Autonomic Nervous System II Flashcards
T/F All organs innervated by the parasympathetic nervous system are also innervated by the sympathetic nervous system but not vice versa.
T. That is some organs receive only sympathetic innervation
“Fight or flight” and “rest and digest refer to what nervous systems respectively?
- Sympathetic Nervous System
- Parasympathetic Nervous System
Describe tone.
The ANS is always working neither sympathetic or parasympathetic are purely “ON” or “OFF”. The degree of function is tone.
How is the ANS related to behavior?
- The ANS through visceral reactions molds and determines the quality and nature of behavioral reactions.
- Conditioning and learning- emotional and nostalgic components as well as autonomic rxns. are stored in memory.
What are the sympathetic and parasympathetic effects on the heart?
S: an increase in HR, and myocardial contractility
PS: decrease in HR, and myocardial contractility
Which vagus nerve primarily innervates SA and AV node respectively?
Right vagus nerve: primarily innervate the SA-node
Left vagus nerve: primarily innervate the AV-node
What are the sympathetic and parasympathetic effects on the arterioles?
S: Although complex, vasoconstriction is generally the dominant sympathetic response.
PS: blood vessels are generally not innervated by the PS nervous system. But engorgement of sexual erectile tissue mediated by PS vasodilation.
NOTE: Point (PS) and Shoot (S)
What are the sympathetic and parasympathetic effects on the veins?
S: induces vasoconstriction.
NOTE: 70% of the blood is in veins, regulation of venous capacity is an important determinant of the distribution of systemic blood volume
What are the sympathetic and parasympathetic effects on the bronchi?
S: sparse innervation that cause them to dilate (But mostly thought to dilate due to circulating epinephrine).
PS: its post-ganglionic innervation, denser than that of the sympathetic nervous system, causes constriction of the bronchioles.
What are the sympathetic and parasympathetic effects on the abdominal viscera?
S: inhibits secretion of the digestive juices, reduces the strength of peristalsis, promote vasoconstriction
PS:secretion of digestive juices, increases motility of the stomach, intestine, and colon. Vagus innervates the proximal portion of colon while the sacral segments of the spinal cord innervate the distal portion of the colon.
What are the sympathetic and parasympathetic effects on the pelvic viscera (lower bowel and urinary bladder)?
Similar to abdominal viscera but voluntary conscious decisions are more important than for abdominal activity.
S: inhibits bladder emptying by stimulating B2-adrenergic receptors in the bladder body (promoting S mm relaxation) and stimulating alpha1-adrenergic receptors of the urethra (causes urethra restriction).
PS: excitatory signals to the S mm walls of the bladder (promote contraction and bladder emptying) and the PS induced release of NO results in urethral Sm cell relaxation.
What are the sympathetic and parasympathetic effects on the eye?
S: stimulation cause dilation of the pupil but pupil size is primarily controlled by the PS.
PS: stimulation causes the ciliary mm to contract, producing pupil constriction.
What are the sympathetic and parasympathetic effects on the skin?
S: sympathatic reflexes promote sweating (sudomotor reflexes).
Despite the sweat gland being innervated by sympathetic, post-ganglionic fibers secrete ACh.
What are the sympathetic and parasympathetic effects on the salivary glands?
S: small amount of viscous saliva rich in solid. vasoconstriction reduce blood flow to the glands.
PS: copious and watery salivation.
What are the sympathetic and parasympathetic effects on the lacrimal glands?
S: constricts blood vessels that supply the lacrimal glands, reduce secretion of tear fluid.
PS: promotes secretion.
NOTE: tears provide lubrication for the eyelids and help wash away noxious agents.
What are the sympathetic and parasympathetic effects on the kidney?
S: innervation of kidney is exclusively sympathetic. Through its vasoconstrictor effects it regulates glomerular filtration rate, renin secretion from juxtaglomerular cells and tubular reabsorption.
What are the sympathetic and parasympathetic effects on the liver?
S: causes the liver to make glucose available via glycogenolysis, and gluconeogenesis.
The transmitters of the ANS exert their effects on target organs via______
membrane receptors
List two characteristics of the receptors on effector cells.
1) They are innervated by post-ganglionic fibers.
2) Receptor activation causes either membrane permeability changes with ion movt. and/or the generation of second messengers.
In sympathetic nervous system E, or NE exert their action via ________receptors.
Adrenergic receptors found on diverse tissues of the body as heart, smooth mm, GI tissue, liver and brain.
What are the 2 types of adrenergic receptors?
Alpha-Adrenergic receptors: activation causes contractions of S mm.
Beta-Adrenergic receptors: activation causes relaxation of S mm
NOTE: gut is an exception since NE stimulation of either alpha or beta receptors causes relaxation.
These receptors are in turn divided: B1, B2, B3, & alpha 1, alpha 2.
The superfamily of adrenergic receptors and the Muscarinic receptors are often described as:
“Seven-transmembrane domain receptors” or “ seven-helix receptors”
Understand the difference of how neurotransmitters and hormones act on the effector organ.
Figure 12 pp 63 of the week 3 notes.
Although all types of B-receptors have the same mechanism of action, their pharmacologies are different. What is the potency of E, NE to B1 and B2 receptors?
B1 and B2 prefer E than NE.
E >NE (somewhat more potent than NE) @ B1 receptors.
E»»>NE (E much more potent than NE) @ B2-receptors.
Draw the signal cascade induced by the activation of B receptors.
pp 65 of week 3 notes.
What are the subunits of PKA?
It has 2 regulatory (R) units and two catalytic (C) units
What happens to the PKA subunits when intracellular cAMP increases?
-cAMP binds to R and the PKA complex dissociates into an R2 dimer and 2 free C subunits.
-The free C subunits are active, catalyzing the transfer of the terminal phosphate of ATP to a target protein.
NOTE: look @ FIGURE on pp. 66
Give 2 examples of B-adrenergic stimulations.
1) Leads to phosphorylation of Ca channels in ventricular fibers of the heart. Phosphorylation increases the open time duration of these channels , greater Ca influx, greater contraction
2) Causes relaxation of S mm by phsphorylating and inactivating myosin-light chain kinase (MLCK). Relaxation of S mm results in vasodialtion.
What is the importance of the coupling of cell surface receptors to adenylate cyclase activation?
1) Transduction
2) Amplification
FIGURE 15 pp. 67
What are the subunits of G-proteins?
-are heterotrimeric composed of Alpha, beta and gamma subunits.
Which subunit is usually determines the effector to which the G protein couples?
Alpha subunit largely determines the effector to which the G protein couples and whether the effector is activated or inhibited. Ex: alpha s stimulates adenylate cyclase..
NOTE: in some cases beta and gamma subunits are more important than the alpha subunit in controlling effector ptns.
What happens to the subunits when the receptors is activated by an agonist?
GDP-GTP exchange takes place on the alpha subunit and the G-ptn dissociates into an active alpha subunit and beta-gamma complex.
Explain the importance of G ptn in understanding how cholera results in diarrhea.
Cholera toxin from bacteria binds to alpha subunit and makes it impossible for it to dissociate from adenylyl cyclase. Cyclase is chronically activated, cAMP pathologically elevated. In intestine, cAMP promotes Cl and Na efflux. Water movt. into the intestinal lumen osmotically follows, causing massive diarrhea.
Figure: understand the function of G-protein.
Figure 16 pp. 69
How do the alpha 2 receptors couple to adenylyl cyclase?
Via an inhibitory alpha-i subunit of Gi result in a decrease in cAMP.
Is NE or E more potent for alpha 1 or alpha 2 receptors?
NE is more potent for both receptors.
Mention some examples of alpha-2 adrenergic stimulation?
1) activation opposes action of B-adrenergic receptors and leads to dephosphorylation of MLCK. MLCK is activated and S mm contracts causing vasoconstriction.
2) Presynaptic alpha-2 adrenergic receptors on post-ganglionic sympathetic fibers. Release of NE-inhibition of presynaptic adenylyl cyclase causes dephosphorylation of Ca channels-leads to shorter open time durations-smaller influx of Ca into the presynaptic terminal. Auto-inhibitory feedback causes the inhibition of NE release.
How does alpha 1 receptor activation affect intracellular Ca?
It increases intracellular Ca. G ptn stimulated-alpha q results in phospholipase C release-and phospholipase C catalyzes the hydrolysis of a phospholipid (phosphoinositol 4,5 phosphate, PIP2) resulting in inositol 1,4,5 phosphate (IP3) and diacylglyceride (DAG).
FIGURE 17A pp. 70
What happens to IP3 and DAG?
- IP3 diffuses to the ER and stimulate Ca release
- DAG remains membrane bound and activates PKC-phosphorylation of target ptns
Give an example of alpha-1 adrenergic receptor activation.
In vascular S mm cell, promotes rise in intracellular Ca which activates MLCK (a CaM-kinase), catalyze phosphorylation of myosin light chain and result in contraction of S mm, vasoconstriction
Acetylcholine exerts its effects via membrane bound receptors known as____
Cholinergic receptors
What are the 2 types of cholinergic receptors?
1) Nicotinic-occur on the post-ganglionic neurons in the synapses of the autonomic ganglia and @ skeletal muscle neuromuscular junction (in the Somatic Nervous System not the ANS)
- ACh exert its function by opening cation selective channels=cell depolarization
2) Muscarinic- occur in organs innervated by the parasympathetic postganglionic endings
What are the agonist and antagonist of the nicotinic and muscarinic receptors?
Nicotinic: agonist nicotine and antagonist curare.
Muscarinic: agonist muscarine and antagonist atropine.
There are 5 different subtypes of muscarinic receptors. What results in their stimulation?
M1, M3, M5- rise in intracellular Ca via IP3 system
M2, and M4- causes cAMP to be lowered
NOTE: M2 found in cardiac muscle the acute response is opening K selective channels (Parasympathetic stimulation slows HR).
