Chapter 11 The Nervous System: Autonomic and Motor Systems

Which of the following is located between the invaginations of the motor end plate of a neuromuscular junction?

Acetylcholinesterase

The gray ramus is comprised of what fiber type?

C

How does latroxin, the venom of the black widow spider, cause muscle spasms and rigidity.

It stimulates acetylcholine release from motor neurons.

Which of the following statements is TRUE of communication across the neuromuscular junction?

The end-plate potential is always of sufficient magnitude to depolarize the muscle cell to threshold to initiate an action potential.

Dual innervation of organs by the autonomic nervous system refers to the observation that ________.

both sympathetic and parasympathetic neurons innervate most organs

The somatic nervous system regulates the activity of ________.

skeletal muscle

The autonomic nervous system innervates all the following effector organs and tissues except ________.

skeletal muscles

Which of the following neurons of the efferent branch of the peripheral nervous system does NOT release acetylcholine?

sympathetic postganglionic neuron

The balance between sympathetic and parasympathetic activity is modified primarily by

the activity of the body

Which of the following structures of an autonomic neuron is NOT located within the ganglion?

the cell body of preganglionic neurons

Which of the following best describes the general arrangement of the efferent limb of the autonomic nervous system?

two neurons in series

The presence of ________ within varicosities mediate the release of neurotransmitter

voltage-gated Ca2+ channels

Which of the following are indicative of the relative release of catecholamines from the adrenal medulla?

80% epinephrine : 20% norepinephrine

What is the neurotransmitter released from motor neurons?

Acetylcholine

The steps of synaptic transmission at the motor end plate are listed below, out of order. Choose the correct order. 1. Acetylcholine binds to postsynaptic receptors. 2. Acetylcholine is released by exocytosis. 3. A graded depolarization is produced. 4. An action potential is produced on the muscle cell membrane. 5. Channels for both sodium and potassium are opened. 6. Voltage-dependent calcium channels on the plasma membrane open. 7. An action potential arrives at the axon terminal.

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At rest, what is the relative contribution of the sympathetic and parasympathetic nervous systems to the regulation of homeostasis?

Both systems are active but the parasympathetic predominates.

When the body is stressed, what is the relative contribution of the sympathetic and parasympathetic nervous systems to the regulation of homeostasis?

Both systems are active but the sympathetic predominates.

Which of the following descriptions of collateral ganglia is true?

Collateral ganglia are in the sympathetic nervous system but distinct from the sympathetic chain, and they function as a site of communication between sympathetic preganglionic neurons and postganglionic neurons.

What is the graded change in membrane potential that occurs at the motor end plate of skeletal muscle called?

End-plate potential

Which of the following descriptions is TRUE for the parasympathetic nervous system, but NOT the sympathetic nervous system?

Postganglionic fibers release acetylcholine

Parasympathetic neurons from which cranial nerve innervate most of the viscera in the thoracic and abdominal cavities?

X

What cells of the adrenal medulla release epinephrine?

chromaffin cells

Which of the following cranial nerves does NOT include parasympathetic nerves?

V - trigeminal nerve

What are swellings of postganglionic autonomic axons from which neurotransmitters are released called?

Varicosities

What type of channels that are present within the varicosities of autonomic neurons are absent from the axon terminal of other neurons?

Voltage-gated Na+ and K+ channels

With respect to their innervation, individual skeletal muscle fibers (cells) are innervated by ________.

a single motor neuron

Parasympathetic preganglionic neurons release the neurotransmitter ________; sympathetic preganglionic neurons release the neurotransmitter ________.

acetylcholine : acetylcholine

Parasympathetic postganglionic neurons release the neurotransmitter ________; sympathetic postganglionic neurons release the neurotransmitter ________.

acetylcholine : norepinephrine

What enzyme degrades the neurotransmitter released from varicosities of parasympathetic postganglionic neurons?

acetylcholinesterase

Which of the following endocrine glands is innervated by sympathetic preganglionic neurons?

adrenal medulla

Activation of which class of adrenergic receptor will result in calcium release from intracellular stores?

alpha1 only

Actions at which class of adrenergic receptor generally have excitatory effects?

alpha1, alpha2, beta1, and beta3

Activation of which class of adrenergic receptor decreases the cytosolic levels of cAMP?

alpha2 only

What class of adrenergic receptor activates the enzyme adenylate cyclase?

beta1, beta2, and beta3

Compared to norepinephrine, epinephrine has a greater affinity for what type of receptor?

beta2

Where are most of the autonomic nervous system control centers located?

brainstem

Where in the central nervous system do the preganglionic neurons of the parasympathetic nervous system originate?

brainstem and sacral region of the spinal cord

Which of the regions of the brain listed below is NOT involved in the control of the autonomic nervous system?

cerebellum

Parasympathetic preganglionic neurons travel in what nerves?

cranial and pelvic nerves

The opening of a cation channel that allows both Na+ and K+ to move through will cause the membrane to ________ because of the ________.

depolarize : greater Na+ electrochemical gradient as compared with K+

Which of the following does NOT have nicotinic cholinergic receptors?

effector organs for the parasympathetic nervous system

Which of the following physiological responses are associated with an elevation in parasympathetic nervous system activity?

enhanced absorption of nutrients

What area of the brain initiates the fight-or-flight response by producing widespread activation of the sympathetic nervous system?

hypothalamus

Which of the following physiological responses are associated with elevated sympathetic nervous system activity?

increased contractile force of the heart

Within the autonomic ganglia, what are the cells that modulate the flow of information to the target organ called?

intrinsic neurons

In what class of neuron and within what organelle is the enzyme monoamine oxidase located?

mitochondria of sympathetic postganglionic neurons

Mismatches between vestibular, visual, and proprioceptive sensory inputs activate the autonomic nervous system, leading to symptoms that are characteristic of ________.

motion sickness

Where on skeletal muscle is the highest density of nicotinic receptors?

motor end plate

What cholinergic receptors are coupled to G proteins?

muscarinic

Binding of acetylcholine to ________ receptors causes a ________ by opening channels that permit both sodium and potassium to permeate the membrane.

nicotinic : depolarization

Which class of autonomic nervous system receptors is ionotropic?

nicotinic cholinergic

• What are the steps at the neuroeffector junctions?

o Action potential arrives at varicosity o Voltage-gated Ca2+ channels open o Ca2+ triggers exocytosis of neurotransmitter o Neurotransmitter binds with receptors on effector organ o Response in effector organ o Neurotransmitter degraded, diffuses away, reuptake

• What are the two classes of andrenergic receptors and what are their properties?

o Alpha receptors (alpha1, alpha2) o Beta receptors (beta1, beta2, beta3)

• How do the autonomic and somatic systems differ in their type of stimulation to the effector?

o Autonomic is the part of the peripheral nervous system that controls visceral functions that occur below the level of consciousness. (parasympathetic and sympathetic) o Somatic is the part of the peripheral nervous system associated with the voluntary control of body movements through the skeletal muscles and mediation of involuntary reflex arcs.

• What is the name of the sympathetic ganglia and where are they located?

o Collateral ganglia: outside the chain

• Can most autonomic processes be consciously controlled?

o Controlled without conscious control, act or occur involuntarily

• What organs are innervated only by the sympathetic nervous system?

o Kidney, arrector pili, adrenal, sweat glands, and most blood vessels

• What neurotransmitter does a motor neuron release? Receptor type on muscle cell?

o Motor neuron releases acetylcholine, binds to receptors in the motor end plate

• Define the roles of the sympathetic and parasympathetic divisions of the ANS.

o Parasympathetic - rest and digest (digestive, heart rate, breathing rate) the part of the autonomic nervous system that controls functions of the body at rest. It helps maintain homeostasis in the body. It causes muscles to relax and heart rate to decrease. o Sympathetic - (fight, flight, fear) the part of the autonomic nervous system that prepares the body to react to stresses such as threat or injury. It causes muscles to contract and heart rate to increase.

• How do the preganglionic and postganglionic neurons differ in the ANS?

o Preganglionic neurons originates in the brainstem or the spinal cord, and the second set o Postganglionic neurons lies outside the central nervous system in collections of nerve cells called autonomic ganglia

• What kind of neurotransmitters are used in the ANS? Are they excitatory or inhibitory? What does this depend on?

o Preganglionic neurons- release acetylcholine o Parasympathetic postganglionic neurons - only release acetylcholine o Sympathetic postganglionic neurons- release nor epinephrine

• Define dual innervation.

o Receiving instructions from both sympathetic and parasympathetic divisions

• What processes are controlled by the parasympathetic NS?

o Rest, quiet relaxed states o Active in "rest and digest"

• What is a motor unit

o a skeletal muscle neuron plus all the muscle fibers it innervates constitutes a

• Do all organs have dual innervation?

o most organs of the body by the sympathetic (on the left) and parasympathetic (on the right) divisions of the ANS have dual innervation o although some-including the adrenal medulla, arrector pili muscles, sweat glands, and most blood vessels-receive only sympathetic innervation

Which of the following contributes to the ability of the sympathetic nervous system to produce widespread responses within the body?

one preganglionic neuron sends collaterals to multiple ganglia, affecting multiple postganglionic neurons

• How do the somatic and autonomic systems differ in respect to motor neurons? Where do they connect?

see study guide

Where do the preganglionic neurons of the sympathetic nervous system emerge from the spinal cord?

thoracic and lumbar regions

Sympathetic preganglionic neurons exit the spinal nerve via the ________ before they enter the ________.

white ramus : ganglion of the sympathetic trunk

Which of the following is NOT a visceral reflex?

withdrawal reflex

Binding of norepinephrine to what type of receptor will trigger the activation of phospholipase C?

α 1

What type of receptor agonists are used to treat people suffering from asthma or nasal congestion?

β2