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.