Human Physio Ch. 11 Auto and Somatic Motor Control
Neurotransmitter activation of its receptor terminates when the neurotransmitter:
(1) diffuses away, (2) is metabolized by enzymes in the extracellular fluid, or (3) is actively transported into cells around the synapse.
Which functions are controlled through the autonomic nervous system? 1. blood pressure 2. heart rate 3. water balance 4. temperature regulation ANSWER: 1, 2, 3 1 and 2 2, 3, 4 1 and 3 1, 2, 3, 4
1, 2, 3, 4 blood pressure, heart rate, water balance, temperature regulation
Which area(s) of the brain exert(s) control over the autonomic nervous system? 1. cerebrum 2. cerebellum 3. hypothalamus 4. pons 5. medulla 6. thalamus ANSWER: 2, 3, 4, 5 1, 2, 3, 5 1, 3, 4, 5 1, 3, 5 1, 2, 3, 4, 5, 6
1, 3, 4, 5 cerebrum, hypothalamus, pons, medulla
Nicotine is thought to cause approximately ________ deaths per year, worldwide.
5,000,000
Nicotine is thought to cause approximately ________ deaths per year, worldwide. ANSWER: 5,000 500 5,000,000 500,000 50,000
5,000,000
Sympathetic Chain
A paired bundle of nerve fibers that run from the base of the skull to the coccyx. Lie on both sides of vertebral column; control effectors in body wall, inside thoracic cavity, and in the head and limbs.
Vagotomy
A procedure in which the vagus nerve is surgically cut, was an experimental technique used in the nineteenth and early twentieth centuries to study the effects of the autonomic nervous system on various organs. For a time it was the preferred treatment for stomach ulcers, but the side effects later led physicians to favor drug therapies instead.
What is a varicosity in the autonomic nervous system?
A series of swollen ends that act as synapses
Match the answers to the questions. A. true only for the sympathetic division B. true only for the parasympathetic division C. true for both divisions Most preganglionic neurons originate in the thoracic and lumbar regions of the spinal cord.
A. true only for the sympathetic division
Indirect agonists/antagonists
Act by altering secretion, reuptake, or degradation of neurotransmitters. E.g.: cocaine, Anticholinesterases
Each of these statements is true except one. Identify the exception. ANSWER: -β1 receptors respond equally well to both epinephrine and norepinephrine. -β2 receptors are not innervated by sympathetic neurons, so are more sensitive to epinephrine, delivered via the blood. -Activation of α receptors opens Na+ channels in the membrane. -Monoamine oxidase is the main enzyme responsible for the degradation of catecholamines.
Activation of α receptors opens Na+ channels in the membrane.
Compare and contrast alpha, beta, muscarinic, and nicotinic receptors. Describe where each is found and the ligands that bind to them.
Alpha and beta adrenergic; nicotinic and muscarinic cholinergic. Nicotinic—on skeletal muscle and postganglionic autonomic neurons. Adrenergic and muscarinic receptors—autonomic targets.
What is the trigger for ACh release into the synaptic cleft of a neuromuscular junction?
An action potential at the axon terminal opens voltage-gated Ca2+ channels.
Match the following with its description. A. acetylcholine B. norepinephrine C. cholinergic nicotinic receptor D. adrenergic receptor E. cholinergic muscarinic receptor target receptor for preganglionic neurons
C. cholinergic nicotinic receptor
Match the answers to the questions. A. true only for the sympathetic division B. true only for the parasympathetic division C. true for both divisions Inside the ganglia are interneurons, which modulate messages.
C. true for both divisions
Neurons that secrete acetylcholine are described as __________ neurons, whereas those that secrete norepinephrine are called either __________ or ___________ neurons.
Cholinergic; adrenergic or noradrenergic—
Predict which type of ACh receptors (nicotinic or muscarinic) chromaffin cells have?
Chromaffin cells are modified postganglionic neurons, so they have nicotinic receptors.
Direct agonists/antagonists
Combine with the target receptor to mimic or block neurotransmitter action.
Sometimes the effects of sympathetic stimulation can be contradictory in the same types of tissue. For example, in the arterioles of the GI tract, sympathetic stimulation causes constriction while arterioles of skeletal muscle can dilate in response to sympathetic stimulation. What mechanism explains these opposite effects?
Different receptors for the same neurotransmitter
What is the advantage of divergence of neural pathways in the autonomic nervous system?
Divergence allows one signal to affect multiple targets.
Match the following with its description. A. acetylcholine B. norepinephrine C. cholinergic nicotinic receptor D. adrenergic receptor E. cholinergic muscarinic receptor parasympathetic tissue receptor
E. cholinergic muscarinic receptor
Chromaffin Cells
Found in the adrenal medulla, axonless cell bodies that secrete the neurohormone epinephrine directly into the blood.
postganglionic neuron
In the autonomic division of the PNS, a neuron that has its *cell body located in the autonomic ganglion* (where a preganglionic neuron synapses with it) and whose axon synapses with the target axon.
preganglionic neuron
In the autonomic divison of the PNS, a neuron that has its *cell body located in the CNS*, and whose axon extends into the PNS to synapse with a second neuron at an autonoic ganglion. (The second neuron's axon synapses with the target axon)
What is the main enzyme responsible for the breakdown of catecholamines?
Monoamine oxidase
________ postganglionic sympathetic neurons secrete ________ onto their target cells. ANSWER: Most, acetylcholine All, acetylcholine All, norepinephrine Most, norepinephrine
Most, norepinephrine
Compare and contrast neuroeffector junctions and neuromuscular junctions.
Neuroeffector junction—distal ends of autonomic axons, anywhere there is a varicosity. Neuromuscular junction—axon terminals of the somatic motor neuron.
autonomic ganglion
Site of the synapse between the *axon* of the preganglionic neuron and the *cell body* of the postganglionic neuron
How do Sympathetic and Parasympathetic branches differ anatomically? Describe how they differ in each area.
The main anatomical differences are (1) the pathways' point of origin in the CNS and (2) the location of the autonomic ganglia.
Why are Serotonin reuptake inhibitors (SRIs) considered better than some older drugs that act on norepinephrine?
The older antidepressant drugs that act on norepinephrine transport and metabolism (tricyclics and MAO inhibitors) may have side effects related to their actions in the autonomic nervous system, including cardiovascular problems, constipation, urinary difficulty, and sexual dysfunction. The serotonin reuptake inhibitors have fewer autonomic side effects.
Adrenal Cortex
The outer portion of the adrenal glands atop the kidneys. It is a true endocrine gland of epidermal origin that secretes steroid hormones
motor end plate
The portion of the cell membrane at the neuromusclar junction; essentially the postsynaptic membrane at the synapse. On the postsynaptic side of the neuromuscular junction, the muscle cell membrane that lies opposite the axon terminal is modified into a series of folds that look like shallow gutters. Along the upper edge of each gutter, nicotinic ACh receptor (nAChR) channels cluster together in an active zone.
neuroeffector junction
The synapse between a postganglionic autonomic neuron and its target cell.
________ are swellings that contain vesicles filled with neurotransmitters. ANSWER: Varicosities Ganglia Dendrites Cell bodies
Varicosities //contain receptors for hormones and paracrines like histamine =can inhibit or facilitate NT release //NT are synthesized in axon varicosities =ACh, and NE are synthesized by cytoplasmic enzymes //and is releases following depolarization, calcium signal, exocytosis =NT diffuse into ISF until target cell receptor is reached //More NT means longer/ stronger response =NT production determined by rate of breakdown/removal //uptake of NT occurs by Varicosities and they resuse chemical =repackaged or broken down by MAO
more neurotransmitter means:
a longer or stronger response.
Biofeedback training
a physiological and behavioral approach in which an individual receives information regarding particular autonomic functions and is rewarded for influencing those functions in a desired direction
Cholinergic receptors respond to the neurotransmitter
acetylcholine.
Divergence
an important feature of autonomic pathways; Each postganglionic neuron can innervate a different target, meaning that a single signal from the CNS can affect a large number of target cells simultaneously.
Antagonistic control of efferent output is typical of the ________ division. ANSWER: somatic and autonomic somatic autonomic somatic and sensory sensory
autonomic
Autonomic neurotransmitters are synthesized in the ANSWER: dendrites. cell body. axon. dendrites and cell body.
axon
Generalized sympathetic dysfunction may result from systemic diseases such as _____ and ________ _________ .
cancer; diabetes mellitus
Primary autonomic failure occurs when sympathetic neurons degenerate. With diminished sympathetic input, target tissues upregulate. This increase in receptor abundance leads to ___________ _________ , a state in which the administration of exogenous adrenergic agonists causes a greater-than-expected response.
denervation hypersensitivity
Neurotransmitter release follows the pattern found in other cells:
depolarization—calcium signal—exocytosis. (When an action potential arrives at the varicosity, voltage-gated Ca2+ channels open, Ca2+ enters the neuron, and the synaptic vesicle contents are released by exocytosis. Once neurotransmitters are released into the synapse, they either diffuse through the interstitial fluid until they encounter a receptor on the target cell or drift away from the synapse.)
Nicotine enhances the release of ________ in the brain. ANSWER: acetylcholine glutamate dopamine epinephrine serotonin
dopamine
The autonomic nervous system works closely with the ________ system and the __________ __________ system to maintain homeostasis in the body
endocrine; behavioral state
The signal molecule ________ elicits the stronger response from beta2 receptors. ANSWER: acetylcholine phospholipase C epinephrine norepinephrine
epinephrine
Somatic motor pathways (a) are excitatory or inhibitory? (b) are composed of a single neuron or a preganglionic and a postganglionic neuron? (c) synapse with glands or with smooth, cardiac, or skeletal muscle?
excitatory, single neuron, and synapse with skeletal muscle
The two types of cholinergic receptors are
nicotinic and muscarinic.
The two types of cholinergic receptors are ANSWER: beta and adrenergic. alpha and beta. nicotinic and muscarinic. nicotinic and adrenergic.
nicotinic and muscarinic.
Both sympathetic and parasympathetic *preganglionic* neurons release acetylcholine (ACh) onto ___________ __________ _____________ on the postganglionic cell
nicotinic cholinergic receptors (AChR)
The signal molecule ________ elicits the stronger response from alpha receptors. ANSWER: epinephrine acetylcholine cAMP norepinephrine
norepinephrine
Most postganglionic sympathetic neurons secrete ___________ onto _________ receptors on the target cell
norepinephrine (NE); adrenergic
Cholinergic muscarinic receptors are found at the ________ in the ANS. ANSWER: parasympathetic autonomic ganglia parasympathetic neuroeffector junctions sympathetic autonomic ganglia sympathetic neuroeffector junctions
parasympathetic neuroeffector junctions
neuromuscular junction
point of contact between a motor neuron and a skeletal muscle cell.
The adrenal medulla is to the _______ pituitary as the adrenal cortex is to the ______ pituitary.
posterior; anterior.
The ________ is the major source of parasympathetic output. ANSWER: vagus nerve ganglia hypoglossal nerve varicosities
vagus nerve
Another name for the autonomous nervous system that was used in older times is the _______ ________ _______.
vegetative nervous system
Trauma to *hypothalamic* control centers may disrupt the body's ability to regulate _________ __________ or ____________.
water balance; temperature
You have discovered a neuron that innervates an endocrine cell in the intestine. To learn more about this neuron, you place a marker substance at the endocrine cell synapse. The marker is taken into the neuron and transported in a vesicle by retrograde axonal transport to the nerve cell body. (a) By what process is the marker probably taken into the axon terminal? (b) The nerve cell body is found in a ganglion very close to the endocrine cell. To which branch of the peripheral nervous system does the neuron probably belong? (Be as specific as you can.) (c) Which neurotransmitter do you predict will be secreted by the neuron onto the endocrine cell?
(a) endocytosis (b) parasympathetic autonomic (c) acetylcholine
Compare and contrast autonomic ganglia and CNS nuclei.
Autonomic ganglia—nerve cell bodies of postganglionic autonomic neurons. CNS nuclei—nerve cell bodies in the brain and spinal cord
Varicosity
Autonomic postganglionic axons end with a series of swollen areas at their distal ends, like beads spaced out along a string. Each of these swellings contains vesicles filled with neurotransmitter.
The two varieties of adrenergic receptors are ANSWER: alpha and beta. nicotinic and cholinergic. beta and cholinergic. nicotinic and muscarinic.
alpha and beta.
Which of these characteristics is the same in both the sympathetic and parasympathetic branches for the vast majority of neurons? A. Site of origin of the nerves B. Receptor type at the target tissues C. Postganglionic neurotransmitter D. Preganglionic neurotransmitter
D. Preganglionic neurotransmitter
Autonomic Neurons
control smooth muscle, cardiac muscle, many glands, and some adipose tissue; involuntary
osmoreceptors
respond to osmolarity of blood: water homeostasis
The two divisions of the efferent side of the peripheral nervous system are
somatic motor neurons and autonomic neurons.
Norepinephrine is synthesized in the varicosity from
the amino acid tyrosine (remember its an amino acid hormone, specifically a catecholamine).
sympathetic branch
within the autonomic division of the PNS, responsible for INCREASING arousal. leads to activation of parasympathetic; portion of the peripheral nervous system that prepares the body for action; controls flight or fight response Activation of the sympathetic branch produces =increased heart rate, =pupil dilation, = liver increases blood sugar to provide energy for muscle contraction, = and inhibition of the digestive processes. >>blood diverted to skeletal muscles instead of digestion //however activation of one sympathetic pathway does not automatically activate them all
Walter Cannon's properties of homeostasis:
(1) preservation of the fitness of the internal environment, (2) up-down regulation by tonic control = sweat glands and smooth muscle rely on this (3) antagonistic control -one ANS branch is excitatory and other is inhibitory -sympathetic vs parasympathetic control >>except for sweat glands and smooth muscle which are strictly sympathetic control (4) chemical signals with different effects in different tissues.
Like all other synapses, the NMJ has three components:
(1) the motor neuron's presynaptic axon terminal filled with synaptic vesicles and mitochondria, (2) the synaptic cleft, and (3) the postsynaptic membrane of the skeletal muscle fiber.
multiple system atrophy
(A rare neurological disorder that impairs your body's involuntary (autonomic) functions, including blood pressure, heart rate, bladder function and digestion). CNS control centers for autonomic functions degenerate.
If a target cell's receptor is (use letter), the neuron(s) releasing neurotransmitter onto the receptor must be (use number). (a) nicotinic cholinergic (b) adrenergic α (c) muscarinic cholinergic (d) adrenergic β 1. somatic motor neuron 2. autonomic preganglionic neuron 3. sympathetic postganglionic neuron 4. parasympathetic postganglionic neuron
(a) 1, 2 (b) 3 (c) 4 (d) 3
Ganglia contain the cell bodies of (choose all that apply) (a) somatic motor neurons (b) preganglionic autonomic neurons (c) interneurons (d) postganglionic autonomic neurons (e) sensory neurons
(d) postganglionic autonomic neurons (e) sensory neurons
sympathetic cholinergic neurons.
A few sympathetic postganglionic neurons, such as those that terminate on sweat glands, secrete ACh rather than norepinephrine.
The diffuse release of autonomic neurotransmitter allows for what? How is it different than a junction in the somatic system?
A single postganglionic neuron can affect a large area of target tissue. A less-directed form of communication than that which occurs between a somatic motor neuron and a skeletal muscle.
Match the answers to the questions. A. true only for the sympathetic division B. true only for the parasympathetic division C. true for both divisions It releases norepinephrine at the neuroeffector synapse.
A. true only for the sympathetic division
Match the answers to the questions. A. true only for the sympathetic division B. true only for the parasympathetic division C. true for both divisions The adrenal medulla is closely allied with this system.
A. true only for the sympathetic division
Which nervous system division has parasympathetic and sympathetic branches?
Autonomic division of the efferent nervous system
Match the answers to the questions. A. true only for the sympathetic division B. true only for the parasympathetic division C. true for both divisions It contains cholinergic neurons.
C. true for both divisions
What are the three other sympathetic ganglion located near the descending aorta?
Celiac, superior and inferior mesenteric
Match the following with its description. A. acetylcholine B. norepinephrine C. cholinergic nicotinic receptor D. adrenergic receptor E. cholinergic muscarinic receptor sympathetic tissue receptor
D. adrenergic receptor //come in to varieties =alpha and beta detect catecholamines like tyrosine derived NE =Alpha responds strongly to NE and weakly to Epi =Beta1 respond equally to NE and EPi =Beta 2 respond strongly to EPI and weakly to NE =Beta 3 found on adipose tissue respond strongly to NE and weakly to Epi //all adrenergic recptors are G protein coupled receptors =slower to start and last longer //Beta receptors increase CAMP and trigger phophorylation of of intracellular proteins //Alpha 1 receptors activates phospholipase C =creates IP3 and DAG =DAG initiates cascade that phosphorylates proteins =IP3 opens Ca channels =cause muscle contraction or secretion by exocytosis //Alpha 2 receptors decrease cAMP =cause smooth muscle relaxation =decrease secretion
Diseases and malfunction of the autonomic nervous system are relatively common.
False
Neurotransmitter made in the varicosities is not packaged into synaptic vesicles for storage.
False
The neuromuscular junction includes extensions of Schwann cells that form a thin layer covering the top of the axon terminals. Why?
Insulation for action potential and the cells secrete a variety of chemical signal molecules that play a critical role in the formation and maintenance of neuromuscular junctions.
Antagonistic Control
One autonomic branch is excitatory and the other branch is inhibitory. For example, sympathetic innervation increases heart rate, while parasympathetic stimulation decreases it. Consequently, heart rate can be regulated by altering the relative proportions of sympathetic and parasympathetic control.
The adrenal medulla is often called the modified sympathetic ganglion. Why?
Preganglionic sympathetic neurons project from the spinal cord to the adrenal medulla, where they synapse (so medulla is at the postganlionic site). However, the postganglionic neurons lack the axons that would normally project to target cells. Instead chromaffin cells secrete the neurohormone epinephrine directly into the blood
a- bungarotoxin n binds to nicotinic skeletal muscle receptors but not to those in autonomic ganglia. Why?
Skeletal muscle has isoforms that are inactivated with extended exposure to ACh or other agonists.
The Huaorani Indians of South America use blowguns to shoot darts poisoned with curare at monkeys. Curare is a plant toxin that binds to and inactivates nicotinic ACh receptors. What happens to a monkey struck by one of these darts?
Skeletal muscles would become paralyzed. Monkey could not flee.
Besides the Vagus, what are some other parasympathetic nerves?
Some other cranial nerves including III, VII, IX & X
The afferent division of the nervous system consists of these two parts.
The afferent division consists of sensory receptors and sensory neurons.
Epinephrine and norepinephrine that are released from the adrenal glands affect target tissue for a longer period of time than the same substances released from neurons at their peripheral receptors. Why? ANSWER: -There are no enzymes to break down epinephrine and norepinephrine in the blood and very little in peripheral tissues. -The hormones released from the adrenal glands bind to different receptors than those released from neurons. -The epinephrine and norepinephrine from the adrenal glands are released by sympathetic neurons, whereas parasympathetic neurons release these substances at the effector organs. -The adrenal gland releases larger amounts of the neurotransmitters than the neurons. -The effectors are less sensitive to epinephrine and norepinephrine released by the adrenal glands.
There are no enzymes to break down epinephrine and norepinephrine in the blood and very little in peripheral tissues.
Sympathetic pathways originate in which region of the spinal cord?
Thoracic and lumbar //ganglion run in 2 chains along vertebral column in addition to ganglion in descending aorta =long postganglionic axon project form ganglion to nervous cell =short preganglionic neurons
The concentration of neurotransmitter in a synapse is influenced by its breakdown or removal.
True
autonomic ganglia act as mini-integrating centers.
True
The motor end plate is ANSWER: -a special fibrous matrix whose collagen fibers hold the axon terminal in proper position. -a folded area of muscle cell membrane with ACh receptors clustered at the top of each fold. -the same as the synaptic cleft. -formed by the membrane of enlarged axon terminals, or boutons, that lie on the surface of skeletal muscle cells. -the same as the neuromuscular junction.
a folded area of muscle cell membrane with ACh receptors clustered at the top of each fold.
Cholinergic receptors respond to the neurotransmitter ANSWER: dompamine. acetylcholine. norepinephrine. epinephrine.
acetylcholine.
Somatic motor neurons secrete the neurotransmitter ________ onto ________ receptors at the target tissue.
acetylcholine; nicotinic
Most blood vessels contain one type of ___________ receptor that causes smooth muscle contraction (vasoconstriction). However, some blood vessels also contain a second type of ___________ receptor that causes smooth muscle relaxation (vasodilation). Both receptors are activated by ______________.
adrenergic; adrenergic; catecholamines
The drug Chantix®, which treats nicotine addiction, is an ________ for the nicotine receptor. ANSWER: antagonist agonist
agonist
The division of the efferent nervous system that controls smooth and cardiac muscles and many glands is the ________ division.
autonomic
The presence of two peripheral efferent neurons in a pathway is typical of the ________ division. ANSWER: somatic somatic and autonomic autonomic sensory somatic and sensory
autonomic //sympathetic and parasympathetic consist of 2 neurons in series =preganglionic neuron -from CNS to autonomic ganglion >>usually or 9 enter synpase all for different targets so singal signal may affect a large number of target cell called divergence -synspase with 2nd neuron =postganglionic neuron -has cell body inside ganglion and projects axon to target tissue
Cholinergic nicotinic receptors are found in the ________ of the ANS. ANSWER: central nervous system neuroeffector junctions varicosities autonomic ganglia
autonomic ganglia //preganglionic neurons release ACh onto postganglionic nicotinic AChR receptors =sympathetic postganglionic neurons secrete Norepinepherine onto adrenergic receptros on target cells >>except for sweat glands that secrete ACh not NE =parasympathetic postganglionic neurons secrete ACh onto mucarinic cholinergic receptors on target cells =Some ANS neurons secrete neither NE or ACh -aka nonadrenergic/cholinergic neurons -uses NT like substance P, adenosine, NO, ATP
"Dual innervation" refers to an organ receiving ANSWER: nerves from both the brain and the spinal cord. both sympathetic and parasympathetic nerves. two nerves from the spinal cord. both autonomic and somatomotor nerves. None of the answers are correct.
both sympathetic and parasympathetic nerves.
In addition, sensory information integrated in the _________ ________ and _________ ________ can create emotions that influence autonomic output
cerebral cortex; limbic system
Sweat glands contain ANSWER: alpha receptors. cholinergic receptors. beta receptors. All of the answers are correct. None of the answers are correct.
cholinergic receptors.
Between the axon and the muscle, the synaptic cleft is filled with a fibrous matrix whose ________ ________ hold the axon terminal and the motor end plate in the proper alignment. The matrix also contains _____________, the enzyme that rapidly deactivates ACh by degrading it into acetyl and choline
collagen fibers; acetylcholinesterase (AChE),
The ____________ also contains neurons that act as sensors, such as osmoreceptors, which monitor osmolarity, and thermoreceptors, which monitor body temperature.
hypothalamus
The massive sympathetic discharge that occurs in fightor-flight situations is mediated through the_______________ and is a total-body response to a crisis.
hypothalamus
Sensory information from somatosensory and visceral receptors goes to homeostatic control centers in the ____________ , _______, and ________. These centers monitor and regulate important functions such as =blood pressure, =temperature control =water balance
hypothalamus, pons, medulla //hypothalamus =contains -osmoreceptors >>monitor osmolarity -thermoreceptros >>monitor body temperature
recycled norepinephrine is either repackaged into vesicles or broken down by ___________ ___________ , the main enzyme responsible for degradation of catecholamines.
monoamine oxidase (MAO)
Most postganglionic parasympathetic neurons secrete acetylcholine onto ___________ __________ receptors on the target cell.
muscarinic cholinergic
The efferent division of the________ ________ ________ can be subdivided into ________ ________ ________ , which control skeletal muscles, and autonomic neurons, which control smooth muscle, cardiac muscle, many glands, and some adipose tissue.
peripheral nervous system; somatic motor neurons
The two divisions of the efferent side of the peripheral nervous system are ANSWER: -somatic motor neurons and voluntary neurons. -somatic motor neurons and autonomic neurons. -the sympathetic and parasympathetic divisions. -voluntary nervous system and somatic motor neurons.
somatic motor neurons and autonomic neurons.
The division of the autonomic nervous system that prepares the body for intense levels of activity and stress is the
sympathetic division.
Peripheral Nervous System
the sensory and motor neurons that connect the central nervous system to the rest of the body
In many cases of sympathetic dysfunction, the symptoms are manifested most strongly in the:
*Cardiovascular system*, when diminished sympathetic input to blood vessels results in abnormally low blood pressure. Other prominent symptoms of sympathetic pathology include urinary incontinence, which is the loss of bladder control, and impotence, which is the inability to achieve or sustain a penile erection.
ACh Muscarinic receptors
*Muscarinic receptors are all G protein-coupled receptors*. Receptor activation initiates second messenger pathways, some of which open K+ or Ca2+ channels. The tissue response to activation of a muscarinic receptor varies with the receptor subtype, of which there are at least five. (As a rule, parasympathetic neurons release ACh at their targets.)
nonadrenergic, noncholinergic neurons
A small number of autonomic neurons secrete neither norepinephrine nor acetylcholine. Some of the chemicals they use as neurotransmitters include substance P, somatostatin, vasoactive intestinal peptide (VIP), adenosine, nitric oxide, and ATP. Neurons are assigned to either the sympathetic or parasympathetic branch according to *where their preganglionic fibers leave the nerve cord*.
Adrenal Medulla
A specialized neuroendocrine tissue associated with the *sympathetic nervous system*. It develops from the same embryonic tissue as sympathetic neurons and is a neurosecretory structure It forms the core of the adrenal glands, which sit atop the kidneys. (Like the pituitary gland, each adrenal gland is actually two glands of different embryological origin that fused during development). In response to alarm signals from the CNS, the adrenal medulla releases large amounts of *epinephrine* for general distribution throughout the body as part of a fight-or-flight response.
Match the following with its description. A. acetylcholine B. norepinephrine C. cholinergic nicotinic receptor D. adrenergic receptor E. cholinergic muscarinic receptor released by all autonomic preganglionic neurons
A. acetylcholine
Match the following with its description. A. acetylcholine B. norepinephrine C. cholinergic nicotinic receptor D. adrenergic receptor E. cholinergic muscarinic receptor released by all autonomic preganglionic neurons
A. acetylcholine
Neurons in the parasympathetic pathway use which of the following neurotransmitters? A. acetylcholine B. norepinephrine C. acetylcholine (preganglionic) and norepinephrine (postganglionic) D. norepinephrine (preganglionic) and acetylcholine (postganglionic)
A. acetylcholine //As a rule PS pathways release this =PS have muscarinic AChr receptors >>all G-protein coupled receptors =activates second messenger >>opens Ca and K channels
Match the answers to the questions. A. true only for the sympathetic division B. true only for the parasympathetic division C. true for both divisions It is important during stress or emergencies (fight-or-flight).
A. true only for the sympathetic division
Match the answers to the questions. A. true only for the sympathetic division B. true only for the parasympathetic division C. true for both divisions The ganglia are found in a chain that runs close to the spinal cord or along the descending aorta.
A. true only for the sympathetic division
Explain how the adrenergic beta receptors basically work.
All adrenergic receptors are* G protein-coupled receptors* rather than ion channels. (Slow response from target). The different subtypes use different second messenger pathways. Catecholamine binding to B-receptors *increases cyclic AMP and triggers the phosphorylation of intracellular proteins*. The target cell response then depends on the specific downstream pathway. For example, activation of B1-receptors enhances cardiac muscle contraction, but activation of B2-receptors relaxes smooth muscle in many tissues.
What are the three subtypes of beta receptors?
All are adrenergic receptors. The three main subtypes of beta receptors differ in their affinity for catecholamines. B1- receptors respond *equally strongly* to norepinephrine and epinephrine. B2- receptors are *more sensitive to epinephrine than to norepinephrine*. Interestingly, the *β2-receptors are not innervated* (no sympathetic neurons terminate near them), which limits their exposure to the neurotransmitter norepinephrine. B3- receptors, which are *found primarily on adipose tissue*, are innervated and *more sensitive to norepinephrine than to epinephrine*.
Alpha receptors. What are the two subtypes?
An adrenergic receptor; the most common sympathetic receptor—respond *strongly to norepinephrine and only weakly to epinephrine* . A1: *activate phospholipase C*, creating inositol trisphosphate (IP3) and diacylglycerol (DAG). In general, activation of A1-receptors *causes muscle contraction or secretion by exocytosis*. A2: *decrease intracellular cyclic AMP* and cause *smooth muscle relaxation* (gastrointestinal tract) or* decreased secretion* (pancreas).
Anticholinesterases
Are indirect agonists that block ACh degradation and extend the active life of each ACh molecule. E.g.: The toxic organophosphate insecticides, such as parathion and malathion, kill insects by causing sustained contraction of their breathing muscles so that they suffocate.
In the autonomic division, neurotransmitters are synthesized in the _______ ________.
Axon variscosities.
Match the following with its description. A. acetylcholine B. norepinephrine C. cholinergic nicotinic receptor D. adrenergic receptor E. cholinergic muscarinic receptor primary sympathetic neurotransmitter
B. norepinephrine
Match the answers to the questions. A. true only for the sympathetic division B. true only for the parasympathetic division C. true for both divisions It dominates during resting-and-digesting activities.
B. true only for the parasympathetic division
Match the answers to the questions. A. true only for the sympathetic division B. true only for the parasympathetic division C. true for both divisions The neurotransmitter acetylcholine is released by neurons at the neuroeffector synapse.
B. true only for the parasympathetic division
Match the answers to the questions. A. true only for the sympathetic division B. true only for the parasympathetic division C. true for both divisions The cell bodies of preganglionic neurons are found either in the brain stem or in the sacral region of the spinal cord.
B. true only for the parasympathetic division //originate in brain stem or sacral region =axons leave via cranial nerves >>innervation is in head, neck, and internal organs >>75% of pSN is in Vagus nerve =ganglia located on or near target organs //long preganglionic neuron =short postganglionic neuron
How are skeletal muscle and autonomic ACh receptors different?
Both muscle and neuronal nAChR proteins have five subunits encircling the central pore. However, skeletal muscle has A, B, gamma, and e subunit isoforms, while neuronal nAchR has only the A and B isoforms.
Which of the following is an example of antagonistic control? A. The vagus nerve innervates much of the viscera changing the function of each of them independently of the others. B. Sympathetic stimulation causes renin secretion by the kidneys, but the kidneys are not innervated by the parasympathetic nervous system. C. The parasympathetic stimulation causes bronchoconstriction while sympathetic stimulation causes bronchodilation. D. The parasympathetic nervous system originates from the brain stem and pelvic nerves (cranio-sacral division) while the sympathetic arises from the thoracic and lumbar spinal cord (thoraco-lumbar division).
C. The parasympathetic stimulation causes bronchoconstriction while sympathetic stimulation causes bronchodilation.
Match the answers to the questions. A. true only for the sympathetic division B. true only for the parasympathetic division C. true for both divisions On average, one preganglionic neuron synapses with eight or nine postganglionic neurons, each innervating a different target.
C. true for both divisions
Match the answers to the questions. A. true only for the sympathetic division B. true only for the parasympathetic division C. true for both divisions The neural pathway from the spinal cord to the target tissue has two neurons, the preganglionic neuron and the postganglionic neuron.
C. true for both divisions
Which statements apply to the parasympathetic division of the nervous system? ANSWER: -It is dominant during "resting and digesting." -Its ganglia are nearby, on or near their target organs. -It is dominant during "resting and digesting" and its ganglia are nearby, on or near their target organs. -Epinephrine is the primary neurotransmitter of the parasympathetic division. -All of the statements apply.
It is dominant during "resting and digesting" and its ganglia are nearby, on or near their target organs.
Fight-or-Flight Response
The brain triggers massive simultaneous sympathetic discharge throughout the body. As the body prepares to fight or flee, the heart speeds up; blood vessels to muscles of the arms, legs, and heart dilate; and the liver starts to produce glucose to provide energy for muscle contraction. Digestion becomes a low priority when life and limb are threatened, and so blood is diverted from the gastrointestinal tract to skeletal muscles.
There is no antagonistic innervation to relax skeletal muscles.
True
Parasympathetic branch
The division of the autonomic nervous system that restores the body's normal resting state and conserves energy. division of the autonomic nervous system that is involved in control of GI, cardiac and respiratory systems. one key function of the sympathetic branch is control of blood flow to the tissues. within the autonomic division of the PNS, responsible for DECREASING arousal
vagus nerve (cranial nerve X)
The major *parasympathetic* tract, which contains about 75% of all parasympathetic fibers. This nerve carries *both sensory* information from internal organs to the brain and *parasympathetic output* from the brain to organs.
Besides the vegetative nervous system, the autonomic nervous system is sometimes called the ___________ nervous system. Why is this an appropriate name? List some functions controlled by the autonomic nervous system.
Visceral nervous system because it controls internal organs (viscera) and functions such as heart rate and digestion.
Which area is NOT normally considered to be an autonomic control center? ANSWER: hypothalamus medulla amygdala pons
amygdala
Cocaine
an *indirect agonist* that blocks the reuptake of norepinephrine into adrenergic nerve terminals, thereby extending norepinephrine's excitatory effect on the target. This is demonstrated by the toxic effect of cocaine on the heart, where sympathetic-induced vasoconstriction of the heart's blood vessels can result in a heart attack.
Most internal organs are under____________ control. Exceptions include the ______ _____ and the ________ _______ in most blood vessels. These tissues are innervated only by the sympathetic branch and rely strictly on _________ control
antagonistic; sweat glands; smooth muscle; tonic
Motor output from the ___________ and ________ ________ creates autonomic responses, endocrine responses, and behavioral responses such as drinking, food-seeking, and temperature regulation (getting out of the heat, putting on a sweater). These behavioral responses are integrated in brain centers responsible for ___________ ________ and control of movement.
hypothalamus; brain stem; motivated behaviors
Increased parasympathetic stimulation ANSWER: causes the pupils to dilate. causes sweat glands to release sweat. causes blood vessels in the skin to dilate. increases heart rate. increases gastric motility.
increases gastric motility.
Many drugs used to treat depression are _________ agonists that act either on membrane transporters for neurotransmitters ( tricyclic antidepressants and selective serotonin reuptake inhibitors) or on their metabolism (monoamine oxidase inhibitors).
indirect
Somatic Motor Neurons
innervate skeletal muscles; voluntary //involve one long single axon projecting to skeletal muscle target from CNS //have motor end plates =with nAChR =contains AChE which can rapidly deactivate ACh degrading it into monomers acytl and choline //ACh acting on motor end plate is always excitatory =creates muscle contraction //relaxation occurs when motor neurons are inhibited by CNS preventing ACh release
The adrenal medulla is important to the sympathetic branch of the autonomic nervous system because ANSWER: -it releases epinephrine and norepinephrine directly into the blood. -it is a source of catecholamines, it is considered a modified sympathetic ganglion, and it releases epinephrine and norepinephrine directly into the blood. -it is considered a modified sympathetic ganglion. -it is a source of catecholamines. -it is a source of catecholamines and it is considered a modified sympathetic ganglion.
it is a source of catecholamines, it is considered a modified sympathetic ganglion =releases epinephrine and =norepinephrine directly into the blood. //adrenal medulla secretes EPI primarily =sympathetic branch however =preganglion extends to adrenal medulla, and postganglion is axonless cell body >>thus chromaffin cells secrete NH EPI directly into blood
The release of autonomic neurotransmitters is subject to __________ from a variety of sources. For example, sympathetic varicosities contain receptors for hormones and for paracrines such as _________. Some preganglionic neurons co-secrete ____________ along with acetylcholine.
modulation; histamine; neuropeptides
Which of the following has its cell body in the ganglion? ANSWER: -preganglionic neuron and postganglionic neuron -preganglionic neuron, postganglionic neuron, and somatic motor neuron -somatic motor neuron -preganglionic neuron -postganglionic neuron
postganglionic neuron
The cell bodies of somatic motor neurons are located either in the ventral horn of the ________ ________ or in the _________, with a long single axon projecting to the skeletal muscle target. Somatic motor neurons branch ________ to their targets.
spinal cord; brain; close
These __________ ________ include urination, defecation, and penile erection—body functions that can be influenced by descending pathways from the brain but do not require this input
spinal reflexes //no input from brain
The division of the autonomic nervous system that prepares the body for intense levels of activity and stress is the ANSWER: parasympathetic division. sympathetic division. craniosacral division. somatomotor division. intramural division.
sympathetic division.
The diameter of blood vessels varies under the control of ________ neurons, which cause the diameter to ________.
sympathetic; either increase or decrease, depending upon the type of receptor present
