Lecture 5: Peripheral Nervous System Flashcards
Components of the CNS
brain, brainstem and spinal cord
Components of the PNS
Nerves and ganglia outside the CNS
-somatic and autonomic
how many pairs of spinal nerves are there
31
how many pairs of cranial nerves are there
12
Somatic NS
voluntary; the division of the PNS that includes sensory and motor neurons
Sensory (Afferent) neurons
-send signals from outside world to brain
-convey input from receptor for somatic and special senses
Somatic Motor (efferent) neurons
-send signals from brain to outside world
-innervate skeletal muscles
Autonomic NS
Involuntary
-regulates cardiac muscle, smooth muscle and glandular tissue
-autonomic motor neurons regulate visceral activities by exciting or inhibiting activities in effector tissues
Afferent divisions of the PNS
Somatic sensory and visceral sensory
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
Neuron system of somatic
-direct highway
-fully myleinated
-1 neuron system
Neuron system of Autonomic
-2 neuron system
-preganglionic neuron and postganglionic neruon
-preganglionic is mylinated
-postganglionic is unmylinated
-synapse occurs at ganglion
major difference between CNS and PNS
the CNS is composed by the spinal cord and the PNS is composed by cranial nerves
Which of the following sensory responses is not a part of the Somatic Sensory division?
a) Proprioception
b)Taste
c)Pressure
d)Vision
Taste
General Sensory Receptors by Structural Class
- Free nerve endings
- Encapsulated
- Proprioceptors
Free nerve endings of sensory neurons: Functional Class by stimulus type
Nociceptors, thermoreceptors, mechanoreceptors, and chemoreceptors
Free nerve endings of sensory neurons: Body Location
MOST body tissues: most dense in connective tissues
Modified free nerve endings (Merkel discs): Functional Class by Stimulus Type
mechanoreceptors (light pressure)
Modified free nerve endings (merkel discs): body location
deepest layer of the epidermis
Hair Follicle Receptors: Functional Class
Mechanoreceptors (hair deflection)
Hair Follicle Receptors: Body Location
In and surrounding hair follicles
Tactile (Meissner’s) corpuscles: Functional Class by Stimulus Type
Mechanoreceptors (light pressure, discriminative touch, vibration of low frequency)
**detects how many objects are touching your skin at a time
Tactile (Meissner’s) corpuscles: Body Location
Hairless skin, particularly nipples, external genitalia, fingertips, eyelids
Sensory receptors: Free nerve endings
-Free Nerve endings of sensory neurons
-Modified free nerve endings (Merkel discs)
-Hair Follicle Receptors
Sensory Receptors: Encapsulated
-Tactile (Meissner’s) Corpuscles
-Lamellar (Pacinian) corpuscles
-RUffini Corpuscles
Sensory Receptors: Proprioceptors
-muscle spindles
-Tendon Organs
Lamellar (Pacinian) corpuscles: Functional Class by Stimulus Type
-Mechanoreceptors (deep pressure, stretch, vibration of high frequency)
Lamellar (Pacinian) corpuscles: Body Location
Dermis and hypodermis; most abundant on fingers, soles of feet, external genitalia, nipples
Ruffini Corpuscles: Functional Class by Stimulus Type
Mechanoreceptors (deep pressure and stretch)
Ruffini Corpuscles: Body location
deep in dermis, hypodermis and joint capsules
Muscle Spindles: Functional class by stimulus type
Mechanoreceptors (muscle stretch)
Muscle Spindles: Body Location
Skeletal muscles, particularly those of the extremeties
Tendon Organs: Functional Class by stimulus type
machanoreceptor (tendon stretch)
Tendon organs: Body location
tendons (at ends of muscles)
Which of the following is responsible for sensing proprioception?
a) free nerve endings
b)merkel cells
c) muscle spindles
d) hair follicle recpeptor
C) muscle spindles
true or false: Pacinian corpuscles are responsible for sensing deep pressure?
true
Breakdown of the vertebrae
7 cervical
12 thoracic
5 lumbar
5 sacral
3-5 coccygeal
Purpose of spinal nerves
-communication system between brain and various body parts
-essential for voluntary and involuntary actions
-highway for sensory and motor integrations
-important for rapid automatic responses through reflexes
3 parts of the anatomy of the spinal nerve
-Epineurium
-Perinrurium
-Endonerurium
what are fasicles
bundles of axons
how many pairs of spinal nerves are there
31
Which pairs of spinal nerves leave the spinal cord ABOVE their corresponding vertebrae level?
1-7
Each spinal nerve connects to the spinal cord through:
dorsal root via dorsal rootlets
Dorsal root
contains axonal processes of sensory neurons arising from posterior horn
The dorsal root contains:
the dorsal root ganglion
-enlargement of the dorsal root
-cluster of cell bodies of sensory neurons
-functions as sensory relay stations by processing and modulating sneosry signal before reaching the CNS
The spinal nerve and the dorsal root gagnglion lie within the
intervertebral foramina
Ventral root
contains axonal processes of motor neurons whose cell bodies are located in the anterior horn of the spinal cord
ventral root connects to the spinal cord via
ventral rootlets
each spinal nerve branches into a:
dorsal and ventral ramus
WHich type of fibers do the dorsal and ventral rami contain
sensory and motor
what do the dorsal and ventral rami supply?
exit through intervertebral foramina to supply the entire somatic region of the body
Dorsal Rami
supplies dorsum of the neck and back
Ventral rami
-supplies anterior and lateral regions of neck and trunk
-supplies all regions of the limbs
-much thicker than dorsal rami
ventral rami branch into
nerve plexuses
how many primary nerve plexuses does the ventral rami form and what do they target
4
-travel to specific target tissues, such as muscles, skin, and organs to facilitare motor control and sensory perception
four main plexuses
cervical, brachial, lumbar, sacral
Cervical Plexus
-spinal nerves C1-C4
-supply sensory & motor innervation to the neck and proportions of the head
Brachial Plexus
-supply nerves C5-T1
-supply sensory & motor innervation to shoulder and upper limbs
Lumbar Plexus
-Spinal nerves L1-L4
-supplies nerves to the lower back, abdominal wall, and part of the lower limb
Sacral Plexus
-spinal nerves L4-S5
-innervates the buttocks, pelvic structures and the remainder of the lower limb
The path from the spinal cord
- Nerves originate from the spinal cord through two roots: dorsal and ventral
- Dorsal and Ventral roots unite outside the spinal cord to form a spinal nerve
- THe spinal nerve branches into two rami: dorsal and ventral
path of dorsal roots information
carrying sensory information into the spinal cord
path of ventral roots information
carrying motor information away from the spinal cord
which of the following plexus is responsible for innervation of the upper limbs
brachial
which anatomical structure of the spinal nerve has both sensory and motor components
ventral rami
What are dermatomes
-sctions of the skin innervated by a single spinal nerve
-motor and sensory innervation for those specific areas
important dermatones
T4: nipples
T10: Umbillicus
Motor Reflex Arc
-neural pathway that mediates rapid involuntary actions
-integrates sensory inputs and motor outputs
-physiological and nural response against potential harmful stimuli
Pathway of the motor reflex arc
- Sensory Receptor
- Sensory neuron (afferent)
- Dorsal Root ganglion
- Dorsal Root
- Posterior Horn
- Interneurons
- ANterior Hron
- Motor Neuron (efferent)
- Effector Muscle
