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The Spinal Cord Objectives

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The Spinal Cord Objectives The Spinal Cord Objectives ● Describe how the spinal cord is protected. ● Describe the structure and functions of the spinal cord. ● Explain the components of a reflex arc Protection ● Provided by: ○ vertebrae ○ meninges ○ cerebrospinal fluid The Meninges ● Three layers of connective tissue covering the brain and spinal cord. 1. Dura mater (“tough mother”) ● A tough dense irregular connective tissue. Helps protect the delicate structures of the CNS. Extends down to the 2nd sacral vertebra. 2. Arachnoid mater ● the middle layer ● resembles a spider’s web 3. Pia mater (“delicate mother”) ● a transparent layer of connective tissue that adheres to the surface of the spinal cord and brain. ● contains numerous blood vessels. Subarachnoid space ● The space between the arachnoid and pia mater. ● This is the location where cerebrospinal fluid (CSF) is located. Structure and Function of the Spinal Cord Gross Anatomy of the Spinal Cord ● In an adult the spinal cord is between 16 and 18 inches long. ● It runs from the base of the brain to the top of L2. ● Below the end of the spinal cord the nerves to the lower parts of the body travel on a bundle of nerves called the cauda equina, which means horse’s tail. Internal Structure of the Spinal Cord ● Gray matter: ○ darker, deeper center area of the spinal cord (looks like a butterfly) ○ Contains the cell bodies of neurons, neuroglia, and dendrites ● White matter: ○ Superficial portion of the spinal cord. ○ location where most axons are found Which part of the spinal cord do you think the pia mater would be in contact with? Exit slip ● What was one thing you: ○ learned today ○ found interesting ○ had a question about Other Structures Associated with the Spinal Cord ● Spinal nerves: ○ Paths of communication between the spinal cord and the nerves to that part of the body. ● Roots (nerve): ○ Are bundles of axons that connect the spinal nerve to the spinal cord. ■ Posterior (dorsal) root - ● contains only sensory axons. They carry sensation from the skin, muscles and internal organs into the central nervous system. ● Each posterior root has a swelling, the posterior (dorsal) root ganglion, that contains the cell bodies of the sensory neurons. ● ○ ■ Anterior (ventral) root ● contains axons of somatic motor neurons - connecting the CNS to skeletal muscles and ● axons of autonomic motor neurons - connecting the CNS to smooth muscle, cardiac muscle, and glands. Review questions Why does your Dr. hit you on the knee? Does thinking about what the Dr. is doing alter the results? Reflex Lab Warm up 1. What do we call the bundle of axons that carry sensory information into the spinal cord from the spinal nerve? 2. Where do we find the cell bodies of motor neurons in the spinal cord? What is the function of the Spinal Cord? Spinal Cord Function 1. The white matter serves as highways for nerve impulse conduction. With sensory impulses traveling toward the brain and motor impulses traveling away from the brain. 2. The gray matter of the spinal cord receives and integrates (analyzes) incoming and outgoing information. It is also the site of integrating reflexes. How would you describe a reflex? Spinal Reflexes ● A reflex is a fast involuntary sequence of actions that occur in response to a particular stimulus. Ex. pulling your hand away from a hot surface (a withdrawal reflex). ● A reflex arc is the pathway nerve impulses follow producing a reflex. Step in a Spinal Reflex Arc 1. Sensory receptors - ● The distal ends of sensory neurons serve as sensory receptors and respond to a specific stimulus by generating nerve impulses. 2. Sensory neuron ● The nerve impulse generated by the sensory receptor travels along the axon of a sensory neuron to the axon terminals in the gray matter of the spinal cord. 3. Integrating center ● One or more regions of gray matter act as an integrating center. May include interneurons. 4. Motor neuron ● Impulses triggered by the integrating centers pass out of the spinal cord along a motor neuron to the part of the body that will respond. 5. Effector ● The part of the body that responds to the motor nerve impulse (a muscle or a gland). It creates the reflex. Review.
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