10-21-14 Autonomics Flashcards
Afferent neurons handle
sensory input
Afferent neurons trigger responses at the ______ ____
Spinal cord
Efferent neurons handle
motor outflow
Where is a reflex processed in the ANS?
The brain, not the spinal cord as in the CNS
In an autonomic reflex arc, the ANS takes the place of the ____ in the CNS reflex arc
alpha motorneuron
Where specifically do reflexes occur in the ANS?
Lower brain levels - Brainstem, hypothalamus
Some of the things the ANS controls
Smooth muscle action, blood flow, glandular secretions
The ANS is the efferent arm of our reflexes that controls the ______
viscera
Where do outflowing ANS neurons synapse?
Outside of the CNS
How many neurons are usually involved in innervating an effector cell in the ANS?
2 neurons in series
The first neuron in the ANS is called the _____
pre-ganglionic neuron
Why does the Pre-ganglionic neuron start in the CNS?
It gets its message from the brain
Where does the pre-ganglionic neuron in the ANS end up?
a ganglion
What is a ganglion?
A cluster of cell bodies
What happens at a ganglion in regards to ANS neurons?
the pre-ganglionic neuron synapses with the post-ganglionic neuron
Where does the post-ganglionic neuron end up?
the target organ
What are the two divisions of the ANS
Parasympathetic and Sympathetic
What are the 3 ways to differentiate between the PS & S divisions of ANS?
- Where the pre-ganglionic fibers leave the CNS
- Location of ganglion
- Lengths of pre- and post-ganglionic axons
Describe the fiber lengths in parasympathetic nervous system
Preganglionic fibers - long
Postganglionic axon - short
Where is the ganglia in the PS nervous system?
On or near the target organ
Where does the Parasympathetic pre-ganglionic axon leave the CNS?
Cranial and Sacral regions
Where do sympathetic pre-ganglionic axons leave the CNS?
Thoracic and lumbar region
Where is the ganglia located in the sympathetic nervous system?
Sympathetic chain, just outside the vertebral column
Describe the relationship between the pre- and post-ganglionic fibers in the sympathetic nervous system
Short pre-ganglionic fibers
Long post-ganglionic axon
The NT released by the pre-ganglionic fibers in sympathetic and parasympathetic nervous systems is the same, what is it? What is the receptor subtype?
Acetylcholine
Nicotinic cholinergic
What facilitates an AP (very basic)
opening of Na+ channels
In the PS nervous system what does influx of Na through the nAchR cause?
EPSP -> AP
Excitatory Post-Synaptic Potential
What does the post-ganglionic axon release in the PS NS?
acetylcholine
Describe the uniqueness of the synapses in the ANS
en passant
Mailman throwing your mail into your yard, instead of placing it in your mailbox
Where are the vesicles located in the ANS?
the varicosities of the efferent synapse
Is the NT released by ANS nerves concentrated or diffuse?
diffuse, distributed to a broad area
The synapses of the ANS are not “protected”. What are the implications of this?
The metabolites are detectable in the blood.
What type of receptor interacts with the post-ganglionic axon of the PS NS?
muscarinic
What are the G-protein coupled muscarinic receptors?
M2
M3
M4
Where is M2 active and what does it do
Cardiac
Decreases cAMP->increased K+efflux (inhibits)
Where are M3 receptors found, and what do they do?
They do the same thing as M2, but are not restricted to Cardiac
Where are M4 glands found, and what do they do?
- Glands
- Increase IP3/DAG -> Increased Ca2+
What is the NT released by the post-ganglionic fiber in the sympathetic nervous system?
Norepinephrine
Why are there so many types of a-adrenergic receptors?
Having different receptors allows the NE & ACh to do elicit different responses in different tissues
A-adrenergic receptor affinity for NE vs. Epinephrine
higher for NE
What do the 1a, 1b, and 1d a-adrenergic receptors do in the sympathetic nervous system?
increase IP3 and DAG -> decreased K+ efflux
What do the 2a,2b,2c a-adrenergic receptors do?
Decrease cAMP -> decreased Ca2+ and Increased K+
The three different subtypes of B-adrenergic all do the same thing, what do they do?
Increase cAMP
Compare the affinity of B-adrenergic receptors for Epinephrine and NE
Higher affinity for epinephrine
What is the sympathetic NT released at the post-ganglionic neuron?
Noradrenaline AKA norepinephrine
What type of receptors on the target organ interact with the sympathetic nervous system
Alpha or beta adrenergic receptors
(nor)epinephrine=____________
(nor)adrenaline
What produces epinephrine?
chromaffin cells of the adrenal medulla
The adrenal medulla is the equivalent of a __________ ________
sympathetic ganglion
Where does the ANS specifically synapse in the adrenal medulla?
chromaffin cells
What NT acting at what receptor type tells the adrenal medulla to secrete epinephrine?
ACh acting at nicotinic receptors
epinephrine is released in the blood by chromaffin cells, what else is also released?
dopamine and norepinephrine (both are required to synthesize epinephrine)
General conditions of the body when parasympathetic system is more active
- sufficient O2
- Low HR
- Low BP
- Blood to intestines
Sympathetic system activation allows
Increased O2 intake
More O2 to muscles
Less blood to GI
Radial muscle of iris response to sympathetic activation is
- contraction -> dilation of pupil
- allows more light in
What receptor subtype is active in the Iris during sympathetic action
a-adrenergic
How is the ciliary muscle of the eye lens acted upon during sympathetic tone?
- Relaxes, which flattens the lens
- Enhances focus on far objects
What receptor subtype is acted upon in the ciliary muscle during sympathetic innervation?
B2-adrenergic
What receptors are signalled in the heart by the sympathetic nervous system during fight or flight?
B1 &B2-adrenergic receptors
What do the B1 and B2 adrenergic receptors do when activated by the sympathetic ns in the heart?
Increase HR
Increase strength of contraction
Fight or flight response in a-adrenergic receptors of blood vessels
vasoconstriction
Fight or flight response in b-adrenergic receptors of blood vessels
vasodilation
Most arteries and veins have both a, and b-adrenergic receptors. Why is this important?
Vasodilation - directs blood to skeletal muscle
Vasoconstriction - shunts blood away from GI system to skeletal muscles
Why do some arterial systems only have a-adrenergic receptors?
Skin and mucosa- limit bleeding during flight or fight
Salivary glands - dry mouth
Brain - can choose whether its alpha receptors are active or not
What type of receptors are used in fight or flight response in bronchial smooth muscles?
B2 receptors
Bronchodilation (makes it easier to get O2 in)
What does a1 activation do in bronchial glands?
decreases secretion
What does b2 activation result in in bronchial glands?
Humidifies air in lungs by increasing secretions
a1 and b activation in GI system during fight or flight results in?
decreased motility
a1 activation in GI sphincters results in _____
contraction
a2 activation in GI results in ______ _____
decreased secretions
How to increase energy in fight or flight
a1 and b2 receptors in liver
a1, b1, b3 receptors in adipose tissue
a1 and b2 action in liver during fight or flight
increased glycogenolysis (breaking glucose molecules off of glycogen one at a time)
action of a1, b1, and b3 receptors in adipose tissue during fight or flight
increased lipolysis - (FFAs)
action of b2 adrenergics on heart
increase strength and rate of contraction (more blood)
Action of a-adrenergics on vasculature
vasoconstrict and send blood away
Action of b-adrenergics on vasculature
dilate and increase blood flow (more blood)
Action of B2-adrenergics on lungs
Bronchodilation (more air)
Increased secretions (humidify more air)
Parasympathetic action on the heart and pupil
Heart - decreases HR, not contractile strength though
Pupil - constriction via relaxation of radial muscle
Rest and digest state of ciliary muscle/lens
contraction, round for near vision
Rest and digest state for vasculature
vasodilation
Rest and digest action in GI
increased motility
increased secretions
relaxed sphincters
State of bronchial smooth muscle during rest and digest
contractions/gland secretion
What is the relationship between PS and S nervous systems during normal conditions?
a state of equilibrium. A lack of equilibrium is NOT healthy.
What is the brains role in the relationship between sympathetic and parasympathetic tone?
The brain controls the fluctuations/”outflow” so that each organ gets the proper balance of PS & S tone.
