1. NERVOUS SYSTEM Objectives: 1. Describe the divisions of the nervous system & basic functioning 2. Explain how information flows through the nervous system 3. Describe the structure of neurons & glial cells & describe the functions of their parts.

2. Nervous System is Divided into 2 sections: Central Nervous System (CNS) Brain Spinal cord Peripheral Nervous System (PNS) Somatic – external environment Autonomic – internal environment

4. Functions: Together with endocrine syst., maintains homeostasis 3 part process:

5. RESPONSE DEPENDS ON NEURAL SIGNALING

6. Neurons Sensory receptors = specialized cells Sensory neurons Afferent – carry signal to CNS Most neurons are interneurons Integrate input/output aka association neurons CNS Motor neurons Efferent – carry away from CNS to effectors Effectors are muscles or glands

7. Neuron Structure

8. Neuron Structure, cont. Cell Body – contains most organelles Dendrites short, highly-branched Numerous Receives stimuli Axon May by up to 1 m long May form smaller branches Terminal branches/synaptic terminals Transmit signal from cell body to synaptic terminal

9. Glial Cells Support/protect neurons Regulatory functions Ex. Schwann cells form myelin around axons Fatty material found in plasma membranes of Schwann cells Insulate

10. Trends in Evolution: Increase in # of nerve cells Concentration of nerve cells Ganglia Brain Specialization of function Afferent vs. efferent Increased # of interneurons & more complex synaptic contacts What will this allow for?

11. Trends in Evolution, cont. Cephalization in organisms w/ bilateral symmetry Formation of head Sense organs concentrated at front end of body Advantage??

12. EXIT TICKET: How does the nervous system contribute to maintaining homeostasis?