Organization of Nervous system Structural and functional unite of the nervous system The Neuron Cells of nervous systems The main cells of the nervous system is nerve cells (Neuron) which is the structural unite of the Nervous system All neurons have same basic structure, a cell body with a number of dendrites and one long axon. There is another supporting cells and it is non excitable cells collectively called Neuroglia Anatomic and Functional Categories of Neurons Non-excitable cells of the nervous system Cell body 11.5 mm Node of Ranvier is a section of unmyelinated axon membrane between two Schwann cells. Schwann cell nucleus is pushed to outside of myelin sheath. Axon Myelin consists of multiple layers of cell membrane. (b) Each Schwann cell forms myelin around a small segment of one axon. Schwann Cells Classification of sensory receptors According to 1. Mechanoreceptors 2.Thermoreceptors 3.Chemoreceptors 4.Electromagnetic receptors 5.Pain receptors 1.Exteroreceptors 2.Interoreceptors 3.Proprioceptors Type of stimuli detected Location Synapse Synaptic transmission Neurotransmitters are chemicals that travel across the synapse and allow communication between neurons. The reflex arc and its steps:- Is the pathway of the reflex action Reflexes Innate, genetically determined Acquired, learned Visceral contraction of smooth, cardiac muscle and glands Somatic, control skeletal muscle Contraction, stretch reflex Development Spinal, Processed in the sp cord Cranial, Processed in the brain Processing sites Response Monosynaptic, one synapse Polysynaptic, multiple synapse Complexity Types of reflex Monosynaptic reflex Polysynaptic reflex https://encrypted- tbn0.gstatic.com/images?q=tbn:ANd 9GcSltQJkQsUSIcE2QmHIQqSbvB A2UZsnf2STBgHgiQkfS-6C4fkI Brain Regions (1) (2) (3) Functional area of the cerebral cortex Spinal cord Functions connect brain to most body parts. involved in spinal reflex actions, First, it carry sensory information through the afferent nerves from the sensory receptors throughout the body to the brain. It also carries information from the brain through efferent fibers to the muscles and glands. Second, it coordinates reflexes without the involvement of the brain. Thoracic segments contain centers that regulate respiratory muscles It contain somatic centers controlling stretch and withdrawal reflex. Thoracic and lumber segments contain centers which regulate several sympathetic function as sweating, vasomotor, and ejaculation Sacral segments contain centers regulate parasympathetic functions as defecation, urination and erection It is a relay for most ascending sensory and descending motor impulses passing in tracts Sensory and motor spinal tracts Autonomic Nervous System (ANS) Control Involuntary or visceral nervous system Regulates the activity of: Cardiac Muscle (Heart) Smooth Muscle ( In Hollow Organs) Blood Vessels Digestive System Bronchioles Sphincters Glands Adrenal Digestive glands 1.Receptor 2.Afferent 3.Interneuron 4.Efferent preganglionic 5.Efferent post ganglionic 6.Effector organ which is cardiac muscle or viscera Role of the Autonomic Division in Homeostasis Figure 11-1 Sympathetic integration Adrenal medulla secrete epinephrine and nor epinephrine Skeletal muscle blood vessels dilate bringing more blood to skeletal muscle to improve all sk M.proparties Thus preparing the body for Fight or Flight Increase heart rate and strength of contraction Dilate respiratory passage Increase blood clotting Effect of sympathetic and para sympathetic on the body