Physiology Brs Flashcards
Solution 150mM NaCl is …tonic
Isotonic
Solution 300mM mannitol is …tonic
Isotonic
At the muscle end plate ACh causes the opening of
Na and K channels
At the muscle end plate ACh causes …polarization to which value
Depolarization to a value halfway the Na and K equilibrium potentials
Why hyperkalemia causes muscle weakness?
Because Na channels are closed by depolarization
Function of γ-motoneurons
Innervate intrafusal myscle fibers –> adjust the sensitivity of the muscle spidle so that it will respond appropriately during muscle contraction
Decerebrate rigidity is caused by
Increased reflex muscle spindle activity due to removal of inhibition of higher centers
What kind of lesions cause decerebrate rigidity?
Lesions above the lateral vestibular nucleus and lesions above the pontine reticular formation but below the midbrain
The excessive muscle tone in decerebrate rigidity can be reversed by
Cutting the dorsal roots
Second order neurons in the olfactory pathway
Mitral cells
Low doses of epinephrine cause vasodilation/vasoconstriction?
Vasodilation (β2 more sensitive to epinephrine than α)
High doses of epinephrine cause vasodilation/vasoconstriction?
Vasoconstriction (μαλλον εχουν περισσοτερους α)
Conscious proprioception (below the lesion) after complete transection of the spinal cord
Permanently lost (because of the interruption of sensory fibers)
Stretch reflexes (below the lesion) after complete transection of the spinal cord
Temporarily lost (because of the spinal shock) , return with time or become hypersensitive
Dihydropyridine receptors (heart)
Voltage-sensitive protein of the T tubules, L-type channels. During the plateau of the action potential Ca2+ enters the cells from extracellular fluid through these channels
Ryanodine receptors (heart)
Ca2+ that enters the cell through the L-type channels (dihydropyridine receptors) triggers release of Ca2+ from the SR = Ca2+ -induced Ca2+ release)
Digitalis
Inhibits Na-K ATPase -> diminishes Na gradient -> diminishes Na-Ca exchange (that extrudes Ca) -> ^ intrac Ca
Pulmonary blood flow greater than aortic blood flow
Left-to-right ventricular shunt
A pattern of two P waves preceding each QRS complex indicates
Decreased conduction velocity in the AV node
The greatest pressure decrease in the circulation occurs across ______
because
Across the arterioles because they have the greatest resistance (ΔP= Q x R)
Cushing reaction
=response to cerebral ischemia.
^ intracranial pressure ->
compression of the cerebral blood vessels ->
cerebral ischemia (^ CO2) ->
sympathetic outflow to the heart and blood vessels ->
PROFOUND INCREASE IN ARTERIAL PRESSURE
Hering-Breuer reflex
Lung stretch receptors: distention of the lungs –> reflex decrease in RR
J (juxtacapillary) receptors
in the alveolar walls, close to the capillaries
Engorgement of the pulmonary capillaries (e.g. left heart failure) –> rapid, shallow breathing
Adaptation to high altitude
- respiratory alkalosis (acetazolamide)
- ^ EPO
- ^ 2,3-DPG
- Pulmonary vasoconstriction (hypertrophy if the right ventricle)