Glucocorticoids and GH/TH

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Glucocorticoids and GH/TH

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University of Southern California
Bisc 307l - General Physiology
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BISC 307L 2nd Edition Lecture 18 Current Lecture Stress activates 2 types of neurons in the hypothalamus: the sympathetic neurons that send excitation to the sympathetic preganglionic neurons and neurons that release corticotropin releasing hormones. This activation results in excitation of the peripheral sympathetic system, which results in the release epi and the release of ACTH from the anterior pituitary (and consequently the release of cortisol from the adrenal cortex). These are both stress responses, and they do not overlap much in their time frames. Epinephrine is a rapidly-developing and short-acting stress hormone. Cortisol, on the other hand, is slower in developing its signal, which is more persistent. But they share a lot of their functions – for example, fuel mobilization from stores and how it is distributed in the body, and stimulation of the cardiovascular system. On top of that, epinephrine inhibits visceral function, and inhibits many of the functions that the PS system would enhance. And cortisol inhibits inflammation and immune responses. On the left, you can see that stress activates other areas of the brain that contain neurons that use norepinephrine and CRH as transmitters. These are the amine and peptide transmitters commonly seen in areas of the brain that respond to stress. Norepinephrine neurons tend to mediate behavioral changes like arousal, wakefulness, and appropriate aggressive responses like dilation of the pupils, defensive postures, etc. CRH neurons in these other brain areas tend to inhibit feeding, growth, and reproduction. There is interplay between right hand side (endocrine) and left hand (neural) side. You can see the negative feedback arrows that cross over between both sides. The idea is that taken as a whole, all these responses in the different areas of the brain and the peripheral endocrine system are adaptive and appropriate in stressful situations. They prepare the body an emergency response by shifting resources away from long-term investments, like feeding, growth, and reproduction, and shift it instead towards short-term survival behaviors and abilities. At the same time, they suppress responses of the immune system that might interfere with these life saving behaviors. Thyroid Hormone and Growth Hormone Figs Thyroid Follicles: The thyroid is in neck, and it wraps around just in front of the larynx. Within the thyroid gland, the functional unit is the thyroid follicle. Thyroid follicles are spherical, there is a one cell thick layer surrounding a sphere filled with water. That is called a colloid cell. There are C cells that secrete calcitonin, which we will talk about when we talk about Ca levels. On the right we see a single thyroid epithelial cell. On top is the extracellular space and blood (in capillaries). On the bottom, the yellow stuff is the Colloid. In our normal orientation, the basolateral side is the side facing upwards toward the capillaries, and the apical side is facing the colloid. Step 1: The cells secrete two forms of protein that together make up the colloid material into the colloid –the most abundant is thyroid globulin, shown by ...

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