Lecture 4 - ANS Flashcards
The ANS is the most important system for ____
Drug effects
Where does info come from and go to with sensory nerves?
Comes from periphery and goes to spinal cord and/or CNS
Where does info come from and go to with motor (efferent) nerves?
Flows from CNS or spinal cord to periphery
Somatic nerves control ____ muscles
Skeletal
Autonomic nerves control ____ muscles
Smooth and cardiac
Is somatic or autonomic automatic?
Autonomic
What movements do somatic nerves control?
Locomotion, respiration, and posture
In general, what does the autonomic nervous system control?
Organs and glands
Are the symp. and para systems efferent or afferent?
Efferent/motor
Is symp control generally widespread or local?
Widespread
What does ergotropic and does it better describe the symp or para system?
- Leading to energy expenditure
- Symp
What does trophotropic mean and does it better describe the symp or para system?
- Leading to growth
- Para
Where do most nerves for the para system come from and what are the exceptions to this?
- Most come from brain
- Exceptions are nerves for colon, rectum, bladder, and genitals
Symp has a ___ preganglionic axon and a ____ postganglionic axon
Short and long
Para has a ___ preganglionic axon and a ____ postganglionic axon
Long and short
Why does symp have a long postganglionic axon?
Because it activates everything at once and doesn’t matter if its close to the target
What do all preganglionics contain?
Acetylcholine, making them excitatory
What do symp postganglionics contain?
Norepinephrine, making them excitatory or inhibitory
What do para postganglionics contain?
Acetylcholine, making them excitatory or inhibitory
What determines if a nerve is excited or inhibited?
The receptor
What are the target tissues of the symp system?
- Organs of head, neck, trunk, and external genitalia
- Adrenal medulla
- Sweat glands in skin
- All vascular smooth muscle
What are the target tissues of the para system?
Organs of head, neck, trunk, and external genitalia
Does the para system ever reach limbs or the body wall?
Nope, except for external genitalia
Stimulants work at stimulating the same systems as the ____ NS
Symp
What is something to note about any drug that activates the symp NS?
Once it enters the brain, it will be a stimulant
Where are the pre-ganglionic neurons of the symp NS located?
Along spinal cord
What are the 3 adrenergic receptors?
1) Alpha 1
2) Alpha 2
3) Beta
What do alpha 1 receptors do?
- Activate phospholipase C
- Increase calcium
- Contract smooth muscle
What do alpha 2 receptors do?
- Inhibit adenylate cyclase
- Increase potassium
- Inhibit norepinephrine and insulin release
What do beta receptors do?
- Activate adenylate cyclase
- Increase protein kinase activity
- Increase heart rate and contractility, bronchodilation, vasodilation, glyconeogenesis, and lipolysis
How do drugs that are stimulants work?
By increasing the uptake of norepinephrine
Where are the pre-ganglionic neurons of the para NS located?
Brain stem
What do odd-numbered muscarinic receptors do?
- Activate phospholipase C causing increased calcium and protein kinase activity
- Cause excitation (gastric release, smooth muscle, bladder)
What do even-numbered muscarinic receptors do?
- Inhibit adenylate cyclase
- Activate potassium channels and inhibit protein kinase activity
- Inhibition of cardiac and smooth muscle
What is an example of when the SNS and PNS have opposite effects at the same site?
- SA node
- Norepinephrine (beta) increases heart rate while acetylcholine (muscarinic) decreases it
What is an example of when the SNS and PNS have opposite effects at different sites?
- Size of pupil
- Norepinephrine (alpha) causes dilation and acetylcholine (muscarinic) causes contraction
What is an example of when symp nerves act on para nerve endings?
Norepinephrine (alpha) decreases acetylcholine release in intestinal wall
What is an example of when SNS and PNS are complementary?
In the male genitals, para causes erection and symp causes ejaculation
What are 2 examples of organs that only receive SNS or PNS?
- Ciliary muscle receives acetylcholine
- Arterioles of most organs only receive norepinephrine
What is the action and receptor of the SNS in the bronchiole smooth muscle?
- Action - relaxation, causing enhanced air flow
- Receptor - beta 2 adrenergic
What is the action and receptor of the PNS in the bronchiole smooth muscle?
- Action - contraction and secretion, causing decreased air flow and increased secretions
- Receptor - muscarinic
How would you increase air flow?
- Stimulate beta 2 receptors
- Block muscarinic receptors
What is the action and receptor of the SNS in the heart?
- Action - increase heart rate and contraction force
- Receptor - beta 1
What is the action and receptor of the PNS in the heart?
- Action - decrease heart rate and contraction force
- Receptor - muscarinic
What is the action and receptor of the SNS in blood vessels?
- Contraction of skin and gut by alpha 1
- Relax skeletal muscle by beta 2
What is the action and receptor of the PNS in gastrointestinal smooth muscle?
- Relaxation of sphincters by muscarinic
- Wall contraction by muscarinic
- Increased secretions by muscarinic
What is the action and receptor of the SNS in gastrointestinal smooth muscle?
- Wall relaxation by beta 2
- Sphincter contraction by alpha
- Decreased secretions by alpha
What is the action and receptor of the PNS in the bladder?
Wall contraction and sphincter relaxation (aka micturition) by muscarinic
What is the action and receptor of the SNS in the bladder?
- Wall relaxation by beta 2
- Sphincter contraction by alpha
What is the action and receptor of the PNS in the eye?
Miosis (contraction) by muscarinic
What is the action and receptor of the SNS in the eye?
Mydriasis (dilation) caused by alpha
What is the baroreceptor (in the heart) response to increased blood pressure?
Decrease symp nerve activity and increase para nerve activity
What is the benefit of antihistamines to the common cold?
Has additional blocking effects at “non-histamine” receptor
- blocks muscarinic causing drying of mucous membranes
What are the side effects to antihistamines?
- Bladder -> relax walls and constrict sphincter (trouble urinating)
- Gut -> relax walls, constrict sphincter, and decrease secretions
What do sympathomimetics do?
Increase sympathetic receptor activity
What is the benefit of a sympathomimetic to the common cold?
Constricts blood vessels in the nasal mucosa
What are side effects of sympathomimetics?
- Bladder -> relax walls and constrict sphincter (trouble urinating)
- Gut -> relax walls, constrict sphincters, and decrease secretions
- Heart -> increase heart rate and constrict arterioles
