Chapter 10 HB

What are the roles of the hypothalamus with hormone secretion?

- Hormones of the hypothalamus control secretion of hormones from the anterior lobe of the pituitary gland. (Circulatory connection) - Neurosecretory cells in the hypothalamus synthesize and secrete hormones that travel by bloodstream to the anterior lobe. - Releasing hormones produced by the hypothalamus stimulate hormone secretion by the anterior pituitary. Inhibiting hormones inhibit hormone secretion. In the posterior lobe, the hypothalamus has a neural connection. Neurosecretory cells from the hypothalamus project directly into the posterior lobe.

What is the function of the endocrine portion of the pancreas? What are the cell types, their hormones, and their functions?

- endocrine cells of pancreas are present as small clusters - called pancreatic eyelits or eyelits of langerhans; they eyelits produce three types of hormone, glucagon, insulin, somatostatin. glucagon increases level of blood sugar when it declines; it stimulates liver to convert glycogen (storage form of glucose in liver), to glucose; insulin decreases level of sugar in blood, by inhibiting the breakdown of glycogen to glucose

What is the function of the parathyroid gland? How does it relate to the thyroid gland? (function, not location)

- secrete the parathyroid hormone (pth); which increases level of calcium in blood. when calcium levels in blood are low, parathyroid glands secrete pth. pth stimualtes osteoclasts to release calcium from boen into blood; also inhibit osteblasts to reduce rate of calcium deposited in bones; also stimulates kidneys to absorb more calcium from filtrate; and rturn to blood. also stimulates the rate of calcium absorption from the Gastrointestinal tract calcitonin secreted from thryoid gland comes into play when claium levels in blood are high, so they stimlulates osteoblasts and inhibit osteoclasts

What is negative feedback?

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What, specifically, does insulin do? What are its target cells?

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What disease occurs if you have excess/not enough glucocorticoid production? What happens clinically?

excess- cushing disease not enough - addison disease clinically - sodium potassium imbalance

Given that hormones contact virtually all cells in the body, why are only certain cells affected by a particular hormone?

Because they are target cells, which have receptors that recognize and bind to specific hormones.

What is the difference between exocrine and endocrine glands?

Endocrine glands have no ducts, secrete hormones. hormone is released in the blood stream and is circulated in the blood where it finds a particular organ, called target organ, to which goes and influences its physiology. An exocrine gland has duct, which is the conduit for the release of products produced by it. The product is discharged in a place where the product of the gland shows its action.

Can you name target cells for all hormones discussed?

GH: Somatotropes TSH: Thyrotropes TRH/ADH/OXYTOCIN: Neureosecretory Neurons LH/FSH: Gonadotropes PRO: Lactotropes CALCITONIN: Parafollicular cells GLUCAGON: Alpha cells INSULIN: Beta cells

With regard to hormone secretion, can you provide at least one example of negative feedback and one of positive feedback?

Negative feedback systems work by controlling the amount of hormone is present. When the hormone levels drop below normal limits, the receptor senses that the hormone concentration is below the normal limits and initiates hormone production. When the hormone levels reach normal limits, receptor relays a message to the hormone producing cells to shut it down. This way hormone levels are kept within normal limits. Positive feed back occurs in which the outcome of a process feeds back to the system and stimulates the process to continue. For example during childbirth, the pituitary gland releases the hormone, oxytocin, which stimulates the uterus to contract. Uterine contractions then stimulate the release of more oxytocin which stimulates even more contractions.

How are thyroid hormones (remember, this is not the same thing as saying "hormones made in the thyroid gland") regulated? Can you describe the negative feedback loop?

Thyroid hormones (T4 and T3) are produced by the follicular cells of the thyroid gland and are regulated by TSH made by the thyrotropes of the anterior pituitary gland. Hypothalamus releases TRH which causes the Anterior Pituitary to release TSH which causes the Thyroid gland to release T3/T4 which are produced until its blood level hits its set point, at which negative feedback on the hypothalamus and the anterior pituitary will decrease T3 and T4 production.

What is a general understanding of a cause of diabetes? Can you explain how a diabetic has three common symptoms?

blood sugar/glucose levels; in blood is high; these high blood levels are caused by some problem in insulin production or function three common symptoms - crave extra liquids, frequent urination, always hungry

Can you name a glucocorticoid? What is the stimulus for its production?

hormones secreted by adrenal cortex that affect glucose levels; act on liver (cortisol)

How do mechanisms of action differ between the two classes of hormones? Can you give examples of each class?

lipid soluble- moves easily thru cells plasma membrane once inside target comboines with repcetio molecules either in cyto plasm or nucleus, after bindiing, attaches to dna in nucleus and activates certain genes to syntehzieze certain proteins glucocorticoids, mineralocorticoids, gonadcorticoids water soluble- can not pass thru plasma membrane, bind to receptor on plasma membrane of target cell, water soluble hormone called first messenger at this point, binding to receptor, activates anothe rmolecule in cytoplasm which is aclled second messenger that influences acticity of enzymes, this way the water soluble molecules initiate a process of action. cAMP

Explain how someone can become hypothyroid/hyperthyroid. What dietary influence might occur?

thyroid gland secretes two kinds of hormones: T3/T4 T3- attached to three iodine molecules; T4 attached to four when thyroid gland secretes less of T3/T4 it means it is under active and this condition is called hypothyroidism. it is characterized by decreased metabolism, weight gain, thick hair, low pulse, dry skin - simple intake of iodine in diet can take care of this problem; a diet deficient in iodine can produce goiter which is the enlarged thyroid gland; this happens because the thyroid is working overtime in a futile effort to filter more iodine from the blood, because they're diet is deficient in iodine. when thyroid glands secrete excess t3/t4 then the condition hyperthyroidism occurs. this is characterized by high pulse, thin hair, weight loss, insomnia, heat intolerance; excessive intake of iodine hyperthyroid dietary influence - iodine

What are the differences between the lobes of the pituitary gland? (where, what hormones produced, HOW the hormones are triggered to secrete)?

Anterior Lobe of Pituitary Gland: - larger lobe - responds to releasing and inhibiting hormones from the hypothalamus by modifying its own synthesis and secretion of 6 hormones. Posterior Lobe of Pituitary Gland: - neural tissue releases hormones - does not produces hormones of its own