Outline Cell Signaling

Outline Cell Signaling: Types of Cell Signaling 1. Direct a.

Connected by gap junctions

2. Indirect a.

Releases chemical messenger

Peptide/Protein Hormones

-

50 Amino Acids = 1 PEPTIDE

-

Synthesized by: Rough ER

-

Stored in: Vesicles (Prohormones)

-

Secreted by: Exocytosis

-

Hydrophilic

b. Carried in ECF c.

Activates signal transduction

Indirect Signaling Over Short Distance 1. Paracrine a. Nearby cell 2. Autocrine a.

Back to self (MAKASARILI)

Indirect Signaling Over Long Distance 1. Endocrine System a.

o

Soluble in aqueous solution

o

Travels to target cell by ECF

-

Binds to transmembrane receptors

-

**RAPID EFFECT

Synthesis *17/105* Steroids

-

From Cholesterol

-

Synthesized by: SMOOTH ER/ Mitochondria

-

3 Classes: o

Hormones transport by circ system

Mineralocorticoids 

2. Nervous System a.

o

Electrical signals along neurons and

Glucocorticoides 

chemical messengers o

(hormones/neurotransmitters) Direct Signaling

Regulate Sex-Specific Characteristics

1. Gap Junctions

-

Aqueous pore between cells

b. Mvmt ions c.

Stress hormones

Reproductive Hormones 

a.

Electrolyte balance

cAMP travels through here

Indirect Signaling

-

Hydrophobic: o

Can diffuse thru plasma membrane

o

Cant be stored in cell

o

Synthesized on demand

o

Transport by carrier proteins

SLOW EFFECT (gene transcription)

Three Steps

**25/105**

1. Release of chemical messenger

Amines

2. Transport of messenger through extracellular envi 3. Communication of signal to target cell

-

Possess Amine Group (-NH2)

-

Eg. Acetylcholine, catecholamines (dopamines etc)

-

Hydrophilic o

6 Classes of Chemical Messengers: -

Peptides

-

Steroids

-

Amines

-

Lipids

-

Purines

-

Gases

**Hydrophilic/Hydrophobic **Hydrophilic/Hydroph obic affects signaling

Except thyroid hormones (hydrophobic)

Other Chem Messengers: -

-

Eicosanoids o

Paracrines

o

Hydrophobic

o

In inflammation; leukotrienes

Gases o

Paracrine

o

Nitric oxide, Carbon Monoxide

-

Purines

Signal Transduction Pathway

o

Neuromodulator and paracrine

o

ATP, GMP etc

Communication to Target Cell

-

4 Components o

Receiver (ligand binding region)

o

Transducer (conformational change of

receptor)

Bind to transmembrane receptor

o

Hydrophobic messenger 

o

Receptor changes shape when ligand binds o

CONFORMATIONAL CHANGE

Types of Receptors: -

Intracellular o

Specific

-

Mimics

-

o

Agonists – activate receptors

o

Antagonists – block receptors

Receptor isoforms

Ligand Receptor Binding

-

-

May bind to more than 1 receptor o

-

Receptors may become saturated if high ligand

o

Regulates transcription of target genes

o

Affects prod of mRNA

Ligand – gated ion channels o

Change in membrane potential

o

Receptor changes shape

o

Binds to transmembrane receptor

o

Electrochemical gradient

Receptor – enzymes o

Change in intracellular enzyme activity

o

Binds to Transmembrane receptor

o

Starts a phosphorylation cascade

Changes in Number of Receptors -

(maraming phinophosphorylate) o

Target Cells can alter receptor number o

Down  – regulation 



o

Target cell decreases number of



Guanylate cyclase, tyrosine Kinase, serine threonine kinase

-

G-Protein Coupled

receptors

o

Activate membrane bound G-proteins

Due to high concentration ligand

o

Change in cell activities

o

Binds to transmembrane receptor

Target cell increases number of

o

Interacts with G-proteins

receptors

o

Activates amplifier enzymes

Up-regulation 

Bind to hydrophobic ligands (in cytoplasm/nucleus)

Ligand Receptor Interactions -

Responder (functions that change in

response to signal)

Chemi messenger can bind to specific receptor

Amplifier (increase number of molecules

by signal)

Binds to intracellular receptor

Ligand o

-

-

Hydrophilic Messenger 

o

Converts change in receptor shape to intracellular response

Receptor on Target Cell o

-

-



Adenosine vs caffeine

Inactivation of Ligand Receptor Complex thru:

Forms second messengers

Regulation of Cell Signaling -

Components of Biological Control Systems

-

By distant tissues

-

By adjacent cells

-

By extracellular enzymes

-

Endocytosis

-

Receptor inactivation



Evaluates input from sensor

-

Inactivation of signal transduction pathway



Sends signal to effector

o

Sensor 

o

o

Detects variable

Integrating center (controller)

Effector 

Target tissue responds to signal

Regulation of Cell Signaling -

-

Set Point o

Value maintained by body

o

Elem me ne yen

Feedback Loops o

Positive 

Output of effector amplifies from set point

o

Negative 

Output of effector brings variable back to set point

Feedback Regulation

-

Direct Feedback Loop

-

First-Order Feedback Loop

-

Second  – Order Feedback Loop

-

Third – order feedback loop

Pituitary Hormones

-

Pituitary gland secretes many hormones

-

2 distinct anatomic sections o

Anterior Pituitary

o

Posterior Pituitary

Posterior Pituitary

-

Extension of Hypothalamus o

Neurons from hypothalamus to posterior pituitary

o

Eg. Neurohormones like oxytocin and vasopressin

-

First  – order endocrine pathway o

Hypothalamus receives sensory input

o

Hypothalamus serves as integrating center

**Endocrine of physio ex is similar**

**49/105** **57/105** **60/105** **63/105** **67/105** **70/105****71/105**