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Chapter 45 Hormones and the Endocrine System

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Interactions of the endocrine and nervous system in regulating animal's physiology ... Controls metamorphosis of tadpole into frog. ... – PowerPoint PPT presentation

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Title: Chapter 45 Hormones and the Endocrine System


1
Chapter 45 Hormones and the Endocrine System
  • Barbara Musolf
  • Clayton State University
  • AS Building G 110-G
  • 678-466-4851

2
Objectives
  • Interactions of the endocrine and nervous system
    in regulating animals physiology
  • Mechanisms of hormone actions
  • The role of the hypothalamus and pituitary in
    regulating the endocrine system
  • The role of hormones in regulating metabolism,
    homeostasis, development and behavior.
  • Invertebrate regulatory systems

3
Intercellular communication
  • The endocrine system releases hormones into the
    blood.
  • Hormones can reach all cells
  • The spread of hormones takes time
  • The action of hormones can be prolonged
  • The nervous system releases neurotransmitters
    that affect specific neuronal cells.
  • Neurotransmitters reach few cells
  • The response is rapid
  • The action is brief

4
Endocrine system
  • All the hormone secreting cells make up the
    endocrine system
  • Hormone secreting organs are called endocrine
    glands
  • Chemicals are released into the blood and
    extracellular space.
  • Regulate homeostatic processes
  • Regulate developmental processes
  • Male and female characteristics
  • Adult and juvenile characteristics

5
Nervous system overlap
  • Neurosecretory cells found in the brain also
    release hormones called neurohormones
  • Some of these chemical hormones also function as
    neurotransmitters.
  • Nervous system plays a role in regulating some
    parts of the endocrine system
  • Regulation of circadian and seasonal rhythms
  • Regulation of reproductive cycles

6
Intercellular signaling Fig. 45.2a
  • Simple endocrine pathway
  • Release of the signal molecule is into the blood.

7
Intercellular signaling Fig. 45.2b
  • Simple endocrine pathway
  • Release of the signal molecule is into
    intercellular space.

8
Intercellular signaling Fig. 45.2b
  • Simple endocrine pathway
  • Release of the signal molecule is into
    intercellular space.

9
Intercellular signaling Fig. 45.2c
  • Synaptic signaling from presynaptic cell to
    postsynaptic cell
  • Release of the signal molecule is at a synapse.

10
Intercellular signaling Fig. 45.2d
  • Synaptic signaling from presynaptic cell to
    postsynaptic cell
  • Release of the signal molecule is at a synapse.

11
Intercellular signaling Fig. 45.2d
  • Neurosecretory signaling
  • A presynaptic cell releases signal molecule into
    the blood.
  • Signal travels to distant targets

12
Types of secreted signaling hormones
  • Hormones convey signals through the blood stream.
  • Paracrine hormones signal local cells
  • Autocrine hormones target the secreting cell
  • Neurotransmitters and neurohormones
  • 3 classes of hormones
  • Proteins and peptides (under 30 AAs)
  • Amines (derived from a single AA)
  • Steroids
  • Pheromones are volatile signals between organisms

13
Chemical classes of hormones
  • Water soluble hormones bind to plasma membrane
    receptors
  • Steroid hormones bind to intracellular receptors

14
Where is the receptor for MSH?
15
Water soluble hormones Fig. 45.5a
  • Intracellular response can be
  • Activation of an enzyme
  • Change in uptake or secretion of chemicals
  • Rearrangement of cytoskeleton
  • Transcription of particular genes

16
Water soluble hormones
  • Can activate second messenger pathways

17
Lipid soluble hormonesFig. 45.5b
  • Diffusion
  • Formation of hormone/receptor complex
  • Activation of transcription
  • Production of mRNA

18
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19
Different effects from one hormone
20
Local regulators
  • Act faster, use the same pathways
  • Cytokines enhance immune responses
  • Growth factor stimulates proliferation and
    differentiation
  • NO promotes vasodilation
  • Prostaglandins enhance smooth muscle contractions

21
Human endocrine glands
22
Simple hormonal pathway
23
Glucose homeostasis
  • Glucagon and insulin are produced in 2 of the
    cells in the pancreas
  • Islets of Langerhans are scattered throughout the
    pancreas
  • Glucagon is produced by alpha cells
  • Insulin is produced by beta cells
  • Glucagon and insulin are antagonistic hormones
    that regulate glucose in the blood at 90mg/100mL

24
Effects of insulin and glucagon
  • Insulin stimulates all body cells except brain
    cells to take up glucose
  • Insulin slows glycogen breakdown in the liver
  • Insulin inhibits gluconeogenesis and production
    of glucose from glycerol.
  • Glucagon increases glucose in the blood.
  • Glucagon stimulates hydrolysis of glycogen in the
    liver and conversion of AAs and glycerol to
    glucose
  • Only liver cells are sensitive to glucagon.

25
Glucose homeostasis
26
Diabetes
  • Diabetes mellitus has two different causes
  • Type I the immune system destroys beta cells
    leading to lack of insulin
  • Type II is a deficiency of insulin or reduced
    sensitivity of insulin receptors
  • Glucose levels in the blood exceed the
    reabsorbing abilities of the kidney
  • The body turns to fat to produce glucose, which
    produces acidic blood (ketosis)

27
Endocrine and nervous system interactions in
invertebrates
  • Hormones control sexual and asexual reproduction
    in hydra
  • In Aplysia a neurohormone stimulates laying of
    eggs and inhibits appetite and locomotion
  • Crustaceans and insects have hormones that
    regulate molting

28
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31
Endocrine and nervous system interactions in
vertebrates
32
Hypothalamus and posterior pituitary
  • The hypothalamus is the neural integrator
  • Axons project to posterior pituitary and release
    neurohormones
  • Antidiuretic hormone (ADH)
  • Oxytocin

33
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34
Hypothalamus and anterior pituitary
35
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36
Anterior pituitary Tropic hormones
  • Gonadotropins--Follicle stimulating hormone (FSH)
    and leutinizing hormone (LH) stimulate activities
    of ovaries and testes
  • Thyroid stimulating hormone (TSH) stimulates
    production and relase of thyroid hormones
  • Adrenocorticotropic hormone (ACTH) promotes
    production and secretion of steroid hormones from
    the adrenal gland.

37
Anterior pituitary Nontropic hormones
  • Prolactin stimulates mammary gland growth and
    milk synthesis in mammals.
  • Melanocyte stimulating hormone inhibits hunger
  • b-endorphins dull the perception of pain

38
Anterior pituitaryGrowth hormone
  • GH acts on the liver to release insulin-like
    growth factors (IGFs)
  • Stimulates bone and cartilage growth
  • Raises blood glucose levels
  • Hypersecretion leads to gigantism
  • Hyposecretion leads to pituitary dwarfism

39
Thyroid hormones
  • Thyroid gland produces triiodothyronine (T3) and
    thyroxine (T4).
  • Secretes mostly T4, which is converetd to T3 by
    target cells.
  • T3 has a higher affinity for the receptor
  • Hypothalamus and pituitary control secretion of
    thyroid hormones

40
Thyroid hormone
  • Plays an important role in development
  • Controls metamorphosis of tadpole into frog.
  • Required in bone formation and branching of
    neurons during development
  • Inherited conditions of thyroid deficiency can
    lead to cretinism
  • Maintains homeostasis in blood pressure, heart
    rate, muscle tone, digestion and reproduction
  • TH increases oxygen use and cellular metabolism.
  • Graves disease is hyperthyroidism.
  • Hypothyroidism leads to weight gain, lethargy

41
Thyroid hormones calcitonin
  • Calcitonin is secreted from parafollicular cells
    of thyroid.
  • Calcitonin is important in calcium homeostasis.
  • Increases activity of osteoblasts that increase
    bone deposition.

42
Parathyroid hormones
  • The parathyroid glands in humans are collections
    of cells embedded in the dorsal surface of the
    thyroid gland.
  • Parathyroid hormone (PTH) leads to release of
    calcium into the blood.
  • Acts on osteoclasts that breakdown bone
  • Inhibits osteoblast activity
  • Stimulates liver and kidney to produce calcitriol
    from Vitamin D
  • Calcitriol increases absorption of calcium in the
    GI tract.

43
Calcium homeostasis
  • Calcium maintained between 9-11 mg/100 mL

44
Adrenal Hormones
  • Adrenal cortex is an endocrine gland
  • Adrenal medulla is a neuroendocrine gland

45
Adrenal gland and short term stress
46
Adrenal gland and long term stress
47
Gonadal sex hormones
  • Gonads produce androgens, estrogens and
    progestins.
  • Proportions are different in males and females
  • Androgens (testosterone) stimulate development
    and help maintain male reproductive system.
  • In utero they lead to development of males
  • During puberty they are responsible for secondary
    sex characteristics
  • Estrogens (estradiol) is responsible for
    maintenance of female reproductive system and
    development of secondary sex characteristics
  • Progestins prepare and maintain the uterus.

48
The pineal gland and melatonin
  • The pineal gland is located centrally in
    vertebrate brain, often close to the surface.
  • In some organisms, the cells are light sensitive,
    others have input from light sensing regions of
    the hypothalamus.
  • The pineal gland secretes melatonin during dark
    hours
  • It is linked to a biological clock that regulates
    daily and seasonal rhythms
  • Melatonin feeds back to the region of the
    hypothalamus called the suprachiasmatic nucleus
    (SCN)
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