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ap chapter 14 PNS

spinal nerves

31 pairs
Cauda equina
Structure
1. Ventral/anterior root ( to muscles) & Dorsal/posterior root
2. Ramus (rami)
a. Dorsal ramus (to back)
i. Supplies somatic motor and sensory fibers muscles and skin of the posterior surface of the head, neck, and trunk
b. Ventral ramus (to front)
i. Innervate muscles and glands in the extremities and lateral and ventral portions of neck and trunk
ii. Autonomic motor fibers split from the ventral ramus
c. Sympathetic rami

Ventral root

include motor neurons that carry information from the CNS and towards effectors (muscles & glands)
to muscles

dorsal root

include sensory fibers that carry information from receptors in the peripheral nerves

Ramus

soon after each spinal nerve emerges from the spinal cavity it forms several large branches, which are ramus
Ramus (rami)
1. Dorsal ramus
a. Supplies somatic motor and sensory fibers muscles and skin of the posterior surface of the head, neck, and trunk
2. Ventral ramus
a. Innervate muscles and glands in the extremities and lateral and ventral portions of neck and trunk
Autonomic motor fibers split from the ventral ramus
Sympathetic rami

dorsal ramus

1. to back
a. Supplies somatic motor and sensory fibers muscles and skin of the posterior surface of the head, neck, and trunk

ventral ramus

1. to front
Innervate muscles and glands in the extremities and lateral and ventral portions of neck and trunk
Autonomic motor fibers split from the ventral ramus

sympathetic rami

coming off

somatic

spinal

autonomic

visceral

plexi

is a web
ventral rami of most spinal nerves subdivide to form complex networks called plexuses

cervical plexus

found deep w/in the neck (C1-C4 along with part of C5 exchange fibers in the cervical plexus)
1. Innervate the muscles and skin of the neck, upper shoulders, and part of the head
2. Phrenic nerve - innervates the diaphragm permitting you to breathe.

brachial plexus

found deep w/in the shoulder
Innervate the lower part of the shoulder and all of the arm

lumbar plexus

1. Innervates thigh and leg
2. Femoral nerve

sacral and coccygeal plexus

1. Supply nearly all the skin of the leg, posterior thigh muscles, and leg and foot muscles
2. Sciatic nerve (largest nerve) thru greater sciatic notch & down the back of the leg

dermatomes

Dermatome-region of skin surface area supplied by afferent (sensory) fibers of a given spinal nerve

myotomes

Myotome-skeletal muscle(s) supplied/received by efferent (motor) fibers of a given spinal nerve, can have overlapping

mixed nerves

contain muscle and sensory. ex. spinal nerves

PNS

mostly somatic, some autonomic

olfactory Nerve

1. In nose (roof)
2. Sensory nerve
3. Carries information about sense of smell
chemical interaction w/mucous - stimulate action potential. Thru cribiform - goes to olfactory bulb
**only place neuron is exposed to environment, will be damaged & will regenerate

Optic nerve

1. Sensory nerve
2. Unite to form optic chiasma
3. Carries visual information from the eyes to the brain
4. carries vision away from eye. crossover make "X" chiasma
5. nerves leaving optic chiasma are called tracts

Vestibulocochlear nerve (aka auditory nerve)

-- connection of vestibular & cochlear branch (both sensory)
1. Sensory nerve
2. Vestibular nerve fibers (Balance)
a. Originate in the semicircular canals
b. Carry the impulses of the sense of equilibrium
3. Cochlear nerve fibers (Hearing)
a. Originate in the organ of Corti
b. Carry the impulses of the sense of hearing

Vestibular nerve fibers (Balance)

a. Originate in the semicircular canals
b. Carry the impulses of the sense of equilibrium

Cochlear nerve fibers (Hearing)

a. Originate in the organ of Corti
b. Carry the impulses of the sense of hearing

Vagus nerve

1. Mixed nerve - muscle and sensory
2. Sensory fibers supply pharynx, larynx, trachea, heart, carotid body, lungs, bronchi, esophagus, stomach, small intestine, and gallbladder (long fiber)
3. Somatic motor fibers innervate the pharynx and larynx
4. Sensation & movement of (visceral) organs supplied
5. most motor fibers os the vagus are autonomic (parasympathetic) fibers.

Somatic motor nervous system

1. Includes all voluntary motor pathways outside the CNS (involves the peripheral pathways to the skeletal muscles, which are somatic effectors)
2. Effectors are skeletal muscles
3. Neurotransmitter is acetylcholine
4. Somatic reflexes
a. Knee jerk (also known as patellar reflex)
- Extension of the lower leg in response to tapping the patellar tendon
b. Ankle jerk (also known as Achilles reflex)
- Extension of the foot in response to tapping the Achilles tendon

Somatic reflexes Examples

1. Knee jerk (also known as patellar reflex) - doctor does to determine the integrity of the reflex arc)
a. Extension of the lower leg in response to tapping the patellar tendon
2. Ankle jerk (also known as Achilles reflex)
a. Extension of the foot in response to tapping the Achilles tendon

Plantar reflex

1. cranial reflex - to brain & back
2. Plantar flexion of all toes and a slight turning in and flexion of the anterior part of the foot in response to stimulation of the outer edge of the sole (Normal if curling toes)

Babinski reflex

1. Abnormal plantar reflex
2. Extension of great toe, with or without fanning of other toes, in response to stimulation of outer margin of sole of foot
3. Over 1-1/2 years of age, a positive Babinski reflex is one of the pyramidal signs indicating destruction of corticospinal fibers (as they go thru pyramids)

Autonomic reflexes

1. control viscera
2. May be spinal (e.g., urination and defecation) or modified by higher brain structures.
3. The thalamus, hypothalamus and brain stem are in charge of multiple reflexes - HR, BP (reflex trying to protect the brain), breathing, eating, osmotic balance, temperature, vomiting, gagging, sneezing.
4. bladder - release on stretch reflex

Somatic (6)

1. Voluntary
2. Skeletal muscle
3. Single efferent neuron
4. Axon terminals release acetylcholine
5. Always excitatory (muscle)
6. Controlled by the cerebrum (pre-central gyrus)

Autonomic (6)

1. Involuntary (visceral)
2. Smooth, cardiac muscle; glands
3. Multiple efferent neurons (2 motor neurons)
4. Axon terminals release acetylcholine or norepinephrine
5. Can be excitatory or inhibitory
6. Controlled by the homeostatic centers in the brain - pons, mostly hypothalamus, medulla oblongata. (cerebrum can override it)

Autonomic nervous system - functions (4)

All dealing with efferent/motor (cause a response)

1. To regulate heartbeat
2. Smooth muscle contraction
3. Glandular secretions
4. To maintain HOMEOSTASIS (biggest thing)

autonomic nervous system - 2 efferent divisions

1. sympathetic division
2. parasympathetic division

autonomic nervous system - 2 neurons

1. Two neurons in the effector pathway. (away from brain or SC to target)
2. 1st neuron is preganglionic neuron
a. Cell body in gray matter of brain or spinal cord (lateral horn).
b. Synapses with postganglionic neuron
2. 2nd neuron is postganglionic neuron
a. Cell body in autonomic ganglion
b. Synapses with effector - which depends on ANS target. dual innervated (parasympathetic & sympathetic) is 2 neurons going in opposite directions

autonomic nervous system

preganglion cell body in (gray matter of lateral horn)
motor ganglion = cell body outside CNS
1st fiber = pre-ganglionic (always)
2nd fiber = post-ganglionic (always)

autonomic pathways

CNS (in lateral horn)---->preganglionic neuron---->Autonomic ganglion---->postganglionic neuron----->target tissue

possible to have two different neurotransmitters
Not in balance = stress

Functions of autonomic nervous systems (4)
Parasympathetic & sympathetic

1. Regulates visceral effectors in ways that tend to maintain or quickly restore HOMEOSTASIS
2. Sympathetic and parasympathetic divisions often exert antagonistic (opposite effects) influences on visceral effectors
3. Major function of sympathetic division is that it serves as an " emergency" system-the FLIGHT OR FIGHT reaction
4. Parasympathetic division is the DOMINANT controller of most autonomic effectors most of the time - Rest and restore reaction

Enteric nervous system

1. Third division of ANS
2. Extensive network in digestive tract walls
3. Complex visceral reflexes coordinated locally
4. Roughly 100 million neurons
5. Intrinsic set of nerves - "brain of gut"
6. Neurons extending from esophagus to anus
7. 2 plexuses
a. Myenteric plexus - GI tract motility (walls)
b. Submucosal plexus - controlling secretions

Myenteric plexus

Enteric nervous system
GI tract motility

Submucosal plexus

Enteric nervous system
controlling secretions

dual innervated

1. (parasympathetic & sympathetic) is 2 neurons going in opposite directions
2. autonomic effectors receive input from both parasympathetic and sympathetic pathways
3. allow effector to be controlled w/remarkable precision

1st neuron

1st neuron is preganglionic neuron
a. Cell body in gray matter of brain or spinal cord (lateral horn.
b. Synapses with postganglionic neuron

2nd neuron

2nd neuron is postganglionic neuron
a. Cell body in autonomic ganglion
b. Synapses with effector - which depends on ANS target. dual innervated (parasympathetic & sympathetic) is 2 neurons going in opposite directions

olfactory nerves - summation

receptors = nasal mucosa
cell bodies = nasal mucosa
termination = olfactory bulbs
function = sense of smell

optic nerves - summation

receptors = retina
cell bodies = retina
termination = nucleus in thalamus, some in superior colliculus in midbrain
function = vision

vagus - summation sensory fibers

receptors = pharynx, larynx, carotid body, thoracic & abdominal viscera
cell bodies = jugular & nodose ganglia
termination = medulla & pons

vagus - summation motor fibers

cell bodies = medulla (dorsal motor nucleus)
termination = ganglia of vagal plexus & then to muscles of pharynx, larynx & autonomic fibers to thoracic & abdominal viscera
function = sensations & movements of organ supplied ex. slows heart, increase peristalsis, contracts muscles for voice production

dorsal root ganglion

contains cell bodies of the sensory neurons

ramus definition

soon after each spinal nerve emerges from the spinal cavity it forms several large branches, which are ramus

somatic reflexes definition

1. contractions of skeletal muscles
2. impulse conduction over somatic reflex arcs - arcs whose motor neurons are somatic motor neurons

Autonomic (visceral) reflex definition

1. contractions of smooth or cardiac muscles, secretion by glands
2. impulse conduction over autonomic reflex arcs - the motor neurons are automatic motor neurons

Efferent autonomic pathways consists of 3 things

1. autonomic nerves
2. ganglia
3. plexuses
theses structures are made up of autonomic neurons

collateral ganglia

1. pairs of sympathetic ganglia located a short distance from the SC
2. preganglionic neurons pass thru chain ganglia w/o synapsing go thru splanchnic nerves to collateral ganglia
Ex. Celiac ganglion, superior mesenteric ganglion & inferior mesenteric ganglion

adrenergic fibers

axons that release norepinephrine
adrenergic effects often linger for some time after stimulation has ceased because uptake of neurotransmitters are slower with MAO & COMT than w/acetylcholinesterase.

cholinergic fibers

axons that release acetylcholine

autonomic adrenergic fibers are (1)

aons of
1. postganglionic sympathetic fiber

autonominc cholinergic fibers are (4)

axons of
1. preganglionic sympathetic fibers
2. preganglionic parasympathetic fibers
3. postganglionic parasympathetic fibers
4. into muscle fibers

Nicotinic

1. in both parasympathetic & sympathetic acetylcholine binds to nicotinic in the membranes of the postganglionic cells (beginning of 2nd neuron)
2.

Muscarinic

1. Acetylcholine, released in all parasympathetic postganglionic cells, binds with muscarinic (at the target)

CNS hierachy that regulates autonomic funtions

1. autonomic centers in cerebral cortex (frontal lobe/limbic)
the
2. autonomic center in hypothalamus (main controller but frontal lobe and limbic system can override)

sympathetic division AKA

thoracolumbar division because the preganglionic neurons (cell bodies) originate from the lateral horn of the thoracic and lumbar regions

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