System organization - PPM system types (Somatic, Autonomic & Enteric) and Reflex arc types

• The PNS consists of all nervous tissue outside of the CNS. • It is divided into three functional components: • Somatic nervous system (SNS) • Autonomic nervous system (ANS) • Enteric nervous system (ENS) • The SNS consists of: • Sensory neurons from skeletal muscles • Motor neurons to skeletal muscles • Stimulation of skeletal muscles, by the motor portion of the SNS is voluntary. • The ANS consists of: • Sensory neurons from visceral organs • Motor neurons to cardiac and smooth muscle tissues, glands and adipose tissue • Stimulation of visceral effectors by the motor portion of ANS is involuntary. • The motor portion of the ANS has two divisions: • Sympathetic - prepares the body to "fight-or-flight" • Parasympathetic -prepares the body to "rest-or-digest" • Most effectors are stimulated by both divisions. • The ENS consists of: • Sensory neurons from digestive organs • Motor neurons to smooth muscle and glands of the digestive organs • Stimulation of digestive effectors by the motor portion of the ENS is involuntary. Reflex arc components • Clusters of neurons in the CNS act as control centers for all of the nervous pathways in the body. • Reflex arcs are nervous pathways that result in rapid and automatic changes in the actions of effectors. • The components of most reflex arcs are: • Receptor • Sensory neuron • Association neuron • Motor neuron • Effector • Somatic reflex arcs stimulate skeletal muscle tissue. • Autonomic and enteric reflex arcs stimulate: • Smooth muscle • Cardiac muscle • Endocrine and exocrine glands • Adipose tissue

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