Structure and Function Midterm 1
Structure and Function Midterm 1 Neuro 3050
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NEUROSC 3000 - 020
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This 11 page Study Guide was uploaded by alvey.15 Notetaker on Friday January 29, 2016. The Study Guide belongs to Neuro 3050 at Ohio State University taught by Georgia Bishop in Spring 2016. Since its upload, it has received 354 views. For similar materials see Structure and Function of the Nervous System in Neuroscience at Ohio State University.
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Structure and Function Midterm 1 Study Guide Brain and Spinal cord 1) The CNS 2) Different distinctions of rostral, caudal, dorsal and ventral past the diencephalic flexure. 3) Nuclei are groups of neurons within the CNS. Plural- Nucleus 4) Tract- axonal pathway connecting two regions of the CNS 5) Fasciculus- a collection of independent fibers that serve a common function. Fasciculus=Tract 6) Funiculus- A collection of axonal tracts or fasciculi. More axons are FUN!! Peripheral Nervous System 1) Neurons, dendrites, and axons outside the the brain and spinal cord 2) A ganglion is a group of neurons in the PNS. Example) dorsal root ganglion which is a collection of sensory neurons outside the spinal cord. Brain 1) Dorsal (Superior) – Moving towards the parietal lobe. Imagine a dolphin’s dorsal fin on the top of your head. 2) Ventral (Inferior)- Latin for “belly”. The belly of your brain! Moving towards the temporal lobe and brain stem. 3) Rostral- Latin for “nose”. Moving towards the nose and frontal lobes. 4) Caudal- Latin for “tail”. Moving towards the occipital lobe. Spinal Cord 1) Dorsal (superior) - Moving towards the back. Imagine a dolphin’s fin on your back. 2) Ventral (inferior) – Moving towards the belly. 3) Rostral- Moving towards the brain. R for rising towards the brain. 4) Caudal- Moving towards the feet. C for climbing down towards the feet. Views of the Brain 1) Sagittal cut- Looking at the brain from a side view. Midsagittal cut is splitting the brain in to it’s two hemispheres. Some key structures you should be able to see are the cerebellum, the pons, and the corpus callosum. 2) Coronal cut- Looking at the brain the same way you look at a person’s face. The face and skull are just removed now (sorry for the gory description!) You should be able to see the lateral ventricles and third ventricle pretty clearly. 3) Horizontal (Transverse) cut- Looking at the brain from a bird’s eye view and cutting horizontally from top to bottom. The corpus callosum is intact and is very visible running bilaterally through the middle of the brain. Meninges 1) Dura mater is Latin for “hard mother” and is made of dense connective tissue. It is the first meningeal layer under the skull. Provides additional hard protection for the brain. 2) Arachnoid layer is smooth where it attaches to dura mater and there is a layer of meshwork (arachnoid trabeculae) that continues down to connect to the pia mater. Between the smooth layer and layer that connects with the pia is called the subarachnoid space and is filled with CSF. 3) Pia mater is Latin for “soft mother” and it is a thin layer that contours the brain. It is not very distinguishable because it is so closely attached to the brain. 4) The dura mater, arachnoid, and pia mater also wrap around the spinal cord. Vertebra Anatomy 1) Spinous process- Medial of the bilateral transverse processes. The spinous process faces dorsal from the spinal. If you forget just feel the bumps on your back because those are the spinous processes of your vertebrae. 2) Lamina- The bridge of bone that holds the two transverse processes and the spinous process together. A laminectomy is when bilateral incisions are made proximal to the transverse processes so the dorsal part of the vertebra can be taken off. This procedure is done to gain access to the spinal cord. 3) Vertebrae are stacked on top of each other and between every two vertebrae is the intervertebral foramen. The spinal nerves emerge from the intervertebral foramen and extend to periphery. Specializations of the Pia 1) Filum Terminalae- The spinal cord stops growing around L2 (conus medullaris) but the pia layer around the spinal cord continues to grow. The filum terminalae fuses with the arachnoid and dura mater at the coccygeal ligament around S2. The area between L3 and S2 is called the lumbar cistern and this is where it is safe to get a lumbar puncture because the needle won’t hit the spinal cord. 2) Denticulate ligament- This is the only visible region of the pia mater of the spinal cord but the meninges have to be cut open and pulled back from the cord to see it. The denticulate ligament extends all the way to the dura mater. The function of the denticulate ligament is suspension of the spinal cord. Anatomy of the Spinal Cord 1) Conus Medullaris- The end of the spinal cord at L2-L3 2) Filum terminalae- extension of the pia past L2 once the spinal cord stops growing. The filum terminale combines with the dura mater and arachnoid at the coccygeal ligament at S2. 3) Cauda Equina- Latin for “horses tail”. It is the accumulation of motor and sensory axons extending past the spinal cord to exit the correct intervertebral foramen. 4) Cross section of spinal cord A) Gray Matter-the butterfly shaped region in the middle contains neurons. These neurons can be stained with a Nissl stain. White Matter- the region around the butterfly contains axon tracts and can be seen better with a silver stain. B) Dorsal brainstem contains two dorsal horns of gray matter and two dorsal columns of white matter. The dorsal side of the brainstem is where sensory information enters via afferent axons. C) Ventral brainstem contains two ventral horns of gray matter and two ventral columns of white matter. The ventral side of the brainstem is where motor information leaves the spinal cord via efferent axons. D) There are also two lateral gray horns and two lateral white matter columns that are responsible for autonomic responses. E) The lateral, dorsal and ventral white matter columns are funiculi. F) Anterior Median Fissure- a distinguishing deep sulcus in the middle of the ventral side of the brain stem. Median means “in the middle”. G) Posterior Median Sulcus- a sulcus not as deep as the anterior median fissure. It is located in the middle on the dorsal side of the spinal cord. 5) The primary cell bodies for the afferent axons are located in the dorsal root ganglion in the periphery. The dorsal root ganglion receives sensory information from the periphery and relay that information to the spinal cord. The primary cell bodies for efferent axons are in the ventral horn of the spinal cord. The ventral horn translates the sensory information in to motor information and sends it out to the periphery from the spinal cord. Anatomy and Functional Components of a Nerve 1) A nerve is composed of many axons. Some of the axons are from sensory neurons and some are from motor neurons. Motor neurons originate in the CNS and sensory neurons originate in the PNS. 2) Axons in a nerve are not homogenous. Some are myelinated while others are not and some have a large diameter while others have a small diameter. 3) Layers of Nerve A) Endoneurium- endo means “inside”. The innermost layer of connective tissue that surrounds each myelinated axon in nerve. B) Perineurium- peri means “around”. The middle layer of connective tissue around a bundle of myelinated axons C) Epineurium- epi means “above”. The layer of connective tissue above the rest that encompasses the entire nerve. 4) Efferent axons carry motor information from the CNS to the PNS. E for exiting the CNS. The neuron somas are in the ventral horn. 5) Afferent axons carry sensory information from the PNS to the CNS. The neuron somas are in the dorsal root ganglion. Spinal Efferent Axon Function 1) General Somatic Efferent (GSE)- Part of the somatic nervous system that we have voluntary control over. The neuron somas originate in the ventral horn and carry general motor information to skeletal muscles in the periphery. 2) General Visceral Efferent (GVE)- Part of the autonomic nervous system that we do not have voluntary control over. The neuron somas still originate in the ventral horn but before reaching its destination the axons synapses on autonomic ganglion. The autonomic ganglion then synapses on smooth muscle, cardiac muscle or glands. A) The somas in the ventral horn are called preganglionic neurons and the somas in the PNS ganglion are called the postganglionic neurons. The preganglionic neurons are always located in the CNS and the postganglionic neurons are always located in the PNS. Spinal Afferent Axon Function 1) General Somatic Afferent (GSA)- Neural bodies that originate in the dorsal root ganglion carry general sensory information (touch, pain and pressure) to the dorsal spinal cord. 2) General Visceral Afferent (GVA)- Neural bodies that originate in the dorsal root ganglion carry autonomic sensory information to the dorsal spinal cord. A) Referred pain- Viscera have few sensory afferents covering a large area and they enter the spinal cord where axons from nearby structures enter the spinal cord. Due to the anatomy pain and pressure signals coming from the viscera are usually felt in a nearby somatic structures. For example, when someone is having a heart attack they usually feel the pain in their left arm and neck. Important Distinctions between Cranial Nerves and Spinal Nerves 1) All spinal nerves have a sensory and motor component. Not all cranial nerves have a sensory and motor component. 2) Spinal nerves originate from dorsal and ventral roots. The sensory and motor information in a cranial nerve is combined in the brainstem or the brain. Dorsal and ventral roots end at area C1 of the vertebral column. Functional Components of Cranial Nerve Axons 1) GSA, GVA, GSE and GVE of the cranial nerves have all of the same functions as in a spinal axon but they are associated with different areas. A) GSA- sensory information from the somatic areas of the mouth, ear, and face. B) GVA- sensory information from the viscera (internal organs). C) GSE- motor information to the somatic areas of the face (eyes, mouth, and face). D) GVE- motor information to the viscera, glands of the head, and muscles of the eye. 2) Special Somatic Afferent (SSA) and Special Visceral Efferent (SVE) are functions only in cranial nerves A) SSA- carries somatic sensory information that is specialized to the head to the spinal cord. Involved the senses in our head: Olfaction, Vision, Gustation and Audition. B) SVE- Even though this has visceral in the name the axons are still under voluntary muscle control. The functions that the axons are involved in (breathing, talking and swallowing) have a visceral component. These axons have a unique embryological origin and innervate the brachiomeric muscles that control facial movements, tongue movements, swallowing and speaking. Autonomic Nervous System 1) We do not have conscious control over the afferents and efferents of this system. 2) Innervate glands, smooth muscle and cardiac muscle of the body and head. 3) Parasympathetic and Sympathetic nervous system divisions work together and are always active. One system may override the other by antagonized the neurons associated with that system 4) Activation of the parasympathetic and sympathetic nervous systems is event specific. For example, your parasympathetic nervous system might be slowing down your heart rate, constricting your pupils and lowering your blood pressure on a hot day outside. Once you step inside a cold building you sympathetic nervous system might antagonize your parasympathetic nervous system and you develop goose bumps. If you are sitting down in a cold building to study, then your parasympathetic nervous system and sympathetic nervous system might be acting together. Remember: one system is not active but is working with the other depending on the event at hand. 5) A difference in the efferent pathway of axons in the ANS from the efferent pathway of the somatic nervous system is that the ANS efferent pathway synapses on two groups of neurons before reaching its final destination. The somatic nervous system only synapses on the neurons in the ventral horn before reaching its final destination. The two groups of neurons in the ANS efferent pathway have special names. A) Preganglionic neurons- neurons in the ventral horn of the spinal cord B) Postganglionic neurons- neurons in the PNS. This is not the dorsal root ganglion because if is a efferent pathway carrying motor information not an afferent pathway carrying sensory information. 6) The parasympathetic nervous system generally releases acetylcholine from the preganglionic neurons and postganglionic neurons 7) The sympathetic nervous system generally releases acetylcholine from the preganglionic neurons and norepinephrine from the postganglionic neurons. Sympathetic Nervous System and Sympathetic Ganglion 1) Rules about all Sympathetic Ganglion A) The preganglionic neurons originate and exit from the ventral root in the thoracolumbar (thoracic and lumbar) region in the vertebral column. B) All preganglionic processes enter the sympathetic chain 2) The Sympathetic Chain extends bilaterally proximal to the vertebral column and extends from C1 to the sacral level of the spinal cord. A) The paravertebral ganglia (para is Latin for “beside”) of the sympathetic chain is innervated by preganglionic neurons from levels T1 to L2 B) The postganglionic neurons near the sympathetic chain are innervated by using rami communicante to send the signal to proximal spinal nerves. C) Preganglionic neurons in ventral root > paravertebral ganglia in sympathetic chain > rami communicante > postganglionic neurons in the peripheral spinal nerves D) Some postganglionic neurons are located in the collateral ganglia on the posterior wall of the abdomen. E) Preganglionic neurons in the ventral root > paravertebral ganglia in the sympathetic chain > postganglionic neurons in the collateral ganglia on the posterior wall of the abdomen. Parasympathetic Preganglionic Neurons 1) Parasympathetic preganglionic neurons originate in the craniosacral region so nuclei in the brainstem and the ventral root in the sacral region. 2) Parasympathetic postganglionic neurons innervate the target organs or near the target organs as in the case of cranial nerves III, VII, IX, X. Cranial Nerves 1) Mnemonic device to remember the numbers and names of cranial nerves A) Oh, Oh, Oh Time To Act Freely Vivian Go Visit A Hedgehog B) Olfactory (I), Optic (II), Oculomotor (III), Trochlear (IV), Trigeminal (V), Abducens (VI), Facial (VII), Vestibulocochlear (VIII), Glossopharyngeal (IX), Vagus (X), Accessory (XI), Hypoglossal (XII) Olfactory (I) 1) Special Sensory Afferent 2) Sensory neurons are located in the olfactory epithelium of the nasal cavity. The olfactory bulbs contain the CNS neurons that decode smell information. Optic (II) 1) Special Sensory Afferent 2) Sensory neurons in the retinal ganglion layer. Oculomotor (III) 1) Visceral Motor Efferent and Somatic Motor Efferent 2) Somatic motor efferent innervates the medial rectus. Medial means “towards the nasal side of the eyeball” and rectus means “straight”. This muscle allows you to cross your eyes. 3) Postganglionic parasympathetic efferents innervate ciliary ganglion that innervate the pupil (constriction) and lens (accommodation). Trochlear (IV) 1) Somatic Motor Efferent 2) Only cranial nerve that has contralateral projections and is on the dorsal side of the brain stem. Moves the eye by the superior oblique. 3) Smallest cranial nerve Trigeminal (V) 1) General Sensory Afferent and Brachiomotor Efferent (Special Visceral Efferent) 2) Largest cranial nerve and sits bilaterally to the pons 3) Split in to three regions of the face called V1, V2 and V3 4) V1 innervates the area above the zygomatic arch (under eye bone) including the eye. V2 innervates the maxillary arch (upper jaw), upper teeth, and nasal cavity. V1 and V2 are General Sensory Afferents. 5) V3 innervates the mandibular arch (lower jaw), lower teeth, chin and anterior part of the tongue. V3 has a brachiomotor efferent involved in chewing and mastication. The general sensory afferent is involved with general pain and sensation from the jaw and tongue. 6) V1, V2 and V3 come together at the trigeminal ganglion behind the temporal bone of the skull but does not synapse on neurons within the ganglion. In this sense it is similar to the dorsal root ganglion of the spinal cord. Abducens (VI) 1) Somatic Motor Efferent 2) Innervates the lateral rectus which moves the eye from side to side Facial (VII) 1) Super 7 Nerve: Has all the cranial nerve components except for Somatic Motor Efferent 2) All the cranial components travel from the brains stem through the middle ear or near the middle ear and to their respective areas of the face. 3) The VME travels from the brainstem, through the middle ear and innervates the lacrimal gland (tearing response) and salivary gland. 4) The SSA innervates taste buds on the anterior part of the tongue. 5) The GSA innervates the skin behind the ear 6) The BME innervates the facial muscles. 7) In both the SSA and GSA the cell bodies originate in the geniculate nucleus 8) The SSA has parasympathetic postganglionic neurons in the submandibular gland and the preganglionic neurons are in the geniculate ganglion. The is the first afferent axon that has had a preganglionic neuron and postganglionic neuron. Vestibulocochlear (VIII) 1) Special Sensory Afferent 2) Neuron bodies originate from the cochlear ganglion and vestibular ganglion Glossopharyngeal (IX) 1) Super 9 Nerve: Has all the components except for the Somatic Motor Efferent 2) Gloss means “tongue” and pharyn means “pharynx” 3) BME innervates the stylopharyngeal muscle to initiate swallowing and cell bodies originate in the jugular foramen in the superior and inferior ganglia. 4) GSA initiates the gag reflex and cell bodies originate in the pharynx. 5) SSA initiates taste on the posterior area of the tongue. Cell bodies originate in the posterior are of the tongue. 6) SVA innervate the carotid sinus and carotid body which measures carbon dioxide levels and blood pressure. Cell bodies originate in the carotid sinus and carotid body. 7) SVE has postganglionic neurons in the otic ganglion which projects to the parotid gland. The preganglionic neurons are in the jugular foramen. 8) All efferent and afferent axons have connections to the superior and inferior ganglion in the jugular foramen of the CNS. Vagus (X) 1) Super 10 nerve: Has all components except for the Somatic Motor Efferent 2) This is the only cranial nerve that extends past the head and neck to the thorax using the Visceral Motor Efferent. The parasympathetic preganglionic neurons originate in the jugular foramen and synapse on the organs of the thorax stopping at the colon. 3) Brachiomeric efferents synapse the pharynx constrictors and is the motor component of the gag reflex. 4) SSA cell bodies originate in the epiglottis where some taste buds are located 5) GSA cell bodies originate in the external auditory meatus and larynx for hearing a speaking 6) All efferent and afferent axons have connections to the superior and inferior ganglion in the jugular foramen of the CNS. Accessory (XI) 1) Brachiomotor Efferent (SVE) to the neck muscles called the trapezius and sternocleidomastoid. Hypoglossal (XII) 1) General Motor Efferent to extrinsic and intrinsic muscles of the tongue that move the tongue. Gross Anatomy of the Spinal Cord Ventral Medulla 1) The medulla is continuous with the brain stem externally and a distinguishing feature on the medulla is the anterior median fissure that runs all the way down the spinal cord 2) Bilateral to the anterior median fissure are the medullary pyramids which are large, raised and oblong shaped. 3) Where the anterior median fissure looks smudged out near the middle of the medulla is the pyramidal decussation which is where the tracts from the right and left areas of the brain cross. 4) The olivary eminences lie lateral to the pyramids. Both olivary eminences have a preolivary and postolivary sulcus. A) Cranial nerve VII (hypoglossal) is the only cranial nerve to come out of the preolivary sulcus. B) The glossopharyngeal (IX) and vagus (X) nerve come out of the post olivary sulcus respectively from superior to inferior on the medulla. The Vagus nerve is bigger than the hypoglossal and sits inferior to the glossopharyngeal nerve. C) Cranial nerves VI, VII and VII sit at the ponto-medullary junction. Cranial nerve VI (Abducens) is the only cranial nerve to extend rostral from the medulla. Caudal Medulla 1) The cerebellum must be removed to view the caudal medulla. 2) The deep depression is the fourth ventricle and where the fourth ventricle ends is called the obex 3) The posterior median fissure is present as in the spinal cord 4) Lateral to the obex is the Cuneate Tubercle which carries lower limb sensory information. 5) Posterior to the Cuneate Tubercle is the Gracile Tubercle that carries upper limb sensation. 6) Posterior to the Gracile Tubercle is the Trigeminal (V) tubercle that carries sensory information to the face. Cerebral Peduncles 1) Tracts that connect the brainstem and cerebellum 2) Inferior cerebellar peduncle connects the medulla and cerebellum 3) Medial cerebellar peduncle connects the pons and cerebellum 4) Superior cerebellar peduncle connects the midbrain and the cerebellum. Ventral Pons 1) The middle cerebellar peduncle is where the pons blends in to the cerebellum. 2) Cranial nerve IV(trochlear) and V (trigeminal)are associated with this area. Trochlear is the smallest cranial nerve and trigeminal is the biggest. 3) Basilar Pons is the base of the pons. Dorsal Pons 1) Extension of the fourth ventricle when cerebellum is removed. Ventral Midbrain 1) Oculomotor nerve (III) runs bilateral to the interpeduncular fossa. 2) Cerebral peduncles lie lateral to the oculomotor nerves. This is where the forebrain is connected to the brain stem. 3) Cerebellum ends at the midbrain. 4) Tectum- roof of the cerebral aqueduct Dorsal Midbrain 1) Dorsal tectum made up of four elevations called colliculi 2) closest to the pons- inferior colliculus which is involved in audition 3) superior colliculus- involved in the visual system 4) Under the inferior colliculus is the trochlear nerve (IV) which is the only cranial nerve dorsal to the brainstem and decussates Ventral Diencephalon 1) Begins at mammillary bodies and ends at optic chasm 2) Know optic nerves, optic chiasm and optic tract location Dorsal Diencephalon 1) Know the thalamus and hypothalamus from medial view 2) All sensory information goes through the thalamus except smell 3) Dorsal to the thalamus is the fornix which links the limbic system to the hypothalamus 4) Dorsal to the fornix is the corpus callosum which connects the two cerebral hemispheres. Telencephalon 1) Lateral sulcus- rostral to caudal 2) Central sulcus- dorsal to lateral sulcus. Brain stops the regions from meeting with a thin piece of brain tissue 3) Temporal lobe is where hippocampus is located 4) Insular cortex- taste, autonomic, pain and balance information. Can be seen if you pull back the lateral sulcus. 5) With the medial slice of the brain there is no problem identifying the parietoccipital sulcus. Harder to identify with a lateral view of the brain. 6) Calcarine sulcus- primary visual cortex. Inferior to the Parietooccipital sulcus 7) Cingulate lobe- emotional aspects of pain. Old part of the cortex that is wrapped around the thalamus.
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