Exam 3 - ANS - Neurotransmitters Flashcards
Autonomic neurons are classified into two groups based on the neurotransmitter they release:
Cholinergic neurons, which release the neurotransmitter acetylcholine (ACh)
Adrenergic neurons, which release the neurotransmitter norepinephrine (NE), AKA noradrenalin
which release the neurotransmitter acetylcholine (ACh)
which release the neurotransmitter norepinephrine (NE), AKA noradrenalin
Cholinergic neurons,
Adrenergic neurons,
Cholinergic neurons are:
All sympathetic and parasympathetic ___
All parasympathetic ____
Sympathetic postganglionic neurons that innervate most ____
Somatic nervous system _____
preganglionic neurons
postganglionic neurons
sweat glands
motor neurons
ACh is stored in synaptic vesicles, released by exocytosis, and diffuses across the synaptic cleft to bind with cholinergic receptors, causing either
excitation or inhibition of the postsynaptic cell
Look at slide 4 for comparison of motor pathways
Nice
most effector tissues are para or sympathetic?
Sympathetic
most sweat glands are para or sympathetic?
Sympathetic
Nicotonic receptors to muscarinic receptors
parasympathetic
Adrenergic neurons are most sympathetic …
postganglionic neurons
NE is stored in synaptic vesicles, released by exocytosis, and diffuses across the synaptic cleft to bind with adrenergic receptors where it causes either
excitation or inhibition of the effector cell
look at slide 9 of ppt
do it!
Different types of cholinergic receptors and different types of adrenergic receptors found in the various postsynaptic cells are largely responsible for the variety of responses elicited by…
binding of the neurotransmitter ligand with the receptor
Cholinergic receptors are _____ in the postsynaptic plasma membrane
All cholinergic receptors bind ____
There are two types of cholinergic receptors:
integral membrane proteins
acetylcholine
two types: nicotinic and muscarinic
named because nicotine mimics the action of ACh by binding to this type of receptor
Nicotinic receptors
named because nicotine mimics the action of ACh by binding to this type of receptor
Nicotinic receptors
named because a mushroom poison called muscarine binds to them and mimics the action of ACh
Muscarinic receptors
Cholinergic Receptors:
Cross-reactivity between nicotinic or muscarinic?
Nicotine does not activate muscarinic receptors
Muscarine does not activate nicotinic receptors
Cholinergic Receptors:
______ activates both types of cholinergic receptor
Since acetylcholine is quickly inactivated by acetylcholinesterase, the effects triggered by cholinergic neurons are ____
Acetylcholine
brief
Activation of nicotinic receptors by acetylcholine causes depolarization (therefore excitation) of the postsynaptic cell:
Excitation of a postganglionic neuron
Excitation of a skeletal muscle fiber
Activation of ______ by acetylcholine sometimes causes depolarization (excitation) and sometimes causes hyperpolarization (inhibition)
Muscarinic receptors
Muscarinic receptors:
The effect depends on the postsynaptic cell—in some cell types it causes inhibition, and in other cell types it causes excitation:
Binding of ACh to muscarinic receptors of smooth muscle sphincters in the gastrointestinal tract causes them to relax
ACh causes sphincter muscles of the eye to contract
Binding of ACh to _____ receptors of smooth muscle sphincters in the gastrointestinal tract causes them to relax
muscarinic
In muscarinic receptors, ACh causes sphincter muscles of the eye to ____
contract
Activation of muscarinic receptors, defecation
relaxation
Activation of muscarinic receptors, miosis
contraction
Activation of muscarinic receptors causes DUMBELS syndrome:
Defecation, Urination, Miosis, Bronchoconstriction, Emesis, Lacrimation, Salivation
- This is consistent with the previous slide, which stated:
- Binding of ACh to muscarinic receptors of smooth muscle sphincters in the gastrointestinal tract causes them to relax
- ACh causes sphincter muscles of the eye to contract
Review Slides 16, 17, and 18 and the associated diagrams
DO IT!
Activation of nicotinic receptors by ACh causes depolarization (excitation), whereas activation of muscarinic receptors by ACh…
…sometimes causes depolarization (excitation) and sometimes causes hyperpolarization (inhibition)
Adrenergic receptors are integral membrane proteins in the postsynaptic plasma membrane
All adrenergic receptors bind both ____
Adrenergic receptors are activated by . . .
norepinephrine and epinephrine
Norepinephrine released by sympathetic postganglionic neurons
Epinephrine and norepinephrine released as hormones into the blood by the adrenal medulla
There are two types of adrenergic receptors:
α receptors
β receptors
Adrenergic receptor activity
The receptors are further classified into subtypes based on responses they elicit and drugs that activate or block them:
α1 and α2
β1, β2, and β3
Activation of subscript 1 receptors (α1 and β1) is usually excitatory
Activation of subscript 2 receptors (α2 and β2) is usually inhibitory
β3 is found only on cells of brown adipose tissue, where activation causes thermogenesis
Activation of subscript 2 receptors (α2 and β2) is usually
inhibitory
β3 is found only on cells of
brown adipose tissue, where activation causes thermogenesis
activation of β3 causes:
thermogenesis
activation of β3 causes:
thermogenesis
Norepinephrine activity ends when it is either
Taken up by the axon that released it (reuptake)
Enzymatically inactivated by . . .
Catechol-O-methyltransferase (COMT) Monoamine oxidase (MAO)
Norepinephrine lingers in the synaptic cleft longer than does acetylcholine, meaning…
effects triggered by adrenergic neurons usually last longer than effects due to cholinergic neurons
is a substance that binds to a receptor and triggers a response in the cell.
agonist
also binds to the receptor, but it fails to activate the receptor and actually blocks the receptor from activation by agonists.
antagonist
activates a receptor but does not cause as much of a physiological change as does a full agonist.
partial agonist
The receptors of the human body work by being stimulated or inhibited by natural agonists and antagonists (such as hormones and neurotransmitters), or synthetic agonists and antagonists (such as drugs)
You’re on your way to being a PA!
___receptors are located predominantly in the heart.
β1
When adrenalin (norepinephrine and epinephrine released by the adrenal medulla) binds to β1 receptors,
the heart rate and strength of contraction are increased.
α1 receptors are located in blood vessels of virtually all sympathetic target organs except the heart. When adrenalin (norepinephrine and epinephrine released by the adrenal medulla) binds to α1 receptors,
blood vessels and visceral organ sphincters constrict (but the pupils of the eye dilate).
Alpha blockers are adrenergic blockers that attach mainly to the α1 receptors of veins and arteries. They “block” the effects of adrenalin on α1 receptors, relaxing the muscles that constrict blood vessels, allowing blood to pass more easily.
Pharmacological Application— Alpha blockers
Alpha blockers are adrenergic blockers that attach mainly to the α1 receptors of veins and arteries. They “block” the effects of adrenalin on α1 receptors, relaxing the muscles that constrict blood vessels, allowing blood to pass more easily.
Pharmacological Application— Alpha blockers
Dual innervation
Most body organs receive innervation from both divisions of the ANS
The divisions generally work _____
in opposition to each other
The balance between sympathetic and parasympathetic activity is called
autonomic tone
Autonomic tone is regulated by the
hypothalamus.
Usually when the activity of one division is increased….
the activity of the other is decreased
The two divisions of the ANS affect body organs differently because…
The postganglionic neurons release different neurotransmitters
Effector organs possess different adrenergic and cholinergic receptors
Dual innervation
Rather than thinking of the two ANS divisions as antagonistic, consider of them to be complementary.
The sympathetic division is the accelerator and the parasympathetic is the brake. Interaction between the two is required to drive the car
Single Innervation:
Some structures receive only sympathetic innervation:
Sweat glands Arrectores pilorum muscles Kidneys Adrenal glands (adrenal medullae) Spleen Blood vessels in general
There is no corresponding parasympathetic innervation in those structures
The decrease in sympathetic tone suffices to decrease effects of sympathetic activation
The sympathetic division dominates the parasympathetic division during physical or emotional stress:
The body preferentially requires functions that support vigorous physical activity and rapid production of ATP
It does not need functions that favor the storage of energy
The sympathetic division can be thought of as the E division:
Exercise, Excitement, Emergency, Embarrassment
Activation of the sympathetic division and release of adrenal medulla hormones initiates a series of effects collectively called the fight or flight response:
Pupils dilate
Heart rate, force of heart contraction, and blood pressure increase
Airways dilate
Blood vessels in abdominal viscera (such as kidneys and gastrointestinal tract) constrict
Blood vessels in skin constrict (skin becomes pale)
Blood flow to skeletal muscles increases
Blood glucose level rises as liver cells perform glycogenolysis
Gastrointestinal tract movements slow and digestive secretions decrease
Effects of sympathetic stimulation last longer, and are more widespread than parasympathetic stimulation:
More extensive divergence of sympathetic postganglionic axons means more tissues are activated simultaneously
Acetylcholine is rapidly degraded by acetylcholinesterase. Norepinephrine remains in the synaptic cleft longer
Epinephrine and norepinephrine are secreted into the blood from the adrenal medulla, intensifying and prolonging responses due to NE released from sympathetic postganglionic neurons
Parasympathetic responses are characterized by the acronym SLUDD:
Salivation Lacrimation Urination Digestion Defecation
The parasympathetic division enhances “rest and digest” activities
Autonomic reflexes are responses that occur when nerve impulses….
Autonomic reflexes are central in regulating…
pass over an autonomic reflex arc
conditions in the body
The overall components of an autonomic reflex arc are the same as a somatic reflex arc:
Sensory receptor Sensory neuron Integrating center Motor neurons Effector
The receptor in an autonomic reflex arc is the ____ end of a ____ neuron
It responds to a stimulus, and produces a change that will eventually trigger nerve impulses
distal
sensory
Autonomic sensory receptors are generally
interoceptors
Sensory neuron:
The sensory neuron conducts nerve impulses from receptors to the CNS
Visceral sensory neurons carry information concerning…
…chemical changes, stretch, and irritation of the viscera
Sensory neuron:
Cell bodies of visceral sensory neurons are located in the sensory ganglia of….
associated cranial nerves or in the dorsal root ganglia of the spinal cord.
Integrating center
Interneurons in the CNS relay signals from….
…sensory neurons to motor neurons
The main integrating centers for most autonomic reflexes are in the hypothalamus and brain stem, but some integrating centers are….
in the spinal cord
Efferent impulses from the integrating center propagate out of the CNS along…
… motor neurons
Two motor neurons connect the CNS to the effector (the rule for the ANS):
Preganglionic neuron
Conducts motor impulses from CNS to an autonomic ganglion and is Myelinated
Postganglionic neuron
Conducts motor impulses from ganglion to effector
Unmyelinated
Two motor neurons connect the CNS to the effector (the rule for the ANS):
Preganglionic neuron
Postganglionic neuron
Conducts motor impulses from CNS to an autonomic ganglion and is Myelinated
Preganglionic neuron
Conducts motor impulses from ganglion to effector
Unmyelinated
Postganglionic neuron
Effectors in an autonomic reflex are:
Smooth muscle
Cardiac muscle
Glands
The reflex is called an autonomic reflex
We are not usually aware of autonomic activities because…
the integrating centers for autonomic responses are in the spinal cord or the lower regions of the brain
Autonomic control by higher centers
The major control and integration center of the ANS is the hypothalamus, which . . .
Receives sensory input
Provides output to autonomic centers in the brain stem and spinal cord
Is connected to both the sympathetic and parasympathetic divisions of the ANS
Polygraph testing:
The fact that most autonomic responses can not be consciously altered or suppressed to any great degree is the basis for polygraph (“lie detector”) tests, which take advantage of changes in certain body parameters when someone is under duress—the stress or anxiety associated with lying
Sweating
Depth and rate of breathing
Heart rate
Blood pressure
Information about a body parameter obtained by monitoring devices and displayed to the person being monitored provides ____, and may enable the individual to learn to exercise a degree of conscious control over the parameter monitored
Biofeedback has been found to be effective for the treatment of headaches and migraines
biofeedback
In Raynaud disease the digits (fingers and toes) become ischemic (lack of blood) after exposure to cold or with emotional stress
The condition is due to….
….excessive sympathetic stimulation of smooth muscle in the arterioles of the digits
_____ is an anticholinesterase drug. It inhibits the enzyme acetylcholinesterase, thus preventing enzymatic breakdown of ACh and allowing it to accumulate in the synapses
Neostigmine
_____ is used to treat myasthenia gravis, a condition in which skeletal muscle activity is impaired for lack of ACh stimulation
Neostigmine
treats myasthenia gravis and helps inhibit acetylcholinesterase
Neostigmine
treats myasthenia gravis and helps inhibit acetylcholinesterase
Neostigmine
______ help relieve depression because they prolong the activity of norepinephrine on the postsynaptic membrane (NE is frequently classified as a “feel good” neurotransmitter)
Tricyclic antidepressants have the brand names Elavil and Sinequan
Tricyclic antidepressants
_______ inactivates norepinephrine released into synapses of postganglionic sympathetic division neurons
Monoamine oxidase
MAO inhibitors help relieve depression because they…
…prolong the activity of norepinephrine on the postsynaptic membrane (NE is frequently classified as a “feel good” neurotransmitter)
