Do Cells Respond to Every Signal | No Not at All
Cells, in general, are designed to respond to specific signals. They can do so because of receptors on their surfaces.
In general, cells respond to bio-molecules like hormones, ions, vitamins, etc. They also respond to drugs, heavy metals and poisons.
But, all the body cells do not respond to all the chemical signals.
To put it in another way we can say that cells do respond to the signals for which they are required to.
However, at times these cells do not respond to specific signals for which they ought to respond.
This condition of non-responsiveness to regular signals is either permanent condition leading to a disease condition. Or, it could also be a temporary condition which could be revoked.
Permanent non-responsiveness of cells
In disease condition, the cells might lack the receptor to respond. One of the best examples for such non-responsiveness in disease condition is Type-II diabetes.
Here cells of the muscles and other tissues do not respond in particular to the Insulin hormone. Insulin is a hormone which enhances the uptake of glucose from the blood into the cells and tissues. Due to the insulin resistance, the cell receptors do not respond to the insulin signal. This leads to lack of energy in the tissues and muscle at the same time the accumulation of glucose in the blood leading to high blood glucose levels.
Hence, the persons having cells with a lack of insulin sensitivity have diabetes. Due to this, they are unable to utilize the glucose in the blood leading to weakness, weight loss and also enhanced sugar levels in urine.
Temporary lack of cell response to stimuli.
Here, the cells do not respond for a short period but, would start responding latter. This condition is due to a phenomenon called as receptor down regulation. The receptors presented on the cell surface and hidden or exhausted. This leads to a lack of response. So, one has to wait for the cell receptors to again up-regulate. After up-regulation, these cells again respond to the stimuli.
One example of such disease condition is breathing insufficiency. Doctors prescribe drugs which act on the β2 adrenergic receptors of the respiratory system to facilitate respiration. But after use of these drugs for five days, then the response goes down. Then the patient is given steroid to up-regulate the β-receptors, and then they again start to respond. So, here β-receptors show temporary non-responsiveness.
For more details on the signal receptors, check our article on types of receptors.
There are also many such diseases or other conditions when cells do not respond to signals.