Lecture 30 - Endocrine & Neuroendocrine Systems II

Lecture 30 - Endocrine & Neuroendocrine Systems II -...

Info icon This preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Monday’s Class ENDOCRINE & NEUROENDOCRINE SYSTEMS II Chapter 4 pp. 100-­‐111, 130-­‐143 Chapter 3 pp. 92-­‐103, 122-­‐133 Important Deadlines • Problem Set #3 due TONIGHT at 11:59PM • Midterm tomorrow – please bring red scantron What you should be able to do by the end of today’s lecture HORMONES & ENDOCRINE SYSTEMS • Identify the major endocrine axes of vertebrates. • Provide numerous examples of positive and negative feedback in endocrine pathways. Feedback Regulation Many times there is a blood supply here Direct Feedback and First-­‐order Feedback are less common than more complicated regulation by Second-­‐order and Third-­‐order Feedback Principles of Animal Physiology Figure 4.30 Pituitary Hormones • The pituitary gland secretes many hormones • Two distinct sections – Anterior pituitary – Posterior pituitary – (Intermediate lobe) • Often called the “master gland” of vertebrates because it controls so many important processes, including other endocrine tissues • Regulated at many levels Posterior Pituitary • Extension of the hypothalamus – Neurons that originate in hypothalamus terminate in posterior pituitary – Neurohormones oxytocin and vasopressin synthesized in cell body and travel in vesicles down axons • First-­‐order endocrine pathway – Hypothalamus receives sensory input from another neuron – Hypothalamus serves as integrating center Neural control of secretion of neurosecretory cells Principles of Animal Physiology Figure 4.31 Hypothalamus receives sensory signal from another neuron ¯ Hypothalamus synthesizes and secretes neurohormones ¯ Hypothalamic-­‐pituitary portal system ¯ Anterior pituitary releases hormones (endocrine cells) • Tropic hormones Anterior Pituitary – Cause release of another hormone • Third-­‐order endocrine pathway for many ant. pit. hormones Neurosecretory control of secretion by endocrine cells Principles of Animal Physiology Figure 4.32 Separate populations of cells in the Ant Pit secrete different hormones Pituitary – The Master Gland Posterior Pituitary Secretes vasopressin & oxytocin Similar to Fig. 4.33 Hypothalamus-­‐pituitary-­‐adrenal cortex axis (HPA axis) • Axis – when the secretions of one endocrine gland act on another in sequence • HPA axis is the major axis in vertebrates E.g. of hormone chain = CRH à ACTH à Glucocorticoids (e.g. cortisol) • Feedback/modulation at each stage of the pathway Adrenal Tissue in Different Vertebrates Figure 4.41 Vertebrate Stress Response • Interaction between nervous and endocrine systems • Sense organs detect “stress” – Activation of sympathetic nerves • Increased heart rate, respiration, dilation of airways • Decreased secretion of insulin from pancreas • Increased secretion of glucagon from pancreas • Increased secretion of epinephrine from adrenal medulla • Increase in blood glucose level Principles of Animal Physiology Figure 4.37 Obesity Genes -­‐ hormone systems • In the 1960’s two genes, ob and db, were discovered that were associated with obesity in mice – Recessive mutations in either ob or db in homozygous mice causes obesity – Parabiotic mice (suturing two animals together to unite their vascular system allowing exchange in blood borne materials) were used to determine the effects of ob and db normal Experimental evidence that ob/ob recessive mammals can be restored to normal by injection of leptin ob: leptin db: leptin receptor • ob/ob mice injected with leptin have normal metabolic activity Leptin: Ch. 11 pp.555, 558 (2e) Ch. 14 pp 615, 617 (3e) Mutant (ob/ob) causes obesity • Transgenic mice and human mutants with homozygous recessive ob genes are obese. Obesity -­‐ Adiposity and Leptin • Leptin is a peptide hormone secreted in adipose tissue (fat stores) • Leptin levels are correlated with adiposity state • At hypothalamus, leptin inhibits the synthesis and release of neuropeptide Y (NPY) • NPY is the most abundant neuropeptide in the brain. – Increases appetite (feeding behavior) • Obese humans have very high leptin suggesting that the hypothalamus has become resistant to leptin • Leptin also impacts peripheral systems – immune system function, thryoid and gonadal dysfunction • Leptin also: – – – – Lowers insulin levels Lowers cholesterol Lowers triglycerides Increases HDL Iberian pigs are leptin resistant • Have obese phenotype • Higher levels of leptin and insulin than other pigs • Due to polymorphism in leptin receptor gene Regulation of Blood Glucose • Precisely controlled – Blood glucose too low, brain cannot function – Blood glucose too high, osmotic balance of blood disturbed • Hormones – Insulin lowers blood glucose levels – Glucagon raises blood glucose levels • Insulin and glucagon are secreted by pancreas – Direct feedback loops – Pancreas also receives neural and hormonal signals • Antagonistic pairing – Hormones that have opposing effects Pathways Regulating Insulin Secretion Figure 3.33 CCK = cholecystokinin Secreted by the digestive tract Figure 4.34 Effect of these signal transduction pathways is to promote uptake & storage of glucose Antagonistic Regulation of Blood Glucose • Islets of Langerhans perform endocrine functions of the pancreas • Pancreatic alpha cells within islets secrete glucagon • Pancreatic beta cells within islets secrete insulin Figure 4.35 Additivity and Synergism – Additivity • When hormones cause same response in a target cell • Hormones do not use the same signaling pathway – Example: glucagon, epinephrine, and cortisol all raise blood glucose by different mechanisms • Response of target cell to combinations of these hormones is additive – Synergism • When hormones enhance affect of other hormones • Response of target cell to combinations of these hormones more than additive Additivity and Synergism Figure 4.36 Wednesday’s Class MOVEMENT & MUSCLES Chapter 6 pp. 208-­‐243 Chapter 5 pp. 196-­‐235 ...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern