Colonie High AP Biology DeMarco/Goldberg

Chapter 41Chemical Regulation

Regulation

Why are hormones needed?

chemical messages from one

body part to another

communication needed to

coordinate whole body

homeostasis & regulation

metabolism

growth

development

maturation

reproduction

growth hormones

Regulation & Communication

Animals rely on 2 systems for regulation…

endocrine system

system of ductless glands secrete chemical signals ‘directly’ into blood

chemical travels to target tissue

slow, long-lasting response

nervous system system of neurons transmits “electrical” signal &

release neurotransmitters to target tissue

fast, short-lasting response

Regulation by Chemicals

axon

endocrine gland

receptor proteins

target cell

Neurotransmitters released by neurons

Hormones release by endocrine glands

receptor proteins

hormone carried by

blood

neurotransmitter

Homology in Hormones

prolactin

mammals

milk

production

birds

fat

metabolism

amphibians

metamorphosis

& maturation

fish

salt &

water

balance

growth

& development

What does this tell you about these hormones?

growth

hormone

How could this hormone have different effects?

Types of Hormones

circulating hormones

hormones that diffuse

into the blood to

activate target cells far

away

local hormones

hormones that affect

target cells close to

their release site

autocrine: hormone-

releasing cell affected

paracrine: hormone

affects nearby cells only

Colonie High AP Biology DeMarco/Goldberg

Classes of Hormones

Lipid-based hormones

steroids

modified cholesterol: sex hormones, aldosterone

Protein-based hormones

polypeptides

small proteins: insulin, ADH

glycoproteins

large proteins + carbohydrate: FSH, LH

amines

modified amino acids: epinephrine, melatonin

insulin

How do hormones act on target cells?

Lipid-based hormones

hydrophobic & lipid-soluble

diffuse across membrane & enter cells

bind to receptor proteins in cytoplasm & nucleus

bind to DNA as transcription factors

Protein-based hormones

hydrophilic & not lipid soluble

can’t diffuse across membrane

receptor proteins in cell membrane

trigger secondary messenger pathway

activate internal cellular response enzyme action, uptake or secretion of molecules…

nucleus

target cell

plasma membrane

DNA

mRNA

blood

proteincarrier

S

S

S

S

Action of Lipid (Steroid) Hormones

receptor protein

cytoplasm

transcriptionfactor

ex: growth factors (hair, bone, muscle, gametes)

1

2

3

4

5

steroid hormone

protein

Signal Transduction Pathway

signal triggers receptor

receptor triggers internal cellular messengers & then cellular response

oreceptor

osignal

pathway(2° messengers)

oresponse

What kinds of

molecules are

the receptors?

Action of Protein Hormones

activatesenzyme

activatesenzyme

activates ion channel

or enzyme

protein hormone

ATP

produces an action

transduction

P

1

2

3

cytoplasm

receptorprotein

response

signal

secondarymessenger

system

signal

transduction

pathway

2° messenger

target cell

plasma membrane

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

7POWERFUL response from a small stimulus!

amplification

Colonie High AP Biology DeMarco/Goldberg

adrenal gland

Action of Epinephrine (adrenalin)

activatesprotein kinase-A

activatesglycogen phosphorylase

activatesadenylyl cyclase

epinephrine

liver cell

releasedto blood

1

2 4

receptorprotein

cytoplasm

5glycogen

activatesphosphorylase kinase

GTP

cAMP

3

activatesG protein

GDP

ATP

6glucose

Nervous & Endocrine Systems Linked

Hypothalamus = “master nerve control center”

nervous system

receives information from nerves around body

about internal conditions

regulates release of hormones from pituitary

Pituitary gland = “master gland”

endocrine system

secretes broad range

of hormones

regulating other

glands

hypothalamus

pituitary

posterior

anterior

Thyroid gland

hypothalamus

anteriorpituitary

gonadotropichormones:

follicle-stimulating

hormone (FSH) & luteinizing hormone (LH)

Mammaryglands

in mammals

Musclesof uterus

Kidneytubules

posteriorpituitary

thyroid-stimulating hormone

(TSH)antidiuretic

hormone(ADH)

Adrenalcortex

Boneand muscle Testis

Ovary

Melanocytein amphibian

tropic hormonesRegulating Metabolism

Hypothalamus TRH = TSH-releasing hormone

Anterior Pituitary

TSH = thyroid stimulating hormone

Thyroid

produces thyroxine hormones

metabolism & development bone growth

mental development

metabolic use of energy

blood pressure & heart rate

muscle tone

digestion

reproduction

tyrosine+

iodinethyroxine

Mammals regulate use & storage of glucose

insulin reduces blood glucose levels

glucose levels rise above set point,

pancreas secretes insulin

promotes transport of glucose into cells &

storage of glucose (as glycogen) in liver & muscle

cells

drops blood glucose levels

glucagon increases blood glucose levels

when glucose levels drop below set point,

pancreas secretes glucagon

promotes breakdown of glycogen &

release of glucose into the blood

raises blood glucose levels

Managing Glucose Levels

liver

pancreas

liver

Regulation of Blood Sugar

blood sugar level(90mg/100ml)

insulin

glucagon

pancreas

high

lowFeedback

Endocrine System Control

islets of Langerhansbeta islet cells

islets of Langerhansalpha islet cells

body cells takeup sugar

from blood

liver storesglycogen

reducesappetite

liver releasesglucose

triggershunger

Colonie High AP Biology DeMarco/Goldberg

Feedback

corpusluteumovary

Female Reproductive Cycle

pregnancy

maintainsuterus lining

yes

estrogen

eggmatures &is released(ovulation)

builds up uterus lining

FSH & LH

progesterone

progesterone

fertilized egg(zygote)

hCG

corpus luteum breaks downprogesterone drops

menstruation

corpusluteum

maintainsuterus lining

GnRH

pituitarygland

hypothalamus

Endocrine System Control

no

Regulation of Blood Volume / Pressure

Hormone regulation

ADH (antidiuretic hormone) from pituitary

causes kidneys to reabsorb more water

aldosterone from adrenal gland

causes kidneys to reabsorb Na+

atrial natriuretic hormone from heart (right atrium)

promotes excretion of Na+ in urine

nitric oxide from blood vessel cells

dilates blood vessels

nitroglycerin & Viagra release nitric oxide

BP

BP

BP

BP

Phototropism

Growth towards lightWent 1926

Phytochrome Photoreceptors Molecular switch reaction to red light

conversion of Pr Pfr in sunlight stimulates germination, flowering, branching…

conversion of Pfr Pr in dark inhibits response, & stimulates other responses: growth in height

Light induced

Phytochrome

Chromophore

Photoreceptor

Kinase activity

Response:

Vertical growth

Phytochrome

Flowering Response

Short-day plants Long-day plants

Triggered by photoperiod

relative lengths of day & night

night length—“critical period”— is trigger

Plant is

sensitive to

red light

exposure!

What is the

evolutionary

advantage of

photoperiodism?

Synchronizes

plant responses

to season!

Signal Transduction Pathway

1. Light signal is detected by

the phytochrome receptor,

which then activates at least 2

signal transduction pathways2. One pathway uses cGMP as a 2nd

messenger to activate a protein

kinase.

The other pathway involves

increases in cytoplasmic Ca2+ that

activates a different protein kinase.

3. Both pathways lead

to expression of genes

for proteins that

function in greening

response of plant.