Why is oxygen so much more critical to the heart muscle than to skeletal muscles?
What will be an ideal response
Cardiac muscle cells are highly dependent on oxygen and rely almost exclusively on aerobic respiration. Thus, they cannot tolerate lack of oxygen due to an inadequate blood supply. When there is a forced switch to anaerobic respiration, lactic acid and rising H+ levels impair heart function.
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Osseous tissue is classified as which of the following?
A) neural tissue B) nonstriated muscle tissue C) connective tissue D) epithelial tissue E) striated muscle tissue
T3 is about 10 times more potent in its biological activity than T4
Indicate whether the statement is true or false
In the absence of extracellular Ca++, an action potential in a motor neuron failed to initiate contraction of the innervated skeletal muscle because of:
A. inhibition of Ca++ influx into the innervated muscle B. inhibition of ACh binding to receptors on the muscle end plate C. stimulation of ACh degradation D. inhibition of ACh release from the motor neuron E. inhibition of Ca++ binding to troponin C in the innervated muscle
Regarding its role as a neurotransmitter in the CNS, norepinephrine
A. is secreted by brainstem neurons in response to sensory stimulation. B. amplifies weak sensory signals and dampens strong ones so that more information can reach conscious levels. C. is important for maintaining directed attention. D. both "is secreted by brainstem neurons in response to sensory stimulation" and "is important for maintaining directed attention" are correct. E. All of the choices are correct.