Physiology

Question 1

In response to stress, what hormones increases and other has no effect?

Answer 1

GH, ACTH, prolactin, and AVP all have an increased secretion. (The increased pituitary secretion will cause an increase in the target organ secretion: cortisol and aldosterone in the adrenal cortex, glucagon in the pancreas.)

TSH, LH, and FSH are unchanged (although some studies report an increased secretion of TSH).

Question 2

Metabolic changes in response to stress? Glucose, Fat, and protein?

Answer 2

Cortisol promotes glycogenolysis, gluconeogenesis, protein catabolism, lipolysis, and ketone body production.

Protein catabolism is stimulated during stress predominantly from the skeletal muscle but also through some visceral muscle protein breakdown.

Fat metabolism occurs mainly through lipolysis (conversion of triglycerides to glycerol and fatty acids).

In addition, glucagon also promotes hepatic glycogenolysis and gluconeogenesis.

Question 3

The liver is the principal site for drug metabolism. For many drugs, metabolism occurs in two phases. phase one involes … vs phase 2 …

Answer 3

Phase I involves modifying the drug through oxidation, reduction, or hydrolysis. These reactions typically inactivate the drug.

Phase II involves conjugation, where a molecule (glucuronic acid, sulfate) is added to the drug to make it more easily excreted from the kidneys and liver.

Question 4

Cytochrome p450 is involved in phase I metabolism by …

Answer 4

oxidizing many drugs. (the reduction and hydrolysis not carried by CP450)

Question 5

RV vs LV coronary perfusion?

Answer 5

Coronary blood flow is dependent on the gradient between aortic and ventricular pressures. The RV is continuously perfused throughout the cardiac cycle whereas the LV is primarily perfused during ventricular diastole.

Question 6

A UOSM : POSM ratio >1.5 is indicative of …

Answer 6

prerenal oliguria secondary to dehydration or hypovolemia.

The UOSM : POSM is used to assess the tubular response of the kidneys to dehydration or hypovolemia. In this setting of prerenal oliguria, this formula evaluates the kidneys’ ability to retain Na+ and water and produce highly concentrated urine by increasing urine osmolality above 450 mOsm/kg. By comparison, normal plasma osmolality is 280-300 mOsm/kg. The UOSM : POSM indicates the kidneys’ ability to concentrate urine. Tubular damage and acute renal failure, therefore, may be represented by a decreased ratio. The UOSM : POSM can also decrease with the administration of diuretics. As an aside, isosthenuria is a UOSM : POSM equal to 1

Question 7

MAC-awake is …

Answer 7

The alveolar concentration of anesthetic at which a patient will open their eyes on command. It is typically 0.15 to 0.5 MAC.

Question 8

Which innervation requires the highest concentration of volatile anesthetic to prevent movement.

Answer 8

Endotracheal intubation

Question 9

Factors that increase MAC:

Answer 9

certain drugs (amphetamines, cocaine, ephedrine, chronic alcohol consumption), electrolyte disturbances (hypernatremia), hyperthermia, natural red hair, increased central neurotransmitter levels (monoamine oxidase inhibitors, acute dextroamphetamine or cocaine use).

Question 10

Factors that decrease MAC:

Answer 10

certain drugs (opioids, ketamine, benzodiazepines, acute alcohol use), electrolyte disturbances (hyponatremia), anemia, hypercarbia, hypothermia, hypoxia, pregnancy.

Question 11

What is the phase that contributes to the largest volume of blood to the left ventricle during diastole.

Answer 11

Early rapid filling: this phase begins with the opening of the mitral valve. The left ventricle begins to fill with blood from the left atrium. The flow of blood is driven by the transmitral pressure gradient.

Question 12

The phases of diastole are:

Answer 12

isovolumetric relaxation, early rapid filling, diastasis, and atrial contraction.

Question 13

Carotid body chemoreceptors are primarily responsive to reductions in …

Answer 13

arterial partial pressure of oxygen (PaO2).

The carotid body chemoreceptors are located at the bifurcation of the common carotid arteries bilaterally. The chemoreceptors are stimulated to increase minute ventilation in response to decreases in PaO2 below 60-65 mm Hg. Once the PaO2 increases to above 65 mm Hg, the neural input to the central respiratory centers ceases. Ventilation then falls again until the decrease in PaO2 surpasses this threshold again.

Question 14

Stimulation of … receptors causes bronchodilation while … stimulation causes bronchoconstriction.

Answer 14

Stimulation of β2 adrenergic receptors causes bronchodilation while M3 receptor stimulation causes bronchoconstriction.

Question 15

Bronchial smooth muscle relaxes in response to … leading to bronchial dilation.

Answer 15

β2 adrenergic stimulation.

Epinephrine causes significant bronchodilation. Norepinephrine does not cause significant bronchial smooth muscle relaxation as it is more β1-selective.

Question 16

Lipolysis is increased by certain catecholamines … stimulation will increase lipolysis.

… stimulation will inhibit lipolysis.

Answer 16

beta-2 adrenergic

“Belly fat burned when Beta 2 stimulated”

Alpha-2 stimulation will inhibits lipolysis

Question 17

The Bohr and Haldane effects?

Answer 17

The Bohr and Haldane effects are complementary principles that help explain the efficient delivery of O2 to the tissue and CO2 to the lungs.

The Bohr effect states that in areas of high CO2, the hemoglobin has less affinity for O2 which is more readily released for consumption by the tissues.

The Haldane effect states that deoxygenated hemoglobin has a higher affinity for CO2. Once the deoxygenated hemoglobin reaches the lungs, the high O2 concentration decreases this affinity and the CO2 is released.

Question 18

Botulinum toxin can cause symptoms of muscle paralysis by preventing …

Answer 18

the release of acetylcholine-containing vesicles from the axon terminal into the synaptic cleft.

Question 19

Disease states that are known to upregulate NAChR’s include:

Answer 19

• Spinal cord injuries
• Burns
• Prolonged immobilization
• Stroke
• Neuromuscular disorders (e.g. Guillain-Barré, Multiple Sclerosis)

Question 20

While spinal cord injuries are associated with an upregulation of nicotinic acetylcholine receptors, this is typically not evident until at least beyond … and peaks at …

Answer 20

24 hours and usually peaks at 7-10 days beyond the injury date.

Question 21

plasma volume is … of ECV.

Interstitial fluid volume comprises … of the ECV

Answer 21

20-25% of the ECV and represents 4% of total body weight.

75-80% of the ECV and represents 16% of total body weight.

The ECV contains one-third of TBW, represents 20% of total body weight and is composed of plasma volume (20-25%) and interstitial fluid volume (75-80%). where ICV contains the rest 2/3 of TBW ~ 40%

Question 22

Other factors, such as drugs, diseases, and electrolytes, can change the affinity of the hemoglobin by affecting the concentration of 2,3-DPG …

Answer 22

• Thyroxine has shown to stimulate the production of 2,3-DPG, causing a right shift of the ODC.
• Hyperphosphatemia stimulates 2,3-DPG production (right shift), while hypophosphatemia decreases 2,3-DPG (left shift).
• 2,3-DPG is also increased (right shift) in anemia, high-altitude hypoxia, heart failure, liver cirrhosis, and sleep apnea syndrome.
• Propranolol causes a right shift of the ODC in patients with coronary artery disease without affecting 2,3-DPG.
• Stored packed red blood cells have decreased 2,3-DPG resulting in left shift.

Question 23

Hypoxia and hypertension can cause bronchoconstriction and are mediated by …

Answer 23

the vagus nerve. In the case of hypoxia, the carotid body is activated because of the low PaO2, and with hypertension the carotid sinus or the aortic baroreceptors are stimulated. Both carotid body and sinus will then stimulate the parasympathetic nervous system via the vagus nerve, resulting in bronchoconstriction.

Question 24

Bronchoconstriciton can be mediated by the …

Answer 24

parasympathetic nervous system,
the non-adrenergic non-cholinergic (NANC) neurons,
or the alpha-adrenergic receptors

Question 25

Oxygen diffusion is increased during exercise because of the …

Answer 25

Recruitment of non-perfused capillary beds

Question 26

The single best measure to provide an assessment of hepatic protein synthesis function is …

Answer 26

Coagulation factors

This is because clotting factors have a short half-life. For example, factor VII has a half-life of only four to six hours – this is compared to albumin which has a half-life of approximately 21 days.

An excellent indicator of such dysfunction is measurements of prothrombin time. Nevertheless, prothrombin times may be high because of vitamin K deficiency, disseminated intravascular coagulation, congenital clotting factor deficiencies, and certain drugs.

Question 27

The main goal of preoxygenation prior to induction is …

Answer 27

Removal of nitrogen from the functional residual capacity (FRC) increases the content of oxygen available for apneic oxygenation after induction of anesthesia.

With room air-breathing, 95% of the FRC is filled with nitrogen which provides little reserve of oxygen during apnea.

Denitrogenation is most successfully employed by breathing 100% FiO2 with a tight-fitting oxygen mask at 10-12 liters per minute of flow at normal tidal volumes. Time to desaturation to SpO2 of < 90% in healthy nonobese patients can be greater than 8 minutes versus only 1-2 minutes without denitrogenation.