Anat Introduction to the Brain PDF

Introduction to the brain, neurons and glia, overview of the nervous system and its development, structure of the CNS Class Year 2, Semester 1 Lecturer DR. VIJAYALAKSHMI S B Department of Anatomy Email id: [email protected] Date 27-1...

Introduction to the brain, neurons and glia, overview of the nervous system and its development, structure of the CNS Class Year 2, Semester 1 Lecturer DR. VIJAYALAKSHMI S B Department of Anatomy Email id: [email protected] Date 27-10-2024 1  Learning Outcomes Define basic neuroanatomical terms Describe the features and characteristics of cells of the nervous system and myelin Differentiate projections, commissures and association fibres Identify the meningeal layers List the main components of the nervous system Describe the process of neural tube formation and early brain development (fore-, mid- and hindbrain) Describe the parts of the central nervous system Identify the parts of the ventricular system Describe the structure of the different components of the peripheral nervous system (cranial and spinal nerves) Explain cauda equina syndrome  Components of Central Nervous System & correlate with development Brain Hindbrain (Rhombencephalon) Medulla (Myelencephalon) Pons = Brainstem *excludes cerebellum (Metencephalon) Cerebellum Midbrain (Mesencephalon) Forebrain (Prosencephalon) Diencephalon Epithalamus Subthalamus Thalamus Retina & Optic nerve Hypothalamus Telencephalon Basal Ganglia (Striatum) Limbic system Cerebral hemispheres Spinal cord  CNS Development  Neurulation  Process involved in the formation of neural tube https://www.ibp.ucla.edu/research/phelps/neuru.php  Neural tube is the primordium of the CNS (brain & spinal cord)  Neurulation begins at the end of 3rd week and completes by end of 4th week  Notochord induces the overlying ectoderm, located at or adjacent to the midline, to thicken and form an elongated neural plate of thickened epithelial cells  https://www.ibp.ucla.edu/research/phelps/tr ans.php https://www.ibp.ucla.edu/research/phelps/s agit.php  Neural plate invaginates along its central axis to form a longitudinal median neural groove, which has neural folds on each side  By the end of the third week, the neural folds have begun to move together and fuse, converting the neural plate into the neural tube  The neural tube soon separates from the surface ectoderm  The zipping process begins at about day 22 Tube closes completely at the cranial end 3 or 4 days later and at the tail (caudal) end 2 to 3 days subsequently (day 27) Neurulation is then complete - CNS is a closed tube  Narrow caudal end = spinal cord  Broader region at head region = brain  NEURAL TUBE DEFECTS If the neural tube fails to close in If closure fails anywhere from the the cranial region, then most of cervical region caudally, then the the brain fails to form, and the defect is called Spina bifida defect is called Anencephaly  Neural tube closure defects A. Rachischisis/Myeloschisis, B. Spina bifida occulta, C. Meningocele, D. Myelomeningocele Divisions of Neural tube  Protective layers of the brain Skin Connective tissue Aponeurosis Loose areolar tissue Periosteum Bone Dura Arachnoid Pia BRAIN  Meningeal layers The meninges P.A.D. the Brain…Inside to outside Pia mater/soft: very outer layer of brain tissue and intimately connected with the brain. When you are pressing on “brain”, you are touching pia matter Subarachnoid space = region where CSF is found. Arachnoid mater/spidery: arachnoid is the thin, transparent tissue that covers the brain Subdural space Dura mater/hard: Thick, fibrous, connective tissue often more intimately associated with the skull and forms partitions between hemispheres Extradural/Epidural space  In the skull, epidural space is a “Potential” space  In the vertebral column, there is “True” epidural space Lobes of Cerebrum Insula  Grey matter and White matter Grey matter - neural tissue that is grey in colour and is comprised of neural cell bodies (i.e., where the nuclei/ganglia are in the brain) …along with other connective tissue and immune cells White matter - neural tissue that is white in colour and is comprised of myelinated axons (which gives it its white colour) …along with other connective tissue and immune cells Collection of nerve cell bodies in Central Nervous System  Gray mater  Nuclei  Layers Collection of nerve cell bodies in Peripheral Nervous System  Ganglia  e.g. Dorsal root ganglion (DRG) Collection of nerve cell fibers in Central Nervous System  White mater  Column  Fascicles  Peduncles  Tract  Radiation Collection of nerve cell fibers in Peripheral Nervous System  Spinal/ Cranial Nerves  motor  sensory  autonomic  mixed  White matter of the Cerebral hemispheres Classified into three groups according to their connections: 1. Commissural fibers 2. Association fibers 3. Projection fibers  White matter of the Cerebral hemispheres Commissure fibers  Connects corresponding regions of the two hemispheres  Includes: a. Corpus callosum b. Anterior commissure c. Posterior commissure d. Fornix e. Habenular commissure  White matter of the Cerebral hemispheres Association fibers  Connects various cortical regions within the same hemisphere  Includes: a. Uncinate fasciculus b. Cingulum c. Superior longitudinal fasciculus d. Inferior longitudinal fasciculus e. Fronto-occipital fasciculus  White matter of the Cerebral hemispheres Projection fibers  Afferent and efferent nerve fibers passing to & from the brainstem to the entire cerebral cortex  Includes: a. Internal capsule b. Corona radiata c. Cortico spinal tract d. Sensory tracts  Cerebral cortex – functional localization 1. Motor area (4) 2. Sensory area (3, 1, 2) 3. Visual area (17, 18, 19) 4. Speech area (44,45) 5. Auditory area (41,42)  BASAL GANGLIA (NUCLEI)  They are collections of grey matter within the cerebral hemisphere  The components:  Lentiform nucleus (Globus pallidus & Putamen)  Caudate nucleus  Its main function is the maintenance of motor activity and muscle tone and coordination of movements and prevents involuntary movements.  DIENCEPHALON Thalamus Hypothalamus Thalamus – all the sensory tracts from the body relay in the thalamus before they terminate in the sensory cortex of the cerebrum Hypothalamus- Control of the body temperature Control of endocrine function Control of behaviors & emotion Control of Autonomic nervous system Neurosecretions  Cerebellum  Situated behind the pons and the medulla  Coordinates voluntary movements such as posture, balance resulting in smooth and balanced muscular activity.  Each cerebellar hemisphere controls the same side of the body  Brain stem VENTRAL DORSOLATERAL Medulla Midbrain Pons Pons Midbrain Medulla Cranial nerve nuclei from 3rd to 12th are in the brain stem Ventricular system Flow of Cerebrospinal fluid (CSF)  NAME TYPE DISTRIBUTION Olfactory N I Sensory Nasal mucosa ( smell/olfaction) Optic N II Sensory Eye ( vision) Oculomotor N III Motor Extraocular muscles (eye movement); Parasympathetic innervation of the eye Trochlear N IV Motor Extraocular muscles (eye movement) Trigeminal N V Motor/Sensory Sensory to face; Muscles of mastication (motor) Abducent N VI Motor Extraocular muscles (eye movement) Facial N VII Mixed Muscles of facial expression; Taste Parasympathetic innervation of salivary and lacrimal glands Vestibulocochlear N VIII Sensory Ear (hearing/balance) Glossopharyngeal N IX Motor/Sensory Taste; General sensory and motor innervation of the pharynx Visceral innervation from carotid body and sinus Parasympathetic innervation of the salivary gland Vagus N X Motor/Sensory General sensory and motor innervation of pharynx, larynx and oesophagus Visceral innervation from thorax and abdomen, including aortic body and arch Parasympathetic innervation of thoracic and abdominal viscera Accessory N XI Motor Muscles of neck (Movement of head and shoulders) Hypoglossal N XII Motor Muscles of the tongue (Movement of the tongue)  Spinal cord Continuation of the brain stem into the spinal canal Spinal cord extends from the foramen magnum of the base of the skull to lower border of the first lumbar vertebra Clinical correlate Lumbar Puncture – What is it? – Indications? – How it is done – Expected result  SPINAL CORD SEGMENTS AND SPINAL NERVES Cervical (8) Thoracic (12) Lumbar (5) Sacral (5) Coccygeal (1) Lower spinal nerves are grouped to form the cauda equina Vertebral level/spinal cord segments Spinal segments do not match with the corresponding vertebra Vertebrae Spinal segment Cervical +1 Thoracic 1-6 +2 Thoracic 7-9 +3 Thoracic 10 L1 & 2 Thoracic 11 L3 & 4 Thoracic 12 L5 Lumbar 1 Sacral/coccygeal White matter arrangement of spinal cord Corticospinal tract Spinothalamic tract Dorsal column & Spinocerebellar tract  CAUDA EQUINA SYNDROME (CES) Condition that occurs when the bundle of nerves below the end of the spinal cord, known as the cauda equina, is damaged. The term Cauda Equina means ‘horse’s tail’ in Latin and describes the spray of nerves that come off the bottom of the spinal cord and activate the bladder, bowel, sexual organs and legs. When these nerves are compressed or damaged, the impact on the sufferer can be devastating. Signs and symptoms of CES include lower back pain, pain that radiates down the leg, and loss of bowel or bladder control. Causes CES:  Back/Spine problems such as a slipped disc  Tumors near the spine  Injuries Warning Signs:  S – Saddle Anesthesia  P – Pain  I – Incontinence  N - Numbness  E - Emergency REFERENCES