Transcript Chapter 9 The Endocrine System

Chapter 9 The Endocrine
System
Biology 112
Tri-County Technical College
Pendleton, SC
Hormones are flowing…
Hormones are chemical substances
secreted into extracellular fluid that
regulate activity of other cells
Hormones circulate to all organs but
affect ONLY certain tissue cells/organs
referred to as its TARGET
CELLS/ORGANS
Target MUST have specific protein
receptors on its plasma membrane or
interior to which hormone can attach
Hormones, cont.
Reproduction, growth & development, body’s
defenses against stressors, electrolyte, water,
& nutrient balance of blood, regulating
metabolism & energy balance
Typically one or more of following occur as
result of hormone action:
changes in PM permeability/electrical state
synthesis of proteins or regulatory molecules
activation/inactivation of enzymes
stimulation of mitosis/meiosis
Getting there
Steroid hormones able to diffuse across PM
Nonsteroid hormones require membrane
receptors and utilize signal-transduction
mechanism (second messengers)
One of three mechanisms responsible for
stimulating endocrine gland
HORMONAL
HUMORAL
NEURAL
Hormonal Action, Visual
Stimulation, Visual
Been there…done that
Hormonal secretion triggered by some
internal/external stimulus
Rising hormone levels inhibit further
hormone release even while promoting
responses in target organs
WOW!!! Negative feedback model again
**End product controls the rate of the
reaction or event
Endocrine Glands
Endocrine glands (ductless) release
their secretions into blood or lymph
Endocrine glands have a very rich blood
supply
Hypothalamus, pituitary, thyroid,
parathyroid, adrenal, pineal, thymus,
pancreas, and gonads (testes/ovaries)
Location, Visual
Pituitary Gland
Pituitary gland about the size of a grape and
hangs by a stalk from inferior surface of
hypothalamus of the brain
surrounded by “turk’s saddle” of sphenoid bone
Has two functional lobes
Anterior pituitary arises from glandular tissue
Posterior pituitary arises from nervous tissue
Anterior hormones: growth hormone (GH),
prolactin (PRL), follicle-stimulating (FSH),
luteinizing (LH), Thyroid stimulating (TSH)
and Adrenocorticotropic (ACTH)
Pituitary, cont.
Growth hormone and prolactin exert their
major effects on nonendocrine targets
FSH, LH, TSH, and ACTH are all TROPHIC
hormones
Trophic hormone is hormone that regulates
the activity of another ENDOCRINE gland
All anterior pituitary hormones are
proteins/peptides; act through 2nd
messengers; are regulated by hormonal
stimuli, and operate via negative feedback
mechanism (in most cases)
Anterior Pituitary, Visual
Growth Hormone
GH is protein-sparing & anabolic
hormone causing amino acids to build
into proteins
Stimulates MOST target cells to grow in
size and divide
Causes fats to be broken down for
energy
Spares body’s supply of glucose thereby
helping to maintain blood sugar
homeostasis
Pituitary Abnormalities
Hyposecretion of GH during childhood
leads to pituitary dwarfism
body proportions fairly normal but person is
living miniature (adult height ~ 4 feet)
Hypersecretion during childhood leads to
gigantism
individual becomes extremely tall (8-9 feet)
If hypersecretion occurs after long bone
growth ended = acromegaly
lower jaw and bony ridges under eyebrow enlarge
as does hands and feet; thickening of soft tissue
leads to coarse/malformed facial features
Most hypersecretion of endocrine glands
caused by tumors of affected gland
Prolactin
Abbreviated as PRL
Protein hormone whose only known
target in humans is the breast
After childbirth, it stimulates and
maintains milk production by mother’s
breasts
Its function is males is NOT known
Same song, different verse…
Adrenocorticotrophic hormone =
ACTH
Regulates activity of the cortex portion
of the adrenal gland
Thyroid-stimulating hormone =
TSH
TSH also known as thyrotropic
hormone (TH)
Influences growth and activity of the
thyroid gland
Follicle Stimulating Hormone
Abbreviated as FSH
Regulates activity of gonads
(ovaries/testes)
In females, FSH stimulates follicle
development in ovaries
As follicles mature, they produce estrogen
and eggs are readied for ovulation
In males, FSH stimulates sperm
development by the testes
Luteinizing Hormone
Abbreviated LH
In females, LH triggers ovulation of egg from
ovary
Also causes ruptured follicle to become
corpus luteum
LH then stimulates corpus luteum to produce
progesterone and some estrogen
In men, LH is referred to as interstitial cellstimulating hormone (ICSH)
stimulates testosterone production by interstitial
cells
Pituitary and Sterility
Hyposecretion of FSH or LH leads to
sterility in both males and females
Hypersecretion does NOT appear to
cause any problem(s)
Some drugs used to produce fertility
stimulate release of FSH and LH
Multiple births fairly common after their
administration
Anterior
Pituitary/Hypothalamus
Pituitary used to be called “master gland”
Release of pituitary’s hormones controlled by
releasing and inhibiting hormones
produced by hypothalamus
Hypothalamus releases these regulatory
hormones into portal circulation which
connects blood supply of hypothalamus with
that of anterior pituitary
Posterior Pituitary
Posterior pituitary (neural tissue) STORES two
hormones produced by hypothalamus
Oxytocin and antidiuretic hormone (ADH)
Both are peptide hormones
Produced in hypothalamus
Transported along axons of hypothalamic
neurosecretory cells to posterior pituitary for
storage
Released into blood in response to nerve
impulses from the hypothalamus
Posterior Pituitary, Visual
OH!!! for Oxytocin
Released in significant amounts only during
childbirth and in nursing women
Stimulates powerful contractions of the
uterine muscles during labor, sexual relations,
and when female is nursing
Also causes milk ejection (letdown reflex) in
nursing women
Natural/synthetic oxytocic drugs (pitocin)
used to induce/hasten labor, stop postpartum
bleeding, and stimulate milk ejection reflex
Antidiuretic Hormone
Diuresis is urine production
Antidiuretic is chemical that inhibits and/or
prevents urine production
ADH causes kidneys to reabsorb more water
from forming urine
Results in urine volume DECREASE and blood
volume INCREASE
In large amounts, ADH increases blood
pressure by causing constriction of arterioles
(small arteries)
ADH sometimes called VASOPRESSIN
Diabetes Insipidus
Hyposecretion of ADH leads to
condition of excessive urine output
called diabetes insipidus
Individuals with this problem are
continually thirsty and drink large
amounts of water
Thyroid Gland
Thyroid located at base of throat, inferior to
Adam’s apple where easily palpated
Large gland of two lobes joined by central
mass called isthmus
Internally, composed of hollow structures
called follicles which store sticky colloidal
material
Thyroid iodine-containing hormone derived from
colloid
Produces 2 active hormones: T3 and T4
Also produces calcitonin (thyrocalcitonin)
Thyroid, Visual
T3 and T4
Thyroid hormone (body’s major
metabolic hormone) actually two iodinecontaining hormones
Tetraiodothyronine (thyroxine or T4)
Triiodothyronine (T3)
Thyroxine (T4) is major hormone
secreted by thyroid follicles
Most T3 formed at target tissues by
conversion of T4 to T3
The T’s, cont.
Both are very similar—two tyrosine
amino acids linked by either 3 or 4
iodine atoms
Controls rate at which glucose is
converted to chemical energy and heat
EVERY cell in body is target for thyroid
hormone
Also important for normal tissue growth
and development especially in
reproductive and nervous systems
Remember it well…
GOITER is enlargement of thyroid gland
caused by diet deficient in iodine
TSH keeps calling for thyroxine and thyroid
gland continues to enlarge to make more…
Only peptide part of molecule is made but
without iodine it is NONFUNCTIONAL
fails to provide negative feedback to inhibit TSH
release
Uncommon in US today because of iodized
salt
Cretinism, Myxedema, and
more
Cretinism results in dwarfism where
adult body proportions remain childlike
Caused by hyposecretion of throxine in
early childhood
Untreated leads to mental retardation,
scanty hair, and very dry skin
Discovered early, HR can prevent signs
and symptoms of deficiency
C, M, and more…cont.
Myxedema caused by hyposecretion of
thryoxine during adulthood
Mental and physical sluggishness, puffiness of
face, fatigue, poor muscle tone, low body
temperature, obesity, and dry skin
Oral thyroxine is prescribed
HYPERTHYROIDISM usually results from
tumor of thyroid gland = extreme
overproduction of thyroxine
C, M, and more…cont.
High metabolic rate, intolerance of heat, rapid
heart beat, weight loss, nervous and agitated
behavior, & inability to relax
Grave’s disease is one form of
hyperthyroidism
May also cause thyroid to enlarge & eyes to
bulge or protrude anteriorly in condition
called exophthalmos
Calcitonin
Calcitonin (thyrocalcitonin) is second major
hormone of the thyroid gland
Decreases blood calcium levels by causing
calcium to be deposited in bone
Antagonistic to parathyroid hormone
Made by “C cells” found in connective tissue
between follicles
Released into blood in response to >ing levels
of blood calcium
Believed calcitonin production is meager or
absent in elderly
Calcitonin is hypocalcemic hormone; <
calcium in blood
Calcium Homeostasis, Visual
Parathyroid Glands
Are tiny masses of glandular tissue found on
posterior surface of thyroid gland
Typically 2 on each lobe (8 reported)
Secrete parathyroid hormone (PTH) or
parathormone
**Most important regulator of calcium ion
(Ca2+) in blood
Calcium levels drop below certain level,
parathyroids release PTH which stimulates
bone destruction cells (osteoclasts)
Parathyroids, cont.
Osteoclasts break down bone matrix
and increase blood levels of calcium
**PTH is hypercalcemic hormone
because it acts to > blood levels of
calcium
Another example of negative feedback
PTH also stimulates kidneys and
intestine to absorb MORE calcium from
forming urine and foodstuff
Hypo versus Hypercalcemia
Hypocalcemia can be caused by
hypoparathyroidism (poor diet, lack of vitamin
D, and/or renal failure)
Blood calcium levels drop too low, neurons
become extremely irritable/overactive
Neurons deliver impulses to muscles at such
rapid rate that muscles go into uncontrollable
spasms (tetany)
Convulsions, intestinal cramps, weak
heartbeat, cardiac arrhythmias, osteoporosis
(what a lesson)
Hypo/Hyper, cont.
Hypercalcemia results when calcium
blood levels become too high
Can be caused by hyperparathyroidism
(cancer, vitamin D toxicity, calcium
supplement overdose)
Confusion, muscle pain, cardiac
arrhythmias, kidney stones, fatigue, and
calcification of soft tissue
Is it catching…????
Adrenal Glands
Adrenal glands curve over top of kidneys
Each is structurally/functionally two endocrine
glands
Like pituitary, the adrenal has glandular
(cortex) and neural (medulla) parts
Central medulla enclosed by adrenal cortex
which contains three separate layers of cells
Adrenal cortex produces 3 major groups of
STEROID hormones called corticosteroids
Adrenal Glands, cont.
Mineralocorticoids, Glucocorticoids, and
sex hormones
Mineralocorticoids, mainly aldosterone,
produced by outermost adrenal cortex layer
Important in regulating mineral (salt) content
of blood—especially [ ] of sodium and
potassium ions
Their target is kidney tubules that selectively
reabsorb minerals or allow them to be flushed
out in urine
Adrenal glands, cont.
Blood levels of aldosterone >, kidney tubule
cells reclaim >ing amounts of sodium ions
Allows more potassium ions to be excreted in
urine
When sodium reabsorbed, water follows
Results in >ed blood volume and blood
pressure
Mineralocorticoids help regulate both water
and electrolyte balance in body fluids
Aldosterone Release, Visual
Adrenals and Glucocorticoids
Cortisone & Cortisol are 2 glucocorticoids
produced by MIDDLE cortex layer
Promote normal cell matabolism and help
body resist long-term stressors primarily by
>ing blood glucose levels
High levels of glucocorticoids in blood prompt
body cells to convert fats and proteins to
glucose
Glucocorticoids are hyperglycemic
hormones
Glucocorticoids cont.
Help control inflammation by <ing
edema
Reduce pain by inhibiting pain-causing
molecules called prostaglandins
Often prescribed for patients with
rheumatoid arthritis to suppress
inflammation
**Glucocorticoids released from adrenal
cortex in response to rising blood levels
of ACTH
Adrenals and Sex hormones
Regardless of gender, adrenal cortex
produces small amounts of both male
and female sex hormones throughout
life
Innermost layer of adrenal cortex
produces the bulk of the adrenalproduced sex hormones
Androgens (male hormones) and some
estrogen also produced
Addison’s Disease
Addison’s disease caused by hyposecretion
of adrenal cortex hormones
Major sign is peculiar bronze skin tone
Aldosterone levels <; sodium & water lost
from body = problems with electrolytes and
water balance
causes muscles to become weak/shock possible
Low levels of glucocorticoids results in
hypoglycemia = lessened ability to cope with
stress (burnout) and suppression of immune
system & increased susceptibility to infection
Complete lack of glucocorticoids=auf
wiedersehen
Cushing’s Syndrome
Hypersecretion usually result of tumor
If tumor in middle cortex region, Cushing’s
syndrome occurs
Excessive output of glucocorticoids results in
“moon face” and appearance of “buffalo
hump” of fat on upper back
Also high BP, hyperglycemia, and possible
diabetes, weakening of bones, and severe
depression of the immune system
Trying things on…
Tumor in zona reticularis of cortex layer can
cause excessive production of either
androgens or estrogen
If androgen >s dramatically, produces
symptoms of adrenogenital syndrome
In women=gradual development of male
secondary sexual characteristics (body and
facial hair, adipose tissue distribution, and
muscular development)
In estrogen >s, leads to gynecomastia
Male develops female secondary sexual
characteristics
ANS and Adrenal Medulla
Adrenal medulla (like posterior pituitary)
develops from neural tissue
When stimulated sympathetic NS neurons, its
cells release 2 similar hormones
Hormones called catecholamines
Epinephrine (adrenaline) &
norepinephrine (noradrenaline)
Sympathetic division called “fight or flight
response” division of ANS
> heart rate, blood pressure, blood glucose
levels and dilation of small passageways of
lungs
Body better able to deal with short-term
stressor
The Pancreas
Pancreas located close to stomach in abdominal
cavity and is MIXED gland (both endocrine &
exocrine)
Tiny masses of hormone-producing cells
scattered among enzyme-producing cells
pancreatic islets (islets of Langerhans)
Islet cells produce insulin & glucagon
Both help regulate sugar (glucose) in blood but
in opposite ways
Beta cells produce insulin and Alpha cells
produce glucagon
Pancreas, Visual
Release and Function of
Insulin
High blood levels of glucose stimulate
beta cells to produce insulin
Insulin acts on ALL body cells and >s
their ability to transport glucose across
their PMs
Once inside, glucose used for energy or
converted to glycogen or fat for storage
Insulin sweeps glucose from
blood=hypoglycemic
Blood glucose levels fallinsulin release
ends (classic negative feedback)
Insulin, cont.
Insulin is ONLY hormone that <s blood
glucose levels
It is absolutely necessary for use of
glucose by body cells
Glucagon, glucocorticoids, and
epinephrine increase blood glucose
levels and are hyperglycemic
Blood Glucose Regulation
Diabetes Millitus
Condition in which blood glucose levels rise to
600 mg/100 ml compared to normal of 80100 mg/100 ml because of lack of insulin
Kidney tubules cannot absorb glucose fast
enough so spills into urine
As glucose flushes from body, water follows
leading to dehydration
Cells cannot use glucose so fats/proteins
broken down for energy=decline in body
weight
Loss of body proteins=decreased ability to
fight infections
Diabetes Millitus, cont.
Use of large amts. of fat for energy results in
ketones in blood=acidosis as blood becomes
more acidic
Unless corrected=death
3 cardinal signs of diabetes milliuts
Polyuria (excessive urination)
Polydipsia (excessive thrist)
Polyphagia (hunger)
Mild cases (Type II/adult onset) treated with
special diets/oral meds to stimulate islets
Type I (juvenile/brittle) requires insulin injections
Glucagon Function/Release
Glucagon released by alpha cells of
islets
Release stimulated by LOW blood levels
of glucose
Action is basically hyperglycemic
Primary target organ is liver where
stimulates breakdown of glycogen to
glucose and its release into the blood
Pineal Gland/Body
Small, cone-like gland found in roof of
3rd ventricle of brain
Secretes melatonin; >s at night; <s
during day
Plays role in body’s day and night cycle
May be related to mating behavior and
coordination of hormones of fertility
Inhibits sexual maturation occurrence
during childhood
Thymus Gland
Located upper thorax, posterior to sternum
Large in infants, decreases in size during
adulthood—by old age just fibrous connective
tissue and fat
Produces thymosin which programs T cells
In childhood, is “incubator” for maturation of
T lymphocytes (WBCs important in immunity)
Ovaries
Paired, almond shaped organs located in pelvic
cavity
Produce estrogens and progesterone
Estrogens (estrone & estradiol) produced by
Graafian follicles of ovary & stimulate
development of secondary sexual characteristics
Work with progesterone to prepare uterus to
receive fertilized egg
results in cyclic changes = menstrual cycle
Ovaries, cont.
Estrogens help maintain pregnancy and
prepare breasts for lactation
placenta source at this time and not ovaries
Progesterone (with estrogen) bring about
menstrual cycles
During pregnancy, quiets muscles of
uterus to prevent abortion
Also assists in preparing breasts for
lactation
Ovaries, cont.
Progesterone also secreted by corpus
luteum
CL produces estrogen/progesterone in
>ing amounts
Ovaries stimulated to release estrogen
and progesterone in cyclic way by
anterior pituitary gonadotropic
hormones of FSH and LH
Testes
Testes produce male sex hormones (androgens)
of which testosterone is most important
Testosterone produced by interstitial cells of
testes and causes development of adult male
sex characteristics
Promotes growth/maturation of reproductive
system
Promotes development of SSC’s such as growth
of beard, development of heavy bones/muscles,
lowering of voice
Stimulates male sex drive
Testes, cont.
Testosterone necessary for continuous
sperm production during adulthood
Production is stimulated by LH from
anterior pituitary gland
It’s the testosterone that killing us,
guys, but what a Catch 22!!!
Placenta
Formed temporarily in uterus of pregnant
woman
Has role in respiratory, excretory, and nutrition
delivery system for fetus
Also produces hormones that help maintain
pregnancy
Human chorionic gonadotropin (hCG)
produced by conceptus and then by fetal part of
placenta
Found only in urine of pregnant women/is basic
for EPTs (monoclonal antibody technology)
Placenta, cont.
hCG stimulates corpus luteum to continue
producing estrogen/progesterone so uterine
lining NOT sloughed off
In 3rd month, placenta assumes job of
production and ovaries become inactive
Human placental lactogen (hPL) works with
estrogen/progesterone to prepare breasts for
lactation
Relaxin causes mother’s pelvic ligaments &
pubic symphysis to relax and become more
flexible
Eases birth passage
Old dogs/children/WM wine
Endocrine system seems to work smoothly
until old age
Late middle age = menopause for women
Estrogen deficiency can lead to
arteriosclerois, osteoporosis, decreased
skin elasticity, changes in operation of
sympathetic nervous system, fatigue,
nervousness, and mood changes
For most part, men produce testosterone
throughout life
Watermelon wine, cont.
Efficiency of endocrine system gradually
declines in old age
Target organs become less productive
GH declines = muscle atrophy
Most older people = hypothyroid
Pineal gland calcifies and immune system
becomes compromised
Decline in insulin production occurs and
adult-onset diabetes common in elderly