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Chemical Coordination

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Title: Hormones and the Endocrine System Author: Nancy Wheat Last modified by: NANCY WHEAT Created Date: 4/30/2006 10:46:54 PM Document presentation format – PowerPoint PPT presentation

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Title: Chemical Coordination


1
Chemical Coordination
  • Chapter 34

2
Hormones
  • A hormone is a chemical signal that is secreted
    into the circulatory system and communicates
    regulatory messages within the body.
  • Hormones may reach all parts of the body, but
    only certain types of cells, target cells, are
    equipped to respond.

3
Systems of Internal Communication
  • Animals have two systems of internal
    communication and regulation
  • The nervous system
  • The endocrine system

4
Systems of Internal Communication
  • The nervous system conveys high-speed electrical
    signals along specialized cells called neurons.
  • The endocrine system, made up of endocrine
    glands, secretes hormones that coordinate slower
    but longer-acting responses to stimuli.

5
Hormones
  • Advantages of using chemical messengers
  • Chemical molecules can spread to all tissues
    through the blood.
  • Chemical signals can persist longer than
    electrical ones.
  • Many different kinds of chemicals can act as
    hormones different hormones can target different
    tissues.

6
Glands
  • Many hormones are secreted by ductless endocrine
    glands.
  • Obtain raw materials from and secrete hormones
    directly into the bloodstream.
  • Exocrine glands have ducts for discharging
    secretions onto a free surface.
  • Sweat glands, salivary glands, enzyme-secreting
    glands in the digestive tract.

7
Hormones
  • Hormones convey information via the bloodstream
    to target cells throughout the body.
  • Pheromones carry messages outside the body to
    other individuals.

8
Hormones
  • Three major classes of molecules function as
    hormones in vertebrates
  • Proteins and peptides
  • Amines derived from amino acids
  • Steroids

9
Hormones
  • Signaling by any of these molecules involves
    three key events
  • Reception
  • Signal transduction
  • Response

10
Hormones
  • The hypothalamus regulates the neuroendocrine
    system, maintaining homeostasis in the body.
  • The hypothalamus can use motor nerves to send
    short-lived electrical messages or hormones to
    send chemical messages with a longer duration.

11
The Chain of Command
  • The hypothalamus produces seven different
    releasing hormones that travel to the pituitary
    gland.
  • Each releasing hormone stimulates the pituitary
    to release a corresponding hormone which travels
    to an endocrine gland and causes it to start
    producing a particular endocrine hormone.

12
Membrane-Bound Receptors
  • Many hormones are too large, or too polar, to
    pass through plasma membranes.
  • Bind to transmembrane proteins that act as
    receptor sites on target cell membranes.
  • Hormone is first messenger.
  • Causes activation of a second messenger in the
    cytoplasm.
  • cAMP

13
Nuclear Receptors
  • Steroid hormones are lipid soluble molecules that
    bind to hormone receptors in the cytoplasm of the
    target cell.
  • Site of activity is the nucleus.
  • Steroids are manufactured from cholesterol.
  • Estrogen, progesterone, testosterone, cortisol.

14
Nuclear Receptors
  • Thyroid hormones and insect-molting hormone
    (ecdysone) also act through nuclear receptors.
  • Binds to transmembrane protein that uses ATP to
    move it into the cell.

15
Control Pathways and Feedback Loops
  • A common feature of control pathways is a
    feedback loop connecting the response to the
    initial stimulus.
  • Negative feedback regulates many hormonal
    pathways involved in homeostasis.

16
Invertebrate Hormones
  • Ecdysone regulates molting in insects.
  • Juvenile hormone favors the retention of juvenile
    characteristics.

17
The Pituitary
  • The pituitary gland is located below the
    hypothalamus.
  • Nine major hormones are produced here.
  • These hormones act primarily to influence other
    endocrine glands.

18
The Pituitary
  • The posterior lobe of the pituitary regulates
    water conservation, milk letdown, and uterine
    contraction in women.
  • The anterior lobe regulates the other endocrine
    glands.

19
The Anterior Pituitary
  • Thyroid stimulating hormone (TSH) stimulates
    the thyroid gland to produce thyroxine which
    stimulates oxidative respiration.
  • Luteinizing hormone (LH) plays an important role
    in the menstrual cycle. It also stimulates the
    production of testosterone in males.

20
The Anterior Pituitary
  • Follicle-stimulating hormone (FSH) plays an
    important role in the menstrual cycle. In males,
    it causes the testes to produce a hormone that
    regulates sperm production.
  • Adrenocorticotropic hormone (ACTH) stimulates
    the adrenal gland to produce steroid hormones.
    Some regulate glucose production, others balance
    sodium potassium in the blood.

21
The Anterior Pituitary
  • Growth hormone (GH) stimulates the growth of
    muscle and bone.
  • Prolactin stimulates milk production.
  • Melanocyte-stimulating hormone (MSH) in
    reptiles amphibians, this hormone stimulates
    color change.

22
The Posterior Pituitary
  • Antidiuretic hormone (ADH) regulates the kidneys
    retention of water.
  • Oxytocin initiates uterine contraction during
    childbirth and milk release in mothers.
  • These hormones are actually synthesized in the
    hypothalamus and stored in the posterior
    pituitary.

23
Biological Clocks
  • The pineal gland is located in the brain of most
    vertebrates.
  • Evolved from a light sensitive third eye.
  • Primitive fish some reptiles still have a third
    eye.

24
Biological Clocks
  • In other vertebrates it functions as an endocrine
    gland secreting melatonin.
  • Melatonin controls color change in amphibians
    reptiles.
  • Release of melatonin is controlled by light/dark
    cycles.
  • The primary functions of melatonin appear to be
    related to biological rhythms associated with
    reproduction.
  • Circadian rhythms 24 hours long.

25
The Thyroid
  • The thyroid gland, located in the neck, produces
  • Thyroxine increases metabolic rate and promotes
    growth.
  • Two iodine-containing hormones, triiodothyronine
    (T3) and thyroxine (T4).
  • Calcitonin stimulates calcium uptake by bones.

26
The Thyroid
  • The hypothalamus and anterior pituitary control
    the secretion of thyroid hormones through two
    negative feedback loops.

27
The Thyroid
  • The thyroid hormones play crucial roles in
    stimulating metabolism and influencing
    development and maturation.

28
The Parathyroids
  • The parathyroid glands are four small glands
    attached to the thyroid.
  • The hormone they produce is parathyroid hormone
    (PTH) which regulates the level of calcium in the
    blood.
  • Essential that calcium is kept within narrow
    limits for muscle contraction, including the
    heart.

29
Calcium Homeostasis
  • Two antagonistic hormones, parathyroid hormone
    (PTH) and calcitonin, play the major role in
    calcium (Ca2) homeostasis in mammals.

30
Calcium Homeostasis
  • Calcitonin, secreted by the thyroid gland,
    stimulates Ca2 deposition in the bones and
    secretion by the kidneys, thus lowering blood
    Ca2 levels.
  • PTH, secreted by the parathyroid glands, has the
    opposite effects on the bones and kidneys, and
    raises Ca2 levels.
  • Also has an indirect effect, stimulating the
    kidneys to activate vitamin D, which promotes
    intestinal uptake of Ca2 from food.

31
The Adrenals
  • Mammals have an adrenal gland above each kidney.
  • Adrenal medulla is the inner core which produces
    adrenaline (epinephrine) and norepinephrine.
  • Adrenal cortex is the outer shell that produces
    the steroid hormones cortisol and aldosterone.

32
Adrenal Medulla
  • The adrenal medulla releases adrenalin
    (epinephrine) and norepinephrine in times of
    stress.
  • Identical to the effects of the sympathetic
    nervous system, but longer lasting.
  • Accelerated heartbeat, increased blood pressure,
    higher levels of blood sugar and increased blood
    flow to heart and lungs.

33
Adrenal Cortex
  • The adrenal cortex produces the steroid hormone
    cortisol (hydrocortisone).
  • Reduces inflammation.
  • Synthetic derivatives such as prednisone are used
    as anti-inflammatory agents.
  • Stimulates carbohydrate metabolism.

34
Adrenal Cortex
  • The adrenal cortex also produces aldosterone.
  • Aldosterone acts in the kidney to promote the
    uptake of sodium other salts from the urine.
  • These salts are important in nerve conduction.
  • Aldosterone and PTH are the only two hormones
    essential for survival.

35
The Pancreas
  • The pancreas is located behind the stomach and is
    connected to the small intestine by a small tube.
  • It secretes digestive enzymes into the digestive
    tract (exocrine function).
  • Endocrine function production of insulin and
    glucagon.

36
Glucose Homeostasis
  • The islets of Langerhans in the pancreas secrete
    insulin and glucagon.
  • Insulin removes glucose from the blood.
  • Glucagon returns glucose to the blood.

37
Diabetes
  • Diabetes mellitus, perhaps the best-known
    endocrine disorder, is caused by a deficiency of
    insulin or a decreased response to insulin in
    target tissues.
  • Marked by elevated blood glucose levels.

38
Diabetes
  • Type I diabetes mellitus (insulin-dependent
    diabetes) is an autoimmune disorder in which the
    immune system destroys the beta cells of the
    pancreas.
  • Type II diabetes mellitus (non-insulin-dependent
    diabetes) is characterized either by a deficiency
    of insulin or, more commonly, by reduced
    responsiveness of target cells due to some change
    in insulin receptors.
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