Somatic Nervous System Overview

Somatic Nervous System

• Component of the peripheral nervous system
• Responsible for voluntary control of skeletal muscles
• Responsible for reflex actions via skeletal muscles
• Includes functions we consciously control, like arm and leg movements
• Consists of 43 different segments of nerves
  • 12 pairs of cranial nerves
  • 31 pairs of spinal nerves

Somatic Nervous System Components

• Dorsal roots: carry sensory information (afferent fibers)
• Ventral roots: carry motor information (efferent fibers)
• Dorsal root ganglia: location of sensory neuron cell bodies
• Interneurons: connect sensory and motor neurons
• Mechanoreceptors: detect mechanical stimuli

Somatic Nervous System- Reflex Arc

• Refers to neural pathways responsible for involuntary movements
• A monoynaptic reflex arc involves two neurons and one synapse

Autonomic Nervous System

• Component of the peripheral nervous system
• Regulates involuntary body functions
  • Includes heart rate, blood pressure, respiration, digestion, and sexual arousal

Autonomic Nervous System Divisions

• Sympathetic: "fight or flight" response, prepares body for stress/emergency situations
• Parasympathetic: "rest and digest" response, conserves and restores body energy
• Enteric: regulates gut reflexes

Autonomic Nervous System- Further Details

• Distributed throughout the central and peripheral nervous system
• Consists of two parts: sympathetic nervous system and parasympathetic nervous system

Divisions of Autonomic Nervous System

• Sympathetic Nervous system
  • Emerges from T1 to L2, of the spinal cord
  • Primarily uses norepinephrine as a neurotransmitter
  • Preganglionic fibers are relatively short
  • Postganglionic fibers are relatively long
• Parasympathetic Nervous system
  • Originates from the brain stem and sacral segments of the spinal cord
  • Primarily uses acetylcholine as a neurotransmitter
  • Preganglionic fibers are relatively long
  • Postganglionic fibers are relatively short

Function of the Sympathetic System

• Prepares the body to deal with emergency situations
• Includes vasomotor, pilomotor, and secretory fibers affecting sweat glands and visceral pain

Function of the Parasympathetic System

• Conserves and restores energy
• Includes the functions involving the regulation of GI processes
• Independent to other parts of CNS

Comparison of Somatic, Sympathetic and Parasympathetic Nervous Systems

• Somatic nervous system:
  • One neuron for a pathway.
  • Heavily myelinated
  • Primarily to skeletal muscles
• Sympathetic nervous system:
  • Two neurons for a pathway.
  • Lightly myelinated preganglionic; unmyelinated postganglionic
  • Affects cardiac, smooth muscle, and glands
• Parasympathetic nervous system:
  • Two neurons for a pathway
  • Lightly myelinated preganglionic and postganglionic
  • Affects cardiac, smooth muscle, and glands

Somatic vs Autonomic Nervous Systems

• Motor neuron cell bodies are located diffrently
• The motor endings are different, and are not the same.

This quiz covers the key components and functions of the somatic nervous system, including its role in voluntary and reflex actions. Test your understanding of the structure and neural pathways that enable movement and sensory perception. It also touches briefly on the autonomic nervous system for context.