Efferent division - autonomic NS

what kind of control info does autonomic division carry? what are the two divisions of the autonomic NS? where is the integrating center?

• involuntary control

• Sympathetic and parasympathetic

• integrating center in the brainstem

what is the two-neuron chain of the ANS?

• preganglionic fiber (with cell body in lateral horn of CNS)

• and postganglionic fiber (ending in varicosities - bulges on end of elongated process, synapsing onto effector organ)

are the synapses in autonomic NS considered 1:1? why?

NO, one fiber will cover very large surface of effector organ (due to varicosities), result = organ responds to one signal as a unit

what accounts for the difference in parasympathetic and sympathetic autonomic NS?

the location of the neurons themselves in the body

Sympathetic nerve chains - where does each neuron have cell body, what does it secrete?

• preganglionic

  • cell body in of thoracic/lumbar regions

  • short

  • secrete ACh (cholinergic)

• postganglionic

  • cell body close to spinal cord

  • secrete norepinphrine (adinergic)

Parasympathetic nerve chains - where does each neuron have cell body, what does it secrete?

preganglionic

• cell body in cranial and sacral region

• long

• secretes Ach

Postganglionic

• cell body in terminal ganglia, close to effector organs

• secrete ACh

what is sympathetic dominance? parasympathetic dominance?

sympathetic dominance: prepares body for fight or flight

parasympathetic dominance: rest and digest

how do the PNS and SNS form a dual control system, innervating both the same organs but having opposite effects?

hint: tone

work on a dimmer switch, when one needs to be more dominant, it turns up (firing rate increases), and the other turns down

work by adjusting baseline (TONIC) levels

how does sympathetic nervous system affect the heart and the lungs?

heart: HR increases so more blood can be brought to tissues

lungs: opens to let more air in

what is the effect of the SNS on the liver?

glycogen release and breakdown into glucose for energy

what is special about the adrenal medulla?

is a modified sympathetic ganglion (no postganglionic fibers)

is an endocrine organ - when stimulated, releases norepinephrine (20%) and epinephrine (80%) into blood stream

what are the two types of adinergeic (ACh) receptors in the autonomic NS? from which system (parasympathetic or sympathetic)? are they fast or slow?

Nicotinic (ACh)

• receive ACh from symp and parasymp preganglionic fibers, are located on cell bodies of PostG

• cationic - fast entry, fast response

Muscarinic (ACh)

• receives ACh from parasymp postG, are located on cell membrane of receptor organ

• activate second messenger systems (G-proteins), slow

what are the two types of adrenergic (Norepinephrine) receptors in the autonomic NS? from which system (parasympathetic or sympathetic)? are they fast or slow?

alpha receptors (1 in smooth blood vessels, 2 in brain)

beta receptors (1 in cardiac, 2 in respiratory smooth muscle, 3 in adipose tissue)

use different 2nd messenger system

elicit either excitatory or inhibitory responses

• alpha 1 and beta 1 = excitatory

• alpha 2 and beta 2 = inhibitory