Download ENDOCRINE SYSTEM

ENDOCRINE SYSTEM
Objectives
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Describe the functions of the endocrine glands and
there hormones.
Describe the relationship between the hypothalmus
and the pituitary glands.
Identify the diagnostic tests used to determine
alterations in function in each of the endocrine
glands.
Compare hyper/hypo pituitarism (thyroidism,
parathyroidism, Addison’s, Cushing syndrome,
gigantism, dwarfism, SIADH, diabetes insipidus),
causes, clinical manifestations, management and
nursing interventions.
Identify teaching of patients needing steroid
therapy.
Required Reading
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Smeltzer & Bare (2004) Chapter 42
Readings on reserve: Unit IV Endocrine
http://arbl.cvmbs.colostate.edu/hbooks/pa
thphys/endocrine/index.html ( Excellent
web-site)
Endocrine System
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The endocrine system (endo, within) is
comprised of glands that secrete
hormones that are carried by the blood to
act on target tissue, regulating multiple
body processes. (ductless)
The endocrine, nervous and immune
system work together to create a precise
control over all body organs and metabolic
processes.
Hormones
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Defined as chemical substances
synthesized and secreted by a specific
organ or tissue, carried by the blood
stream to other cells or organs, to produce
a particularl regulatory effect.
(Lewis, Heitkemper & Dirksen, 2004)
Principal functions of the
endocrine system
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Maintenance of the internal environment in the
body (maintaining the optimum biochemical
environment).
Integration and regulation of growth and
development.
Control, maintenance and instigation of sexual
reproduction, including gametogenesis, coitus,
fertilization, fetal growth and development and
nourishment of the newborn.
The Endocrine & Nervous System
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The effects of hormones secreted by the
endocrine system affect the nervous
system and are in turn mediated by the
nervous system.
Example: adrenal medulla secretes
substances – epinephrine &
norepinephrine – that act as neuro
transmitters causing an effect of the
sympathetic nervous system.
Nervous system
The nervous system exerts
point-to-point control through
nerves, similar to sending
messages by conventional
telephone. Nervous control is
electrical in nature and fast.
Hormones travel via the
bloodstream to target cells
•The endocrine system sends its
hormonal messages to essentially
all cells by secretion into blood and
extracellular fluid. Like a radio
broadcast, it requires a receiver to
get the message - in the case of
endocrine messages, cells must
bear a receptor for the hormone
being broadcast in order to
respond.
Endocrine System & Immune
System
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There is also close
interaction between
the endocrine and
immune systems.
Example:
Glucocorticoids play a
major role in the
body’s response to
stress.
PRINCIPAL ENDOCRINE GLANDS
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Pituitary
Adrenal
Thyroid
Parathyroid Glands
Pancreas
Gonads (ovaries & testes)
(Hypothalamus link b/t nervous & endocrine systems)
Endocrine Glands Glands
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Pineal gland Secretes melatonin, a
hormone that helps regulate wakesleep cycle.
Hypothalmus: primary link btw.
the endocrine and nervous system.
It controls the release of pituitary
hormones.
Pituitary (anterior & posterior):
the “master gland b/c of its
importance.
Thyroid: Causes increase in
metabolic rate, increase in protein
and bone turnover.
Parathyroids: (4) regulate serum
calcium & phosphate.
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Thymus: Secretes hormones that maintain
and contribute to the production of peripheral
t-cell population.
Adrenal glands (cortex & medulla) Cortex
secretes glucocorticoids (cortisol),
mineralcorticoids (aldosterone) and
androgens.Medulla secretes substances that
act as neurotransmitters on sympathetic
nervous system.
Pancreas: endocrine and exocrine functions
Endocrine functions carried out by the Islets
of Langerhan which produce insulin and
glucagon (regulate blood glucose levels).
Exocrine cells secrete digestive enzymes into
the small intestine.
Gonads – female ovaries in abdomen; maletestes in scrotum
Other Structures Producing
Hormones
•Glands within the gastrointestinal tract
•Structures within the heart
and blood vessels (atrial
natriuretic peptide/factor (ANF
or ANP)
•Kidney: renin & erythropietin
A cell is a target for a hormone because is
has a specific receptor for that hormone
Most hormones circulate in blood, coming into contact
with essentially all cells. However, a given hormone
usually affects only a limited number of cells, which
are called target cells. A target cell responds to a
hormone because it bears receptors for the
hormone.
Hormones -Three classes based on
structure
1.
2.
3.
Steroid
Peptide (protein)
Amines
Mechanism of Protein Hormone
• Are water soluble
• Bind to cell
membrane receptors
on target tissue and
activate second
messenger within.
•Rapid response time
Peptide (Protein) Hormones
Steroid Hormones
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Steroid hormones
pass through the
plasma membrane
& do not require an
external receptor.
Hormones exert their actions in four
ways:
1. Maintenance of
internal environment
2. Regulation of energy
availability
3. Reproduction
4. Growth &
development
1. Maintenance of internal environment
is done through such activities as:
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Control of extracellular fluid
volume & BP
Electrolyte regulation
Maintenance of bone, muscle &
fat stores
2. Regulation of energy available
Control of the conversion of
calories to energy
 Storage of energy
 Mobilization of energy stores
when needed
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3. Reproduction
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Ovaries: produce ova
and hormones estrogen
& progesterone & are
controlled by pituitary.
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Testes: produce the
male reproductive cells
spermatozoa and the
male hormones
testosterone and inhibin
4. Growth and Development
Anterior pituitary secretes growth
hormone
 Review Peds
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Feedback Control
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Hormone concentration in the blood
stream is maintained at a fairly constant
level. When hormone levels rise, further
production of the hormones is inhibited.
When the hormone level drops, the rate of
production increases.
Feedback control
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Negative feedback is most common. The gland
itself responds by increasing or decreasing
hormone levels based on feedback from various
factors.
Positive feedback is less common: The increased
activity of hormone production and response
stimulates further production.
The regulation of hormone levels
depend mainly on the body’s negative
feedback system. For example:
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Elevated blood sugar levels stimulate the
release of insulin from the pancreas.
The insulin facilitates the transfer of sugar
from the blood to the cells
Low BS inhibits the release of more
insulin
Negative feedback is the corrective
action
Feedback Control of Hormone
Production
Feedback loops are used
extensively to regulate
secretion of hormones in
the hypothalamic-pituitary
axis. An important
example of a negative
feedback loop is seen in
control of thyroid
hormone secretion
Positive Feedback
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The regulation of hormone levels also
depend on the body’s positive feedback
system
Positive feedback systems amplify
changes rather than reversing them
For example: During labour, muscle
contractions becomes stronger &
stronger under the influence of oxytocin
Diseases of the endocrine system
are related to either:
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an excess or a deficiency of a specific
hormone or
to a deficit in the receptor site.
The thyroid and testes are the only glands
that can be examined directly
Knowledge of A&P together
with data from the history &
lab tests are essential in
assessing the endocrine
system.
Hypo and Hypersecretion of
Hormones
Hyper-secretion is production of too
much hormone
 Hypo-secretion is production of too
little hormone
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Endocrine Disorders & Psychiatric
Disturbances
Gland
Hypo
Hyper
Pituitary
Myxedema
Dwarfism
Sex Dysfunction
Diabetes Insipidus
Gigantism
Acromegaly
Sexual Dysfunction
Thyroid
Cretinism
Myxedema
Graves
Parathyroid
Tetany
Hypercalcemia
Adrenal
Addison’s Disease
Cushing Disease
Hyperaldosteronism
Pancreas
Diabetes Mellitus
Hypoglcemia
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Endocrine disorders may be associated
with a wide range of
psychological/psychiatric symptoms such
as depression, mania, paranoid disorders,
cognitive disturbances, hostility, &
irritability.
Nurses need to be aware that such
symptoms may precede other
manifestations of an endocrine disorder
and/or be early indications of its relapse.
Endocrine Disorders Commonly Manifesting
Psychiatric Characteristics
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Cushing’s Disease
Addison’s Disease
Hyperthyroidism
Hypothyroidism
Hyperprolactinaemia
Hyperparathyroidism
Hypothalamus and Pituitary as
Partners
HYPOTHALMUS
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Coordinates the
working of the
autonomic nervous
system & endocrine
system. Receives info
from cerebral
hemisphere, brain
stem, spinal cord,
autonomic &
peripheral nerves,
senses.
Hypothalamus Function
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Produces regulatory hormones that stimulate
the anterior pituitary (especially stimulating
or inhibiting): TRH, GHRH, GnRH, GH-IH,
CRH, PRH, PIH
Ultimately the hypothalamus can control
every endocrine gland in the body!
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Hypothalamic Hormones
Releasing Factor Anterior Pituitary
Target
Cells
TRH
TSH
thyroid
GHRH
GH
bone muscle
GH-IH
GH
bone muscle
GnRH
FSH, LH
ovaries, testes
CRH
ACTH
Adrenal cortex
PRH
Prolactin
mammary glands
PIH (dopamine inhibitor)
HYPOTHALMUS: SOME MAJOR
FUNCTIONS
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Autonomic nervous system
Secretion of pituitary hormones
Organization of body metabolism
Availability of energy foods such
as glucose
sleep & wakefulness
Temperature, thirst & water
regulation
Hunger & Appetite
Behavior - fear, rage, sexual
desire
Growth
Sexual reproduction
Hypothalamus Pituitary
Partners
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•Assess
Due to the unique interaction between
the hypothalamus and the pituitary
gland, hypothalamic dysfunction is
often associated with alterations
in pituitary function. Because the
hypothalamus is also responsible for
many homeostatic regulatory
functions, alterations can also occur in
behavior, temperature control &,
appetite.
Hypothalmus: disturbance in function may
be triggered by:
•Mental or emotional upset, grief
& worry
•Weight changes (drastic)
•Other causes - tumors,
•cerebral infections, trauma.