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Flashcards in ME04 - Introduction to Endocrine Deck (39):
1

Local chemical messengers secreted by cells into the ex
tracellular fluid & affect neighboring cells of a different
type

Paracrine/Juxtacrine (Histamine)

2

Affects cells of the same type
Secreted by cells into the ECF and affects the function of
the same cells that produced them by binding to cell sur
face receptors

Autocrines

3

Peptides secreted by cells into the ECF & can func
tion as autocrines, paracrines or endocrine hormones

Cytokines

4

Example of Cytokines

a. interleukins & lymphokines ? secreted by
helper cells & act on other cells of the immune system
b. Leptin (adipokines) ? secreted by adipocytes

5

Secreted by neurons into the circulating blood and influ
ence the function of cells at another location in the body

Neuroendocrine Hormones

6

Example of Neuroendocrine Hormones

ADH, OTC, & hypophysiotropic hormones

7

Released by endocrine glands into blood stream & influence function of target cells
Some affect almost all cells & organs (GH, Thyroid hormone, Catecholamines)
Other affect specific tissues (ACTH, TSH, FSH & LH)
Secreted by ductless glands in the endocrine system

Endocrine Hormones

8

Function of Endocrine Hormones

Play important role in homeostasis
Essential to the maintenance of the life & well being of an individual & of the species

9

Chemical Messengers
Secreted into the blood and acts on another location

Hormones

10

Main site of inactivation

Liver

11

Mechanism for removal of hormones

Kidneys, Liver

12

General Characteristics of Hormones

1. Secreted by specific group of cells
2. Thrown directly into circulation
3. Exert effects on target tissues which are distant from the source of hormone
4. Do not create an additional or new function, only modify or alter functions that already exists.
5. Rate of secretion fluctuates. Increases when there is a need for it; minimal when need not present.
6. Do not stay in the circulation forever
- Can undergo inactivation
- Main site of inactivation: LIVER
- Can be removed from circulation through kidneys.
- Plasma concentration of hormones tested by determining

13

Forms of Chemical Signaling

Autocrine ? cell targets itself

Signaling across gap junctions ? Cell targets a cell connected by gap junctions

Paracrine ? Cell targets nearby cell

Endocrine ? Cell targets a distant cell through the bloodstream

14

Hormones synthesized and secreteed by dedicated Endocrine Glands

Pituitary Gland ? GH, Prolactin, ACTH, TSH, FSH, LH

Thyroid Gland ? T4,T3, Calcitonin

Parathyroid Gland ? PTH

Islets of langerhans ? Insulin, Glucagon, Somatostatin

Adrenal Gland ? Epinephrine, NorEpi, Cortisol, Aldosterone, DHEAS

Ovaries ? Estradiol, Progesterone, inhibin

Testes ? Testosterone, AMH, Inhibin

15

Hormones Synthesized in Organs with Primary Function other than Endocrine

Brain (Hypothalamus) ? ADH, Vasopressin, Oxytocin, CRH, TRH, GnRH, GHRH, Somatostatin, Dopamine

Brain (Pineal Gland) ? Melatonin

Heart ? ANP

Kidney ? Erythropoietin

Adipose Tissue ? Leptin, Adiponectin

Stomach ? Gastrin, Somatostatin, Ghrelin

Intestines ? Secretin, Cholecystikinin, GLP-1, GLP-2, GIP, Motilin, IGF-1

Liver ? IGF-1

16

Classify Hormones

1. PROTEIN HORMONE
- More common, Stored in vesicles


2. BIOGENIC AMINES
- derivatives of tyrosine
- thyroid hormones (T3 & T4), adrenal medullary hormones

- derivative of histidine:
- histamine (mast cells inconnective tissues)

- derivatives of tryptophan
- melatonin (pineal gland)
- serotonin (blood platelets)



3. STEROID HORMONE
- derivative of Cholesterol
- Synthesized as needed

17

Produces new proteins from DNA
Lipid-soluble
Reflection Coefficient closer to 0

STEROID HORMONES
Slow-acting; To produce 2 proteins from DNA

18

Modifies existing proteins
Water-soluble
Reflection Coefficient closer to 1

Protein Hormones - facilitates signals; Faster

19

Types of Hormone Receptor

G-PROTEIN LINKED HORMONE RECEPTORS
Transmembrane proteins loop in and out of the cell membrane seven times
Make use of G-Proteins

ENZYME-LINKED HORMONE RECEPTORS
Passes through the membranes only once
Makes use of intracellular enzymes directly
E.g. Leptin and its use of Tyrosine Kinase

G Proteins
- Heterotrimeric GTP-binding Proteins
- Act as TRANSDUCERS
- Link hormone receptors with 2nd messenger systems (Intracellular Enzymes and Ion Channels)

20

Intracellular Enzymes and Ion Channels

May be Gs Protein (stimulatory) or Gi Proteins (inhibitory)
3 subunits: alpha, beta, gamma

21

The Second-Messenger System

? cAMP/cGMP
? IP3/DAG
? Calcium-Calmodulin
? Tyrosine Kinase

22

Most common 2nd Messenger System

cAMP/cGMP System

MECHANISM
Alpha subunit of G proteins activates Adenylate cyclase and together with ATP ?>forms cAMP ?> activates protein kinase A

23

Used by all Hypothalamic Hormones EXCEPT CRH
- Mediates smooth muscle contraction by hor-mone/neutrotransmitter (e.g. Motilin in the GI)

Phospholipid System (IP3/DAG)

- MECHANISM
Phospholipase C ?> PIP2 ?>PIP2 splits into IP3(releases Calcium) and DAG (activates protein kinase C)

24

Used by Insulin, Growth factors, EPO, Leptin

Tyrosine Kinase

25

Pathway >> G protein >> Protein Kinase

cAMP >> Gs INC cAMP; Gi DEC cAMP; Adenylate Cyclase >> Protein Kinase A

IP3/DAG >> Gq INC IP3/DAG; Phospholipase C >> Protein Kinase C
cGMP >>---------------------- >> Protein Kinase G
Tyrosine Kinase >> ---------- >> Tyrosine Kinase/ JAK-STAT
Intracellular (Steroid Hormones)

26

Must be transported bound to a protein in the blood

Lipid Soluble Hormones

27

Active form of Lipid Soluble Hormones

FREE, UNBOUND FORM

28

What is the Mechanism of Hormonal Action

On the target cell, the hormone in combination
with the receptor cells act by any of the following
mechanisms:
1. Alternating the permeability of cell membrane
- Neurotransmitter substances

2. Activating the intracellular enzyme
- Protein hormones & catecholamines

3. Activating the gene
- Thyroid & steroid hormones

29

Mechanism for Regulation of Hormone Effects

MECHANISMS
- Hormone Secretion
- Hormone Receptors

30

Differentiate Negative from Positive Feedback

NEGATIVE FEEDBACK
?Products inhibit Precursors?
More common
E.g. Cortisol inhibiting ACTH Secretion from the Pituitary


POSITIVE FEEDBACK
?Products stimulate Precursors?
Rare, exploding
E.g. surge of LH before ovulation, Oxytocin during deli-very and lactation

31

Differentiate Down-Regulation from UP-Regulation of Receptors

DOWN-REGULATION OF RECEPTORS
Decrease in:
- Receptor Number
- Receptor Affinity
- E.g. in the uterus, progesterone down-regulates its own receptor and the receptor for estrogen


UP-REGULATION OF RECEPTORS
Increase in:
- Receptor Number
- Receptor Affinity
- E.g. in the ovary, estrogen up-regulates its own re-ceptor and that of LH

32

3 types of Hormone Interactions

Synergistic Effects | Permissive Effects | Antagonistic Effects

33

Differentiate 2 Types of Synergistic Effec ts (Additive & Complementary)

- ADDITIVE EFFECTS
- E.g. Epinephrine & NE effects on the heart


- COMPLEMENTARY EFFECTS
- E.g. FSH & Testosterone effects on spermatogenesis

34

Differentiate Permissive Effects vs Antagonistic Effects

. PERMISSIVE EFFECTS
- E.g. Cortisol has permissive effects on Epi & NE with regards to blood vessels; T3 has permissive effects on Epi with regards to lipolysis


ANTAGONISTIC EFFECTS
- E.g. Estrogen blocking Prolactin effects on the breasts during pregnancy

35

Equal to the rate of disappearance of hormone from the plasma/concentration of hormone in each milliliter of plasma

Metabolic Clearance Rate

Mechanisms: Tissue Destruction, Tissue binding, Bile Excretion, Urine Excretion

36

Hormone >> Pituitary target

GnRH >> FSH, LH
CRH >> ACTH (B-LPH)
TRH >> TSH (PRL)
GHRH >> Somatotropin (GH)
PRH >> TRH
PIH >> Lactotrophs (PRL)
MRH >> MSH
MIH >> MSH

37

Where Oxytocin is produced

Paraventricular nuclei

38

Where ADH is produced

Supraoptic nuclei

39

Where hormones are stoed

Posterior Pituitary