Ch 60 ANS and Adrenal Medulla Flashcards
Briefly, what is the pathway of SNS nerves to the adrenal medulla?
preganglionic sns fibers go without synapsing from the intermediolateral horn cells of the SC, through sympathetic chains, through splanchnic nerves, to the modified neuronal cells secreting epi/norepi into the blood
What are the two main SNS abdominal ganglia?
Celiac and hypogastric
Which structures have cholinergic postganglionic SNS fibers? (the exceptions)
Sweat glands, piloerector muscles, and a few blood vessels
What is secreted by all preganglionic nerve fibers?
Acetylcholine
Where are the transmitter vesicles of acetylcholine or norepinephrine synthesized and stored?
The variscosities of many PSNS and all SNS fibers
Which ion causes terminals to release their neurotransmitters?
Calcium diffusion into nerve terminal or variscosities
How is acetylcholine synthesized and destroyed, and how long does it last?
Made when choline acetyl-transferase catalyzes the combination of acetyl-coA and choline. It persists a few seconds. Then it’s split into acetate and choline by acetylcholinesterase in local connective tissue
Briefly, how is norepinephrine synthesized?
Starts in adrenergic nerve terminal endings, and completes in secretory vesicles.
Tyrosine –> Dopa. Dopa –> dopamine.
Dopamine is transported to the vesicles, and then hydroxlyated to NorEpi. Some norepi is methylated into epi
By which 3 ways is norEpi removed from the secretory site?
- Active transport to reuptake into nerve terminals (predominant)
- Diffusion away
- Destruction by monoamine oxidase or catechol-o-methly transferase
How long is norepi or epi active?
10 to 30 seconds. takes minutes to ‘fade away’
Where are muscarinic vs nicotinic receptors found in the body?
Muscarinic: on all effector cells stimulated by postganglionic cholinergic neurons
Nicotinic: At the autonomic ganglia at synapses between pre and postganglionic neurons, or at neuromuscular junctions
*in both PSNS and SNS
Stimulation of adrenergic Beta2 receptors results in ______
Vasodilation (including coronaries), intestinal relaxation, uterus relaxation, bronchodilation, calorigenesis, glycogenolysis, and bladder wall relaxation
Stimulation of adrenergic Beta1 receptors results in ______
Cardioacceleration, increased myocardial strength, lipolysis
Stimulation of adrenergic Beta3 receptors results in ______
thermogenesis
Stimulation of adrenergic alpha receptors results in ______…and which is specifically alpha2?
Vasoconstriction, iris dilation, intestinal relaxation, intestinal sphincter contraction, pilomotor contraction, bladder sphincter contraction, and
alpha 2 = inhibiting neurotransmitter release
How does SNS stimulation dictate changes in systemic arterioles?
adrenergic alpha: constrict in the muscle
Adren B2 and cholinergic: dilate muscle vessels
Constricts abdominal visceral vessels
How do the effects of epinephrine and norepinephrine on blood pressure differ?
Norepinephrine: increases TPR and elevates arterial pressure.
Epinephrine: raises arterial pressure to a lesser extent but increases cardiac output
Briefly, what are the three main differences between epinephrine and norepinephrine?
- Epi stimulates beta receptors more strongly
- Norepinephrine has a stronger effect on blood vessel constriction
- Epi has 5-10x the metabolic effect as norepi
How does the PSNS vs SNS control the pupillary opening?
SNS: contracts meridonal fibers of the iris to dilate the pupil
PSNS: contracts the circular muscle of the iris to constrict the pupil
How does the SNS vs PSNS control the shape of the lens?
PSNS: contracts the ciliary muscle to release tension on the ligaments and allow the lens to become convex, so the eye focuses on objects near at hand
SNS: Slight relaxation of the ciliary muscle to flatten the lens further and see far objects more clearly
What is meant by SNS or PSNS “tone”? What is its purpose
Tone allows a single nervous system to both increase and decrease the activity of a stimulated organ … so a decrease OR increase in activity of the SNS or PSNS can enact a change.
What is denervation supersensitivity?
An enhanced reaction of an organ or tissue to hormonal stimulation after the organ has been denervated, to enable that organ/tissue to respond to SNS or PSNS stimulation. Thought to occur due to receptor upregulation in the postsynaptic membrane
Briefly, what is the baroreceptor reflex?
When stretch receptors located in the walls of the internal carotid arteries and the aortic arch are stretched by high pressure, signals transmit to the brainstem to inhibit SNS impulses to the heart and blood vessels and excite the PSNS.
Result: arterial pressure falls (normalize)
What is mass discharge? How does this occur?
When large portions of the SNS discharge at the same time.
1. Increased arterial pressure
2. Increased blood flow to active muscles and decreased to abdominal viscera
3. Increased cellular metabolic rate
4. Increased blood glucose [ ]
5. Increased glycolysis
6. Increased muscle strength
7. Increased mental activity
8. Increased rate of blood coagulation
Which receptors do the following drugs stimulate?
Phenylephrine, albuterol, isoproterenol?
Phenylephrine: alpha
Albuterol: Beta2
Isoproterenol: beta
What do ephedrine, tyramine, and amphetamine have in common?
They all cause the release of NorEpi from storage vesicles in the SNS nerve endings
What receptors do methacholine and pilocarpine act upon?
muscarinic cholinergic receptors
What do neostigmine, pyridostigmine, and ambenonium have in common?
They all inhibit acetylcholinesterase to potentiate the effect of acetylcholine at the NMJ
What do atropine, homatropine, and scopolamine have in common?
They block the action of acetylcholine at the muscarinic type of cholinergic effector organs
