Lecture 1 Central nervous system DJ.pdf

Central Autonomic Nervous System REGULATION OF BIOLOGICAL PROCESS Hormones Neurotransmitters Histamine Prostaglandins Organization Spinal Cord Spinal ganglia Posterior horn (Efferent Motor) (Afferent Sensory) Anterior horn Auronomic nervous system Somatic nervous system Sympathetic and Parasympathti...

Central Autonomic Nervous System REGULATION OF BIOLOGICAL PROCESS Hormones Neurotransmitters Histamine Prostaglandins Organization Spinal Cord Spinal ganglia Posterior horn (Efferent Motor) (Afferent Sensory) Anterior horn Auronomic nervous system Somatic nervous system Sympathetic and Parasympathtic Cervical Thoraccic Lumbar Sacral AUTONOMIC NERVOUS SYSTEM Typically, a two-neuron structure is found in the autonomic nervous system The preganglionic neuron has its cell body in the central nervous system and its axon in an autonomic ganglion where it synapses with one or more postganglionic neurons The preganglionic neuron originates in the CNS with its cell body in the lateral horn of the gray matter of the spinal cord or in the brainstem AUTONOMIC NERVOUS SYSTEM SYMPATHETIC PARASYMPATHETIC Preganlionic neuron in thoraccic and lumbar spinal cord Preganlionic neuron in brain stem ( CN III , VII, IX, X) and sacral spinal cord (cranio-sacral division) Anatomically designed to produce response on an organ basis (thoraco-lumbar division) Anatomically designed to produce widespread physiological activity Neurotransmitters Sympathetic neuron = norepinephrine Cholinergic neuron = acetylcholine Neurotransmission 1 Preganglionic synapse 2 Postganglionic synapse 3 Somatic motor end plates Post Ganglionic Innervation One way transmission Promotes a response in postsynaptic target Effector Receptors Innervation Most effector organs receive dual innervation Both working in opposition (balanced) the one exerting the greater function will prevail Specific effects 1-Bloods vessels Mainly innervated by sympathetic system, maintain smooth muscle tone 2 Heart Sympathetic system Positive chronotropic (heart rate) Positive inotropic (force of contraction) Positive dromotropic (conductivity) Parasympathetic system Negative inotropic Negative dronotropic 3 Cardiovascular reflex Mainly due to stretch receptors (carotid body) effects on cardiovsacular center at Medulla oblongata 4- Eye Pupil Lens) Sympathetic system (mydriasis) Dilator pupillae (radial fibers) Parasympatheic system (miosis) Constrictor pupillae (circular fibers At rest the suspensory ligaments of cilliary body exerts tension flattening the lens Under parasympathetic stimuli the cilliary body contracts decreasing tension on the lens thickening the lens due to elasticity accommodating for near vision 5 Lung Bronchial tree is dually innervated Sympathetic system Bronchodilation Parasympatehtic system Bronchoconstriction 6 Gastrointestinal tract Dual effects but act on local neural regulators Enkephalins Substance P Vasoactive intestinal peptide 7- Salivary glands Dual stimulation produce secretion with different characteristics Sympathetic stimuli Thick and mucinous Parasympathetic stimuli Watery 8- Adrenal medulla Behaves as a sympathetic ganglion producing primarily epinephrine, then norerpinephrine