Neuroanatomy - Part 1 PDF

Neuroanatomy – Part 1 Maria Hill PP6012 Learning Outcomes To gain an understanding of the following: Cells of the Nervous System Communication within the Nervous System Structural and Functional Divisions of the Nervous System Somatic vs Autonomic Nervous System The Cerebral Cortex and connections F...

Neuroanatomy – Part 1 Maria Hill PP6012 Learning Outcomes To gain an understanding of the following: Cells of the Nervous System Communication within the Nervous System Structural and Functional Divisions of the Nervous System Somatic vs Autonomic Nervous System The Cerebral Cortex and connections Functional areas of the cerebral cortex The Limbic System and Hypothalamus Recommended Reading Clinical neuroanatomy and Neuroscience. 5th Edition. Fitzgerald, Gruener, Mtui. Neuroanatomy. An Illustrated Colour Text. 6th Edition. Crossman & Neary. Gray’s anatomy for Students. 4th Edition. Drake, Vogl, Mitchell. The Human Nervous System. An Anatomical Viewpoint. 2nd Edition. Barr, Murray. http://www.neuroanatomy.ca/ https://nba.uth.tmc.edu/neuroanatomy/index.html Tissue of the Nervous System Neurons Nerve Cells Structural and Functional unit of the Nervous System Specialised for rapid communication CNS and PNS Glial Cells/Neuroglia Support cells Insulate, Nourish, Protect, Secrete Myelin Sheath Modulation of neurotransmission CNS - Oligodendrocytes PNS - Schwann cells Tissue of the Nervous System Astrocytes Star shaped Nourishment Synapse formation and regulation Microglia Produced in bone marrow Defence Immune System Satellite Cells Astrocytes of the PNS Nourish Neurons Maintain environment Communication within the Nervous System Synapse - Region of communication between neurons How?? Neurotransmitters transmit information from one neuron to another Chemical agents Secreted by neurons Neurotransmitters Chemical messengers >100 known Present in presynaptic membrane Released in response to depolarisation Specific postsynaptic receptors Large - Neuropeptides Small - Single amino acids EGs - Acetylcholine, Glutamate, GammaAminobutyric Acid, Dopamine, Adrenaline (Epinephrine), Noradrenaline (Norepinephrine), Serotonin The Firing Neuron Polarisation Repolarisation Chemical Transmission Depolarisation https://www.youtube.com/watch?v=XnksofQN8_s The Myelin Sheath An insulating layer surrounding the neuron Protein and fat Produced by Schwann cells/Oligodendrocytes Allows efficient transmission of electrical impulses Clinical – Demyelination eg Multiple Sclerosis Central Nervous System Functions Integration and co-ordination of incoming and outgoing neural signals or information Carrying out higher mental functions e.g. thinking and learning Central Nervous System White and Grey Matter White = Myelin Sheath Group of Cell bodies in CNS = Nucleus/Nuclei = Grey Bundle of Axons in CNS = Tract = White Peripheral Nervous System Function - To carry information TO and FROM the CNS Group of cell bodies = Ganglion Bundle of Axons = Peripheral Nerve Afferent fibres = Arrive at the CNS = Sensory Neurons Efferent fibres = Exit from the CNS = Motor Neurons Peripheral Nerves Cranial Nerves Emerge from the “cranium” Exit via foramen 12 pairs Spinal Nerves Emerge from the “Spinal Cord” Exit via Intervertebral Foramen 31 pairs Formation of a Spinal Nerve Anterior/Ventral and Posterior/Dorsal Horns, Rootlets, Roots Anterior Root - Motor Fibres Posterior Root - Sensory Fibres Posterior/Dorsal Root Ganglion Roots unite to form a Mixed Spinal Nerve Anterior Ramus and Posterior Ramus both have mix of Motor and Sensory Fibres The Somatic Nervous System Function Provides Sensory and Motor information to all parts of the body under voluntary/conscious control Sensory and Motor Neurons Autonomic Nervous System (ANS) Function Provides Sensory and Motor information to all parts of the body that are NOT under voluntary control Includes sympathetic and parasympathetic neurons Eg Heartbeat Neurotransmitters: Noradrenaline, Adrenaline, Acetylcholine SNS and Para SNS - 2 Neuron Series The cell body of the preganglionic neuron lies in the gray matter of the CNS. Its axons terminals synapse with the cell body (dendrites) of the postganglionic neuron The cell body of the postganglionic neuron lies in ganglia outside the CNS. Its axons terminals terminate on an effector organ inducing a response SNS Ganglia SNS Ganglia Paravertebral Superior cervical - head and neck, BS brain, eyes, lacrimal and salivary glands Middle/Inferior cervical - heart, lungs, bronchi Thoracic Lumbar Sacral Travel with spinal nerve - blood vessels, sweat glands Prevertebral Celiac Ganglion - smooth muscle/glands of stomach, small intestine, liver, spleen, pancreas, kidney Superior Mesenteric ganglion - distal small and large intestine Inferior Mesenteric ganglion - Inferior Hypogastric plexus Colon, rectum, urinary bladder, sex organs Para SNS – “Rest and Digest” Craniosacral Cillary Ganglion (CNIII) Pterygopalatine (CNVII) Submandibular (CNVII) Otic Ganglion (CNIX) Cardiac and Pulmonary Plexus (CNX) Celiac Plexus (CNX) Inferior Hypogastric Plexus (S2-4) Components of the CNS CNS = Brain + Spinal Cord Brain Cerebrum Diencephalon Thalamus Hypothalamus Pituitary Gland Pineal Gland Brainstem Midbrain Pons Medulla Cerebellum Divisions of the brain Forebrain Telencephalon & Diencephalon Midbrain Mesencephalon Hindbrain Metencephalon & Myelencephalon Interesting facts Humans have the largest brain relative to body size Human brain is 4 times larger than that of a gorilla Brain of a dolphin is larger than that of a human Same structures, different volumes Brain size at birth is 25% of adult size The Cerebrum Right and Left Hemispheres Divided by longitudinal fissure Gyri - Folds Sulci - Fissures Only one third of cortical surface exposed Cortex Gray and White Matter Cerebral White Matter – 3 Types of fibres Commissural fibres Connect gyri in opposite hemispheres (pass through corpus callosum) Association fibres Connect different parts of the same cerebral hemisphere Projection fibres Ascending/descending tracts Lobes of the Brain Deepest sulci are central (Rolandic fissure) and lateral sulcus (Sylvian fissure), which together with the parietooccipital sulcus divide each hemisphere into 4 lobes Frontal Parietal Temporal Occipital Limbic (Insular) Function of Lobes Frontal Motor, Planning, Reasoning, Language Production (Broca’s Area) Parietal Somatosensory Occipital Vision Temporal Hearing, Understanding Language (Wernickes Area) Functional Classification Cortex Primary Cortical Areas Association Cortices Where the integration of all the information occurs Makes us human! Brodmann’s Areas German Neurologist (1868 – 1918) Identified 52 distinct cortical areas Areas reflect functional differences Brodmann’s Areas Primary motor cortex (4) Primary somatosensory cortex (1, 2, 3) Primary visual cortex (17) Primary auditory cortex (41, 42, 22) Motor Cortex Frontal Lobe Primary motor cortex (4) Located in the precentral gyrus Somatotopically organized as the motor homunculus Contributes to the corticospinal tract Stimulation of this area results in contralateral movements of voluntary muscles Lesion ie Upper Motor Neuron Lesion (UMNL) results in contralateral paralysis Motor Cortex Premotor cortex (6 - lateral) Anterior to precentral gyrus Control of proximal and axial muscles Prepares the motor cortex for specific movements in advance of execution Postural control Stores motor programmes from past experiences Supplementary motor cortex (6 – medial) Located medial cortex Programming complex motor sequences ie planning movement Responsible for coordinated movement Lesion results in Apraxia Sensory Cortex Parietal Lobe Primary somatosensory cortex (1,2,3) Located in the postcentral gyrus Receives ascending input from the thalamus Somatotopically organized as the sensory homunculus Lesions may result in contralateral loss of sensation, - touch, proprioception, point localization, 2-point discrimination, vibration and pressure Sensory Cortex Somatosensory Association cortex (5, 7, 40) Receives input from primary sensory cortex, visual association cortex Responsible for interpretation of sensory information Lesion results in contralateral loss of tactile discrimination Left side lesions: Asterognosis (inability to identify objects), inability to perceive depth, Apraxia (inability to perform motor tasks/follow simple instructions Right side lesions: Visuospatial orientation deficits, Neglect Visual Cortex Occipital Lobe Primary visual cortex (17) Borders the calcarine sulcus Left visual field projected on right cortex and vice versa Lesions result in contralateral homonymous hemianopia Visual Cortex Secondary and tertiary visual cortices (18, 19) Project to extrastriate visual association cortex in parietal lobe (7) and inferior temporal lobe (20, 21, 37) Visual Association cortex (39) Receives input from 18 and 19 Responsible from processing of visual information Auditory Cortex Temporal Lobe Primary Auditory Cortex (41, 42) Located in the superior temporal gyrus Receives ascending input from the thalamus Responsible for the conscious perception of sound Unilateral lesion – no hearing loss Bilateral lesion – cortical deafness Auditory Cortex Auditory Association cortex (22) Wernicke’s Area Located in the posterior part of the superior temporal gyrus Responsible for understanding speech & language Lesion results in Wernicke’s Apahsia Broca’s Area (44, 45) Located in the inferior lateral frontal gyrus of the dominant hemisphere Connected to Wernicke’s area Responsible for speech production Lesion results in Broca’s Aphasia Areas of higher cortical function Prefrontal cortex (9-12) Located anterior to the motor and premotor areas Responsible for complex cognitive behaviour, personality expression, decision making, moderating social behaviour Lesion results in: Poor judgement and foresight Unresponsiveness to consequences of actions Poor decision making Failure to learn from experience Disinhibition Loss of social and moral restraints Inappropriate social conduct Emotional lability The Limbic System The Limbic lobe The Cingulate gyrus The Parahippocampal gyrus The Hippocampus (Memory) The Amygdala (Emotion) The Limbic System Responsible for instinctive and emotional aspects of behaviour Responsible for memory and adaptive behaviour based on previous experience Responsible for motivation Helps us to engage appropriately with our environment Lesions result in Alzheimer's Disease, Parkinson’s Disease https://www.youtube.com/watch?v=ErpxEwlW ww4&feature=youtu.be Memory Episodic Based on experience and learning from autobiographical events (Hippocampus). Memories associated with senses/emotions (Amygdala). Memories converted from short-term → long-term The Hypothalamus The most ventral part of the diencephalon Lies beneath the thalamus Forms the floor of the third ventricle Projects to the pituitary gland Responsible for maintaining homeostasis – critical for life Works alongside the limbic system The Hypothalamus Input Circulatory (Blood) – Physical, chemical, hormonal Neural (Hippocampus, Amygdala, Brainstem) Output Circulatory – Pituitary gland Neural – Cerebral cortex, brainstem – Autonomic Nervous System