Compare Somatic and Autonomic Nervous Systems

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6 Terms

1
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SNS: Functional Organization

  • controlled/percieved consciously

  • motor + sensory

    • motor = initiation from CNS → somatic motor neuron → somatic effector (skm)

      • voluntary involve cerebrum

      • reflexive involve brainstem/spinal cord

    • sensory = detection of stimuli by sensory receptors of special senses (vision, hearing, equilibrium, smell, taste) tactile receptors of skin and mucous membranes, proprioceptors

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ANS: Functional Organization

  • not conscious, motor only (autonomic motor or visceral motor system)

  • signals from CNS to hear, smooth muscle, glands

  • responds to visceral sensory inputs (from blood vessels)

    • sensory neurons not not part of ANS

  • functions to maintain homeostasis

  • hypothalamus in control

    • divided into sympathetic and parasympathetic

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SNS: Lower Motor Neuron

  • single cell from CNS to skm fibers

    • cell body in brainstem/spinal cord, exits to skm

    • myelinated + fat = fast propagation of signals

    • releases ACh from synaptic knob to excite

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ANS: Lower Motor Neuron

  • 2 neurons from CNS to cardia, smooth + glands

  • First is preganglionic:

    • cell body in brainstem/sc

    • thin, myelinated axon to autonomic ganglion in peripheral nervous system

    • release ACh from synaptic knob to excite second motor neuron

  • Second is ganglionic (postganglionic) neuron

    • cell body in autonomic ganglion

    • very thin, unmyelinated axon projects to cardiac muscle, smooth muscle, or glands

    • releases ACh or NC from synaptic knob to excite or inhibit

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Advantages ANS has with 2 neurons

  • neural convergence: many preganglionic synapsing on 1 ganglionic

  • neural divergence: 1 preganglionic synapsing on many ganglionic

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CNS control of ANS

  • ANS regulated by parts brain/sc

  • Hypothalamus: nuclei controlling both divisions

    • emotional ANS processes (fight-or-flight)

    • influenced by areas of cortex, thalamus, limbic system

  • Brainstem: nuclei mediate visceral reflexes

    • maintain blood pressure, heart rate, respiration

  • Spinal cord: some ANS reflexes

    • defecation and urination controlled by PNS