BIO201 - Chapter 13 (Spinal Cord, Spinal Nerves, and Somatic Reflexes)
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Created by:
angelsheffield on November 7, 2011
Subjects:
biology, anatomy, physiology, nervous sytem, spinal cord, spinal nerves, somatic reflexes
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83 terms
Terms | Definitions |
|---|---|
 Foramen Magnum | The spinal cord extends from the |
| L1 | The spinal cord extends to |
| Central Nervous System | The spinal cord is a component of which system |
| Peripheral Nervous System | The spinal nerves are a component of which system |
| Conduction, Locomotion, Reflexes | 3 Functions of the Spinal Cord |
| Conduction | Bundles of fibers passing information up and down the spinal cord, connecting different levels of the trunk with each other and with the brain |
| Central Pattern Connectors | Pools of neurons providing control of flexors and extensors that cause alternating movements of the lower limbs |
| Reflexes | Involuntary, stereotyped responses to stimuli |
| 31 | Total pairs of spinal nerves |
| Cervical, Thoracic, Lumbar, Sacral | 4 Regions of Spinal Cord |
| Cervical Enlargement | Nerves to the upper limb |
| Lumbar Enlargement | Nerves to the pelvic region and lower limbs |
| Medullary Cone | Tapered tip of the spinal cord |
| Cauda Equinae | Bundle of nerve roots that occupy the vertebral canal from L2 to S5 (horse's tail) |
| Meninges | Three fibrous connective tissue membranes that enclose the brain and spinal cord |
| Dura Mater | Tough collagenous membrane surrounded by epidural space filled with fat and blood vessels |
| Arachnoid Mater | Layer of simple squamous epithelium lining the dura mater and loose mesh of fibers filled with CSF (creates subarachnoid space) |
| Pia Mater | Delicate membrane adherent to the spinal cord (should never penetrate this layer) |
| Subarachnoid Space | Comprised of a majority of CSF |
| Epidural Space, Dura Mater, Arachnoid Mater, Subarachnoid Space, Pia Mater | 5 Layers of Meninges in the Spinal Cord |
| Gray Matter | Neuron cell bodies with little myelin; site of information processing (synaptic integration) |
| White Matter | Abundantly myelinated axons; carry signals from one part of the CNS to another |
| Dorsal | Root of spinal nerve that is totally sensory fibers |
| Ventral | Root of spinal nerves that is totally motor fibers |
| Gray Commissure | Connects the dorsal and ventral roots of gray matter |
| Central Canal | Punctures the gray commissure; lined with ependymal cells and filled with CSF |
| White Column | Consists of bundles of myelinated axons that carry signals up and down, to and from the brainstem |
| Ascending Tracts | Tracts that carry sensory information up the spinal cord |
| Descending Tracts | Tracts that carry motor information down the spinal cord |
| Decussation | As the fibers pass up or down the brainstem and spinal cord they cross over from the left to the right side and vice versa |
| Contralateral | When the origin and destination of a tract are on opposite sides of the body |
| Ipsilateral | When the origin and destination of a tract are on the same side of the body |
| 3 | Number of neurons sensory signals travel across in ascending tracts |
| First Order Neurons | Detect stimulus and transmit signals to spinal cord or brainstem (in ascending tracts) |
| Second Order Neurons | Continues to the thalamus at the upper end of the brainstem (in ascending tracts) |
| Third Order Neurons | Carries the signal the rest of the way to the sensory region of the cerebral cortex (in ascending tracts) |
| Dorsal Column Pathway | Pathway that functions in deep touch, visceral pain, vibration, and proprioception |
| Proprioception | Nonvisual sense of the position and movements of the body |
| Spinothalmic Pathway | Pathway that functions in pain, pressure, temperature, light touch, tickle, and itch |
| Spinocerebellar Pathway | Proprioceptive signals from limbs and trunk travel up to provide the cerebellum with feedback needed to coordinate muscle actions |
| 2 | Number of neurons involved in descending tracts |
| Upper Motor Neuron | Originates in the cerebral cortex or brainstem and terminates on a lower motor neuron (descending tract) |
| Lower Motor Neuron | Axon leads the rest of the way to the muscle or other target organ (descending tract) |
| Corticospinal Tract | Descending tract from the cerebral cortex for precise, finely coordinated limb movements |
| Tectospinal Tract | Descending tract that functions as a reflex turning of the head in response to sights and sounds |
| Reticulospinal Tract | Descending tract that functions in controlling limb movements important to maintain posture and balance |
| Vestibulospinal Tract | Descending tract that functions in postural muscle activity in response to inner ear signals |
| Nerve | A bundle of nerve fibers (axons) |
| Epineurium | Covers a nerve |
| Perineurium | Surrounds a fascicle |
| Endoneurium | Separates individual nerve fibers |
| Perineurium | Blood vessels penetrate only the... |
| Neurilemma | Outer membrane formed by Schwann cells of a PNS nerve axon |
| Sensory (Afferent) Nerves | Carry signals from sensory receptors to the CNS |
| Motor (Efferent) Nerves | Carry signals from the CNS to muscles and glands |
| Mixed Nerves | Consist of both afferent and efferent fibers; conduct signals in two directions |
| Ganglion | Cluster of neurosomas outside of the CNS |
| Proximal Branches | Branches of nerves that includes the dorsal and ventral roots |
| Distal Branches | Branches of nerves that includes the dorsal and ventral ramus |
| Shingles | Skin eruptions along path of nerve; remains for life in dorsal root ganglia |
| Cervical Plexus | Plexus that supplies the neck and phrenic nerve to the diaphragm |
| Brachial Plexus | Plexus that supplies the upper limb and some of the shoulders and neck |
| Lumbar Plexus | Plexus that supplies the abdominal wall, anterior thigh and genitalia |
| Sacral Plexus | Plexus that supplies the remainder of the lower trunk and lower limb |
| Coccygeal Plexus | Plexus found on S4, S5 and C0 |
| Somatosensory Function | Plexuses carry signals from bones, joints, muscles, and skin |
| Dermatome | A specific area of the skin (cutaneous) that receives sensory input from a pair of spinal nerves |
| Require Stimulation, Quick, Involuntary, Stereotyped | 4 Properties of a Reflex |
| Conditioned Reflexes | Learned responses |
| Muscle Spindle | Stretch receptors embedded in skeletal muscles |
| Proprioceptors | Specialized sense organs to monitor the position and movement of the body parts |
| Length, Movement | Muscle spindles inform the brain of muscle... (2) |
| Intrafusal Fibers | Muscle fibers within a spindle |
| Stretch (Myotatic) Reflex | When a muscle is stretched, it contracts and maintains increased tonus; Knee-jerk reflex |
| Flexor (Withdrawal Reflex) | Quick contraction of flexor muscles resulting in the withdrawal of a limb from an injurious stimulus |
| Polysynaptic Reflex Arc | Pathway in which signals travel over many synapses on their way back to the muscle |
| Crossed Extensor Reflex | The contraction of extensor muscles in the limb opposite of the one that is withdrawn; maintains balance by extending the other leg |
| Ipsilateral Reflex Arc | Reflex arc in which the sensory input and the motor output are on the same sides of the spinal cord |
| Contralateral Reflex Arc | Reflex arc in which the input and output are on opposite sides of the spinal cord |
| Intersegmental Reflex | Reflex in which the input and output occur at different levels of the spinal cord |
| Tendon Organs | Proprioceptors in a tendon near its junction with a muscle |
| Golgi Tendon Organ | 1mm long, nerve fibers entwined in collagen fibers of the tendon |
| Tendon Reflex | Response to excessive tension on the tendon; inhibits muscle from contracting strongly; moderates muscle contraction before it tears a tendon or pulls it loose from the muscle or bone |
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