chapter 11 part 1 endocrine glands: secretion and action of hormones

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Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

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Page 1: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Chapter 11 Part 1

Endocrine Glands:

Secretion and Action of Hormones

Page 2: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Classic Definition of a Hormone

• Hormone - Chemical messenger produced by a ductless gland or tissue and carried in the blood/lymph to a target organ where it effects a change in cellular activity.

EffectorCell 1

TargetCell 2

Capillary

Page 3: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Endocrine Glands

Located at base of brain

Testis in Male

Adrenal Gland Ovary

KidneyPituitary

Hypothalamus

ThyroidParathyroid

Page 4: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Higher Centers of Brain Control All Hormonal Functions

Cerebrum

Cerebellum

MedullaOblongata

ThirdVentricle

PinealBody

Anterior & PosteriorPituitary

Hypothalamus

Pituitary Stalk

Page 5: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Anatomy of Cow Brain

Spenoid Bone

Pituitary

Diaphragma sellae

Infundibular Stalk

Page 6: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Control of Endocrine Gland FunctionHypothalamic-Pituitary Interrelationships

Pituitary Stalk

Nerve cells which releasepeptide hormones:Oxytocin, ADH

NeurohypophysisNerve endings comedirectly from hypothalamus

Adenohypophysisnon-neural tissue

HypothalamusSecreting neurons: GnRH,

CRH, TRH, GHRH

Hypophyseal Portal Vessels

Posterior Pituitary:

Release of Oxytocin or ADHinto circulation

Release of LH, FSH, ACTH, PRL, GH, TSH

Anterior Pituitary

Superior HypophysealArtery

Page 7: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Endocrine Glands and Hormones

• Secrete biologically active molecules into the blood.– Lack ducts.

• Carry hormones to target cells that contain specific receptor proteins for that hormone.

• Target cells can respond in a specific fashion.

• Different from nervous system – – Nervous system is fast, short-term reactions– Endocrine – longer duration, adaptation response.

Page 8: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Endocrine Glands and Hormones (continued)

• Neurohormone:– Specialized neurons that secrete chemicals into

the blood rather than synaptic cleft.• Chemical secreted is called neurohormone.

• Hormones:– Affect metabolism of target organs.

• Help regulate total body metabolism, growth, and reproduction.

Page 9: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

1) Paracrine - released from effector cell (E) interact with a different target cell (T1).2) Autocrine - secreted by E interact with original E cell or similar cell types. 3) Juxtacrine -expressed on surface of E and interacts with target cell (T2) via direct cell-cell contact. 4) Intracrine - is not secreted by E and interacts with an intercellular receptor.

Other forms of endocrine action

E T

E

E T

Page 10: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

• Pheromones: A chemical substance that is liberated by one animal and causes a relatively specific behavior modification in a recipient animal following its chemoreception• Lee-Boot effect: Crowded female mice become anestrous when no males are present.• Bruce effect: A newly mated female mouse will abort if placed with a strange male (not the previous mate).• Dormitory effect: menstrual synchrony in all-females living groups

EctocrineFlehmen

Page 11: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Common Aspects of Neural and Endocrine Regulation

• APs are chemical events produced by diffusion of ions through neuron plasma membrane.

• Action of some hormones are accompanied by ion diffusion and electrical changes in the target cell.– Nerve axon boutons release NTs.– Some chemicals are secreted as hormones, and also are

NTs.• In order for either a NT or hormone to function in

physiological regulation:– Target cell must have specific receptor proteins.– Combination of the regulatory molecule with its receptor

proteins must cause a specific sequence of changes.– There must be a mechanism to quickly turn off the action of

a regulator.

Page 12: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones
Page 13: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones
Page 14: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones
Page 15: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones
Page 16: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Most hormones belong to one of 4 structural classes

• Peptides & Amines (E, NE % DA) are hyrophilic

• Steroids and eicosanoids are hydrophobic

Page 17: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Structural Classes• Amines:

– Hormones derived from tyrosine and tryptophan.• NE, Epi, T4.

• Peptides, Polypeptides and Proteins– Polypeptides

• Chains of < 100 amino acids in length.– ADH.

• Ex: Adrenalcorticotropic Hormone (ACTH) – 39 amino acids

– Peptide - Few - Several amino acids• Ex: Gonadotropin Releasing Hormone (GnRH) - 10 amino acids• Oxytocin - 8 amino acids

– Protein hormones:• Polypeptide chains with > 100 amino acids.

– Growth hormone, Insulin, ACTH.– Prolactin - 198 amino acids

Page 18: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Structural Classes

• Glycoprotein - Protein hormone with carbohydrate molecules- Some have large amount of sialic acid – FSH

- Steroids- Lipids derived from cholesterol– Are lipophilic (fat loving; can diffuse through

plasma membrane) hormones.- Ex – testosterone, estradiol, progesteone, and

cortisol

Page 19: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Effects of [Hormone] on Tissue Response

• [Hormone] in blood reflects the rate of secretion.• Half-life:

– Time required for the blood [hormone] to be reduced to ½ reference level.

• Minutes to days.

• Normal tissue responses are produced only when [hormone] are present within physiological range.

• Varying [hormone] within normal, physiological range can affect the responsiveness of target cells.

Page 20: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Percent of Carbohydrate and Size of Protein Effects Half-Life in Blood

% inBloodAfterInjection

Human ChorionicGonadotropin -30% Carbohydrate

eCG

Equine ChorionicGonadotropin -45% Carbohydrate

Follicle Stimulating Hormone 8% Carbohrydrate

Luteinizing Hormone little sialic acid

GnRHOxytocin

Time required to remove or clear half of the dose from the blood

Page 21: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Chemical Classification of Hormones (continued)

Page 22: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Δ5Δ4

Δ5: Primates, Sheep, CattleΔ4: Pigs, rats, mice(Conley and Bird 1997)

Page 23: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Hormone Synthesis

• Protein Hormones – Synthesized at ribosomes as large precursor proteins – Preprohomrone converted to prohormone within

rough ER– Golgi apparatus – packages prohormone and

converts it to hormone– Stored in secretory granules– Upon stimulation – get exocytosis

• Requires: – 1. ATP

– 2. Ca

Page 24: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

The flow of

genetic information in a typical

cell

Page 25: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Anterior Pituitary Hormones Such as LH, FSH andTSH (Thyroid Stimulating Hormone) have Two Chains Alpha - Beta -

chain is identical between FSH, LH and TSH. chain gives the hormone its specific action.Need both chains together for biological activity

S S

Page 26: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

LHmRNA

Transcription

Translation

FSH

TSH

hCG

TSH, LH and FSH: Pituitary Glycoprotiens

hCG: placental

Page 27: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Synthesis of Steroid Hormones

• Ex: glucocorticoids, mineralocorticoids, sex steroids• Formed from cholesterol – which is used

immediately or stored in cell– Type of steroid hormone produced depends on presence

of specific enzymes– EX: adrenal cortex cell – contain enzymes needed for

production of glucocorticoids or mineralocorticoids

• Steroid hormones secreted immediately from cell after formation– Rate of steroid hormone secretion controlled by rate of

production

Page 28: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Mineralocorticoids, glucocorticoids and steroids are synthesized from

cholesterol

Cholesterol C27

Pregnenolone C21

Glucocorticoids C21

Mineralocorticoids C21

Androgens C19

Estrogens C18

Page 29: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Chemical Classification of Hormones (continued)

• Hormones can also be divided into:– Polar:

• H20 soluble.

– Nonpolar (lipophilic):• H20 insoluble.

– Can gain entry into target cells.

– Steroid hormones and T4.

– Pineal gland secretes melatonin:• Has properties of both H20 soluble and lipophilic

hormones.

Page 30: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Prohormones and Prehormones

• Prohormone:– Precursor is a longer chained polypeptide that is

cut and spliced together to make the hormone.• Proinsulin.

• Preprohormone:– Prohormone derived from larger precursor

molecule.• Preproinsulin.

• Prehormone:– Molecules secreted by endocrine glands that are

inactive until changed into hormones by target cells.

• T4 converted to T3.

Page 31: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Prohormones and Prehormones

Page 32: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

• Synergistic:– Two hormones work together to produce a

result.– Additive:

• Each hormone separately produces response, together at same concentrations stimulate even greater effect.

– NE and Epi.

– Complementary:• Each hormone stimulates different step in the

process.– FSH and testosterone.

Hormonal Interactions

Page 33: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Hormonal Interactions (continued)

– Permissive effects:• Hormone enhances the responsiveness of a

target organ to second hormone.– Increases the activity of a second hormone.

» Prior exposure of uterus to estrogen induces formation of receptors for progesterone.

– Antagonistic effects:• Action of one hormone antagonizes the

effects of another.– Insulin and glucagon.

Page 34: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Effects of [Hormone] on Tissue Response (continued)

• Priming effect (upregulation):– Increase number of receptors formed on target

cells in response to particular hormone.– Greater response by the target cell.

• Desensitization (downregulation):– Prolonged exposure to high [polypeptide

hormone].• Subsequent exposure to the same [hormone]

produces less response.– Decrease in number of receptors on target cells.

» Insulin in adipose cells.» Type 2 diabetes

– Pulsatile secretion may prevent down regulation.

Page 35: Chapter 11 Part 1 Endocrine Glands: Secretion and Action of Hormones

Mechanisms of Hormone Action• Hormones of same chemical class have

similar mechanisms of action.– Similarities include:

• Location of cellular receptor proteins depends on the chemical nature of the hormone.

• Events that occur in the target cells.• GH and Prolactin (Trophic hormones - increase in

growth)

• To respond to a hormone:– Target cell must have specific receptors for that

hormone (specificity).• Hormones exhibit:

– Affinity (bind to receptors with high bond strength).– Saturation (low capacity of receptors).