Nervous System.docx

[Nervous System ] What is it made up of? Neurons -- electrically active cells which transmit neurotransmitters through synapses Glial cells -- support neuron but also allow for optimal physiochemical environment (some produce myelin which is white and helps insulate fibres of neurons. Categorize...

[Nervous System ] What is it made up of? Neurons -- electrically active cells which transmit neurotransmitters through synapses Glial cells -- support neuron but also allow for optimal physiochemical environment (some produce myelin which is white and helps insulate fibres of neurons. Categorized into: Central nervous system (CNS) -- spinal cord and brain Peripheral nervous system (PNS). -- Cranial nerves (12 pairs in the periphery), spinal nerves (31 pairs) and associated ganglia \*Human spinal nerves -- 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal [Sensory division (Afferent)] Towards CNS = Sensory (Afferent), information must be passed from spinal cord to brain Somatic sensory - e.g. touch, pain, vibration, temperature Visceral sensory -- e.g. stretch, pain, visceral irritation, nausea and hunger [Motor division (Efferent)] Away from CNS = motor (Efferent), commands from the brain must be sent out to the PNS Somatic motor -- e.g. use of skeletal muscles Visceral motor -- e.g. innervation of smooth + cardiac muscles and glands [Somatic VS Visceral control] Autonomic nervous system = visceromotor system - Consists of involuntary actions e.g. heart, lungs, GIT, smooth muscles, glands, pupil. Purely motor system - 2 divisions sympathetic and parasympathetic [Grey matter VS White matter ] Grey Matter - Is cell bodies, dendrites and unmyelinated axons - Located outside the brain (cerebral cortex) and in deep nuclei (dumps of cell bodies) - Spinal cord -- form the inner horns - PNS -- neuronal cell bodies are in the ganglia laying outside spinal cord White Matter - Mainly axons, myelinated - Funiculi -- surrounds the horn within the spinal cord - Fasciculi -- small bundles of nerve fibres with common origin, destination and function [Corpus callosum:] Wide flat bundle of myelinated axons that cross between cerebral hemispheres (commissural fibres) Allow inter-hemispheric communication Largest white matter structure of Brain [Brain Terminology ] Gyri (Gyrus) -- hills Sulci (Sulcus) -- grooves Fissure -- a deep groove or cleft [Structure of Brain] Frontal Lobe - located at anterior of brain, controls speech, motor cortex is in this lobe Parietal Lobe -- Mid-section of brain, control speech, taste and reading, somatosensory cortex is in this lobe Occipital Lobe -- Posterior of brain, controls vision Temporal Lobe -- bottoms part of brain, controls hearing and smell Cerebellum- bellow temporal lobe [General Points for Cerebral Cortex] Is covered by grey matter Makes up 80% of the brain 2-4mm thick Consist of 6 layers Left and right connected by corpus callosum [Cerebrospinal Fluid (CSF)] - Fills cerebral ventricles, central canal of spinal cord and flows over surface of tissue - Like plasma but without protein - Functions include cushioning, homeostasis, chemical buffer - Continuously produced by choroid plexus - Circulatory system: CSF ends up being absorbed into venous blood via meninges [Sympathetic Nervous System ] - Originate at T1-L2 - Enter sympathetic chain - Leave sympathetic chain - Synapse at prevertebral chain - Slow digestive transit - Closes sphincters - Flight or Fight [Parasympathetic Nervous System ] - Originate at brainstem or S-levels - Travel to target organ - Synapse at target - Increase digestion - Opens sphincter - Rest and Digest