07 - The Autonomic Nervous System Flashcards
What is the branch of your nervous system that controls your glands and involuntary muscles?
Autonomic Nervous System (ANS)
What are the involuntary muscles?
Heart & smooth muscle
What is ANS also called?
Visceral motor nervous system
- Visceral - organs
What is the most important role of ANS?
To maintain homeostasis
Is there a sensory part to the ANS?
Yes
- There is also a sensory part of the system
- It is largely ignored except regarding referred pain and interoception
What are the 2 types of motor division?
- Somatic motor division
- Autonomic motor division
What are the 2 divisions in the autonomic motor division?
Sympathetic division
Parasympathetic division
What is the sympathetic division?
Flight, fight & fright
What is the parasympathetic division?
Rest, relaxation and rumination
What does the somatic motor division control?
Striated or voluntary muscles
What are the 2 nervous systems?
Central nervous system (brain & spinal cord)
Peripheral nervous system
What are the 2 sensory divisions that brings info to the peripheral nervous system?
Autonomic sensory division (mostly interoceptors)
Somatic sensory division
What’s the system? What motor nerve is it?
Voluntary control & one neuron from CNS to effector (no ganglia)
Somatic motor system
Somatic motor nerve
What’s the system? What motor nerve is it?
Involuntary control (autonomous) & two neurons between the CNS and effector
Autonomic motor system
Autonomic motor nerve
What are the 2 neurons between the CNS and effector of the autonomic motor system called?
First: preganglionic
Second: postganglionic
Where does the preganglionic and postganglionic neurons connect?
In areas called autonomic ganglia
What neurotransmitter is used in somatic motor systems?
Acetylcholine
- The only neurotransmitter used
What are the 2 inputs in the autonomic NS?
Sympathetic input
Parasympathetic input
How does the sympathetic input work in the heart?
Sympathetic input speeds up heart rate (tachycardia) and increases the force of contractions
- A positive inotropic effect)
- This is an appropriate response for preparing for fight and flight
How does the parasympathetic input work in the heart?
Parasympathetic input slows heart rate (bradycardia) and decreases the strength of contractions
- A negative inotropic effect
- This is an appropriate response for rest and relaxation
How does the sympathetic input work in the gastrointestinal tract?
Sympathetic input yields relaxation
How does the parasympathetic input work in the gastrointestinal tract?
Parasympathetic increase activity
What would happen if a sympathectomy were performed on the heart (i.e., all the sympathetic input was stopped)?
Decrease in heart rate and blood pressure
Are both types of input of the ANS the same in an organ?
No
- Input from one branch of the ANS is dominant in an organ
What input of the ANS is dominant in the heart?
Parasympathetic nervous system
- In the heart there are both branches of the ANS, but the sympathetic nervous system is dominated by the parasympathetic nervous system
What input of the ANS is dominant in the GI tract?
Parasympathetic nervous
- In the GI tract the parasympathetic nervous system dominates the sympathetic system for regulating gastrointestinal motility
If all autonomic input to the heart was stopped then what would happen to heart rate and force of contraction? Why?
Heart rate would increase, and the force of contractions would increase
- B/c the heart is dominated by the parasympathetic nervous system, thus if both inputs are stopped, more input from the parasympathetic nervous system is stopped, therefore, the heart rate would increase & force of contractions would increase
- The heart will not stop b/c it has pacemaker cells
Give some examples of organs with only ONE type of ANS input
Sweat glands have only sympathetic input
Visceral arterioles have almost only sympathetic input
The iris sphincter muscle has only parasympathetic inputs (it constricts the pupil)
The radial muscle of the iris has only sympathetic input (it dilates the pupil)
If all autonomic input to the peripheral blood vessels were to stop what would happen?
Blood vessels would dilate, and blood pressure would drop
What is the constriction of the pupil called?
Miosis
What is the relaxation of the pupil called?
Mydriasis
What does sympathetic stimulation cause in the eye (pupil)?
Causes radial muscles to contract
- Pupil enlarges
- B/c in a fight-flight situation, you want bigger pupils so you can see better (eg. when running away)
What does parasympathetic stimulation cause in the eye (pupil)?
Causes circular muscles to contract
- Pupil size gets smaller
- You’re relaxed thus don’t need to notice/see everything around you
Does sympathetic output have long or short preganglionic neurons?
Short
Does parasympathetic output have long or short preganglionic neurons?
Long
What are the receptor(s) used in sympathetic output?
Adrenergic receptors
- Norepinephrine (NE or noradrenalin) used on effector
What are the receptor(s) used in parasympathetic output?
Nicotinic Ach receptors
- ACh used in the ganglia
Muscarinic Ach receptors
- ACh used on the effector
What input does nicotine stimulate in the autonomic NS?
Nicotine stimulate both the sympathetic and parasympathetic at the same time
- Therefore heart rate goes all over the place
Atropine blocks the muscarinic cholinergic neurons (i.e., the postganglionic parasympathetic receptors). What would this drug do to the pupil size? How?
The pupil would dilate (mydriasis)
- Atropine only block the parasympathetic receptor
- Thus only have sympathetic receptors
- Dilated pupils
Where are the ganglia located in the parasympathetic NS?
Very close or on their effectors
Where are the ganglia located in the sympathetic NS?
Far from their effectors
Why are the ganglia on or very close to their effectors?
B/c you want to control them separately
What are the 2 outputs in the parasympathetic NS?
Cranial output (out of the head)
Sacral output (out of the base of the spine, the sacrum)
What are the 3Rs for parasympathetic NS?
Rest
Relaxation
Rumination
What does SLUDD stand for in the parasympathetic NS?
Salivation
Lacrimation
Urination
Digestion
Defecation
What is the “king” of the parasympathetic NS?
Vagus nerve
- Cranial nerve X (10th)
- This cranial nerve has input into almost all of the viscera (organs)
What are the 3 Fs in the sympathetic NS?
Fight
Flight
Fright
Which side does the sympathetic trunk (or chain) ganglia in the sympathetic NS run on?
Both sides of the spinal cord
What does the sympathetic trunk (or chain) ganglia in the sympathetic NS do?
Neurons run up and down the chain “broadcasting” the sympathetic message
What are the sympathetic ganglia in the sympathetic NS called?
Collateral ganglia
What are the 2 outputs in the sympathetic NS?
Thoracic output
Lumbar output
Can sympathetic neurons have split axons?
Yes
- Some sympathetic neurons have split axons (axon collaterals)
What does the split axons (axon collaterals) in the sympathetic NS do?
Send messages up and down the sympathetic trunk ganglia and also out to the collateral ganglia
What are the 2 receptors of the Autonomic NS?
Cholinergic receptors
Adrenergic receptors
Where are cholinergic receptors found?
Found in the synapses of
- the sympathetic and parasympathetic ganglia
- the postganglionic parasympathetic effectors
Where are adrenergic receptors found?
Found only on the sympathetic postganglionic target organs (aka effectors)
What are the 2 types of cholinergic receptors?
Muscarinic receptors
Nicotinic receptors
Where are muscarinic receptors found?
Found on all parasympathetic target organs
Where are nicotinic receptors found?
The receptor found in sympathetic and parasympathetic ganglia
What does stimulation of muscarinic receptors lead to?
Acetylcholine (or muscarine) stimulating these receptors leads to
- Decreases heart rate
- Increases intestinal motility
- All parasympathetic effects
What does stimulation of nicotinic receptors lead to?
Stimulation of these receptors (like with nicotine) leads to both sympathetic and parasympathetic effects
Do the cholinergic receptors last a long time?
No, these receptors have only a short time of activation
- acetylcholine breaks down rapidly because of acetylcholinesterase (AChase or AChE)
What happens to your pupils when an anticholinesterase like the nerve gas sarin is consumed? Why?
Pupils constrict (miosis)
- B/c there is more stimulation in the parasympathetic side
- Miosis is a result from the parasympathetic NS
What are the neurotransmitters of adrenergic receptors?
Adrenalin and noradrenalin
- Aka epinephrine and norepinephrine, respectively
What are the 2 subtypes of adrenergic receptors? What do they do?
a (alpha)
- Generally, stimulate contractions
β (beta)
- Generally, inhibit contractions (except in the “heart muscle” or myocardium)
Are stimulation in adrenergic receptors short or long term activation of the neurons? Why?
Stimulation leads to relatively long-term activation of the neurons
- Breakdown or removal of the neurotransmitter is slow compared to acetylcholine
What does the activation time of the neurons and the spread of the sympathetic NS stimulation tell us?
The long activation of the neurons combined with the large spread of the sympathetic NS stimulation means sympathetic effects last a relatively long time
What are the 2 subtypes of alpha adrenergic receptors?
a1
a2
What are the 3 subtypes of beta adrenergic receptors?
β1
β2
β3
What are a1 (alpha 1) adrenergic receptors?
- Causes contractions of smooth muscle
- Found mostly in blood vessels of the viscera except in the heart
What are a2 (alpha 2) adrenergic receptors?
- Presynaptic receptors
- Promotes clotting
- Often ignored except by close family members
What are β1 (beta 1) adrenergic receptors?
- Used for heart muscle
- tachycardia and increased contractility
What do β2 (beta 2) adrenergic receptors do?
- Relaxes the bronchioles
- Relaxes the uterus
- Almost all sympathetic target organs are relaxed
What do β3 (beta 3) adrenergic receptors do?
Increases lipolysis
What are alpha-adrenoceptors for?
Blood vessels
- take off the tail fo the alpha symbol –> look like a blood vessel
Where are β1 adrenoceptors found?
Heart
- you have 1 heart (β1)
Where are β2 adrenoceptors found?
The lungs
- you have 2 lungs (β2)
What are the 2 adrenergic drugs? How do they work?
Beta-blockers for tachycardia and hypertension
- Beta-receptors are blocked which slows the heart
- Specific ß1-receptor antagonists are better because:
- Slow heart rate and make the heart more efficient
- Do not block ß2-receptors so bronchioles are not constricted
Beta-agonists for asthma
- Dilate bronchioles but speed up the heart because both ß1 and ß2 -receptors are stimulated
- Specific ß2 -agonists are better because they mostly just dilate the bronchioles
- Salbutamol (Ventolin®) is a specific agonist of the ß2 receptor and provides tremendous relief for asthma sufferers with constricted bronchioles
How is pain in a visceral organ experienced?
As a dull aching pain (often called visceral pain) and often not at the site of damage
What is pain in a visceral organ called?
Referred pain
- Aka visceral pain
What nerves carry referred pain of the ANS?
- Visceral afferents
- Sympathetic nerves
- They come in to the CNS at the level of the thoracic and lumbar spine
What controls everything you can not control?
The autonomic nervous system controls everything you cannot control
