Chapter 18: The Endocrine System

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Chapter 18 The Endocrine System
Primary sources for figures and content Marieb,
E. N. Human Anatomy Physiology. 6th ed. San
Francisco Pearson Benjamin Cummings,
2004. Martini, F. H. Fundamentals of Anatomy
Physiology. 6th ed. San Francisco Pearson
Benjamin Cummings, 2004.
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Endocrine System

• Regulates long-term processes
• growth
• development
• reproduction

3
Intercellular Communication

• 1. Direct Communication
• Occurs between two cells of the same type through
  gap junctions via ions or small solutes
• 2. Paracrine Communication
• Uses chemical messengers to transfer signals
  between cells in a single tissue
• Messenger cytokines or local hormones

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Intercellular Communication

• 3. Endocrine Communication
• Uses hormones to coordinate cellular activities
  in distant portions of the body
• Hormones chemical messengers released from one
  tissue and transported in blood to reach target
  cells in other tissues
• Gradual, coordinated but not immediate
• 4. Synaptic Communication
• Involves neurons releasing neurotransmitter at a
  synapse close to target
• Immediate but short lived

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Mechanisms of Intercellular Communication
Table 181
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The Endocrine System

• Consists of glands and glandular tissue involved
  in paracrine and endocrine communication
• Endocrine cells produce secretions ? released
  into extracellular fluid ? enters blood ?
  body-wide distribution to find target
• Target cell specific cells that possess
  receptors needed to bind and read hormonal
  messages

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Endocrine System
Endocrine Cells located In
Figure 181
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Hormones

• Can be divided into 3 groups
• amino acid derivatives
• peptide hormones
• lipid derivatives

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Hormones

• Structure
• 1. Amino Acid Derivatives
• Structurally similar to or based on amino acids
• E.g. catecholamines (epinephrine, norepinephrine,
  dopamine), thyroid hormones, melatonin

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Hormones

• Structure
• 2. Peptide Hormones
• Chains of amino acids
• A. Peptides
• lt200 amino acids
• E.g. ADH, oxytocin, GH
• B. Glycoproteins
• gt200 amino acids with carbohydrate side chain
• E.g. TSH

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Hormones

• Structure
• 3. Lipid Derivatives
• A. Steroid Hormones
• Structurally similar to/based on cholesterol
• E.g. Androgens, Estrogens, Calcitriol
• B. Eicosanoids
• Derived from arachidonic acid
• Not circulating autocrine or paracrine only
• E.g. Leukotrienes from leukocytes ? coordinate
  inflammation
• E.g. Prostaglandins from mast cells ? coordinate
  local activities (smooth muscle contractions,
  clotting, etc.)

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Classes of Hormones
Figure 182
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Mechanism of Action

• Hormones circulate in blood ? contact all cells
• Only cause effects in cells with receptors for
  hormone ? called target cells
• Receptors present on a cell determines the cells
  hormonal sensitivity

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Hormone stimulus effects in target cells

1. Alter plasma membrane permeability or
   transmembrane potential by opening/closing ion
   channels
2. Stimulate synthesis of ? structural proteins,
   receptors, regulatory enzymes within cell
3. Activate or deactivate enzymes
4. Induce secretory activity
5. Stimulate mitosis

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Hormone Receptors

• Located on plasma membrane or inside target
• Cell membrane hormone receptors
• Intracellular hormone receptors

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Hormone Receptors

• 1. Cell membrane hormone receptors
• Catecholamines, peptide hormones, glycoprotein
  hormones, eicosanoids
• Bind receptors on cell surface
• Indirectly trigger events inside cell via second
  messengers (cAMP, Ca)
• 2nd messenger acts as activator, inhibitor, or
  cofactor for intracellular enzymes
• Enzymes catalyze reactions for cell changes
• Receptor linked to 2nd messenger by G protein
  (regulatory enzyme complex)

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Hormone Receptors

• 1. Cell membrane hormone receptors
• 2nd messenger mechanism results in amplification
  of hormone signals
• One hormone molecule binds one receptor but can
  result in millions of final products

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G Proteins and Hormone Activity

• cAMP Mechanism
• Hormone binds receptor
• G-protein activated
• Adenylate cyclase activated
• ATP ? cAMP
• Kinases activated
• Proteins (enzymes) phosphorylated
• Enzymes activated/deactivated

Figure 183
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G Proteins and Hormone Activity

• PIP-Calcium Mechanism
• Hormone binds receptor
• G-protein activated
• Phospholipase C (PLC) activated
• Phospholipids (PIP2) cleaved into diacyglycerol
  (DAG) and inositol triphosphate (IP3)
• DAG opens Ca channels on membrane
• IP3 releases Ca from ER
• Calcium binds calmodulin
• Enzymes Activated

Figure 183
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Hormone Receptors

• 2. Intracellular hormone receptors
• Steroid hormones, thyroid hormones
• Result in direct gene activation by hormone
• Hormone diffuses across membrane, binds receptors
  in cytoplasm or nucleus
• Hormone receptor bind DNA ? transcription ?
  translation protein production ? metabolic
  enzymes, structural proteins, secretions

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Steroid Hormones
Thyroid Hormones
Figure 184a
Figure 184b
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Target cell activation depends on

• 1. Blood level of hormone
• 2. Relative number of receptors
• 3. Affinity of bond between hormone and receptor
• If hormone levels are excessively high for too
  long ? cells can reduce receptor number or
  affinity and become ? non-responsive to a hormone

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Distribution and Duration of Hormones

• Circulating hormones either free or bound to
  carrier/transport proteins
• Free hormones last seconds to minutes
• Rapidly broken down by liver, kidney, or plasma
  enzymes in blood
• Bound hormones last hours to days in blood
• Effect at target cell can take seconds to days
  depending on mechanism and final effect, but
  hormone once bound to receptor is broken down
  quickly

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Interaction of Hormones at Target Cells

• Target cells have receptors for multiple hormones
• Effects of one hormone can be different depending
  on presence or absence of other hormones
• Hormone Interactions
• Antagonistic hormones oppose each other
• Synergistic hormones have additive effects
• Permissive one hormone is needed for the other
  to cause its effect

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Control of Endocrine Activity

• Synthesis and release of most hormones regulated
  by negative feedback

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Control of Endocrine Activity

• 3 Major Stimuli for Hormone Release
• 1. Hormonal stimuli
• Ion and nutrient levels in blood trigger release
• E.g. PTH released when blood Ca is low
• 2. Neural stimuli (autonomic nervous system)
• Nerve fibers directly stimulate release
• E.g. sympathetic ? adrenal medulla epinephrine
  release

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Control of Endocrine Activity

• 3 Major Stimuli for Hormone Release
• 3. Hormonal stimuli
• Hormones stimulate the release of other hormones
• E.g. Releasing hormones of hypothalamus cause
  release of hormones from anterior pituitary
• Hormone release turned on by stimuli and off by
  negative feedback but can be modified by nervous
  system

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KEY CONCEPT

• Hormones coordinate cell, tissue, and organ
  activities
• Circulate in extracellular fluid and bind to
  specific receptors
• Hormones modify cellular activities by
• altering membrane permeability
• activating or inactivating key enzymes
• changing genetic activity

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How could you distinguish between a neural
response and an endocrine response on the basis
of response time and duration?

1. Neural responses are quicker and longer lasting.
2. Neural responses are slower and longer lasting.
3. Neural responses are quicker and shorter in
   duration.
4. Neural responses are slower and shorter in
   duration.

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How would the presence of a molecule that blocks
adenylate cyclase affect the activity of a
hormone that produces its cellular effects by way
of the second messenger cAMP?

1. It would block the action of the hormone.
2. It would enhance the action of the hormone.
3. It would increase sensitivity to the hormone.
4. It would decrease speed of hormonal changes.

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What primary factor determines each cells
hormonal sensitivities?

1. pH of intracellular fluid
2. life cycle phase of cell
3. presence/absence of necessary receptor complex
4. tissue where cell is found

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Endocrine Organs
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1. Hypothalamus
Figure 185
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1. Hypothalamus

• Located at base of 3rd ventricle
• Master regulatory organ
• Integrates nervous and endocrine systems
• Three mechanisms of control
• Secrete regulatory hormones to control secretion
  from anterior pituitary
• - Hormones from anterior pituitary control other
  endocrine organs
• Act as endocrine organ ? Produce ADH and oxytocin
• Has autonomic centers of neural control or
  adrenal medulla ? Neuroendocrine reflex

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2. Pituitary Gland
Figure 186
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2. Pituitary Gland (Hypophysis)

• Hangs inferior to hypothalamus via infundibulum
• In sella turcica of sphenoid
• Anterior lobe secretes 7 hormones
• Function via cAMP 2nd messenger
• Posterior lobe secretes 2 hormones
• Function via cAMP 2nd messenger

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2. Pituitary Gland
Figure 187
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2. Pituitary Gland

• A. Anterior lobe (Adenohypophysis)
• Glandular tissue
• Anterior pituitary hormones are all tropic
  hormones
• Turn on secretion or support function of other
  organs
• Secretion of the hormones controlled by releasing
  and inhibiting hormones from the hypothalamus

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2. Pituitary Gland

• A. Anterior lobe (Adenohypophysis)
• Hormones of the Anterior Lobe

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2. Pituitary Gland

• A. Anterior lobe (Adenohypophysis)
• Disease of Growth Hormone
• Excess
• Usually due to pituitary tumor
• Before epiphyseal closure gigantism
• After acromegaly, excessive growth of hands,
  feet, face, internal organs
• Deficiency
• Pituitary dwarfism failure to thrive

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2. Pituitary Gland

• B. Posterior lobe (Neurohypophysis)
• Neural tissue
• Contains axons of hypothalamus
• Release hormones to posterior lobe for storage
• Hormones release by Posterior Lobe

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The Hormones of the Pituitary Gland
Figure 189
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Hypothalamas and Anterior Lobe

• Rate of secretion is controlled by negative
  feedback
• Hormones turn on endocrine glands or support
  other organs

Figure 188a
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Prolactin (PRL)
Figure 188b
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Hormones

• Releasing Hormones (RH)
• Stimulate synthesis and secretion of 1 or more
  hormones at anterior lobe
• Inhibiting Hormones (IH)
• Prevent synthesis and secretion of hormones from
  anterior lobe

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KEY CONCEPT

• Hypothalamus produces regulatory factors that
  adjust activities of anterior lobe of pituitary
  gland, which produces 7 hormones
• Most hormones control other endocrine organs,
  including thyroid gland, adrenal gland, and
  gonads

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KEY CONCEPT

• Anterior lobe produces growth hormone, which
  stimulates cell growth and protein synthesis
• Posterior lobe of pituitary gland releases 2
  hormones produced in hypothalamus
• ADH restricts water loss and promotes thirst
• oxytocin stimulates smooth muscle contractions
  in
• mammary glands
• uterus
• prostate gland

48
If a person were dehydrated, how would the level
of ADH released by the posterior lobe change?

1. More ADH is released.
2. Less ADH is released.
3. It would not change at all.
4. Initially ADH would decrease, then increase until
   hydration is restored.

49
A blood sample shows elevated levels of
somatomedins. Which pituitary hormone would you
expect to be elevated as well?

1. thyroid stimulating hormone
2. growth hormone
3. oxytocin
4. adrenocorticotropic hormone

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What effect would elevated circulating levels of
cortisol, a steroid hormone from the adrenal
cortex, have on the pituitary secretion of ACTH?

1. ACTH levels would slowly rise.
2. ACTH levels would increase rapidly.
3. ACTH levels would decrease.
4. ACTH levels would remain the same.

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3. Thyroid Gland
Figure 1810a, b
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3. Thyroid Gland

• Inferior to larynx
• Left and right lobes connected by isthmus
• Largest pure endocrine organ
• Tissue
• 1. Follicles ? Spheres or simple cuboidal
  epithelium
• 2. Parafollicular cells/C cells between follicles
• Follicles filled with colloid ? thyroglobulin
• Thyroglobulin protein constantly synthesized by
  follicle cells and exocytosed into follicle for
  storage
• Upon stimulation by TSH, thyroglobulin is
  processed into thyroid hormones (T3/T4)

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Formation and Release of Thyroid Hormones
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Thyroid Follicles
Figure 1811a, b
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3. Thyroid Gland

• Receptors for thyroid hormones located in all
  cells except
• Adult brain, spleen, testes, uterus, thyroid
• 3 receptors in target cells
• Cytoplasm hold hormone in reserve
• Mitochondria increase cellular respiration
• Nucleus activate genes for enzymes involved in
  energy transformation and utilization

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3. Thyroid Gland

• Overall effect of thyroid hormones
• Increase metabolic rate and body heat production
• Regulate tissue growth and development
• 1. Hypothyroidism ? lack of T3/T4
• A. Myxedema (adults)
• Low body temp, muscle weakness, slow reflexes,
  cognitive dysfunction and goiters ? swollen
  thyroid
• Produce thyroglobulin but fail to endocytose
• B. Cretinism (infants) Genetic defect
• Causes lack of skeletal and nervous system
  development

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3. Thyroid Gland

• 2. Hyperthyroidism ? excessive T3/T4
• High metabolic rate, high heart rate,
  restlessness, fatigue
• 3. Graves Disease
• Autoimmune disorder
• Produce antibodies that mimic TSH causing
  overproduction of thyroid hormones

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3. Thyroid Gland

• Parafollicular cells/C cells
• in basement membrane of follicles
• Produce Calcitonin
• Calcitonin stimulates decrease in blood calcium
  levels
• Inhibits osteoclasts
• Promotes Ca loss at kidneys
• Parafollicular cells respond directly to blood
  calcium levels, not controlled by hypothalamus
• Ca 20 above normal calcitonin release

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3. Thyroid Gland
Figure 1810c
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Rate of Thyroid Hormone Release

• Major factor
• TSH concentration in circulating blood

Figure 1811b
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Thyroid Gland
Table 183
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Iodide Ions

• Are actively transported into thyroid follicle
  cells
• stimulated by TSH
• Reserves in thyroid follicles
• Excess removed from blood at kidneys
• Deficiency limits rate of thyroid hormone
  production

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5. Parathyroid Glands

• Four glands embedded in posterior surface of
  thyroid gland

Figure 1812
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5. Parathyroid Gland

• Two cell types
• Oxyphiles few, functions unknown
• Chief Cells majority
• Produce Parathyroid hormone (PTH)/Parathormone
• Most important regulator of blood calcium
• Secreted when blood calcium is low
• Acts to raise blood calcium levels by acting on
  various tissues
• 1. Bone ? stimulates osteoclasts and inhibits
  osteoblasts
• 2. Kidney ? enhances reabsorption of Ca
• 3. Intestines ? promotes conversion of Vit. D to
  calcitriol in kidney to enhance Ca and PO43-
  absorption in small intestine

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4 Effects of PTH

1. It enhances reabsorption of Ca2 at kidneys,
   reducing urinary loss
2. It stimulates formation and secretion of
   calcitriol at kidneys

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Parathyroid Glands

• Primary regulators of blood calcium I levels in
  adults

Figure 1813
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Parathyroid Glands
Table 184
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KEY CONCEPT

• Thyroid gland produces
• hormones that adjust tissue metabolic rates
• a hormone that usually plays minor role in
  calcium ion homeostasis by opposing action of
  parathyroid hormone

69
What symptoms would you expect to see in an
individual whose diet lacks iodine?

1. increased rate of metabolism
2. increased body temperature
3. rapid response to physiological stress
4. goiter

70
When a persons thyroid gland is removed, signs
of decreased thyroid hormone concentration do not
appear until about one week later. Why?

1. Thyroid hormone is produced by other endocrine
   glands.
2. Thyroid hormone remains in circulation for 14
   days.
3. Thyroid-binding globulins provide thryoxine
   reservoirs.
4. Thyroid hormone is used slowly.

71
The removal of the parathyroid glands would
result in a decrease in the blood concentration
of which important mineral?

1. calcium ions
2. phosphate ions
3. sodium ions
4. potassium ions

72
What effect would elevated cortisol levels have
on the level of glucose in the blood?

1. increased glucose
2. decreased glucose
3. modulated glucose around homeostatic optimum
4. dramatic increase of glucose, then a crash

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6. Adrenal Glands
Figure 1814
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6. Adrenal Gland

• 2 glands, in renal fascia, superior to kidney
• Glandular adrenal cortex
• Medulla mostly nervous tissue
• In general ? adrenal hormones are used to cope
  with stressors

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6. Adrenal Glands

• A. Adrenal Cortex
• Produces 24 corticosteriods
• In target alter gene transcription to affect
  metabolism
• Glandular
• 3 layers
• zona glomerulosa
• zona fasciculate
• zona reticularis

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6. Adrenal Glands

• Adrenal Cortex
• Zona glomerulosa ? Mineralcorticoids
• Control water and electrolyte balance
• 95 Aldosterone
• Stimulates Na retention and K loss
• Released in response to
• Low Na or high K
• Angiotension mechanism
• Low blood pressure or volume
• Excessive ACTH

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6. Adrenal Glands

• Adrenal Cortex
• Zona fasciculate ? glucocorticoids
• Metabolic hormones
• Control glucose metabolism
• Most common cortisol, hydrocortisone
• Secretion controlled by ACTH
• Effects ?
• gluconeogenesis in liver
• release of fatty acid from adipose
• triggers protein hydrolysis to release free amino
  acids from skeletal muscle
• triggers body cells to utilize fatty acids and
  amino acids instead of glucose
• Excess ? anti-inflammatory, inhibit immune
  response and healing

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6. Adrenal Glands

• Adrenal Cortex
• 3. Zona reticularis ? gonadocorticoids
• Mostly androgens, may aid onset of puberty
• Excess androgenital syndrome

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Adrenal Cortex
Table 185
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6. Adrenal Glands

• Adrenal Cortex Diseases that affect the
  cortex
• 1. Cushings Syndrome
• Excessive corticosteroids ?
• increase ACTH from pituitary tumor
• Results in ?
• hyperglycemia, decr. Muscle and bone mass,
  hypertension, edema, poor healing, chronic
  infections
• 2. Addisons Disease
• Deficient in corticosteroids
• Results in ?
• Weight loss, hyopglycemia, decr. Na, incr. K in
  plasma, dehydration, hypotension

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6. Adrenal Glands

• B. Adrenal Medulla
• Neural, produces catecholamines to enhance
  effects of other adrenal hormones
• Modified ganglionic sympathetic neurons called
  chromaffin cells release ? epinephrine (80) and
  norepinephrine (20) in response to sympathetic
  stimulation
• Epinephrine effects
• Stimulate heart
• Stimulate metabolic activities ?
• Skeletal muscle mobilize glucogen reserves,
  accelerate ATP production
• Adipose promote release of fatty acids
• Liver promotes release of glucose

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KEY CONCEPT

• Adrenal glands produce hormones that adjust
  metabolic activities at specific sites
• Affects either pattern of nutrient utilization,
  mineral ion balance, or rate of energy
  consumption by active tissues

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6. Pancreas
Figure 1815
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6. Pancreas

• Inferior and posterior to stomach
• Mostly exocrine cells ? pancreatic acini
• Secrete digestive enzymes
• 1 endocrine ? pancreatic islets

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6. Pancreas

• Pancreatic Islets cell types
• 1. Alpha cells ? glucagon ? increase blood
  glucose
• 2. Beta cells ? insulin ? decrease blood glucose
• 3. Delta cells ? somatostatin ?
• Suppresses glucagon and insulin release
• Slows enzyme release into intestines
• 4. F cells ? pancreatic polypeptide ?
• Regulates production of pancreatic enzymes

86
6. Pancreas

• Insulin
• Secreted in response to high blood glucose or ANS
• Parasympathetic incr. insulin
• Sympathetic decr. Insulin
• Effect only on insulin dependent cells (have
  receptors)
• Brain, kidney, GI mucosa, and RBCs
• ALL INSULIN DEPENDENT

87
5 Effects of Insulin

1. Accelerates glucose uptake
2. Accelerates glucose utilization and enhanced ATP
   production
3. Stimulates glycogen formation
4. Stimulates amino acid absorption and protein
   synthesis
5. Stimulates triglyceride formation in adipose
   tissue

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6. Pancreas

• Diabetes mellitus ? too much glucose in blood
  (hyperglycemia)
• Type I ? failure to produce insulin
• Type II ? insulin resistance, sometimes insulin
  deficiency
• Cells can not utilize glucose ? ketone bodies
  produced ? too many ketone bodies lead to
  ketoacidosis
• Glucagon
• Secreted in response to low blood glucose or
  sympathetic stimulation

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3 Effects of Glucagons

1. Stimulates breakdown of glycogen in skeletal
   muscle and liver cells
2. Stimulates breakdown of triglycerides in adipose
   tissue
3. Stimulates production of glucose in liver

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Insulin and Glucagon Effects
Figure 1816
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Pancreatic Islets
Table 186
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KEY CONCEPT

• Pancreatic islets release insulin and glucagons
• Insulin is released when blood glucose levels
  rise
• Stimulates glucose transport into, and
  utilization by, peripheral tissues
• Glucagon released when blood glucose levels
  decline
• Stimulates glycogen breakdown, glucose synthesis,
  and fatty acid release

93
7. Pineal Gland

• Posterior of third ventricle
• Pinealocytes
• Synthesize melatonin from serotonin
• Secretion on diurnal cycle
• High at night, low during dayligh
• Melatonin functions
• 1. Play role in timing of sexual maturation
• 2. Antioxidant ? free radical protection
• 3. Sets circadian rhythms

94
Why does a person with Type 1 or Type 2 diabetes
urinate frequently and have a pronounced thirst?

1. Glucose in the blood inhibits ADH release.
2. Sugar in the urine prevents kidneys from
   reabsorbing water.
3. High blood sugar dehydrates the tissues of the
   mouth.
4. Blood sugar elevates blood volume, increasing
   urine output.

95
What effect would increased levels of glucagon
have on the amount of glycogen stored in the
liver?

1. increased glycogen
2. decreased glycogen
3. no effect
4. rapid increase of glycogen, with a slow return to
   homeostasis

96
Increased amounts of light would inhibit the
production of which hormone?

1. prolactin
2. melanocyte stimulating hormone
3. aldosterone
4. melatonin

97
Hormones Produced by Specific Organs
Table 187
98
8. Gastrointestinal Tract

• Enteroendorine cells in GI mucosa secrete many
  hormones ? coordinate digestive activity
• Mostly paracrine communication
• Cholecystokinin
• Enterocrinin
• Gastric inhibitory peptide
• Gastrin
• Secretin
• Vasoactive intestinal peptide

99
(No Transcript)
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9. Kidneys

• Various endocrine cells
• Three products
• 1. Calcitrol ? Steroid hormone
• Stimulate Ca, PO43- absorption in GI
• Stimulate osteoclast activity
• Stimulate Ca retention in kidney
• Suppress PTH production
• 2. Erythropoeitin ? Peptide hormone
• Released in response to low O2 in kidney
• 3. Renin ? Enzyme

101
9. Kidneys

• Three products
• 3. Renin ? Enzyme
• Released in response to sympathetic stimulation
  or decline in renal blood flow
• Converts angiotensin in blood into Angiotensin II
  (hormone)
• Angiotensin II effects
• Stimulate secretion of aldosterone ? adrenal
• Stimulate secretion of ADH ? pituitary
• Stimulate thirst
• Elevate BP
• Both aldosterone and ADH ? restrict Na and H2O
  loss at kidney

102
Calcitriol

• Stimulates calcium and phosphate ion absorption
  along digestive tract

Figure 1817a
103
The ReninAngiotensin System
Figure 1817b
104
10. Heart

• Some cells of atrial walls secrete Atrial
  Natriuretic Peptide in response to stretch
• ANP promotes Na and water loss at kidney
• Inhibits release of renin, ADH, and aldosterone ?
  reduce BP and volume

105
11. Thymus

• Located deep to sternum
• Cell produces thymosin hormones
• Promote development and maturation of T
  lymphocytes and the immune response

106
12. Gonads

• A. Testes ? male
• Interstitial cells produce androgens in response
  to LH
• Testosterone, most common
• Produces male secondary sex characteristics
• Promotes sperm production
• Maintains secretory glands

107
12. Gonads

• B. Ovaries ? Female
• Follicle cells produce estrogens in response to
  FSH and LH
• Estradiol, most important
• Produce female secondary sex characteristics
• Support maturation of oocytes
• Stimulate growth of uterine lining
• Surge in LH causes
• Ovulation
• Follicle reorganizes to form corpus luteum
• Produces estrogens and progestins, especially
  progesterone

108
12. Gonads

• B. Ovaries ? Female
• Progesterone, most important
• Prepares uterus for embryo growth
• Accelerates movement of oocyte/embryo to uterus
• Enlargement of mammary glands

109
13. Adipose

• 1. Leptin secretion
• in response to absorption of glucose and lipids
• Triggers satiation in appetite center of
  hypothalamus
• controls normal levels of GnRH, gonadotropin
  synthesis
• 2. Resistin secretion
• Reduces insulin sensitivity

110
Hormones interact to produce coordinated
physiological responses.
111
Hormone Interactions

• Antagonistic (opposing) effects
• Synergistic (additive) effects
• Permissive effects
• 1 hormone is necessary for another to produce
  effect
• Integrative effects
• hormones produce different and complementary
  results

112
Hormones Important to Growth

1. GH
2. Thyroid hormones
3. Insulin
4. PTH
5. Calcitriol
6. Reproductive hormones

113
Growth Hormone (GH)

• In children
• supports muscular and skeletal development
• In adults
• maintains normal blood glucose concentrations
• mobilizes lipid reserves

114
Thyroid Hormones

• If absent during fetal development or for first
  year
• nervous system fails to develop normally
• mental retardation results
• If T4 concentrations decline before puberty
• normal skeletal development will not continue

115
Insulin

• Allows passage of glucose and amino acids across
  cell membranes

116
Parathyroid Hormone (PTH) and Calcitriol

• Promote absorption of calcium salts for
  deposition in bone
• Inadequate levels causes weak and flexible bones

117
Reproductive Hormones

• Androgens in males, estrogens in females
• Stimulate cell growth and differentiation in
  target tissues
• Produce gender-related differences in
• skeletal proportions
• secondary sex characteristics

118
Insulin lowers the level of glucose in the blood,
and then glucagon causes glucose levels to rise.
What is this type of hormonal interaction called?

1. additive
2. antagonism
3. permissive
4. integrative

119
The lack of which hormones would inhibit skeletal
formation?

1. GH, thyroid hormone, PTH, gonadal hormones
2. prolactin, FSH, LH, GH
3. thyroid hormone, melatonin, PTH, calcitonin
4. GH, TSH, ACTH, FSH

120
Why do levels of GH-RH and CRH rise during the
resistance phase of the general adaptation
syndrome?

1. to bolster immune response
2. to decrease excess blood volume
3. to increase needed supplies of blood glucose
4. to heighten sensory perceptions

121
Generaladaptation syndrome.
122
General Adaptation Syndrome (GAS)

• Also called stress response
• How bodies respond to stress-causing factors

Figure 1818
123
General Adaptation Syndrome (GAS)

• Is divided into 3 phases
• alarm phase
• resistance phase
• exhaustion phase

124
Alarm Phase

• Is an immediate response to stress
• Is directed by ANS
• Energy reserves mobilized (glucose)
• Fight or flight responses
• Dominant hormone is epinephrine

125
7 Characteristics of Alarm Phase

• Increased mental alertness
• Increased energy consumption
• Mobilization of energy reserves (glycogen and
  lipids)
• Circulation changes
• increased blood flow to skeletal muscles
• decreased blood flow to skin, kidneys, and
  digestive organs
• Drastic reduction in digestion and urine
  production
• Increased sweat gland secretion
• Increases in blood pressure, heart rate, and
  respiratory rate

126
Resistance Phase

• Entered if stress lasts longer than few hours
• Dominant hormones are glucocorticoids
• Energy demands remain high
• Glycogen reserves nearly exhausted after several
  hours of stress

127
Effects of Resistance Phase

1. Mobilize remaining lipid and protein reserves
2. Conserve glucose for neural tissues
3. Elevate and stabilize blood glucose
   concentrations
4. Conserve salts, water, and loss of K, H

128
Exhaustion Phase

• Begins when homeostatic regulation breaks down
• Failure of 1 or more organ systems will prove
  fatal
• Mineral imbalance

129
Aging Related Changes

• Very little change in most hormone levels
• Adverse effects due to changes in target tissue
• Prevent reception or response to hormone
• Gonads decrease in size and hormone production

130
Review Endocrine System

• Provides long-term regulation and adjustments of
  homeostatic mechanisms
• fluid and electrolyte balance
• cell and tissue metabolism
• growth and development
• reproductive functions
• assists nervous system response to stressful
  stimuli through general adaptation syndrome

131
SUMMARY

• Paracrine communication
• Endocrine communication
• Classes of hormones
• amino acid derivatives
• peptide hormones
• lipid derivatives, including steroid hormones and
  eicosanoids
• Secretion and distribution of hormones
• Endocrine reflexes
• Hypothalamus regulation of the endocrine system
• The pituitary gland
• the anterior lobe
• the posterior lobe

132
SUMMARY

• Releasing hormones
• Inhibiting hormones
• The thyroid gland
• thyroid follicles
• thyroid hormones
• The parathyroid glands
• The adrenal glands
• the adrenal cortex and adrenal medulla
• The pineal gland
• The pancreas
• the pancreatic islets
• insulin and glucagons

133
SUMMARY

• Endocrine tissues in other systems
• Hormonal interaction
• Role of hormones in growth
• Hormonal response to stress
• Effects of hormones on behavior
• Effects of aging on hormone production