The Nervous System PDF

3. The Nervous System Human Anatomy & Course Physiology Status Complete Materials 4. Nervous System - Slides Date @September 10,...

3. The Nervous System Human Anatomy & Course Physiology Status Complete Materials 4. Nervous System - Slides Date @September 10, 2024 Table of Contents The Nervous System The Central Nervous System The Peripheral Nervous System Terms Neural Tissue Protection and Segregation Meninges Cerebrospinal Fluid Glial cells Anatomy of Spinal Cord & Nerves Longitudinal Structure Nerves Dermatome Plexus 3. The Nervous System 1  Receptors Cross-Section Spinal Cord Reflex Components of the Reflex Arc Withdrawl (Pain) Reflex The Stretch or Patellar Reflex The Nervous System Function: Regulates and communicates Senses: detects a change in a variable Integrates: input is received, decision is made, command is sent out Responds: effector organs respond Is divided into the CNS and PNS The Central Nervous System Function: a control center Consists of the brain and spinal cord The Peripheral Nervous System Function: Provides links to and from the outside (efferent & afferent path) Consists of receptors, nerves, ganglia and motor nerve endings 3. The Nervous System 2  Subdivided based on effector into: Somatic Division: skeletal muscles Autonomic Division: smooth & cardiac muscles, glands Terms Gray matter: group of cell bodies White matter: collection of axons Center or nucleus: in CNS Nerves: are bundles of axons Cortex: layer in CNS Tracts: are bundles of axons that share a common origin, Ganglion: in PNS function or destination Pathway: link Columns: are groups of tracts Sensory or ascending paths: PNS Organs include: brain, spinal cord, to CNS receptors, nerves Motor or descending paths: CNS to PNS Neural Tissue Protection and Segregation Bones of vertebral column and skull Meninges: 3 membrane wrappings Dura Mater: is a tough outer layer Arachnoid Mater: is a middle layer with extending fibers Pia: Mater is innermost layer that adheres to nervous tissue following its folds Cerebrospinal fluid: cushions Glial cells: support and protect neurons Cellular barriers: segregate CNS i.e. BBB 3. The Nervous System 3  Meninges Function: 1. form protective wrappings 2. carry nerves & blood vessels 3. Form attachment sites 4. form spaces that hold fluids or fat Subarachnoid space: holds CSF Epidural space: holds fat (spinal cord only) Subdural space: contains small amount of fluid that adheres by surface tension the dura to the arachnoid creating a double membrane Dural spaces (sinuses): hold veins (brain only) Cerebrospinal Fluid 3. The Nervous System 4  Function: 1. sink-like role aids in maintaining environment around neurons 2. Cushions (SAS) 3. Brain floats in CSF reducing weight: 1400g → 50g 4. Provides nutrients to cells lining the path of circulation Structure: Is formed from blood by choroid plexus found in each ventricle Choroid plexus: 2 cell layer (wall of capillary + ependymal cell) that filters and adjust blood plasma CSF circulation: choroid plexus → ventricles (lateral, third, fourth) SAS → arachnoid villi → dural sinuses (venous blood) Arachnoid villi: one-way valves in SAS that return CSF to blood via dural sinuses Glial cells 3. The Nervous System 5  Function: support the neuron and form cellular barriers Blood brain barrier: consists of foot processes of the astrocyte and the blood vessel wall (simple squamous epithelial) Nutrients and ions pass through 2 layer i.e. is filtered and adjusted Pia glial barrier: Astrocyte Foot processes line the pia mater Blood retina barrier Anatomy of Spinal Cord & Nerves Longitudinal-section CNS vs PNS Cross-section Cell components 3. The Nervous System 6  Longitudinal Structure Cervical enlargement Lumbar enlargement Central canal Conus medullaris Cauda equina Nerves & Plexus Cervical Thoracic Lumbar Sacral Nerves Nerves: are groupings of axons that travel together in the PNS connecting receptors & effectors to CNS Nerves carry myelinated and unmyelinated axons through the periphery Most are mixed: carry both sensory and motor info 3. The Nervous System 7  Within a nerve, axons travel in tracts wrapped in membranes Brachial plexus Dermatome Plexus Derma: skin, Tome: a cutting Plexus: a branching and rejoining Dermatome: Specific segment or of nerves creating alternative area of skin that is supplied by a paths single nerve Function: Ensures that info to and Dermatome map follows a from limbs is not carried in one segmental pattern because are path but many derived in the embryo from cells of a somite these cells develop into Incase of injury, not all function to that area is lost 1. Myotome or skeletal muscle 2. Dermatome connective tissue including skin 3. Sclerotome which gives rise to vertebrae 3. The Nervous System 8  Clinically they can indicate potential damage to one or more spinal nerves (somatic dysfunction or viral infection) 3. The Nervous System 9  Receptors Receptors: Neural tissue Types: specialized to detect stimuli Mechanoreceptor: respond to Simple receptor: a dendrite ending membrane distortion Baroreceptor: pressure (stretch) Chemoreceptor: chemcial Thermoreceptor: temperature Nociceptor: pain Interceptors and exteroceptors Proprioceptors: “ones own”, receptors in joints and muscles for body position Cross-Section 3. The Nervous System 10  1. Sensory 10. Dorsal ramus Neuron 11. Ventral ramus 2. Motor 12. Communicants Neuron 13. Grey Ramus 3. Dorsal Grey Communicants Commisure 14. White Ramus 4. White Communicants matter (columns) 15. Sympathetic Ganglion Chain 5. Gray matter (horns) 16. Sympathetic Cord 6. Ventral root 17. Sympathetic Ganglion 7. Dorsal root 18. Collateral 8. Dorsal root Ganglion ganglion 9. Spinal Nerve 3. The Nervous System 11  Gray matter: consists of interneurons and synapses Dorsal horn: somatic sensory axons synapse with interneuron Lateral Horn: autonomic sensory axons synapss with interneuron interneurons synapse with autonomic motor neurons Ventral horns: somatic interneurons synapses with Corticospinal: carry motor info for motor neurons voluntary control of skeletal muscles White matter: carries axons and myelinated axons to and from the brain Dorsal Columns: carry sensory info of fine touch and pressure Spinal Cord Functions: Highway for ascending and descending tracts linking PNS and CNS Integration (control center) for reflexes Reflex Reflex: a rapid, involuntary response to a stimuli Reflex arc: the path of nerve impulses from stimuli to response Characteristics of all reflexes: maintain homeostasis 3. The Nervous System 12  predictable response involuntary rapid response innate or learned Components of the Reflex Arc Receptor: is dendrite ending of a sensory neuron Afferent path: is the dendrite/axon of the sensory neuron in the nerve and dorsal root Control center: is the synapse or interneuron (relay) in the gray matter Efferent path: is the axon of the motor neuron in the ventral root and nerve Effector: is the muscle or gland Withdrawl (Pain) Reflex The Stretch or Patellar Reflex 3. The Nervous System 13  Collateral branches of the interneuron: allow for a more complex coordinated response Antagonistic muscles are inhibited Polysynaptic ipsilateral: on the same side of body Report is sent to brain 3. The Nervous System 14