Peripheral Nervous System Flashcards
(32 cards)
What are the 31 Pairs of Spinal Nerves?
*Cervical: 8
*Thoracic: 12
*Lumbar: 5
*Sacral: 5
*Coccygeal: 1
What are Dermatomes?
*Map showing the relationship between sensory receptors of the skin and the spinal nerves
*Useful in clinical setting when trying to determine if there has been spinal cord or spinal nerve damage
What is Paraplegia?
Paraplegia
* Damage between T1 →L2
* Loss of feeling/motor functions of legs
What is Quadriplegia?
Quadriplegia
* Damage above T1
* Loss of feeling/motor functions of all 4 limbs
* May be partial or full loss of upper limbs
* If damage occurs above C4, diaphragm is impacted
* Loss of ability to breathe without help
What is Shingles?
*Varicella-zoster virus resides in single dorsal
root ganglion
- From previous chicken pox infection
*If immune system is weakened (due to
illness or age), virus can multiply, travel
along peripheral sensory nerves, and cause
painful skin lesions
*The lesions are located within a dermatome
*A vaccination is available to prevent
outbreak
What is Structural Organization
of PNS?
*Sensory receptors →sensory neurons
- Respond to stimulus and initiate action potentials
- (Some sensory neurons are able to respond to stimuli without a receptor)
*→Motor neurons
*→Effector(s)
What ar sensory receptors?
Can be simple
* Ex. Free nerve ending (dendrite) of sensory neuron
Can be complex
* Ex. Specialized cell (Pacinian corpuscle)
Functional classification of receptors
* Mechanoreceptors: respond to mechanical forces
* Thermoreceptors: temperature changes
* Chemoreceptors: chemicals
* Photoreceptors: light
* Nociceptors: pain
What is Specialized Sensory Processing?
Echolocation
Magnetoreception
What is Echolocation?
Echolocation
* Not just for bats!
* Humans can train themselves to use
echoes to help with navigation
(especially those without sight)
What is Magnetoreception?
Magnetoreception
* Are humans innately able to respond to
magnetic forces/ sense magnetic fields?
* A magnetosensitive protein (cryptochrome-
2) has been found in the human eye
What is Mechanoreceptors: Meissner’s Corpuscle?
*Mechanoreceptors respond to distortion caused by pressure changes, vibration, etc.
*An example is the Miessner’s(tactile) corpuscle
- Responds to light, discriminative touch
- Located in dermal papillae of hairless skin
What is Mechanoreceptors: Pacinian Corpuscle?
Pacinian (lamellar) corpuscle
* Responds to deep pressure
* Located in dermis and hypodermis
* Adapt rapidly, so good at on/off processing or
rapid vibration
What is Mechanoreceptors: Ruffini Endings?
Ruffini endings (bulbous corpuscle)
* Located in dermis and hypodermis
* Respond to deep pressure, stretch
* Adapt slowly so are able to monitor continuous pressure
What are Mechanoreceptors: Proprioceptors?
*Proprioceptors are encapsulated nerve endings that monitor stretch in their locomotory organs (muscles, tendons, etc.)
- Examples: muscle spindle, (golgi) tendon organ
*Offer awareness of movement
*Cerebellum uses information to determine where our body parts are in space
What are Mechanoreceptors: Root Hair Plexus?
Root hair plexus
* Free nerve endings wrapped around hair follicle
* Respond to movement (deflection) of the hair
What are Thermoreceptors?
*Free nerve endings that respond to temperature changes
*Found throughout the body
What are Nociceptors?
*Free nerve endings that respond to mechanical, thermal, or chemical stimuli
- Examples: excessive pressure, extreme temperatures, chemical released from damaged cells
*Pain is the emotional way our brain interprets the stimulus
What are Itch Receptors?
*Itch receptors are recently discovered free nerve endings
- Scientists used to believe nociceptors responded to the itch stimulus
*Itch receptors respond to inflammatory chemicals (ex. Histamine)
*A major difference between nociception and itch:
- Pain elicits a withdrawal reflex
- Itch elicits a scratch reflex
What are Chemoreceptors: Taste?
*Chemoreceptors respond to certain chemicals
- Taste, olfaction, blood chemistry
*Taste buds have chemoreceptors that respond to chemicals of food
*Gustatory pathway:
- Chemoreceptor of taste bud →spinal cord →thalamus →gustatory cortex in insula
What are Photoreceptors: Eye?
*Photoreceptors respond to light
* found in retina of eye
- (melanocytes have now been found to be photoreceptive)
What are Peripheral Nerves?
*Include cranial nerves and spinal nerves
* All cranial nerves except the Vagus (X) are involved with functions of the head and neck
* 31 pairs of spinal nerves form nerve plexuses
What are the Divisions of a Spinal Nerve?
*Spinal nerves split into a dorsal ramus and a ventral ramus
*The ventral rami form the nerve plexuses
- Except in the thoracic region
– Ventral rami innervate the thoracic cage
What is the Nerve Plexuses?
*A plexus is a network of nerves that supply specific regions of the body
*Made of ventral rami of all spinal nerves except T2-T12
*Nerve plexuses:
- Cervical
- Brachial
- Lumbar
- Sacral
What is the Cervical Plexus?
*Formed from ventral rami C1-C5
*Innervates back of neck and diaphragm
- Damage to phrenic nerve can impair breathing
