1. The marine iguana (Amblyrhynchus cristatus)
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2. Common 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.

3. Endocrine 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.

4. Endocrine 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.

5. Chemical 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.

6. Chemical Classification of Hormones (continued)
Lipids derived from cholesterol.
Are lipophilic hormones.
Testosterone.
Estradiol.
Cortisol.
Progesterone.

7. Chemical 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.

8. Chemical Classification of Hormones (continued)
Steroid hormones- lipid soluble
Synthesize from cholesterol
Invertebrates--Molting hormone
Vertebrates– gonads and adrenal cortex
Peptide and protein hormones-transported via carrier proteins
Invertebrates– gamete-shedding hormones
Vertebrates-- ADH, insulin, growth hormone
Amine hormones–
Melatonin, catecholamines, and iodothyronines

9. Prohormones 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.

10. Hormonal 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.

11. Hormonal 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.

12. Effects 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.

13. Effects 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.

14. Mechanisms 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).

15. Hormones 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.

16. Nuclear 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.

17. Mechanisms 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.

18. Mechanism 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.

19. Hormones 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.

20. Adenylate 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.

21. Adenylate 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 + PPi
cAMP attaches to inhibitory subunit of protein kinase.
Inhibitory subunit dissociates and activates protein kinase.

22. Synthesis, storage, and release of hormones
Peptide hormones
Synthesized by transcription of DNA, translation and post-translational processing
Steroid hormones
Synthesized from cholesterol
Not stored, synthesize on demand
Secreted by diffusion through cell membrane

23. Figure 14.4 Snapshots of insulin synthesis, processing, and packaging (Part 1)
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24. Figure 14.4 Snapshots of insulin synthesis, processing, and packaging (Part 2)
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25. Pituitary gland is located in the diencephalon.
Structurally and functionally divided into:
Anterior lobe.
Posterior lobe.

26. The mammalian pituitary gland
Pars nervosa- posterior pituitary
Contains terminals of axons
Secretory cells located in hypothalamus
Anterior pituitary
Nonneural endocrine cells
Secretion controlled by hypothalamo-hypophyseal portal system
Separate populations of cells secrete different hormones

27. Hypothalamic 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.

28. Figure 14.6 The vertebrate pituitary gland has two parts (Part 1)
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29. Pituitary 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.

30. Pituitary 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:
Adenohypophysis
Derived from a pouch of epithelial tissue that migrates upward from the mouth.

31. Anterior Pituitary: Trophic effects:
Pituitary Hormones
Anterior Pituitary:
Trophic effects:
High blood [hormone] causes target organ to hypertrophy.
Low blood [hormone] causes target organ to atrophy.

32. Hypothalamic 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

33. Figure 14.6 The vertebrate pituitary gland has two parts (Part 2)
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34. Figure 14.6 The vertebrate pituitary gland has two parts (Part 3)
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35. Figure 14.6 The vertebrate pituitary gland has two parts (Part 4)
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36. Figure 14.6 The vertebrate pituitary gland has two parts (Part 5)
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37. Feedback 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.

38. Feedback 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.”

39. Higher 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.

40. Figure 14.7 The adrenal gland consists of an inner medulla and an outer cortex
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41. Figure 14.8 Both hormonal and neural mechanisms modulate the action of the HPA axis
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42. Figure 14.9 Interactions of insulin, glucagon, and epinephrine
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43. Figure 14.10 The mammalian stress response (Part 1)
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44. Figure 14.10 The mammalian stress response (Part 2)
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45. Figure 14.11 The CNS and the immune system interact during the stress response
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46. The CNS and the immune system interact during the stress response
Cytokines released from certain cells of the immune system
Binds with specific receptor molecules
Travel in the blood to hypothalamus
Stimulate CRH neurosecretory cells
Resulting in the physiological responses of the HPA axis
Helps fight infection
Glucocorticoids inhibit the production of agents that cause inflammation-modulating the immune response

47. Endocrine control of nutrient metabolism in mammals
Insulin secreted when nutrients molecules are abundant
Hypoglycemic effect- promote uptake of nutrients
Inhibit degradation of glycogen, lipids and proteins
Glucagon secreted when glucose level is low
Hyperglycemic effect- stimulate break down of glycogen, triglyceride molecules
Forms glucose from noncarbohydrate sources
Growth hormone, glucocorticoids, epinephrine, thyroid hormones play permissive and synergistic roles in nutrient metabolism

48. Figure 14.12 Hormone & nutrient levels in blood of healthy humans before & after a meal (Part 1)
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49. Figure 14.12 Hormone & nutrient levels in blood of healthy humans before & after a meal (Part 2)
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50. Figure 14.13 The action of an antidiuretic hormone (Part 1)
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51. Figure 14.13 The action of an antidiuretic hormone (Part 2)
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52. Figure 14.14 The renin–angiotensin–aldosterone system (Part 1)
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53. Figure 14.14 The renin–angiotensin–aldosterone system (Part 2)
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54. Endocrine control of salt and water balance in vertebrates
Vasopressin (ADH)- peptide neurohormone
Stimulate conservation of water
Aldosterone
Stimulate conservation of Na+
Part of renin-angiotensin-aldosterone system
ANP- atrial natriuretic peptide
Stimulate the excretion of Na+ and water

55. Figure 14.15 Chemical messengers act over short, intermediate, and long distances
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56. Figure 14.16 Two types of metamorphosis
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57. Figure 14.17 The silkworm Bombyx mori goes through holometabolous development
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58. Insect metamorphosis – part 1
Three hormones control metamorphosis:
Prothoracicotropic hormone – PTTH
Ecdysone
Juvenile hormone JH
Secreted by nonneural endocrine cells
Prevents metamorphosis in the adult form
In adult, stimulates sex-attractant pheromones
Additional hormones
Bursicaon – darkening and hardening of the cuticle
Eclosion hormone (EH)
Pre-ecdysis triggering hormone (PETH)
Ecdysis triggering hormone (ETH)
Control stereotyped movements during ecdysis

59. Insect metamorphosis part 2
Convergent evolution of endocrine and neuroendocrine functions between vertebrate and invertebrate animals
Hemimetabolous insects go through gradual metamorphosis
Holometabolous insects go through complete metamorphosis
Environmental and behavioral signals mediated by the nervous system initiate molting

60. Insect metamorphosis – part 3
Neuroendocrine cells in the brain secrete PTTH
Stimulates secretion of ecdysone from the prothoracic glands
Ecdysone is converted to 20-hydroxyecdysone by peripheral activation
Epidermis secrete enzymes required for molting process

61. Figure 14.19 Endocrine & neuroendocrine structures involved in control of insect metamorphosis (1)
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62. Figure 14.19 Endocrine & neuroendocrine structures involved in control of insect metamorphosis (2)
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