6 & 7 - Autonomic System Flashcards
Viscera by visceral sensors
is a kind of sensory input to the ANS. An example is change in blood pressure elicits the ________.
baroreceptor reflex
Other than visceral sensors, the other 2 types of sensor that input to the ANS are _____ and ______.
- Surface of the body by somatic sensors
○ Fall in ambient temperature sensed by peripheral/ cutaneous thermoreceptors triggers the contraction of arrector pilli muscle to raise hair and constriction of cutaneous blood vessels
- External environment by special sensors
Light affects the constriction and dilation of pupil
Considering the generation of ANS, there are 2 control pathways namely:
Somatic control pathways and Autonomic control pathways
What are the 4 differences of somatic and autonomic pathways? Why ANS is relatively slow to to somatic motor control?
- No. of synapses
Somatic: Monosynaptic
Autonomic: Disynaptic - Fiber type
Somatic: Myelinated type A fibers
Autonomic: Autonomic preganglionic neurons are small myelinated type B fibers; postganglionic: unmyelinated C fibers
(overall: fibers of ANS are less myelinated) - Neurotransmitter:
Somatic: Ach
Autonomic: Sympathetic: NE;
Parasympathetic: Acetylcholine - Effect on effectors:
Somatic: always excitatory
Autonomic: depends on the receptors, can be excitatory or inhibitory
Place the discrete effect of the 3 controls in descending order.
Parasympathetic ANS,
Sympathetic ANS,
Somatic motor control
Discrete effect: Somatic motor control > Parasympathetic ANS > Sympathetic ANS
What are the differences between sympathetic and parasympathetic divisions?
- Length of preganglionic neuron
S: Short
PS: Long - Length of postganglionic neuron
S: long
PS: short - Location of ganglia
S: lying close to the spinal cord (distant from effector organs)
PS: at the effector organs - Effect
S: less discrete (allow divergence to other places)
PS: more discrete
Motor nerve endings are specialized into ________, and are matched by post-synaptic specialization into ____________ where receptors for neurotransmitters are concentrated and only expressed in this cell surface area of the effector cell
synaptic knobs;
motor end plates
In _______ innervation, preganglionic neurons group their cell bodies into the _____________. (paired structure forming 2 sympathetic chains)
sympathetic;
sympathetic trunk ganglia
Sympathetic: After entering the sympathetic trunk, the preganglionic neuron may synapse with __________ at the same spinal level
Or send collaterals up/down the trunk to synapse at other spinal levels
-> widespread and less discrete effect
postganglionic neurons
Sympathetic: Preganglionic neurons synpase with postganglionic neurons located in prevertebral/ collateral ganglia (not paired), if they didn’t synapse after passing the sympathetic trunk
As not chained,-> more ___________ effect
(e.g. coeliac, aorticorenal, superior mesenteric, infereior mesenteric)
discrete
Sympathetic: Preganglionic neurons synapse with __________ located in adrenal medulla, which secrete hormones: ________ 80% and _______ 20%
-> widespread and prolonged effect
chromaffin cells;
adrenaline;
noradrenaline
Parasympathetic:
Preganglionic neurons originate from the brainstem in the nuclei of the _________.
cranial nerves (3,7,9,10)
Craniosacral division of ANS
Run for a long distance to meet postganglionic neurons in terminal ganglia
-> More ________ effect
localised
Adrenal medulla, adipose tissue, kidney, most blood vessels, sweat gland, piloerector muscle are only innervated by the _________.
Sympathetic nerves
fight or flight
stressful situations
Lacrimal gland, ciliary muscle are only innervated by the _____________.
Parasympathetic nerves
rest and digest (conserve energy)
NE and EP are synthesized from the amino acid ______as the precursor.
At adrenal medulla, chromaffin cells express additional enzyme (PNMT) to convert _____ to ____ as the major secretory product
tyrosine;
noradrenaline to adrenaline
Liver receives both sympathetic and parasympathetic nerve innervation
_________: stimulation of glucose production
Sympathetic
*Parasympathetic: anatomically but not functionally, if any, stimulation of glycogenesis and inhibition of gluconeogenesis
All autonomic preganglionic neurons release ______ onto _____________receptors.
acetylcholine;
cholinergic nicotinic receptors
Most postganglionic parasympathetic neurons secrete _______ onto ___________receptors.
acetylcholine;
cholinergic nicotinic receptors
Most postganglionic sympathetic neurons secrete ___________ onto _________ receptors (metabotropic receptor) (exceptions: sweat glands)
noradrenaline;
adrenergic
______ receptors are ionotropic receptors > faster action;
_____ receptors are metabotropic receptors >slower action
Nicotinic cholinergic ;
Muscarinic cholinergic
Muscarinic:
Adenylate cyclase >
catalyse ATP > cAMP
> PK > Ca2+ channels open/close
depends on Gi/Gq/Gs protein being stimulated
○ In ANS, neuronal type of nicotinic receptors are involved in generating ______________.
In somatic nervous system, muscle type of nicotinic receptors are involved in generating ___________ in skeletal muscle
EPSP (excitatory postsynaptic potential) ;
end plate potential (EPP)
Muscarinic receptor (Odd) (metabotropic) :
Stimulates muscle ________ (bronchial, intestinal) by binding to _________ that is linked to activation of phospholipase C, generating _____________ , and hence Ca2+ release from intracellular store
contraction;
G protein-coupled receptor (GPCR);
inositol triphosphate (IP3)
Muscarinic receptor (even)(metabotropic) ;
Example: Ach bind to M2 receptor activates ________ to inhibit adenylate cyclase, leading to fall in cAMP, reduced protein kinase A activity and closure L-type Ca2+ channel due to decreased channel protein phosphorylation
The ________ subunit of GK protein activates K+ channel to ________ the cell membrane.
Gi protein;
beta y;
hyperpolarize
