Download Central Nervous System - Human Physiology - Lecture Notes and more Study notes Human Physiology in PDF only on Docsity! Central Nervous System A. Development of the CNS - CNS develops from neural tube of embryo starting at ~ 3 weeks - anterior neural tube first differentiates into forebrain, midbrain, and hindbrain (4 weeks), then further develops into 6 major brain regions + spinal cord (6 - 11 weeks); - forebrain greatly enlarges to form cerebral hemispheres B. Supporting Structures of the CNS 1. Meninges - connective tissue coverings of the CNS dura mater arachnoid pia mater 2. Brain Ventricles and Cerebrospinal Fluid (CSF) - CSF produced by the choroid plexuses of the brain ventricles - CSF circulates through ventricles and into subarachnoid space - CSF composition is regulated; low protein concentration compared to plasma 3. Glial Cells - supporting cells of the NS astrocytes - provide physical and metabolic support to neurons blood-brain barrier - tight junctions between capillary endothelial cells โ regulates passage of substances from blood to CNS interstitial fluid microglia - phagocytes, protective functions oligodendrocytes - myelinate axons in CNS ependymal cells - produce CSF C. Spinal Cord and Spinal Nerves 1. Spinal Cord a. gray matter - nuclei, contain cell bodies, dendrites, axon terminals โ integration dorsal (posterior) horn ventral (anterior) horn b. white matter - tracts, contain myelinated axons โ conduct APs over longer distances ascending tracts: sensory information descending tracts: motor information 2. Spinal Nerves a. dorsal root - incoming axons of sensory neurons (cell bodies in dorsal root ganglia) b. ventral root - outgoing axons of motor neurons (cell bodies in ventral horn) - 31 pairs (C1-8, T1-12, L1-5, S1-5, Co1) 3. Spinal Reflexes Reflex arc: sensory receptor โ sensory neuron โ integrating effector (muscle) โ motor neuron โ center monosynaptic reflex (e.g., muscle spindle stretch reflex) polysynaptic reflexes (e.g., withdrawal reflex and crossed extensor reflex) D. The Brain Brain Stem = Medulla, Pons and Midbrain - transition from spinal cord to higher brain regions - sensory and motor tracts pass through - origins of cranial nerves reticular formation - network of neurons involved in arousal of cerebral cortex (sleep/wake) 1. Medulla Oblongata - ascending (somatosensory) tracts convey sensory information to higher brain areas - descending (corticospinal) tracts carry motor signals, cross over in pyramids of the medulla - respiratory and cardiovascular control centers - other involuntary control centers (swallowing, vomiting) Docsity.com
