Physiology of Autonomic Nervous System

Question 1

Structures involved in central control of ANS

Answer 1

• Spinal cord
• Brain stem (medulla oblongata)
• Hypothalamus
• Cerebral cortex

Question 2

Spinal cord role in ANS control

Answer 2

• reflex changes in blood pressure
• sweat production
• micturition (urine production)

Question 3

Brain stem role in ANS control

Answer 3

• Medulla oblongata controls:
• blood pressure
• respiration.

Question 4

Hypothalmus role in ANS control

Answer 4

• principal locus of integration
• body temperature
• water balance
• carbohydrate metabolism
• sexual reflexes
• autonomic emotional responses

Question 5

Cerebral cortex role in ANS control

Answer 5

• volitional changes
• conditioned autonomic responses

Question 6

Primary neurotransmitters (+roles) & receptors of the parasympathetic nervous system

Answer 6

• Acetylcholine (ACh)
• Preganglionic neurons release ACh
• In the ganglia Ach interacts with _neuronal-type nicotinic cholinergic receptors _(NNRs or neuronal-type nAChRs).
• Postganglionic neurons release AChIn the end organs Ach interacts with _muscarinic cholinergic receptors (_MRs or mAChRs).

Question 7

Primary neurotransmitters (+roles) & receptors of the sympathetic nervous system

Answer 7

• Acetylcholine (ACh)
  
  • Preganglionic neurons release ACh
  • In the ganglia and adrenal medulla ACh interacts with neuronal-type nicotinic cholinergic receptors(NNRs).
• Norepinephrine (NE)
  
  • Postganglionic neurons generally release the catecholamine NE.
  • Exceptions:
    
    • Adrenal medulla releases primarily epinephrine (EPI)
    • Postganglionic neurons innervating sweat glands release ACh.
    • Postganglionic neurons innervating renal vasculature release dopamine (DA).
  • @ end organs NE and EPI interact with a- and b-adrenergic receptors.

Question 8

Major divisions (+general goals) of ANS

Answer 8

• Parasympathetic nervous system (“rest and digest”): general goal—conserve and restore energy
• Sympathetic nervous system (“fight or flight”): generally discharges as a unit in response to an acute stress.

Question 9

General physiological response generated by parasympathetic nervous system (7)

Answer 9

• ↑salivary gland secretion; ↑lacrimal gland secretion (tears); ↑bronchial gland secretion
• miosis (constriction of the pupil; iris circular muscle) and accommodation (focusing for near vision; ciliary muscles)
• ↓heart rate (bradycardia)
  
  • ↓conduction at the S-A node indirectly ↓blood pressure.
• Constriction of bronchioles
• ↑GI absorption; ↑GI motility; relaxation of sphincters; ↑GI secretions.
• ↑urinary tract motility; relaxation of sphincters; bladder contraction.

Question 10

General physiological response generated by sympathetic nervous system (6)

Answer 10

• ↑Heart rate (tachycardia); ↑force of cardiac contractility
• ↑total peripheral resistance (vasoconstriction) resulting in ↑blood pressure.
• ↑blood glucose; ↑lipolysis
• Mydriasis (dilation of the pupil; iris radial muscle)
• Dilation of bronchioles
• controls of tone in blood vessels

Question 11

Mechanisms by which drugs alter activity of ANS (5)

Answer 11

• Mimicking the neurotransmitter action
• Blocking the neurotransmitter action
• Changing the normal action of the neurotransmitter by altering:
  
  • Synthesis of the neurotransmitter
  • Release of the neurotransmitter
  • Inactivation of the neurotransmitter following release