AP 2 2.5: The Autonomic Nervous System Flashcards
Autonomic Nervous System
The autonomic nervous system, a part of the peripheral nervous system, is made up of motor neurons that control the internal organs automatically and usually without need for conscious intervention. The sensory neurons that come from the internal organs allow us to feel internal pain. The cell bodies for these sensory neurons are in dorsal-root ganglia, along with the cell bodies of somatic sensory neurons.
Preganglionic axon
The following terminology will be used for the ANS nervous system
A motor neuron cell body is located in the spinal cord or brain. The axon synapses with a second motor neuron located in an autonomic ganglion outside the spinal cord.
Postganglionic axon
The following terminology will be used for the ANS nervous system
After synapsing in a in an autonomic ganglion, the axon of the ganglionic motor neuron synapses on an effector organ in the peripheral nervous system.
There are two divisions of the autonomic system
the sympathetic and parasympathetic systems. Both systems function automatically (usually subconsciously) in an involuntary manner. These two divisions cause essentially opposite effects on the same visceral organ. In general, if one division stimulates, the other inhibits.
sympathetic system
The sympathetic system (Figure 2.48) is also called the thoracolumbar division because this division contains preganglionic fibers from the thoracic and upper lumbar segments of the spinal cord, in the lateral gray horns. The sympathetic system is especially important during emergency situations and is associated with the “fight or flight” response. When in immediate danger, active muscles require a steady, increased supply of glucose and oxygen for muscular contraction. The sympathetic system accelerates the heartbeat, dilates the bronchi, and increases the breathing rate. The impacts of the sympathetic system supply the increased need for oxygen throughout body. At the same time, the sympathetic system causes the liver to deliver more glucose for the body’s increased metabolic needs. Sympathetic activation inhibits the digestive tract since digestion is not an immediate necessity when in danger or under attack. The primary neurotransmitter utilized by the sympathetic system at the target organs is norepinephrine (NE)
norepinephrine (NE)
The primary neurotransmitter utilized by the sympathetic system at the target organs is norepinephrine (NE). If norepinephrine is the neurotransmitter released, then the neuron is called adrenergic.
Sympathetic trunk ganglia
The sympathetic nervous system contains the following ganglia
Sympathetic trunk ganglia or lateral ganglia: located on both sides of the spinal cord, these contain the ganglia for the sympathetic nervous system that controls the effector organs in the trunk, head, and limbs.
Celiac ganglion
The sympathetic nervous system contains the following ganglia
Celiac ganglion: largest of the ganglia, these ganglia innervate the digestive tract.
Superiomesenteric ganglion
The sympathetic nervous system contains the following ganglia
Superiomesenteric ganglion: innervates the small intestine and parts of the large intestine
Inferior mesenteric ganglion
The sympathetic nervous system contains the following ganglia
Inferior mesenteric ganglion: innervates the large intestine, kidneys, bladder, and sex organs.
Ciliary ganglion
The parasympathetic nervous system contains the following ganglia
Ciliary ganglion: Associated with cranial nerve III, this targets the intrinsic eye muscles, which change the pupil and lens.
parasympathetic system
The parasympathetic system (Figure 2.49) is also known as the craniosacral division because the preganglionic fibers originate in the brainstem and sacral division of the spinal cord. The parasympathetic division tends to have more specific targets than the widespread sympathetic division. The parasympathetic system is also sometimes called the “housekeeper system” because it promotes all the internal responses associated with a relaxed state. Parasympathetic stimulation causes the pupil of the eye to constrict and helps the lenses of the eyes to focus on nearby objects. It promotes the digestion of food through stimulation of the smooth muscles of the GI tract and secretion of digestive glands to assist digestion, such as the salivary glands. The parasympathetic system also acts to slow the heart rate. The neurotransmitter utilized by the all parasympathetic system neurons is acetylcholine (ACh).
acetylcholine (ACh)
The neurotransmitter utilized by the all parasympathetic system neurons is acetylcholine (ACh). If a neuron releases acetylcholine, it is called cholinergic.
Pterygopalatine ganglion & Submandibular ganglion
The parasympathetic nervous system contains the following ganglia
Pterygopalatine ganglion & Submandibular ganglion: Associated with CN VII, the target organs are for tear production, nasal glands, and salivary glands.
Otic ganglion:
The parasympathetic nervous system contains the following ganglia
Otic ganglion: Associated with CN IX, the target glands are the parotid glands.
