Lecture 8: Autonomic Nervous System Flashcards
How is sensory information (AP) carried to the CNS from the periphery?
Afferent neurons
How is motor information (AP) carried from the CNS out to the periphery?
Efferent neurons (motorneuron)
At the simplest level, the nervous system functions in a series of ________.
Reflex arcs
What occurs first when you touch a hot stove?
Nociceptors in hand are brought to threshold and an AP travels down the nerve to the spinal cord.
What occurs at the spinal cord after you touch a hot stove?
- The AP depolarizes the pre-synaptic membrane of the axon from nociceptors.
- The efferent neuron is brought to threshold by the epsp’s
What occurs from the spinal cord out to the hand during the withdraw reflex?
An AP travels through the (alpha)-motorneuron out to the hand activating the skeletal muscle.
What takes the place of the efferent neuron (motorneurons) in the autonomic reflex arc?
Autonomic nervous system
How is the stimulus coming through the afferent neuron different for the autonomic nervous system?
Are often much broader stimuli, and many times are afferents within the viscera
In the reflex arc what is more important for function, spinal cord or brain?
The spinal cord, don’t actually need a brain for this reflex.
Where does the majority of the integration of autonomic reflex occur? (Be specific)
Within the brain, more specifically the lower levels (brainstem and hypothalamus)
The outflow of the ANS has how many neurons in series going to the effector cell?
Two neurons
What is a ganglion?
Collection of cell bodies outside of the CNS
Where does the pre-ganglionic axon synapse on the post-ganglionic neuron?
The ganglion
Where does the post-ganglionic neuron travel?
To the target organ where it synapses
Where do the axons of the parasympathetic pre-ganglionic axons leave the CNS?
- Cranial region
- Sacral region
Where are the ganglia of the parasympathetic nervous system located?
On or near the target organ
What are lengths of the parasympathetic pre- and post-ganglionic fibers?
Pre-ganglionic = long
Post-ganglionic = short
Where do the axons of the sympathetic pre-ganglionic axons leave the CNS?
- Thoracic region
- Lumbar region
Where are the ganglia of the sympathetic nervous system located?
The sympathetic chain, just outside the vertebral column
What are lengths of the sympathetic pre- and post-ganglionic fibers?
Pre-ganglionic = short
Post-ganglionic = long
In the parasympathetic and sympathetic nervous system what is the NT released by the pre-ganglionic fiber and what receptor does it bind to?
ACh is released and binds to a nicotinic AChR on the post-ganglionic cell membrane.
What occurs when ACh binds to the nAChR on the post-ganglionic cell membrane?
- nAChR is a ligand-gated sodium channel
- Sodium enters the dendrite causing an epsp and eventually an AP
What NT is released by the post-ganglionic cell in the parasympathetic nervous system?
ACh
What is the efferent synaptic structure in the autonomic nervous system? (She uses a specific analogy here)
These synapses are en passant (in passing)
*Like the mailman throwing your mail out of the window as/he she goes by your house…
What are varicosities of the autonomic nerves; what do they contain?
Small swellings along the axon that contain vesicles with NT
Due to the efferent synapses of the autonomic nervous system not being as protected as the specialized NMJ’s what occurs?
Substantial leakage of the NT into the systemic circulation.
*Can be used as an indicator of autonomic nervous system activity.
What type of receptor does ACh bind to on the effector cell after being released from the post-ganglionic cell in the parasympathetic nervous system?
A muscarinic receptor (GPCR)
What does binding of ACh to an M2 (muscarnic) receptor cause in cardiac tissue?
↓cAMP —-> ↑ gK+ (hyperpolarizes cell)
What kind of receptor does ACh bind to on the post-ganglionic cells’s dendrites after being released from the pre-ganglionic cell of the sympathetic nervous system?
Nicotinic ACh receptor
What is the NT released by the post-ganglionic fiber of the sympathetic nervous system?
Norepinephrine
What two receptors can norepinephrine bind to?
- α-adrenergic receptor
- β- adrenergic receptor
What do the α-adrenergic receptors have a higher affinity for?
Higher affinity for NE than epinephrine
What do the β- adrenergic receptors have a higher affinity for?
Higher affinity for epinephrine
What affect do β- adrenergic receptors have on cAMP?
all ↑ cAMP
What kind of cells are found within the adrenal medulla and what do they produce?
Chromaffin cells which produce epinephrine
The adrenal medulla is equivalent to what for the sympathetic nervous system?
Sympathetic ganglion (where pre-ganglionic fibers synapses with post-ganglionic fibers)
What NT acting on what kind of receptor tells the adrenal medulla to secrete epinephrine?
ACh acting at nicotinic receptors
Where does the epinephrine released by the adrenal medulla go?
To the blood
Which two muscles of the eye will be affected by the sympathetic nervous system?
1) Radial muscle of iris (contracts)
2) Ciliary muscle of lens (relaxes)
What type of receptor is found on the radial muscle of the iris; what affect is produced by the sympathetic NS?
- α-adrenergic receptor
- Contracts muscle, dilating the pupil, allowing more light in
What type of receptor is found on the ciliary muscle of the lens; what affect is produced by the sympathetic NS?
- β-adrenergic receptor
- Relaxes muscle, flattening the lens, allowing focus on far objects
What type of receptors are found on the heart for the sympathetic nervous system; what do they do?
- β1 and β2-adrenergic receptors
- Increase the HR and strength of contraction
What’s the simple rule of thumb for α-receptors acting on the vasculature?
Cause contraction of vascular smooth muscle = vasoconstriction
What’s the simple rule of thumb for β-receptors acting on the vasculature?
Cause relaxation of vascular smooth muscle = vasodilation
Most arteries and veins contain which receptors?
Both α and β receptors
Which organs do the α and β receptors have a strong effect on?
- Skeletal muscle
- Abdominal organs
- Kidneys
What’s the importance of having a lot of α and β receptors in the abdominal organs and kidneys?
So blood can be shunted to the more important organs during sympathetic response, such as: heart, lungs, brain, and skeletal muscle
Which arterial systems only contain α receptors?
- Skin and mucosa (so you don’t bleed to death)
- Salivary glands (dry mouth)
- Brain
Bronchial smooth muscle contains which receptor and the effect?
- β2 receptors
- Smooth muscle relaxation and bronchodilation
Bronchial glands contain which receptor and the effect?
α1 receptors: decrease secretion (profound effect)
β2 receptors: increase secretion
What is contained in the inhaler of a person who is asthmatic?
β2 agonist (causes bronchodilation)
What receptors are found in the digestive tract for motility; affect during sympathetic response?
- α1 and β receptors
- Decrease motility
What is the importance of having α1 receptors on the sphincter of the GI tract during a sympathetic response?
Sphincter contracts and blocks food from moving any further through the digestive tract
What is the function of α2 receptors on secretion in the GI tract during sympathetic response?
Decrease secretion
Function of the α1 and β2 receptors of the liver during sympathetic response?
Increase glycogenolysis (release of glucose)
Function of the α1, β1, and β3 receptors found in adipose tissue during the sympathetic response?
Increase lipolysis
After the sympathetic response, which receptors does the parasympathetic system act on?
Muscarinic receptors
Why is there not parasympathetic receptors in all the same places as sympathetic?
All that is required in many of these areas is just to turn down the sympathetic response and things will return tor normal
How does the parasympathetic system act directly and indirectly on the heart?
- Decreases HR (directly) through SA and AV node
- Contractility of the hear (indirectly) since the sympathetic system is turned down
