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Nervous system

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Kinesiology & Health Science
KINE 2031
Neil Smith

Nervous system (p115 onwards) Sensory – Detects changes in environment, located throughout the body - Receptors capable of detecting both external and internal changes. Integration – Nervous system processes sensory input and decides if a response is required Motor Output – Nervous system sends down motor message to respond to stimulus (Only if integration decides a response is needed) Central Nervous System (CNS): Consist of brain and spinal cord, encased in bone as a form of protection of delicate organ system. - Functionally grouped into: sensory, motor, and connector/interneurons Peripheral Nervous system (PNS): Located outside of CNS – Functional division as follows: a. Sensory (Afferent): Responsible for receiving information from receptors and transmitting to the CNS Split into two groups: Sensory somatic (Body): eg. Touch, pain and pressure Visceral (Organs): Blood vessels, digestive organs, respiratory organs - Most of the time does not reach conscious levels, unless sensation is extreme (eg. Stomach being stretched) b. Motor (Efferent): Responsible for transmitting motor impulses from CNS to muscles/glands. Somatic (Body): eg. Conscious contraction of striated/skeletal muscles Visceral (Organs): unconscious (autonomic) contraction of smooth muscle, cardiac muscle/glands i. Sympathetic ii. Parasympathetic Functional Unit Neuron: Functional unit of nervous system (carries out function by receiving electrical stimulus and transmitting it) Neuron structure Cell body – contains the cell body, nucleus and mitochondria Dendrite(s) – extension of cytoplasm that are responsible directing information towards the cell body. Axon – extension of cytoplasm for directing information away from cell body Non-Nervous Cells: Neuroglial Cells in the CNS Astrocytes –cell processes sticking out – acts as blood-brain barrier - Positioned in between blood vessels (capillaries) and neurons. They regulate what substances come in contact with neurons. - Also provides structural integrity. Oligodendrocytes – Smooth, bullous shape. - Extension wrap around axons to produce myelin sheath (Myelin is fatty coating around axons that insulates) - Myelin appears lighter in colour therefore axons that are myelinated are said to be white matter of the CNS. Microglial Cells – Mimics bodies lymphatic system, cell that destroys pathogens. Ependymal Cells – Simple cuboidal epithelial cells with specialized cilia – Living in the cavity of spinal cord - Cilia secrete to make Cerebral spinal Fluid (CSF) Non-Nervous Cells – Peripheral Nervous System Satellite Cells – Cover the cell body in the ganglia. - Important for regulation of exchange of nutrients and waste between neurons an ext. environment Schawnn (Neurolemmocytes) cells – Forming myelin sheath around axons in the PNS The Brain – Fore, Mid and Hind Regions Forebrain: Cerebrum, Thalamus, Hypothalamus, Basal Ganglia Cerebrum – Divided into two hemispheres, most of forebrain. - Outer covering is called the cortex, consist of non-myelinated cell bodies (Gray Matter) - Convoluted/folded – grooves are Sulci and the hills between grooves are called Gyri - Longitudinal Fissure, (sulci groove) that separates the cerebral hemisphere - Central Sulcus – separates the Frontal lobe from Parietal Lobe - Lateral Sulcus – superior border for Temporal Lobe - Parieto-occiptal Sulcus – separates Parietal Lobe and Occipital Lobe - Insula lobe is located deep to the Temporal Lobe - Gyrus infront of Central Sulcus is called Pre-Central Gyrus – responsible for Motor Function - Behind is termed Post-Central Gyrus – responsible for Sensory Information. White Matter – Beneath the Gray matter of the cortex are myelinated axons of neurons. Axons that joni gyri in the same hemispheres are called Association type tracts. - Commissural tracts – myelinated axons that join the right to left hemispheres. An example of the largest is termed the Corpus Callosum - Projection tracts/fibres – myelinated axons that transmit sensory info up the cortex –or- that transmits motor information down through the cerebrum. Gray Matter - All outside consists of non-myelinated axons (lots of cell bodies). Floor of forebrain nuclei of neurons group together to form distinct structures: 1. Thalamus – relay centre for almost all sensory information that goes through cerebral cortex 2. Hypothalamus – Controller for the Autonomic Nervous System and Endocrine System 3. Basal Ganglia – Grouping of cerebral nuclei receive information from cerebral cortext to regulate skeletal movement Midbrain – In between the forebrain and hindbrain. Functions: Nuclei of the two cranial nerves control the movement of the eyes - Superior Cerebellar Peduncles are motor tracts that run back to the cerebellum - Visual and Auditory reflex centres Hindbrain – consists of two parts, the Pons and the Medulla Oblongata. Pons – Regulates breathing: rate and depth. - Contains the nuclei of cranial nerves 5-8 (5,6,7,8) - Peduncles comes off the pons and travels back to the cerebellum (Mid Cerebellar Peduncles) Medulla Oblongata – Reflex centres that regulate vital functions (HR, Breathing rate, BP) - Contains cranial nerves 8-12 - Inferior Cerebellar Peduncles connects to the cerebellum Cerebellum – similar to the cerebrum that is outer layer is cortex and convoluted (gyri and sulci). Responsible for coordination of motor movement - Two hemisphere separated by a narrow midline called Vermis - Arbor Vitae (tree) – is the term to describe the myelinated axons that resemble the branching of a tree Meninges – protective layer that covers the brain and spinal cord - Dura Mater, outer layer; Arachnoid, middle; Pia Mater, inner most deep layer. - Dura Mater, vertical fold of Dura located in the longitudinal Fissure which forms the Falx Cerebri. - Vertical fold between two lobes of the Cerebellum forms Falx Cerebelli - Horizontal fold between the Cerebellum and the occipital lobes forms Tentorium Cerebelli - ‘Roof’ of dura over the Sella Turcica of the Sphenoid bone forms the Diaphragma Sellae  Saddle Shape contain the pituitary - Arachnoid Granulation (Villi) extends in opposite directions, into the Superior Sagittal Sinus. sub space of Arachnoid consists of CSF - Follows same contour as Dura Mater - Connected to the underlying Pia Mater via strands called Trabeculae (spider like)  Arachnoid and Pia termed subarachnoid space - Pia Mater – delicate inner meningeal layer – follows contours of Cerebral Cortex Venous Sinuses – Edges of Dural Folds are venous channels/sinuses, carries deoxygenated blood away from the brain - Superior Sagittal Sinus – Top edge of Falx Cerebri - Inferior Sagittal Sinus – Bottom free edge of Falx Cerebri - Inferior Sinus continues and meets Superior Sinus via the Straight Sinus (confluence) - Occipital Sinus Located in the Falx Cerebelli (Confluence) - Right and Left Transverse Sinuses located in outer edge of Tentorium Cerebelli - Continues anteriorly as the Sigmoid Sinuses (S-Shaped), where the Confluence (Straight sinus + superior sagittal) drains into. - The Sigmoid Sinuses exit cranial cavity as the L-R Internal Jugular Veins Inside Sella Turcica – Cavernous sinuses (cave) drain into either sides located at the Diaphragma Sallae - Draining back to the Sigmoid Sinuses from Cavernous are the L&R Inferior and Superior Petrosal Sinuses. Ventricles – spaces or cavities withing the brain, these spaces communicate with each other. L&R Lateral Ventricle – communicate with midline 3 Ventricle via Interventricular Foramina rd - 3 Ventricle located between the two Thalami, continues in the mibrain region as Cerebral Aqueduct - Cerebral Aqueduct cont. in Pons region as the 4 Ventricle  Central Canal of the Spinal cord th 
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