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168 Cards in this Set
- Front
- Back
How many layers is the spinal cord made up of?
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two
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What do the layers of the spinal cord consist of?
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an outer layer of white matter and an inner layer of gray matter
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Is grey matter or white matter unmyelinated?
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grey
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What does it mean if the white matter is myelinated?
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this is where the axons ar
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How many pairs of spinal nerves are there?
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31
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Where do the spinal nerves emerge from?
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the intervertebral foramina
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Where do spinal nerves get their name from?
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the vertebra that is superior to it
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How many pairs of cervical nerves are there?
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8
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How many pairs of thoracic nerves are there?
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12
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How many pairs of lumbar nerves are there?
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5
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How many pairs of sacral nerves are there?
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5 pairs
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How many pairs of coccygeal nerves are there?
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1 pair (Co1)
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What is the intervertebral foramina?
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the space between the vertebrae and the spinal cord that ends between L1 and L2
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What is the cauda equina?
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the filum terminale, ventral, dorsal roots
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What is the filum terminale?
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fibrous tissue that extends from the inferior tip of the conus medullaris to the second sacral vertebra
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What is the purpose of the filum terminale?
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to provide support to the spinal cord as a component of the coccygeal ligament
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What does a spinal nerve contain?
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the axons of sensory and motor neurons
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Where do sensory fibers enter the CNS?
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the dorsal root
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What does the dorsal root ganglion contain?
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cell bodies of sensory neurons whose axons carry information to the spinal cord
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What does the dorsal root contain?
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axons of neurons whose cell bodies are in the dorsal root ganglion
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What does the ventral root contain?
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axons of motor neurons that extend into the periphery to control somatic and visceral effectors
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Where is gray matter located?
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near the narrow central canal and forms an H shape
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Where does the spinal cord end?
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between L1 and L2
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Where is the amount of gray matter in the spinal cord greatest?
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in areas dedicated to sensory and motor control of the limbs
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What three layers do the meninges consist of?
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the dura mater, arachnoid mater, and pia mater
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What is the purpose of the meninges?
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provides physical stability and shock absorption
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How does the spinal cord obtain oxygen and nutrients?
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through blood vessels located in the meninges
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What meninges are the spinal meninges continuous with?
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the cranial meninges
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What does the subarachnoid space consist of?
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subarachnoid trabeculae which are a network of collagen and elastic fibers that attach the arachnoid mater to the pia mater
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What is the subarachnoid space filled with?
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cerebrospinal fluid
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What is the purpose of the cerebrospinal fluid?
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Acts as a shock absorber and diffusion medium for dissolved gases, nutrients, chemical messengers, and waste products
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What does the epidural space contain?
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areolar tissue, blood vessels, and a protective padding of adipose tissue
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What type of fibers does the dura mater consist of?
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dense collagen
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What seperates the dura mater from the arachnoid mater?
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the subdural space
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What is the arachnoid mater composed of?
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simple squamous epithileum
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What seperates the arachnoid mater from the pia mater?
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the subarachnoid space
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What does the pia mater consist of?
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elastic and collagen fibers that are firmly bound to underlying neural tissue
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What type of sensory nuclei does the posterior gray horn contain?
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somatic and visceral
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waht type of nuclei does the lateral gray horn contain?
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viseral motor
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What type of nucei dowes the anterior gray horn contain?
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somatic motor
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What are cell bodies of neurons in the gray matter of the spinal cord organized into?
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nuclei
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What two types of nuclei are there?
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sensory and motor
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What do sensory nuclei do?
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they recieve and relay sensory information from peripheral receptors
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What do motor nuclei do?
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they issue motor commands to teh peripheral effectors
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How is white and grey matter organized?
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according to the region of the body innervated by it
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How is white matter organized?
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into columns which contain tracts
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What are tracts
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bundles of axons in white matter that are relatively uniform in respect to diameter, myelination, and conduction speed
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What type of tracts carry sensory info to the brain?
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ascending tracts
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What type of tracts convey motor commands to the spinal cord?
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descending tracts
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How many columns are there in white matter and what are they?
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3--the posterior, lateral and anterior
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How are segments of the spinal cord connected?
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by a pair of spinal nerves
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What are spinal nerves surrounded by?
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connective tissue layers continuous with peripheral nerves
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What are the three layers of the connective tissue that surround a spinal nerve?
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the epineurium, perineurium, and endoneurium
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what does the epineurium consist of
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collagen fibers
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What does the perineurium do?
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divides teh nerve into a series of compartments that contain bundles of axons (fascicles)
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What are rami?
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what each spinal nerve branches out to form
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What does the dorsal ramus innervate?
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muscles, joints, skin of the back
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What does the ventral ramus innervate?
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structures in the lateral and anterior trunk as well as the limbs
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Where are communicated rami present?
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in the thoracic and superior lumbar segments of the spinal cord
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What are the three types of rami?
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dorsal, ventral, communicating
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What is the specific region of the skin monitored by a single pair of spinal nerves known as?
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a dermatome
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Do adjacent dermatomes overlap?
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yes
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What creates a loss of sensation in the skin?
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damage or infection of a spinal nerve or dorsal root ganglion
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What is the purpose of each ramus?
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to provide sensory and motor innervation to a specific region
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What does the central nervous system consist of?
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the brain and spinal cord
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What does the peripheral nervous system consist of?
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all neural tissue outside the CNS
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Compare sensory vs. motor
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sensory brings information from the PNS to the CNS from receptors in peripheral tissues and organs where the motor division of the PNS carries motor commands from the CNS to peripheral tissues and systems
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What is the difference between somatic and autonomic regulation?
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somatic controls skeletal muscle contractions where autonomic controls smooth muscle, cardiac muscle, glands and adipose tissue
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What does the ventral root of each spinal nerve contain?
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axons of somatic motor and visceral motor neurons
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Can we control visceral or somatic contractions?
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somatic
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What do columns contain?
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bundles of axons that have a common origin/destination
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Do bundles of tracts carry similar information?
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yes
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What are branches of a spinal nerve called?
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rami
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What is the filium terminale?
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connective tissue that connects the conus medullans to the coccyx
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What does the dorsal ramus contain?
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somatic motor and visceral motor fibrs that innervate the skin and skeletal muscles of the back
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What does the ventral ramus contain?
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axons that supply the ventrolateral body surface, structures in the body wall, and the limbs
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What are rami communicates?
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the white and gray rami
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Which ramus is the first branch from the spinal nerve and carreis visceral motor fibers to a nearby sympathetic ganglion?
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the white
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What does the white ramus consist of?
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postganglionic fibers that innervate glands and smooth muscles in the body wall or limbs
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What does the sympathetic nerve contain?
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preganglionic and postganglionic fibers that innervate structures in the thoracic cavity
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Do pre or post ganglionic fibers go to smooth muscles, glands, and visceral organs?
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postganglionic fibers
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How does somatic sensory information arrive?
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through the dorsal and ventral rami
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How does visceral sensory information reach the dorsal root?
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through dorsal, ventral, and white rami
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What are the branches of a typical spinal nerve?
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dorsal ramus, ventral ramus, and rami communicantes
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What region does the dorsal ramus provide sensory and motor innervation to?
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deep muscles and skin of dorsal surface of trunk
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Which ramus supplies motor and sensory innervation to skeletal muscles of upper/lower limbs and skin of lateral and ventral trunk surfaces?
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the ventral ramus
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What is the purpose of a sympathetic nerve?
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innervate the abdominopelvic viscera, smooth muscles, glands, and visceral organs in the thoracic cavity
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Where is sensory info collected from peripheral structures delivered?
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thoracic and superior lumbar segments of the spinal cord
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Where does somatic sensory information arrive in the spinal cord?
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through the dorsal and ventral rami
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Where does visceral sensory information arrive from
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dorsal, ventral and white rami
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What carries sensory info from the visceral organs?
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the sympathetic nerve
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What is the function of nerve plexuses?
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innervate skin and skeletal muscles
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Which nerve plexus is the smallest?
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the cervical
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What is a nerve plexus?
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complex interwoven network of peripheral nerves nerves that contain components of several spinal nerves
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What are the four groups of plexuses?
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cervical, brachial, lumbar, and sacral
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What does the cervical plexus consist of?
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ventral rami of spinal nerves C1-C5
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What does the cervical plexus innervate?
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muscles of the neck that extend into the thoracic cavity
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What does the brachial plexus innervate?
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the pectoral girdle and upper limbs
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What does the brachial plexus consist of?
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ventral rami of spinal nerves C4-T1
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Where do the nerves that form the brachial plexus originate from?
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trunks and cords
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What do the lumbar and sacral pluxuses innervate?
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the skin and skeletal muscles of the trunk and lower limbs
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What are neuronal pools?
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functional groups of interconnected neurons
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What tells the functional characteristics of a neuronal pool
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the pattern of interaction among neurons
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What are the five different neural circuits?
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divergence, parallel, serial, convergence, and reverberation
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What occurs in divergence?
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spread of info from one neuron to several neurons
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When does divergence occur?
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When sensory neurons bring information into the CNS
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What occurs in parallel processing?
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several neurons or neuronal pools process the same info simultaneously
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How is info relayed in serial processing?
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stepwise fashion, from one neuron to anohter
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What occurs in convergence?
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several neurons synapse on a single postsynaptic neuron
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In what type of neural circuit can motor neurons be suject to both conscious and unconcious control?
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convergent
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What occurs in a reverberation circuit?
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branches of axons somewhere in the circuit extend back to the circuit
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Which type of circuit is like a positive feedback loop?
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reverberation
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What are reflexes?
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preprogrammed responses to specific stimuli
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What are the simplest circuits?
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reflexes
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Where do reflexes occur?
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in the PNS and spinal cord
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What happens each time a particular reflex is activated?
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it produces the same motor response
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How can reflexes be classified?
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by development, response, complexity of circuit, or processing site
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How do neural reflexes work?
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sensory fibers deliver information from peripheral receptors to an integration center in the CNS
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What are the possible receptors of a sensory neuron?
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a specialized cell or dendrites of a sensory neuron
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What are receptors sensitive to?
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Physical or chemical changes in the body or changes in the external environment
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Write out the steps of a reflex
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.....on paper
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what is the wiring of a single reflex called?
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a reflex arc
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Where does a reflex arc begin and end?
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begins at a receptor and ends at a peripheral efector
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What is the difference between innate and acquired reflexes?
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innate reflexes are genetically or developmentally determined where acquired reflexes are learned
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Which reflex is enhanced by repetition?
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acquired reflexes
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What type of reflex is chewing or withdrawl of your hand from pain?
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innate reflex
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Compare somatic reflexes to visceral reflexes.
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somatic reflexes control skeletal muscle contractions where visceral reflexes control actions of smooth and cardiac muscles and glands
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What type of reflexes are superficial and stretch reflexes?
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somatic
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Are the categories of reflexes mutually exclusive?
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NO
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Compare monosynaptic and polysynaptic reflexes.
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Monosynapic-one synapse in the CNS, delay between the stimulus and response is minimized
Polysynaptic-multiple synapses (two to several hundred); longer delay between the stimulus and response |
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What determines the length of delay in a polysynaptic reflex?
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the greater the number of synapses, the greater the length of delay
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Compare spinal and cranial reflexes.
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Spinal reflexes are processed in the spinal cord; crania reflexes are processed in the brain
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What type of reflex is a stretch reflex?
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monosynaptic
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What is the function of a stretch reflex?
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provides automatic regulation of skeletal muscle length
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Write down the 5 steps of a stretch reflex.
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.....write it.
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What are the sensory receptors involved in a stretch reflex?
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muscle spindles
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What does each muscle spindle consist of?
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small, specialized skeletal muscle fibers-->intrafusal muscle fibers
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How long does it take for the an entire stretch reflex to be completed?
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20-40 msec
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What is each muscle spindle innervated by?
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gamma motor neurons
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What is the function of gamma motor neurons?
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control the sensitivity of a muscle spindle by altering tension in the intrafusal fibers of a muscle spindle
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How does the CNS increase or decrease muscle tone when movements are underway in a stretch reflex?
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with the gamma motor neurons
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In a stretch reflex, what does stretchng the central portion of an intrafusal fiber do?
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distorts the dendrites and stimulates the sensory neuron which stimulates the motor neurons which increases the muscle tone
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in a stretch reflex, what does compressing the central portion of the intrafusal fiber do?
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inhibits the sensory neurons therefore muscle tone decreases
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What type of reflex are many stretch receptors?
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postural reflexes
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What is the function of postural reflexes?
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reflexes that help us maintain a normal, upright posture
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What type of reflexes are withdrawl and crossed extensor reflexes?
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polysynaptic
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What is the function of withdrawl reflexes?
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move affected parts of the body away from a stimulus
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What happens when pain receptors are stimulated?
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sensory neurons activate interneurons in the spinal cord that stimulate motor neurons in the anterior gray horns-->ultimatelyh resulting in contraction of flexor muscles that moves body away from source of pain
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What happens to opposing muscles when a specific muscle contracts?
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they relax (reciprocal inhibition)
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Why are withdrawl reflexes so versatile?
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the sensory neurons activate many pools of interneurons
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In withdrawl reflexes, what does the intensity and location of the stimulus determine?
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theh distribution of the effects and the strength and character of the motor responses
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What type of reflex arc do stretch and withdrawl reflexes involvee
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ipsilateral (same side)
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What occurs in an ipsilateral reflex arc?
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the sensory stimulus and motor response occur on the same side of the body
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What type of reflex arc does a crossed extensor reflex involve?
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a contralateral reflex arc
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What occus in a contralateral reflex arc?
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an additional motor response occurs on the opposite side of the stimulus
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What are the five properties of polysynaptic reflexes?
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1. involve pools of interneurons
2. intersegmental in distribution 3. involve reciprocal inhibition 4. have reverberating circuits (prolong reflexive motor response) 5. several reflexes may cooperate to produce a coordinated, controlled response |
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What effect does the brain have on the performance of a reflex?
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it facilitates or inhibits motor neurons or interneurons involved
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What is reinforcement?
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facilitation of motor neurons involved in reflexes
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Why are stretch reflexes such as the biceps reflex tested during a physical exam?
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each reflex is controlled by specific segments of the spinal cord, tests whether the segments of the spinal cord are functioning correctly
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Of the 31 segments of the spinal cord, how are they categorized?
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8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
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Where does the spinal cord end?
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between vertebrae L1 and L2
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What structures serve as anchors to prevent excessive movement of the spinal cord?
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the denticulate ligaments
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What is the function of the spinal cord?
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serves as an information pathway between the brain and the spinal nerves and as an integration center
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What do the ascending and descending tracts of the white matter in the spinal cord serve as?
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communication links between the spinal nerves and the sensory and motor areas in the brain
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What are the five elements of a reflex arc?
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1. sensory receptor
2. sensory neuron 3. integration center in the CNS 4.motor neuron 5. effector organ |
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What are the receptors involved in a stretch reflex?
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muscle spindles
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What occurs in a stretch reflex when a muscle is stretched?
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the muscle spindles are elongated, a reflex muscle contraction will occur, excessive stretching of the muscle will be prevented
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What types of neurons does a single spinal nerve contain?
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sensory and motor
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