Nervous System I and II (1) PDF

Nervous System Dr Ayman G. Mustafa Associate Professor  Objectives Identify and name the lobes, major sulci and gyri of the brain Explain the concept of functional localization of the brain Describe the functions of basal nuclei and diencephalon Differentiat...

Nervous System Dr Ayman G. Mustafa Associate Professor  Objectives Identify and name the lobes, major sulci and gyri of the brain Explain the concept of functional localization of the brain Describe the functions of basal nuclei and diencephalon Differentiate between the types of cerebral white matter Identify the parts and describe the functions of the brain stem State the functions of the cerebellum Describe the internal and external structure of spinal cords Understand the structure of spinal nerves Describe the major nerve plexuses and their main branches Differentiate between sympathetic and parasympathetic divisions of the nervous system 2  General Organization of the CNS Brainstem Cerebrum 1. Midbrain Diencephalon 2. Pons Cerebellum 3. Medulla oblongata 3  Cerebrum A B Longitudinal fissure divides cerebrum into right and left cerebral hemispheres Largest part of brain, controls higher mental functions Each cerebral hemisphere (A) consists of Grey matter, collection of cell bodies of neurons At surface, form cerebral cortex Buried deeply, form diencephalon (B) and basal nuclei White matter, which are axons of neurons forming tracts 4  Cerebral Cortex CENTRAL SULCUS G G G LATERAL G FISSURE Folded surface increases surface area, consist of Elevated folds or gyri (G) Shallow depressions or sulci Deep grooves or fissures 5  Grooves and Lobes of the Cerebrum (Lateral View) 6  Grooves and Lobes of the Cerebrum (Medial View) Frontal lobe Parietal lobe Occipital lobe C Temporal lobe Calcarine sulcus 7 Overview of Major Functional Cerebral Areas Longitudinal fissure 8  Motor and Sensory Homunculi All body parts are represented Each hemisphere receives (mapped) in the cerebral info from the opposite side of cortex in an inverted and the body disproportional manner 9  Functional Localization in the Cerebral Cortex I Hip Leg Foot Toes Genitals Primary somatosensory cortex Interpretation of somatosensation Intra-abdominal Spatial map of the contralateral half of the body (sensory homunculus) Area is proportional to density of sensory innervation of a given body part and not its size Medial Lateral 10  Functional Localization in the Cerebral Cortex II Hip Knee Ankle Toes Primary motor cortex Pharynx Controls of voluntary, skilled movement Spatial map of the contralateral half of the body (motor homunculus) Area is proportional precision of movement of body part and not its size Lateral Medial 11  Speech Areas Sensory (Wernicke’s) Speech Area Interpretation of words Connected with visual and auditory cortex Damage results in receptive aphasia Motor (Broca’s) Speech Area Controls ability to speak Damage to results in expressive aphasia 12 Functional Areas of the Cerebrum 13  Deep Grey Matter: Basal Nuclei Basal Nuclei Assist in the regulation of voluntary motor activities Modifies instructions sent to skeletal muscles by the primary motor cortex Lesions can result in Parkinson’s disease 14  Deep Grey Matter: Diencephalon Located under the cerebrum Links cerebrum with the brain stem Three main divisions of the diencephalon: Thalamus, 15 hypothalamus and epithalamus  Cerebral White Matter Commissural tracts (in corpus callosum) Cerebral nuclei Commissural fibers Corpus callosum is a large tract that connects both cerebral hemispheres Projection fiber tracts connect the cerebrum with lower CNS centers Association fibers connect areas within the same hemisphere Projection Thalamus tracts (b) Coronal section 16  Brainstem Include midbrain, pons and medulla oblongata Tractwear a In Processes information between spinal cord and cerebrum/ cerebellum Functions include: Provide pathway for ascending and descending tracts Contains grey matter nuclei associated with: Cranial nerves and Autonomic and vital centers Contains diffuse mass of grey matter (reticular 17 information) 117 important for consciousness Cerebellum Second largest part of brain, composed of two hemispheres Covered with cerebellar cortex (grey matter) and inner white matter (just like cerebrum) Coordinates repetitive smooth body movements Responsible for body balance and posture 18  Protections of the Brain Bone: Skull Membranes (meninges): Dura, arachnoid and pia 19 Fluid: Cerebrospinal fluid Blood Supply to the Brain Internal carotid system: Supply the cerebrum and diencephalon Vertebrobasilar system: From vertebral and basilar arteries, supply: brainstem, cerebellum and spinal cord Internal carotid a. C Anastomosis between the two systems ensure Makesnew adequate blood supply to the brain Vertebral a. 20  Spinal Cord: Overview Spinal cord is shorter than vertebral column Dura & arachnoid form the dural sac which extends to vertebral level S2 CSF in the expanded subarachnoid space between L2 and S2 is the lumbar cistern 21 External Features of the Spinal Cord Spinal cord ends as conus medularis at vertebral level L2 More caudal nerves descend to exit between appropriate vertebrae  This forms the cauda equina Pial extension from conus medullaris forms the filum terminale interna 22  Spinal Nerves Cervical - 8 Thoracic - 12 Lumbar - 5 Sacral - 5 Coccygeal - 1 23 31 pairs of spinal nerves emerge from 31 spinal cord segments Internal Features of the Spinal Cord 24 CNS Major Tracts in the CNS Two important concepts:  Ascending Tracts  Descending tracts 25 Structure of a Nerve Nerve: Bundle of neuron fibres surrounded by connective tissue  Each fiber is surrounded by endoneurium  A bundle of fiber is known as a fascicle, surrounded by perineurium  Fascicles are bound together by epineurium 26  Cranial Nerves Oh Oh Oh To Touch And Feel Very Good Velvet, A Ha 27 Distribution of Cranial Nerves mel islet the stnerve 28 Distribution of Cranial Nerves 29 Distribution of Cranial Nerves 30 Distribution of Cranial Nerves 31 Distribution of a Spinal Nerve Ramus Posterior ↑ ↓ Anterior (Ventral or anterior) 32  Distribution of a Spinal Nerve Ramus Dorsal root Dorsal ramus Ventral ramus Spinal nerve Ventral root Formed by union of dorsal & ventral roots Contain both sensory and motor ANTERIOR fibres (mixed nerves) Bifurcate to form dorsal & ventral rami (mixed nerves) Dermatomes and Myotomes Dermatome: the area of skin innervated by a given spinal level Myotome: the group of muscles supplied by a given spinal level Lesion of a given spinal nerve results in a stereotyped loss of sensory input and motor output 34 & Nerve Plexuses the peripheral vs Dorsal and ventral rami are mixed nerves Ventral rami of some spinal nerves blend to create compound nerves Each nerve carry axons from 2 or more spinal segments This network of ventral rami and the final compound peripheral nerve is called a nerve plexus 35 Formation of Nerve Plexuses 36 Major Nerves of the Upper Limb 37 Major Nerves of the Lower Limb 38  Major Nerves of the Lower Limb & est body largthe nerve 39 Overview of the Autonomic Nervous System Functions independently without conscious effort Regulates the activity of involuntary muscles  Cardiac  Smooth  Glands Responds to emotional stress and prepare the body for strenuous physical activity Part of the peripheral nervous system 40 Divisions of Peripheral Nervous System -- -u S 41  Somatic Nervous System vs. Autonomic Nervous System ANS has two efferent neurons between CNS and effector organ  Preganglionic neuron  Postganglionic neuron 42  Overview of Preganglionic and Postganglionic Neurons Preganglionic neurons arise from cell bodies in the brain and spinal cord Postganglionic neurons emerge from cell bodies in ganglia 43  Divisions of Autonomic Nervous System Neurotransmitters released by postganglionic neurons: Sympathetic: Epinephrine (adrenaline) /norepinephrine (noradrenaline) 44 Parasympathetic: Acetylcholine Structure of the Autonomic Nervous System Both serve the same organs, cause opposite effects Activities of each are counterbalanced 45 Parasympathetic vs Sympathetic Nervous System Parasympathetic division brings up relaxed state, allows conservation of energy Sympathetic division coordinates the body for the “fight or flight” response 46 Anatomy of Parasympathetic Division I  Preganglionic neurons are located in:  Brain nuclei of cranial nerves III, VII, IX and X  Spinal cord segment S2 to S4  Also called craniosacral division 47 Anatomy of Parasympathetic Division II  Preganglionic neurons in the  Cranial region: travel with fibers of cranial nerves, serve head and neck region  Sacral region: leave the spinal cord and form pelvic splanchnic nerves  Postganglionic neurons in the wall of viscera 48 Function of Parasympathetic Division 49 Anatomy of Sympathetic Division  Preganglionic neurons:  Located in the gray matter of spinal cord segments T1 to L2  Sympathetic division is also known as thoracolumbar division  Preganglionic neurons exit the SC and enter sympathetic trunk ganglion  Postganglionic neurons reenter the spinal nerve 50  Preganglionic Neuron of Sympathetic Division  Preganglionic neurons located in the gray matter of spinal cord  Exit through ventral root of spinal nerve  Travels through spinal nerve 51  Enters sympathetic trunk ganglia  Postganglionic Neuron of Sympathetic Division  Postganglionic neurons renters spinal nerve, exit through ventral ramus to effector 52 Sympathetic Pathways 53 Function of Sympathetic Division 54  storing & it dose effect in the liver the gleconce as glycogin in 55 55  nerve Radial neveeve Una