ANS Background and Parasympathetic Flashcards
Explain the branches nervous system?
Define ANS?
A branch of the peripheral nervous system innervating smooth muscle tissue, glands, organs whose activity is not under concious control.
Autonomous - independent, not under control of the brain
Parasympathetic and sympathetic neurones are classified based on their ____ and not based on ____?
Parasympathetic and sympathetic neurones are classified based on their origin from the CNS and not based on the transmitter they release.
Where the Parasympathetic Nerves originate from?
Originate from the medulla (cranial origin) and sacral (sacral origin). CRANIOSACRAL OUTFLOW
Where do Sympathetic Nerves originate from?
Originate from the thoracic and lumbar spinal cord - Thoracolubar Outlflow
What is a Ganglion?
A collection of neuronal bodies found in the voluntary and autonomic branches of the peripheral nervous system (PNS)
Explain the different neurotransmitters released by parasympathetic and sympathetic nerves?
Parasympathetic: Preganglionic nerves release Ach on Nicotinic Receptors on Postganglionic nerves which release Ach on muscarinic receptors in tissues.
Sympathetic: Preganglionic nerves release Ach on Nicotinic Receptors on Postganglionic nerves which release norepinephrine on Andregenic receptors.
What are all the sites where Ach is released?
Where are all the sites where NE is released?
Postganglionic Sympathetic Nerves.
Sympathetic fibres innervating sweat glands in the palms (adregenic sweating).
Why dont we use muscarinic and ganglionic blockers?
Both of them are not specific. Ganglionic Blockers will block parasympathetic and sympathetic fibres. Muscarinic Blockers will block all isoforms of the receptors present in many different tissues.
Both of these will have many various side effects because non specific.
What are 3 different type of specific blocker drugs.
a1B - Alpha 1 Blocker - Aplha 1 found in majority blood vessels and responsible for vasoconstriction. **Drug leads to vasodilation. Useful to treat hypertension and lower blood pressure **
B1B - Beta 1 Blocker - Found in Heart - Increases heart rate and contractility. **Drug leads to lower heart rate and blood pressure - prevents strokes. **
B2B - Beta 2 Blocker - Found in Bronchial Smooth Muscle - Beta 2 Agonist leads to Bronchodilation. Drug has opposite effect.
Very Specific Drugs
What does Non Selective - Beta B do and what is the adverse effect?
Most Widely Used Class of Drugs.
Blocks all Beta Receptors.
Non selective beta blockers cause bronchoconstriction as the adverse effect when treating a cardiovasular condition.
The adrenal medulla releases ____(80%) and ____ (20%) into the circulation when stimulated by preganglionic ____.
The adrenal medulla releases epinephrine (80%) and norepinephrine (20%) into the cirulation when stimulated by preganglionic sympathetic nerves.
What is Phaeochromocytoma?
A tumor of the adrenal medulla that releases large amounts of E and NE into the cirulation. Cause increased blood pressure and heart rate. (Tachycardia and very high blood pressure).
What is Ach synthesized from?
Choline and Acetyl coenyme A.
What causes the breaking down of Ach in the synapse and what is the effect of the inhibition of this?
Acetylcholinesterase - Enzyme
Inhibition leads to very high Ach concentration in the synapse - Cholinergic Crisis
What does botulinum toxin do?
Blocks Ach release - Causes skeletal Muscle paralysis
Does not affet the synthesis but rather it affets the release of ACh
What are catecholamines?
Catechol (benzene with two hydroxyl) + Amine Side Chain
What are NE, E, and Dopamine synthesized from?
How is NE removed from the synapse?
Taking back up into the presynaptic nerve terminal to terminate its action though a specific uptake protein (Protein Uptake 1).
What is the clinical significance of NE uptake blockers?
**Increase NE concentration in the synapse.
**
Uptake blockers useful for conditions with deficiency (depression). Can use serotonin, dopamine blockers to increase concentration and treat depression.
What are the different type of cholinergic receptors?
Explain the different subtypes of Nicotinic Receptors.
Nicotinic Receptors are sodium ion channels.
What are the functions of the Parasympathetic Nervous System(Rest and Digest)?
In each organ
Heart: Rate and Contractility Down
Blood Vessels: Relaxed Blood Vessels, Normal Blood Pressure. (Remember Blood vessels have limited have parasympathetic innervation, more lack of sympathetic ativity that causes this; paraympathetic causes vasodilation in GI and erectile tissue.)
Urinary Bladder: Normal Contractions, Contributes to the relaxation of the sphincter.
GIT including mouth: More Secretions (Saliva etc), and activates peristalsis. Excess Parasympathetic Activity leads to diarrhea, etc.
Eyes: Focus on near objects, constriction of the pupils.
What are the functions of the sympathetic nervous system(fight or flight)?
In each organ
Heart: Increased rate and Contractility
Blood Vessels: Vasoconstriction and increased BP. However skeletal, pulmonary, and coronary vessels dilate. (Muscle and lungs need more oxygen and energy.)
Kidneys: Increased Renin Secretion (Helps Vasoconstriction)
Urinary Bladder: Contraction inhibited and constricted sphincter (Urine Retention).
Lungs/Bronchi: Relaxed Bronchial Muscle - More Oxygen
GIT: Reduced GIT secretions and Peristalsis
Liver: Increased glycogenolysis (More Blood Glucose)
Eyes: Dilated Pupils, Focus on distant obect
What is dominant tone?
The dominant tone in an organ means that the branch of ANS innervating that organ is dominant or more active most of the time than the other.
Drugs especially ____ affecting the system which is ____ will have a more ____ in that organ.
Drugs especially antagonists affecting the system which is dominant will have a more noticeable effect in that organ.
What are 2 types of drugs that can mimick parasympathetic effects and what is their mode of action?
- Muscarinic Receptor Agonists (Direct Acting)
- Acetylcholinesterase Inhibitors (Indirect Acting)
What are 2 types of drugs that can block parasympathetic effects?
- Muscarinic Receptor Antagonists
- Skeletal Neuromuscular junction blockers
In most organs - Parasympathetic Block resembles sympathetic stimulation