WEEK 6: 6.3 The Autonomic Nervous System Flashcards
What are different sections of the body that are activated by the sympathetic nervous system that are not activated by the parasympathetic NS?
The sweat glands,
arrector pili which lead to erection of hair,
blood vessels, skin and splanchnic which contract, blood vessels-skeletal muscle which relax
How many neuronal pathways does the ANS follow?
2 (2-neuron chain) from the CNS to effector organs
What are these 2 neuron chain?
The pre-ganglionic neurons which originate in the brain/spinal cord & the post-ganglionic neurons which originate in ganglion outside the CNS
How many neuronal pathways does the Somatic NS follow?
1 neuron from the CNS to effector organs
What kind of effect can the SNS have VS ANS
SNS: a stimulatory and voluntary effect
ANS: a stimulatory/inhibitory involuntary effect
What neurotransmitter does the somatic motor system use to communicate with skeletal muscles?
Ach (acetylcholine)
What neurotransmitter does the sympathetic NS use to communicate with various organs?
Primarily norepinephrine, but when communicating with sweat glands, Ach
What neurotransmitter does the parasympathetic NS use to communicate with various organs?
Ach
What are the target organ receptors of the sympathetic NS
alpha receptors (1/2)
- smooth muscle contraction (alpha 1)
Beta receptors (1,2,3)
- smooth muscle relaxation (b2)3
- cardiac muscle contraction (b1)
Muscarinic receptor
- sweat glands
what is the anatomy in terms of fibers that compose a neuronal pathway of the sympathetic NS?
a short pre-ganglionic and long post-ganglionic fibre
What is a difference between pre-ganglionic and post ganglionic fibres?
fibres are unmyelinated in a post-ganglionic fibre
What are two types of ganglia for the sympathetic NS?
- paravertebral
-prevertebral
Where is the paravertebral ganglia located?
- next to the vertebral column (paired), including in all vascular smooth muscle, arrector pili muscles, head neck thorax visceral organs
Where is the prevertebral ganglia located?
anterior to the spinal column (single)
- all visceral organs in the abdomen and pelvis
The paravertebral ganglia and associated fibres form the?
sympathetic chain
What is the sympathetic chain comprised of?
paired, longitudinally arranged paravertebral sympathetic ganglia linked together
What two things can the post-ganglionic neuron innervate?
blood vessels, arrector pili muscles and sweat glands by returning to the spinal nerve for innervation
or
form a splanchnic nerve for innervation of visceral targets (contain visceral sensory fibres and autonomic fibres)
What is the location of the prevertebral ganglia?
it lies along the aorta and its major arterial branches
What is a situation in which pre-ganglionic fibres can pass neural messages without a post-ganglionic neuron?
pre-ganglionic fibre can pass through the sympathetic trunk to synapse on chromaffin cells within the adrenal medulla
what do chromaffin cells secrete?
norepinephrine and epinephrine which then travels through the bloodstream
Summarize what a pre-ganglionic neuron can do
- enter sympathetic chain and synapse on a paravertebral ganglia (same level, above or below)
- pass through the trunk and synapse in pre-vertebral ganglion
- pass through the trunk to synapse on the chromaffin cells within the adrenal medulla
What are the target organ receptors in the parasymapthetic NS?
Muscarinic M1-M5 (acetycholine): located in cardiac muscle, smooth muscle and glands
Where is the Parasymapthetic NS located?
it arises from the brainstem & grey matter of sacral segments S2-S4 regions of the spinal cord
What does the parasympathetic NS consist of in terms of pre-ganglionic and post-ganglionic fibres?
long pre-ganglionic and short post-ganglionic fibres
Why are the pre and post ganglionic fibres of this length in the Parasymp NS?
Because terminal ganglia are located within/near the visceral effector/target organs
What is an autonomic plexus?
a network of nerves in the body that contain autonomic nerve fibres- both symapthetic and parasympathetic
What is an autonomic plexus formed from?
sympathetic postganglionic axons
parasympathetic preganglionic axons
visceral sensory axons
What are different major autonomic plexuses?
cardiac, pulmonary, abdominal aortic, superior and inferior hypogastric
What are the functions of the parasymapthetic NS
regulates heart rate and promotes digestion, allows urination, promotes sweating
What does the sympathetic NS control?
pupil size, eyelids, sweat glands
