3 Functions of the Nervous System Peripheral nervous system = (made up of nerves and supporting cells) collects information about the body’s external and internal environment.Also delivers instruction from brain to the appropriate part of the body.
4 Functions of the Nervous System Central nervous system (brain and spinal cord) processes information and creates a responseDraw CNS in the space below:
5 NeuronsMessages carried by the nervous system are electrical signals called impulses.Nervous system impulses are transmitted by cells called neurons.Recall on page 1 of your notes that Neurons are the cells that carry nerve impulses and glial cells surround and protect neurons
6 Types of NeuronsNeurons are classified according to the direction in which an impulse travels:Sensory neurons = carry impulses from sense organs (eyes and ears) to spinal cord and brain.Motor neurons = carry impulses from brain and the spinal cord to muscles and glands.Interneurons = process information from sensory neurons and then send commands to motor neurons.
7 Structure of NeuronsCell body = contains the nucleus and much of the cytoplasmDendrites = receive impulses from other neurons and carry impulses to the cell body.Axon = carries impulses away from the cell bodyNeurons may have dozens of dendrites, but usually they have only one axon.
8 Structure of NeuronsAxon terminals = series of small swellings at the end of the axonMyelin sheath = an insulating membrane that surrounds the axon and speeds up impulsesThe myelin sheath has many gaps, called nodes, where the axon membrane is exposed and where impulses travel slower.
10 The Nerve ImpulseAn impulse begins when a neuron is stimulated by another neuron or by the environment.A neuron remains in its resting state until it receives a stimulus to its dendrites large enough to start a nerve impulse from the cell bodyOnce it begins, the impulse travels quickly down the axon away from the cell body toward the axon terminals.
11 The SynapseAt the end of the neuron, the impulse reaches an axon terminal where a synapse is created to cross the synaptic cleftSynapse = the point at which a neuron transfers an impulse to another cellSynaptic cleft = the space that separates the axon terminal from the adjacent cell.
12 The SynapseThe axon terminal at a synapse contains tiny vesicles filled with neurotransmitters.Neurotransmitters = chemicals that transmit an impulse across a synapse to another cell.
13 Review: steps of synapse transmission Impulse arrives at the synapse from the axon terminalsNeurotransmitters are released from the axonNeurotransmitters diffuse across the synaptic cleft and bind to receptors on the dendrites of the receiving cellThis binding stimulates a new impulse begins in the second cell.
14 Draw the nerve synapse: neurotransmittersaxonterminalAxon of first cellimpulseNew impulse in dendrite of second cell