Zoology 101: Animal Biology Last Lecture Outline Lecture 27 1. Hormones 2. Behavior 3. Endocrine systemCurrent lecture 1. Endocrine system and hormones2. Anterior pituitary and other hormonesEndocrine system and hormones • Endocrine system interacts with brain◦ Hypothalamus ▪ Receives signals from neurons and initiates appropriate endocrine response given the environmental conditions ▪ Neurosecretory cells → neurons that produce/release neurotransmitter into the bloodstream◦ Pituitary gland ▪ Posterior pitutary• extension of hypothalamus• 2 hormones released from neurosecretory cells directly into blood vessels in posterior pituitary • ADH (Kidneys tubules) and Oxytocin (mammary glands, uterine muscles), both are water soluble• Oxytocin: regulates maternal activity (positive feedback)◦ Physical: uterine contractions at birth (pitocin), stimulates milk ejection (milk let down)◦ Behavioral: maternal care (highly variable among species) ◦ Stimulus → sensory neuron → hypothalamus/posterior pituitary → neurosecretory cell → neurohormone → blood vessels → target cell → response • ADH: antidiuertic hormone conserves body water ◦ Physical: regulates kidney function ◦ Behavior: forms and maintains strong pair bonds ◦ Acts on kidneys to reduce water loss in urine ◦ Alcohol and caffeine block ADH ◦ Made in hypothalamus and released by posterior pituitary Anterior Pituitary • Releasing hormones (neurohormones) from hypothalamus enter portal veins • Releasing hormones trigger release of anterior pituitary gland• FDH (testes/ovaries), TSH (thyroid), ACTH (adrenal cortex), Prolactin (mammary glands), MSH (melanocytes), GH (liver, bones, tissues) • 2 types of Anterior pituitary hormones ◦ Nontropic: act directly on target (bone, muscle) (i.e. prolactin, MSH, GH)◦ Tropic: Regulate function of other endocrine cells/glands (hypothalamus → pituitary → thyroid); FSH, LH, TSH, ACTH, GH• Tropic and cold ◦ cold stimulus → signal to hypothalamus → release TRH (thyroid releasing hormone) → anterior pituitary secretes T3 and T4 → body tissues → increases cellular metabolism (causing body to warm up) • Hyperthyroidism: excessive production of thyroid hormone ◦ increased temperature, sweating, high blood pressure, weight loss, irritability, ◦ TSH receptors constantly stimulated → thyroid hormone release, Too much T3 and T4• Hypothryroidism: too little thyroid hormone◦ weight gain, lethargy, cold intolerance ◦ Caused (usually) by lack of iodine in food /diet◦ if iodine atoms aren't available, they cant be used and T3 and T4 levels decrease ◦ Hypothalamus releases more TRH → anterior pituitary releases more TSH → elevated levels of TSH cause the thyroid gland to grow in size by increasing cell division (goiter) • Hormones vary across species ◦ Thyroid hormone▪ metabolism across lineages ▪ re absorption of tadpole tale in metamorphosis◦ Melanocyte stimulating Hormone (MSH) regulates skin color in amphibians, reptiles and fish▪ MSH can play a role in hunger/metabolism in addition to coloration▪ In center of cell → light colored pigment. ▪ On edge of cell → dark colored pigment ▪ Color change by MSH → gradual in frog, regulated by nervous system in octopus for rapid color change • Non pituitary hormones (insulin and glucagon)◦ insulin: activates glucose transporters in ca cell◦ Signals cell to insert GLUTs transporter into cell membrane allowing glucose to enter cell◦ without insulin, glucose cant enter the
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