Describe the structure and function of arrector pili
What will be an ideal response?
Arrector pili are smooth muscles that extend from the superficial dermis of the skin to the dermal root sheath around the side of the hair follicle. In its normal position, hair emerges at an angle to the surface of the skin. Under physiological or emotional stress, such as cold or fright, autonomic nerve endings stimulate the arrector pili muscle to contract, which pulls the hair shafts perpendicular to the skin surface. This action causes "goose bumps" because the skin around the shaft forms slight elevations.
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Which of the following is not a function of thrombin?
a. stimulates conversion of fibrinogen to fibrin b. activates tissue thromboplastin, which initiates the extrinsic clotting pathway c. activates factor XIII (fibrin-stabilizing factor) d. enhances platelet aggregation e. acts in positive-feedback fashion to facilitate its own formation
The primary types of tissues found in animals are
a. muscular. b. nervous. c. epithelial. d. connective. e. all of the above
Which of the following pairs is mismatched?
A. Tentorium cerebelli - base of brain B. Pia mater - surface of the brain C. Falx cerebelli - between the cerebellar hemispheres D. Dural venous sinus - collects blood that returns from the brain E. Falx cerebri - longitudinal fissure
The figure illustrates the autonomic reflexes and the heart. What does "B" represent?
A. sympathetic nerve B. increase in blood pressure detected by carotid baroreceptors C. glossopharyngeal nerve D. decrease in blood pressure detected by carotid baroreceptors E. vagus nerve