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223 Cards in this Set
- Front
- Back
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Primordium of the Nervous System
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-Develops from infolding of ectoderm, forms neural tube
-3rd and 4th week after conception in humans -Neural crest is formed from a column of cells that pinch off along dorsal surface of neural tube --gives rise to DRG, sympathetic ganglia, schwann cells -Rostral end of the tube closes, forms cephalic limit of the future brain --lamina terminalis -Neural tube differentiates along its length as the embryo grows |
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Neural tube derivatives
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-DRG
-Sympathetic ganglia -Schwann Cells |
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Lamina Terminalis
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-Ventral extent of the cranial wall of 3rd ventricle
-Formed from rostral end of the neural tube |
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Ependymal cells
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-Line central canal of neural tube
-Divide and give rise to neuroblasts --neuroblasts and migrate away, differentiate into nuclei of nerve cells |
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Gray matter
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-concentrations of cell bodies
--nuclei and laminae |
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White matter
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-Concentrations of axons
--tracts --fasciculus --funiculus --column --commisure --bundle --root --nerve |
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Segmentation of the Neural Tube
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-Neural tube differentiates along length as embryo grows
-Ventricles arise from modifications of central canal --ventricles are lined with ependyma |
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Cerebral Aqueduct of Sylvius
Mesencephalic Aqueduct |
-Narrowing of the 4th ventricle, channel into the midbrain
-Above= Tectum -Below= Tegmentum |
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Tectum
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-Dorsal part of the midbrain (Mesencephalon)
-Divided into superior and inferior colliculi |
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Diencephalon
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-Forms walls of 3rd ventricle
-Composed of epithalamus, dorsal thalamus/thalamus proper, subthalamus, and hypothalamus |
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Epithalamus
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-Composed of pineal gland, stria medularis, habenular nucleus
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Lateral Ventricle
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-largest ventricle within cerebral hemispheres
-Forms anterior, posterior, and inferior horn -Connected to 3rd ventricle via interventricular foramen |
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interventricular foramen
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-Foramen of Monro
-Hole between lateral ventricles and 3rd ventricle -Allows movement of CSF between ventricles |
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Central Nervous System
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-Brain and Spinal Cord
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Peripheral nervous System
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-Cranial nerves
-Spinal nerves -Extensions of nerves |
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Dura mater
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-Pachymenix
-Thickest meningeal layer, most external -In vertebral canal is separate from periosteum by epidural space, filled with epidural fat -In braincase, dura is adhered to periosteum --adhered in C1 and C2, and to atlanto-occipital membranes |
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Atlanto-occipital membrane
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-Passes from the dorsal axis of the vertebral column to the dorsal rim of the foramen magnum of the occipital bone
-Great location for CSF tap into cisterna magna |
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Longitudinal Cerebral Fissure
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-Dorsal midline of the cerebrum, between two cerebral fissures
-Within fissure is falx cerebri of dura mater |
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Falx Cerebri
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-Invagination of dura mater between the two cerebral hemispheres, within the longitudinal cerebral fissure
-Layers of dura split and form dorsal saggital sinus |
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Leptomeninges
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-Pia mater and arachnoid layer
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Pia Mater
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-Thin, transparent internal membrane covering the brain and spinal cord
-Adheres to the external surface of nervous tissue |
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Arachnoid Layer
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-Between dura and pia mater layers
-Sends delicate trabeculae to the pia mater to hold it in place and hold blood vessels in place -In life, closer to the dura --in death, closed potential space opens due to lack fo CSF in subarachnoid space |
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Subarachnoid Space
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-Between arachnoid layer and pia mater
-Filled with CSF -Contains superficial blood vessels |
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Cisterna Magna
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-Cerebromedullary cistern
-Largest of the subarachnoid cisterns --In angle between the cerebellum and the medulla -Site for CSF puncture between atlanto-occipital space |
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Basilar Artery
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-Formed from the terminal branches of the vertebral arteries
-Continuous caudally with the ventral spinal artery of the spinal cord -Runs along the ventral midline of the medulla and pons -Divides into 2 branches, forms the caudal portion of the arterial circle/circle of willis |
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Internal carotid Arteries
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-Main source of blood to the arterial circle in the dog
-Enters middle cranial fossa, runs rostrally, and passes around hypophysis/Pituitary to reach optic chiasm -Runs dorsally, penetrates the dura and cavernous sinus -Divides into middle cerebral, rostral cerebral, and caudal communicating artery |
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Caudal Communicating arteries
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-Run caudally in circle of willis/arterial circle
-Join together to create the basilar artery |
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Cerebral Arterial Circle
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-Circle of Willis
-Surround the pituitary/Hypophysis -Gets blood from internal carotid artery and small branches from the arterial circle |
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Rostral Cerebral Artery
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-Terminal branch of the internal carotid artery at rostral aspect of the cerebral arterial circle
-Runs rostro-dorsally, lateral to optic chiasm -Runs dorsally between the two frontal lobes in longitudinal fissure -Runs caudally on the dorsal surface of the fibers that connect the two cerebral hemispheres -Supplies blood to the medial portion of the rostral half of the cerebrum |
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Middle cerebral artery
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-Arises from arterial circle near caudal aspect of the pituitary gland
-Rund laterally, rostral to the piriform lobe on ventral surface of the olfactory peduncle -Runs dorso-laterally aover the side of the cerebral hemisphere -Branches, supplies lateral surface of the entire cerebrum |
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Caudal cerebral artery
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-Arises from caudal communicating artery, near caudal aspect of the pituitary gland rostral to oculomotor nerve
-Follows optic tract, runs caudo-dorsally over laterals aspect of the thalamus to longitudinal fissure -passes rostrally on the dorsal surface of the corpus callosum, supplies medial part of the caudal half of the cerebral hemisphere -Supplies medial part of the caudal half of the cerebral hemisphere -Alos supplies diencephalon and rostral mesencephalon |
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Rostral cerebellar artery
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-From caudal 1/3 of arterial circle
-Runs dorso-caudally along the pons and middle cerebellar peduncle to lateral cerebellar hemisphere -Supplies caudal mid-brain and rostral half of the cerebellum |
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Caudal cerebellar artery
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-Branch of the basilar artery near middle of the medulla
-Runs dorsally, supplies caudal portion of the cerebellum |
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Brain cooling apparatus in the Dog
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--In alert, resting dogs, brain is warmer than arterial blood on common carotid artery
-During activity, brain temp drops even though carotid blood temp increases --stays 1.3 C below carotid temp during exercise -Counter-current heat exchange between warm arterial blood and cool venous blood draining nose and mouth --Arteries entering the brain run through cavernous sinus --Cavernous sinus gets cool venous blood from nasal cavity via opthalmic venous plexus -Protects brain from overheating suring severe thermal stress of exercise |
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Rete Mirabile
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-In ruminants
-Ventral to circle of willis-Internal, within the cavernous sinus -Carotid artery or branch from maxillary (depends on species) forms nest of tiny arterioles --arterioles exist in parallel --provide greater surface area for heat exchange -Venous blood from cavernous sinus cools arterioles in rete mirable -Arterioles converge into a single artery (internal carotid) and enter circle of willis |
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Venous Sinuses of the brain
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-Venous passageways within dura or bony canals of the skull
-Receive veins that drain the brain and bones of the skull -Blood is dilute due to addition of CSF -Bring blood and CSF back to maxillary, internal jugular, and vertebral veins, and vertebral venous plexuses |
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Dorsal Saggital Sinus
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-In attached edge of the falx cerebri, between two cerebral hemispheres
-Caudally, enters foramen for the doral saggital sinus in occipital bone --joins right and left transverse sinuses in skull |
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Species variations in arterial blood to the brain
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1. Dog, human: internal carotid artery and basilar artery supply arterial circle
-basilar artery carries blood to circle -No rete mirabile 2. Sheep, cat: only maxillary ramus supplies arterial circle -have rete mirabile -basilar artery carries blood away from circle 3. Ox: maxillary anastomosing ramus and vertebral artery supply arterial circle -have rete mirabile -Basilar artery carries blood away from arterial circle |
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Cavernous Sinus
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-On floor of the middle cranial fossa
-Extends from orbital fissure to the petro-occipital canal -Connected to the ophthalmic plexus and maxillary vein -Continued caudally by the ventral petrosal sinus, in petro-occipital canal -Intercavernous sinuses connect right and left cavernous sinuses, rostral and caudal to pituitary gland |
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Cerebro-Spinal Fluid
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-Flows within the ventricles and in subarachnoid space between arachnoid and pia layers of the meninges
-Reabsorbed from subarachnoid space along the major venous sinuses -Enters venous blood through arachnoid villi |
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Velum
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-Thin roof of the 4th ventricle
-In rhombencephalon |
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Rhombencephalon
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-Metencephalon and myelencephalon/hindbrain
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Choroid Plexus
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-Produces CSF
-In lateral ventricles, dorsal part of the 3rd ventricle, and in 4th ventricle |
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Nuclei
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-Discrete clusters of neurons
-Each nucleus has connections with a particular nucleus in the thalamus -Topical relationships between nuclei are often precise --Somatotopic/topographic organization |
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Somatotopic organization of the nervous system
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-Neurons innervating specific structures are located in a very specific location
-sensory innervation to one body area will connect with one specific part of medullary nucleus, innervation to another body area will connect to a different part of nucleus |
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Sensory Pathways
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-Brain receiving information from receptors in body
-touch, pressure, temperature, noxious stimuli -Stretch receptors, tension receptors, position receptors -Special senses (auditory, vestibular, visual, olfactory, gustatory) -Internal state of the body (blood pressure, lung stretch, bladder distention, blood glucose, blood O2, blood CO2, tension, GI stretch, chemoreceptors, baroreceptors |
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Special senses
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-Olfaction
-Vision -Taste/Gustatory -Hearing -Balance |
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Thalamo-Cortical Relations
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-Thalamus is an important staging area in transfer of information to cerebral cortex
--Almost all thalamic nuclei project into cortex --Almost all info arriving at cortex passes through a thalamic nucleus -Mostly relates to systems analyzing external world and responses to external world |
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Neocortex
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-Part of the cortex involved in analyzing and responding to the external world
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Cortico-subcortical projections
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1. Whole cortex projects to basal ganglia
2. Whole cortex projects into the diencephalon 3. Whole neocortex projects to the midbrain 4. Whole neocortex projects to cerebellum via cortico-ponto-cerebellar pathway --fibers end on pontine nuclei, pontine nuclei project to cerebellum 5. Cortical projections to the pons, medulla, and spinal cord are more defined than projections to higher levels |
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Middle cerebellar Peduncle
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-Huge bundle of fibers from pontine nuclei to cerebellum
-AKA brachium pontis |
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Cerebral Peduncles
Crus Cerebri |
-Joining of the fibers of the internal capsule
-Fibers in peduncles pass down toward medulla -Form pyramids when reach to the ventral surface of the medulla |
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Pyramids
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-Extensions of the cerebral peduncles on the ventral surface of the medulla
-Contain corticospinal and corticobulbar (corticomedullary) tracts -At junction of medulla and spinal cord, fibers cross/decussate and continue caudally in contralateral part of spinal cord |
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Brain divisions (general)
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1. Cerebrum (Telencephalon)
2. Cerebellum 3. Brainstem |
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5 Brain divisions
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1. Cerebrum (Telencephalon)
2. Diencephalon (epithalamus, thalamus, subthalamus, and hypothalamus) 3. Mesencephalon (midbrain) 4. Metencephalon (Pons and Cerebellum) 5. Myelencephalon (Medulla) |
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Brainstem composition
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1. Diencephalon (Epithalamus, thalamus, subthalamus, hypothalamus)
2. Mesencephalon (Midbrain) 3. Metencephalon (Pons and Cerebellum) 4. Mylencephalon (Medulla) |
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Gyri and Sulci
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-Gyri: outward folds on cerebrum
-Sulci: inward folds on cerebrum |
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Rhinal Fissure
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-Along lateral sides of the cerebellum
-Separates neocortex from paleocortex |
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Cruciate Sulcus
Ansate sulcus |
-transverse sulcus across the front part of cerebrum
-Separates frontal lobe from parietal lobe -Ansate Sulcus in the sheep --sheep does not have cruciate sulcus |
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Parietal Lobe
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-Behind the cruciate/Ansate sulcus and dorsal to ectosylvian sulcus
-Extends caudally to caudal 1/3 of cerebral hemisphere -Contains primary somatosensory cortex --Processing of somatosensory information |
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Occipital Lobe
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-Caudal 1/3 of cerebral hemisphere
-Primary visual cortex, primary receiving area for visual system |
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Frontal Lobe
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-Most rostral lobe of cerebrum, rostral to cruciate sulcus
-Production of motor commands |
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Temporal Lobe
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-Ventrolateral aspect of the cerebral hemispheres
-Primary receiving cortex for the auditory system |
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Paleocortex
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-Olfactory bulb, olfactory peduncle, piriform lobe
-Separated from neocortex by rhinal fissure |
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Piriform Lobe
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-Ventral bulge just lateral to pituitary gland and medial to the temporal lobe of the neocortex
-part of paleocortex -Separated from neocortex by rhinal fissure |
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Cerebellum
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-Modulates ongoing motor activity
--produces smooth, well-times, coordinated movements -Uses cerebellar connections to brainstem -Derived from dorsal part of metencephalon -Connected to brainstem by rostral, caudal, and middle cerebellar peduncles |
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Transverse cerebral fissure
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-Separates cerebellum from cerebrum
-Transverse sinus and tentorium cerebelli are within transverse cerebral fissure |
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Transverse fibers of the pons
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-On the ventral surface of the brainstem
-Run into cerebellum on each side -Form middle cerebellar peduncle -Run laterally and dorsally into the middle cerebellar peduncles -Pontine nuclei in ventral pons are source of fibers |
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Rostral cerebellar peduncle
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-Attaches rostrally
-Joins pons and cerebellum -Contains efferent axons from cerebellum to brainstem |
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Caudal cerebellar peduncle
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-Attaches caudally
-Joins pons and cerebellum |
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Vermis
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-Sagitally on cerebellar hemispheres, down the center
-Entire middle portion of the cerebellum -Directly above the 4th ventricle - |
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Paravermis
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-Sagitally oriented lobes on either side of the cerebellum
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Flocculo-nodular lobe of cerebellum
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-"wings" of cerebellum
-Not directly visible, kind of tuck under and are hidden from view |
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Folia
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-Gyri of cerebellum
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Medulla of the Cerebellum
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-White matter in the center
-Contains deep cerebellar nuclei -Connects with all folia and cerebellar peduncles |
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Boundary between telencephalon and hypothalamus
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-Optic chiasm
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Diencephalon
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-Thalamus, subthalamus, hypothalamus, and epithalamus
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Interthalamic adhesion
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-Joins two hemispheres of the thalamus
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Lamina Terminalis
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-Separation between rostral commisure and optic chiasm
-Rostral boundary of the 3rd ventricle -Most rostral extent of the embryonic neural tube on the median plane -Paper-thin |
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Infundibular recess
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-Extension of the 3rd ventricle into the infundibulum of the pituitary gland
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Hypothalamus
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-Forms the ventral portion of the diencephalon below the interthalamic adhesion
-Extends laterally from the lateral wall of the 3rd ventricle on each side out to internal capsule -Optic chiasm, infundibulum, and mammillary bodies are on ventral surface |
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Optic Tracts
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-Emerge from optic chiasm caudally
-Run laterally and dorsocaudally on lateral surface of the diencephalon -Enter lateral geniculate nucleus of the thalamus -Each tract curves around the caudal edge of the internal capsule |
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Mammillary bodies
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-On ventral surface of the hypothalamus
-Caudal edge = caudal extent of the hypothalamus and rostral boundary of the mid-brain |
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Thalamus
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-Extends laterally between midline epithalamus and internal capsule
-Optic tracts and lateral geniculate nucleus are on lateral edge -Below 3rd ventricle -Extends ventrally to top of the ventral component of 3rd ventricle |
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Epithalamus/Pineal Body
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-Major structure is Pineal Body
-Caudal projection from the diencephalon -Secretes melatonin (seasonal changes in reproductive activity) |
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Subthalamus
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-Not visible grossly
-Between thalamus and hypothalamus, near caudal end -Participates in neural circuitry with basal ganglia in telencephalon and substantia nigra |
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Mesencephalon
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-Midbrain
-Between caudal edge of the mammillary bodies (hypothalamus) and rostral aspect of the transverse fibers of the pons --Transverse fibers of pons cover part of ventral mesencephalon -Descending tracts from cerebral cortex form crus cerebri/cerebral peduncles |
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Crus cerebri
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-Cerebral peduncles
-Join cerebrum to mesencephalon/midbrain |
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Tectum
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-Mesencephalic structures dorsal to the mesencephalic aqueduct/aqueduct of sylvius
-Composed of corpora quadregemia --rostral colliculi and caudal colliculi -Receives sensory information about external world --Processes info to provide commands to drive somatic motor behavior |
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Rostral/Superior colliculi
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-Part of corpore quadregemia in tectum of mesencephalon
-Function in the visual system -Receives sensory information about the external world and processes info to drive somatic motor behavior -Superficial layers= visual info from retina -Deeper layers= somatosensory and auditory info -Translates visual info into oculomotor commands for visual tracking of stimuli -"balls" |
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Caudal/inferior Colliculi
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-Part of corpora quadregemia in tectum of mesencephalon
-Function in auditory system -Projection nucleus in the auditory pathway to medial geniculate nucleus and primary auditory cortex -Receives input from the ipsilateral lateral lemniscus --lateral lemniscus receives impulses from cochlear nuclei and superior olivary nuclei |
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Metencephaon
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-Pons and cerebellum
-Ventral surface of pons includes transverse fibers of the pons |
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Pontine Nuclei
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-In ventral pons
-Source of axons that make up the transverse fibers -Corticopontine fibers from all areas of cerebral cortex synapse on pontine nuclei -part of the pathway from the cerebral cortex to the cerebellum --corticopontocerebellar pathway |
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Myelencephalon
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-Medulla
-Extends from caudal aspect of transverse fibers of the pons to first dorsal and ventral rootlets of cervical nerve |
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trapezoid Body
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-Transverse band of fibers
-Runs parallel and caudal to the transverse pontine fibers -Associated with cochlear portion of VIII cranial nerve -Auditory function -Contains decussating auditory fibers |
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Pyramids
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-Pair of longitudinally running fiber bundles on either side of the ventral median plane on medulla
-Emerge from behind the transverse fibers of pons -Run caudally along trapezoid body, continue on ventral surface of the medulla -Right and left portions are separated by ventral median fissure -Axons continue in spinal cord as corticospinal tracts |
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Ventral median fissure
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-Separates right and left pyramids in medulla
-Stops at the decussation of the pyramids |
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Corticospinal tract
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-Continuation of the pyramidal axons within the spinal cord
-Descending tract, carries info from brain down to muscles -Decussates (crosses over) in the pyramids of medulla |
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Limbic System
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-Complex set of brain structures
-Lie on either side of the thalamus -Involved in emotion, behavior, motivation, long-term memory, Olfaction -Responsible for emotional life and long-term memories |
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Median Sulcus
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-Groove in the center of the floor of the 4th ventricle in the medulla
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Sulcus Limitans
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-Groove on the lateral wall of the medulla
-Longitudinal groove -Divides motor areas (medial and ventral) from sensory areas (lateral and dorsal) |
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Spinal Cord
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-Elongated, cylindrical structure
-Contained within the bony vertebral column -Most caudally positioned and least complex part of CNS |
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Spinal cord Functions
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1. Spinal reflexes:
--underlie basic somatomorot activity and visceromotor reflex activity 2. Channel for multiple ascending pathways --conduct sensory info from body soma and viscera to rostral parts of CNS 3. Channel for multiple descending pathways --Conduct info from cord that modulates spinal reflec activity |
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Central Canal
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-Center of spinal cord
-Filled with CSF |
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Epidural space
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-Between dura mater and bony vertebral column
-Contains irregular accumulations of adipose tissue -Can be used for injection of local anesthetic |
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Longitudinal laminae
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-Organization of neurons within the spinal cord
-Span a number of cord segments |
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Dorsalmedian Septum
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-Fibrous
-Extends deeply into spinal cord -Separates the dorsal half of the spinal cord into symmetrical halves |
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Dorsolateral Sulcus
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-Thin line on the lateral dorsal surface of the spinal cord
-lateral boundary of the dorsal funiculus -Point at which dorsal root fibers enter the spinal cord (afferents) |
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Ventromedial fissure
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-Narrow fissure on the midline of the ventral surface of the spinal cord
-Indents deeply into the ventral half of the spinal cord -Subdivides spinal cord into symmetrical halves-Identifies the ventral surface of the spinal cord |
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White matter
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-Composed of longitudinally-oriented myelinated and unmyelinated axons
-Axons ascend and descend -Formed by oligodendroglial cells in CNS -Formed by schwann cells in peripheral nervous system -Lipid content of myelin makes white matter white -Can be divide into dorsal funiculus, lateral funiculus, and ventral funiculus |
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Somatic Efferent
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-Axons of alpha motor neurons
-Axons of gamma motor neurons |
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Visceral Efferent
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-All sympathetic and parasympathetic fibers
--preganglionic and postganglionic |
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Somatic Afferent
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-All fibers from exteroceptors
--surface receptors for pain, touch, thermal receptors -Fibers from proprioceptors --position and movement |
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Visceral Afferent
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-Pain fibers
-Hunger fibers -Afferent fibers that are vital in reflexes |
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Alpha Motor neuron
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-AKA lower motor neuron
-Innervates voluntary skeletal muscle |
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Gamma motor neuron
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-Axons terminate on intrafusal cells in muscle spindles
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Preganglionic sympathetic neuron
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-Lies in intermediolateral column of spinal cord
--lateral horn -axon ends on postganglionic neurons |
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Gray matter
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-More heterogeneous than the white matter
-Composed of neurons, dendrites, myelinated and unmyelinated axons, local circuit axons, synaptic endings -Also contains glial cells -Can be divided into dorsal, intermediate gray, and ventral horns -Motorneurons, interneurons, and tract cells all exist in gray matter |
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Motorneurons
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-Large neurons
-Found within the ventral horn and intermediolateral cell column of lateral horn of gray matter -Upper lumbar cord and sacral cord -Project axons out of the spinal cord via ventral roots -Innervate striated skeletal muscle fibers, sympathetic ganglia, or parasympathetic terminal ganglia |
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Interneurons
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-In gray matter of spinal cord
-Involved in local circuit connections -interact with motorneurons, other interneurons, or tract cells |
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Tract cells
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-in gray matter of spinal cord
-Project axons rostrally or caudally for varying distances within the white matter |
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Propriospinal system
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-AKA spino-spinal system
-Interrelates different spinal cord segments -intrinsic connections of the spinal cord |
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Rexed's Laminae
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-Groupings of horizontally-oriented laminae within the spinal gray matter
-10 groupings total -Extend the length of the spinal cord -Lamina suggest physiological specificity within individual laminae -Dendrites of neurons within the different laminae possess different geometry and orientation -Laminae I-VI= dorsal horn --VII and X= intermediate gray --VIII and IX= ventral horn |
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Somatotopic Orgnization
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-Motorneurons in lamina IX are systematically positioned in different regions based on location of body and muscles innervated
-Distal muscles= dorsolateral region -Epaxial muscles= dorsomedial region -Allows motor neurons that innervate a given muscle or muscle group to organize into motorneuronal pools |
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Reciprocal innervation
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-Antagonistic muscle is kept from contracting during muscle contraction
-Collateral of the muscle spindle receptor activates inhibitory interneuron --interneuron inhibits alpha motor neurons that innervate antagonistic muscle |
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Spinal nerves
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-Form where dorsal and ventral roots come together
-Mixed nerves, contain both sensory and motor fibers |
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Dorsal Root
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-Contains only sensory fibers (afferents)
--Enter spinal cord -Made up of a series of rootlets |
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Dorsal Root Ganglion
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-contains thousands of sensory neuronal cell bodies
-Innervate corresponding body segment of spinal cord -Pseudounipolar cells |
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Ventral root
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-Contains only MOTOR fibers leaving the spinal cord (efferent)
-Made up of thousands of rootlets |
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Dorsal and ventral horns
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-Gray matter regions of the spinal cord
-Dorsal= sensory, receives central processes of sensory neurons -Ventral= motor mostly, contains alpha and gamma motor neurons --innervate skeletal muscles and muscle spindles |
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Intermediate gray
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-Region of interneurons and tract cells
-tract cell neurons give rise to long projecting axons, make up tract systems |
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lateral Horn
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-intermediolateral cell column
-Exists only in thoracic and upper lumbar segments -May not be grossly visible -Preganglionic motorneurons of the sympathetic division of ANS -In sacral segments, contains preganglionic motorneurons of parasympathetic division |
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Dorsal Column
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-Dorsal funiculus
-Contains fasiculus cuneatus and fasciculus gracilis -FC= forelimb related -FG= hindlimb related |
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Motor neuronal pools
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-Large neurons grouped into small clusters
-In ventral horn of the spinal cord -All alpha motorneurons that innervate a single muscle collect into a single motorneuron pool -Each motorneuron pool forms a column of alpha motorneurons --may extend 1-4 spinal cord segments |
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Hyperreflexia
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-Excessive reflex
-Due to damage to spinal cord segment above segment where reflex occurs -With time may subside |
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Crossed Extension Reflex
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-Alternating or reciprocal movements of the limbs
-Provide anatomical and physiological basis for stepping and running movements -Example of a polysynaptic reflex |
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Polysynaptic Reflexes
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1. Withdrawal reflex from noxious stimulus (flexion withdrawal reflex)
2. Crossed extension reflex |
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Golgi tendon organ
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-Proprioceptive sensory receptor organ
-At origins and insertions of skeletal muscles -Within tendons of skeletal muscles -Provides sensory component of golgi stretch relfex |
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Brainstem
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-Diencephalon, Midbrain, Pons, and Medulla
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Midbrain
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-Tectum (roof)
-Tegmentum (bottom) -Tectum and tegmentum are separated by dorsolateral fissure |
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Dorsolateral fissure
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-Separates tectum from tegmentum
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Tegmentum
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-Contains numerous sensory, motor, and autonomic nuclei
-Motor nuclei of Oculomotor (III), Trochlear (IV), abducens (VI), trigeminal (V), facial (VII), glossopharyngeal (IX), vagus (X), accessory (XI) and hypoglossal (XII) nerves -Direct rostral continuation of the medulla oblongata, excluding pyramids |
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Medulla Oblongata
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-Myelencephalon
-Cranial continuation of the spinal cord -Gray matter loses butterfly characteristic and moves towards external part instead of internal part -Enlarged relative to the spinal cord |
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Relay nuclei/Projection nuclei
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-Clusters of cell bodies
-Synapses between axons of ascending spinal cord tracts and cell bodies of neurons that project to the cerebrum, cerebellum, or thalamus -receive axonal input from ascending sensory systems from spinal cord and primary sensory systems of the head -Ultimate destination is cerebellum or cerebral cortex -Gracile and cuneate nuclei -lateral cuneate -inferior olivary -lateral reticular nuclei |
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Reticular Formation
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-Extends from caudal medulla into upper midbrain
-Some nuclei are diffuse and impossible to isolate, others are obvious and easy to isolate -Can be divided into medial and lateral portion -Neuron axons can extend from spinal cord to thalamus and hypothalamus --ideal for influencing the activity level of the nervous system as a whole -involved in regulation of respiration, vasomotor activity, gastric function -Spontaneous respiration is completely dependint on medullary reticular formation |
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Raphe Nuclei
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-Along the midline of the medulla
-Continuous sheet of cells taht extends along the midline of brainstem from caudal medulla to rostral mesencephalon -Major projections are to hypothalamus, amygdyla, caudate/putamen, septum, hippocampus, thalamus, periaqueductal gray, cerebral cortex -Mostly serotonin cells |
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Nucleus Raphe Magnus
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-In medullary gray matter
-Source of axons that descend to dorsal horn of the spinal cord -Role in modulating pain input |
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Gigantocellular reticular nucleus
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-In medullary gray matter
-Source of reticulospinal fibers -Modulates activity of the ventral horn spinal motorneurons |
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Reticulospinal tracts
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-From reticular formation
-In charge of muscle tone |
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Medullary reticular formation
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-Completely responsible for spontaneous respiration
-Also plays a role in cardiac and vasomotor networks --excite or inhibit the heart |
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Pontine reticular Formation
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-initiates REM sleep
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Reticular Activating system
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-Ascending projections of reticular nuclei to thalamus
-Has huge effect on thalamocortical activity -Lies in medial thalamus -Gets input fomr major sensory systems -Tunes levels of excitability of cells in the cerebral cortex, basal ganglia, and other forebrain structures -Helps maintain consciousness -provides means for arousal to initiate action |
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Fiber tracts in the Medulla
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1. Fibers originating in projection neurons of spinal cord and in projection nuclei of medulla
--Ascend to cerebellum, midbrain tectum, thalamus, and cerebral cortex --Medial and lateral lemnisci, spinocerebellar, cuneoberebellar, neospinalthalamic tracts 2. Descending tracts 3. Fiber tracts associated with cranial nerves |
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Vestibulospinal tract
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-Divided into lateral and medial divisions
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Lateral vestibulospinal tract
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-Fibers originate in lateral vestibular nucleus
-In ventral funiculus of the spinal cord -Contains only uncrossed axons -End directly on the extensor motorneurons and spinal interneurons |
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Medial vestibulospinal tract
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-Originates in medial vestibular nucleus
-Fibers reach spinal cord through descending component of medial longitudinal fasciculus -Each nucleus projects bilaterally -Fibers travel in the ventral funiculus, terminate in the medial part of the ventral horn |
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Reticulospinal Tracts
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-2 sites of origin
--pons and medulla -Medullary fibers lie laterally and travel bilaterally in lateral funiculus of the spinal cord -Pontine fibers lie medially, are uncrossed, descend in ventral funiculus of spinal cord -Axons terminate on interneurons of the ventral horn |
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4 Sensory modalities entering caudal brainstem
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1. somatosensory: somatic afferents
--V, VII, IX, and X 2. Visceral afferents: --IX, X 3. Taste: --VII, IX, X(taste) --VIII (auditory) 4. Vestibular: --VIII Corresponding groups of sensory nuclei are associated with modalities/cranial nerves |
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Circumventricular organs
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-Border the ventricular surface
-Lie on or close to midline of the brain -Lack blood brain barrier in capillary bed -Contain central receptor sites in brain for circulating hormones? -Singnal brain about internal state of the body |
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Area Postrema
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-In caudal medulla along the walls of the 4th ventricle
-Extensive projections into nucleus of the solitary tract, nucleus ambiguus, and parabrachial nucleus -receives a prominent descending projection from hypothalamus -Can modulate incoming visceral affernt information -Modulates BP by detecting angiotensin II in blood circulation -Detects toxic factors |
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Monoamine systems
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-Collections of cell bodies and axonal projections
-Utilize special NT substances derived from tyrosine or tryptophan --Dopamine, norepi, epi, and serotonin -Goal-oriented behaviors (feeding, sex, drinking) -Memory and learning -Arousal and motivation -Mood |
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Locus Coeruleus
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-In dorsal pons
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Vagal area
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-Along caudal walls of 4th ventricle
-greyish buldge -Contains nucleus of the solitary tract and dorsal motor nucleus of the vagus nerve |
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Nucleus of the solitary tract
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-Termination of visceral afferents
-In vagal area |
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Dorsal motor nucleus of the vagal nerve
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-Origin of visceral efferents
-In vagal area -Associated with vagal nerve |
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Vestibular area
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-Slight bulge along dorsal wall of the 4th ventricle
-rostral to vagal complex and caudal/medial to cerebellar peduncles -Contains 4 vestibular nuclei --receive afferents from vestibular apparatus |
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Tuberculum Cinereum
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-Longitudinally-running column on dorsal surface of the medulla
-Most lateral and on side of the medulla -Carries axons from the spinal trigeminal tract (STT) on top of spinal trigeminal tract nucleus (STN) --Tract is an extension of the dorsal root --Nucleus is like a dorsal horn for the face/head -Axons enter brain in the trigeminal nerve |
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Nucleus of the Solitary Tract
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-Receives visceral sensory neurons
-Receives taste via facial (VII), glossopharyngeal (IX), and vagus (X) --to rostral portion -Receives visceral afferents via glossopharyngeal (IX) and vagus (X) --to middle and caudal portion |
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Tractus Solitarius
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-Solitary Tract
-Fiber tract for visceral sensory neurons -Taste via facial (VII), glossopharyngeal (IX), and vagus (X) -Visceral afferents via glossopharyngeal (IX) and vagus (X) |
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Nucleus Ambiguus
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-Glossopharyngeal (IX) and Vagus (X)
-Motorneurons that innervate branchial arch origin -Glossopharyngeal nerve (IX) innervates stylopharyngeus and other pharyngeal muscles -Vagus (X) innervates pharyngeal muscles, laryngeal muscles, and esophageal striated muscle |
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Spinal Trigeminal Nucleus and Tract
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-Somatic Sensory innervation to the head and face
-Taste and viasceral afferents -Associated with Facial (VII), glossophatyngeal (IX), and vagus (X) nerves |
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Main Sensory Nucleus
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-Trigeminal
-Origin of trigeminothalamic tract |
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Motor nucleus of the Trigeminal nerve
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-Motor neurons that innervate the muscles of mastication
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Cochlear Nucleus
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-Involved in hearing
-Vestibulocochlear (VIII) |
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Facial Nucleus
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-Motor innervation to the muscles of facial expression
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Abducens Nucleus
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-Motorneurons of the abducens (VI) nerve
-Lateral rectus and retractor bulbi muscles |
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Nucleus Gracilis
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-Projection nucleus of the dorsal column medial lemniscal pathways
-Somatosensory pathway from the caudal half of the body -Conscious proprioception |
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Nucleus Cuneatus
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-Projection nucleus of the dorsal column medial lemniscal pathway
-Somatosensory pathway from rostral half of the body --Except hearing -Conscious proprioception |
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Inferior Olive
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-Projection nucleus
-Receives input from all sensory systems -Points to cerebellum as climbing fibers |
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Lateral reticular Nucleus
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-Projection nucleus
-Receives sensory inputs from spinal cord -projects to cerebellum as mossy fibers |
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Accessory Cuneate Nucleus
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-projection nucleus
-Receives sensory input from cervical and upper thoracic spinal cord segments -Projects to the cerebellum as mossy fibers -Unconscious proprioception |
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Caudal cerebellar Peduncle
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-Projection path for dorsal spinocerebellar and cuneocerebellar pathways
-Sensory information |
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Superior Olivary nuclear complex
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-Projection pathway
-involved in auditory system |
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Middle cerebellar peduncle
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-Projection path
-Connects pontine nuclei axons to the cerebellum -motor coordination |
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Rostral cerebellar peduncle
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-Projection pathway
-Ventral spinocerebellar projection -Sensory |
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Lesions of the Medulla
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-Signs are representative of the motor and sensory pathways passing through medulla
1. facial hypalgesia or analgesia (sensory trigeminal V) 2. Paresis or paralysis of masticatory muscles (Motor trigeminal V) 3. Medial Strabismus (abducens VI) 4. Facial paresis or paralysis (Facial VII) 5. Pharyngeal Paresis ( Glossopharyngeal IX, Vagus X) 6. Tongue Paresis (Hypoglossal XII) |
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Olfactory I
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-Sensory
-Smell |
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Optic II
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-Sensory
-Vision |
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Oculomotor III
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-Motor
-Eye movements -Innervates dorsal, medial, ventral rectus, levator palpebrae muscles -Mediates pupillary constriction and accomodation of the lens for near vision |
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Trochlear IV
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-Motor
-Innervates dorsal oblique muscle |
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Trigeminal V
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-Mixed
-Mediates cutaneous and proprioceptive sensations from skin, muscles, and joints in the face and mouth -Sensory innervation to teeth and corneal reflex -Motor innervation to muscles of mastication |
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Abducens IV
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-Motor
-Innervates lateral rectus and retractor bulbi muscles |
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Facial VII
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-Mixed
-Innervates muscles of facial expression, muscles for closing the eye and motor corneal reflex -Innervates lacrimal glands and salivary glands -Mediates taste sensation from the caudal 2/3 of tongue -Sensation from the skin of the external ear |
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Vestibulocochlear VIII
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-Sensory
-hearing, balance, postural reflexes -Orientation of the head in space |
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Vagus X
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-Mixed
-Autonomic fibers innervate smooth muscle in the heart, blood vessels, trachea, bronchi, esophagus, stomach, and intestine -Innervates striated muscles in the larynx and pharynx, controlling speech -Mediates visceral sensation from the pharynx, larynx, thorax, and abdomen -Innervates taste buds in the epiglottis |
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Spinal Accessory XI
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-Motor
-Motor innervation of the trapezius and sternomastoideus muscles |
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Hypoglossal XII
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-Motor
-Innervation to the intrinsic muscles of the tongue |
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Basis Pontis
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-Ventral region of the pons
-Contains longitudinally directed fiber bundles --Caudal continuations of the crus cerebri/cerebellar peduncle of midbrain |
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Fibers of the Basis Pontis
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-Corticopontine fibers
-Corticobulbar fibers -Corticospinal fibers Fibers become separated and somewhat dispersed as they enter the rostral border of the basilar pons --dispersal is caused by the presence of interspersed clusters of cell bodies of pontine nuclei |
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Corticopontine fibers
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-From cerebral cortex to pontine nuclei
-part of the basis pontis -Fibers from all areas synapse on the pontine nuclei |
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Corticobulbar fibers
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-From cortex to nuclei in the medulla
-part of the basis pontis |
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Corticospinal fibers
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-From cortex to interneurons and motor neurons in the spinal cord gray matter
-Part f basis pontis |
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Pontocerebellar fibers
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-Provide information to the cerebellum
--motor commands from the primary motor cortex --Sensory information from the primary receiving areas |
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Main sensory nucleus
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-Component of the brainstem trigeminal nuclear complex
-Runs into the pons and rostral medulla -Receives sensory info from the face, sinuses, oral cavity, and head -Projects axons via the medial lemniscus to the thalamus |
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Motor nucleus of the trigeminal nerve
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-Just medial to the main sensory nucleus
-provides motor innervation to the muscles of mastication and tensor tympani, tensor palati, mylohyoid, and rostral belly of the digastricus muscle |
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Facial nerve nucleus
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-Dorsolateral to the superior olivary nuclei
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Superior Olivary Nuclei
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-Auditory pathway structure in the pons
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Auditory pathways in the Pons
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-Superior Olivary Nuclei
-Trapezoid body -Nuclei of the trapezoid body -lateral lemniscus -Nuclei of the lateral lemniscus |
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Fibers extending throughout the length of the pons
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-Medial lemniscus
-medial longitudinal fasciculus |
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Midbrain
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-Mesencephalon
-Just rostral to the rostral border of the pons -Smallest of the 5 brain divisions -Composed of tectum and tegmentum |
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Substantia Nigra
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-In midbrain/mesencephalon
-Dopamine projections arise from substantia nigra -Dopamine neurons of the nigrostriatal tract -Important for locomotion -Damage in the area causes parkinsons |
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Serotonergic Pathways
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-Arise from raphe nuclei in midbrain, pons, and medulla
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Extrapyramidal motor system
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-Substantia nigra
-Nucleus Ruber (red nucleus) -Reticular formation -Functional grouping of neurons in the midbrain -Contributes to the control of striated muscle tone |
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Retinotectal fibers
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-Leave optic tract rostral to the dorsal lateral geniculate body
-Project to superior colliculus via brachium of the superior colliculus -Bilateral in origin |
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Corticotectal fibers
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-From visual cortex
-Terminate in rostral 1/3 of rostral colliculus -Unilateral |
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Rostral Colliculus Outputs
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1. to cranial nerve nuclei to control movement of the eyes
--Oculomotor III, trochlear IV, abducens VI 2. Projection down brainstem and spinal cord to cervical cord segments (tectospinal tract --Produces head movements via neck muscles 3. Tectopontine tract to pontine nuclei --Relays visual input to the cerebellum |
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Tectoreticular projection
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-Innervates the mesencephalic reticular formation bilaterally
-projects to the pontine and medullary reticular nuclei near midline -Control of visual attention (gaze) |
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Pupillary reflexes
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-Mediated by the pretectal region
-Directly controlled by the edinger-westphal nucleus -Shining light into one eye should constrict BOTH eyes --consensual response -Light levels detected by the retina are projected via optic nerves and optic tracts to pretectal nuclei --pretectal neurons project to Edinger-Westphal nucleus --Edinger-Westphal neurons are parasympathetic pregangionics to ciliary body behind eye |
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Pretectal region
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-Just rostral to the superior colliculus
-Mediates pupillary reflexes |
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Edinger-Westphal nucleus
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-Directly controls the pupillary light reflex
-Subnucleus of the oculomotor nerves -Neurons are parasympathetic preganglionics to the ciliary body behind the eye |
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Dopaminergic Pathway
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-Chemically-defined pathway
-Has cell bodies in substantia nigra, ventral tegmental area, and retrorubral nucleus |
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Serotonergic Pathway
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-Cells mostly found in raphe nuclei
-Neurons can contain more than one NT --adds plasticity to the system -System can modulate sensory info at spinal cord, at thalamic relay, at cerebral cortex |
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Pontine Tegmentum
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-Area above the basilar pons
-Includes reticular formation, cranial nerve nuclei and projection nuclei above the basilar pons |
