PHYSIOLOGY: HUMAN BODY SYSTEMS

Homeostasis “Keeping things in balance” process by which organisms keep internal conditions relatively constant despite changes in external environments Maintained by the feedback loop

Feedback Loop Regulates many internal conditions Ex: feedback loop showing a response to cold * Positive (+): * Negative … variables triggers mechanisms that conteract Involves a change in some variables that triggers mechanisms that amplify

THE NERVOUS SYSTEM

Functions of the Nervous System Controls and coordinates the functions of the body Responds to internal and external stimuli Carries its messages through electrochemical signals called impulses

Neuron: Structure Are the cells that transmit impulses in the nervous system Diagram a neuron Label the dendrites and the axon terminal l Use arrows to show which way electrochemical impulses travel

3 Types of Neurons Sensory neurons: sense organ  spinal cord and brain Motor neurons: brain  spinal cord  muscles and glands Interneurons: connect sensory and motor neurons Differ by the direction in which they send signals sensory interneurons motor

The Nerve Impulse At rest, the cell is negative on the inside (more K + ), and positive on the outside (more Na + ) An impulse is a sudden reversal of the membrane potential

Synapse Transmition The location at which a neuron passes its impulse to neuron Axon Terminal connects to the dendrite There is a GAP The Axon terminal contains tiny sacs with NEUOTRASMITTERS these are chemicals that pass on impulse.