Nervous systems

Nervous systems

1. ANS

   • Autonomic nervous system
     • Organ supplied
       • Many
         • e.g. smooth and cardiac muscle
           • Glands
             • Adipose tissue
         • Dual innervation
           • PNS and SyNS
           • Antagonistic
           • Differences
             • Agonistic
               • Glands in the head e.g. salivary
             • Single innervation
               • Most blood vessels
                 • Except
                   • Blood vessels of the head and neck
                     • These have dual innervation
               • Sympathetic NS
                 • vasomotor tone
             • Same innervation - different response
               • Blood vessels
                 • Smooth muscle vs cardiac and skeletal
                   • C+Sk = beta receptors
                   • Smooth = alpha receptors
             • Dual innervation - dif muscles
               • Radial muscle of the eye - SnS
                 • Circular muscle of the eye - PNS
     • Distal most synapse
       • Outside CNS - in ganglia
     • Nerve fibres
       • Pre = myelinated
         • Post = unmyelinated
     • No. of neurones in efferent pathway
       • 2
     • Effects on target tissue
       • Excitatory or inhibitory
     • Transmitter
       • ACh / NA
         • Ach = mAChR
         • NA = alpha or beta
     • Function
       • Visceral functions
         • Movement in internal organs
         • Secretion
         • Control of metabolism
   • Sympathetic nervous system
     • Origin
       • Dorso-lumbar
         • T1 to L2
     • Function
       • Tackling stress and emergency
     • Distribution
       • Wide
     • Ganglia
       • Sympathetic trunk ganglion
       • Away from organs
     • Post ganglionic fibres
       • Long
         • Unmyelinated
     • Pre:post ratio
       • 1:20 or 1:100
     • Transmitter
       • Pre = Ach
       • Post: NA
       • EXCEPT
         • Post gan - Ach in Sweat glands
           • Adrenal medulla - only Pre
             • Ach acts on adrenal medulla
               • Adrenal medulla releases Na + Adrenaline
   • Parasympathetic nervous system
     • Origin
       • Cranio-Sacral
         • III, VII, IX, X
         • S2-S4
     • Function
       • Assimilation of food and conservation of energy
     • Distribution
       • Limited
     • Ganglia
       • On/close to organs
     • Post ganglionic fibres
       • Short
     • Pre:post ratio
       • 1:1 - 1:2
     • Transmitter
       • ACh
   • Enteric nervous system
     • Innervates the gut, pancreas and gallbladder
     • Parasympathetic
     • Has two plexi
       • Submucosal
         • Stomach and intestines only
         • Located between longitudinal muscle and submucosal
       • Myenteric
         • Full GIT
         • Located between longitudinal muscle and circular muscle
     • Short reflex - afferent, interneurones and efferent neurones
       • Interneurones
         • Excitatory
         • Inhibitory
       • Afferent (sensory)
         • Mechanoreceptors and chemoreceptors
       • Efferent
         • Inhibitory
         • Excitatory

2. SNS

   • Somatic nervous system
     • Organ supplied
       • Skeletal myscle
     • Distal most synpase
       • In CNS
     • Nerve fibers
       • Myelinated
     • Transmiter
       • ACh
         • nAChR
     • No. of neurones in efferent pathway
       • 1
     • Effects on target tissue
       • Exciatory
     • Function
       • Posture and movement

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