Entrance Exams
Govt. Exams
Dystrophin is a structural protein that stabilizes muscle cell membranes; its absence causes Duchenne muscular dystrophy with progressive muscle weakness.
During inspiration, external intercostal muscles contract, increasing thoracic volume, decreasing intrapleural pressure, and allowing air to flow into lungs.
The countercurrent multiplier creates an osmotic gradient allowing the production of concentrated urine by establishing osmolarity differences in the medulla.
The sympathetic nervous system triggers 'fight or flight' responses including increased heart rate and pupil dilation via norepinephrine and epinephrine.
During the refractory period, sodium channels enter an inactivated state (unable to reopen immediately) while potassium channels remain open, hyperpolarizing the membrane.
ADH (vasopressin) is released in response to increased blood osmolarity, increases aquaporin-2 channels in collecting ducts, and promotes water reabsorption.
Central and peripheral chemoreceptors detect increased CO2 (and decreased pH), sending signals to respiratory centers to increase ventilation rate.
Stapes vibrations move perilymph in the cochlea, causing basilar membrane displacement and stereocilia bending on hair cells, generating action potentials.
MAO degrades monoamines (dopamine, serotonin, norepinephrine) in mitochondria of presynaptic terminals, regulating neurotransmitter levels.
Glycogen depletion in muscles and liver reduces glucose availability for ATP production, causing sudden fatigue despite continued oxygen availability.