1 / 23

Mechanisms of Hormone Action

Mechanisms of Hormone Action. Figure 16–4b Effects of Intracellular Hormone Binding. Endocrine Reflexes. Endocrine Reflexes Functional counterparts of neural reflexes In most cases, controlled by negative feedback mechanisms

cortez
Télécharger la présentation

Mechanisms of Hormone Action

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Mechanisms of Hormone Action Figure 16–4b Effects of Intracellular Hormone Binding.

  2. Endocrine Reflexes • Endocrine Reflexes • Functional counterparts of neural reflexes • In most cases, controlled by negative feedback mechanisms • Stimulus triggers production of hormone whose effects reduce intensity of the stimulus

  3. Endocrine Reflexes • Endocrine reflexes can be triggered by • Humoral stimuli • Changes in composition of extracellular fluid • Hormonal stimuli • Arrival or removal of specific hormone • Neural stimuli • Arrival of neurotransmitters at neuroglandular junctions

  4. Endocrine Reflexes • Simple Endocrine Reflex • Involves only one hormone • Controls hormone secretion by the heart, pancreas, parathyroid gland, and digestive tract • Complex Endocrine Reflex • Involves • One or more intermediary steps • Two or more hormones • The hypothalamus

  5. Endocrine Reflexes Figure 16–5 Three Mechanisms of Hypothalamic Control over Endocrine Function.

  6. Endocrine Reflexes • Neuroendocrine Reflexes • Pathways include both neural and endocrine components • Complex Commands • Issued by changing • Amount of hormone secreted • Pattern of hormone release: • hypothalamic and pituitary hormones released in sudden bursts • frequency changes response of target cells

  7. The Pituitary Gland • Also called hypophysis • Lies within sella turcica • Diaphragma sellae • A dural sheet that locks pituitary in position • Isolates it from cranial cavity • Hangs inferior to hypothalamus • Connected by infundibulum

  8. Pituitary Gland • Releases nine important peptide hormones • Hormones bind to membrane receptors • Use cAMP as second messenger

  9. Pituitary Gland Figure 16–6a The Anatomy and Orientation of the Pituitary Gland.

  10. Pituitary Gland Figure 16–6b The Anatomy and Orientation of the Pituitary Gland.

  11. Pituitary Gland • Median Eminence • Swelling near attachment of infundibulum • Where hypothalamic neurons release regulatory factors • Into interstitial fluids • Through fenestrated capillaries

  12. Pituitary Gland • Portal Vessels • Blood vessels link two capillary networks • Entire complex is portal system • Ensures that regulatory factors reach intended target cells before entering general circulation

  13. Pituitary Gland Figure 16–7 The Hypophyseal Portal System and the Blood Supply to the Pituitary Gland.

  14. Pituitary Gland • Two Classes of Hypothalamic Regulatory Hormones • Releasing hormones (RH) • Stimulate synthesis and secretion of one or more hormones at anterior lobe • Inhibiting hormones (IH) • Prevent synthesis and secretion of hormones from the anterior lobe • Rate of secretion is controlled by negative feedback

  15. Pituitary Gland • Anterior lobe (also called adenohypophysis) • Hormones “turn on” endocrine glands or support other organs • Can be subdivided into three regions: • Pars distalis • Pars intermedia • Pars tuberalis

  16. Pituitary Gland Figure 16–8a Feedback Control of Endocrine Secretion

  17. Pituitary Gland Figure 16–8b Feedback Control of Endocrine Secretion.

  18. Pituitary Gland Figure 16–9 Pituitary Hormones and Their Targets.

  19. Pituitary Gland

  20. Pituitary Gland • Posterior lobe (also called neurohypophysis) • Contains unmyelinated axons of hypothalamic neurons • Supraoptic and paraventricular nuclei manufacture • Antidiuretic hormone (ADH) • Oxytocin (OXT)

  21. Pituitary Gland Figure 16–9 Pituitary Hormones and Their Targets.

  22. Pituitary Gland

More Related