No herbivores are carnivores. Some carnivores are humans. Which conclusions are TRUE? I. Some humans are carnivores. II. No carnivores are omnivores. III. Some omnivores are carnivores.
Conclusion I is true (Some carnivores are humans implies some humans are carnivores). Conclusion II is true (omnivores are herbivores, and no herbivores are carnivores, so no carnivores are omnivores). Conclusion III is false (it contradicts the given statements). So I and II are true.
Which neurotransmitter is hydrolyzed by the enzyme monoamine oxidase (MAO)?
MAO breaks down monoamine neurotransmitters: dopamine, serotonin (5-HT), adrenaline, noradrenaline. Acetylcholine is broken down by acetylcholinesterase; glutamate is not a monoamine.
Which enzyme is secreted in its active form without needing activation?
Amylase (salivary and pancreatic) is secreted in active form. Many proteases (e.g., pepsin, trypsin) are secreted as zymogens (inactive precursors) to prevent auto-digestion.
Formula:
\[\text{CPP} = \text{MAP} - \text{ICP}\]
\[\text{CPP} = 90 - 22 = 68 \text{ mmHg}\]
Target values in TBI management (Brain Trauma Foundation):
- CPP target: \(60 - 70 \text{ mmHg}\)
- ICP target: \(< 20 \text{ mmHg}\)
- MAP target: \(\geq 80 \text{ mmHg}\)
- Head of bed elevation \(30°\)
- Hyperosmolar therapy: Mannitol \(0.25 - 1 \text{ g/kg}\) IV or hypertonic saline (3%)
- Controlled hyperventilation: target \(\text{PaCO}_2 = 35 \text{ mmHg}\) (temporary)
- Sedation and analgesia
- Avoid hyperthermia, hypoxia, hypotension
- CSF drainage via ventriculostomy
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