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Chapter 45. Chemical Signals in Animals. Overview: The Body’s Long-Distance Regulators. Hormones- chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body

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Chapter 45

Chapter 45

Chemical Signals in Animals


Overview the body s long distance regulators
Overview: The Body’s Long-Distance Regulators

  • Hormones- chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body

  • Endocrine system- secretes hormones that coordinate slower but longer-acting responses including reproduction, development, energy metabolism, growth, and behavior

  • Nervous system conveys high-speed electrical signals along specialized cells called neurons; these signals regulate other cells


Types of secreted signaling molecules
Types of Secreted Signaling Molecules

  • Secreted chemical signals include

    • Hormones

    • Local regulators

    • Neurotransmitters

    • Neurohormones

    • Pheromones


Types of secreted signaling molecules1
Types of Secreted Signaling Molecules

  • Hormones- secreted into extracellular fluids and travel via the bloodstream

  • Mediate responses to environmental stimuli and regulate growth, development, and reproduction

  • Local Regulators- chemical signals that travel over short distances by diffusion

  • Help regulate blood pressure, nervous system function, and reproduction


Types of secreted signaling molecules2
Types of Secreted Signaling Molecules

  • Neurotransmitters- diffuse short distances between nerve synapses

  • Play a role in sensation, memory, cognition, and movement

  • Neurohormones- originate from neurons in the brain and diffuse through the bloodstream

  • Pheromones- chemical signals that are used to communicate with other individuals

  • Mark trails to food sources, warn of predators, and attract potential mates


Three major classes of molecules function as hormones in vertebrates
Three major classes of molecules function as hormones in vertebrates:

  • Polypeptides (proteins and peptides)

  • Amines derived from amino acids

  • Steroid hormones

  • Lipid-soluble hormones (steroid hormones) pass easily through cell membranes, while water-soluble hormones (polypeptides and amines) do not


  • Chapter 45

    Water-soluble vertebrates:

    Lipid-soluble

    0.8 nm

    Polypeptide:

    Insulin

    Steroid:

    Cortisol

    Amine:

    Epinephrine

    Amine:

    Thyroxine


    Pathway for water soluble hormones
    Pathway for Water-Soluble Hormones vertebrates:

    • Binding of a hormone to its receptor initiates a signal transduction pathway leading to

    • 1) responses in the cytoplasm

    • 2) enzyme activation

    • 3) or a change in gene expression

    Animation: Water-Soluble Hormone


    Chapter 45

    Epinephrine vertebrates:

    Adenylyl

    cyclase

    G protein

    GTP

    G protein-coupled

    receptor

    ATP

    Epinephrine- result in the release of glucose into the bloodstream

    Second

    messenger

    cAMP

    Protein

    kinase A

    Inhibition of

    glycogen synthesis

    Promotion of

    glycogen breakdown


    Pathway for lipid soluble hormones
    Pathway for Lipid-Soluble Hormones vertebrates:

    • The response to a lipid-soluble hormone is usually a change in gene expression

    Animation: Lipid-Soluble Hormone


    Chapter 45

    Hormone vertebrates:

    (estradiol)

    Estradiol

    (estrogen)

    receptor

    Plasma

    membrane

    Hormone-receptor

    complex

    DNA

    Vitellogenin

    mRNA

    for vitellogenin


    Multiple effects of hormones
    Multiple Effects of Hormones vertebrates:

    • The same hormone may have different effects on target cells


    Chapter 45

    Same receptors but different vertebrates:

    intracellular proteins (not shown)

    Different receptors

    Epinephrine

    Epinephrine

    Epinephrine

    Epinephrine

     receptor

     receptor

     receptor

     receptor

    Glycogen

    deposits

    Vessel

    dilates.

    Vessel

    constricts.

    Glycogen

    breaks down

    and glucose

    is released.

    (a) Liver cell

    (c) Intestinal blood

    vessel

    (b) Skeletal muscle

    blood vessel


    Chapter 45

    Major endocrine glands: vertebrates:

    Hypothalamus

    Pineal gland

    Pituitary gland

    Organs containing

    endocrine cells:

    Thyroid gland

    Thymus

    Parathyroid glands

    Heart

    Liver

    Adrenal

    glands

    Stomach

    Pancreas

    Kidney

    Testes

    Small

    intestine

    Kidney

    Ovaries


    Chapter 45

    Pathway vertebrates:

    Example

    Stimulus

    Low pH in

    duodenum

    S cells of duodenum

    secrete secretin ( )

    Endocrine

    cell

    Negative feedback

    Blood

    vessel

    Target

    cells

    Pancreas

    Bicarbonate release

    Response


    Insulin and glucagon control of blood glucose
    Insulin and Glucagon: Control of Blood Glucose vertebrates:

    • Pancreas- has endocrine cells called islets of Langerhans

      • alpha cells produce glucagon and beta cells produce insulin

    • Insulin reduces blood glucose levels by

      • Promoting the cellular uptake of glucose

      • Slowing glycogen breakdown in the liver

      • Promoting fat storage

    • Glucagon increases blood glucose levels by

      • Stimulating conversion of glycogen to glucose in the liver

      • Stimulating breakdown of fat and protein into glucose


    Chapter 45

    Insulin vertebrates:

    Beta cells of

    pancreas

    release insulin

    into the blood.

    STIMULUS:

    Blood glucose level

    rises.

    Homeostasis:

    Blood glucose level

    (about 90 mg/100 mL)


    Chapter 45

    Body cells vertebrates:

    take up more

    glucose.

    Insulin

    Beta cells of

    pancreas

    release insulin

    into the blood.

    Liver takes

    up glucose

    and stores it

    as glycogen.

    STIMULUS:

    Blood glucose level

    rises.

    Blood glucose

    level declines.

    Homeostasis:

    Blood glucose level

    (about 90 mg/100 mL)


    Chapter 45

    Homeostasis: vertebrates:

    Blood glucose level

    (about 90 mg/100 mL)

    STIMULUS:

    Blood glucose level

    falls.

    Alpha cells of pancreas

    release glucagon.

    Glucagon


    Chapter 45

    Homeostasis: vertebrates:

    Blood glucose level

    (about 90 mg/100 mL)

    STIMULUS:

    Blood glucose level

    falls.

    Blood glucose

    level rises.

    Alpha cells of pancreas

    release glucagon.

    Liver breaks

    down glycogen

    and releases

    glucose.

    Glucagon


    Chapter 45

    Body cells vertebrates:

    take up more

    glucose.

    Insulin

    Beta cells of

    pancreas

    release insulin

    into the blood.

    Liver takes

    up glucose

    and stores it

    as glycogen.

    STIMULUS:

    Blood glucose level

    rises.

    Blood glucose

    level declines.

    Homeostasis:

    Blood glucose level

    (about 90 mg/100 mL)

    STIMULUS:

    Blood glucose level

    falls.

    Blood glucose

    level rises.

    Alpha cells of pancreas

    release glucagon.

    Liverbreaks

    downglycogen

    andreleases

    glucose.

    Glucagon


    Diabetes mellitus
    Diabetes Mellitus vertebrates:

    • Type I diabetes mellitus (insulin-dependent) is an autoimmune disorder in which the immune system destroys pancreatic beta cells

    • Type II diabetes mellitus (non-insulin-dependent) involves insulin deficiency or reduced response of target cells due to change in insulin receptors


    Coordination of endocrine and nervous systems in vertebrates
    Coordination of Endocrine and Nervous Systems in Vertebrates vertebrates:

    • Hypothalamus- receives information from the nervous system and initiates responses through the endocrine system

    • Pituitary gland- attached to the hypothalamus


    Chapter 45

    Cerebrum vertebrates:

    Thalamus

    Pineal

    gland

    Hypothalamus

    Cerebellum

    Pituitary

    gland

    Spinal cord

    Hypothalamus

    Posterior

    pituitary

    Anterior

    pituitary


    Posterior pituitary hormones
    Posterior Pituitary Hormones vertebrates:

    Posterior pituitary- stores and secretes hormones made in the hypothalamus

    • Oxytocininduces uterine contractions and the release of milk (pos. feedback)

    • Antidiuretic hormone (ADH) enhances water reabsorption in the kidneys


    Chapter 45

    Hypothalamus vertebrates:

    Neurosecretorycells of thehypothalamus

    Axon

    Posterior

    pituitary

    Anterior

    pituitary

    HORMONE

    Oxytocin

    ADH

    TARGET

    Kidney tubules

    Mammary glands,uterine muscles


    Chapter 45

    Pathway vertebrates:

    Example

    Stimulus

    Suckling

    +

    Sensoryneuron

    Hypothalamus/posterior pituitary

    Neurosecretorycell

    Posterior pituitarysecretes oxytocin ( )

    Positive feedback

    Bloodvessel

    Smooth muscle inbreasts

    Targetcells

    Response

    Milk release


    Anterior pituitary hormones
    Anterior Pituitary Hormones vertebrates:

    Anterior pituitary makes and releases hormones under regulation of the hypothalamus.

    • For example, the production of thyrotropin releasing hormone (TRH) in the hypothalamus stimulates secretion of the thyroid stimulating hormone (TSH) from the anterior pituitary


    Chapter 45

    Tropic effects only: vertebrates:FSHLHTSHACTH

    Neurosecretory cellsof the hypothalamus

    Nontropic effects only:ProlactinMSH

    Nontropic and tropic effects:GH

    Hypothalamicreleasing andinhibitinghormones

    Portal vessels

    Endocrine cells ofthe anterior pituitary

    Posterior pituitary

    Pituitary hormones

    HORMONE

    FSH and LH

    TSH

    ACTH

    Prolactin

    MSH

    GH

    TARGET

    Testes orovaries

    Thyroid

    Adrenalcortex

    Mammaryglands

    Melanocytes

    Liver, bones,other tissues


    Hormone cascade pathways

    Example vertebrates:

    Pathway

    Hormone Cascade Pathways

    Cold

    Stimulus

    Sensoryneuron

    Hypothalamus secretesthyrotropin-releasinghormone (TRH )

    Neurosecretorycell

    Bloodvessel


    Chapter 45

    Example vertebrates:

    Pathway

    Stimulus

    Cold

    +

    Sensoryneuron

    Hypothalamus secretesthyrotropin-releasinghormone (TRH )

    Neurosecretorycell

    Bloodvessel

    Anterior pituitary secretes

    thyroid-stimulating

    hormone (TSH

    or thyrotropin )


    Chapter 45

    Pathway vertebrates:

    Example

    Stimulus

    Cold

    Sensoryneuron

    Hypothalamus secretesthyrotropin-releasinghormone (TRH )

    Neurosecretorycell

    Bloodvessel

    Anterior pituitary secretes thyroid-stimulatinghormone (TSHor thyrotropin )

    Negative feedback

    Thyroid gland secretes thyroid hormone (T3 and T4 )

    Targetcells

    Body tissues

    Increased cellularmetabolism

    Response


    Tropic hormones
    Tropic Hormones vertebrates:

    • Tropic hormones regulate the function of endocrine cells or glands

      • Thyroid-stimulating hormone (TSH)

      • Follicle-stimulating hormone (FSH)

      • Luteinizing hormone (LH)

      • Adrenocorticotropic hormone (ACTH)


    Nontropic hormones
    Nontropic vertebrates: Hormones

    • Nontropic hormones target nonendocrine tissues

      • Prolactin(PRL)- stimulates lactation in mammals

      • Melanocyte-stimulating hormone (MSH)- skin pigmentation and fat metabolism


    Growth hormone
    Growth Hormone vertebrates:

    • Growth Hormone- secreted by the anterior pituitary gland, has tropic and nontropic actions

    • An excess of GH can cause gigantism, while a lack of GH can cause dwarfism


    Thyroid hormone control of metabolism and development
    Thyroid Hormone: Control of Metabolism and Development vertebrates:

    • Stimulate metabolism and influence development and maturation

    • Hyperthyroidism- high body temp., weight loss, irritability, and high blood pressure

      • Graves’ disease is a form of hyperthyroidism in humans

    • Hypothyroidism- weight gain, lethargy, and intolerance to cold

    • Proper thyroid function requires dietary iodine for hormone production


    Parathyroid hormone and vitamin d control of blood calcium
    Parathyroid Hormone and Vitamin D: Control of Blood Calcium vertebrates:

    • Parathyroid hormone (PTH) increases the level of blood Ca2+

      • It releases Ca2+ from bone and stimulates reabsorption of Ca2+ in the kidneys

      • Stimulates kidneys to activate vitamin D-promotes uptake of Ca2+ from food

    • Calcitonin decreases the level of blood Ca2+

      • It stimulates Ca2+ deposition in bones and secretion by kidneys


    Chapter 45

    PTH vertebrates:

    Parathyroid gland(behind thyroid)

    STIMULUS:

    Falling bloodCa2+ level

    Homeostasis:

    Blood Ca2+ level(about 10 mg/100 mL)


    Chapter 45

    Active vertebrates:vitamin D

    Stimulates Ca2+uptake in kidneys

    Increases Ca2+ uptake in intestines

    PTH

    Parathyroid gland(behind thyroid)

    Stimulates Ca2+ release from bones

    STIMULUS:

    Falling bloodCa2+ level

    Blood Ca2+level rises.

    Homeostasis:

    Blood Ca2+ level(about 10 mg/100 mL)


    Adrenal hormones response to stress
    Adrenal Hormones: Response to Stress vertebrates:

    • Adrenal Medulla- Catecholamines

    • Secretes epinephrine (adrenaline) and norepinephrine(noradrenaline)

    • They mediate various fight-or-flight responses

      • Trigger the release of glucose and fatty acids into the blood

      • Increase oxygen delivery to body cells

      • Direct blood toward heart, brain, and skeletal muscles, and away from skin, digestive system, and kidneys


    Adrenal hormones response to stress1
    Adrenal Hormones: Response to Stress vertebrates:

    • Adrenal Cortex- Steroid Hormones

    • Glucocorticoids, such as cortisol, influence glucose metabolism and the immune system

    • Mineralocorticoids, such as aldosterone, affect salt and water balance


    Chapter 45

    Fig. 45-21a vertebrates:

    Stress

    Nervesignals

    Hypothalamus

    Spinal cord

    Releasinghormone

    Nervecell

    Anterior pituitary

    Blood vessel

    ACTH

    Adrenal medulla

    Adrenal cortex

    Adrenalgland

    Kidney


    Gonadal sex hormones testes and ovaries
    Gonadal vertebrates: Sex Hormones (testes and ovaries)

    • All three sex hormones are found in both males and females, but in different amounts

    • Testes- synthesize androgens(ex: testosterone)- male reproductive system

      • Testosterone causes an increase in muscle and bone mass

    • Estrogens (ex: estradiol)- female reproductive system and secondary sex characteristics

    • Progestins (ex: progesterone)- preparing and maintaining the uterus


    Melatonin and biorhythms
    Melatonin vertebrates:and Biorhythms

    • Pineal gland- located in the brain, secretes melatonin, controlled by light/dark cycles