Exam 4 - Lecture 33, Intro to ANS

Question 1

Central Nervous system

Answer 1

Main control centers for conscious thought and all body activities

Brain: located in cranial cavity

Spinal Cord: located in vertebral cavity

Question 2

Peripheral nervous system

Answer 2

connects CNS with organs and glands

12 pairs of cranial nerves
31 pairs of spinal nerves

Question 3

Miosis of pupil

Answer 3

Parasympathetic stimulation

Caused by activation of M3-R leads to constriction of the circular muscle

Acetylcholine, opiates and opioids cause

Question 4

Mydriasis

Answer 4

Sympathatic stimulation

Caused by activation of a1-R leads to constriction of radial muscle

Adrenaline, Anticholinergics, Cocaine, Amphetamine, Hallucinogens cause

Question 5

PNS subdivided into

Answer 5

Sensory (afferent) nerves and motor (efferent) nerves

Question 6

Two types of motor nerves

Answer 6

Somatic NS for voluntary contraction of skeletal muscles

Autonomic NS regulate involuntary control of smooth, cardiac muscles and glands

Question 7

Autonomic NS has two branches

Answer 7

Sympathetic and parasympathetic

Sympathetic stimulates tissues
Parasympathetic inhibit tissues

Question 8

Simplified scheme of ANS organization

Answer 8

CNS (Preganglionic neuron, almost always ACh, released onto nicotinic receptors)

Peripheral ganglion (Postganglionic neuron, AChi, NE released onto M/a,b receptors…onto target cell)

Question 9

Somatic system

Answer 9

Typically monosynaptic, ACh to N1 receptors

Heavily myelinated axon

Effect: Stimulatory

Effector organs: Skeletal muscle

Question 10

Sympathetic system

Answer 10

Preganglionic neuron releases ACh onto N2-Rs

Lightly myelinated

Most neurons release NE onto adrenergic GPCRs (alpha and beta)

Question 11

Parasympathetic system

Answer 11

Preganglionic neuron release ACh onto N2-Rs

Lightly myelinated

Most neurons release ACh onto muscarinic GPCRs (M1 - M5)

Question 12

Function of ANS

Answer 12

with endocrine system, regulates activity of most internal organs by innervating smooth muscle, cardiac muscle and glands

Independent of thought

Question 13

Characteristics of ANS

Answer 13

controls involuntary or reflex activities

Typically 2 neuron chain, Preganglionic neurons originate in brain or spinal cord, postganglionic neurons originate in ganglion located outside the CNS

Question 14

Gross Anatomy of ANS - Parasympathetic

Answer 14

Preganglionic fibers are long

Postganglionic fibers are short

Fibers originate in brain stem (cranial) or Sacral

Ganglia are within or near visceral effector organs

Question 15

Gross Anatomy of ANS - Sympathetic

Answer 15

Preganglionic fibers are short

Postganglionic fibers are long

Fibers originate in thoracic and lumbar spinal cord

Ganglia are close to spinal cord

Question 16

Sympathetic Nervous system

Answer 16

Generally stimulates the effector organ

Can be activated in emergencies, fight or flight reaction

Question 17

Key facts Sympathetic nervous system

Answer 17

Preganglionic fibers produce ACh (cholinergic fiber), and Postganglionic produce NE (adrenergic fiber)

Short pre-, long post-ganglionic fibers

Question 18

Key facts Parasympathetic nervous system

Answer 18

Most pre- and post-ganglionic fibers produce ACh (cholinergic)

Long pre-, short post-ganglionic fibers

Question 19

Generalized noradrenergic junction

Answer 19

1. tyrosine enters via Na+ dependent carrier
2. tyrosine converted to dopamine
3. Dopamine and related amines enter vesicles via VMAT
4. Dopamine converted to NE by DBH
5. Vesicles with NE (and other signaling molecules) released into synaptic cleft
6. NE activated postsynaptic adrenoreceptors
7. NE diffuses away and is taken back up into presynaptic neuron by NET

Question 20

Alpha GPCR

Answer 20

Alpha-1 receptors (Gaq coupled)

Alpha-2 receptors (Gai coupled

Question 21

Alpha-1 receptors

Answer 21

Gaq coupled

Mediate fight or flight response
cause constriction of blood vessels (control BP)

inhibit motility in gut by contracting sphincter muscles and relaxing non-sphincter tissue

Mobilize energy by breaking down liver glycogen to glucose

Question 22

Alpha-2 receptors

Answer 22

Gai coupled

Presynaptic, provide feedback control for neurotransmitter release (decrease Ca2+ influx to decrease release of transmitter)

Question 23

Beta GPCR

Answer 23

Beta-1 receptors (Gas coupled)

Beta-2 receptors (Gas coupled0

Question 24

Beta-1 receptors

Answer 24

Cardiac, inotropic, chronotropic

Smooth muscle relaxation in the gut

Question 25

Beta-2 receptors

Answer 25

Induce bronchodilaton

Induce smooth muscle relaxation in the gut

Induce conversion glycogen to glucose

Stimulate secretion of insulin from the pancreas

Question 26

Generalized cholinergic junction

Answer 26

1. Choline transported into presynaptic nerve terminal by Na dependent CHT
2. ACh synthesized from choline and acetly Co-A by ChAT
3. ACh enters vesicles via VAT
4. Release of vesicles requires increased intracellular Ca2+ flux through Nav channels in response to depolarization
5. ACh and other signaling molecules interact with postsynaptic receptors
6. ACh diffuses to presynaptic auto receptors and is metabolized by aceylcholinesterase

Question 27

Nicotinic Receptors

Answer 27

Excitatory cation channels, cause membrane depolarization

Respond in milisec, not as fast as Na

Question 28

Muscarinic receptors

Answer 28

All GPCRs

Effect depends on subtype and target organ

M1,M3,M5, coupled to Gaq

M2,M4 coupled to Gai

Question 29

Two important points

Answer 29

some postganglionic neurons (sympathetic and parasympathetic) have both nicotinic and muscarinic receptors

Some neurons are neither cholinergic or adrenergic

Question 30

Sympathetic neurons signaling via NE, ATP and Neuropeptide Y

Answer 30

3 Phases of contraction in vascular smooth muscle

1. ATP binds P2X purinoceptor (cation channel)
   Depolarization opens CaV -> Up [Ca2+] -> contraction, calcium is from outside (Rapid response)
2. Ne -> a1-Rs -> Gaq -> PLC -> Up IP3 -> [Ca2+] -> contraction. Calcium is form internal store (Moderately fast response)
3. Neuropeptide Y acts at the Y1 receptor to cause slow contraction; mechanism is unclear (Slowest response)

Question 31

Parasympathetic neuron signaling using ACh, VIP and NO

Answer 31

two phases of relaxation in vascular smooth muscle

1. Neuron releases NO, which diffuses to muscle cell. ACh binds to M3-R on endothelial cells, leading to more NO production from eNOS (endothelial nitric oxide synthase). The NO activates guanylate cyclase in the muscle cell, generating cGMP and promoting relaxation.
2. Neuropeptide VIP binds the VIP receptor which activates Gas -> Increase Adenylyl Cyclase (AC) -> Increase cAMP -> Increase PKA -> Decrease [Ca2+] -> decrease contraction

Question 32

M2-R pathway

Answer 32

Gai -> Up GaB -> Up K+ current via GIRK/Kir3 channels (hyper polarization)

Gai -> Down Adenylyl Cyclase -> Down cAMP -> Down PKA

Question 33

Exception 1: some postganglionic neurons (sympathetic and parasympathetic) have both nicotinic and (multiple) muscarinic receptors

Answer 33

Activating M1 slower than M2, N causes Spike EPSP…..M1 responsible for slow EPSP, Peptides can cause Later, slow EPSP. M2 cause IPSP

Question 34

Exception 1: some postganglionic neurons (sympathetic and parasympathetic) have both nicotinic and (multiple) muscarinic receptors

Answer 34

Activating M1 slower than M2, N causes Spike EPSP…..M1 responsible for slow EPSP, Peptides can cause Later, slow EPSP. M2 cause IPSP

Question 35

Reflexes in ANS

Answer 35

Stimulus

1. Receptor in Viscera
2. Visceral sensory neuron
3. Integration center
4. Motor neuron
5. Visceral effector

Response

Question 36

Eye Example

Answer 36

Lens focuses light onto Fovea in the back of eye

Myopia - Focal point in front of Fovea

Hyperopia - Focal point behind Fovea

Question 37

Astigmatism

Answer 37

Light ends up off of the Focal point

Question 38

M1

Answer 38

slow EPSP

Question 39

M2

Answer 39

IPSP

Question 40

Peptides

Answer 40

Late, slow EPSP