Biology XI: 21 Neural control & coordination(1 Human Neural System

Human Neural System: Structure and Function of Neuron Human Neural System Has 2 parts: Central neural system (CNS)Peripheral neural system (PNS) CNS: Brain and Spinal Cord PNS: Nerves associated with CNS (Afferent fibres and efferent fibres) Afferent fibres: Transmit impulses from tissues to CNS Efferent fibres: Transmit impulses from CNS to tissues Structural and functional unit of neural system: Neuron Neuron Classification of neurons based on the number of axons and dendrites: Multipolar neurons Bipolar neurons Unipolar neurons 1 axon and 2 or more dendrites 1 axon and 1 dendrite 1 axon and no dendrite Found in the cerebral cortex Found in the retina During the embryonic stage Two types of axons: Myelinated Non-Myelinated Enveloped with Schwann cells, forming a myelin sheath around the axon Also enveloped by Schwann cells, but they do not form a myelin sheath around the axon Nodes of Ranvier present Nodes of Ranvier absent Found in the spinal and cranial nerves Found in the autonomous and somatic neural systems Nodes of Ranvier: Gaps between two adjacent myelin sheaths Structure of Neuron: