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

2. 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

3. Endocrine Glands Testis in Male Adrenal Gland Hypothalamus Ovary
Kidney
Pituitary
Located at
base of brain
Thyroid
Parathyroid
Testis in
Male

4. Anterior & Posterior Pituitary
Higher Centers of Brain Control All Hormonal Functions
Cerebrum
Hypothalamus
Third
Ventricle
Pineal
Body
Medulla
Oblongata
Pituitary Stalk
Anterior & Posterior
Pituitary
Cerebellum

5. Anatomy of Cow Brain Infundibular Stalk Diaphragma sellae Pituitary
Spenoid Bone

6. Control of Endocrine Gland Function
Hypothalamic-Pituitary Interrelationships
Hypothalamus
Secreting neurons: GnRH, CRH, TRH, GHRH
Nerve cells which release
peptide hormones:
Oxytocin, ADH
Superior Hypophyseal
Artery
Hypophyseal Portal Vessels
Pituitary Stalk
Posterior Pituitary:
Neurohypophysis
Nerve endings come
directly from hypothalamus
Anterior Pituitary
Adenohypophysis
non-neural tissue
Release of LH, FSH,
ACTH, PRL, GH, TSH
Release of Oxytocin or ADH
into circulation

7. 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.

8. 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.

9. Other forms of endocrine action
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. E E T

10. Ectocrine
Flehmen
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

11. 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.

16. Most hormones belong to one of 4 structural classes
Peptides & Amines (E, NE % DA) are hyrophilic
Steroids and eicosanoids are hydrophobic

17. Structural Classes Amines: Peptides, Polypeptides and Proteins
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 amino acids

18. 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

19. 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.

20. Percent of Carbohydrate and Size of Protein Effects Half-Life in Blood
Equine Chorionic
Gonadotropin -
45% Carbohydrate
eCG
% in
Blood
After
Injection
Human Chorionic
Gonadotropin -
30% Carbohydrate
Follicle Stimulating Hormone
8% Carbohrydrate
GnRH
Oxytocin
Luteinizing Hormone
little sialic acid
Time required to remove or clear half of the dose from the blood

21. Chemical Classification of Hormones (continued)

22. Δ4 Δ5 Δ5: Primates, Sheep, Cattle Δ4: Pigs, rats, mice
(Conley and Bird 1997)

23. 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

24. The flow of genetic information in a typical cell

25. b a Anterior Pituitary Hormones Such as LH, FSH and
TSH (Thyroid Stimulating Hormone) have Two Chains
Alpha - a
Beta - b b S S a
a chain is identical between FSH, LH and TSH.
b chain gives the hormone its specific action.
Need both chains together for biological activity

26.         TSH FSH LH hCG mRNA Transcription Translation
TSH, LH and FSH: Pituitary Glycoprotiens
hCG: placental

27. 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

28. Cholesterol C27 Pregnenolone C21 Androgens C19 Glucocorticoids C21
Mineralocorticoids, glucocorticoids and steroids are synthesized from cholesterol
Cholesterol C27
Pregnenolone C21
Glucocorticoids C21
Mineralocorticoids C21
Androgens C19
Estrogens C18

29. 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.

30. Prohormones and Prehormones
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.

31. Prohormones and Prehormones

32. Hormonal Interactions
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.

33. 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.

34. 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.

35. 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).