LEC: NERVOUS SYSTEM

• sympathetic postganglionic fibers (adrenergic fibers) release norepinephrine
• parasympathetic postganglionic fibers (cholinergic fibers) release acetylcholine
• When both divisions serve the same organ they cause antagonistic effects due to the different neurotransmitters released
• preganglionic axons of both divisions release acetylcholine
• Parasympathetic division allows us to “unwind” and conserve energy.
• Sympathetic division mobilizes the body during extreme situations.
• The ANS has two arms that serve the same organs but cause opposite effects that counterbalance each other’s activities.
• Somatic nervous system – the cell bodies are inside the CNS, and their axons extend all the way up to the skeletal muscles they serve
• Autonomic nervous system – has a chain of two motor neurons
• Its axon (preganglionic axon) leaves the CNS to synapse with the second motor neuron in a ganglion outside the CNS
• The axon of this second neuron (post ganglionic axon) then extends to the organ it serves
• The Autonomic Nervous System is the motor subdivision of the PNS that controls body activities automatically
• Autonomic Nervous System - Composed of group of neurons that regulate cardiac muscle, smooth muscles and the glands
• Cervical - C1 - c5
• Brachial - C5-C8 and T1
• Important nerves of Brachial :

  • axillary
  • radial
  • median
  • musculocutaneous
  • ulnar
• Axillary - deltoid muscle and skin of shoulder; muscles and skin of superior thorax
• Radial - triceps and extensor muscles of the forearm; skin of posterior upper limb
• Median - flexor muscles and skin of forearm and some muscles of the hand
• Musculocutaneous - flexor muscles of arm; skin of lateral forearm
• Ulnar - some flexor muscles of forearm; wrist and many hand muscles; skin of hand
• Wristdrop - inability to extend hand at wrist
• Clawhand - inability to spread fingers apart
• Foot drop - inability to dorsiflex foot
• Lumbar - L1-L4
• Sacral - L4-L5 and S1-S4
• Important nerves of lumbar:

  • femoral
  • obturator
• Important nerves of sacral:

  • Sciatic
  • Superior and Inferior gluteal
• Sciatic - largest nerve in body, splits to common fibular and tibial nerves just above the knee
• Sciatica - inability to extend hip and flex knee
• Shuffling gait - inability to plantar flex and invert foot
• The ventral rami of all other spinal nerves form plexuses
• Plexuses - which serve the motor and sensory needs of the limbs
• The ventral rami of spinal nerves T1 to T12 form the intercostal nerves
• Intercostal Nerves - which supply the muscles between the ribs and the skin and muscles of the anterior and lateral trunk
• The smaller dorsal rami serve the skin and muscles of the posterior body trunk
• The 31 pairs of spinal nerves are formed by the combination of ventral and dorsal roots of the spinal cord
• Mixed nerves – carry both sensory and motor fibers.
• Motor/efferent nerves – carry only motor fibers.
• Sensory/afferent nerves – carry impulses towards the CNS.