Assignment # Nervous Regulation and Reflex Arcs Biology Mrs. McCarthy Monday, August 27, 2018

I. Regulation – all the activities that help to maintain homeostasis Changes take place both inside and outside an organism To stay alive, an organism must respond to these changes Responses must be regulated and coordinated Irritability – ability to respond to the environment

II. Mechanisms of Nervous Regulation Impulses – messages carried by neurons Neuron – nerve cell

C. Receptors – sense organs sensitive to certain changes 1. Examples: a. physical forces – pressure, temperature b. chemicals inside and outside the body c. sight, hearing, touch, taste, smell

Effector –responds to the nervous system 1. Examples are glands and muscles

E. Stimulus – anything that causes a nerve impulse

How will your body respond to the hot stove? Example – you walk into your kitchen where your mother has just finished boiling some water. You did not know she was doing this, and so you touch the hot stove. Identify the following parts of the scenario: What is the stimulus? What is the receptor? What is the effector? How will your body respond to the hot stove?

III. Structure of a neuron Three basic parts 1. Cell body contains the nucleus and organelles 2. Dendrites – short, highly branched fibers that receive impulses 3. Axon – long, thin fiber that extends from the cell body. It carries the impulse to other neurons.

Neuron Diagram

Reflex – involuntary, automatic response to a stimulus IV. The reflex arc Reflex – involuntary, automatic response to a stimulus Reflex arc – pathway of impulses for a reflex

Receptor in the skin is stimulated by the heat Example – when your hand touches a hot object, it actually pulls away before you feel the sensation of heat or pain Receptor in the skin is stimulated by the heat The receptor starts an impulse in a sensory neuron, which carries it to the spinal cord In the spinal cord, the sensory neuron sends the impulse to an interneuron The interneuron sends the impulse to a motor neuron The motor neuron sends the impulse to the effector The effector is a muscle, which moves away the hand