Understanding the Nervous System: Structure, Functions, and Impacts

1. Chapter 31 NotesThe Nervous System

2. The Nervous System: • is a rapid communication system using electrical signals. • enables movement, perception, thought, emotion and learning. • consists of a network of specialized cells called neurons.

3. Neuron structure: • Cell Body: central part of neuron, maintains cell function, relays signals from one part of cell to another. • Dendrites: extend from cell body, receive information from other cells.

4. Axon: long extension from the cell body, transmits signals to other neurons, ends in an axon terminal. Many axons are insulated with myelin which improves the efficiency of signal transmission. • Synapse: where the axon terminal connects with another neuron, separated by a gap called the synaptic cleft.

5. Axon terminal axon Cell body dendrites

6. Nerve= A bundle of several neurons and supporting cells. • Neuron function: • Neurons transmit signals down axons by altering the flow of sodium and potassium ions across their membranes in response to chemical signals. The resulting imbalance of electrical charges inside vs. outside the axon creates an electrical voltage potential (an “action potential”) that is propagated down the length of the axon.

7. When an electrical impulse reaches the axon terminal, it stimulates the release of neurotransmitters from the “pre-synaptic” neuron into the synaptic cleft. These chemical messengers bind receptors on the surface of the “post-synaptic” neuron and either stimulate or inhibit an action potential in it.

8. Most psychoactive drugs function by mimicking or interfering with the function of neurotransmitters and/or their receptors.

9. Structure of the Nervous System • Divided into two parts: • Central Nervous System (CNS): • Interprets and responds to information • Consists of the Brain & Spinal Cord Optical Illusions Website

10. Peripheral Nervous System (PNS), which contains: • Sensory neurons that send info (sight, smell, touch, sound, taste, pain) to the CNS. • Motor neurons that send commands from CNS to muscles and other organs. Divided into: • Somatic nervous system: controls skeletal muscles that are under conscious control • Autonomic nervous system: controls smooth muscles that are not under conscious control (i.e. the heart, diaphragm, digestive system)

11. Parts of the Brain: • Cerebrum (green) • Largest part of the brain, divided into two hemispheres. • Handles learning, memory, perception and intellectual functions. • Left hemisphere processes sensations from and controls movement on the right side of the body, the right hemisphere does the same for the left side of the body.

12. Cerebellum (blue) • Regulates balance, posture and movement; • coordinates the moving of several muscles together (i.e. for walking)

13. Brain Stem: a collection of several structures at the base of the brain. (yellow) • Midbrain, pons and medulla oblongata: relays information and regulates homeostasis and vital body functions. • Thalamus: central relay center for all sensory information traveling from the body to the brain. • Hypothalamus: regulates homeostasis and the endocrine system.