Flashcards in Physiology Deck (64)
What corresponds with the electrical R wave on an ECG?
Mitral valve closure
What happens to the FRC when you age? With height changes?
It increases. This is due to the elastic recoil of the lung decreasing. FRC will increase with height
What effect does propofol have on SSEPs?
Decreases amplitude and increases latency (not to the extent that volatiles or barbiturates will)
What is the standard FRC in a standard adult patient? What is the oxygen consumption?
FRC: 30 ml/kg
O2 consumption: 3-4 ml/kg/min
Name 3 hormones that are metabolized in the pulmonary circulation
2. Serotonin (>95% of serotonin is removed from circulation in one pass through the lungs)
What is the posterior pituitary gland called?
The neurohypophysis (this releases oxytocin and ADH)
Which is more active? T3 or T4? Why? How is T3 formed?
T3 due to decreased protein binding. It is formed by the peripheral conversion of T4 to T3 by 5-iodinase
What neuro monitoring system is MOST affected by volatiles?
Visual: VERY #1
Brainstem auditory: barely
What ratio of urine osmolarity to plasma osmolarity indicates a pre-renal cause of oliguria?
Uosm: Posm > 1.5
Urine osmolarity > 440 and Plasma osmolarity > 285
What effects do a L to R shunt and a R to L shunt have on inhalational induction and IV induction?
1. Inhalational: L to R shunt has no effect, but a R to L shunt SLOWS induction
2. Intravenous: L to R shunt MINIMALLY slows induction (due to recirculation of drugs through the lungs) and a R to L shunt speeds induction
What are the three main ways that CO2 is carried in the blood?
1. Dissolved CO2
3. Carbamino compounds (CO2 bound to proteins)
Name 6 factors that increase MAC
Things that increase cerebral metabolic rate:
3. Chronic alcohol use
4. Increase in central neurotransmitters (seen with MAOIs, levodopa, ephedrine, cocaine, and amphetamines)
5. Red hair
6. Peak at 6 months of age
Which vertebral segments house the SNS?
What ganglia are part of the UE SNS?
upper cervical, middle cervical, and stellate ganglia (stellate is the fusion of the lower cervical and first thoracic ganglia)
What is the reticular activating system?
The part of the brain that alters consciousness. Signals are transported from the RAS via the thalamus to the cerebral cortex. Most anesthetics (except Ketamine) directly depress the RAS. Ketamine works on the Thalamus
Explain the changes seen with pregnancy that occur with spirometry
1. There is minimal to no decrease in TLC or VC
2. There is a decrease in RV and ERV, meaning that IRV will increase
Name the sleep stages, in order, of awake to asleep
BATS Drink Blood
Theta (stage 1)
Spindles and K complexes (stages 3/4)
Higher frequency waves start at the top and decrease in frequency as you progress
What determines movement of fluids across the BBB? What common molecule crosses the BBB freely?
Intravascular osmolarity and oncotic forces.
Water crosses the BBB freely
What techniques can be used as an ancillary modem of confirming brain death? What defines electro cerebral silence?
1. EEG and evoked responses
2. EEG < 2uV/mm activity
What is the volume left at the end of normal tidal volume breathing?
FRC (ERV + RV)
Describe the changes seen with altitude sickness. What are the complications? How can you prevent it?
1. Low PaO2 stimulates the carotid body to tell the brain to breathe
2. Increased ventilation means a resp. alkalosis ( though the alkalosis normalizes, MV remains increased)
3. The CSF then decreases it's concentration of Bicarb prior to plasma via excretion
4. Body equilibrates in 2-3 days
5. Complications include HAPE (more likely if pre-existing pulmonary HTN), and HACE due to hyperemia in the setting of hypoxia
6. Acetazolamide is the prophylaxis
What is the equation for CPP? What does the body do to acutely compensate for increases in ICP?
MAP - (ICP or CVP: depends on which is highest)
- Movement of intracranial venous blood to extra cranial veins or intracranial CSF to spinal CSF
- CBF will NOT decrease. It will INCREASE because it will try to maintain CPP, and this is what explains Cushing's triad
Describe the ABG of a pregnant woman
1. Increased MV leads to a respiratory ALKALOSIS with an incomplete metabolic acidosis for compensation
2. Early in pregnancy, you will see an increase in PaO2 to 105-107 that will then decrease as the pregnancy progresses
Describe the formation and metabolism of Ach
1. Ach is synthesized in neuron terminals by choline acetyltransferase
2. Ach is broken down in the synaptic cleft by acetylcholinesterase (not to be confused with butyrlycholinesterase aka pseudocholinesterase)
Describe the phases of the pacemaker action potential. How does sympathetic activation change this waveform?
Phase 0: influx of Calcium via L-type calcium channels
Phase 3: efflux of K
Phase 4: Influx of Na and Ca via T-type calcium channels
-Sympathetics increase the slope of phase 4, meaning that the myocytes reach their threshold faster
Describe the Renin-Angiotensin-Aldosterone System. Describe the role of Angiotensin II
1. the kidneys sense poor perfusion and release renin
2. The renin then cleaves angiotensinogen to angiotensin 1
3. Angiotensin 1 is converted to Angiotensin II by the lungs (primarily) and the kidney
4. Angiotensin II causes the production of aldosterone
5. Angiotensin II and Aldosterone increase systemic blood pressure, renal perfusion, and increase intravascular volume
6. Angiotensin II: increases SVR by vasoconstriction, increases GFR by constriction of efferent glomerular arterioles, stimulates release of ADH to increase volume, and stimulates production of Aldosterone
7. Aldosterone causes re-absorption of Na and therefore water
What is another term for transpulmonary lung pressure?
Elastic recoil of the lung
What will an ABG show in a patient with diarrhea?
1. Acidosis, diarrhea goes down the tube and so does the pH
(as opposed to vomiting, which goes up and so does the pH)
2. Hyperchloremic metabolic acidosis
What is Winter's formula? When do you use it?
1. used for metabolic acidosis, to determine change in Co2
2. = (1.5*HCO2) + 8 +/-2
3. If CO2 is different, suspect a mixed disorder!