Autonomic nervous system

Nicotinic vs Muscarinic

- Nicotinic receptors are found in:The somatic nervous system (neuromuscular junctions in skeletal muscles). The sympathetic and parasympathetic nervous system (autonomic ganglia). -Muscarini receptors are found in: brain, heart, smooth muscle or the parasympathetic nervous system -muscarinic type being G-protein coupled receptors (GPCRs) that mediate a slow metabolic response via second messenger cascades, while the nicotinic type are ligand-gated ion channels that mediate a fast synaptic transmission of the neurotransmitter

What are the neurotransmitters of the ANS?

2 Majors: Norephinephrine / Epinephrine Acetylcholine others neurotransmitters which are also postganglionic parasympathetic neurons of the gastrointestinal tract (GI) -Substance p -vasoactive intestinal peptide (VIP) -nitric oxide (NO)

A 12-year-old girl with acute asthma exacerbation is given albuterol, a b-agonist sympathomimetic agent. 4. What is the mechanism of action when these receptors are stimulated in the correct sequence of events? A) Activation of Gs protein, stimulation of adenylate cyclase, increased cAMP B) Increased cAMP, activation of Gs protein, and stimulation of adenylate cyclase

A) Activation of Gs protein, stimulation of adenylate cyclase, increased cAMP

A 12-year-old girl with acute asthma exacerbation is given albuterol, a b-agonist sympathomimetic agent. 5. Under normal physiological conditions, which neurotransmitter would stimulate the post-ganglion fiber? A) acetylcholine B) dopamine C) norepinephrine D) epinephrine

A) acetylcholine keyword: "stimulate"

Beta2 receptor agonists are used to treat which of the following conditions? A. Asthma B. Myasthenia gravis C. Heart failure D. Insecticide poisoning

A-Asthma

Which of the following is the neurotransmitter in autonomic ganglia? A. Acetylcholine B. Norepinephrine C. Epinephrine D. Dopamine

A-acetylcholine

Which of the following nerve fibers are contained in the gray ramus? A. Postganglionic sympathetic fibers B. Preganglionic parasympathetic fibers C. Postganglionic parasympathetic fibers D. Preganglionic sympathetic fibers

A-postganglionic sympathetic fibers Gray ramus (or gray ramus communicants) = paravertebral chian

Which of the following receptors is found in both the sympathetic and parasympathetic ganglia? A. Nicotinic B. Muscarinic C. Adrenergic D. Dopaminergic

A. Nicotinic

Nicotinic receptors are found on which of the following nerve cells? A. Sympathetic effector cells B. Sympathetic ganglionic cells C. Parasympathetic effector cells D. All of the above

B-sympathetic ganglionic cells Sympathetic effector cells = adrenergic receptors Parasympathetic effector cells = muscarinic receptors

The application of a solution containing atropine to the eye will result in which of the following? A. Pupillary constriction B. An inability to focus on objects close at hand C. Ptosis D. Amblyopia

B. An inability to focus on objects close at hand atropine = antagonist of muscarinic receptors

Albuterol is expected to: A. constrict bronchioles B. relax bronchioles C. act on alpha receptors D. act on non-adrenergic receptors

B. relax bronchioles

A 12-year-old girl with acute asthma exacerbation is given albuterol, a b-agonist sympathomimetic agent. 3. What neurotransmitter normally activate receptors on post-ganglionic sympathetic targets? A) acetylcholine B) dopamine C) norepinephrine D) serotonin

C) norepinephrine keyword: "targets" = effector organs

Which of the following receptor types mediates an increase in heart rate and contractility? A. Alpha 1 receptors B. Alpha 2 receptors C. Beta 1 receptors D. Beta 2 receptors

C-beta 1 receptors

Which drug stimulates beta1 and beta2 receptors? A. Phenoxybenzamine B. Albuterol C. Isoproterenol D. Reserpine

C-isoproterenol used to treat bradicardia (slow heart rate) by increasing heart rate

6. Which of the following contains pre- and post-ganglionic fibers? A. CNS - central nervous system B. PNS - Peripheral nervous system C. ANS - Autonomic nervous system D. SNS - Somatic nervous system

C. ANS - Autonomic nervous system

A 12-year-old girl with acute asthma exacerbation is given albuterol, a b-agonist sympathomimetic agent. 2. What ANS receptor does this medication target? A) Nicotinic B) Muscarinic C) alpha adrenergic D) beta adrenergic

D) beta adrenergic

A 12-year-old girl with acute asthma exacerbation is given albuterol, a b-agonist sympathomimetic agent. 1. What is the target organ/tissue for this medication? A) GI wall B) SA node C) skeletal muscle, D) bronchial smooth muscle

D) bronchial smooth muscle

Selective destruction of the right superior cervical ganglion would result in which of the following? A. A dilated pupil in the right eye B. A dilated pupil in the left eye C. A fixed non-accommodating lens in the right eye D. A constricted pupil in the right eye

D- a constricted pupil in the right eye

7. Which of the following system innervate skeletal muscles? A. CNS - central nervous system B. PNS - Peripheral nervous system C. ANS - Autonomic nervous system D. SNS - Somatic nervous system E. ENS - Enteric nervous system

D. SNS - Somatic nervous system

Parasympathetic affect to the heart rate & conduction velocity

Decreases heart rate & conduction velocity Fewer action potentials occur per min because the threshold potential is reached more slowly and, therefore, less frequently The mechanism: ACh greatly increases the permeability of the fiber membranes to potassium ions, which causes increased negativity inside fiber (less excitable).

Adrenergic receptors

Epinephrine / Norepinephrine Alpha 1 & 2 Beta 1 & 2

Control of ANS

Hypothalamus - controls efferent ANS activity (as well as the secretion of hormones by the pituitary gland) Brain stem, particularly the medulla coordinate basic homeostatic functions; controls cardiovascular, respiratory and GI systems

Muscarinic receptors MOA

In the heart SA node, agonist (Ach) binds and activates Gi protein = inhibition of adenylate cyclase = decreased cAMP =opening of K+ channels, slowing of the rate of spontaneous depolarization and decreased heart rate (bradycardia). In smooth muscle and glands, activation of Gq protein, stimulation of phospholipase C, increases in IP3 and intracellular Ca2+

Muscarinic receptors

Location: Heart (M2), smooth muscle (M3), and glands (M3). Agonist: ACh or muscarine Agonist binding: Inhibitory in the heart; decrease heart rate, decrease conduction velocity in AV node. Excitatory in smooth muscle and glands; example, in bronchial muscle, cause contraction and in the GI system, causes increased motility and increase secretion of GI juices. Antagonist: atropine

A1 receptors

Location: Vascular smooth muscles of the skin, GI tract, bladder sphincters and radial muscles of the iris Agonist binding (NE): Excitation. Contraction of radial muscles of the iris = dilation of the pupils to allow more light to enter the eye. The blood vessels in skin are constricted = decreased blood flow = maintaining body heat Constrict bladder and GI sphincters Mechanism: Activation of Gq protein = stimulation of phospholipase C = increases in inositol 1,4,5-triposphate (IP3) and intracellular calcium

Nicotinic receptors

Location: autonomic ganglia (Nn) of parasympathetic and sympathetic nervous system, neuromuscular junction (Nm), and the adrenal medulla Agonist: ACh or nicotine Agonist binding: Excitation. Antagonist: hexamethonium (at the autonomic ganglia) Mechanism: agonist binds to the a subunit of the nicotinic ACh receptor. These receptors are also ion channels for Na2+ and K+

B2 receptors

Location: vascular smooth muscle of skeletal muscle, bronchial smooth muscle and wall of GI tract and bladder Agonist binding (NE) : Relaxation. Dilation of vascular smooth muscle, dilation of bronchioles, relaxation of bladder wall, decrease GI secretion Mechanism: Activation of Gs protein = stimulation of adenylate cyclase = increased cAMP = relaxation of bronchial smooth muscle leading to bronchodilation

A2 receptors

Location: wall of the GI tract Agonist binding (NE) : Inhibition. Inhibition of GI secretion, reduced GI motility Mechanism: Gi protein activation, which leads to inhibition of adenylate cyclase and decreases in cyclic adenosine monophosphate (cAMP).

Functions of ANS

Maintenance of body homeostasis - e.g. blood pressure Integration of the stress response - e.g. response to fight or flight Integration of visceral function - e.g. coordination of organs in the digestive system after ingestion of food

Cholinergic receptors

Nicotinic Muscarinic

Sympathetic effects on heart rate and conduction velocity

Norepinephrine (NE) is the neurotransmitter, acting at β1 receptors. Increases heart rate & conduction velocity More action potentials occur per min because the threshold potential is reached more quickly and, therefore, more frequently. The mechanism: increases the permeability of fiber membrane to Na+ and Ca2+, causing more positive resting potential.

Autonomic System

Pathways to and from the CNS that innervates and regulates smooth muscles, cardiac muscles and glands. Distinct from somatic nervous system (SNS) that innervates skeletal muscle

THE ADRENAL MEDULLA -AN ENDOCRINE GLAND

Regarded as a modified postganglionic sympathetic neurons Preganglionic fibers synapse directly on chromaffin cells in the adrenal medulla and secrete ACh The chromaffin cells secrete epinephrine and norepinephrine (4:1) into the circulation

Output systems from the CNS

Somatic motor system -skeletal muscles ANS motor system - controls involuntary functions

3 divisions of the ANS:

Sympathetic Parasympathetic Enteric

ANS Effects

Sympathetic and parasympathetic systems usually have opposite effects on visceral targets.

B1 receptors

Sympathetic stimulation Location: sinoatrial (SA) node, atrioventricular (AV) node and ventricular muscle of heart Agonist binding (NE) : Excitation. Increase heart rate (Tachycardia), increase AV conduction velocity, and increase contraction Mechanism: Activation of Gs protein = stimulation of adenylate cyclase = increased cAMP

Activation of parasympathetic system

enhances functions of organs that are active during quiescent (inactivity) states (rest and digestive functions) often mediates actions opposite to those of the sympathetic system in homeostatic reflexes (eg, baroreceptor reflex)

Activation of the sympathetic system

enhances the capacity for immediate physical activity (eg, exercise and fight or flight responses) responses to physiological emergencies such as hemorrhage

Norephinephrine / Epinephrine

released by adrenergic neurons that are sympathetic postganglionic neurons.

Acetylcholine

released by cholinergic neurons that are also sympathetic and parasympathetic preganglionic fibers and parasympathetic postganglionic fibers.