Week 1: PNS Flashcards
What is the basic schema of the PNS?
Input –> CNS –> Output
What is the term for the signal receptor nerves that come in from the body?
Sensory/afferent, which have both conscious (somatic) and unconscious (visceral)
Where do somatic afferent nerves send signals from?
Skin and skeletal muscles
Where do visceral afferent nerves sense signals from?
Internal organs
What is the term for output signals from the CNS?
Motor/efferent nerves, can be voluntary (somatic, skeletal muscles) and involuntary (visceral, ANS)
What does the somatic sensory system detect?
Temperature
Pain
Touch
Proprioception (position in space)
What does the visceral sensory system detect?
Change of internal environment of viscera, including stretch, temperature, pain, hunger, nausea, etc.
What does the visceral motor system act on? What is another term for this system? What are it’s main components?
The Autonomic Nervous System (ANS) acts on smooth muscle, cardiac muscle and glands, and has sympathetic and parasympathetic components.
What are the two different types of nerves?
Spinal nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccyx)
and
Cranial nerves 1 - 12
Oh Oh Oh To Touch And Feel A Virgin Girl’s V Ah Bliss!
Identify A - J
A - somatic motor nerve
B - somatic sensory nerve
C - posterior root
D - spinal ganglion
E - spinal nerve
F - posterior ramus
G - anterior root
H - anterior ramus
I - anterior rootlets
J - posterior rootlets
The ventral/anterior root carries ____________ signals
motor/efferent (somatic and visceeral)
The dorsal/posterior root carries _____________ information
sensory/afferent (somatic and visceral)
The spinal nerve carries ____________ information
BOTH motor efferent AND sensory afferent (somatic and visceral)
The ventral/anterior ramus carries information to _____________
body walls and limbs
The dorsal/posterior ramus carries information to ____________
The deep back muscles and skin
What is the main difference between somatic and visceral motor outflow?
The somatic motor outflow is a single motor neuron connection between CNS and the target organ (skeletal muscle)
The visceral motor outflowm (ANS) is a two neuron connection (pre- and post-ganglionic) between the CNS and target organ (a gland, or cardiac/smooth muscle)
What are the two kinds of nerves of the ANS?
Preganglionic - originate in CNS and travel to ganglion to form a synapse
Postganglionic - originate in PNS and travel away from a ganglion at the point of a synapse
What are the principal differences between sympathetic and parasympathetic preganglionic and postganglionic nerves?
Sympathetic nerves have short pre- and long postganglionic fibers (T1 - L2)
Parasympathetic nerves have long pre and short postganglionic fibers (cranial nerves and S2 - S4)
How do sympathetic signals travel superiorly and inferiorly from a given thoracolumbar segment?
They pass through the ganglia of the sympathetic trunk, which extends farther than the thoracolumbar region of exiting sympathetic neurons.
What three pathways can sympathetic nerves follow at junctions of the sympathetic trunk?
1) Nerve can exit at the same segment as it originated in via the gray ramus and go to periphery
2) Travel up/down sympathetic trunk to a different spinal segment than it originated in and exit via a gray ramus there to the periphery
3) Travel up or down the sympathetic trunk or leave the same segement, passing through sympathetic chain (PARAVERTEBRAL) ganglia to visceral organs via the splanchnic nerves or cardiopulmonary nerves (synapse at PREVERTEBRAL ganglia)
How are visceral organs innervated?
1) Head - signals travel up the sympathetic chain, synapsing at the uppermost ganglia (above T1 - L2) and sending postganglionic neurons out into the salivary and lacrimal glands, nasal mucosa, and blood vessels/skin
2) Thoracic - nerves travel up the sympathetic chain to the cardiopulmonary region, synapsing at the uppermost T1 - L2 chain ganglia and sending postganglionic neurons out to the heart an lungs
3) Abdominal/pelvic cavity - preganglionic neurons travel through the sympathetic chain WITHOUT SYNAPSING, synapsing instead at the prevertebral ganglia with the postganglionic neuron
Where are most prevertebral plexuses and ganglia located?
They are located on the anterior portion of the aorta, and are primarily located at the major branches, including:
celiac ganglia - foregut
superior mesenteric ganglia - midgut
inferior mesenteric ganglia - hindgut
Of all sympathetic nerves, which is the “special” nerve that doesn’t synapse anwhere except for at the target organ?
The sympathetic nerve that innervates the adrenal medulla is unique because it is one long preganglionic nerve that passes through the paravertebral chain, directly to the adrenal medulla and exerts actions within the organ itself. The medulla acts like a postganglionic fiber, secreting hormone (epinephrine)
How do parasympathetic nerves travel? What are the two major regions and what kinds of nerves are present?
Pelvic splanchnic nerves have long preganglionic nerves that DO NOT go through the para/prevertebral ganglia, and synapse with short postganglionic neurons within ganglia at target organs (CNs are slightly different)
Cranial - most signals come from the vagus nerve (CN X), and travel to the thoracic cavity or abdomen (nerves of the head are slightly different)
Sacral - major parasymp innervation is carried out by pelvic splanchnics (symp innervation by sacral splanchnics)
What pathway do pain/irritation signals follow in the visceral sensory pathway?
These signals travel through
1) visceral afferent nerves
2) through the white rami
3) through the posterior root and
4) into the CNS
What are the three main somatic plexuses? What areas do they take in information from?
Cervical
Brachial (upper limb)
Lumbosacral (lower limbs and pelvis)
What are the visceral plexuses?
There are many. They target specific visceral organs and receive contributions from both sympathetic and parasympathetic nerves.
The heart, for example, receives sympathetic input from the upper T1-area postganglionic nerurons of the sympathetic chain, and receives parasympathetic input from the vagus nerve (CNX)
