Introduction to the Autonomic Nervous System (ANS) PDF

Introduction to the Autonomic Nervous System (ANS) ۱. Components of ANS Central Nervous System (CNS) o Brain o Spinal Cord Peripheral Nervous System (PNS) o Sensory and Somatic Nervous System (Voluntary) o Autonomic Nervous System (Involu...

Introduction to the Autonomic Nervous System (ANS) ۱. Components of ANS Central Nervous System (CNS) o Brain o Spinal Cord Peripheral Nervous System (PNS) o Sensory and Somatic Nervous System (Voluntary) o Autonomic Nervous System (Involuntary) ۲. Anatomy of the PNS Somatic Nervous System (Voluntary) o Sensory neurons: Relay external stimuli to CNS o Motor neurons: Relay signals from CNS to muscles Autonomic Nervous System (Involuntary) o Controls:  Smooth muscles  Endocrine secretions  Heart rate  Metabolic processes (e.g., glucose utilization) o Subdivided into:  Parasympathetic Nervous System (PSNS)  Rest and Digest  Sympathetic Nervous System (SNS)  Fight or Flight  Enteric Nervous System (ENS)  Found within the walls of the GI tract ۳. Basic Components of the ANS Pre-Ganglionic Neurons (from CNS to ganglia) Post-Ganglionic Neurons (innervate target organs) ٤. Neurotransmitters in the ANS Peripheral Nervous System (PNS) o Acetylcholine (ACh) o Norepinephrine (NE) Central Nervous System (CNS) o ACh, NE, Dopamine, Serotonin, GABA, Glutamate, Histamine o Neuroactive peptides (e.g., Substance P) ٥. Parasympathetic Nervous System (PSNS) Function: o Pupil constriction (Miosis) o Bronchoconstriction o GI and urinary activities o Reduces heart rate The influence of the PSNS depends on the release of Ach Receptors : o Cholinergic Receptor (nicotinic or muscarinic) Drugs that Modulate PSNS: o Bethanechol: Enhances GI and urinary motility o Atropine: Antagonizes PSNS activity ٦. Sympathetic Nervous System (SNS) Function: o Pupil dilation (Mydriasis) o Bronchodilation o Increase in heart rate and contraction o Inhibition of GI activity and urination o Increase in blood sugar levels These actions are mediated via released norepinephrine and epinephrine Receptors : o Adrenergic Receptor ( alpa, beta )  Drugs that Modulate SNS: o Salbutamol: Beta-2 agonist, dilates bronchioles o Metoprolol: Beta-1 antagonist, reduces heart rate ۷. ANS Function Summary Sympathetic (Fight and Flight) Parasympathetic (Rest and Digest) Interaction between the two systems for overall regulation Blood vessels are innervated by sympathetic nerves but lack parasympathetic innervation. ۸. Pharmacology of the ANS Pre-Synaptic (Pre-Junctional) Actions: o Affect neurotransmitter synthesis, storage, release Post-Synaptic Actions: o Receptor activation/blocking, neurotransmitter metabolism