HORMONES AND CELL SIGNALLING

TYPES OF CELL JUNCTIONS

CHEMICAL SIGNALS AND MODES OF ACTION

Endocrine system – produces chemical messages = hormones that are transported from endocrine gland to target cell in the bloodHormones = chemical signals that travel throughout the bodyLocal regulators act on near by cellsPheromones communicate between different individuals­ These play a role in animal reproduction

CLASSES OF HORMONES

Protein-based hormones­polypeptides­ small proteins: insulin, ADH

­glycoproteins­ large proteins + carbohydrate: FSH, LH

­amines­ modified amino acids: epinephrine, melatonin

Lipid-based hormones­ steroids­ modified cholesterol: sex hormones, aldosterone

insulin

HOW DO HORMONES ACT ON TARGET CELLS

Lipid-based hormones­ hydrophobic & lipid-soluble­ diffuse across cell membrane & enter cells­ bind to receptor proteins in cytoplasm & nucleus­ bind to DNA as transcription factors­ turn on genes

Protein-based hormones­ hydrophilic & not lipid soluble­ can’t diffuse across cell membrane­ bind to receptor proteins in cell membrane­ trigger secondary messenger pathway­ activate internal cellular response­ enzyme action, uptake or secretion of molecules…

nucleus

target cell

DNAmRNA

protein

blood

proteincarrier

S

S

S

S

ACTION OF LIPID (STEROID) HORMONES

binds to receptor protein

cytoplasm

becomes transcription factor

ex: secreted protein = growth factor (hair, bone, muscle, gametes)

2

4

6

cross cell membrane1

steroid hormone

mRNA read by ribosome5

plasma membrane

protein secreted7

3

ACTION OF PROTEIN HORMONES

activatesenzyme

activatesenzyme

activates enzyme

ATP

produces an action

P1

2

3

cytoplasm

receptorprotein

response

signal

secondarymessengersystem

signal-transduction pathway

acts as 2� messenger

target cell

plasma membrane

binds to receptor protein

proteinhormone

ATPactivatescytoplasmicsignal

cAMP

GTP

activatesG-protein

transduction

POLAR AND NON-POLAR HORMONES

HORMONE RECEPTOR COMPLEX

adrenal glandEX: ACTION OF EPINEPHRINE (ADRENALINE)

activatesprotein kinase-A

activatesglycogen phosphorylase

activatesadenylyl cyclase

epinephrine

liver cell

releasedto blood

1

2 5

receptorproteinin cell membrane

cytoplasm

6glycogen

activatesphosphorylase kinase

GTP

cAMP4

activatesG protein

ATP

glucose

activates GTP

3

signal

transduction

response7

GDP

DIFFERENT EFFECTS OF A CHEMICAL SIGNAL

A single type of signal molecule can produce different responses in different target cells­May be due to different receptors ­May be due to differences within the signal transduction pathway of the target cell

BENEFITS OF A 2� MESSENGER SYSTEM

Amplification!

signal

receptor proteinActivated adenylyl cyclase

amplification

amplification

amplification

amplification

GTP G protein

product

enzyme

protein kinase

cAMP

Not yetactivated

1

2

4

35

6

7

FAST response!

amplification

Cascade multiplier!

MAINTAINING HOMEOSTASIS

high

low

hormone 1

lowersbody condition

hormone 2

gland

specific body condition

raisesbody condition gland

Negative FeedbackModel

CONTROLLING BODY TEMPERATURE

high

low

nerve signals

sweat

nerve signals

body temperature(37�C)

shiver

dilates surfaceblood vessels

constricts surfaceblood vessels

Nervous System Control Feedback

hypothalamus

hypothalamus

liver

pancreas

liver

REGULATION OF BLOOD SUGAR

blood sugar level(90mg/100ml)

insulin

body cells takeup sugar from blood

liver storesglycogen

reducesappetite

glucagon

pancreas

liver releasesglucose

triggershunger

high

low

FeedbackEndocrine System Controlislets of Langerhans beta islet cells

islets of Langerhansalpha islet cells

POSITIVE FEEDBACK AND HORMONES

Oxytocin induces contraction of the uterus during childbirth and causes mammary glands to eject milk during nursing.­Oxytocin signaling in both cases exhibits positive feedback.

NERVOUS & ENDOCRINE SYSTEMS LINKEDHypothalamus = “master nerve control center”­ nervous system­ receives information from nerves around body about internal conditions ­ releasing hormones: regulates release of hormones from pituitary

Pituitary gland = “master gland”­ endocrine system­ secretes broad rangeof “tropic” hormones regulating other glands in body

hypothalamus

pituitary

posterior

anterior

HOMOLOGY IN HORMONES

prolactin

mammals

milkproduction

birds

fatmetabolism

amphibians

metamorphosis& maturation

fish

salt &waterbalance

What does this tell you about these hormones?

SIGNAL TRANSDUCTION MODELINGCreate a model that demonstrate signal transduction.

The protein hormone glucagon that binds to a receptor in the plasma membrane with a cytoplasmic response through a G-protein & 2nd messenger & phosphorylation cascade (that leads to the breakdown glycogen to glucose).

Must Include: G-protein linked receptor, G protein, Adenylyl Cyclase, ATP & cAMP, multiple kinases, phosphates, glycogen phosphorylase, glycogen (& glucose)

Note: The final response is carried out by the phosphorylation the enzyme glycogen phosphorylase