Answer: D. Contractility of the heart muscle refers to the force of contraction that this muscle can exert.
Explanation:
The myocardial contractility is ability of the heart muscles to contract. This is achieved by the forces which develop between the contracting muscles caused by the filaments of actin and myosin.
The degree of binding of the muscle filaments dependents upon the calcium ion concentration. These actions are controlled in vivo by the sympathetic nervous system. It is driven by the release of the catecholamine, which is a process which determines the calcium ion concentration inside the cytosol of the muscles of the heart.
Answer:
(D). oxytocin.
Explanation:
The hypothalamic-pituitary axis can be defined a pathway that plays a central role in regulation of various endocrine glands. Hormones released from hypothalamus stimulates pituitary gland, which in turns secrete pituitary hormones to regulate release of hormones from other endocrine glands.
Regulation of growth hormone (somatotropin), cortisol (adrenal hormone), prolactin, and T3 (thyroid hormone) is done by hypothalamic-pituitary axis.
Oxytocin is a peptide hormone, which is synthesized by hypothalamus and secreted by posterior pituitary gland. However, level of oxytocin is regulated by positive feedback in loop, in which hormone itself regulates its release and does not involves regulation by hypothalamic-pituitary axis.
Thus, the correct answer is option (D).
Answer:
The correct term is - extrinsic stain.
Explanation:
Extrinsic stains are normally present on the surface of a tooth and occur due to taking pigmented beverages such as coffee, tea, carbonated drinks, caramel coloring, and foods. Smoking cigarettes is also one of the reasons that can cause an extrinsic stain.
This can be removed by dentists or professionals like hygienists. The stain particles act on the outer surface of the teeth and pigmented them which cause stain yellowish or brownish in individuals.
Thus, the correct answer is - extrinsic stain.
