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Pharm > Intro to the ANS > Flashcards

Intro to the ANS Flashcards

1
Q

Indications for ANS drugs

A 
HYPERTENSION
SHOCK 
NASAL CONGESTION
ANGINA
ARRHYTHMIAS
ASTHMA
PARKINSON’S
GLAUCOMA
GI DYSFUNCTION
BLADDER DYSFUNCTION
WEIGHT REDUCTION

Many drugs have autonomic nervous system side effects

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2
Q

Properties of ANS drugs

A

Most ANS drugs have peripheral effects.
Some cross the blood brain and modulate CNS receptors (i.e. have central effects).
Some drugs act at the neuromuscular junction.

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3
Q

Peripheral Nervous System

A

The peripheral nervous system (PNS) refers to nerves outside the spinal cord and brain
Two Major Divisions
1) Somatic = Motor neurons send signals to skeletal muscle to control voluntary movement
2) ANS = Neurons of the autonomic nervous system send signals to organs & glands – involuntary control

Subdivisions of the ANS
Parasympathetic
Sympathetic

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4
Q

Structural features of the ANS

A

AUTONOMOUS, INVOLUNTARY

GANGLIA OUTSIDE THE CNS

AFFERENT/EFFERENT NEURONS

A REFLEX SYSTEM

AFFERENT - PERIPHERAL SENSORY “RECEPTORS”

CNS CONTROL LARGELY BRAINSTEM AND HYPOTHALAMUS

EFFERENT – TWO NEURON RELAY (GANGLION) TO RECEPTORS ON TARGET ORGANS

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5
Q

Preganglionic

A

A neuron with a cell body in the CNS and axon extending to a ganglion in the periphery

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6
Q

Postganglionic

A

A neuron with a cell body in a peripheral ganglion and axon extending to a target tissue

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7
Q

Neurotransmitters and receptors

A

Acetylcholine (Ach)

    • Cholinergic
    • Muscarinic & Nicotinic receptors

Norepinephrine (NE)

    • Adrenergic
    • Alpha (a) and beta (b) receptors

Epinephrine (Epi)

    • Adrenergic
    • Actually a hormone since it is released into the blood
    • Alpha (a) and beta (b) receptors

Dopamine (DA)

    • Dopaminergic
    • Renal vascular smooth muscle (+CNS)
    • Dopaminergic receptors (D1, D2, D3, D4, D5)
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8
Q

Cholinergic

A

refers to acetylcholine (ACh)
Nerves that release ACh are cholinergic
Receptors activated by ACh are cholinergic
– Nicotinic and muscarinic
Drugs that effect neurotransmission by Ach

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9
Q

Adrenergic

A

refers to norepinephrine (NE) from neurons and epinephrine from adrenal medulla
Epinephrine = adrenaline –> adrenergic
Nerves that release NE are adrenergic
Receptors activated by NE are adrenergic
Alpha (a) and Beta (b)
Drugs that effect neurotransmission by NE

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10
Q

Cholinergic Neurons

A

Cholinergic fibers synthesize, store and release acetylcholine (Ach)
Preganglionic fibers in all ganglia
Postganglionic Parasympathetic fibers to glands, smooth and cardiac muscle
Postganglionic fibers to thermoregulatory
sweat glands
Motor fibers to striated muscle

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11
Q

Adrenergic Neurons

A

Adrenergic fibers synthesize, store and release norepinephrine (NE)
Post-ganglionic sympathetic fibers to smooth muscle, heart and glands
Note that chromaffin cells in the adrenal medulla are modified ganglion cells and release primarily epinephrine (Epi) into the circulation.

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12
Q

Divisions of the ANS

A

SYMPATHETIC

    • THORACOLUMBAR
    • ENERGY EXPENDING
    • “FIGHT OR FLIGHT”
    • Adrenal medulla

PARASYMPATHETIC

    • CRANIOSACRAL
    • 3RD, 7TH, 9TH AND 10TH CRANIAL NERVES
    • ENERGY CONSERVING
    • “REST AND DIGEST”
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13
Q

Regulation by the ANS

A

PS and S systems often (not always) oppose each other
Some exceptions:
– Salivary and sweat glands (both cause secretion)
– Ciliary muscles (both cause contraction)
– Male sexual response (PS erection, S ejaculation)

Usually some tone in both systems. Tone in each system increased or decreased to balance function relative to ongoing activity of the body

When both systems are maximally activated, PS effects are usually predominant

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14
Q

Parasympathetic System

A

Discrete, localized discharge

  • Long preganglionic neurons, short postganglionic neurons, ganglia within or near target organ
    • Cranial - sacral outflow from CNS

Rest & Digest

    • Slows heart rate, lowers blood pressure
    • Stimulate GI movements and secretions
    • Aids absorption of nutrients
    • Protects retina from excessive light
    • Empties the bladder and rectum

Cholinergic neurons both preganglionic & postganglionic
Responses on end organs mediated viamuscarinic cholinergic receptors

Receptors on postganglionic parasympathetic neurons are nicotinic cholinergic receptors
(Also less important muscarinic receptors present)

Cells of target organ have muscarinic cholinergic receptors that mediate the responses to ACh released from postganglionic PS neurons

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15
Q

Sympathetic system discharge

A

Very diffuse discharge possible

Outflow from T1 to L2-3 segment of spinal cord

Synapse with neurons lying in sympathetic ganglia

  • Paravertebral sympathetic ganglia (22 pairs)
  • Prevertebral ganglia in abdomen and pelvis – celiac, superior mesenteric, aorticorenal, and inferior mesenteric
  • Terminal ganglia – near end organs – urinary bladder, rectum, cervical ganglia

Epinephrine released from adrenal medulla during exercise, excitement, anger, fear

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16
Q

Sympathetic neuron types

A

Preganglionic sympathetic neurons are cholinergic (ACh)

Postganglionic sympathetic neurons are adrenergic (NE)

    • Exception is sympathetic neurons to sweat glands – these sympathetic neurons are cholinergic, i.e., release Ach
    • Exception is specialized neurons innervating afferent arterioles of kidney – these neurons release dopamine which causes relaxation of the vascular smooth muscle & vasodilation by activating D1 dopamine receptors

Adrenal medulla is like a modified ganglia – no axons, instead releases Epi into blood
- Preganglionic fibers to adrenal medulla are cholinergic

17
Q

Fight or Flight

A

(NE & Epi)
Heart rate increases, blood pressure rises
RBCs poured into blood from spleen to carry more O2
Blood flow shifted from skin and splanchnic region to skeletal muscles
Blood glucose rises
Bronchioles and pupils dilate
Brain receives signals to facilitate purposeful responses & to imprint the event in memory

18
Q

Adrenergic receptors

A

alpha 1 and 2

Beta 1, 2, and 3

19
Q

Summarize the ANS responses in the heart

A

B1- adrenergic response increases heart rate, contractile force, and conduction velocity. Muscarinic/ cholinergic response decreases rate and conduction velocity.

20
Q

Summarize the ANS responses in the eye

A

Pupil Size:

alpha 1- adrenergic response constricts radial muscle causing dilation (mydriasis)

cholinergic response causes contraction of circular muscle (miosis)

Accomodation: no sympathetic innervation.
parasympathetic- contraction of ciliary muscle producing accommodation for near vision.

“The Silly (ciliary) Circus (circular) is Parasympathetic.”

21
Q

Bronchial smooth muscle responses

A

Beta 2 receptor. Sympathetic response: relaxation. Parasympathetic: contrTION

22
Q

Blood vessel ANS responses

A

alpha 1 receptor. Sympathetic response: constriction
Parasympathetic: no innervation EXCEPT in skeletal muscle blood vessels (dilates)

Beta 2 receptor also found in skeletal muscle

Beta receptor also in Beta Coronary vessels.

23
Q

GI tract ANS responses

A

alpha 2, Beta 2

sympathetic: decreases
parasympathetic: increases

24
Q

Sphincter ANS responses

A

alpha receptors

symp: contracts
parasymp: relaxes

25
Q

Splenic capsule ANS responses

A

alpha 1 receptor

symp: contracts
parasymp: no innervation

26
Q

Urinary bladder ANS responses

A

detrusor muscle: Beta receptor

  • symp: relaxes
  • parasymp: contracts

trigone-sphincter: alpha 1 receptor.

  • symp: contracts
  • parasymp: relaxes
27
Q

Uterus ANS responses

A

alpha 1 and beta 2

sympathetic response: contraction-rleaxation
parasympathetic response- contraction-relaxation

28
Q

Glycogenolysis ANS responses

A

no parasympathetic response.

Sympathetic increases in skeletal muscle via Beta receptors
- in liver via alpha 1 and beta 2

29
Q

Lipollysis ANS responses

A

beta 1 and beta 2 receptors, increased by sympathetic response. No paraysmp.

30
Q

Renin secretion ANS responses

A

Beta 1 receptor
increased by sympathetic

no parasymp

31
Q

Insulin secretion ANS responses

A

alpha 2 and beta 2 receptors

sympathetic response decreases and increases

parasympathetic response increases

32
Q

Rules of Thumb - Smooth muscle

A

Alpha1 (a1) Receptors
Stimulate contraction of all smooth muscle
Vascular smooth muscle Vasoconstriction
Glandular smooth muscle

Beta2 (b2) Receptors
Relax smooth muscle

Muscarinic Cholinergic Receptors:
Contract smooth muscle
–Apparent discrepancy – ACh & muscarinic agonists given IV cause vasodilation, due to release of nitric oxide (NO)
Different intracellular signal than a1 receptors

Pharm (14 decks)

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