Endocrine Lecture II PDF

University ofGalway.ie  Cell-Cell Communication Large, complex, multi-cellular organisms need long- range signaling mechanisms to coordinate the behavior of cells in remote parts of the body. Thus, they have evolved cell types specialized for intercellular communica/on over large distances...

University ofGalway.ie  Cell-Cell Communication Large, complex, multi-cellular organisms need long- range signaling mechanisms to coordinate the behavior of cells in remote parts of the body. Thus, they have evolved cell types specialized for intercellular communica/on over large distances. University ofGalway.ie ►Major Communication Systems ► Nervous System, Endocrine, Immune Cells ► Neurotransmitters, Hormones, Cytokines ►Integrate Stimuli & Respond to External or Internal Environment Changes ►Coordinated Function University ofGalway.ie ► Highly Differentiated Cells, Tissues and Organs  Autocrine Mechanism of Signaling  Signal released by cells and has a local effect on same cell type from which signals released  Usually inactivated quickly  Prostaglandin University ofGalway.ie Prostaglandin s Autocrine Control University ofGalway.ie  Paracrine Mechanism of Communication Released by cells and affect other cell types locally without being transported in blood University ofGalway.ie Figure 15-4b Molecular Biology of the Cell (© Garland Science 2008) Paracrine Regulation in The Pancreas University ofGalway.ie  Endocrine Mechanism of Communication Long distance signaling. Hormone produced by endocrine glands, enter circulation, affects distant cells with Specific Receptors University ofGalway.ie Neuro-Endocrine Mechanism of Communication  Stimulus Sensed by Nervous Sys ◦Specialized Neuro-endocrine cells produce hormone ◦Signals an Appropriate Response University ofGalway.ie  Phermon es Chemicals secreted in sweat and other bodily fluids that are believed to influence the behavior of the opposite sex of Same Species University ofGalway.ie  Nervous and Endocrine Communication - Similarities Association with Brain– Hypothalamus Common messengers - Neurotransmitter and Hormone ►Epinephrine Two systems are Cooperative ►Nervous sys secretes neuro-hormones, into the circulation ►Parts of endocrine sys innervated directly by nervous sys University ofGalway.ie  Nervous and Endocrine Communication - Differences Mode of transport – Axonal Unidirectional Versus Blood, Interstitial Fluid Speed of response – Nervous – instant/milliseconds – Endocrine – delayed/seconds Duration of response – Nervous – ms/s – Endocrine – mins/days University ofGalway.ie Amplitude vs. Frequency Modulation University ofGalway.ie Controlling Hormone Secretion University ofGalway.ie  Concentration of Hormone - As Seen By Target Cell ► Rate of Production ► Free Vs Bound Hormone ► Synthesis and Secretion ► Rate of Delivery ► Rate of Blood Flow ► Regional Distribution of Blood University ofGalway.ie ► Rate of Degradation and Elimination ► Characteristic Rates of Decay ► Metabolised - Liver and Excreted -Kidney  Free hormone  Fraction available for receptor binding ◦ Represents the active hormone  Determines feedback inhibition that controls hormone release  Is the fraction that is cleared from the circulation University  Correlates with clinical states of hormone excess/deficiency ofGalway.ie Bound Hormone Combined to plasma protein  Non-covalent interactions  Hormone is inactive  Pool of readily available hormone  Increases circulatory hormone half life  Controls rate of delivery to receptor University ofGalway.ie  Synthesis and Secretion of Hormones are the Most Highly Regulated Aspect of Endocrine Control Mediated by Negative and Less Commonly Positive Feedback Circuits University ofGalway.ie Negative Feedback Loops  Positive Feedback Loops Humoral Stimuli - Blood Chemistry Parathyroid hormone (PTH) University ofGalway.ie Humoral Stimuli GlucoseInsulin Glucose Insulin University ofGalway.ie Neural Stimuli Control Control by Hormonal Stimuli University ofGalway.i e Hormone Interaction University ofGalway.ie  Hormone Interaction  Synergism occurs when two or more hormones produce the same effects in a target cell and their results are ampli>ied  Permissiveness A hormone cannot exert its full effects without theUniversity ofGalway.ie presence of another hormone. Agonists and Antagonists University ofGalway.ie  Agonists Mimic Normal Hormone Response ► Bind to a Receptor ► Trigger Cell Response ► Phenylephrine – Adrenaline Agonist ► Used in Medical Treatments ► Adrenaline..J Mucus Secretion ► Stress induced “Dry Mouth” ► Phenylephrine “Cold-relief” ►..J Nasal Mucus Secretions  Antagonis ► Bindto a Receptor ts ► Competes with Messenger For Receptor Site ► Does not Trigger Cell Response Antagonist to Use Androgen Prostate cancer Adrenaline Hypertension Estrogen Breast Cancer Prostaglandin Inflammatory Disease University Progesterone Contraceptive ofGalway.ie  Receptors ► Muscarinic Receptors ► Bind acetylcholine (ACh) in Autonomic Nervous system ► Bind Muscarine – Mushroom Toxin ► Mimics ACh (agonistic action) and can cause a severe parasympathomimetic can be fatal ► Nicotinic Receptors ► Bind ACh at neuromuscular junctions ► Binds curare – Poison Arrow Frog Foxin) ► Blocks the receptor (antagonistic action) ► Prevents neuromuscular transmission – Paralysis Universit y ofGalway.