Lecture 24: The Autonomic Nervous System Flashcards
Homeostasis
Dynamic balance between the autonomic branches (sympathetic and parasympathetic)
Sympathetic Nervous System
Fight or flight
Parasympathetic Nervous System
Rest and digest
Visceral Reflexes
Happens in spinal cord
Viscera
Where autonomic, polysynaptic reflexes are initiated
Automatic Motor Responses
Doesn’t go to brain, no cognition
Higher Order
In brain stem, hypothalamus (mostly)
What functions do higher order contain control centers and nuclei for?
Salivation + swallowing, digestive secretions, peristalsis, urinary retention
What responses do the pons, hypothalamus and medulla initiate?
Autonomic, endocrine, and behavioral responses
How are autonomic functions regulated?
Tonic v antagonistic control
Most autonomic regulation is:
Antagonistic
except for sweat glands, smooth muscle dilation
ANS general anatomy
Two neurons (preganglionic and postganglionic) that synapse in an autonomic ganglion
Where do sympathetic pathways originate from?
Thoracic and L1-L2 region of spinal cord
Where do parasympathetic pathways originate from?
Brain stem and sacral region of spinal cord
Are sympathetic pathway ganglia closer to the spinal cord or target?
Spinal cord
Are parasympathetic pathway ganglia closer to the spinal cord or target?
Target
Length of sympathetic pathway neurons
Short pre-ganglionic neuron, long post-ganglionic neuron
Length of parasympathetic pathway neurons
Long pre-ganglionic neuron, short post-ganglionic neuron
What type of receptors do sympathetic pathways have?
Adrenergic receptors
What does the post-ganglionic neuron of the sympathetic pathway secrete to the receptor on the target tissue?
Norepinephrine
What type of receptors do parasympathetic pathways have?
Muscarinic
What does the post-ganglionic neuron of the parasympathetic pathway secrete to the receptor on the target tissue?
ACh
Dual Innervation of most organs
Balance between parasympathetic and sympathetic activity
Increase of activity in one couple to decrease in other
Autonomic tone
Resting level of activity even without stimulation
Nerves can increase of decrease activity quickly
Nicotinic Receptors
Ionotropic, ion channels
Cation non-selective, produces EPSP
Muscarinic Receptors
GPCR, series of second messengers that opens up K+ (IPSP) and Ca2+ channels (EPSP)
Vagus Nerve
75% of all parasympathetic outflow
Innervates structures in neck, thoracic and abdominopelvic cavities including distal portion of large intestine
Sympathetic Chain
Adjacent to vertebral column
Collateral Ganglia
Anterior of Vertebral bodies
