CHAPTER 5 CELL STRUCTURE Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings.
C h a p t e r 18 The Endocrine System Copyright © 2009 Pearson Education, Inc., publishing as...
-
Upload
randell-flowers -
Category
Documents
-
view
217 -
download
1
Transcript of C h a p t e r 18 The Endocrine System Copyright © 2009 Pearson Education, Inc., publishing as...
C h a p t e r
18
The Endocrine System
Copyright © 2009 Pearson Education, Inc.,publishing as Pearson Benjamin Cummings
Pages 603-635
Endocrine System Introduction
Composed of glands and tissues that secrete chemical regulators called hormones
Study of endocrine system is endocrinology
What do you call a doctor who specializes in diseases of the endocrine system?
Definitions
Hormones are chemicals regulatorsMost are secreted into the blood and
become circulating hormonesThey affect the functioning of other cells These “other cells” are called targets
Definitions
Hormones are specific for certain targets because hormones bind to specific receptors of target cells
Targets range from specific tissues to widespread tissues
Hormones Regulate
GrowthMetabolismFluid, electrolyte, and acid-base balanceReproductionBlood pressureand other processes such as heart rate,
digestion, etc.
Endocrine Glands and Tissues
Secrete hormones Examples Pituitary gland
(hypophysis) Thyroid gland Parathyroid glands Adrenal glands Pancreas Gonads Endocrine tissues
within other organs
Chemistry of hormones
Compounds that act as hormones are: Amino Acid Derivatives
Thyroid hormones Epinephrine, Norepinephrine and Dopamine
Peptide Hormones Small polypeptides and small proteins Glycoproteins
Chemistry of Hormones
Lipid DerivativesEicosanoids
Leukotrienes and prostaglandins
Steroids Estrogen, testosterone and cortisol
Hormone Secretion
Stimulus (another hormone, changes in blood chemistry or nerve stimuli)
Endocrine Gland
Target cell
Hormone secretion
Actions
Blood
Binds to Receptor------------
----------------Hormone
Regulation of Hormone Secretion
Hormone actions depend on cellular receptorsHormones that cannot enter the cell bind to
cell membrane receptorsHormone acts as “first messenger”Hormone-receptor complex simulates formation
of “second messenger” – usually cyclic-AMPSecond messenger produces hormones action
inside cell
Hormone Actions – Hormone Cannot Enter Cell
ATP
c-AMP – 2nd messenger
Hormone – 1st messenger
Membranes Receptor
Enzyme catalyzedreactions Actions
Most Hormones such as peptides and proteins work this way
Regulation of Hormone Secretion
Some Hormones can enter cellHormone binds to intracellular receptorHormone-receptor complex enters nucleusDNA segments (genes) activatedDNA codes for protein formationProtein produces hormone actions
Steroids and thyroid hormones work this way
Hormone Actions – Hormone Enters Cell
DNA in Nucleus
Protein Actions
Hormone Enters Cell
Intracellular Receptor
Regulation of Hormone Secretion
Hormone Concentration Affects Number of Receptors If hormone level high, receptor numbers decrease –
called down-regulation Cells become less sensitive to hormone
If hormone levels low, receptor numbers increase – called up-regulation
Cells become more sensitive to hormone
Up and down regulation help maintain endocrine homeostasis
Control of Secretion
Negative feed back Actions of Effector (Gland) decrease or inhibit
stimulus Actions are usually hormone secretions Most common control
Attempts to maintain normal levels of secretion Thermostat analogy
Positive feed back Actions of Effector increase or continue stimulus What are two examples?
Pituitary Gland (Hypophysis)
Small gland connected to hypothalamus
Two parts Anterior pituitary
(adenohypophysis) Posterior pituitary
(neurohypophysis) Infundibulum – a funnel-
shaped structure connecting the pituitary to the hypothalamus
anterior pituitary--------- -----posterior pituitary
hypothalamus
---------infundibulum
Pituitary Gland (Hypophysis)
Posterior pituitary Hormones produced by
hypothalamus and placed in posterior pituitary for secretion
Secretes two hormones Oxytocin (OT) Antidiuretic hormone (ADH)
Pituitary Gland
Anterior pituitary largest part Produces and secretes most
of the hormones Under indirect control of
hypothalamus Hypothalamus secretes
releasing hormones (RH) and inhibiting hormones (IH)
Reach anterior pituitary through hypophyseal portal circulation
Hormones of Anterior Pituitary
Human Growth Hormone (hGH) Targets most cells especially skeletal and muscle
tissue Actions
↑ rate of cell division for growth ↑ protein synthesis provides structure needed for
growth ↑ use of fat for energy, especially during prolonged
exercise ↑ rate of bone growth
Growth Hormone
Results in growth to adulthood and maintenance of skeleton and muscles in adults
May work directly on tissues, but mostly works indirectly by stimulating formation of insulin-like growth factors (IGF’s) in liver that then target muscle, skeletal and other tissues
Growth Hormone Imbalances
Pituitary dwarfism Caused by hyposecretion in childrenResults in small body
Giantism caused by hypersecretion in infants and children resulting in height of 7 to 8 feet
Acromegaly caused by hypersecretion in adults resulting in distorted features
Hormones of Anterior Pituitary
Thyroid stimulating hormone (TSH)Targets thyroid glandStimulates secretion of most thyroid
hormonesAdrenocorticotropic Hormone (ACTH)
Targets suprarenal (adrenal) cortexStimulates secretion of most steroids from
suprarenal glands
Hormones of Anterior Pituitary
Prolactin (PRL)Targets mammary glands Stimulates milk production in mammary
glands in concert with other hormonesGonadotropins
Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) target the ovaries and testes (gonads) and control female and male reproductive physiology
Hormones of the Posterior Pituitary
Oxytocin (OT) Mostly targets smooth muscles of
reproductive system of both sexes Actions in female
Labor (uterine) contractions Release of milk from mammary glands (milk
letdown)
Actions in male Contraction of smooth muscle in
reproductive tissue
Hormones of Posterior Pituitary
Antidiuretic Hormone (ADH) (vasopressin)Targets kidneys, sweat glands and
arteriolesActions
Causes kidneys and sweat glands to conserve water
Constricts arteriolesDo these actions affect blood pressure?
Thyroid Gland
Large butterfly-shaped gland in neck below voice box (larynx)
Has Two lobes connected by an isthmus
right lobe
left lobe
isthmus
Histology of Thyroid
Composed of many follicles filled with jelly-like (colloidal) thyroglobulin protein
• Thyroid hormones synthesized by follicle cells and stored in combination with thyroglobulin
Thyroglobulin
Thyroid Hormones Formation
Thyroglobulin protein made by follicular cells Thyroid hormones formed by addition of iodine
to the thryroglobulin protein 3 or 4 iodine atoms added to thyroglobulin
T3 (triiodothyronine) if 3 iodine atoms added
T4 (tetraiodothyronine or thyroxine) if 4 iodine atoms added
Thyroid Hormone Formation
Synthesis and secretion stimulated by anterior pituitary hormone TSH (thyrotropin)
When secreted, T3 and T4 combine with blood proteins for transport to target cells
Once in target cells, produce metabolic effects to provide energy and stimulate growth
Target Tissues and Actions of T3 & T4
Targets most tissues, but not allActions
ATP production and use of ATP for energy
Normal growthControl by negative feedback
Iodine is added to __________ to make T3 and T4.1. thyroxine binding globulin2. thyroglobulin3. albumin4. gamma globulin
Question
Imbalances of T3 & T4
Hyperthyroidism Too much T3 & T4
Grave’s disease most common form Symptoms
metabolic rate (MR) tachycardia body temperature (BT) anxiety & irritability goiter Exophthalmia (exophthalmos) heat intolerance weight loss
Imbalances of T3 & T4
Hypothyroidism Too little T3 & T4
Symptoms metabolic rate (MR) bradycardia body temperature (BT) lethargy goiter weight gain cold intolerance swollen face (Myxedema)
Imbalances of T3 & T4
Endemic goiter and iodine deficiency Insufficient dietary iodine to make T3 & T4
Endemic refers to ____________________
Lack of negative feedback causes overgrowth of thyroid
Goiter results
Parathyroid Glands
Thyroid and parathyroid glands contol blood calcium
Four parathyroid glands embedded in
back of thyroid gland
Control of Blood Calcium
Calcitonin (CT) from thyroid lowers blood calcium by adding it to bones
Parathyroid hormone from parathyroid glands increases blood calcium by removing it from bones
Suprarenal (adrenal) Glands
Located on top of kidneys Hormones adjust metabolism
and affect use of nutrients ionic balance energy consumption
Help maintain homeostasis against stress
Suprarenal Layers
Capsule Outer CT covering
Cortex – outer layer Threes zones Secretes steroids
Medulla – inner layer Secretes catecholamines
Suprarenal Histology
Cortex Secrete steroid hormones called corticoids Three Zones
Glomerular (outer) zone Cells in globular clusters Secretes mineralocorticoids such as aldosterone
Fascicular (middle) zone Cells form vertical elongated bundles Secrete glucocorticoids such as cortisol
Reticular (inner) zone Cells form irregular, net-like pattern Secrete some sex steroids in both sexes
Corticoids
Mineralocorticoids from glomerular zoneAldosterone most importantRegulates blood sodium, potassium
and acid – increases plasma sodium and decreases plasma potassium
Regulation affects fluid & electrolyte homeostasis
Principal one is cortisolActions include:
Mobilizing Body’s Resources to Resist Stress by
Protein breakdown (catabolism) for energy Formation of new glucose from amino
acids, lactic acid, and the glycerol part of fat molecules-gluconeogenesis
Glucocorticoids from Fascicular Zone
Glucocorticoids from Fascicular Zone
Actions include:Mobilizing Body’s Resources to Resist Stress
Conversion of excess glucose to glycogen (glycogenesis) for storage in liver-provides energy reserve
use of fat for energy assures glucose availability for brain
Maintaining bp by making blood vessels sensitive to vasoconstriction
Actions include:Reducing inflammation
Works with epinephrine (adrenaline) to reduce effects of inflammation.
Various steroids including hydrocortisone, cortisone, and synthetic steroids are used medically to reduce inflammation
Excess cortisol causes fat deposition in abdomen and face.
Control is by negative feedback
Glucocorticoids from Fascicular Zone
Imbalances of GlucocorticoidsAddison’s disease
Insufficient glucocorticoidsUsually caused by own antibodies attacking
suprarenal cortexSymptoms
Lack of energyWeight loss Inability to resist stressJohn F. Kennedy had it
Imbalances of Glucocorticoids
Cushing’s DiseaseExcessive glucocorticoid secretion
Usually caused by tumors in adrenals or elsewhere
Muscle wastingSpindly arms & legs
Fat redistributionLarge abdomen with stretch marksRounded faceFatty hump between shoulders
Which of the following is one of the actions of cortisol?
1. increased blood Calcium
2. blood glucose
3. gluconeogenesis
4. use of fat for energy
5. 2&3
6. 3&4
Question
Hormones of Suprarenal Medulla
Catecholamines - epinephrine (adrenaline) and norepinephrine (noradrenaline) Targets – most cells React quickly to stress by:
heart rate and strength blood flow to skeletal muscles, heart and brain dilation of airways (bronchodilation) fuel for energy-release of glucose from glycogen blood pressure
Suprarenal Medulla
Suprarenal medulla receives direct innervation from sympathetic nervous system develop from same tissue as Autonomic neurons
Hormones are sympathomimetic effects mimic those of sympathetic NS cause fight-flight behavior
Sympathetic stimulation increases hormone secretion by suprarenal medulla
Which hormone increases cell division, protein synthesis and the use of fat for energy?
1. prolactin
2. hGH
3. TSH
4. ACTH
Question
Pancreas
Large leaf-shapedLocated in curve of small intestine and
behind stomachBoth endocrine and exocrine
Endocrine part controls mostly blood sugar
Exocrine part secretes digestive enzymes
Anatomy of Pancreas
Five inches long Consists of head, body
& tail Most of pancreas is
exocrine and secretes digestive enzymes
Endocrine cells produce hormones that control blood sugar and affect metabolism and digestion
Histology of Pancreas
Exocrine acinar cells surround a small duct
Endocrine cells form Pancreatic Islet (Islets ofLangerhans)
1 to 2 million Islets
Contain four types of cells
Cell Types in the Pancreatic Islets
Alpha cells (20%) produce glucagonBeta cells (70%) produce insulinDelta cells (5%) produce somatostatinF cells (5%) produce pancreatic
polypeptideWill stress glucagon and insulin
secretion
Actions of Insulin
Insulin lowers blood glucose by: uptake of glucose into cellssynthesis of liver glycogen for storage-
glycogenesis
Insulin also protein & fat synthesis
Actions of Glucagon
Glucagon increases blood glucose by:Synthesis of glucose from amino acids in
liver-gluconeogenesisbreakdown of liver glycogen into glucose-
glycogenolysis release of glucose from liver into blood
Regulation of Glucagon & Insulin Secretion
High blood glucose after meal stimulates secretion of insulin and inhibition of glucagon
Low blood glucose when fasting stimulates release of glucagon and inhibition of insulin
Which of the following happens after you eat?
1. More glucose released into blood from liver
2. More glucose moves into cells
3. gluconeogenesis
4. breakdown (catabolism) of glycogen
Question
Diabetes Mellitus
Insulin unavailable for uptake of glucose into cells
Blood glucose becomes elevated – hyperglycemia
Diabetes Mellitus
Two Types:Type I (IDDM) or juvenile DM
Beta cells destroyed by own immune system
Insulin levels lowInsulin injections requiredUsually develops in people younger than 20
Diabetes Mellitus
Type II (NIDDM) or maturity onset DMMost common type (90%)Insulin may still be secreted but cells may
be less sensitive to itInsulin injections may not be requiredMostly in people over 35 who are obeseMay be controlled by diet