Week 1: PNS

Question 1

What is the basic schema of the PNS?

Answer 1

Input –> CNS –> Output

Question 2

What is the term for the signal receptor nerves that come in from the body?

Answer 2

Sensory/afferent, which have both conscious (somatic) and unconscious (visceral)

Question 3

Where do somatic afferent nerves send signals from?

Answer 3

Skin and skeletal muscles

Question 4

Where do visceral afferent nerves sense signals from?

Answer 4

Internal organs

Question 5

What is the term for output signals from the CNS?

Answer 5

Motor/efferent nerves, can be voluntary (somatic, skeletal muscles) and involuntary (visceral, ANS)

Question 6

What does the somatic sensory system detect?

Answer 6

Temperature

Pain

Touch

Proprioception (position in space)

Question 7

What does the visceral sensory system detect?

Answer 7

Change of internal environment of viscera, including stretch, temperature, pain, hunger, nausea, etc.

Question 8

What does the visceral motor system act on? What is another term for this system? What are it’s main components?

Answer 8

The Autonomic Nervous System (ANS) acts on smooth muscle, cardiac muscle and glands, and has sympathetic and parasympathetic components.

Question 9

What are the two different types of nerves?

Answer 9

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!

Question 10

Identify A - J

Answer 10

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

Question 11

The ventral/anterior root carries ____________ signals

Answer 11

motor/efferent (somatic and visceeral)

Question 12

The dorsal/posterior root carries _____________ information

Answer 12

sensory/afferent (somatic and visceral)

Question 13

The spinal nerve carries ____________ information

Answer 13

BOTH motor efferent AND sensory afferent (somatic and visceral)

Question 14

The ventral/anterior ramus carries information to _____________

Answer 14

body walls and limbs

Question 15

The dorsal/posterior ramus carries information to ____________

Answer 15

The deep back muscles and skin

Question 16

What is the main difference between somatic and visceral motor outflow?

Answer 16

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)

Question 17

What are the two kinds of nerves of the ANS?

Answer 17

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

Question 18

What are the principal differences between sympathetic and parasympathetic preganglionic and postganglionic nerves?

Answer 18

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)

Question 19

What are the activities that are involved with sympathetic activation of the ANS?

Answer 19

Heart rate and contractility increase

GI inhibition (decreased digestion/defecation)

Bronchodilation

Bladder muscle inhibition

Pupil dilation

Blood vessel tone increase (higher BP)

Genitalia (ejaculation)

Skin (sweating and piloerection)

Question 20

What are the activities that are involved with parasympathetic activation of the ANS?

Answer 20

Heart rate decrease

GI movement, digestion, defecation

Bronchiolar constriction

Bladder contraction/urination

Pupil constriction for near vision

Genitalia (erection)

Question 21

What actions do the para/sympathetic systems activate in regards to sexual activity? How do we remember this?

Answer 21

Erection = Parasympathetic = “Point”

Ejaculation = Sympathetic = “Shoot”

Question 22

What pathway is “mandatory” in the sympathetic system? What pathway is “optional”?

Answer 22

All outgoing sympathetic signals exit through the ventral/efferent nerve, move through the spinal ganglia and spinal nerve, then circle “forwards” around to the white ramus communicans. All sympathetic preganglionic nerves must go through the white ramus.

However, not all postganglionic fibers behave the same–they have optional pathways. Some synapse at the ganglia there, and pass through the gray ramus communicans to the anterior or posterior perpiphery. Some pass through the ganglia and synapse elsewhere.

Question 23

Why are there more gray rami communicans than white?

Answer 23

White rami communicans only exist in the T1 - L2 segment of the spine, where sympathetic nerves are connecting and passing through. There are many more “exit points” along the ENTIRE spinal cord, even outside of T1 - L2, where postganglionic sympathetic nerves are exiting to do their job.

Question 24

How do sympathetic signals travel superiorly and inferiorly from a given thoracolumbar segment?

Answer 24

They pass through the ganglia of the sympathetic trunk, which extends farther than the thoracolumbar region of exiting sympathetic neurons.

Question 25

What three pathways can sympathetic nerves follow at junctions of the sympathetic trunk?

Answer 25

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)**

Question 26

How are visceral organs innervated?

Answer 26

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**

Question 27

Splanchnic nerves are ____________ (pre/postganglionic) and cardiopulmonary nerves are ______________ (pre/postganglionic)

Answer 27

Splanchnic = preganglionic Cardiopulmonary = postganglionic

Question 28

Where do most, if not all, thoracic, sacral and lumbar **splanchnic** nerves form synapses?

Answer 28

Preverteral ganglia at target organs such as the aorta

Question 29

What do the thoracic, lumbar, and sacral splanchnics innervate?

Answer 29

**Thoracic** - foregut/midgut, adrenal gland, kidneys **Lumbar** - hindgut, a little bit of pelvis **Sacral** - majority of pelvis

Question 30

Where are most prevertebral plexuses and ganglia located?

Answer 30

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

Question 31

Of all sympathetic nerves, which is the "special" nerve that doesn't synapse anwhere except for at the target organ?

Answer 31

The s**ympathetic 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)**

Question 32

How do parasympathetic nerves travel? What are the two major regions and what kinds of nerves are present?

Answer 32

**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**)

Question 33

What is the difference between sympathetic and parasympathetic innervation of the pelvic region?

Answer 33

**Sympathetic** = **sacral** splanchnics **Parasympathetic** = **pelvic** splanchnics

Question 34

What are the three main regions of innervation, and what are their subdivisions? How do we remember the nerves in each category?

Answer 34

Thoracic Cavity - **C**ardiopulmonary (symp) + **V**agus (para) Abdominal Cavity - **T**horacic (fore/midgut symp)/**L**umbar splanchnics (hindgut symp) + **V**agus (fore/midgut para)/**P**elvic splanchnics (hindgut para) Pelvic Cavity - **S**acral splanchnics + **P**elvic splanchnics Sympathetic: **Create The Last Scene** Parasympathetic: **VVPP**

Question 35

What para/sympathetic nerves innervate the thoracic cavity?

Answer 35

Symp = cardiopulmonary Parasymp = Vagus (CNX)

Question 36

What para/sympathetic nerves innervate the abdominal cavity sections?

Answer 36

**Fore/Midgut:** Symp = thoracic splanchnics Parasymp = vagus (CNX) **Hindgut:** Symp = lumbar splanchnics Parasymp = pelvic splanchnics

Question 37

What para/sympathetic nerves innervate the pelvic cavity?

Answer 37

Symp = sacral splanchnics Parasymp = pelvic splanchnics

Question 38

What are the four main sympathetic prevertebral ganglia?

Answer 38

Celiac ganglia Superior mesenteric ganglia Inferior mesenteric ganglia Hypogastric plexus (less focused on)

Question 39

What are the main parasympathetic ganglia regions?

Answer 39

Head - glands of the mouth, the eyes, intracranial vessels Thorax - lungs, heart Abdomen (foregut) - stomach, liver, spleen, pancreas, small intest. Abdomen (midgut) - kidney, distal small intest., large intest., asc. and transverse colon Abdomen (hindgut) - transverse colon, distal colon, rectum Pelvis + perineum - bladder, sex organs

Question 40

\_\_\_\_\_\_\_\_\_\_\_ nerves innervate the periphery

Answer 40

Sympathetic spinal (T1 - L2)

Question 41

What pathway do pain/irritation signals follow in the visceral sensory pathway?

Answer 41

These signals travel through 1) visceral afferent nerves 2) through the white rami 3) through the posterior root and 4) into the CNS

Question 42

What is referred pain? Why does it occur?

Answer 42

Pain perceived at a location that is not the site of injury/stimulus. It occurs because incoming signals from visceral and somatic afferents **come into the same spinal segment**, and **"confuse" the brain into thinking that the visceral pain is coming from elsewhere.** This occurs because visceral regions are "mapped" more generally, and visceral pain is not well localized. Somatic pain, however, is VERY well localized.

Question 43

What is a nerve plexus?

Answer 43

It is a collection of nerves in the PNS from different segments with specific targets, either somatic or visceral

Question 44

What are the three main somatic plexuses? What areas do they take in information from?

Answer 44

**Cervical** **Brachial** (upper limb) **Lumbosacral** (lower limbs and pelvis)

Question 45

What are the visceral plexuses?

Answer 45

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)**