Endo Part 3
Can Males Lactate?
• Yes,– In humans, some men can breastfeed– In rats, some males breastfeed their young.– Receptors for both are similar– Hormones are similar in size and chemical
makeup – Have similar functions – ___________ can induce both to be secreted
• Anterior pituitary and hypothalamic secretions are controlled by the ______________organs they regulate.– Secretions are controlled by ___________ feedback
inhibition by target gland hormones.• ______________ feedback at 2 levels:
– The target gland hormone can act on the hypothalamus and inhibit secretion of ____________ hormones.
– The target gland hormone can act on the anterior pituitary and inhibit __________ to the releasing hormone.
Feedback Control of the Anterior Pituitary
Feedback Control of the Anterior Pituitary (continued)
• Short feedback loop:– Retrograde transport of
blood from anterior pituitary to the hypothalamus.
• Hormone released by anterior pituitary ___________secretion of releasing hormone.
• _______________ feedback effect:– During estrus,
______________ stimulates “___________ surge.”
Higher Brain Function and Pituitary Secretion
• Axis:– Relationship between _________ pituitary
and a particular target gland.• Pituitary-gonad axis.
• Hypothalamus receives input from higher brain centers.– Psychological stress affects:
• _______________ rhythms.• ________________ cycle.
______ adrenal glands:
Location:Immediately anterior to the kidneys, encased in a _________tissue capsule
The exact location relative to the kidney and the shape of the adrenal gland vary among species.
ADRENAL GLANDS
Adrenal Glands• History –
– Brown-Sequard (1856) adrenalectomy – fatal to dog– Cannon (1929) – fight or flight – adrenomedulla
• Paired organs that cap the kidneys.• Each gland consists of an outer _____________
and inner ________________.• In ____________ – no distinct cortex or medulla
Adrenal Glands (continued)
• Adrenal cortex:– Does not receive
________ innervation.– Must be stimulated
______________ (ACTH).
• Consists of 3 zones: – Zona __________ – Zona fasciculata. – Zona reticularis.
• Secretes ________________
Adrenals
Kidney
Posterior Pituitary Gland
Hypothalamus
AnteriorPituitary Gland
ACTH
Stress Circadian
rhythm
CRH
(-)
Glucocorticoids, Catecholamines, etc..
Glucocorticoids, Catecholamines, etc..
Muscle: Net loss of aminoAcids (glucose)
Liver: Deamination of
proteins into amino acids,
gluconeogenesis (glucose)
Fat Cells: Free fatty
acid mobilization
Heart rate: Increased
Immune system:
suppressed
Hypothalamopituitary adrenal axis
The adrenal gland has two distinct regions:
• An inner medulla: - _______________epinephrine (E) - norepinephrine (NE). - richly innervated by preganglionic sympathetic fibers and is, in
essence, an extension of the sympathetic nervous system (involved in the “fight or flight” reaction).
• An outer cortex: - Secretes several classes of _________hormone - three concentric zones of cells that differ in the major steroid
hormones they secrete.
Zona Reticularissex steroids (androgens)
Zona FasciculataGlucocorticoids (Cortisol)Glucose homeostasis and many others
Zona GlomerulosaMineralocorticoids (Aldosterone) Na+, K+ and water homeostasis
Medulla: Catecholamines
CORTEX
Adrenal
Functions of the Adrenal Cortex
• Zona glomerulosa: Mineralcorticoids – __________________
• Stimulate kidneys to reabsorb Na+ and secrete K+.
– Deoxycorticosterone • Zona fasciculata: Glucocorticoids
– __________________• Inhibit glucose utilization and stimulate
gluconeogenesis.
• Zona reticularis (DHEA): _______ steroids:• Androgens – significant amounts• Estrogens – insignificant amounts
Functions of the Adrenal Cortex (continued)
Functions of the Adrenal Cortex (continued)
• Carried by plasma specific – binding globulins
• Mechanism of action – Enters cell, ___________receptor, enters
nucleus, increases mRNA, increases __________ formation
Adrenal Glands• Adrenal medulla:
– Derived from _______________ neural crest ectoderm (same tissue that produces the sympathetic ganglia).
• Synthesizes and secretes:– ____________________ (mainly Epi but some NE).
Functions of the Adrenal Medulla
• Actions– _____________ respiratory rate. – Increase HR and cardiac output.– __________________ blood vessels, thus
increasing venous return.– Stimulate glycogenolysis.– Stimulate ____________________– Increases BMR– Stimulates spleen contraction – increased
RBC’s in blood
Functions of the Adrenal Medulla
• Stimuli– Hypoglycemia– Emergency situation
Stress and the Adrenal Gland• Non-specific response to
stress produces the general adaptation syndrome (GAS).
• Alarm phase:– Adrenal glands
activated.• Stage of resistance:
– Stage of readjustment.• Stage of exhaustion:
– Sickness and/or death if readjustment is not complete.
Thyroid Hormones• Thyroid gland is located
just below the larynx.• Thyroid is the
_____________ of the pure endocrine glands.
• Follicular cells secrete ___________.
• Parafollicular cells secrete ___________.
Thyroid Hormones
• Different activity in different animals– Fish – no specific organs, follicles scattered– Birds – 2 lobes – widely separated, no
isthmus– Snakes – 1 gland, anterior to heart
Production of Thyroid Hormones
• ___________ (I-) actively transported into the follicle and secreted into the colloid.
• Oxidized to iodine (Io).• Iodine attached to tyrosine within
thyroglobulin chain.– Attachment of 1 iodine produces
monoiodotyrosine (MIT).– Attachment of 2 iodines produces
diiodotyrosine (DIT).
Production of Thyroid Hormones (continued)
• _______ and ________ produced.• TSH stimulates pinocytosis into the
follicular cell.– Enzymes hydrolyze T3 and T4 from
thyroglobulin.• Attached to TBG and released into blood.
Production of Thyroid Hormones (continued)
Actions of T3
• Stimulates ________synthesis.• Promotes maturation of nervous system.• Stimulates rate of cellular respiration by:
– Production of uncoupling proteins.– ____________ active transport by Na+/K+ pumps.– Lower cellular [ATP].
• Increases ____________ heat.• Increases ______________ rate.
– Stimulates increased consumption of glucose, fatty acids and other molecules.
Mechanism of Thyroid Hormone Action
• Thyroxine (tetraiodothyronine) T4• Travels attached to _______________ (thyroxine-binding
globulin)• Small amount of T3 • Carrier proteins have a ___affinity for T4• Free T3 is what is physiologically active
– So, why do we have T4???– T4 passes into cytoplasm and is converted to T3.– Receptor proteins located in nucleus.
Diseases of the Thyroid
• Iodine-deficiency (endemic) goiter:– Abnormal growth
of the thyroid gland.
• In the absence of sufficient iodine, cannot produce adequate amounts of T4 and T3.
Diseases of the Thyroid (continued)
– Adult myxedema:– Symptoms:
• Decreased metabolic rate.• Weight gain.• Decreased ability to adapt to cold.• Lethargy.
• Grave’s disease:– Autoimmune disorder:
• Cretinism:– Hypothyroid from end of 1st trimester to 6 months postnatally.
• Severe mental retardation.
Parathyroid Glands• Embedded in the lateral
lobes of the thyroid gland.• Parathyroid hormone (PTH):
– Only hormone secreted by the parathyroid glands.
• Single most important hormone in the control of blood [___________].
• Stimulated by ___________blood [Ca2+].
• Promotes ________ in blood [Ca2+] by acting on bones, kidney and intestines.
Actions of Calcitonin
• Secreted by __________ cells• Works with parathyroid cells to regulate
Ca levels• Stimulates secretion of ________ in urine• Actions work to lower blood Ca levels
Pancreatic Islets (Islets of Langerhans)
• Alpha cells secrete ________.– Stimulus is decrease in blood
[glucose].– Stimulates glycogenolysis and
lipolysis.– Stimulates conversion of fatty
acids to ketones.• Beta cells secrete ________.
– Stimulus is increase in blood [glucose].
– Promotes entry of glucose into cells.
– Converts glucose to glycogen and fat.
– Aids entry of amino acids into cells.
Pineal Gland
• Secretes __________________:– Production stimulated by the suprachiasmatic nucleus
(SCN) in hypothalamus.• SCN is primary center for circadian rhythms.• Light/dark changes required to synchronize.• Melatonin secretion increases with darkness and peaks in middle
of night.
– May inhibit _________________.– May function in the __________ of puberty
(controversial).– Controls estrus in sheep, goats, and horses
Pineal Gland (continued)
Thymus
• Site of production of ____ cells (thymus-dependent cells), which are lymphocytes.– Lymphocytes are involved in cell-mediated immunity.
• Secretes hormones that are believed to stimulate T cells after leave thymus.– Thymus gland size is large in newborns and children.
• _____________ after puberty and becomes infiltrated with strands of fibrous tissue.
Gonads and Placenta
• Gonads (testes and ovaries):– Secrete sex hormones.
• Testosterone.• Estradiol 17-.• Progesterone.
• Placenta:– Secretes large amounts of _____________,
progesterone
Autocrine and Paracrine Regulation
• Autocrine:– Produced and act within the same tissue of an organ.
• All autocrine regulators control gene expression in target cells.• Paracrine:
– Produced within one tissue and regulate a different tissue of the same organ.
• Cytokines (lymphokines):– Regulate different cells (interleukins) .
• Growth factors:– Promote growth and cell division in any organ.
• Neutrophins:– Guide regenerating peripheral neurons.
Prostaglandins• Most diverse group of ________ regulators.• Produced in almost every organ.• Wide variety of functions.• Different prostaglandins may exert antagonistic effects in
some tissues.– Immune system:
• ___________________________________.– Reproductive system:
• ________________________________.– Digestive system:
• ______________________________
Lipid Hormones - ProstaglandinsFatty AcidsProstaglandins
1. Produced by all tissues of body2. Can have a local effect on tissues (same tissue which produced it)3. Rapidly degraded in lungs
Phospholipids- Rate limiting (Phospholipase A2)
- Precursor to ProstaglandinsAspirin inhibits
PGE2PGF2
Arachidonic Acid
Cyclo-oxygenase
Causes vasodilatation of blood vessels
Causes vasoconstriction ofBlood vessels
Prostaglandins (continued)
Prostaglandins (continued)
– Respiratory system:• May _____________________________.
– Circulatory system:• _____________________________.
– Urinary system:• Vasodilation.• See pg 318
• Inhibitors of prostaglandin synthesis:– Non-steroidal anti-inflammatory drugs (NSAIDS).
• Aspirin, indomethacin, ibuprofen: inhibit COX1.– Celecoxib and rofecoxib: inhibit COX2.