BIO 7:  Lecture 18 Preview

Nervous systems help animals respond quickly to stimuli

Neurons are key cells in the nervous system; they have dendrites, a nerve cell body, and an axon. 

A neuron can stimulate muscles to contract, glands to secrete, and/or another neuron to start an action potential.  Different neurotransmitters have different effects.


Bundles of neurons make up nerves; larger groups of neurons make up the brain and spinal cord.

The Peripheral Nervous System (PNS) = nerves coming from sense organs and going to muscles and glands.

The Central Nervous System (CNS) = brain and spinal cord, receiving information from sense organs, interpreting and storing information, and sending information to muscles and glands



Animals that do not move much have reduced CNS's.

Larger and more mobile animals have larger CNS's.


Parts of the brain are specialized to carry out different functions.



A reflex is a quick, unconscious response, to avoid danger e.g. eye blink when object nears eye quickly

Signal goes from sensory neuron to spinal cord to muscle neuron, before going to brain.



Many animals have highly developed sense organs for detecting changes in light, pressure, and chemicals in the environment.


Hormones from the Endocrine System help the Nervous System to Coordinate Activities among Cells in Big Organisms



In animals glands that produce hormones are called endocrine glands; they release hormones into the bloodstream.







Some hormones control blood glucose levels in humans:  insulin, glucagon, adrenaline.





Some hormones keep mineral levels constant in the body, using a negative feedback mechanism.