Nervous System 6 Flashcards
The peripheral Nervous System:
The sensory afferebt division
Of the PNS detects changes in the internal and external environment
Sensory receptors
Adaption: When there is constant stimulus, receptors can recur in sensitivity
There are 2 types:
Phasic: fast adapting- smell
Tonic: adapts slowly or not at all- taste, pain
Receptors and their function
Chemoreceptors: responds to chem like smell, taste, changes in blood pressure
Exteroceptors: “ “ outside the body
Nociceptors: sensitive to pain causing stimuli like extreme temps, excessive pressure and inflammatory chemo
Proprioceptors: responds to stretches in skeletal muscle, tendons, joints, ligaments and tells the brain of micemebt
Receptors and their function cont
Mechanoreceptors: responds to touch, pressure, vibr and stretches
Special senses: vision, hearing, eqm, smell and taste
Visceroceptors: sensitive to chem changes, tissue stretches and temp changes
Signal Transmission
Sensory receptors change stimulus into an action potential through signal transduction
Action potential travel along multiple sensory fibres to the brain through signal transmission
- the first part of the pathway is mediated by peripheral nerves
Never
Consists of peripheral nerve axons enclosed by connective tissue:
Endoneurium: encloses 1 axon
Perineurium: encloses a bundle of them
Epineurium: encloses 1 nerve
Within a mixed nerve
There are different axon fibres based on diameter and degree of Myelination which effect conduction speed
Eg. Both A(omega) and C axon fibres carry info related to pain and temp
Depending on where they start
The nerves are grouped as either cranial or spinal
Cranial Nerves
There are 12 pairs
Numbered I to XII
They innervate urge head and neck except for the vagus nerve, CN X
Look at notes
Antonym
Only(Olfactory)
One(optic)
Oatmeal(oculomotor)
To(trochlear)
Take(trigemineal)
Away(abducens)
For(facial)
Value,(vestibulocohoear)
Good(glossipharyngeal)
Van Houtte(vagus)
And (accessory)
Hash (hypoglossal)
Which CNs are involved in eye movement
Cranial nerves (III, VI and IV)
Which CNs are involved in the special senses?
Olfactory: Olfaction (Smell)
• Optic: Vision
• Facial/Glossopharyngeal/Vagus: Taste
• Vestibulocochlear: Hearing and equilibrium
Look at slides
True or False
We have as many vertebrae as spinal nerves
False
Spinal Nerves
There are 31 pairs:
• 8 cervical (C1 to C8)
• 12 thoracic (T1 to T12)
• 5 lumbar (L1 to L5)
• 5 sacral (S1 to S5)
• 1 coccygeal (Co1)
All of these are mixed nerves
They are named for their exit point from the spinal cord
After the spinal nerves exit the vertebral foramen, they are divided into 3 branches
Dorsal ramus supplies the posterior body trunk.
• Ventral ramus supplies the rest of trunk and limbs.
• Rami communicantes contain autonomic nerve fibres that join ventral rami in the T1-L2 region.
What is the difference between a root and a ramus?
Roots of the spinal nerve approach the spinal cord.
• separated into sensory (dorsal
root) and motor (ventral root).
Rami of the spinal nerves lead away
from the spinal cord. Ramus:
“branch” in Latin.
• carry both sensory and motorfibres to the periphery
Spinal Nerve Plexuses
The ventral rami recombine the nerve fibres from different spinal levels to form plexuses
- fibres that go to a similar region of the body are grouped together to from the peripheral nerves
Major Spinal Neeve Plexuses
Cervical: C1-C4( some of C5)
Brachial: C5-T1
Lumbar: L1-L4
Sacral: L4-S4
Spinal Cord Injury
Injuries to the spinal cord can lead to paralysis of the body.
• changes in strength, sensation, and other functions below the site of the injury
Resultant damage depends on:
- severity: complete or incomplete
- function: changes in sensation and/or motor function
- level: the lowest part of the spinal cord that remains undamaged
Types of injuries
Tetraplegia/Quadriplegia: loss of movement and sensation in all limbs, sometimes the head, neck and shoulders
Paraplegia: loss of movement or sensation in the lower torso and lower limbs, this is often called lower spinal cord injury
