The Autonomic Nervous System Concepts Flashcards
Contrast the structural and functional differences between the somatic and autonomic parts of the nervous system.
Somatic
Sensory info: DCML, ALS,
Integration: Sensory pathways reach the thalamic and up to the cortex
Motor Info: 1 motor neuron
- Motor neuron leaves from the anterior gray horn
Function: Move a skeletal muscle
Autonomic
Sensory info: Hitchhiking afferent sensory fibers
Integration:
- Medulla and pontine centers for breathing, heart rate, vomiting
- Hypothalamic nuclei for controlling ANS activity (anterior/posterior)
- Urination/defecation is handled at the sacral level of the spinal cord
Motor info: 2 motor neurons
- Motor neuron leaves from the lateral gray horn
Function: Move a smooth and cardiac muscle
Describe preganglionic and postganglionic neurons of the sympathetic autonomic nervous system. Contrast with preganglionic and postganglionic neurons of the parasympathetic division.
Sympathetic:
Preganglionic neurons are short
Postganglionuerons are long
Parasympathetic:
Preganglionic neurons are long
Postganglionic neurons are short
Contrast the ganglia used in both divisions of the ANS
Sympathetic: thoracolumbar
Superior cervical ganglion
Middle cervical ganglion
Interior cervical ganglion
Superior mesenteric ganglion
Inferior mesenteric gnalgion
Parasympathetic: craniosacral
Ciliary ganglion
Pterygopalatine ganglion
Submandibular ganglion
Otic ganglion
Understand how to identify a splanchnic nerve.
If it’s passing right through a trunk ganglia to a more lateral prevertebral ganglion, then it’s a splanchnic nerve
Explain the general concept of intramural ganglia.
They’re really close to the effectors, sometimes within the walls of the effectors themselves
Explain the relationship of the hypothalamus to the ANS, specifically which nuclei drive the sympathetic and parasympathetic arms.
Posterior hypothalamus nuclei drive the sympathetic arm of the ANS (fight/flight)
Anterior hypothalamus nuclei drive the parasympathetic arm of the ANS (rest/recover)
Discuss, in very general terms, the sensory input to both branches of the ANS, as well as some basic integrative centers for both branches, including medullary and pontine nuclei
Sympathetic:
- somatic and special sensory information
-integration occurs at pontine and medullary autonomic centers (breathing, heart rate, vomiting, sneezing, coughing)
- Sacral spinal cord level (micturition and defecation)
- Limbic system nuclei that introduce emotions and memory
Parasympathetic: (own “feed” of sensory information)
- Stretch receptors and chemoreceptors
- Integration occurs in the same place as sympathetic ANS, however limbic plays less role
Contrast the 2 major plexuses of the ENS, both structurally and functionally
Myenteric plexus
- Bigger of the two
- Superficial to the gut lumen
- located in muscularis
- Sit between the 2 main muscular layers of the GI tract (circular & longitudinal)
- May drive submucosasal
Function: integrate the GI tract sensation with smooth muscle movement
Submucosal plexus:
- Deeper than the myenteric relative to the gut lumen
- made of loose areolar and adipose connective tissue
- Found in the submucosa
- may not drive myenteric
Function: integrating GI tract sensation with glandular secretion
Describe the different ways to classify sensory receptors by structure.
First-order sensory neurons with free nerve endings
First-order sensory neurons with encapsulated nerve endings
Sensory receptor synapses with first-order sensory neuron
Contrast, both structurally and functionally, sensory receptors creating generator potentials with those creating receptor potentials
Chemoreceptors in free nerve endings and mechanoreceptors in encapsulated nerve endings create generator potentials. Free nerve endings pick up temperature and encapsulated nerve endings pick up light pressure. These are somatic/general/viscera types of senses
Chemoreceptors for taste in a special receptor create receptor potentials with a 2 part step. This is a special type of sense.
Contrast exteroceptors, interoceptors, visceroceptors, and proprioceptors
Extereoreceptors= integumentary, externally
Interceptors (Visceroreceptors) = internally, visceral
Proprioceptors= muscle spindles, joints
Contrast mechanoreceptors, chemoreceptors, osmoreceptors, nociceptors, and photoreceptors, focusing on where each can be found in the body and what each senses.
Mechanoreceptors= detect physical stimuli
Chemoreceptors= detects chemicals
Osmoreceptors= sense osmotic pressure of body fluids
Nociceptors= respond to painful stimuli from physical or chemical damage
Photoreceptors= detect light that strikes the retina of the eye
Compare the locations and functions of the direct and indirect (cortical and subcortical) motor pathways.
Direct: straight to the spinal from the cortex
- Corticospinal
Indirect: supplemental
- Rubrospinal= fine motor skills
- Tectospinal= visual and auditory reflex
- Vestibulospinal= balance
- Lateral and medial reticulospinal= posture
Consider where descending motor pathways may decussate
90% Medulla (Decussation of the Pyramids) or 10% segmental level
Explain how the basal nuclei and cerebellum contribute to the refinement of corticospinal motor plans.
Basal Nuclei= motor plans from the cerebral cortex descend through the caudate nuclei, to the putamen, to the Globus pallidus, relayed back through the thalamus, then back to the motor areas of the cortex for reevaluation
Cerebellum= cerebellum receives motor plans from the corticospinal tract. Via the pontocerebellar tract, running through the middle cerebellar peduncle into the cerebrum. The cerebrum is continually receiving proprioceptive information from very slowly adapting proprioceptors of the body and constantly comparing tensions with actual results. It sends edited feedback to the motor areas and corrected motor info to motor centers of the brain stem to drive indirect motor paths
Describe the neuronal components, locations, and functions of the posterior column-medial lemniscus pathway, the anterolateral pathway, the trigeminothalamic pathway, and the spinocerebellar pathway. Be able to trace (generally) each
from a peripheral exteroceptor
DCML:
- The gracile fasciculus handles sensations from the lower limbs/trunk
- The cuneate fasciculus handles sensations from the upper limbs/trunk/neck/posterior head
ALS:
- Decussation occurs at the segmental level
Trigeminothalamic:
- Instead of spinal nerves, cranial nerves act as 1st order neurons and carry sensory input to nuclei in the pons
- Decussates at pons or medulla then ascends to the thalamus
Spinocerebellar:
- ipsilateral
Consider where contralateral ascending sensory pathways may decussate
Segmental level or at pons or medulla
Identify the locations and functions of the different types of neurons in the somatic motor pathways, comparing upper and lower motor neurons
The upper motor neurons originate in the cerebral cortex and travel down to the brain stem or spinal cord, while the lower motor neurons begin in the spinal cord and go on to innervate muscles and glands throughout the body.
Describe how ENS reflex arcs can work without CNS input
You can sense, integrate, and respond entirely in the walls of the GI tract
Sensory: stretch and chemoreceptor
Integrate: in the myenteric plexus or submucosal plexus
Motor output: smooth muscles of myenteric plexus or secretory cells of submucosal plexus
Contrast 1st, 2nd, and 3rd order sensory neurons, paying attention to where they originate, where they terminate, where cell bodies may be found, and where they
1st=
Originate: exteroceptors and proprioceptors
Terminate: CNS
Cell bodies found: posterior root ganglion
2nd=
Originate: lower level of CNS (spinal cord or brainstem)
Terminate: thalamus
Decussate: somewhere low in the CNS (segmental level for ALS or medulla for DCML or either medulla or pons for the trigeminalthalamic path)
3rd=
Originate: thalamus (ventroposterior lateral for DCML & ALS and ventroposteior medial for trigeminothalamic)
Terminate: primary somatosensory cortex
