Neurotransmitters Flashcards
neurons, which release the neurotransmitter acetylcholine
Cholinergic
neurons, which release the neurotransmitter norepinephrine (NE), AKA noradrenalin
Adrenergic
All sympathetic and parasympathetic preganglionic neurons
Cholinergic neurons
All parasympathetic postganglionic neurons
Cholinergic neurons
Sympathetic postganglionic neurons that innervate most sweat glands
Cholinergic neurons
Somatic nervous system motor neurons
Cholinergic neurons
Cholinergic neurons
All sympathetic and parasympathetic
preganglionic neurons
All parasympathetic postganglionic neurons
Sympathetic postganglionic neurons that innervate most sweat glands
Somatic nervous system motor neurons
ACh is stored in synaptic vesicles, released by exocytosis, and diffuses across the synaptic cleft to bind with ____ receptors, causing either excitation or inhibition of the postsynaptic cell
cholinergic
Sympathetic – most effector tissues
Presynaptic releases Ach, postsynaptic releases NE (to effector)
Sympathetic – most sweat glands
Pre- and post-synaptic releases Ach
Adrenergic neurons are:
most sympathetic postganglionic neurons
NE is stored in synaptic vesicles, released by ___, and diffuses across the synaptic cleft to bind with adrenergic receptors where it causes either excitation or inhibition of the effector cell
exocytosis
Slide 9
ok
Cholinergic receptors are ___ membrane proteins in the postsynaptic plasma membrane
integral
All cholinergic receptors bind
acetylcholine
___, named becausE nicotine mimics the action of ACh by binding to this type of receptor
cholinergic
Nicotinic receptors
____ receptors, named because a mushroom poison called muscarine binds to them and mimics the action of ACh
cholinergic
Muscarinic
Nicotine does not activate muscarinic receptors
Muscarine does not activate nicotinic receptors
Cross-reactivity
Acetylcholine activates both types of cholinergic receptor
Since acetylcholine is quickly inactivated by ____, the effects triggered by cholinergic neurons are brief
acetylcholinesterase,
Activation of nicotinic receptors by acetylcholine causes ____ (therefore excitation) of the postsynaptic cell:
Excitation of a postganglionic neuron
Excitation of a skeletal muscle fiber
depolarization
depolarization
nicotinic
Activation of ___receptors by acetylcholine sometimes causes depolarization (excitation) and sometimes causes hyperpolarization (inhibition)
muscarinic
The effect depends on the postsynaptic cell—in some cell types it causes inhibition, and in other cell types it causes excitation:
Activation of muscarinic receptors causes DUMBELS syndrome:
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
Defecation, Urination, Miosis, Bronchoconstriction, Emesis, Lacrimation, Salivation
Slide 16, 17
And 18, too
Adrenergic receptors are integral membrane proteins in the ____ plasma membrane
postsynaptic
All adrenergic receptors bind both ___
norepinephrine and epinephrine
Adrenergic receptors are activated by . . .
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
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
__is found only on cells of brown adipose tissue, where activation causes thermogenesis
β3
Norepinephrine activity ends when it is either
Taken up by the axon that released it (reuptake)
Enzymatically inactivated
Norepi can be enzymatically inactivated by?
Catechol-O-methyltransferase (COMT) Monoamine oxidase (MAO)
Norepinephrine lingers in the synaptic cleft ___ than does acetylcholine, meaning …
longer
effects triggered by adrenergic neurons usually last longer than effects due to cholinergic neurons
substance that binds to a receptor and triggers a response in the cell.
agonist
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
__ receptors are located predominantly in the heart. When adrenalin (norepinephrine and epinephrine released by the adrenal medulla) binds to __ receptors, the heart rate and strength of contraction are increased
β1
__ 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 __ receptors, blood vessels and visceral organ sphincters constrict (but the pupils of the eye dilate)
α1
The balance between sympathetic and parasympathetic activity is called ___
autonomic tone
Most body organs receive innervation from both divisions of the ANS
The divisions generally work in opposition to each other
Autonomic tone is regulated by the ___. Usually when the activity of one division is increased, the activity of the other is decreased
hypothalamus
The two divisions affect body organs differently because . . .
The postganglionic neurons release different neurotransmitters
Effector organs possess different adrenergic and cholinergic receptors
Some structures receive only sympathetic innervation:
There is no corresponding parasympathetic innervation in these structures
Sweat glands Arrectores pilorum muscles Kidneys Adrenal glands (adrenal medullae) Spleen Blood vessels in general
Sweat glands Arrectores pilorum muscles Kidneys Adrenal glands (adrenal medullae) Spleen Blood vessels in general
Structures receive only sympathetic innervation:
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
Pupils dilate
Heart rate, contraction, BP increase
Airways dilate
Abdominal viscera, skin vessels constrict
Blood flow to skeletal muscles increases
Glycogenolysis increases
GI tract movt slows
Sympathetic response
Effects of ___ last longer, and are more widespread than parasympathetic stimulation
sympathetic stimulation
More extensive divergence of sympathetic postganglionic axons means more tissues are activated ____
simultaneously
Acetylcholine is rapidly degraded by acetylcholinesterase. Norepinephrine remains in the ___ longer
synaptic cleft
Epinephrine and norepinephrine are secreted into the ___ from the adrenal medulla, intensifying and prolonging responses due to NE released from sympathetic postganglionic neurons
blood
Parasympathetic responses are characterized by the acronym SLUDD
Salivation Lacrimation Urination Digestion Defecation
responses that occur when nerve impulses pass over an autonomic reflex arc
Autonomic reflexes
Autonomic reflexes are central in regulating 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
Sensory receptor Sensory neuron Integrating center Motor neurons Effector
The overall components of an autonomic reflex arc are the same as a somatic reflex arc
The receptor in an autonomic reflex arc is the ___ of a sensory neuron
distal end
It responds to a stimulus, and produces a change that will eventually trigger nerve impulses
The ___ conducts nerve impulses from receptors to the CNS
sensory neuron
____ neurons carry information concerning chemical changes, stretch, and irritation of the viscera
Visceral sensory
Cell bodies of visceral sensory neurons are located in the sensory ganglia of associated cranial nerves or in the ____ of the spinal cord
dorsal root ganglia
The main integrating centers for most autonomic reflexes are in the____, but some integrating centers are in the spinal cord
hypothalamus and brain stem
____ in the CNS relay signals from sensory neurons to motor neurons
Interneurons
Efferent impulses from the integrating center propagate out of the CNS along ___ neurons
motor
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
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 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
Raynaud disease
digits (fingers and toes) become ischemic (lack of blood) after exposure to cold or with emotional stress
condition is due to excessive sympathetic stimulation of smooth muscle in the arterioles of the digits
anticholinergic drug that blocks parasympathetic effects
routinely administered preoperatively to suppress salivation and respiratory system secretions during surgery
used by ophthalmologists to dilate the pupils for eye examination (i.e., as a mydriatic agent)
Atropine
Atropine is also an antidote for chemical warfare agents that inactivate acetylcholinesterase
an anticholinesterase drug. It inhibits the enzyme acetylcholinesterase, thus preventing enzymatic breakdown of ACh and allowing it to accumulate in the synapses
used to treat myasthenia gravis, a condition in which skeletal muscle activity is impaired for lack of ACh stimulation
Neostigmine
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)
