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What are the 2 components (layers) of the enteric nervous system? Although they recieve autonomic input, what are enteric neurons capable of?
The two layers are the myenteric plexus and the submucosal plexus. Enteric neurons are capable of autonomous regulation of gut motility.
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What does the CNS consist of and what is it responsible for? How about the PNS? What are the two types of nerves in the PNS?
central nervous system: brain and spinal cord, responsible for final decision making; peripheral nervous system: peripheral ganglia and nerves, cranial nerves and spinal nerves
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What do Spinal nerves serve? How about cranial nerves? What two branches does each group of nerves have?
SPinal nerves serve the trunk and extremities. Cranial nerves serve the head region. Each have a somatic and autonomic branch
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Define afferent vs efferent neurons. Describe the somatic (sensory) afferent information and autonomic (visceral) afferent information. Describe the somatic (motor) efferent information and the autonomic (visceral) afferent information.
Afferent: carry information to the CNS; Somatic afferents include touch, pain, pressure, vibration, temp, and propioception in the skin, body wall, and limbs. Also hearing, equilibrium, vision, and smell; Autonomic afferents include stretch, pain, temp. and chemical changes in the viscera, nausea, hunger and taste.; Efferent: carry info away from CNS; Somatic efferents include motor innervation to all skeletal muscles. Autonomic (visceral) efferents include any motor innervation to smooth muscle, cardiac muscle, or glands. Has two branches Sympathetic and Parasympathetic.
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Where are these structures on a neuron and what are the functions? (nucleus, axon, axon terminals, dendrites)
Nuclues is located in the cell body and is the site of protein synthesis. Axon extends for long distances to the target. Axon terminals contact target cells (muscles, glands or other neurons) and at the synapses, release neurotransmitters. Dendrites recieve information from other neurons.
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Do neurons divide?
No they are post-mitotic cells and do not divide.
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What are the different structural types of neurons? What types of neurons are found in each category typically?
1. Bipolar: Two ends with a body in the middle. Ends can be axon and dendrite or two axons, specialized sensory neurons.; 2. Unipolar: No dendrites. Just a head and one axon, typically sensory neurons. 3. Multipolor: Many dendrites, usually motor or interneurons.
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What are interneurons?
Interneurons conduct impulses between neurons. Most neurons (over 99%) are in this class.
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Define nucleus vs. ganglion.
Nucleus is a cluster of neuron cell bodies in the CNS. Ganglion is a cluster of neuron cell bodies of the PNS.
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Define tract vs. nerve.
Tract is a group of axons in the CNS. Nerve is a group of axons in the PNS.
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Define grey matter vs. white matter.
These are terms to describe CNS tissue. Grey matter are areas that contain mainly call bodies. White matter contain mostly axon.
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What is a plexus?
A plexus is a region where nerve fibers mix and resort.
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What are the main components of the brain? Where do they lie?
Cerebral cortex is on the outter surface. Cerebellum is at the back of the head and controls fine tuning of motor coordination. The corpus callosum is in the center and connects the two hemispheres of the cerebral cortex. The brainstem is below that and contains the midbrain, pons, and medulla. The spinal cord starts inferior to the medulla.
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What are the lobes of the brain? What do they specialize in?
Frontal lobe: Primary motor cortex, prefrontal working memory, broca's speech area; Parietal lobe: somatosensory cortex; Occipital lobe: visual cortex; Temporal lobe: auditory cortex and memory
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What do somatic fibers innervate? How about autonomic fibers? Do they only exist for PNS?
The CNS and PNS each have somatic and autonomic fibers. Somatic fibers innervate skin and skeletal muscles. Autonomic fibers innervate viscera which includes any organs with smooth muscle, cardiac muscle and glands.
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Where do Cranial Nerves originate? Where do they innervate? How many are there?
There are 12 cranial nerves. They originiate from the brain and lead to the head neck or trunk of the upper body.
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CN I
Olfactory nerve: sensory only- smell
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CN II
Optic nerve: sensory only- vision
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CN III
Oculomotor nerve: motor- eye movements, parasympathetic constriction of pupils
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CN IV
Trochlear nerve: motor only- eye muscle
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CN V
Trigeminal nerve: motor- muscles of mastication, sensory- head and face
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CN VI
Abducens nerve: motor only- eye muscle
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CN VII
Facial nerve: motor- muscles of the face, parasympathetic lacrimal, salivary and nasal glands
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CN VIII
Vestibulocochlear nerve: balance (vestibular) head position and movement, hearing (cochlear)
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CN IX
Glossopharyngeal nerve: taste and sensory of lining in the throat, parasympathetic involving blood pressure
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CN X
Vagus nerve: motor- larynx, pharynxm and soft palate for swallowing, parasympathetic- to gut for gastric secretion and movement, slows heart rate, afferent- from thoracic and abdominal viscera
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CN XI
Accessory nerve: motor only- sternocleidomastoid and trapezius
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CN XII
Hypoglossal nerve: motor only- tongue muscles.
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What the the 12 cranial nerves? (do not have to do function of each right now)
1. Olfactory; 2. Optic; 3. Oculomotor; 4. Trochlear; 5. Trigeminal; 6. Abducens; 7. Facial; 8. Vestibulocochlear; 9. Glossopharyngeal; 10. Vagus; 11. Accessory; 12. Hypoglossal
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How many spinal nerves are there? How many of each type?
31 pairs of spinal nerves. 8 cervical (c1-c8), 12 thoracic (t1-t12), 5 lumbar (l1-l5), 5 sacral (s1-s5), 1 coccygeal (coccyx)
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What does the anterior root contain? posterior (dorsal root)? Where do they converge? Where does the dorsal ramus go? Ventral ramus?
Anterior (ventral) root contains purely motor neurons. Posterior (dorsal) root contains purely sensory neurons. They converge at the dorsal root ganglion. Dorsal ramus goes to the back. Ventral ramus goes to the front and the extremities.
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Explain what it means for the spinal system to be segmentally organized.
Upper parts of the cord innervate upper regions of the body, while the lower spinal cord provide innervation to lower regions of the trunk and extremities.
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Describe the pathway for somatic motor neurons versus the somatic afferent system. Make sure to explain where the cell bodies lie for each system.
Page 24 and 26 of the notes.
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What are signs of lower motor neuron damage? Typical causes?
Flaccid paralysis of muscles, hypotonicity (loss of muscle tone), loss of stretch reflex. Typically caused by a knife cut or prolapse of intervertebral disc
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Where do upper motor neurons originate and innervate? What are signs of upper motor neuron injury?
Upper motor neurons originate in the motor centers of the cerebral cortex or the red nucleus of the midbrain. Their axons travel down tracts and synapse on lower motor neurons on the ventral horn of the spinal cord. SIgns of upper motor neuron damage include spasticity, rigor, loss of voluntary movement or exaggerated/aberrant reflexes (Babinski Sign). Typically caused my damage to the spinal cord or stroke.
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What are visceral afferents? Are they part of the autonomic nervous system?
These are nerves that conduct sensory impulses such as pain, blood pressure, info about blood gas from visceral organs to the CNS. Axons will typically leave the spinal nerves and travel with autonomic fibers to reach visceral organs. They are NOT part of the autonomic nervous system.
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