homeostasis endocrine system nervous system

2004-2005

Homeostasis

Endocrine System

Nervous System

2004-2005

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

2004-2005

Regulation & Communication

Animals rely on 2 systems for regulation

endocrine system (video) ductless gland which secrete

chemical signals directly into blood chemical travels to target tissue

slow, long-lasting response

nervous system system of neurons, central

nerve system transmits “electrical” signal to

target tissue

fast, short-lasting response

2004-2005

Regulation by chemical messengers

AxonNeurotransmitter

Endocrine gland

Receptor proteins

Hormonecarried by blood

Target cell

Neurotransmitters released by neurons

Hormones release by endocrine glands

Classes of Hormones

Protein-based hormones

polypeptides 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

How do hormones act on target cells

Lipid-based hormones

lipid-soluble

diffuse across membrane & enter cells

bind to receptor proteins in cytoplasm &

then this hormone-receptor complex moves

into nucleus

bind to receptor proteins in nucleus

Receptor protein + hormone bind to

DNA and stimulate transcription

Transcription: making an RNA copy of

DNA

2004-2005

Nucleus

Cytoplasm

Steroid hormone (S) passes through plasma membrane.

Inside target cell, the steroid hormone binds to a specific receptor protein in the cytoplasm or nucleus.

Hormone-receptor complex enters nucleus & binds to DNA, causing gene transcription

Protein is produced.

Protein synthesis is induced.

Plasma membrane

DNAmRNA

Protein

Steroidhormone

Blood plasma

Proteincarrier

1

2

2

3

3

5

5 4

4

S

S

S

1

S

Action of steroid (lipid) hormones

2004-2005

How do hormones act on target cellsSignal molecule

Cell surface receptor

enzyme

G protein

cAMP

Targetprotein

Nucleus

Cytoplasm

ATP

Protein-based hormones

hydrophilic & not lipid soluble can’t diffuse across

membrane

trigger secondary (2°) messenger pathway transmit “signal” across

membrane

usually activates a series of 2° messengers

activate cellular response enzyme action, uptake or

secretion of molecules, etc.

Action of protein hormones

3

4

GTPactivatesenzyme

activatesenzyme

activatesenzyme

Receptorprotein

cAMP

Proteinhormone

ATP

1

2

Cytoplasm

Produces an action

protein

messenger

cascade

G protein

2004-2005

Benefits of a 2° messenger system

Amplification!

Signal molecule Receptor protein Activated adenylyl cyclase

Amplification

Amplification

Amplification

Amplification

GTP G protein

2

1

3

4

5

6

7

Enzymatic product

Enzyme

Protein kinase

cAMP

Not yetactivated

2004-2005

Ductless

glands release

hormones into

blood

Endocrine system

Duct glands = exocrine

(tears, salivary)

Glands Pineal

melatonin

Pituitary

many hormones: master gland

Thyroid

thyroxine

Adrenal

adrenaline

Pancreas

insulin, glucagon

Ovary

estrogen

Testes

testosterone

2004-2005

Major vertebrate hormones (1)

Major vertebrate hormones (2)

2004-2005

Endocrine & Nervous system links

Hypothalamus = “master 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

2004-2005

Thyroid gland

Hypothalamus

Anteriorpituitary

Gonadotropic hormones:Follicle-stimulatinghormone (FSH) & luteinizing hormone (LH)

Mammaryglandsin mammals

Musclesof uterus

Kidneytubules

Posteriorpituitary

Thyroid-stimulating Hormone(TSH)

Antidiuretic hormone(ADH)

Adrenalcortex

Boneand muscle Testis

Ovary

Melanocytein amphibian

Maintaining homeostasis (video)

high

low

hormone 1

lowersbody condition

hormone 2

gland

specific body condition

raisesbody condition

gland

Feedback

Negative Feedback

Response to changed body condition

if body is high or low from normal level

signal tells body to make changes that will

bring body back to normal level

once body is back

to normal level,

signal is

turned off

high

hormone 1

lowersbody condition

gland

specific body condition

liver

pancreas

liver

Regulation of Blood Sugar

blood sugar level(90mg/100ml)

insulin

body cells takeup sugar

from blood

liver storessugar

reducesappetite

glucagon

pancreas

liver releases

sugartriggershunger

high

low

FeedbackEndocrine System Control

corpusluteumovary

Female reproductive cycle

pregnancy

maintainsuterus lining

no

yes

Feedback

estrogenegg

matures &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

Any Questions??

Nervous System

Nervous system cells

dendrites

cell body

axon

synapse

Neuron

a nerve cell

Structure fits function

many entry points for signal

one path out

transmits signalsignal direction

signal

direction

dendrite cell body axon

Neuron

Cells: surrounded by charged ions

Cells live in a sea of charged ions

anions (negative ions ) more concentrated within the cell

Cl-, charged amino acids

cations (positive ions) more concentrated in the extracellular fluid

Na+

Na+ Na+ Na+ Na+ Na+ Na+ Na+Na+ Na+ K+ Na+ Na+

Cl-

K+ Cl- Cl- Cl-

K+

aa-K+ Cl- Cl-

aa- aa-aa-

aa- aa-K+

K+channel

leaks K+ +

–

Resting Potential

Cells have voltage!

Opposite charges on opposite sides of

cell membrane

membrane is polarized

negative inside; positive outside

charge gradient

stored energy (like a battery)

+ + + + + + + ++ + + + + + +

+ + + + + + + ++ + + + + + +

– – – – – – – ––– – – – –

– – – – – – – ––– – – – –

How does a nerve impulse travel? Stimulus: nerve is stimulated

open Na+ channels in cell membrane membrane becomes very permeable to Na+

Na+ ions diffuse into cell

charges reverse at that point on neuron positive inside; negative outside

cell becomes depolarized

– + + + + + + ++ + + + + + +

– + + + + + + ++ + + + + + +

+ – – – – – – –– – – – – – –

+ – – – – – – –– – – – – – –

Na+

The 1stdomino is down

How does a nerve impulse travel?

Wave: nerve impulse travels down neuron change in charge opens other Na+ gates

in next section of cell

“voltage-gated” channels

Na+ ions continue to move into cell

“wave” moves down neuron = action potential

– – + + + + + +– + + + + + +

– – + + + + + +– + + + + + +

+ + – – – – – –+ – – – – – –

+ + – – – – – –+ – – – – – –

Na+

wave

The rest of the

dominoes fall

How does a nerve impulse travel?

Re-set: 2nd wave travels down neuron

K+ channels open up slowly

K+ ions diffuse out of cell

charges reverse back at that point negative inside; positive outside

+ – – + + + + +– – + + + + +

+ – – + + + + +– – + + + + +

– + + – – – – –+ + – – – – –

– + + – – – – –+ + – – – – –

Na+

K+

wave

Set dominoes back up quickly

How does a nerve impulse travel?

Combined waves travel down neuron

wave of opening ion channels moves

down neuron

signal moves in one direction

flow of K+ out of cell stops activation of Na+

channels in wrong direction

+ + – – + + + ++ – – + + + +

+ + – – + + + ++ – – + + + +

– – + + – – – –– + + – – – –

– – + + – – – –– + + – – – –

Na+

wave

K+Ready for next time!

How does a nerve impulse travel?

Action potential propagates

wave = nerve impulse, or action potential

brain finger tips in milliseconds!

+ + + + – – + ++ + + – – + +

+ + + + – – + ++ + + – – + +

– – – – + + – –– – – + + – –

– – – – + + – –– – – + + – –

Na+

K+

wave

In the blink of an

eye!

Voltage-gated channels Ion channels open & close in response to changes in

charge across membrane

Na+ channels open quickly in response to depolarization

& close slowly

K+ channels open slowly in response to depolarization &

close slowly

+ + + + + – + ++ + + + – – +

+ + + + + – + ++ + + + – – +

– – – – – + – –– – – – + + –

– – – – – + – –– – – – + + –

Na+

K+

wave

How does the nerve re-set itself? After firing a neuron has to re-set itself

Na+ needs to move back out

K+ needs to move back in

both are moving against concentration gradients

need a pump!!

+ + + + + – – ++ + + + + – –

+ + + + + – – ++ + + + + – –

– – – – – + + –– – – – – + +

– – – – – + + –– – – – – + +

Na+Na+Na+Na+

Na+ Na+Na+

K+K+K+K+ Na+ Na+

Na+Na+Na+

Na+Na+

Na+Na+

Na+

Na+

K+K+K+K+

K+K+

K+ K+

wave

A lot of work to do here!

How does the nerve re-set itself?

Na+ / K+ pump

active transport protein in membrane

requires ATP

3 Na+ pumped out

2 K+ pumped in

re-sets charge

across

membrane

That’s a lot of ATP!

Feed me some sugar quick!

Action Potential

Measuring cell voltage

unstimulated neuron = resting potential of -70mV

Action potential graph1. Resting potential

2. Stimulus reaches threshold potential

3. Na+ channels open; K+ channels closed

4. Na+ channels close; K+ channels open

5. Undershoot: K+ channels close slowly

Synaptic terminal

Chemicals stored in vesicles

release neurotransmitters diffusion of chemical across synapse conducts the

signal — chemical signal — across synapse

stimulus for receptors on dendrites of next neuron

synaptic terminal

neurotransmitter

chemicals

We switched…from an

electrical signalto a chemical

signal

Transmission Across a Synapse

Chemical synapse: follow the path• action depolarizes membrane

• triggers influx of Ca+

• vesicles fuse with membrane

• release neurotransmitter to cleft

• neurotransmitter bind with receptor

• neurotransmitter degraded / reabsorbedion-gated

channels

Nerve impulse in next neuron

Post-synaptic neuron

triggers nerve impulse in next nerve cell

chemical signal opens “ion-gated” channels

Na+ diffuses into cell

K+ diffuses out of cell

– + + + + + + ++ + + + + + +

– + + + + + + ++ + + + + + +

+ – – – – – – –– – – – – – –

+ – – – – – – –– – – – – – –

Na+

Here we go again!

Neurotransmitters Acetylcholine

transmit signal to skeletal muscle

Epinephrine (adrenaline) & norepinephrine

fight-or-flight response

Dopamine

widespread in brain

affects sleep, mood, attention & learning

lack of dopamine in brain associated with Parkinson’s disease

excessive dopamine linked to schizophrenia

Serotonin

widespread in brain

affects sleep, mood, attention & learning

snake toxin blocking

acetylcholinesterase active site

Acetylcholinesterase Enzyme which breaks

down neurotransmitter acetylcholine

inhibitors = neurotoxins

snake venom, sarin, insecticides

acetylcholinesterase

active site

in red

neurotoxin

in green