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70 Cards in this Set
- Front
- Back
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How long is the average adult spinal cord?
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18 inches
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Where are the two locations of enlargement of the spinal cord? Why?
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The cervical and lumbar enlargements. Increased gray matter to facilitate in interneuron communication.
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What are the two indentations in the ventral and dorsal spinal cord called?
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The anterior median fissure and the posterior median sulcus.
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Where is the conus medullaris? Where does the filum terminale attach?
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At L1. It attaches at the second or third sacral segment.
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How man spinal cord segments are there?
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31: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccyx
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Where does the dorsal root ganglia lie in relation to the pedicle?
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Directly inferior to it.
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What is the Bell-Magendie law?
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The concept that ventral grey matter in the spinal cord carries motor information and dorsal grey matter carries sensory information.
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What are the three types of connective tissue around the spinal nerves (and all nerves, for that matter)? What does the outermost layer coalesce into when the nerve attaches to the spinal cord?
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The endoneurium surrounds a bundle of axons. The perineurium surrounds various bundles and associated vasculature. The epineurium is a tough layer of collagen that encapsulates the whole nerve. This coalesces with the dura mater near the spinal cord.
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Give an example of a monosynaptic and a polysynaptic reflex.
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Monosynaptic reflexes include the modulation of muscle tone from stretch and includes the patellar stretch reflex.
Polysynaptic reflexes have at least one interneuron in the spinal cord. The withdrawal reflex is an example. |
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What kinds of sensation do the posterior columns relay to the brain?
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Fine touch, pressure, vibratory and proprioceptive information.
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Describe the flow of vibratory, fine touch, and proprioceptive information from the DRG to the somatosensory cortex
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From the DRG to the fasciculus gracilis (legs) or fasciculus cuneatus (arms), ascend ipsilaterally to synapse on the nucleus cuneatus and nucleus gracilis in the medulla oblongata. Immediately decussate. Ascend up the now contralateral medial lemniscus tract up to the ventral posterolateral thalamus. From there, project to the postcentral (somatosensory) gyrus, forming the homunchulus, which is lateral-most the face and larynx and medial and inferior-most the feet and genitalia. The knees go over the sagittal fissure.
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Describe the path of the spinothalamic tract from DRG to the somatosensory cortex and other higher order brain regions.
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From the DRG to synapse at the dorsal horn of the grey matter. There decussate at that level or one or two above over the anterior white commissure. From there, pain and temperature sensations go to the lateral spinothalamic tract. Touch goes to the anterior spinothalamic tract. These then ascend to the ventral posterolateral thalamus and synapse again. From there, they go to the postcentral gyrus, the cingulate, and the insula.
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From a stimulus/response standpoint, describe those signals carried by the spinothalamic tract.
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They carry signals that provide a compulsion to act. For example, to move away from heat or pain, to scratch an itch, etc.
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Describe how information from the golgi tendon organs, intrafusal muscle fibers, and joint capsules reach the brain.
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They send signals up to the dorsal horn. Synapses are made there. Some fibers decussate over the anterior white commissure, go to the anterior spinocerebellar tract, travel up the the brain stem and enter the cerebellum from the superior cerebellar peduncle. Other fibers remain ipsilateral, travel to the posterior spinocerebellar tract, and enter the ipsilaterdal inferior cerebellar peduncle.
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What are the three tracts that make up the pyramidal system?
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1) Corticobulbar tracts, 2) Anterior corticospinal, 3) Lateral corticospinal
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Describe the pathways of the lateral and anterior corticospinal tracts and their relative functions.
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Both originate from the pyramidal cells of layer V of the primary motor cortex, (precentral gyrus), supplementary motor cortex, and other areas of the brain. They travel via the posterior limb of the internal capsule, down to the brainstem. About 80% decussate at the medulla oblongata (pyramidal decussations). These then travel along the lateral corticospinal tract before synapsing at the ventral horn. They are responsible for appendicular fine movements. 10% of the fibers do not decussate in the medulla but travel along the anterior corticospinal tract. They will then decussate at level over the anterior white commissure, synapse with the ventral horn, and exit out the ventral spinal root. These are responsible for axial movement. 10% of the fibers remain ipsilateral and travel along the lateral corticospinal tract.
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Describe the function of the corticobulbar tract and its pathway.
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Responsible for the movements of the face/laryngopharynx. From the primary motor cortex, supplementary motor cortex, etc, down the posterior limb of the internal capsule, to synapse with the cranial nerve nuclei of CN III, IV, VI, VII, IX, and XII.
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What is the main function of the extrapyramidal system?
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To coordinate and process subconscious motor activity.
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What are the most important nuclei of the extrapyramidal system?
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All are important. Waldman's states that the "cerebral nuclei", i.e. the basal ganglia (caudate, putamen, globus pallidus) are the most important.
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List the four major extrapyramidal tracts and their functions:
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1) Tectospinal tract: from the tectum, containing the superior and inferior colliculi. Responsible for moving the head, eyes, body, in response to loud sounds, bright lights, etc.
2) Rubrospinal tract: from the red nucleus in the midbrain. Decussates in the tegmentum and travels along the lateral corticospinal tract, terminating in the cervical spine. Responsible for maintenance of muscle tone in the upper extremities and primarily flexion, hence decerebrate posturing (extension of the upper extremities) with lesions below the red nucleus. 3) Vestibulospinal tract: from the medial and lateral vestibular nuclei in the pons and upper medulla. The medial tract goes ipsi and contralaterally along the medial vestibulospinal tract to innervate the ventral horn of the cervical spine. The lateral vestibulospinal tract does not decussate and runs to the lumbar spine. 4) Reticulospinal tract: modulates muscle tone and provides a primarily extensor bias (hence also decerebrate posturing |
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Besides modulation of motor control, what other two things does the reticulospinal tract do?
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Provides an outflow and modulation of sympathetic signals going from the thalamus to the throacolumbar sympathetic outflow (T1-L2) and sacral parasympathetics.
It is also responsible for modulating subconsious pain motor responses. |
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Where are the three neuronal somata of the sympathetic nervous system, starting in the cord?
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1) Preganglionic fibers which have their cell bodies in the the intermediolateral gray of the spinal cord from T1-L2
2) Ganglionic fibers which arise from the paravertebral ganglia or from collateral ganglia. 3) Neurons of the adrenal medulla |
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Give the main functions of the sympathetic nervous system.
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1) Increased pain threshold
2) Stimulation of the reticular activating system causing increased alertness 3) Increased BP 4) Increased cardiac inotropy and rate 5) Increased respiratory rate and depth 6) Energy mobilization by increased lipolysis in adipose, and glycogenolysis in the muscle and liver. 7) Sensation of euphoria 8) Increased muscle tone via stimulation of the extrapyramidal system. |
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What levels of the thoracolumbar sympathetic chain innervate the adrenal medulla?
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Levels T3-T8
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What levels of the thoracolumbar sympathetic chain make up the celiac ganglia? What organs does this innervate?
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T5-T11. Innervates the stomach, abdominal vasculature, pancreas, liver and bile duct, adrenal glands, and small intestines. Via the superior mesenteric nerve, it innervates the large intestines.
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What levels of the thoracolumbar sympathetic chain make up the inferior mesenteric ganglia? What organs to these innervate?
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T12-L2. The ganglia sits by the origin of the inferior mesenteric artery. The rectum, kidney, and bladder are innervated.
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Describe the neurotransmitters of the sympathetic nervous system, their receptors, and notable exceptions.
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Typically preganglionic fibers synapse with postganglionic fibers using acetylcholine and nicotinic receptors. Postganglionic fibers synapse with target organs using epinephrine or norepinephrine. Exceptions include the sweat glands, in which pregangionic fibers directly synapse with it with acetylcholine using a muscarinic receptor. Blood vessels in skeletal musculature have beta 2 receptors instead of alpha 1 receptors, thus allowing for vasodilation.
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What are the three main sympathetic collateral ganglia? Are these paired or unpaired?
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The celiac, superior mesenteric, and inferior mesenteric.
Unpaired (i.e. singluar) |
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Describe the differences in "divergence" between sympathetic and parasympathetic preganglionic synapses.
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Parasympathetic ganglia synapses are much more circumscribed (max 7-8) synapses, leading to a much more focal response. Sympathetic synapses are much broader with more synapses.
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Where are the parasympathetic nuclei of the spinal cord located?
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The intermediolateral horns of S2-4.
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List the 6 major parasympathetic ganglia, their location, their corresponding nerves, and their function.
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1) Ciliary ganglia: Posterior orbit. CN3 from the Edinger-Westphal nucleus. Constrict the pupil
2) Sphenopalatine ganglia/Pterygopalatine ganglia: In the pterygopalatine fossa. CN VII. Increase output of nasal glands, tear ducts, salivary glands. 3) Submandibular ganglia: Above the submandibular gland on the hyoglossus muscle. CN VII. Same as sphenopalatine. 4) Otic ganglion: Immediately below the foramen ovale. CN IX. increase secretion of the parotid gland 5) Terminal ganglia: Various locations. CN X. Increase blood flow and rest/relax activities of the visceral organs of the head, neck, thoracic cavity, and abdominal cavity. 6) Terminal/intramural ganglion: Various locations. From the sacral parasympathetic plexuses. Innervate visceral organs of the lower abdominopelvic cavity. |
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Name the three broad categories of nociceptors
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1) Thermoreceptors
2) Mechanoreceptors 3) Chemoreceptors: such as to cytokines like substance P |
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What class of nerve mediates sharp pain? What is it's course to the primary somatosensory and retircular areas?
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A-delta fibers, which are myelinated. Go up the contralateral spinothalamic tract to the VPL nucleus of the thalamus to the reticular area and the postcentral gyrus.
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What fibers carry dull pain? What is their pathway?
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The unmyelinated C fibers. The same pathway as A-delta fibers.
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What are thermoreceptors composed of?
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exposed nerve endings from C and A delta nerve fibers
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What organs are thermoreceptors located in?
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The skin, skeletal muscles, liver, and hypothalamus
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What is the ratio of cold versus heat thermorecptoms
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about 3.5x more cold thermoreceptors
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What is the pathway from the receiving end of the thermoreceptor to the brain?
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From the exposed fiber up the C and A delta nerves, to the dorsal horn, decussate to the lateral spinothalamic tract, up to the VPL thalamus and reticular formation, to the somatosensory cortex.
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Why are thermoreceptors called "phasic"?
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They respond rapidly to temperature changes but then quickly habituate, attenuating their firing.
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What are the three main functional types of mechanoreceptors and their most common type in the skin?
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1) Tactile: Pacinian/lamellar corpuscles, Meissner's corpuscles, Merkel's disks, Ruffini corpuscles, free nerve endings
2) Baroreceptors: Merkel's disk as well. Throughout the vasculature. 3) Prioprioceptors: golgi tendon organs, intrafusal muscle fibers. |
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What are the two broad structural classes of mechanoreceptors?
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Encapsulated and unencapsulated mechanoreceptors.
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What are the three types of encapsulated mechanoreceptors?
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1) Pacinian corpuscles
2) Meissner's corpuscles 3) Ruffinian corpuscles |
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What are the three types of unencapsulated corpuscles?
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1) Merkel's discs
2) Free nerve endings 3) Root hair plexuses |
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Where are Meissner's corpuscles found and what do they do?
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In areas of heightened sensitivity. Very adaptable and sensitive to fine touch, vibration, etc. Found in nipples, lips, genitalia, fingertips, and eyelids.
They are in the superficial subcutaneous tissue just beneath the epidermis/dermal villae. |
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What do the Pacinian corpuscles do and where are they found?
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They are the largest of the encapsulated mechanoreceptors. They are found in the junction of the dermis/subcutaneous fat as well as bones, joints, fascia, and visceral organs. They respond more to firmer touch and vibration.
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Where are the Ruffinian corpuscles found and what do they do?
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In the dermis. They are stretch receptors and tonic, not phasic. They do not slow their signaling much with time.
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Where are the Merkel's discs found? What do they do?
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In the stratum germinativum of the skin. Typically by Meisner's corpuscles. They are more grouped around hair follicles. They respond to very fine touch, localization, and pressure. Unlike Meisner's corpuscles, they are slow-reacting.
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Where do the mechanoreceptors composed of free nerve endings reside?
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in the villi of the dermis
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What do the hair root plexus do?
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Sense broad shifts in the dermis and are highly adaptable/phasic. Think that you only feel your clothes when they're moving on you.
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How do baroreceptors work? Where are baroreceptors located?
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They are free nerve endings that sense stretch (like Merkel's discs for the skin). They are located throughout the respiratory, GI, and GU tract. They are highly focused in the carotid and aortic sinuses so as to monitor homeostasis.
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What are the two main types of proprioceptors?
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Golgi tendon organs and intrafusal fibers/muscle spindles
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Where are the main locations of chemoreceptrs. What do they measure respectively?
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In the medulla they respond to carbon dioxide and hydrogen. In the carotid and aortic bodies they respond to CO2 and O2 levels. They can signal, via CNs IX and X, changes in respiration so as to correct the levels.
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What two guys proposed the gate control theory of pain?
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Melzack and Wall (1965)
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Name three mechanisms thought to cause the gate control theory of pain
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1) Non-nociceptive A-beta fibers enter the dorsal root entry zone at the same location as unmyelinated C fibers. These directly inhibit the C fibers from transmitting cephalad.
2) Stimulation of neurons in the periaqueductal gray areas have inferiorly-directed signaling that inhibits pain signals. 3) The periaqueductal grey areas can also release opioids that act on the spinal cord. |
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What fissure or sulcus separates:
1) The cerebral hemispheres 2) The frontal and parietal lobes 3) The frontal and temporal lobes 4) The parietal and occipital lobes |
1) The medial longitudinal fissure
2) The central fissure 3) The lateral sulcus 4) The parieto-occipital sulcus |
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What are the three types of white matter fibers in the cerebrum?
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1) Association fibers: project within the ipsilateral cerebrum.
2) Commissural fibers: project between hemispheres between the corpus collosum and anterior commissure. 3) Projection fibers (e.g. internal capsule) that send fibers elsewhere outside of the telencephelon to the diencephalon, brainstem, cerebellum, and spinal cord. |
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What are the main functions of the caudate nucleus and putamen?
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Coordinate repetitive rhythmic movements like walking.
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What is the main function of the claustrum portion of the basal ganglia/cerebral nuclei?
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Identifies patterns and features of visual information at the subconscious level.
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What is the main function of the amygdaloid body?
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Regulates basic urges/emotion, such as hunger and sexual drive.
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What is the main function of globus pallidus?
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Maintains muscle tone before specific movements (hence its role in Parkinson's disease).
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Broadly speaking, what are the locations of the limbic system
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Between the border of the telencephalon and the diencephalon: cingulate gyrus, dentate gyrus, parahippocampal gyrus, hippocampus, amygdala, fornix, anterior thalamus, hypothalamus.
Also in the reticular formation. |
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Broadly speaking, what are the main functions of the limbic system.
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Coordination of emotions with appetites, aiding in the formation of memories, and bridging the gap between the voluntary and autonomic nervous systems.
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What are the main cortical areas of the limbic system in the cerebral cortex?
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The cingulate gyrus, the dentate gyrus, and the parahippocampal gyrus.
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What are the main nuclei of the limbic system in the cerebral cortex?
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The hippocampus and amygdala
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What is the main limbic tract in the telencephalon?
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The fornix
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What are the two main areas of the limbic system in the diencephalon?
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The anterior thalamus and the hypothalamus.
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Information from what cranial nerve does not pass through the thalamus?
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CN I (olfactory)
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What is the function of the lateral geniculate nucleus?
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Relay info from the optic tract to the occipital cortex.
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What is the function of the medial geniculate nucleus
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Relay info from the inferior colliculus to the auditory cortex (Brodmann areas 41 and 42 in the temporal lobe).
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What nuclei and cranial nerves exit out of the pons?
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V, VI, VII, VIII
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