Recommended
More Related Content
What's hot
What's hot (20)
Similar to U9.2 Nervous System
Similar to U9.2 Nervous System (20)
More from NeQuelle DeFord
More from NeQuelle DeFord (20)
Recently uploaded
Recently uploaded (20)
U9.2 Nervous System
- 1. D E F O R D THE NERVOUS SYSTEM
- 3. TWO CELL TYPES • Neuroglia – supporting cells that insulate, support, and protect delicate neurons • Neurons – nerve cells 3
- 4. 4 • Ependymal cells: ciliated cells that line cavities of the brain and spinal cord; beating cilia keep cerebrospinal fluid circulating • Astrocytes: anchor neurons to capillaries and regulate exchanges between them • Oligodendrocytes: wrap around nerve fibers to form insulating coverings called myelin sheaths • Microglia: phagocytes that dispose of debris, including dead brain cells and bacteria • Satellite cells: protective cushioning cells in the PNS • Schwann cells: form myelin sheaths in the PNS
- 5. ANATOMY OF A NEURON • Dendrites: fibers that receive & convey messages to cell body • Cell body: metabolic center of the cell; contains the nucleus • Axon: fibers that conduct impulses away from the cell body • Axon terminal: branching fibers at the end of the axon; contains vesicles filled with chemicals called neurotransmitters 5
- 6. NEURON DETAILS Axon Terminal Direction of Impulse 6
- 7. MYELIN SHEATH • Some neurons have a covering composed of a whitish, fatty material called myelin • Insulates fibers and increases the rate of transmission of the nerve impulse 7
- 8. • Nerve cells outside the CNS are myelinated by Schwann cells • Wrap themselves around the axon • Gaps between Schwann cells, Nodes of Ranvier, allows impulse to jump from node to node, increasing transmission speed SCHWANN CELLS Schwann cell 8
- 9. AXON TERMINAL • At their terminal end, axons branch into hundreds or thousands of axon terminals • Each contains vesicles or sacs of neurotransmitters • When a nerve impulse reaches an axon terminal, it stimulates the release of neurotransmitters 9
- 10. SYNAPSE • Neurons do not actually touch each other • The junction between them is called a synapse • Neurotransmitters diffuse across the synapse to continue cell to cell communication 10
- 11. BUNDLES OF NERVE FIBERS 11 • White matter – myelinated • Gray matter – unmyelinated • In PNS, they are called nerves • In CNS, bundles of nerve fibers are called tracts
- 12. STRUCTURAL CLASSIFICATION OF NEURONS Based on the number of processes extending from the cell body. 12 • Bipolar – have a single dendrite and axon • Unipolar – lack dendrites and have a single axon • Multipolar (most common) – one axon and several dendrites
- 13. FUNCTIONAL CLASSIFICATION OF NEURONS • Sensory (Afferent) Neurons (green) carry impulses from receptors (such as the skin) to the CNS • Interneurons (Relay Neurons) (yellow) connect sensory and motor neurons in the CNS • Motor (Efferent) Neurons (purple) carry impulses from the CNS to an effector (muscle or gland) 13
- 14. 14
- 15. 15 Unipolar Neuron (Sensory Neuron) Receptor CNS Bipolar Neuron (Interneuron) CNS CNS Multipolar Neuron (Motor Neuron) CNS Effector
- 16. PROPRIOCEPTORS • Sensory receptors situated on the nerve endings of the inner ear, muscles, skin, joints, tendons, and other tissues • Detect stretch or tension in skeletal muscles, tendons and joints • Maintain balance and posture Micrograph of a muscle spindle, a sensory receptor that conveys messages to the CNS about body position. 16
Editor's Notes
- Neuroglia (glia or glial cells) resemble neurons, but do not transmit impulses
- Myelin acts as an electrical insulator which greatly increases the speed of a nerve signal Unmyelinated axon conduction velocities range from about 0.5 to 10 m/s Myelinated axons can conduct impulses at velocities up to 150 m/s Source: https://www.ncbi.nlm.nih.gov/books/NBK10921/
- Another feature of myelinated neurons that speeds impulse transmission is the presence of gaps between Schwann cells These gaps, called Nodes of Ranvier, are the only sections of the axon where current flows, so the action potential actually jumps from node to node
- Dendrites of sensory neurons are usually associated with specialized receptors of the sense organs or of the skin (shown), muscles and tendons Students may recall sensory receptors in the skin include free nerve endings, Pacinian corpuscles, and Meissner’s corpuscles