Autonomic Nervous System Physiology Flashcards
What are the two main divisions of the nervous system?
Central and Peripheral
What are the two main divisions of the peripheral nervous system?
Somatic and Autonomic
What are the two main divisions of the autonomic nervous system (ANS)?
Sympathetic and Parasympathetic
What does the somatic nervous sytem of the PNS control?
Voluntary movement by stimulating skeletal muscle
What does the autonomic nervous sytem (ANS) control?
- Regulation of the functions of the visceral/internal organs
- The ANS is involuntary
How are nerves in the somatic nervous system projected to the skeletal muscle?
Nerves project directly form the CNS to the skeletal muscle
How does the autonomic nervous system reach its target?
- Uses a two-neuron chain from the CNS to the effector site
- Preganglionic neuron synapses an autonomic ganglion outside the CNS and this post-ganglionic neuron innervates the effector site
Genneral effects of the sympathetic nervous system
- Increased heart rate
- Increased blood pressure
- Decreased digestion
- “Fight or flight”
General effects of the parasympathetic system?
- Decrease heart rate
- Decrease blood pressure
- Increase digestion
- “Rest and digest”
What type of receptors does Acetylcholine (ACh) bind to?
- Cholinergic receptors; 2 types:
- Nicotinic
- Muscarinic
- Different muscarinic subtypes: M1 to M5
What type of receptor does Norepinephrine (noradrenaline) bind to?
- Adrenergic receptors; 2 types:
- Alpha
- subtypes: alpha 1 and alpha 2
- Beta
- subtypes: beta 1, beta 2, and beta 3
- Alpha
What is the enteric nervous system?
How is it controlled?
- Independent part of the autonomous nervous system that controls GI function and secretions
- Sympathetic stimulation decreases its activity
- Parasympathetic stimulation increases its activity
Where do sympathetic preganglionic nerves originate?
What is their length?
- Originate in the thoracolumbar spinal cord (T1-L2/3)
- Short length
How do sympathetic preganglionic nerves travel?
Where do they synapse?
- They travel via the white rami
- They synapse in paravertebral (sympathetic chain close to the spinal cord) ganglia or in prevertebral ganglia
How do postganglionic sympathetic nerves leave the paravertebral ganglia?
What length are they?
- They leave the paravertebral ganglia via grey rami
- They are long in length
Where do parasympathetic preganglionic fibers originate?
What length are they?
- They originate in the brainstem and sacral spinal cord (craniosacral division)
- Cranial nerves III, VII, IX, and X
- S2-S4
- They are long in length
Where are parasympathetic ganglia located?
What length are the postganglionic parasympathetic nerves?
- They are located close to the effector site
- The postganglionic parasympathetic nerves are short
What neurotransmitter and receptors are used at both sympathetic and parasympathetic ganglionic synaptic sites?
- ACh acts on Nicotinic receptors for both sympathetic and parasympathetic systems
Postganglionic sympathetic nerves release ____ which acts on ____ receptors
Pastganglionic sympathetic nerves release norepinephrine which acts on adrenergic receptors
Note, adrenergic receptors have 5 subtypes:
a1, a2, b1, b2, b3
What are adrenergic receptors coupled to?
Specifically, what is coupled with the following?
a1
a2
and B(1-3)
Specific G-proteins
a1 –> Gq
a2 –> Gi
B –> Gs
Most sympathetic postganglionic nerves release ____
What are the exceptions to this?
Most sympathetic postganglionic nerves release norepinephrine
Except the sympathetic postganglionic nerves that innervate:
- Sweat glands which release acetylcholine
- Renal vascular smooth muscle which releases dopamine
-
Adrenal glands and releases acetylcholine which causes the adrenal glands to release epinephrine into the bloodstream
- Note: epinephrine acts as a hormomon when released into the blood and not a neurotransmitter
The adrenal medulla is a modified ____ ____, releasing ____ and ____ into the blood response to pregangionic sympathetic stimulation that uses cholinergic transission
The adrenal medulla is a modified sympathetic ganglion releasing epinephrine and norepinephrine into the blood response to pregangionic sympathetic stimulation that uses cholinergic transission
Postganglionic parasympathetic fibers release ____ which stimulates ____ receptors
Postganglionic parasympathetic fibers release ACh which stimulates muscarinic receptors
Note: muscarinic receptors have 5 subtypes
M1, M2, M3, M4, M5
Muscarinic receptors are coupled to specific ____
What subtype matches to each ____?
Muscarinic receptors are coupled to specific G-proteins
M1, M3, M5 –> Gq
M1 –> Gs
M2, M4 –> Gi
What does it mean that the sympathetic and parasympathetic ssystems allow reciprocal regulation of function of many organs?
They allow opposite regulation
Describe the differences between the Somatic and Autonomic Nervous System for the following:
Sensory Inputs
Efferent Pathways (number of neurons)
Axons (myelinated vs unmyelinated)
Effector Sites
Resonpe to Stimulation (Excitatory/Inhibitory and Volunatary)
Neurotransmitter
Main Functions
What neurotransmitter is realeased at the ganglia for both the sympathetic and parasympathetic nervous systems?
ACh
What is the pre-ganglionic to post-ganglionic nerve ratio for the sympathetic and parasympathetic nervous system?
Sympathetic 1:10 (many post per pre-ganglionic nerves)
Parasympathetic 1:2 (few post per pre-ganglionic nerves)
Autonomic Nervous System Picture
Ganglion and Effector Site Neurotransmitters for:
Somatic Nervous Sytem
Parasympathetic Nervous System
Sympathetic Nervous System (minus the exceptions)
In general, sympathetic pre-ganglionic neurons are ____ and sympathetic post-ganglionic neurons are ____
In general, sympathetic pre-ganglionic neurons are short and sympathetic post-ganglionic neurons are long
In general, parasympathetic pre-ganglionic neurons are ____ and parasympathetic post-ganglionic neurons are ____
In general, parasympathetic pre-ganglionic neurons are long and parasympathetic post-ganglionic neurons are short
Somatic vs Sympathetic vs Parasympathetic
Ganglionic NT
Ganglionic Receptor
Post-Ganlionic NT
Target Organ Receptor
Sympathetic vs Parasympathetic effects on organs
General info (understand the basic ideas)
Of note: both increase salivary glands –> Dry mouth when nervous is actually caused by decreased parasympathetic
Alpha and Beta Receptor General Effect
a1
a2
b1
b2
b3
Effects of the following receptors:
M1
M2
M3
Note there is also M4 and M5 but these will be covered elsewhere
a1-receptors, b-receptors, and a 2 receptors
G-Protein
Second Messenger
Target
(M1,M3,M5), (M1), and (M2, M4)
G-Protein
Second Messenger
Target
Enteric Nervous System with relation to:
Sympathetic and Parasympathetic synapse and effect on ENS activity
Control of ANS function occurs by higher ____ centers and by local ____
Control of ANS function occurs by higher CNS centers and by local reflexes
Note:
- Higher CNS centers: Hypothatlamus and brainstem (pons and medulla) control autonomic outflow
- Local regulation by reflexes involes specific autonomic ganglia and the spinal cord (no CNS required)
