Biosc 0150 Foundations of Biology I Review 13 Chapter 47 49 Review Chapter 47 Chemical signals in animals 1 Compare and contrast neural signals to endocrine signals Neural signals are spread electrically by neurons whereas endocrine signals can be sent by specialized cells that secrete hormones or neurons that release hormones into the bloodstream in the case of neuroendocrine signals Neural signals can be sent very quickly because they are electrical in nature but they only release a small amount of short lived neurotransmitter at a time into the synapse Endocrine signals are slower than neural signals but can release a larger amount of hormones at a time compared to the small amount of neurotransmitter released in neural signals 2 Explain why chemical hormones can have large effects on all of their target cells even when they are in small quantities Then explain why action potentials cannot affect a wide range of cells via electrical signals Chemical hormones can travel throughout the body within the blood stream When hormones bind or move into cells with specific receptors for them a signal transduction cascade occurs giving a large cell response On the other hand an action potential can only have a short term effect on a small number of cells because the electrical signal cannot travel throughout the body 3 How do hormones travel throughout the body Through the bloodstream a When a hormone is released why are only certain cells affected The response to a hormone is tissue specific because only certain cells contain receptors for particular hormones b Do steroid hormones produce new proteins or activate existing ones What about non steroid hormones Steroid hormones activate transcription factors that lead to the production of new proteins non steroid hormones trigger signal transduction cascades that activate existing proteins c Compare and contrast the modes of action of steroid vs non steroid hormones Steroid hormones act directly and alter gene expression They bind to receptors inside the cell forming a complex that binds to DNA and activates transcription Non steroid hormones act indirectly and activate proteins They bind to receptors on the cell surface and trigger production of a second messenger or a phosphorylation cascade ending in activation of proteins already present in the cell d Suppose a steroid hormone bound to a cell surface receptor Explain how its mode of action would compare to a polypeptide hormone The steroid hormone complex would probably fail to bind to the hormone response element If so then gene expression would not change the arrival of the hormone would have little to no effect on the target cell The mode of action would be similar hormone binding would have to trigger a signal transduction event that resulted in production of a second messenger or a phosphorylation cascade 4 Consider three of the six categories of chemical signals in animals autocrine paracrine and endocrine In terms of prefixes decide how each of these systems operates with regards to spacing in the body Auto the signal from a cell acts on the cell itself para the signal from a cell acts on cells besides it think para llel endo the signal from a cell is transported within the body to other cells through the bloodstream Adel Anthony Megan Dr Swigonova Page 1 of 6 Biosc 0150 Foundations of Biology I Review 13 Chapter 47 49 5 In the neuroendocrine to endocrine pathway there are two chances for feedback inhibition to occur whereas the endocrine and neuroendocrine pathways only have one chance for feedback inhibition to occur First explain what the process of feedback inhibition is Then decide why the neuroendocrine to endocrine pathway has two chances for feedback inhibition to occur Feedback inhibition occurs when the product of a process inhibits its own production similar to LeChatlier s Principle The neuroendocrine to endocrine pathway has two chances for feedback inhibition because it takes two secreted products to elicit a response in target cells First comes the neuroendocrine signal which in turn stimulates and endocrine gland that secretes an endocrine signal Both of these products can inhibit their own production 6 You have identified a certain hormone which directly travels into its target cells Is this hormone water or lipid soluble What class of macromolecule is this hormone likely to be Lipid soluble steroid hormone Would you expect a polar polypeptide hormone to bind to a receptor or diffuse into a cell Bind to a receptor 7 Why is the pituitary gland considered the master gland The pituitary gland is a important in responding to the environment usually without our knowledge It acts as a thermostat that controls all other glands that are responsible for hormone secretion It controls hormone functions such as our temperature thyroid activity growth urine production and testosterone production in males and ovulation and estrogen production in females a Suppose you were to inject someone with adrenocorticotropic hormone ACTH What effect would this have on cortisol levels in the body and why Cortisol is a glucocorticoid that suppresses ACTH production and this is possible because cortisol prevents the release of corticotropin releasing hormone CRH which stimulates the anterior pituitary gland to secrete ACTH b Why is this a form of feedback inhibition When CRH is released from the hypothalamus into the anterior pituitary gland this stimulates the release of ACTH however if there is too much ACTH cortisol will be released back towards the hypothalamus to suppress CRH and to the anterior pituitary gland to suppress ACTH s release c Suppose a person s ACTH levels are high and you inject the person with cortisol however this person s body is damaged and is unable to regulate the hormones through feedback inhibition What would be the result When feedback inhibition fails you will have high levels of cortisol and ACTH which leads to Cushing s disease a fatal disease that depletes the body s protein reserves 8 What is the main similarity and difference between the anterior and posterior pituitary glands Both glands synthesize and release hormones but the anterior pituitary gland forms in an embryo s mouth and throat lining while the posterior pituitary gland is an extension of the brain s hypothalamus a What is the relation of the posterior pituitary gland to the hypothalamus The posterior is directly connected to the hypothalamus and neurosecretory cells from the hypothalamus