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Nervous System

Learn about the sensory input, integration, and motor output functions of the nervous system, as well as the central and peripheral divisions. Explore the different types of supporting cells and neurons, and understand the parts and classification of a neuron. Discover the characteristics of the brain, including its lobes and senses.

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Nervous System

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  1. Nervous System

  2. Functions of the Nervous System • Sensory Input • Monitors changes (stimuli) inside and outside the body • Integration • Processes and interprets sensory input to decide what should be done • Motor Output • Supplies response by activating muscles or glands

  3. Nervous System Divisions • Central Nervous System (CNS) • Includes the Brain and Spinal Cord • Peripheral Nervous System (PNS) • Includes Spinal nerves & Cranial nerves

  4. Further Breakdown of PNS • Sensory (afferent) Division • Sends impulses to the CNS from sensory receptors in body • Somatic sensory fibers: messages from skin, muscles and joints • Visceral sensory fibers: messages from internal organs • Motor (efferent) Division • Carries impulses from CNS to effector organs (muscles and glands) to cause a response

  5. SAMESensory = Afferent(comes first, body  brain)Motor = Efferent(comes second, brain  body)

  6. Further Breakdown of Motor Division • Somatic System • Voluntary control of skeletal muscles • Autonomic System • Involuntary body responses, such as smooth & cardiac muscles, and glands

  7. Nervous Tissue • Made up of two types of cells • Supporting Cells: these structures do not directly transmit any signals, but they help the neurons to function properly; aka “glia” • Neurons: actually pass signals

  8. Supporting Cells • Neuroglia: supporting cells (glia) lumped together (term is commonly used to reference all types of supporting cells)

  9. Neuron Cell Body Neuroglia Cells

  10. Types of Supporting Cells in CNS • Astrocytes • Form barrier between capillaries and neurons • Help control chemical environment in brain • “To Make Mice Smarter, Add A Few Astrocytes!” • Scroll to bottom of website to see how astrocytes communicate • Microglia • Dispose of debris, such as dead brain cells and bacteria (immune system)

  11. Astrocytes can release gliotransmitters (like glutamate) by exocytosis to send signals to neighboring neurons. Each astrocyte has its own territory (they don't overlap), and each may interact with several neurons and hundreds to thousands of synapses to properly integrate information. "End-feet" connect to blood vessels in the brain. By signaling blood vessels to expand or narrow, astrocytes regulate local blood flow to provide oxygen and nutrients to neurons in need.

  12. Neurons Astrocytes

  13. Types of Supporting Cells in CNS • Ependymal • Lines cavity of brain & spinal cord • Circulate cerebrospinal fluid • Oligodendrocytes • Wrap around nerve fibers, forming myelin sheaths

  14. Types of Supporting Cells in PNS • Schwann cells: form myelin sheaths in PNS • Satellite Cells: protective, cushioning cells in PNS

  15. Neuron Cell Body Neuroglia Cells

  16. Parts Of A Neuron • Cell Body: metabolic center, contains rough ER (Nissl substance) and neurofibrils (maintain shape) • Dendrites: convey incoming messages toward cell body

  17. Parts Of A Neuron • Axons: conduct outgoing messages away from cell body (has only one originating at axon hillock) • Axon Terminal: branching at end of axon which contain neurotransmitters

  18. Parts Of A Neuron • Synaptic Cleft (Synapse): gaps between neurons • Myelin Sheath: protects and insulates nerve fibers (axon), increases rate of nerve impulses; made of proteins and lipids

  19. Parts Of A Neuron • Schwann cells: cells forming myelin sheath in PNS • CNS = oligodendrocytes • Nodes of Ranvier: gaps between Schwann cells on axon Did you know Einstein’s brain was STOLEN? Here the story here.

  20. FYI: Multiple Sclerosis • Myelin sheaths around the fibers are destroyed, and converted into hardened sheaths called scleroses • Person loses ability to control muscles

  21. Neuron Classification • Functional • Sensory (afferent): carry impulses from sensory receptors to CNS • Motor (efferent): carry impulses from CNS to body • Association (interneurons): connect motor and sensory neurons in neural pathways of CNS

  22. Neuron Classification • Structural • Multipolar: several extensions from cell body (common for motor neuron) • Bipolar: one axon and one dendrite from cell body (common for interneurons) • Unipolar: single process from cell body, process divides (common for sensory neuron)

  23. Central Nervous System

  24. http://www.youtube.com/watch?v=snO68aJTOpM

  25. Central Nervous System …also called the CEREBRUM

  26. Brain Characteristics • Gyri: elevated ridges of tissue (gyrus is singular) • Sulci: shallow grooves separating gyri (sulcus is singular) • Fissures: deep grooves separating large regions of brain • Lobes: separations of hemispheres of brain

  27. Senses & Controls of Brain - Cerebrum • White matter: collections of myelinated nerve fibers, usually found in deeper brain matter; carries the impulses (axons) • Gray matter: collections of UNmyelinated nerve fibers and cell bodies; usually found in the outer areas; contains the neuron cell bodies

  28. Cerebrum • The cerebrum is divided into right and left hemispheres by the longitudinal fissure • Controls consciousness • Senses and motor control occurs here! • Each hemisphere divided into 4 lobes

  29. Funny thing about the brain… • The somatic sensory area (cortex) • Where your senses are picked up & processed • Upside down • Signals from body parts toward the head are picked up at the base of the area, while signals from lower (inferior) body parts are picked up at the top of the area • Crossed pathways • Left side of the sensory area receives impulses from the right side of the body, and vice versa

  30. Funny thing about the brain… • The primary motor area (cortex) • Responsible for sending out signals for movement • Also upside down with crossed pathways

  31. Senses & Controls of Brain - Cerebrum • Occipital Lobe: contains visual sense • Temporal Lobe: contains smell & auditory senses • Also includes the hippocampus, which is responsible for long-term memory (including forming new memories about events) and spatial navigation

  32. Senses & Controls of Brain - Cerebrum Frontal Lobe… • Broca’s area: ability to speak (vocalize), usually more developed in left hemisphere • Language comprehension area: word meanings Language Comprehension Broca’s Area

  33. Senses & Controls of Brain - Cerebrum • Speech Area (aka Wernicke’s Area) • located at the junction of the temporal, parietal, and occipital lobes • Allows one to context spoken words (use them correctly) • Usually more developed in left hemisphere Speech Area

  34. Senses & Controls of Brain - Cerebrum • The Corpus Callosum is a very large nerve fiber tract (bundle) that connects the cerebral hemispheres & allows them to communicate

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