BIOL125 Lecture Notes - Lecture 12: Perineurium, Epineurium, Vagus Nerve
Peripheral Nervous System
• 3.28. The Peripheral Nervous System (PNS)
o 3.28.1. the two major pathways - sensory and motor
• Sensory
▪ Dorsal column tract
▪ Spinothalamic tract
▪ Spinocerebellar tract
• Motor
▪ Corticospinal tract
o 3.28.2. the somatic and autonomic systems
• Somatic (voluntary)
▪ Spinal nerves
▪ Cranial nerves
• Autonomic (involuntary)
▪ Sympathetic
▪ Parasympathetic
• Transduces physical or chemical stimuli from both within the body and from
the external environment to sensory information via receptors
• Conveys the sensory information to the CNS via afferent pathways
• Conveys motor signals from the CNS to skeletal and smooth muscle via
efferent pathways
• Converts motor signal to chemical signals at synapses on target tissues
• Somatic sensory
▪ Conveys information from the periphery
▪ Collective description for all sensations
• Special senses (Seeing, hearing, smelling and tasting)
• Touch
• Proprioception
• Pain, temperature
▪ The output of the somatic nervous system is exclusively to skeletal
muscle
▪ Thus the output of the somatic nervous system results in movement
• 3.29. Protection of spinal nerves
o Nerves
• Bundles of neurons, connective tissue and blood vessels which are present
only in the PNS
• Nerves carry motor information to muscle and other cells
• Mediate sensory modalities to the spinal cord or brainstem
• Spinal nerves send/receive information between spinal cord and the body
• Spinal nerves mediate non-special senses
• Cranial nerves send/receive information between the brain and the structures
of the head and neck
• Cranial nerves mediate many special senses and some special senses
• Spinal
▪ 31 pairs mixed nerves
• 8 cervical (C1-C8)
• 12 thoracic (T1-T12)
• 5 lumbar (L1-L5)
• 5 sacral (S1-S5)
• 1 coccygeal
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▪ Structure
• Each side of spinal column, spinal (dorsal and ventral) roots join
to form a spinal nerve
• Mixed nerves carry both sensory and motor fibres
▪ Spinal roots
• Anterior/ventral root contains axons of motor neurons
• Posterior/dorsal root contains axons of sensory neurons
• Dorsal root has ganglia - contain cell bodies of sensory neurons
• Combination of these roots creates spinal cord
▪ Spinal nerves entering the spinal cord
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Document Summary
The peripheral nervous system (pns: 3. 28. 1. the two major pathways - sensory and motor. Spinocerebellar tract: motor, corticospinal tract, 3. 28. 2. the somatic and autonomic systems. Somatic sensory: conveys information from the periphery, collective description for all sensations. Special senses (seeing, hearing, smelling and tasting: touch, proprioception, pain, temperature, the output of the somatic nervous system is exclusively to skeletal muscle, thus the output of the somatic nervous system results in movement, 3. 29. Spinal nerves send/receive information between spinal cord and the body. Spinal nerves mediate non-special senses of the head and neck: cranial nerves mediate many special senses and some special senses. Spinal: 31 pairs mixed nerves, 8 cervical (c1-c8, 12 thoracic (t1-t12, 5 lumbar (l1-l5, 5 sacral (s1-s5, 1 coccygeal. Structure: each side of spinal column, spinal (dorsal and ventral) roots join to form a spinal nerve, mixed nerves carry both sensory and motor fibres.