2Common Aspects of Neural and Endocrine Regulation APs are chemical events produced by diffusion of ions through neuron plasma membrane.Action of some hormones are accompanied by ion diffusion and electrical changes in the target cell.Nerve axon boutons release NTs.Some chemicals are secreted as hormones, and also are NTs.In order for either a NT or hormone to function in physiological regulation:Target cell must have specific receptor proteins.Combination of the regulatory molecule with its receptor proteins must cause a specific sequence of changes.There must be a mechanism to quickly turn off the action of a regulator.
3Endocrine Glands and Hormones Secrete biologically active molecules into the blood.Lack ducts.Carry hormones to target cells that contain specific receptor proteins for that hormone.Target cells can respond in a specific fashion.
4Endocrine Glands and Hormones (continued) Neurohormone:Specialized neurons that secrete chemicals into the blood rather than synaptic cleft.Chemical secreted is called neurohormone.Hormones:Affect metabolism of target organs.Help regulate total body metabolism, growth, and reproduction.
5Chemical Classification of Hormones Amines:Hormones derived from tyrosine and tryptophan.NE, Epi, T4.Polypeptides and proteins:Polypeptides:Chains of < 100 amino acids in length.ADH.Protein hormones:Polypeptide chains with > 100 amino acids.Growth hormone.
6Chemical Classification of Hormones (continued) Lipids derived from cholesterol.Are lipophilic hormones.Testosterone.Estradiol.Cortisol.Progesterone.
7Chemical Classification of Hormones (continued) Glycoproteins:Long polypeptides (>100) bound to 1 or more carbohydrate (CHO) groups.FSH and LH.Hormones can also be divided into:Polar:H20 soluble.Nonpolar (lipophilic):H20 insoluble.Can gain entry into target cells.Steroid hormones and T4.Pineal gland secretes melatonin:Has properties of both H20 soluble and lipophilic hormones.
8Chemical Classification of Hormones (continued) Steroid hormones- lipid solubleSynthesize from cholesterolInvertebrates--Molting hormoneVertebrates– gonads and adrenal cortexPeptide and protein hormones-transported via carrier proteinsInvertebrates– gamete-shedding hormonesVertebrates-- ADH, insulin, growth hormoneAmine hormones–Melatonin, catecholamines, and iodothyronines
9Prohormones and Prehormones Precursor is a longer chained polypeptide that is cut and spliced together to make the hormone.Proinsulin.Preprohormone:Prohormone derived from larger precursor molecule.Preproinsulin.Prehormone:Molecules secreted by endocrine glands that are inactive until changed into hormones by target cells.T4 converted to T3.
10Hormonal Interactions Synergistic:Two hormones work together to produce a result.Additive:Each hormone separately produces response, together at same concentrations stimulate even greater effect.NE and Epi.Complementary:Each hormone stimulates different step in the process.FSH and testosterone.
11Hormonal Interactions (continued) Permissive effects:Hormone enhances the responsiveness of a target organ to second hormone.Increases the activity of a second hormone.Prior exposure of uterus to estrogen induces formation of receptors for progesterone.Antagonistic effects:Action of one hormone antagonizes the effects of another.Insulin and glucagon.
12Effects of [Hormone] on Tissue Response [Hormone] in blood reflects the rate of secretion.Half-life:Time required for the blood [hormone] to be reduced to ½ reference level.Minutes to days.Normal tissue responses are produced only when [hormone] are present within physiological range.Varying [hormone] within normal, physiological range can affect the responsiveness of target cells.
13Effects of [Hormone] on Tissue Response (continued) Priming effect (upregulation):Increase number of receptors formed on target cells in response to particular hormone.Greater response by the target cell.Desensitization (downregulation):Prolonged exposure to high [polypeptide hormone].Subsequent exposure to the same [hormone] produces less response.Decrease in number of receptors on target cells.Insulin in adipose cells.Pulsatile secretion may prevent downregulation.
14Mechanisms of Hormone Action Hormones of same chemical class have similar mechanisms of action.Similarities include:Location of cellular receptor proteins depends on the chemical nature of the hormone.Events that occur in the target cells.To respond to a hormone:Target cell must have specific receptors for that hormone (specificity).Hormones exhibit:Affinity (bind to receptors with high bond strength).Saturation (low capacity of receptors).
15Hormones That Bind to Nuclear Receptor Proteins Lipophilic steroid and thyroid hormones are attached to plasma carrier proteins.Hormones dissociate from carrier proteins to pass through lipid component of the target plasma membrane.Receptors for the lipophilic hormones are known as nuclear hormone receptors.
16Nuclear Hormone Receptors Steroid receptors are located in cytoplasm and in the nucleus.Function within cell to activate genetic transcription.Messenger RNA directs synthesis of specific enzyme proteins that change metabolism.Each nuclear hormone receptor has 2 regions:A ligand (hormone)-binding domain.DNA-binding domain.Receptor must be activated by binding to hormone before binding to specific region of DNA called HRE (hormone responsive element).Located adjacent to gene that will be transcribed.
17Mechanisms of Steroid Hormone Action Cytoplasmic receptor binds to steroid hormone.Translocates to nucleus.DNA-binding domain binds to specific HRE of the DNA.Dimerization occurs.Process of 2 receptor units coming together at the 2 half-sites.Stimulates transcription of particular genes.
18Mechanism of Thyroid Hormone Action T4 passes into cytoplasm and is converted to T3.Receptor proteins located in nucleus.T3 binds to ligand-binding domain.Other half-site is vitamin A derivative (9-cis-retinoic) acid.DNA-binding domain can then bind to the half-site of the HRE.Two partners can bind to the DNA to activate HRE.Stimulate transcription of genes.
19Hormones That Use 2nd Messengers Hormones cannot pass through plasma membrane use 2nd messengers.Catecholamine, polypeptide, and glycoprotein hormones bind to receptor proteins on the target plasma membrane.Actions are mediated by 2nd messengers (signal-transduction mechanisms).Extracellular hormones are transduced into intracellular 2nd messengers.
20Adenylate Cyclase-cAMP (continued) Phosphorylates enzymes within the cell to produce hormone’s effects.Modulates activity of enzymes present in the cell.Alters metabolism of the cell.cAMP inactivated by phosphodiesterase.Hydrolyzes cAMP to inactive fragments.
21Adenylate Cyclase-cAMP Polypeptide or glycoprotein hormone binds to receptor protein causing dissociation of a subunit of G-protein.G-protein subunit binds to and activates adenylate cyclase.ATP cAMP + PPicAMP attaches to inhibitory subunit of protein kinase.Inhibitory subunit dissociates and activates protein kinase.
22Synthesis, storage, and release of hormones Peptide hormonesSynthesized by transcription of DNA, translation and post-translational processingSteroid hormonesSynthesized from cholesterolNot stored, synthesize on demandSecreted by diffusion through cell membrane
23Figure 14.4 Snapshots of insulin synthesis, processing, and packaging (Part 1) anphys-fig jpg
24Figure 14.4 Snapshots of insulin synthesis, processing, and packaging (Part 2) anphys-fig jpg
25Pituitary gland is located in the diencephalon. Structurally and functionally divided into:Anterior lobe.Posterior lobe.
26The mammalian pituitary gland Pars nervosa- posterior pituitaryContains terminals of axonsSecretory cells located in hypothalamusAnterior pituitaryNonneural endocrine cellsSecretion controlled by hypothalamo-hypophyseal portal systemSeparate populations of cells secrete different hormones
27Hypothalamic Control of Posterior Pituitary Hypothalamus neuron cell bodies produce:ADH: supraoptic nuclei.Oxytocin: paraventricular nuclei.Transported along the hypothalamo-hypophyseal tract.Stored in posterior pituitary.Release controlled by neuroendocrine reflexes.
28Figure 14.6 The vertebrate pituitary gland has two parts (Part 1) anphys-fig jpg
29Pituitary Hormones (continued) Posterior pituitary:Stores and releases 2 hormones that are produced in the hypothalamus:Antidiuretic hormone (ADH/vasopressin):Promotes the retention of H20 by the kidneys.Less H20 is excreted in the urine.Oxytocin:Stimulates contractions of the uterus during parturition.Stimulates contractions of the mammary gland alveoli.Milk-ejection reflex.
30Pituitary Gland (continued) Posterior pituitary(neurohypophysis):Formed by downgrowth of the brain during fetal development.Is in contact with the infundibulum.Nerve fibers extend through the infundibulum.Anterior pituitary:AdenohypophysisDerived from a pouch of epithelial tissue that migrates upward from the mouth.
31Anterior Pituitary: Trophic effects: Pituitary HormonesAnterior Pituitary:Trophic effects:High blood [hormone] causes target organ to hypertrophy.Low blood [hormone] causes target organ to atrophy.
32Hypothalamic Control of the Anterior Pituitary Hormonal control rather than neural.Hypothalamus neurons synthesize releasing and inhibiting hormones.Hormones are transported to axon endings of median eminence.Hormones secreted into the hypothalamo-hypophyseal portal system regulate the secretions of the anterior pituitary
33Figure 14.6 The vertebrate pituitary gland has two parts (Part 2) anphys-fig jpg
34Figure 14.6 The vertebrate pituitary gland has two parts (Part 3) anphys-fig jpg
35Figure 14.6 The vertebrate pituitary gland has two parts (Part 4) anphys-fig jpg
36Figure 14.6 The vertebrate pituitary gland has two parts (Part 5) anphys-fig jpg
37Feedback Control of the Anterior Pituitary Anterior pituitary and hypothalamic secretions are controlled by the target organs they regulate.Secretions are controlled by negative feedback inhibition by target gland hormones.Negative feedback at 2 levels:The target gland hormone can act on the hypothalamus and inhibit secretion of releasing hormones.The target gland hormone can act on the anterior pituitary and inhibit response to the releasing hormone.
38Feedback Control of the Anterior Pituitary (continued) Short feedback loop:Retrograde transport of blood from anterior pituitary to the hypothalamus.Hormone released by anterior pituitary inhibits secretion of releasing hormone.Positive feedback effect:During the menstrual cycle, estrogen stimulates “LH surge.”
39Higher Brain Function and Pituitary Secretion Axis:Relationship between anterior pituitary and a particular target gland.Pituitary-gonad axis.Hypothalamus receives input from higher brain centers.Psychological stress affects:Circadian rhythms.Menstrual cycle.
40Figure 14.7 The adrenal gland consists of an inner medulla and an outer cortex anphys-fig jpg
41Figure 14.8 Both hormonal and neural mechanisms modulate the action of the HPA axis anphys-fig jpg
42Figure 14.9 Interactions of insulin, glucagon, and epinephrine anphys-fig jpg
43Figure 14.10 The mammalian stress response (Part 1) anphys-fig jpg
44Figure 14.10 The mammalian stress response (Part 2) anphys-fig jpg
45Figure 14.11 The CNS and the immune system interact during the stress response anphys-fig jpg
46The CNS and the immune system interact during the stress response Cytokines released from certain cells of the immune systemBinds with specific receptor moleculesTravel in the blood to hypothalamusStimulate CRH neurosecretory cellsResulting in the physiological responses of the HPA axisHelps fight infectionGlucocorticoids inhibit the production of agents that cause inflammation-modulating the immune response
47Endocrine control of nutrient metabolism in mammals Insulin secreted when nutrients molecules are abundantHypoglycemic effect- promote uptake of nutrientsInhibit degradation of glycogen, lipids and proteinsGlucagon secreted when glucose level is lowHyperglycemic effect- stimulate break down of glycogen, triglyceride moleculesForms glucose from noncarbohydrate sourcesGrowth hormone, glucocorticoids, epinephrine, thyroid hormones play permissive and synergistic roles in nutrient metabolism
48Figure 14.12 Hormone & nutrient levels in blood of healthy humans before & after a meal (Part 1) anphys-fig jpg
49Figure 14.12 Hormone & nutrient levels in blood of healthy humans before & after a meal (Part 2) anphys-fig jpg
50Figure 14.13 The action of an antidiuretic hormone (Part 1) anphys-fig jpg
51Figure 14.13 The action of an antidiuretic hormone (Part 2) anphys-fig jpg
52Figure 14.14 The renin–angiotensin–aldosterone system (Part 1) anphys-fig jpg
53Figure 14.14 The renin–angiotensin–aldosterone system (Part 2) anphys-fig jpg
54Endocrine control of salt and water balance in vertebrates Vasopressin (ADH)- peptide neurohormoneStimulate conservation of waterAldosteroneStimulate conservation of Na+Part of renin-angiotensin-aldosterone systemANP- atrial natriuretic peptideStimulate the excretion of Na+ and water
55Figure 14.15 Chemical messengers act over short, intermediate, and long distances anphys-fig jpg
56Figure 14.16 Two types of metamorphosis anphys-fig jpg
57Figure 14.17 The silkworm Bombyx mori goes through holometabolous development anphys-fig jpg
58Insect metamorphosis – part 1 Three hormones control metamorphosis:Prothoracicotropic hormone – PTTHEcdysoneJuvenile hormone JHSecreted by nonneural endocrine cellsPrevents metamorphosis in the adult formIn adult, stimulates sex-attractant pheromonesAdditional hormonesBursicaon – darkening and hardening of the cuticleEclosion hormone (EH)Pre-ecdysis triggering hormone (PETH)Ecdysis triggering hormone (ETH)Control stereotyped movements during ecdysis
59Insect metamorphosis part 2 Convergent evolution of endocrine and neuroendocrine functions between vertebrate and invertebrate animalsHemimetabolous insects go through gradual metamorphosisHolometabolous insects go through complete metamorphosisEnvironmental and behavioral signals mediated by the nervous system initiate molting
60Insect metamorphosis – part 3 Neuroendocrine cells in the brain secrete PTTHStimulates secretion of ecdysone from the prothoracic glandsEcdysone is converted to 20-hydroxyecdysone by peripheral activationEpidermis secrete enzymes required for molting process
61Figure 14.19 Endocrine & neuroendocrine structures involved in control of insect metamorphosis (1) anphys-fig jpg
62Figure 14.19 Endocrine & neuroendocrine structures involved in control of insect metamorphosis (2) anphys-fig jpg