PNS & autonomic nervous system Flashcards
CNS
brain, brainstem and spinal cord
PNS
nerves and ganglia outside the CNS
what does the PNS split into
- somatic nervous system
- autonomic nervous system
somatic nervous system
VOLUNTARY
- includes both sensory and motor neurons
somatic sensory neurons
afferent
- receptors for somatic senses
- receptors for special senses
somatic motor neurons
efferent
innervate skeletal muscles
Autonomic nervous system
INVOLUNTARY
- regulates cardiac muscles, smooth muscle, glandular tissue
- autonomic motor neurons regulate visceral activities by exciting or inhibiting activities in effector tissues
somatic sensory
carries signals from receptors in skin, muscles, bones, and joints
visceral sensory
carries signals mainly from organs in the thoracic and abdominal cavities
what is the difference between autonomic and somatic in the nervous system
somatic: direct highway to the muscle
autonomic: connects to ganglion then to muscle
which of the following statements best describes a difference between the CNS and PNS
1. the CNS is composed by the spinal cord, while the PNS is composed by cranial nerves
2. both the CNS and PNS exclusively consists of the brain and spinal cord
3. the PNS is responsible for processing sensory information, whereas the CNS is responsible for motor functions
4. the CNS and PNS are terms used interchangeably to describe the same set of neural structures
1.
which of the following sensory responses is NOT part of the somatic sensory division
1. proprioception
2. taste
3. pressure
4. vision
2.
general sensory receptors by structural class
- free nerve endings:
- encapsulated:
- proprioceptors
free nerve endings: sensory receptors
- nociceptors (pain)
- thermoreceptors (temp)
- mechanoreceptors (pressure)
- chemoreceptors
in most body tissue; most dense in CT
modified free nerve endings
merkel discs
mechanoreceptor (light pressure)
- deepest layer of epidermis
hair follicle receptors (free nerve endings)
mechanoreceptors (hair deflections)
- in and surrounding hair follicles
list the encapsulated sensory receptors
- tactile (Meissner’s corpuscles)
- lamellar (Pacinian corpuscles)
- Ruffini corpuscles
tactile (Meissner’s corpuscles)
- mechanoreceptor (light pressure, discriminative touch, vibration of low frequency)
- hairless skin (nipple, genitalia, finger tips, eyelids)
lamellar (Pacinian corpuscles)
- mechanoreceptor (deep pressure, stretch, vibration of high frequency)
- dermis and hypodermis; on fingers, soles of feet, genitalia, nipples
Ruffini corpuscles
- mechanoreceptors (deep pressure and stretch)
- deep in dermis, hypodermis, and joint capsules
sensory receptors proprioceptors
- muscle spindles
- tendon organs
muscle spindles
- mechanoreceptors (muscle stretch)
- skeletal muscles, particularly those of the extremities
tendon organs
mechanoreceptor (tendon stretch)
- tendons
which of the following is responsible for sensing proprioception
1. free nerve endings
2. merkel cells
3. muscle spindles
4. hair follicle receptor
3.
true or false:
Pacinian corpuscles are responsible for sensing deep pressure
true
what does the spinal cord consists of:
- posterior horn
- anterior horn
- lateral horn
what are the purposes of spinal nerves
- communication between brain and body parts
- voluntary and involuntary actions
- high way for sensory and motor integrations
-rapid automatic responses through reflexes
anatomy of the spinal nerve + function
structural support, protection, organization
- epineurium (around whole nerve)
- perineurium (surround fascicles)
- endoneurium (surrounds axons)
segments of spinal nerves
- 8 pairs of cervical nerves
- 12 pairs of thoracic nerves
- 5 pairs of lumbar nerves
- 5 pairs of sacral nerves
- 1 pair of coccygeal nerves
how many pairs of spinal nerves are there?
31
what pairs leave the spinal cord above their corresponding vertebrae level
pairs 1-7
each spinal nerve connects to the spinal cord through?
dorsal root
ventral root
dorsal root
- contains axonal processes of sensory neurons arising from posterior horn
what does the Dorsal root contain?
dorsal root ganglion
what is the dorsal root ganglion
- enlargement of the dorsal root
- cluster of cell bodies of sensory neurons
how does the dorsal root ganglion function?
as sensory relay stations by processing and modulating sensory signal before reaching the CNS
where does the spinal nerve and dorsal root ganglion lie?
within the intervertebral foramina
what are two spinal roots
dorsal root
ventral root
ventral root
contains axonal processes of motor neurons who cell bodies are located in anterior horn of the spinal corn
what does each spinal nerve branch into?
dorsal ramus
ventral ramus
where does the dorsal rami supply?
dorsum of neck and back
where does the ventral rami supply
- anterior and lateral regions of neck and trunk
- all regions of limbs
- much thicker than the dorsal rami
similarities of the dorsal and ventral rami
both contain sensory and motor fibers
- exit the vertebral column through the intervertebral foramina
- supply the entire somatic region
ventral rami
do not travel directly to their target tissues but instead branch out extensively to form complex networks
what are the complex network of ventral rami called
nerve plexuses
what are the four primary nerve plexuses from the ventral rami
- cervical plexus
- brachial plexus
- lumbar plexus
- sacral plexus
cervical plexus
- spinal nerves C1-C4
- supply sensory and motor innervation to the
neck
portions of the head
brachial plexus
spinal nerves C5-T1
supply sensory and motor innervation to:
- shoulder
- upper limbs
lumbar plexus
spinal nerves L1-L4
supplies nerves to the:
- lower back
- abdominal wall
- part of the lower limb
sacral plexus
spinal nerves L4-S5
innervates:
- buttocks
- pelvic
- remainder of lower limb
the path from the spinal cord
- nerve originate from the spinal cord through two roots
1. dorsal (info to spinal cord)
2. ventral (info away from spinal cord) - dorsal and ventral roots unite outside the spinal cord to form a spinal nerve
- the spinal nerve branches into 2 rami
1. dorsal rami
2. ventral rami
which of the following plexus is responsible for innervation of the upper limbs
1. cervical
2. thoracic
3. lumbar
4. brachial
4.
which anatomical structure of the spinal nerve has both sensory and motor components
1. dorsal root
2. ventral root
3. dorsal root ganglion
4. ventral rami
4.
what are dermatomes
sections of the skin innervated by single spinal nerve
what are dermatomes
sections of the skin innervated by a single spinal nerve
- motor and sensory innervation for those specific areas
- nipples
- umbilicus
what is the motor reflex arc
- neural pathway that mediates rapid involuntary actions
- integrates sensory inputs and motor outputs
- physiological and neural response against potential harmful stimuli
anatomy of the motor reflex arc
- sensory receptor
- sensory neuron (afferent)
- dorsal root ganglion
- dorsal root
- posterior horn
- interneurons
- anterior horn
- motor neurons (efferent)
- effector muscles
autonomic nervous system
- involuntary motor (efferent)
- innervates smooth and cardiac muscles, viscera, and glands
- regulates unconscious processes
what is the ANS sometimes referred to as
- visceral motor system
sympatheic vs parasympathetic nervous system
- most organs receive both sympathetic and parasympathetic innervation
- the effects are generally considered to be opposing
sympathetic NS function
- stimulate metabolism; active during stress, exertion, emergency
- increases heart rate, force of contraction and BP
- downregulates digestive activity
- dilates blood vessels in skeletal muscles
- fight or flight
function of the Parasympathetic
promotes relaxation, nutrient uptake, energy storage
- decreases heart rate, force contraction and BP
- stimulates digestive secretions and increases gut motility
- dilates blood vessels in GI tract
- rest and digest
neuron
are the basic functional unit of the nervous system; a highly specialized cells that carry electric signals
myelin sheath: anatomy of a neuron
lipid-rich sheath that surrounds some nerve cells axons; are as an insulating layer
somatic nerves
- voluntary control
- one neuron between CNS and target
autonomic nerves
- involuntary control
- two neurons between CNS and target
what does somatic nerve innervate
skeletal
muscles
what does the autonomic nerves innervate
cardiac muscles
smooth muscles
glands
viscera
about preganglionic
located in the brainstem or spinal cord
- myelinated
about postganglionic
located in autonomic ganglion
- unmyelinated
ganglia
collection of neuronal cell bodies found in the PNS
- functions as relay stations between preganglionic and postganglionic neurons of the ANS
autonomic outflow: sympathetic
thoraco-lumbar
regions T1-L2
autonomic outflow: parasympathetic
cranio-sacral
- cranial nerves: CN III, CN VII, CN IX, CN X
- sacral regions S2-S4
sympathetic ganglia
- the sympathetic chain (paravertebral ganglia)
- prevertebral ganglia
- celiac
- superior mesenteric
- inferior mesenteric
the sympathetic chain
paired sympathetic ganglia linked together to form a chain along the length of the vertebral column (C1-S5)
(the connection spread sympathetic responses to many target tissue simultaneously)
where are preganglionic sympathetic neurons limited to
T1-L2
what is the sympathetic ganglia chain also known as
sympathetic trunk or paravertebral ganglia
prevertebral ganglia
situated anterior to the vertebral column, along the aorta
- celiac ganglion
- superior mesenteric ganglion
- inferior mesenteric ganglion
(named relative to blood vessels branching from the abdominal aorta)
length of preganglionic in sympathetic ganglia
short
length of postganglionic in sympathetic ganglia
long
rami communicans
connection between the spinal nerve and sympathetic trunk
type of communicans within the sympathetic outflow
white ramus communicans
gray ramus communicans
where are white and gray communicans located with the sympathic
white- only from T1-L2
gray- all levels along sympathetic
where does sympathetic outflow originate?
in the lateral horn of the spinal cord, from segments T1-L2
where does preganglionic neurons of the sympathetic outflow exit? and enter?
the ventral horn and root to enter the spinal nerve
where does the preganglionic neuron enter the sympathic chain?
via the white ramus communican “on ramp”
what are the 3 main routes preganglionic neurons have before entering the sympathetic chain
- synapse within the chain at the same level
- change level within the chain and then synapse
- formation of a splanchnic nerve
synapse within the chain at the same level
preganglionic neurons synapses with postganglionic neuron at the same level and exits via the grey ramus, travelling with spinal nerve to target
same level
preganglionic neurons located between T1-L2
same level nerve targets
body wall
abdominal and thoracic viscera
limbs
same level outflow pathway Preganglionic neurons
- located in the lateral horn (T1-L2)
- myelinated preganglionic axon exits spinal cord via the ventral horn and ventral root to enter the spinal nerve
- preganglionic axon then leaves spinal nerve, and enters the sympathetic trunk via white ramus communicans to synapse on the postganglionic neurons
same level outflow pathway Postganglionic neurons
- unmyelinated postganglionic axon passes through the gray ramus communicans to enter the spinal nerve
- postganglionic fiber travels within spinal nerve to innervate target
change level within the chain and then synapse
preganglionic fiber can ascend or descend within the sympathetic chain
- Between T1-L2
ascending nerve targets
- head/neck viscera
- thoracic viscera
- upper limbs
descending nerve targets
- abdominopelvic viscera
- lower limbs
viscera of the thorax
organs in the thorax are supplied by various plexuses
- postganglionic contribute to autonomic plexuses
cardiac plexus
pulmonary plexus
splanchnic nerve formation
aka visceral nerves
- form when autonomic fibers do not re-join the spinal nerve
- preganglionic fibers bypasses the sympathetic chain completely and synapses in a peripheral (prevertebral) ganglion near the target
splanchnic nerve: target abdominopelvic viscera
originate from thoracic and lumbar vertebral levels of the spinal cord, as sets of paired splanchnic nerves
- then synpases in prevertebral ganglion
paired splanchnic nerves
- greater splanchnic (T5-9)
- lesser splanchnic (T10-11)
- least/lumbar splanchnic (T12-L2)
prevertebral ganglion
- celiac ganglion
- superior mesenteric ganglion
- inferior mesenteric ganglion
what ganglion goes with greater splanchnic nerve
celiac ganglion
what ganglion goes with lesser splanchnic
superior mesenteric ganglion
what ganglion goes with least/lumbar splanchnic nerve
interior mesenteric ganglion
parasympathetic nervous system
“rest and digest”
parasympathetic nervous system targets
- viscera of head and neck
- abdominal and thoracic viscera
- pelvic viscera
parasympathetic ganglia
located near or within the target organ
preganglionic—> long
postganglionic —> short
PNS: cranial outflow
CN III: occulomotor
VII: facial
IX: glossopharyngeal
X: vagus
cranial outflow: head and neck
CN III, VII, IX
- preganglionic neurons leave brainstem from parasympathetic nuclei
- synapse on post-ganglionic neuron with parasympathetic ganglion
CN VII parasympathic to what ganglion
pterygopalatine ganglion–> lacrimal gland
submandibular ganglion–> sublingual/submandii gland
CN III parasympathic goes to what ganglion
ciliary gland–> eye
cranial outflow: head and neck
CN III, VII, IX
- preganglionic neurons leave brainstem from parasympathetic nuclei
- synapse on post-ganglionic neuron within parasympathetic ganglia
cranial outflow: thoracic and abdominal viscera
- preganglionic neurons leave the brainstem via CN X, which contribute to autonomic plexuses
- supplies parasympathic to pharynx, larynx, thorax and midgut structures
- preganglionic neurons synapse on ganglia within or close to target
what are ganglions that are within the target called
intra-mural ganglion
sacral outflow: distal GI tract and pelvic viscera
- preganglionic neuronal cell bodies located in spinal segments S2-S4
- axons travel via pelvic splanchnic nerves which contribute to autonomic plexus
- preganglionic fibers synapse within ganglia in or near effector organ to supply targets
which nerve supplies parasympathetic innervation to the lungs?
1. CN X (vagus)
2. CN IX (glossopharyngeal)
3. CN III (oculomotor)
4. pelvic splanchnic nerves
5. none of the above
1
visceral afferent fibers
conduct sensory information from autonomic targets to the CNS
(are distinct from the autnomic nervous system)
what are visceral afferent fibers not considered
sympathetic or parasympathetic
visceral reflexes
are the simplest functional units in the autonomic nervous system
- consists of a sensory nerve, and visceral motor neurons
example of visceral relfex
shinning a light in the eye triggers a visceral reflex that constricts the pupils
enteric nervous system
part of the ANS
- network of neurons located in the walls of the digestive tract
- receives regulatory signals via sympathetic and parasympathetic divisions
CN IX to what ganglion
otic ganglion
