Autonomic Nervous System

Question 1

Parasympathetic v. Sympathetic

Answer 1

• Sympathetic: Fight or flight

- Parasympathetic: Rest and digest

Question 2

Origin of ANS nerves and relationship to target organs

Answer 2

Parasympathetic: Cranial and sacral nerves
*ganglia near target organs (1:1 ratio)
Sympathetic: Throacic/Lumbar nerves
*ganglia far from target organs (1:20 ratio)

Question 3

ANS effect on Eyes

Answer 3

Parasympathetic: circular muscle contraction
*Miosis (constrict)
Sympathetic: radial muscle contraction
*Mydriasis (dilates)

Question 4

ANS effect on lacrimal glands

Answer 4

Parasympathetic: tear formation
Sympathetic: ?

Question 5

ANS Salivary gland effects

Answer 5

Parasympathetic: increased saliva production
Sympathetic: Decreased saliva production

Question 6

ANS effect on Heart

Answer 6

Parasympathetic:
   -Decreased HR
   -decreased automaticity 
   -decreased conduction velocity  
Sympathetic:
   -Increased HR
   -Increased automaticity
   -Increased conduction velocity
   -increased contraction force

Question 7

ANS effect on lungs

Answer 7

Parasympathetic: Bronchiocontriction
Sympathetic: bronchiodilation

Question 8

ANS effects on Blood vessels

Answer 8

Parasympathetic: Dilation but not via actual innervation
Sympathetic: Increased constriction
-except skeletal muscle and liver: increased dilation

Question 9

ANS effect on Sweat Glands

Answer 9

Parasympathetic: Some local secretion
Sympathetic: increased activation and generalized secretion

Question 10

ANS effect on Stomach

Answer 10

Parasympathetic: Increased activity and peristalsis
Sympathetic: Decreased activity

Question 11

ANS effect on Liver

Answer 11

Parasympathetic: ?
Sympathetic: Increased glucose release and glycogenolysis

Question 12

ANS effect on Spleen

Answer 12

Parasympathetic

Sympathetic: blood release

Question 13

ANS effect on Small intestines

Answer 13

Parasympathetic: Increased activity
Sympathetic: decreased activity

Question 14

ANS effect on Colon

Answer 14

Parasympathetic: increased peristalsis
Sympathetic: decreased peristalsis

Question 15

ANS effect on Kidney

Answer 15

Parasympathetic: increased urine output
Sympathetic: decreased urine output

Question 16

ANS effect on Bladder

Answer 16

Parasympathetic: open sphincter and urination occurs
Sympathetic: closed sphincter

Question 17

ANS effect on Rectum

Answer 17

Parasympathetic: Active and voiding
Sympathetic: Closed and inactive

Question 18

ANS effect on Genitals

Answer 18

Parasympathetic: Erection
Sympathetic: Ejaculation

Question 19

ANS effect on adrenal medulla

Answer 19

Parasympathetic

Sympathetic: epinephrine released

Question 20

Neurotransmitters released by the ANS

Answer 20

Parasympathetic: ACh
Sympathetic: Epi and NE

Question 21

Cholinergic Receptor Subtypes

Answer 21

Muscarinic Receptors:
-There are 5 G- protein coupled muscarinic receptor subtypes:
-M1, M3, & M5 žincrease IP3;
-M2 &M4ž decrease cAMP&Ÿ increase opening of K+ channels
Nicotinic Receptors:
-receptors of autonomic ganglia (nAChRN nicotinic receptors)
-Receptors of skeletal muscle (nAChRM nicotinic receptors)
-not identical since they respond differently to certain stimulating and blocking agents.

Question 22

Synthesis of Catecholamines – Steps in enzymatic synthesis

Answer 22

Tyrosine->Dopa->Dopamine->NE->Epi

Question 23

Catecholamine Uptake Mechanism

Answer 23

active transport

1. Intraneuronal vesicular transport – from cytoplasm into storage granules, requires ATP & Mg2+
   
   • blocked by reserpine.
2. Neuronal membrane transport across the axoplasmic membrane from the extracellular fluid to the cytoplasm by NET
   
   • blocked by cocaine and the tricyclic antidepressants.

Question 24

Direct v. Indirect Catecholamines

Answer 24

• Direct- agents that exert their effects by interacting with the post-synaptic adrenergic receptor
• Indirect- actions that are dependent on endogenous catecholamines by either:
  
  1. displacement of stored catecholamines, these agents must by transported into the nerve terminal via neuronal membrane transporters (ex. amphetamine)
     
     2. inhibition of the uptake of released catecholamines (ex. cocaine)

Question 25

Termination of the Effects of Adrenergic Stimulation

Answer 25

1. Re-uptake of NE into nerve terminals via neuronal membrane transport is the major mechanism in most organs (exception, blood vessels where enzymatic breakdown & diffusion terminate the action).
2. Dilution by diffusion out of junctional cleft
3. Metabolic transformation
   -Monoamine oxidase (MAO) is associated with mitochondria. Isoenzymes of MAO: MAO A & B are in periphery, MAO B is predominant in CNS.
   -Catechol-O-methyl transferase (COMT) is located in the cytoplasm. COMT in the liver is particularly
   important in terminating the actions of circulating endogenous & administered catecholamines.