ANS

Question 1

Afferent division of the nervous system is composed of ____ information from the ____, the ___, and _____.

Answer 1

The Afferent Division is composed of sensory information from the muscles (somatic sensory); the guts (visceral sensory); and special senses to include vision, hearing, balance, taste and smell.

Question 2

The efferent division includes the _____ and _____ systems.

Answer 2

Sympathetic and parasympathetic

Question 3

The ____ division consists of a single neuron between the CNS and skeletal muscle, leading to skeletal muscle innervation and muscle excitation only.

The ____ division has two neuron chains connected by a synapse and innervates smooth and cardiac muscle, GI, and neurons, to which it can be excitatory or inhibitory.

Answer 3

The somatic efferent division consists of a single neuron between the CNS and skeletal muscle, leading to skeletal muscle innervation and muscle excitation only.

The autonomic efferent division has two neuron chains connected by a synapse and innervates smooth and cardiac muscle, GI, and neurons, to which it can be excitatory or inhibitory.

Question 4

Synapses for somatic motor neurons are at ______

Answer 4

neuromuscular junctions

Question 5

What’s a ganglion?

Answer 5

Collection of neuronal cell bodies outside the CNS

Question 6

The postganglionic axon becomes highly branched as it approaches its target. Along the branches are a series of swellings called _______. It is from these that thhe neurotransmitter is released onto the _____.

Answer 6

The postganglionic axon becomes highly branched as it approaches its target. Along the branches are a series of swellings called varicosities. It is from these that thhe neurotransmitter is released onto the target cell.

Question 7

The parasympathetic division is also referred to as the ______ division because the preganglionic neurons are located in the _____ and in the _____ region of the CNS.

Answer 7

The parasympathetic division is also referred to as the craniosacral division because the preganglionic neurons are located in the brainstem and in the sacral region of the CNS.

Question 8

Describe the length and location of neurons in the parasympathetic nervous system:

Answer 8

In parasympathetic division,

Preganglionic neurons are in the brainstem and sacral region and have long axons.

The postganglionic neurons have short axons with body in the periphery.

Question 9

The cell bodies of “cranio” parasympathetic neurons are in the ____ and axons are in the ____.

The cell bodies of “sacro” parasympathetic neurons are in the _____ and axons are in the ____.

Answer 9

The cell bodies of “cranio” parasympathetic neurons are in the brainstem and axons are in the cranial nerves.

The cell bodies of “sacro” parasympathetic neurons are in the sacral spinal cord and axons are in the peripheral nerves.

Question 10

The sympathetic division is also called the _____ division because of the location of the preganglionic cell bodies.

Answer 10

The sympathetic division is also called the thoracolumbar division because of the location of the preganglionic cell bodies.

Question 11

The preganglionic neuron in the sympathetic division has a cell body located in the ______ of the spinal cord. The axon exits via _____ and heads for the sympathetic chain _____, called the ________.

Answer 11

The preganglionic neuron in the sympathetic division has a cell body located in the intermediolateral column of the spinal cord. The axon exits via ventral roots and heads for the sympathetic chain ganglia, called the sympathetic trunk.

Question 12

Describe key sympathetic chain ganglia of the sympathetic division:

Answer 12

•Cervical Ganglia:

• Superior
• Middle
• Inferior
• Ganglia adjacent to thoracic & upper lumbar & sacral segments
• Prevertebral Ganglia:
• Celiac
• Superior Mesenteric
• Inferior Mesenteric

Question 13

What are chromaffin cells?

Answer 13

Modified postganglionic sympathetic neurons located in the adrenal medulla, regulated by the sympathetic nervous system. These cells secrete EPI and NE into the general circulation, regulating endocrine function.

Question 14

Paravertebral ganglia are:

A. the location of postganglionic parasympathetic neuron cell bodies.

B. composed of somatic motor neuron cell bodies.

C. the location of postganglionic sympathetic neuron cell bodies.

D. the location of preganglionic sympathetic neuron cell bodies

Answer 14

C. the location of postganglionic sympathetic neuron cell bodies.

Question 15

The preganglionic parasympathetic neuron releases _____ on ____ receptors.

The postganglionic parasympathetic neuron releases _____ on _____ receptors (located on the effector cell).

Answer 15

The preganglionic parasympathetic neuron releases acetylcholine on nicotinic receptors.

The postganglionic parasympathetic neuron releases acetylcholine on muscarinic receptors (located on the effector cell).

Question 16

The sympathetic preganglionic neuron releases ____ onto _____ receptors.

The sympathetic postganglionic neuron releases ____ onto ___ receptors (on the effector cell).

Answer 16

The sympathetic preganglionic neuron releases Acetylcholine onto nicotinic receptors.

The sympathetic postganglionic neuron releases norepinephrine onto adrenergic receptors (on the effector cell).

Question 17

nicotinic receptors are examples of ______ receptors, while muscarinic and adrenergic receptors are examples of _____ receptors.

Answer 17

nicotinic receptors are examples of ionotropic receptors, while muscarinic and adrenergic receptors are examples of metabotropic receptors.

Question 18

Muscarinic receptors are located in the plasma membrane of

A. postganglionic parasympathetic neuronal cell bodies

B. parasympathetic effector cells

C. postganglionic sympathetic neuronal cell bodies

D. most sympathetic effector cells

Answer 18

B. parasympathetic effector cells

Question 19

What are 3 key exceptions to the standard sympathetic pattern of postganglionic neuron release of NE/EPI onto adrenergic receptors?

Answer 19

Sweat glands - even though innervated by sympathetic system, the postganglionic neurons release ACh, which binds to muscarinic receptors.

Dopamine can be released by postganglionic sympathetic neurons, which binds to a dopamine 1 receptor on renal vasculature smooth muscle.

The adrenal medulla is directly innervated by preganglionic sympathetic fibers, which trigger the medulla to release NE and Epi into bloodstream directly (instead of using a neuron), which then binds to alpha and beta adrenergic receptors.

Question 20

The heart is regulated by ____ and ____ receptors

Answer 20

Beta 1 - stimulates the depolarization of the SA and AV nodes and cardiac myocytes, increasing both chronotropy and inotropy.

M2 - hyperpolarizes these cells, decreasing both chronotropy and inotropy.

Question 21

In glandular tissues, M3 receptors promote ____, while in smooth muscle tissues M3 promotes _____.

Answer 21

In glandular tissues, M3 receptors promote secretions, while in smooth muscle tissues M3 promotes contraction.

Question 22

alpha 1 receptors are located on the peripheral ______, and stimulation causes _____.

Answer 22

alpha 1 receptors are located on the peripheral blood vessels, and stimulation causes vasoconstriction.

Question 23

____ receptors on the SA node cause an increase in heart rate when stimulated.

Answer 23

B1 receptors on the SA node cause an increase in heart rate when stimulated.

Question 24

_____ receptors cause bronchodilation and vasodilation when stimulated.

Answer 24

B2 receptors cause bronchodilation and vasodilation when stimulated.

Question 25

Most of the effects of the a2 receptor result from its location on _______ neuron terminals

Answer 25

Most of the effects of the a2 receptor result from its location on **presynaptic** neuron terminals

Question 26

a2 receptors have important presynaptic and postsynaptic effects. Explain what each are.

Answer 26

**Presynaptically**, a2 inhibits the release of NE from the presynaptic neuron (basically serves as a negative feedback loop to block sympathetic signals) **Postsynaptically**, a2 induces smooth muscle contraction, just like a1

Question 27

Are blood vessels innervated by the sympathetic, parasympathetic, both, or neither?

Answer 27

Sympathetic innervates most blood vessels Parasympathetic innervates most arteries and arterioles, but NOT veins or venules

Question 28

What is meant by parasympathetic discrete control of effectors?

Answer 28

Discrete control means that each organ can be regulated separately, so we can urinate without having our heart rate drop significantly.

Question 29

The sympathetic nervous system is capable of mass \_\_\_\_\_\_, meaning what?

Answer 29

Capable of mass discharge Activation of multiple organ systems concurrently

Question 30

Epocrine sweat glands:

Answer 30

located all over body, function for thermoregulation, postganglionic neurons release ACh; binds to muscarinic receptors on sweat gland target.

Question 31

Appocrine sweat glands:

Answer 31

located in armpits, genitals, perianal; active from puberty onward; adrenergic receptors on sweat gland, may be regulated hormonally (epinephrine in blood stream)

Question 32

What targets are ONLY innervated by the sympathetic nervous system (and not parasympathetic)?

Answer 32

Sweat glands Pilomotor muscles of the skin Arterioles Veins

Question 33

Increased parasympathetic activity promotes ______ of airways.

Answer 33

Constriction (also causes increased bronchial secretions)

Question 34

Describe the sexual response effects of parasympathetic activity:

Answer 34

Male: erection Female: increased blood flow, lubrication

Question 35

Explain the regulation of the detrussor muscle, internal urethral sphincter, and external urethral sphincter via parasympathetic and sympathetic divisions:

Answer 35

Parasympathetic promotes urination - contracts the detrussor muscle causing urge to urinate. Sympathetic inhibits micturation. (somatic is under voluntary control)

Question 36

Compare the sympathetic vs. parasympathetic affects on salivation:

Answer 36

Sympathetic: stimulation promotes thick, mucousy salivary secretions Parasympathetic: stimulation promotes watery secretions

Question 37

Which of the following responses is consistent with a "mass discharge" of sympathetic tone? A. Pupil dilation; ↑ gastric HCl secretion; constriction of internal urethral sphincter B. Pupil constriction; ↑ heart rate; erection C. Pupil dilation; bronchodilation; ejaculation

Answer 37

C. Pupil dilation; bronchodilation; ejaculation

Question 38

What is a reflex?

Answer 38

Involuntary response to a stimulus - cerebral cortex is not directly involved

Question 39

What are the 4 main components of the reflex arc?

Answer 39

–Afferent limb = Sensory limb * Receptor * Afferent pathway –Central Integration Center –Efferent limb = output * Efferent pathway –Effector = Target (muscle, gland) *(reflexes can be neuronal or hormonal)*

Question 40

Explain the reflex arc that occurs in the case of e.g. hemorrhage:

Answer 40

Question 41

Where are baroreceptors located that detect changes in blood pressure and volume?

Answer 41

Aortic arch and carotid sinus

Question 42

Parasympathetic and sympathetic divisions are organized as a ______ chain

Answer 42

Parasympathetic and sympathetic divisions are organized as a **two-neuron** chain

Question 43

\_\_\_\_\_ is released at both parasympathetic and sympathetic preganglionic neurons. The receptors on the post-ganglionic cell are always \_\_\_\_\_.

Answer 43

**ACh** is released at both parasympathetic and sympathetic preganglionic neurons. The receptors on the post-ganglionic cell are always **nicotinic**.

Question 44

Parasympathetic postganglionic neurons release ____ from the postganglionic neuron and binds to ____ \_\_\_\_ receptors on the effector tissue.

Answer 44

Parasympathetic postganglionic neurons release **ACh** from the postganglionic neuron and binds to **muscarinic cholinergic** receptors on the effector tissue.

Question 45

Most sympathetic postganglionic neurons release ______ onto their effector tissues. The receptors are _____ receptors.

Answer 45

Most sympathetic postganglionic neurons release **norepinephrine** onto their effector tissues. The receptors are **adrenergic** receptors.

Question 46

The adrenal gland is a modified ____ neuron. It releases ____ and \_\_\_\_.

Answer 46

The adrenal gland is a modified **postganglionic** neuron. It releases **norepinephrine** and **epinephrine**.

Question 47

Autonomic reflex arcs include the **\_\_\_\_\_** reflex which helps to maintain blood pressure and volume.

Answer 47

Autonomic reflex arcs include the **baroreceptor** reflex which helps to maintain blood pressure and volume.

Question 48

Autonomic reflex arcs include the baroreceptor reflex which helps to maintain _____ and \_\_\_\_\_\_.

Answer 48

Autonomic reflex arcs include the baroreceptor reflex which helps to maintain **blood pressure** and **volume.**

Question 49

The ANS regulates the function of involuntary muscle (smooth and cardiac) and \_\_\_\_\_

Answer 49

glands

Question 50

Label as sympathetic and parasympathetic

Answer 50

Question 51

Which receptors are GPCRs - parasympathetic, sympathetic, both, or neither?

Answer 51

Both.

Question 52

What organs have M2 vs. M3 receptors?

Answer 52

M2 - HEART!!!!! M3 - eye, salivary glands, lungs, stomach, bladder

Question 53

What adrenergic receptor(s) are located on the eye?

Answer 53

a1 and B2

Question 54

What adrenergic receptor(s) control the salivary glands?

Answer 54

B2

Question 55

What adrenergic receptor(s) control the stomach?

Answer 55

B2

Question 56

What adrenergic receptor(s) control the bladder?

Answer 56

a1 and B2

Question 57

What organs are controlled via B2 receptors?

Answer 57

Eyes Salivary glands Lungs Stomach Bladder

Question 58

What organs are controlled via a1 receptors?

Answer 58

Eye Bladder *(both are also controlled via B2 and M3 receptors)*

Question 59

What receptors (adrenergic and cholinergic) control the eye?

Answer 59

M3 (cholinergic) a1 and B2 (adrenergic)

Question 60

What receptors (adrenergic and cholinergic) control the salivary glands?

Answer 60

M3 (cholinergic) B2 (adrenergic)

Question 61

What receptors (adrenergic and cholinergic) control the lungs?

Answer 61

M3 (cholinergic) B2 (adrenergic)

Question 62

What receptors (adrenergic and cholinergic) control the stomach?

Answer 62

M3 B2

Question 63

What receptors (adrenergic and cholinergic) control the bladder?

Answer 63

M3 a1 B2

Question 64

The ___ receptor inhibits the SA/AV node and cardiac muscle

Answer 64

M2

Question 65

The M3 receptor promotes ____ and \_\_\_\_.

Answer 65

Secretion Smooth muscle contraction

Question 66

Which adrenergic receptor promotes smooth muscle contraction?

Answer 66

a1 (and somewhat a2)

Question 67

Which receptor stimulates the SA/AV node and cardiac muscle?

Answer 67

B1 receptors

Question 68

Stimulation of which receptor promotes smooth muscle relaxation?

Answer 68

B2 receptors

Question 69

Which adrenergic/cholinergic receptors are Gq type GPCRs, and what are their signaling pathways?

Answer 69

M3 and a1 Gq --\> PLC --\> Ca++

Question 70

Which adrenergic/cholinergic receptors are Gi type GPCRs, and what are their signaling pathways?

Answer 70

M2 and a2 Gi --\> AC --\> cAMP

Question 71

Which adrenergic/cholinergic receptors are Gs type GPCRs, and what are their signaling pathways?

Answer 71

B1 and B2 Gs --\> AC --\> cAMP

Question 72

Are toxicities more common with parasympathetic or sympathetic drugs?

Answer 72

Parasympathetic Most PS drugs are non-selective (vs. sympathetic drugs are selective). *Route of administration of PS drugs is important*

Question 73

How do M2 and B1 receptors regulate heart rate?

Answer 73

Question 74

M2 agonists _____ cardiac output. M2 antagonists ____ cardiac output.

Answer 74

M2 agonists **reduce** cardiac output. M2 antagonists **increase** cardiac output.

Question 75

Atropine is a ___ \_\_\_ (receptor type, agonist/antagonist). What is its ultimate effect?

Answer 75

Atropine is an **M2 antagonist** Ultimately increases cardiac output and elevates heart rate (also used to reverse cholinesterase poisoning)

Question 76

B1 agonists _____ cardiac output. B1 antagonists ____ cardiac output.

Answer 76

B1 agonists **increase** cardiac output. B1 antagonists **decrease** cardiac output.

Question 77

Metoprolol, Carvedilol, and Nadolol are B1 ______ thus they ____ cardiac output.

Answer 77

Metoprolol, Carvedilol, and Nadolol are B1 **antagonists** thus they **decrease** cardiac output.

Question 78

Dobutamine and Isoproterenol are B1 ____ thus they ____ cardiac output.

Answer 78

Dobutamine and Isoproterenol are B1 **agonists** thus they **increase** cardiac output.

Question 79

In the lungs, stimulation of ___ receptors promotes bronchoconstriction while stimulation of ___ receptors promotes bronchodilation.

Answer 79

In the lungs, stimulation of **M3** receptors promotes bronchoconstriction while stimulation of **B2** receptors promotes bronchodilation.

Question 80

Methacholine is an M3 \_\_\_\_\_, meaning it promotes broncho\_\_\_\_\_.

Answer 80

Methacholine is an M3 **agonist**, meaning it promotes broncho**constriction**.

Question 81

Ipratropium, Tiotropium, Glycopyrrolate, Aclidinium, and Umeclidinium are M3 \_\_\_\_\_\_, thus they promote broncho\_\_\_\_.

Answer 81

Ipratropium, Tiotropium, Glycopyrrolate, Aclidinium, and Umeclidinium are M3 **antagonists**, thus they promote broncho**dilation**.

Question 82

Albuterol, Salmeterol, Formoterol, Indacaterol, and Epinephrine are B2 \_\_\_\_, thus they promote broncho\_\_\_\_\_.

Answer 82

Albuterol, Salmeterol, Formoterol, Indacaterol, and Epinephrine are B2 **agonists**, thus they promote broncho**dilation.**

Question 83

The detrussor muscle of the bladder is controlled via ____ receptors that promote detrussor contraction and ____ receptors that promote detrussor relaxation.

Answer 83

The detrussor muscle of the bladder is controlled via **M3** receptors that promote detrussor contraction and **B2** receptors that promote detrussor relaxation. ## Footnote *(also controlled by a1 receptors - promotes urethral contraction)*

Question 84

Bethanachol is an M3 \_\_\_\_, thus causes urinary \_\_\_\_.

Answer 84

Bethanachol is an M3 **agonist**, thus causes urinary **urgency**.

Question 85

Oxybutynin, Solifenacin, and Tolterodine are M3 \_\_\_\_\_\_, thus promote urinary \_\_\_\_\_\_.

Answer 85

Oxybutynin, Solifenacin, and Tolterodine are M3 **antagonists**, thus promote urinary **retention**.

Question 86

Terazosin, Doxazosin, and Tamsulosin are a1 \_\_\_\_\_\_, thus promote urinary \_\_\_\_\_.

Answer 86

Terazosin, Doxazosin, and Tamsulosin are a1 **antagonists**, thus promote urinary **urgency**. ## Footnote *Tamsulosin is used to treat BPH, which causes an enlarged prostate blocking urine flow.*

Question 87

GI tract stimulation of M3 receptors promotes GI smooth muscle \_\_\_\_\_\_. GI tract stimulation of B2 receptors promotes GI smooth muscle \_\_\_\_\_\_.

Answer 87

GI tract stimulation of M3 receptors promotes GI smooth muscle **contraction**. GI tract stimulation of B2 receptors promotes GI smooth muscle **relaxation**.

Question 88

Dicyclomine and Hyocyamine are M3 \_\_\_\_\_, thus they INCREASE/REDUCE peristalsis.

Answer 88

Dicyclomine and Hyocyamine are M3 **antagonists**, thus they INCREASE/REDUCE peristalsis. ## Footnote *(used to treat IBS)*

Question 89

Stimulation of M3 receptors promotes _____ saliva secretion. Stimulation of B2 receptors promotes ____ saliva secretion.

Answer 89

Stimulation of M3 receptors promotes **watery** saliva secretion. Stimulation of B2 receptors promotes **thick** saliva secretion.

Question 90

Stimulation of ___ receptors promotes watery saliva secretion. Stimulation of ___ receptors promotes thick saliva secretion.

Answer 90

Stimulation of **M3** receptors promotes watery saliva secretion. Stimulation of **B2** receptors promotes thick saliva secretion.

Question 91

Pilocarpine is an M3 \_\_\_\_, stimulating ___ saliva production. Glycopyrrolate is an M3 \_\_\_\_, stimulating ___ saliva production.

Answer 91

Pilocarpine is an M3 **agonist**, stimulating **watery** saliva production. Glycopyrrolate is an M3 **antagonist**, stimulating **thick** saliva production. *(Pilocarpine is used for Sjogren's syndrome)*

Question 92

Stimulation of M3 promotes eye \_\_\_\_\_, whereas stimulation of a1 promotes eye \_\_\_\_\_.

Answer 92

Stimulation of M3 promotes eye **constriction**, whereas stimulation of a1 promotes eye **dilation**.

Question 93

Atropine is an M3 **\_\_\_\_**, so it promotes pupil **\_\_\_\_**. Carbachol is an M3 **\_\_\_\_**, so it promotes pupil **\_\_\_\_**.

Answer 93

Atropine is an M3 **antagonist**, so it promotes pupil **dilation**. Carbachol is an M3 **agonist**, so it promotes pupil **constriction**.

Question 94

Uterine smooth muscle contraction is regulated by ___ and ___ (cholinergic and/or adrenergic receptors).

Answer 94

Uterine smooth muscle contraction is regulated by **M3** and **B2.**

Question 95

M3 promotes uterine \_\_\_\_\_. B2 promotes uterine \_\_\_\_\_.

Answer 95

M3 promotes uterine **contraction**. B2 promotes uterine **relaxation**.

Question 96

Terbutaline is a B2 \_\_\_\_, and is used to promote uterine \_\_\_\_.

Answer 96

Terbutaline is a B2 **agonist**, and is used to promote uterine **relaxation**. ## Footnote *(Given to slow down premature labor)*

Question 97

What receptors regulate vascular constriction?

Answer 97

a1 and B2 NO parasympathetic stimulation

Question 98

a1 promotes vaso\_\_\_\_\_\_; B2 promotes vaso\_\_\_\_\_.

Answer 98

a1 promotes vasoconstriction; B2 promotes vasodilation.

Question 99

Midodrine is an a1 \_\_\_\_, thus it promotes vaso\_\_\_\_\_.

Answer 99

Midodrine is an a1 **agonist**, thus it promotes vaso**constriction**.

Question 100

Prazosin, Terazosin, and Doxazosin are a1 \_\_\_\_\_, thus they promote vaso\_\_\_\_.

Answer 100

Prazosin, Terazosin, and Doxazosin are a1 **antagonists**, thus they promote vaso**dilation**.

Question 101

Sympathetic stimulation causes a positive dromotropic and positive chronotropic effect. What does this mean?

Answer 101

Positive dromotropic effect = increased conduction velocity of action potentials Positive chronotropic effect = increased heart rate

Question 102

What is the major effect of sympathetic stimulation of the SA node?

Answer 102

Faster rate of phase 4 depolarization

Question 103

Parasympathetic stimulation of SA node causes a ___ chronotropic and a ___ dromotropic effect.

Answer 103

Parasympathetic stimulation of SA node causes a **negative** chronotropic and a **negative** dromotropic effect. AKA decreased HR (negative chronotropic) decreased conduction velocity (negative dromotropic)

Question 104

Parasympathetic stimulation increases SA nodal permeability to \_\_\_.

Answer 104

Parasympathetic stimulation increases SA nodal permeability to **potassium**. ## Footnote *(results in hyperpolarization)*

Question 105

Sympathetic stimulation of the SA node increases the open state probability of ___ channels.

Answer 105

Sympathetic stimulation of the SA node increases the open state probability of **HCN** channels. ## Footnote *(these allow Na entry - causes depolarization. Also increases permeability of T-type and L-type Ca++ channels)*

Question 106

Sympathetic stimulation increases rate of cardiac muscle ____ and \_\_\_\_.

Answer 106

Sympathetic stimulation increases rate of cardiac muscle **tension** and **relaxation**. ## Footnote *(increases tension/contraction via increased L-type Ca++ channel (DHP channel) permeability. Increased relaxation by increasing activity of SERCA pumps - this makes the myocyte ready for another depolarization aka contraction sooner)*

Question 107

Answer 107

B. Dobutamine, a beta-1 adrenergic receptor agonist

Question 108

HR and SV are controlled by ____ receptors. Vascular tone aka SVR is controlled by ___ receptors (and less so by ___ receptors).

Answer 108

HR and SV are controlled by **B1** receptors. Vascular tone aka SVR is controlled by **a1** receptors (and less so by **B2** receptors). *a1 receptors promote vasoconstriction and B2 receptors promote vasodilation.*

Question 109

List two important synthetic B agonists and two important endogenous B agonists:

Answer 109

Synthetic: * Dobutamine (B1 \> B2) * Isoproterenol (B1 & B2) Endogenous: * Norepinephrine * Epinephrine

Question 110

What is the most important difference between EPI and NE?

Answer 110

The low affinity of NE for the B2-AR. Otherwise, both have a very similar affinity for B1 and a1/a2 receptors.

Question 111

Answer 111

A. Metoprolol, a beta-1 adrenergic receptor antagonist

Question 112

The primary effect of B1-AR stimulation in SA nodal cells is to increase the rate of _____ depolarization, which increases \_\_\_\_\_.

Answer 112

The primary effect of B1-AR stimulation in SA nodal cells is to increase the rate of **Phase 4** depolarization, which increases **heart rate**.

Question 113

Answer 113

D. Phenylephrine, an alpha-1 adrenergic receptor agonist ## Footnote *(Phenylephrine, like NE, is purely an alpha-1 antagonist)*

Question 114

Answer 114

C. Atropine, a muscarinic (M2) receptor antagonist