1) What type of action does a steroid hormone bring about once it enters the cel
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Question
1) What type of action does a steroid hormone bring about once it enters the cell? 2) How does an amino-acid based hormone exert its effect upon its target cell? 3) Why is a person more likely to become ill when under persistent stress? 4) Insulin and glucagon have an antagonistic relationship. Under which conditions are each released? 5) Thyroxine (TaA) regulates metabolism. What would be the effect if a person has high concentrations of thyroxine? Low concentrations? How could this be observed in regard to body mass? 6) What role does aldosterone play? 7) What are the primary functions of the plasma proteins? 8) What actions or substances can impair blood coagulation? 9) Which antigens and antibodies are present in type A blood? Type B blood? Type AB blood. Type O blood. 10) What ion is required for coagulation? 11) What group of autorhythmic cells of the heart controls the intrinsic heart rate? 12) How is stoke volume determined? 13) What are some hormones that decrease heart rate? Increase heart rate 14) What does each EKG wave pattern represent? 15) Why is MAP significant? 16) What are the three tunics (layers) of blood vessels and what is the significance of each? 17) How is blood pressure regulated in regard to the following: nervous system, endocrine system, renal regulation 18) What type of relationship exists between peripheral resistance of blood flow and diameter, blood vessel length, and blood viscosity? 19) What are the functions of the lymphatic system? 20) Which class of nutrients is transported to the blood by way of the lymphatic system? 21) What is the result of a blocked lymphatic vessel? 22) What are antibodies and which immune cell releases them? 23) What is the primary function of complement? 24) What is the function of interferons? 25) What is the primary significance of T helper cells? 26) How do cytotoxic T cells do their work? 27) What are the characteristics of the innate immune system? The adaptive system? 28) What cells are parts of the innate system? Of the adaptive system?Explanation / Answer
1) There are two ways by which the steroid hormone acts:
a) Genomic pathway- In this, the steroid hormone after entering the cell binds to a specific metalloprotein receptor called as nuclear receptor. As soon as the steroid binds to it, the receptors dimerize and then enters the cell nucleus. After reaching the nucleus, the receptor-seteroid hormone complex bonds to specific DNA sequences to induce transcription and translation of target genes. This is a slow process.
b) Non genomic pathway- In this pathway, the steroid hormone binds to receptors found on the plasma membrane such as G-protein coupled receptors, ion channels,etc. The binding then leads to a rapid activation of second messenger and various signal transduction cascades like protein kinase pathways which eventually modulate the activity of transcription factors in the nucleus and in turn, the transcription and translation of a particular gene.
2) Amino acid based hormones are water soluble. All amino acid -based hormones except thyroid hormone show their effect by signaling pathways with the help of intracellular second messengers which are produced by binding of hormones to the receptors on the plasma membrane. These receptors activate the G proteins which then alters the enzyme activity like adenylyl cyclase or phospholipase C. This activation leads to the production of second messengers which amplifies the initial hormone signal to bring about the physiological action in the cell.
Thyroid hormones enter the cell through membrane transporter proteins and then they bind to intracellular DNA binding receptors in the nucleus. This hormone-receptor complex then interacts with specific DNA sequences and changes gene expression.
3) Due to persistent stress, there is release of the stress hormone cortisol and corticosteroid which weakens the immune system by lowering lymphocyte levels due to which the ability to fight off antigens is reduced increasing the susceptibility to infections. Cortisol is a hormone which supresses inflammation during a stress response. however, due to chronic stress, the body develops resistance towards it and this results in chronic inflammation. Stress responses also affect digestive system, for eg. by release of adrenaline. The digestion is affected during stress and this results in increase of the digestive activity after stress causing ulcers. Stress also causes release of adrenaline and noradrenaline to result in an increase in blood cholesterol levels which ultimately leads to heart diseases.
4) Insulin and glucagon are hormones that help to regulate the blood sugar level (glucose) and work by a negative feedback pathway. When there is increase in blood sugar level after food intake during digestion, this results in the pancreas to secrete insulin into the bloodstream. Insulin signals the cells in the body to take up glucose from the blood into the cells wherein it is used as an energy source or stored in the form of glycogen in liver and muscles. Thus, the blood sugar levels come back to normal.
When the blood sugar levels decrease after a prolonged period without consumption of food, glucagon is released from the pancreas which signals the liver and muscle cells to break down the stored glycogen back into glucose. This glucose in then released into the bloodstream to be used up by other cells in the body to be used as enerygy source.
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