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
what can the length of the axon be used to distinguish?
sympathetic vs parasympathetic divison
which type of fibers are myelinated?
pre-ganglionic and somatic fibers → speed of transmission is higher here
which fibers are unmyelinated?
post-ganglionic fibers
which pre-vertebral ganglia are involved in some heart disorders?
cardiac plexus
which pre-vertebral ganglia induces the immediate KO of a fighter?
celiac ganglion
in general what nerves are important for homeostasis of the body?
splanchnic
what is the ratio of ganglionic neurons / somatic neurons in the body?
50:1
what routes are shared with the axons of the pre-ganglionic motoneurons?
same routes used by voluntary motoneurons
in what four ways can pre-ganglionic motoneurons make synapses?
- with ganglionic motoneurons in parallel
- more than one ganglionic motoneuron located “upstairs” or “downstairs”
- a motoneuron found in the pre-vertebral ganglia (splanchnic nerves)
- with the adrenal medulla do modulate its functionality
what is the cervical ganglia important for?
regulation of the salivary glands, eyes, and heart
what are the liver, stomach, spleen, and digestive tract regulated by?
mesenteric and celiac ganglia
where are the two different motor neurons of the parasympathetic division located?
one group of pre-ganglionic parasympathetic motor neurons located in the anterior part of the CNS and the other group of pre-ganglionic parasympathetic motor neurons located in the sacral segment of the spinal cord
we do not have any pre-vertebral or paravertebral chain or ganglia for this system
where is the ganglia receiving the signal in the parasympathetic system typically located?
not in close contact with the spinal cord bit inside the organs → often called intramural ganglia
what is one of the key division of the pre-ganglionic parasympathetic division?
Edinger-Westphal nucleus
where do the parasympathetic pre-ganglionic motoneurons organize themselves?
in tight contact with the voluntary motoneurons → they are organized in the brain in specific nuclei that are not placed in the very same positions as the sympathetic system - at least the ones in the brainstem
what can the Edinger-Westphal nucleus innervate?
the ocular motor nerve causing miosis
what are the superior and inferior salutatory nuclei fundamental for?
the salivary secretion and for tear production
what the pre-ganglionic parasympathetic motor neurons in the so called medulla fundamental for?
regulation of the intestines
what does the vagus nerve (X) control?
the bronchi, heart, stomach, small intestine
what nerve are the eyes regulated by?
voluntary nerve III and the pre-ganglionic parasympathetic motor neurons are running in tight contact with nerve III
what is the vagus nerve (X) important for?
the regulation of the stomach and digestion → it is a voluntary nerve that also contains pre-ganglionic parasympathetic axons that travel along the voluntary part
what are the pre-ganglionic parasympathetic motor neurons in the sacral portion of the spinal cord that enter into contact with specific plea important for?
regulation of the intestines, bladder, and genitals
what does the cranial outflow of the parasympathetic system involve?
the ciliary ganglion (in the eye and regulates pupil contraction)
what is the function of the facial nerve and the glossopharyngeal nerve?
production of tears and saliva
what do the parasympathetic axons of the vagus nerve control?
the heart, liver, lungs, gallbladder, and pancreas
describe the cell morphology of the sympathetic ganglionic cells:
usually have dense dentridic arborization and therefore can receive multiple signals
describe the cell morphology of he parasympathetic ganglionic cells:
few or sometimes no dendrites and therefore are innervated by only one or a few pre-ganglionic axons
what is a unique characteristic of ganglionic ANS motor neurons when they come into contact with smooth muscle?
there is no classical synaptic organization, but there are “bubbles” along the length, and from these bubbles we have the release of neurotransmitters
a single ganglionic moron neuron can induce the spread of neurotransmitters for several hundred microns regulating MANY cells instead of just one
describe the specificity of the ganglionic motor neuron pre and post synaptic terminal:
specificity is very low
describe the sympathetic system of the ANS:
well-organized with chairs of paravertebral and pre vertebral ganglia
where are the ganglions of the parasympathetic division in close contact with?
the stomach
name four effects deriving from the activation of the parasympathetic division?
- bronchoconstriction to prevent the lungs from taking in too much air
- increase in the mobility of the intestine to promote digestion
- urinary activity is increased
- increase in genital activity during rest
all pre-ganglionic motorn neurons in the ANS use what neurotransmitter?
they are cholinergic = release acetylcholine at the ganglionic level (both divisions)
what neurotransmitter do the sympathetic ganglionic neurons release?
norepinephrine
which neurotransmitter do the parasympathetic ganglionic neurons release?
acetylcholine at the target organic level
which receptor is always at the first synapse?
the neurotransmitter released is always acetylcholine so the receptors always a nicotinic acetylcholine receptor
which receptor is in the second synapse?
parasympathetic system released acetylcholine so the acetylcholine receptor is always Muscarinic
describe the promiscuity of the autonomic system:
they can co-released with amines molecules like neuropeptides as well as nitric oxide and CO2 → the same cells can release more than one neurotransmitter
describe nicotinic receptors:
inotropic receptor: nicotine is angonist of this receptor
acetylcholine is the classical ligand → this receptor is always expressed in the neuromuscular junction to allow muscle contraction and is used in neural communication
describe Muscarinic receptors:
G-protein coupled receptors that can be coupled to different G proteins that an cause different effects
muscarine is a potent agonist of these receptors
atropine is an antagonist of muscarinic receptors - how does atropine induce mydriasis?
atropine blocks the Muscarinic receptor that belongs to the parasympathetic branch opening the pupil (parasympathetic activation causes meiosis - antagonization causes the opposite)
what can a massive activation of the sympathetic system cause?
- piloerection: stimulate fight or flight
- increased blood pressure (faster O distribution)
- hyperglycemia
- inhibition of what is not necessary to fight (digestive, urinary etc.)
how does the pacinian sensor on the palm of the hand work?
the activation of the pacinian sensor induces the activation of our pseudo-unipolar neurons
this signal enters the dorsal horn of the spinal cord and is sent along a short axon not only to the somatic motor neurons but also to the pre-ganglionic motor neurons which then send the signal to the smooth muscles
what is the nucleus solitarius?
the region in which the visceral sensation arrives → you have feedback from raw or local reflexes that derive from the movement of your viscera
the sensory neurons “inform” the integrative center (nucleus solitarius) by sending signals deriving from the visceral movement
where does the nucleus solitarius send the signals?
sends the info to higher elements in the brain and this is why we feel pain
system is not designed to give specific localization of the damage only allows us to feel it
describe somatic sensing vs ANS sensing:
somatic sensing is very precise whereas ANS sensing is more “gross”
where does the gustatory sensation come from?
the nucleus of the solitary tract
where is the hit for visceral sensation?
in the nucleus of the solitary tract in the anterior part of the brain
where is the hit for visceral sensation?
in the nucleus of the solitary tract in the anterior part of the brain
