1. Nervous System SAP3. Students will assess the integration & coordination of body functions & their dependence on the endocrine and nervous systems to regulate physiological activities. Interpret interactions among hormones, senses, & nerves which make possible the coordination of functions of the body. Investigate the physiology of electrochemical impulses & neural integration; trace the pathway of an impulse, relating biochemical changes involved in the conduction of the impulse. Describe how the body perceives internal and external stimuli and responds to maintain a stable internal environment.

2. Nervous System Together, all nervous tissues in the body make up the nervous system. Among the 11 body systems, the nervous system and the endocrine system play the most important roles in maintaining homeostasis. The branch of medical science that deals with the normal functioning and disorders of the nervous system is called neurology.

3. What is the Nervous System? A system of nerves and supporting tissues that create Senses (sight, hearing, touch, etc) Thought Muscle Movement Feelings

4. Structures of the nervous system The structures include the brain, cranial nerves and their branches, the spinal cord, spinal nerves and their branches, ganglia, enteric plexuses, and sensory receptors. The Brain – contains about 100 billion neurons Cranial nerves – emerge from the base of the brain Nerve – bundle of hundreds to thousands of axons plus connective tissue and blood vessels that lie outside the brain and spinal cord Spinal cord – connects to the brain (encircled by vertebral column), contains about 100 million neurons

5. Structures of the nervous system Spinal nerves – emerge from the spinal cord, 31 pairs Enteric plexuses – networks of neurons found in the walls of organs of the gastrointestinal tract that help regulate the digestive system Sensory receptors – dendrites of sensory neurons (ex. Sensory receptors in the skin) or specialized cells that monitor changes in the environment (ex. Photoreceptors in the retina of the eye).

6. What is the job of the Nervous System? Sensory Function – detect stimuli. Within your body – ex. Blood pressure. Outside of your body – ex. A touch on your arm. Sensory (afferent) neurons carry this sensory information into the brain and spinal cord through cranial and spinal nerves. Integrative function – processes sensory info by analyzing and storing it and by making decisions for appropriate responses. Many of the neurons that participate in integration are interneurons. Interneurons (have axons that extend for a short distance and contact nearby neurons in the brain or spinal cord) make up the vast majority of neurons in the body.

7. What is the job of the Nervous System? Motor function - Once a sensory stimulus is perceived, an appropriate motor response (muscle contraction or gland secretion) should occur. This is done by motor (efferent) neurons. They carry info from the brain toward the spinal cord or out of the brain and spinal cord to effectors (muscles and glands) through cranial and spinal nerves. Stimulation of the effectors by motor neurons causes muscles to contract and glands to secrete.

8. Neurons Cell body (soma) – nucleus, cytoplasm, organelles (ER, lysosomes, mitochondria, golgi complex) Dendrites – (little trees) receiving part of a neuron Axon – conducts nerve impulses toward another neuron, muscle fiber or a gland Synapse – site where 2 neurons or a neuron and an effector cell can communicate.

9. Neurons Myelin sheath – made of lipids and proteins, many layers that covers the axon of a neuron. It is like insulation covering a wire. It increases the speed of a nerve impulse. There can be as many as 100 layers! Nodes of Ranvier – Gaps in the Myelin sheath Diseases such as Multiple Sclerosis and Tay-Sachs destroy myelin sheaths.

10. Gray and White Matter White matter – consists primarily of myelinated axons of many neurons. The whitish color of the myelin gives it the white color. Gray matter – contains cell bodies, dendrites, unmyelinated axons, and axon terminals. It looks gray because of the organelles and there is little or no myelin in those areas.

11. Regeneration Human neurons have VERY LITTLE ability to repair themselves! PNS – axons and dendrites may undergo repair if the cell body is intact and the Schwann cells are functional. Schwann cells on either side of an injured site multiply by mitosis and grow toward each other creating a regeneration tube across the injured area. Regrowth is slow! New axons cannot grow if the gap becomes filled with scar tissue. CNS – even if the cell body is intact a cut axon is usually not repaired.

12. Myelination Nerves that have a large diameter and are myelinated are super-fast: 120 m/s Nerves with a small diameter that are unmyelinated are slow:.5 m/s

13. How do nerves communicate? Through Neurotransmitters: chemical signals sent from the Axon terminals of the nerve Nerves communicate through electrical signals These electrical signals are created through action and resting potentials

14. How is an action potential reached? Change in nerve membrane permeability. Na+ rushes in and the nerve is depolarized (loses its charge). K+ then rushes out which repolarizes the nerve cell It takes 1/1000 (a millisecond). Both steps are the action potential Active transport soon reestablishes the resting potential

15. If a drug like procaine decreased the membrane permeability to Na+ ions, what would be the effect? Impulses from one nerve can not pass to the next region. The action potential can’t be reached. Used by doctors as a local anesthetic.

16. What kind of neurotransmitters cross the synaptic cleft? Acetylcholine: muscles Epinephrine/adrenaline: Fight or Flight Dopamine: brain functions: not working = schizophrenia (too much) and Parkinson’s Seratonin: suppresses pain impulses, temp regulation, mood, appetite, onset of sleep

17. What kind of neurotransmitters cross the synaptic cleft? Endorphins – body’s natural pain killers. Acupuncture may produce analgesia by increasing the release of endorphins. Endorphins are also linked to improved memory, learning, and feelings of pleasure.

18. neurotransmitters Therapeutic drug – Prozac – blocks the reuptake of specific neurotransmitters. This is known as Selective Serotonin Reuptake Inhibitor (SSRI). They block the reuptake of serotonin allowing Prozac to prolong the activity of this neurotransmitter at synapses in the brain. SSRI’s provide relief for those suffering from some forms of depression.