* the life function that deals with the control and coordination of all of the life activities (metabolism).
* there are two types of regulation; depends on special control mechanisms

NERVOUS CONTROL: found in multicellular animals only
CHEMICAL CONTROL: found in all organisms

I. How Regulation Happens
* depends mainly of the functioning of nerve cells called (neurons) in animals

Here's how it works...
What happens when the bell rings while you are in class?
Normally, you would get up and go to your next class! Except in biology, where I tell you when to leave!

1) stimulus--
* any change in the environment; can be internal (inside the body) or external (outside the body)

ex. light, sound, touch, chemicals

2) receptors--
* structures that are specialized to pick up (receive) stimuli from the environment
* different receptors pick up different stimuli

ex. eyes, ears, skin

3) impulse--
* an electro-chemcial (electricity and chemicals) charge that is generated by a neuron
* transmitted to and from the CENTRAL NERVOUS SYSTEM (in humans) when a receptor picks up a stimulus

4) response--
* a reaction that an organism makes to a stimulus

ex. can be a physical movement or a glandular response (pit in stomach)

5) effectors--
* specialized organs or other structures that produce (carry-out) a response

ex. muscles or glands

*bell rings ------------------- the sound is a stimulus

*ears pick up sound ----------- the ears are receptors

*message travels to and from the CNS -------- impulse

*student stands up ------------ response sent out by CNS

*muscles in leg/body move ----- muscles are the effectors carrying out response

(entire process carried out by NEURONS)


try to train Pavlov's dogs with this cool Flash game
hormones--the chemical messengers of the body; see how they were discovered

II. Nervous Control
A) The Neuron
* a nerve cell that is specially adapted for the transmission of impulses

* it has many parts:

1) dendrites--
* fibers which detect stimuli and generate impulses to the cyton

2) cyton--
* the main cell body that contains the nucleus

3) axon--
*a fiber which transmits the impulse away from the cyton towards the terminal branches

4) terminal branches--
* ends of the neuron which secrete neurotransmitters

5) synapse--
* the gap (also called space or junction) between two adjacent NEURONS

6) neurotransmitters--
* chemicals which when secreted by the terminal branches, help the transmission across a synapse; "continues" the electric impulse with chemicals!
* only travel from terminal branches of one NEURON to the dendrites of the next NEURON

ex. acetylcholine

Impulses only travel in one direction in most animals!

B) Adaptations for Nervous Control in Animals

1) Earthworm--
* has a primitive brain (CENTRAL NERVOUS SYSTEM) made up of fused ganglia (bunched nerves)
* also has a ventral (belly) nerve cord with smaller peripheral nerves branching out
* the presence of this central nervous system permits impulses to travel from receptors to brain to effectors (one-way)



be a mad scientist and build a neural connection
look at this informative link showing how impulses travel
watch this clip that shows neuron to neuron impulses
what are neuro-transmitters and how do they work
see how neuro- transmitters were discovered

III. Chemical Control
* used by all organisms
* similar to nerve control, however NEURONS are not used to control and coordinate all the body activities; chemicals called hormones are also used

* hormones are also called chemical messengers
* they are produced in glands which secrete them into the bloodstream; this transports the hormone to a TARGET TISSUE which will react a certain way
* hormones can either simulate (start) or inhibit (stop) a reaction
* hormones control--

1) overall metabolism
2) maintenance of homeostasis
3) growth and reproduction
4) reproductive cycles

A) Adaptations of Chemical Control

1) plants--
* plant hormones are chemicals produced by cells which affect growth and development of other cells
* plant hormones are produced in areas of the plant that grow quickly (root tips, stems, buds, seeds)
* a plant growth (mistakenly called movement) because of a stimulus is called a tropism
phototropism--response to light
geotropism--response to gravity
hydrotropism--response to water
thigmotropism--response to touch
*the plant hormones that are responsible for this kind of growth or "movement" are called AUXINS

2) animals (in general)--

* different than chemical control in plants because there are certain tissues that produce specific hormones
* these are found in ENDOCRINE GLANDS

*hormones are made in one place in the organism
*hormones carried by the circulatory system to their target tissues

* animal hormones control specific tissues and have many, many different functions


hormones--the chemical messengers of the body; see how they were discovered