Lecture #12 Flashcards
what is the autonomic nervous system also described as?
the visceral nervous system
what are the two division of the autonomic nervous system?
ortho-sympathetic and parasympathetic
what does the over activation of the sympathetic system cause?
fight or flight
what does the over activation of the parasympathetic system cause?
rest and digest
how do the the sympathetic and parasympathetic division modulate organs?
by fighting each other → on one side the sympathetic system activates organs to fight or escape and the parasympathetic prepares organs to rest
what are the two characteristics of these homeostatic mechanisms?
- they are adaptive to the environment
- they have a memory (can be trained)
what is the most famous example where the parasympathetic and sympathetic systems converge?
the pupil - both division can regulate the level of restriction
what is an example of a system almost entirely controlled by the sympathetic system?
smooth muscle of the genitals
what are the 5 main features of the autonomic nervous system?
- lower motor neurons of the visceral motor system and the effector motoneurons are located outside the CNS (somatic system both motoneurons are located inside)
- organization of the ANS is simpler and not a classical plaque
- activation of the visceral motor system are coordinated by a large set of subcortical structures that are often in the ventral part of the forebrain
- neurotransmitters: visceral motor terminals release a variety of neurotransmitters including small molecules and complex neurotransmitters (promiscuity→ both at the same time)
- effects of the visceral motor activation can vary → ex: the nitric oxide in the genitalia has a different effect compared to the nitric oxide exerted in the brain
how does an over activation of the parasympathetic division affect the pupil?
causes mitosis (papillary construction) that causes less light to reach the retina
how does an over-activation of the sympathetic division affect the pupil?
causes mydriasis (dilation of the pupil) allowing a huge amount of light to reach the pupil and allowing you to see very well
how does an over activation of the sympathetic division affect the lungs?
causes bronchodialation in order to have oxygen to fight
how does an over activation of the parasympathetic division affect the lungs?
causes bronchial construction and the secretion of liquids
what is one key difference between the autonomic and voluntary nervous system?
the number of synapses formed
describe the amount of synapses in the voluntary system:
monosynaptic cascade: the first motoneuron receives a lot of information from the sensory cortex and generates a synapse with the secondary motoneuron (in the spinal cord)
there is one synapse → the one between the primary and secondary motoneuron `
describe the amount of synapses in the ANS:
disynaptic system: the first neuron of the cascade is in the basement of the brain and sends the first axon connecting to the first motoneuron belonging to the sympathetic or parasympathetic division → this motoneuron is still located in the CNS and is able to interact with a secondary motoneuron which is outside from the CNS and able to interact directly with the target organ
what is the difference in location regarding the last motoneuron in the somatic system compared to the ANS?
- last motoneuron is always in the CNS in the somatic system
- last motoneuron is always outside the CNS in the ANS
where are the voluntary motoneurons found compared to the autonomous motoneurons?
voluntary: ventral horn of the spinal cord
autonomous: far from this region
where are the voluntary motoneurons found compared to the autonomous motoneurons?
voluntary: ventral horn of the spinal cord
autonomous: far from this region
where are the neurons belonging to the orthosympathetic system found?
in the midline, in a region called the intermediolateral cortex observed from the thoracic vertebrae (T1) to the lumbar region (L3)
where are the paravertebral ganglia located?
close to the spinal cord but outside of it
describe the interaction between the paravertebral ganglia and the sympathetic / somatic nervous system:
sympathetic: will enter the ganglia
somatic: do not enter
what is another name for the paravertebral ganglia region?
white ramus - virtually all the axons are myelinated
what three interactions can axons make?
- interact with the second motoneuron of the system (grey ramus: part in which the axons of the second motoneuron re-enter in the main nerve - sends axons which are not myelinated)
- axons can turn toward the upper or lower ganglia instead of going toward the parallel ganglion
- axon can exit from the ganglion, travel for a specific distance, and then enter into another ganglion in the sympathetic system called the pre-vertebral ganglion
what are the ganglia parallel to the spinal cord called?
paravertebral ganglia
what are the ganglia in front of the spinal cord called?
pre-vertebral ganglia
where are the motoneurons of the voluntary system and primary system located in the spinal cord?
voluntary: ventral horn
sympathetic: midline
what is the fist motoneuron of the sympathetic system always called?
pre-ganglionic
in the classical voluntary motor neuron, where to the motoneurons send axons?
directly to the skeletal muscle
in the sympathetic system, there is ganglia flanking one side of the spinal cord which “mediates” the interaction with the target - what is in this ganglia?
a group of secondary motoneurons (ganglionic motoneurons) that receive information from the primary motoneurons and send axis to contact smooth muscle, vasculature, etc
how far do pre-ganglionic motoneurons travel?
a short distance: the paravertebral ganglia are close to the spinal cord
how far do ganglionic motoneurons travel?
a long distance because it needs to reach the target organs