DSA 1 Flashcards
Division of the peripheral NS.
Peripheral nervous system (PNS) is divided into a sensory (afferent) division and a motor (efferent) division.
- Sensory (afferent) division
- Somatic sensory subdivision: general sensory information we are consciously aware of.
- Visceral sensory subdivision: sensory information from organs that monitor organ status
- Motor (efferent) division
- Somatic nervous system: controls skeletal muscle contraction
- Autonomic nervous system: Involuntary body functions and maintain internal homeostasis. It innervates smooth muscle of organs, the heart, and glandular secretion
* A. Sympathetic
* B. Parasympathetic
- Autonomic nervous system: Involuntary body functions and maintain internal homeostasis. It innervates smooth muscle of organs, the heart, and glandular secretion
What is the neuron pathway in the ANS?
ANS has a 2-neuron system that goes from the CNS–> organs.
Presynaptic neurons- located in CNS
Postsynaptic neurons- located in periphery
Features of the sympathetic NS
- Catabolic/Anabolic
- Distrubution?
Functions?
- Catabolic- uses energy to prepare for fight or flight.
- It is distributed to all vascularized portions of the body
- Ex. Responsible for vasoconstriction of vessels (except coronary arteries). Dilates the coronary arteries.
- Bronchodilation
- Ejaculation
Features of the parasympathetic NS
- Catabolic/Anabolic
- Distrubution?
- Functions?
- Anabolic- promotes normal function by conserving NRG to help rest and digest
- Restricted to the head, neck, and body cavity viscera but it is not found within the body walls or limbs.
- Responsible for glandular secretion except sweat glands
- Produces erection
Describe the presynaptic and postsynaptic fibers of the sympathetic NS and parasympathetic NS
Path of sympathetic NS neurons
- [CB of the presynpatic sympathetic neurons] are located in the lateral gray horn of the SC between T1 and L2/3.
- Exit via the ventral root–> spinal nerves
- Spinal nerves–> white rami communicans
- White rami communicans–> short pre-synaptic nerves will synapse with long postsynaptic neurons in the sympathetic chain/paravertebral ganglia.
*Some neurons can also synapse with ganglia outside of the chain, called prevertebral (collateral) ganglia.
- Post-synaptic neurons then re-enter the spinal nerves via gray rami communicans
- Distributed throughout the entire body via ventral and dorsal rami
What do white rami communicans do?
carry the pre-synaptic sympathetic axons from the spinal nerve –> sympathetic trunk ganglia.
What do gray rami communicans do?
They carry postsynaptic sympathetic fibers back to the spinal nerve to travel to effectors.
Where are white rami communicans found?
T1-L2/3
Where are gray rami communicans found? Why?
C1- coccyx
because postsynaptic sympathetic innervation is distributed to body walls and extremeties.
Do pre-synaptic sympathetic neurons always synapse with sympathetic chain at the same level?
No.
Sometimes, especially in the cervical and sacral levels, the axons carried by the white rami communicans enter the sympathetic chain, but instead of synapsing at the same vertebral level, they travel up or down the chain before synapsing with postsynaptic neurons at another level.
Do presynaptic sympathetic chain neurons always synapse with sympathetic chain ganglia?
No.
Neurons in the abdomen and the pelvis do not have to synapse with ganglia in the sympathetic chain. I
nstead, presynaptic sympathetic neurons go through the sympathetic trunk and exit via thoracic splanchnic nerves to synapse on collateral ganglia on the abdominal aorta, celiac and superior and inferior mesenteric ganglia. -
Once the axons synapse in collateral ganglia, they then follow the blood vessels and go to organs supplied by these vessels.
Presynaptic sympathetic neurons that do not synapse in the sympathetic chain do what?
They inhibit the activity of muscles and glands in the visceral organs.
*The collateral ganglia are located near branches of the abdominal aorta and are referred to by their location*
What is the adrenal medulla?
Important organ of the sympathetic NS.
Presynaptic sympathetic neurons that exit from T8- L1 will pass through sympathetic trunk without synapsing–>
enter the abdomen as splachnic nerves–>
chromaffin cells in the adrenal medulla: release NE and Epi.
The parasympathetic Ns has neuronal outflow from where?
Brain and sacral area