Essentials of Human Anatomy & Physiology

1. Essentials of Human Anatomy & Physiology The Nervous System Chapter 7

2. Nervous System Functions 1. Sensory input – gathered information • Allows you to monitor changes occurring in & outside of the body (changes = stimuli) 2. Integration • Process and interpret the sensory input and decide if action is needed 3. Motor output • A response to integrated stimuli activates muscles or glands

3. Structural Classification of the Nervous System • Central Nervous System (CNS) • Brain • Spinal cord • Peripheral Nervous System (PNS) • Nerves that extend from the brain and spinal cord

4. Functional Classification of the Peripheral Nervous System • Sensory (afferent) division • Nerve fibers that carry information to the central nervous system

5. Functional Classification of the Peripheral Nervous System • Motor (efferent) division • Nerve fibers that carry impulses away from the central nervous system

6. Functional Classification of the Peripheral Nervous System • Motor (efferent) division • Two subdivisions • Somatic nervous system = Voluntary • Autonomic nervous system = Involuntary • Sympathetic • Parasympathetic

7. Organization of the Nervous System

8. Nervous Tissue: Support Cells • Supporting Cells in the CNS • Lumped together as neuroglia (AKA- glia or glial cells) • “Nerve glue” • Includes many types of cells that support, insulate, & protect the delicate neurons • Each type has specific functions

9. Nervous Tissue: Neurons • Neurons = Nerve cells • Cells specialized to transmit messages • Nerve impulses • Major regions of Neurons • Cell body – Contains the nucleus and is the metabolic center of the cell • Processes – Fibers that extend from the cell body (dendrites and axons)

10. Neuron Anatomy • Cell body • Nucleus • Metabolic Center

11. Neuron Anatomy • Extensions outside the cell body • Dendrites – Conduct impulses toward the cell body • Axons – Conduct impulses Away from the cell body

12. Axons and Nerve Impulses • Axons end in axonal terminals • Axon terminals contain vesicles that contain neurotransmitters • Axon terminals are separated from the next neuron by a gap • Synaptic cleft – just the space between adjacent neurons • Synapse – junction between neurons; including the membranes of both neurons & the space between them

15. Nerve Fiber Coverings • Myelin • Covers nerve fibers • Whitish, fatty material • Waxy appearance • Protects & insulates the fibers • Increases the transmission rate of nerve impulses • Schwann cells – produce myelin sheaths in jelly-roll like fashion • Nodes of Ranvier – gaps in the myelin sheath along the axon

16. Application of Neurons • Multiple sclerosis (MS) • Chronic, potentially debilitating disease that affects the central nervous system, which is made up of the brain and spinal cord. • Myelin sheath is destroyed- It hardens to a tissue called the scleroses • Transmitted nerve impulses are short-circuited • Affected person loses control of his/her muscles and becomes increasingly more disabled • Autoimmune disease • Protein component of the sheath is attacked • No cure • Interferon injections • Hormone like substance released by some immune cells- provides relief • website

17. Multiple Sclerosis

18. Neuron Cell Body Location • Most neurons are found in the central nervous system • White matter- dense collections of myelinated fibers • Gray matter – unmyelinated fibers & cell bodies • Nuclei – clusters of cell bodies within the white matter of the central nervous system • Ganglia – collections of cell bodies outside the central nervous system (PNS)

19. Functional Classification of Neurons • Sensory (afferent) neurons • Carry impulses from the sensory receptors to the CNS • Cutaneous sense organs (Vision, hearing, equilibrium, taste & smell) • Proprioceptors – detect stretch or tension in skeletal muscles, tendons and joints • Pain receptors

20. Functional Classification of Neurons Motor (efferent) neurons • Carry impulses from the central nervous system to the viscera and/or muscles and glands Interneurons (association neurons) • Connect sensory and motor neurons in neural pathways

21. Neuron Classification