ch14.pdf - Chapter 14 Autonomic Nervous System An Overview...

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1 An Overview Our nervous system is broken down into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS is composed of the brain and the spinal cord; the PNS is composed of the cranial nerves (total of 12) and the spinal nerves (total of 31). Our nervous system takes care of coordinating voluntary as well as involuntary actions by sending signals (through nerve cells known as neurons in an electrochemical fashion and in a large majority of cases through nerve fibers known as axons) from every aspect of our body (like electrical wires throughout our house) as well as receiving feedback. Excitatory as well as inhibitory information is moved from nerve cell to nerve cell joining together through synapses (junction points of two nerve cells) and moving impulses from nerve cell to nerve cell with the help of neurotransmitters. We know that we not only can move our fingers, but we can also use them for sensing our surroundings. Nerve impulses can be transmitted from the periphery to the center and vice versa, from the CNS to the PNS and from the PNS to the CNS. We can classify nerve impulses heading from the PNS toward the CNS as sensory. These impulses travel along a sensory or afferent neuronal net- work. Impulses originating in the CNS heading toward the PNS are motor impulses that travel along a motor or efferent neuronal network. These neuronal structures within the CNS and PNS carry both sensory and motor information, like a two-way highway. Within the PNS, motor impulses are further divided into somatic motor (mediating voluntary movements moving impulses from the CNS to skeletal muscles) and visceral motor or better known as the autonomic nervous system (taking care of the visceral or organ motor activities at an unconscious level conducting impulses from the CNS to smooth and cardiac muscles as well as glands). The autonomic nervous system or ANS will be subdivided into the sym- pathetic nervous system (coordinating emergency situations preparing our system for excitation or the well-known “fight or flight” response helping the body prepare for a crisis or stress) and the parasympathetic nervous system (in charge during resting conditions, keeping balance by promoting rest and relaxation or the well-known “rest and digest response”). Sympathetic Nervous System The sympathetic nervous system is a part of the autonomic nervous system. It prepares the body for excitation, crisis, or stress, but the sympathetic sys- tem also works in an ongoing manner essential for our day-to-day functioning. Chapter 14: Autonomic Nervous System
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2 Motor network: Descending pathways (upper motor neurons) Through efferent or motor nerves (away from the CNS) 12 pairs of cranial nerves 31 pairs of spinal nerves Autonomic nervous system controls visceral or organ motor activities at an unconscious level. For example, coordinating respiratory, urinary, cardiovascular, digestive, reproductiveorgans.
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  • Fall '18
  • sympathetic trunk, Collateral ganglia

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