Transcript Endocrine System - Chiropractor Manhattan | Chiropractor

Dr. Michael P. Gillespie
Mediator Molecules in Nervous &
Endocrine Systems
 The nervous system utilizes neurotransmitters to
control body functions.
 The endocrine system utilizes hormones to control
body functions.
Site Of Mediator Action In Nervous
& Endocrine Systems
 The neurotransmitters perform their action close to
the site of release.
 The hormones usually perform their action far from
their site of release.
Types Of Target Cells In Nervous &
Endocrine Systems
 The nervous system acts upon muscle cells (smooth,
cardiac, and skeletal), glands, and other neurons.
 The endocrine system acts upon virtually all cells of
the body.
Time To Onset Of Action In
Nervous & Endocrine Systems
 In the nervous system, action typically occurs within
milliseconds of neurotransmitter release.
 In the endocrine system, action can take seconds to
days to occur after release of the hormone.
Duration Of Action In Nervous &
Endocrine Systems
 The actions tend to be briefer in duration in the
nervous system and longer in duration in the
endocrine system.
Comparison of Nervous and
Endocrine System Control
Characteristic
Nervous System
Endocrine System
Mediator Molecules
Neurotransmitters –
released locally
Hormones – delivered
throughout the body by
the blood
Site of Mediator Action
Close to site of release
Usually far from site of
release
Types of target cells
Muscle (smooth, cardiac,
and skeletal) cells, gland
cells, other neurons
Cells throughout the
body
Time to onset of action
Within milliseconds
Seconds – hours - days
Duration of Action
Typically briefer
(milliseconds)
Generally longer (seconds
to days)
Hormones
 A hormone is a mediator molecule that is
released in one part of the body but regulates
activity of cells in other parts of the body.
 Most hormones enter the interstitial fluid and
then the bloodstream.
 Hormones travel through the bloodstream to cells
throughout the body.
 Several neurotransmitters are also hormones (i.e.
norepinephrine).
Functions Of Hormones
 Help regulate:
 Chemical composition and volume of the internal
environment (interstitial fluid).
 Metabolism and energy balance.
 Contraction of smooth and cardiac muscle fibers.
 Glandular secretions.
 Some immune system activities.
Functions Of Hormones
 Control growth and development.
 Regulate operation of reproductive systems.
 Help establish circadian rhythms.
“Supersystem”
 The nervous and endocrine systems function together.
 Parts of the nervous system stimulate or inhibit the
release of hormones.
 Hormones can promote or inhibit the release of nerve
impulses.
Exocrine Glands Versus
Endocrine Glands
 Exocrine glands (Exo = outside) – secrete their
products into ducts that carry secretions into body
cavities, into the lumen of an organ, or to the outer
surface of the body.
 Endocrine glands – secrete their hormones into the
interstitial fluid surrounding the secretory cells.
Exocrine Glands Versus
Endocrine Glands
 Exocrine glands.
 Sudoriferous (sweat).
 Sebaceous (oil).
 Mucous.
 Digestive.
Exocrine Glands Versus
Endocrine Glands
 Endocrine glands.
 Pituitary.
 Thyroid.
 Parathyroid.
 Adrenal.
 Pineal.
 Other organs that secrete hormones:
 Hypothalamus, thymus, pancreas, ovaries, testes, kidneys,
stomach, liver, SI, skin, heart, adipose tissue, & placenta.
Endocrine System
 All endocrine glands and hormone secreting cells
comprise the endocrine system.
 Endocrinology (-logy = study of) is the study of the
science of endocrine glands, function of endocrine
glands, diagnosis of endocrine disorders and
treatment of endocrine disorders.
Hormone Receptors
 Hormones bind with specific receptors.
 Only target cells for a given hormone have specific
receptors that bind and recognize that hormone.
 A target cell can have anywhere between 2000 and
100,000 receptors for a particular hormone.
 Receptors are constantly being synthesized and
broken down to meet the needs of the body.
Down-regulation
 If a hormone is present in excess, the number of target
cell receptors may decrease.
 Down-regulation decreases the responsiveness of the
target cell to the hormone.
Up-regulation
 When a hormone (or neurotransmitter) is deficient,
the number of receptors may increase.
 Up-regulation makes a target cell more receptive to a
specific hormone.
Synthetic Hormones
 Synthetic hormones in the form of drugs can block the
receptors from naturally occurring hormones.
Circulating & Local Hormones
 Circulating hormones – pass from secretory cells that
make them into the interstitial fluid and then into the
blood.
 Most hormones are of this type.
 Local hormones – act locally on neighboring cells or
on the same cells that secreted them without first
entering the bloodstream.
Local Hormones
 Paracrines – (para = beside or near) act on neighboring
cells.
 Autocrines – (auto – self) act on the same cell that
secreted them.
Local Hormones
Example Of A Local Hormone
 Interleukin 2 (IL-2) is an example of a local hormone.
 It is released by helper T cells during immune responses.
 It acts on nearby immune cells (paracrine) and on itself
(autocrine).
 This generates more helper T cells and boosts the
immune response.
Duration of Local Versus
Circulating Hormones
 Local hormones usually are inactivated quickly.
 Circulating hormones linger longer.
 The liver eventually deactivates circulating hormones
and the kidneys excrete them.
Chemical Classes Of Hormones
 Lipid-soluble hormones.
 Steroid hormones.
 Thyroid hormones.
 Nitric oxide (NO).
Chemical Classes Of Hormones
 Water-soluble hormones.
 Amine hormones.
 Peptide hormones and protein hormones.
 Eicosanoid hormones.


Prostaglandins.
Leukotrienes.
Hormone Transport In Blood
 Most water-soluble hormones are transported in their
“free” form (not attached to plasma proteins).
 Most lipid-soluble hormones are bound to transport
proteins.
Hormone Receptors
 Lipid-soluble hormones – the receptors are located
inside the target cells.
 Water-soluble hormones – the receptors are located
within the plasma membrane of the target cells.
Action Of Lipid-soluble
Hormones
 Lipid soluble hormones turn specific genes of the
nuclear DNA on or off.
 This directs the synthesis of a new protein (often an
enzyme).
 These new proteins alter the cells activity.
Action Of Water-soluble
Hormones
 Water soluble hormones are the first messenger. They
activate the second messenger i.e. cyclic AMP (cAMP).
 This initiates a cascade of events within the cell that
produces millions of enzymes to catalyze reactions.
 Phosphodiesterase inactivates cAMP.
Lipid Soluble Hormones
Water Soluble Hormones
Summary of Hormones By Class
 Refer to Table 18.2
Responsiveness Of The Target
Cell
 The responsiveness of the target cell depends upon the
following:
 The hormone’s concentration.
 The number of the hormone receptors on the target cell.
 Influences exerted by other hormones.
Influences Of Other Hormones
 Permissive effect – the action of a 2nd hormone is
required for the 1st hormone to take effect.
 Thyroid hormones (2nd) allow epinephrine to stimulate
lipolysis.
Influences Of Other Hormones
 Synergistic effect – the sum of the actions of the 2
hormones is greater than either hormone
individually.
 Estrogens and FSH promote development of oocytes.
 Antagonistic effect – one hormone opposes the
actions of another.
 Insulin promotes synthesis of glycogen and glucagon
stimulates breakdown of glycogen.
Control Of Hormonal Secretion
 Hormone secretion is regulated by:
 Signals from the nervous system.
 Chemical changes in the blood.
 Other hormones.
Hypothalamus
 Serves as a major integrating link between the nervous
system and the endocrine system.
 Painful, stressful, and emotional experiences cause
changes in hypothalamic activity.
 Synthesizes at least 9 different hormones.
 Regulates the pituitary gland.
Pituitary Gland (hypophysis)
 Synthesizes at least 7 different hormones.
 Release of anterior pituitary hormones is stimulated
by releasing hormones and suppressed by inhibiting
hormones from the hypothalamus.
 Attaches to the hypothalamus by a stalk, the
infundibulum (= a funnel).
Types Of Anterior Pituitary Cells
& Their Hormones
 Somatotrophs – secretes human growth hormone
(hGH) or somatotropin, which stimulates tissues to
secrete insulinlike growth factors (IGFs).
 Thyrotrophs – secrete thyroid-stimulating hormone
(TSH) or thyroptropin.
Types Of Anterior Pituitary Cells
& Their Hormones
 Gonadotrophs – secrete follicle-stimulating hormone
(FSH) and luteinizing hormone (LH) which act on the
gonads.
 They stimulate the secretion of estrogen and
progesterone and the maturation of oocytes in the
ovaries.
 They stimulate the secretion of testosterone and sperm
production in the testes.
Types Of Anterior Pituitary Cells
& Their Hormones
 Lactotrophs – secrete prolactin (PRL), which initiates
milk production.
 Corticotrophs – secrete adrenocorticotropic hormone
(ACTH) or corticotropin, which stimulates the adrenal
cortex to secrete glucocorticoids.
Tropic Hormones (tropins)
 Hormones that influence another gland are called
tropic hormones or tropins.
Control Of Secretion By The
Anterior Pituitary
(adenohypophysis)
 The hypothalamus secretes five releasing hormones
and two inhibiting hormones.
 Negative feedback loops from hormones released from
target glands decrease the release from the anterior
pituitary gland.
Human Growth Hormone &
Insulinlike Growth Factors
 The main function of hGH is to promote synthesis
of IGFs.
 IGFs cause cells to grow and multiply.
 They help to maintain the mass of muscles and
bones.
 They promote healing of injuries and tissue repair.
 They enhance lypolysis in adipose tissue.
Release Of hGH
 Two hypothalamic hormones control the release of
hGH:
 Growth hormone releasing hormone (GHRH).


Stimulated by hypoglycemia.
Inhibited by hyperglycemia.
 Growth hormone inhibiting hormone (GHIH).


Stimulated by hyperglycemia.
Inhibited by hypoglycemia.
Thyroid-stimulating Hormone
 Thyroid-stimulating hormone (TSH) stimulates
the synthesis and secretion of two thyroid
hormones:
 Triiodothyronine (T3).
 Thyroxine (T4).
 Thyrotropin-releasing hormone (TRH) from the
hypothalamus controls TSH secretion.
 Negative feedback from T3 and T4 inhibits the
release of TRH.
Follicle-stimulating Hormone
 FSH initiates the development of ovarian follicles and
stimulates follicular cells to secrete estrogens in
females.
 FSH stimulates sperm production in the testes in
males.
Follicle-stimulating Hormone
 Gonadotropin-releasing hormone (GnRH) from the
hypothalamus stimulates FSH release.
 Estrogens in females and testosterone in males
suppresses release of GnRH and FSH through negative
feedback systems.
Luteinizing Hormone (LH)
 In females LH triggers ovulation.
 FSH and LH work together to stimulate the release of
estrogen.
 In males, LH stimulates the release of testosterone
from the testes.
Prolactin (PRL)
 Initiates and maintains secretion of milk by the
mammary glands.
 By itself, prolactin has only a weak effect.
Prolactin (PRL)
 Only with the effects of estrogens, progesterone,
glucocorticoids, hGH, thyroxine and insulin does
PRL bring about milk.
 The hypothalamus secretes both inhibitory and
excitatory hormones that regulate PRL secretion:
 Prolactin-inhibiting hormone (PIH).
 Prolactin-releasing hormone (PRH).
Hypersecretion Of Prolactin
 In males – erectile dysfunction.
 In females – galactorrhea (inappropriate lactation) and
amenorrhea (absence of menstrual cycles).
Adrenocorticotropic Hormone
(ACTH)
 ACTH controls secretion of cortisol and other
glucocorticoids by the cortex of the adrenal gland.
 Corticotropin-releasing hormone (CRH) from the
hypothalamus stimulates secretion of ACTH.
 Glucocorticoids cause inhibition of CRH and ACTH
through negative feedback systems.
Principle Actions Of Anterior
Pituitary Hormones
 Table 18.4 page 655.
Posterior Pituitary
(neurohypophysis)
 The posteror pituitary does not synthesize any
hormones; however, it does store and release two
hormones from the hypothalamus:
 Oxytocin (OT).
 Antidiuretic hormone (ADH) a.k.a. vasopressin.
Oxytocin
 During delivery, oxytocin enhances contraction of
smooth muscle cells in the wall of the uterus.
 After delivery, oxytocin stimulates milk ejection
(“letdown”) from the mammary glands in response to
the suckling infant.
Antidiuretic Hormone (ADH)
 ADH is a substance that decreases urine production.
 ADH causes the kidneys to return more water to the
blood.
Summary Of Posterior Pituitary
Hormones
 Table 18.5 page 658.
Thyroid Gland
 Located inferior to the larynx (voice box).
 Right and left lateral lobes connected by an
isthmus.
 Anterior to the trachea.
 Highly vascular.
 Consists of thyroid follicles (spherical sacs).
 The walls of each follicle contain follicular cells,
which extend into the lumen of the follicle.
Follicular Cells
 Produce two thyroid hormones (both are lipid
soluble).
 Thyroxine (tetraiodothyronine or T4).
 Triiodothyrronine (T3).
Parafollicular Cells
 Also known as C cells.
 Produce the hormone calcitonin (CT).
 Regulates calcium homeostasis.
 CT inhibits the action of osteoclasts.
 CT accelerates the uptake of calcium and phosphates
into the bone matrix.
Actions Of Thyroid Hormones
 Increase basal metabolic rate (BMR).
 Stimulates synthesis of Na+ / K+ ATPase
 Calorigenic effect.
 Helps to regulate body temperature.
 Regulate metabolism.
 Protein synthesis.
 Increase the use of glucose and fatty acids for ATP.
 Increase lypolysis.
Actions Of Thyroid Hormones
 Accelerate body growth, especially of the nervous
system.
 Enhances actions of the catecholamines
(norepinephrine and epinephrine). In
hyperthyroidism there is an increased heart rate,
more forceful heartbeats, and increased blood
pressure.
Parathyroid Glands
 Embedded into the posterior surface of the lateral
lobes of the thyroid gland.
 Superior and inferior parathyroid glands.
 Two kinds of epithelial cells.
 Chief (principal) cells – produce parathyroid hormone
(PTH) or parathormone.
 Oxyphil cell – function unknown.
Parathyroid Hormone
 Regulates levels of calcium, magnesium, and
phosphate ions in the blood.
 PTH increases the activity and # of osteoclasts.
 PTH stimulates the kidneys to synthesize calcitrol
(active form of vitamin D).
 Calcitrol stimulates increased absorption of Ca2+ from
the GI tract.
Adrenal Glands
 The paired adrenal (suprarenal) glands lie superior to
each kidney.
 Consists of the adrenal cortex (80-90% of the gland)
and the adrenal medulla.
 Highly vascularized.
Adrenal Gland Hormones
 Adrenal Cortex – steroid hormones.
 Adrenal Medulla – 3 catecholamine hormones.
 Norepinephrine.
 Epinephrine.
 Dopamine.
Aldosterone (Cortex)
 Regulates homeostasis of sodium ions and postassium
ions.
 Promotes the secretion of H+ in the urine to regulate
acid-base balance. Prevents acidosis (pH below 7.35).
 Renin-angiotensin-aldosterone (RAA) pathway
controls the secretion of aldosterone (Controls blood
pressure).
Glucocorticoids (Cortex)
 Regulate metabolism and resistance to stress.
 Cortisol (hydrocortisone).
 Corticostrerone.
 Cortisone.
 Low levels of glucocorticoids, mainly cortisol,
stimulate the hypothalamus to secrete
corticotropin-releasing hormone (CRH), which
promotes the release of ACTH from the anterior
pituitary, which in turn stimulates glucocorticoid
secretion.
Effects Of Glucocorticoids
 Increase the rate of protein breakdown.
 Stimulates glucose formation by breaking down
glycogen stores and through gluconeogenesis.
 Stimulates lypolysis.
Effects Of Glucocorticoids
 Resistance to stress by supplying ATP and raising BP in
cases of severe blood loss.
 Anti-inflammatory effects – inhibit WBCs (also slows
wound healing).
 Depression of immune responses (utilized with organ
transplant recipients).
Androgens (Cortex)
 The adrenal cortex secretes small amounts of
androgens (primarily dehydroepiandrosterone
DHEA).
 Assists in early growth of axillary and pubic hair in
both sexes.
 Contributes to libido and provides a source of
estrogens after menopause in females.
 ACTH stimulates its secretion.
Adrenal Medulla Hormones
 Epinephrine (adrenaline).
 Norepinephrine (noradrenaline).
 These two hormones augment the fight or flight
response.
 Increase the heart rate and force of contraction.
 Dilates the airways in the lungs.
 Shunts blood to heart, liver, skeletal muscles, and
adipose tissue.
 Increases blood levels of glucose and fatty acids.
Pancreatic Islets
 Both and endocrine and exocrine gland.
 Pancreatic islets (a.k.a. islets of Langerhans).
 4 major cell types:
 Alpha (A) cells – secrete glucagon.
 Beta (B) cells – secrete insulin.
 Delta (D) cells – secretes somatostatin (identical to
growth hormone inhibiting hormone).
 F cells – secrete pancreatic polypeptide.
Pancreatic Hormones
 Glucagon raises blood glucose levels.
 Insulin lowers blood glucose levels.
 Somatostatin inhibits both glocagon and insulin
release.
 Pancreatic polypeptide inhibits somatostatin
secretion, gallbladder contraction and secretion of
digestive enzymes by the pancreas.
Regulation Of Glucagon &
Insulin Secretion
 Hypoglycemia stimulates release of glucagon.
 Glucagon causes hepatocytes to convert glycogen to
glucose (glycogenolysis).
 Hyperglycemia inhibit release of glucagon.
Regulation Of Glucagon &
Insulin Secretion
 Insulin allows glucose to diffuse into cells, increases
amino acid uptake by cells, and increaes fatty acid
uptake by cells.
 This facilitates glucose conversion into glycogen
(glycogenesis), synthesis of proteins, and synthesis of
fatty acids (lipogenesis).
Gonads
 Ovaries (female gonads).
 Produce steroid hormones.
 Estrogens.
 Progesterone.
 Produce inhibin.
 Produce relaxin.
 Testes (male gonads).
 Produce testosterone (an androgen).
 Produce inhibin.
Females Sex Hormones
 Estrogen and progesterone along with FSH and LH
(from the anterior pituitary), regulate the menstrual
cycle, maintain pregnancy, and prepare the mammary
glands for lactation.
 Maintain the feminine secondary sex characteristics
(larger breasts and hips).
Inhibin & Relaxin
 Inhibin inhibits secretion of FSH.
 Relaxin increases the flexibility of the pubic symphisis
during pregnancy and helps dilate the cervix during
labor and delivery.
Male Sex Hormones
(Androgens)
 Testosterone regulates the production of sperm.
 Stimulates the production of male secondary sex
characteristics (beard growth and deepening of the
voice).
Pineal Gland
 A small endocrine gland attached to the roof of the
third ventrical of the brain.
 Secretes melatonin.
 More melatonin is released in darkness.
 Melatonin contributes to the body’s biological clock.
Seasonal Affective Disorder
(SAD)
 Thought to be due to overproduction of melatonin
during the winter months.
 Full spectrum bright-light therapy can assist with SAD
and jet lag.
Thymus
 Located behind the sternum between the lungs.
 Hormones produced – thymosin, thymic humoral
factor (THF), thymic factor (TF), amd thymopoeietin.
 Promotes the maturation of T cells and may retard the
aging process.