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Flashcards in Module 4 Deck (238)
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1

Reaction Time: Fast
Mediators: Neurons
Type of Message: Electrical impulse
Response Target: External environment
Linking Mechanism: Nerves and synapses
Effectors: Muscles and glands
Function: Nervous coordination

NERVOUS CONTROL

2

Reaction Time: Slow
Mediators: Hormones
Type of Message: Organic message
Response Target: Internal environment
Linking Mechanism: Blood and circulatory system
Effectors: Organ systems
Function: Chemical coordination

HORMONAL CONTROL

3

released by axon terminals and act locally to control cell functions

NEUROTRANSMITTERS

4

- local chemical messengers secreted by cells into the extracellular fluid & affect neighboring cells of a different type
- example: Histamine

PARACRINES/JUXTACRINE

5

- 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 surface receptors

AUTOCRINES

6

-are peptides secreted by cells into the ECF & can function as autocrines, paracrines or endocrine hormones
- Examples:
a. interleukins & lymphokines – secreted by helper cells & act on other cells of the immune system
b. Leptin (adipokines) – secreted by adipocytes

CYTOKINES

7

- secreted by neurons into the circulating blood and influence the function of cells at another location in the body
- examples ADH, OTC, and hypophysiotropic hormone

NEUROENDOCRINE HORMONES

8

- Greek word – HORMAEIN (to arouse or excite)
- released by endocrine glands into blood stream and influence function of target cells
- some affect almost all cells and organs (GH, Thyroid hormone, Catecholamines)
- other affect specific tissues (ACTH, TSH, FSH & LH)

Endocrine hormones

9

- secreted by ductless glands in the endocrine system
- play important role in homeostasis
- essential to the maintenance of the life and well being of an individual and of the species

Endocrine hormones

10

- Chemical Messengers
- secreted into the blood and acts on another location

Hormones

11

Main site of inactivation of hormone
(e.g. Estrogen in males)

LIVER

12

Mechanism for removal of hormone
(e.g. urine metabolites like VMA), LIVER (bile, feces)

KIDNEYS

13

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

14

Hormone Classes

1. PROTEIN HORMONE
2. BIOGENIC AMINES
3. STEROID HORMONE

15

- More common hormone class; Stored in vesicles

PROTEIN HORMONE

16

- derivatives of tyrosine
thyroid hormones (T3 and T4)
adrenal medullary hormones

- derivative of histidine:
histamine (mast cells in connective tissues)

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

BIOGENIC AMINES

17

- derivative of Cholesterol
- Synthesized as needed

STEROID HORMONE

18

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

STEROID HORMONES

19

Modifies existing proteins
Water-soluble
Reflection Coefficient closer to 1

PROTEIN HORMONES

20

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

G-PROTEIN LINKED HORMONE RECEPTORS

21

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

ENZYME-LINKED HORMONE RECEPTORS

22

- Heterotrimeric GTP-binding Proteins
- Act as TRANSDUCERS
- Link hormone receptors with 2nd messenger systems (Intracellular Enzymes and Ion Channels)
- May be Gs Protein (stimulatory) or Gi Proteins (inhibitory)
- 3 subunits: alpha, beta, gamma

G Proteins

23

- Most common 2nd Messenger System

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

cAMP/cGMP System

24

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

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

Phospholipid System (IP3/DAG)

25

- Used by Insulin, Growth factors, EPO, Leptin
- Enzyme-linked

Tyrosine Kinase

26

- Must be transported bound to a protein in the blood
- Active form: FREE, UNBOUND FORM

Lipid Soluble Hormones

27

Hormone Secretion, Transport and Clearance

- Onset of Hormone Effects (Varies from seconds (NE, Epi) to months (T3, GH))
- Very little amount needed to produce effect
- Number of Hormone Receptors (never constant)

28

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 and catecholamines

3. Activating the gene - Thyroid and steroid hormones

29

(Regulation of Hormone Secretion)

- “Products inhibit Precursors”
- More common
- E.g. Cortisol inhibiting ACTH Secretion from the Pituitary

NEGATIVE FEEDBACK

30

(Regulation of Hormone Secretion)

- “Products stimulate Precursors”
- Rare, exploding
- E.g. surge of LH before ovulation, Oxytocin during delivery and lactation

POSITIVE FEEDBACK