Peripheral Nervous 13

Question 1

sensory function for touch

Answer 1

• for touch we have free nerve endings and these serve for various functions related to sensory of skin
• free nerve endings can be thermoreceptors
• they can determine temperature and also chemoreceptors for free nerve endings that determine itch, ph

Answer 1

• cranial nerves come off brain
• cranial nerves are all considered peripheral nerves
• peripheral nerves include the nerve coming off the spinal cord and going to their target locations
• so things like the cervical, thoracic, lumbar, and sacral nerve coming off the spinal cord including causa and aguaena

Answer 2

• mechanoreceptors detect pressure although there are the pacinian corpuscles that also detect pressure
• nociception or pain
• so free nerve endings can be responsible for temperature, itch, ph, pressure, and pain
• merkel discs responsible for light pressure
• hair follicle receptors detect hair deflection or hair shaft deflection in the follicle and innervate hair follicles
• meissner’s corpuscle responsible for fine discriminant touch
• pacinian corpuscle responsible for deep touch or pressure (they give a vibratory sensation and detect vibratoy waves and a certain frequency

Answer 3

• bulbous corpuscles and muscle spindles responsible for proprioception or knowing where any muscle, and given stretch is kind of like in three dimensional space
• proprioception is like the ability to close your eyes and know exactly where left arm is in three dimensional space
• innervation going to tendons to determine how effectively or far they stretch

Answer 4

• sensory input to the brain travels from the nerves up into sensory a parent fibers up the spinal cord up the brainstem and then to the thalamus, which is like the sensory relay circuit
• thalmus will organize those signals and then send them off to where they belong on the post central gyrus and the parietal lobe
• post central gyrus is where the homunculus for the somatosensory cortex and in parental lobe
• somatosensory cortex receives all the sensory input from the body and interpreting it
• the thalamus is organizing that sensory input
• its really the sensory relay circuit, the thalamus is, it’ll organize those signals and deploy them to the somatosensory cortex

Question 5

levels of organization

Answer 5

• individual axons are myelinated
• peripheral nerves myelinated by schwann cells and many are myelinating axons
• axon up top and it is myelinated with a myelin sheath
• each individual myelinated peripheral nerve is surrounded by an endoneurium
• several endoneurium encased nerve fibers which are myelinated are surrounded by a perineurium
• several perineurium are organized around blood vessels which nourish them
• perineurium surrounded fibers are organized around central artery and vein which are providing blood flow and removing waste
• entire unit of perineurium encased fibers, fascicles, surround blood vessels
• entire unit encased by epineurium
• epineurium is the greatest and largest organization

Answer 6

• entire epineurium will encompass a thick nerve cord ex. vagus nerve
• thick cord is going to be surrounded by epineurium because that is the highest order of organization is the epineurium
• some peripheral nerves are capable of regeneration
• closer the nerve fibers, the less dramatic the damage

Answer 7

• process in which axon must recover and reconnect to original fiber
• then myelin sheath will recover
• various nerium surroundings will encompass and re encapsulate the fiber
• schwann cells will cover the axons again and nerve can be functional
• only possible in peripheral not central
• central can create new axons and new connections

Answer 8

• cranial nerve 1 - olfactory smell
• cranial nerve 2 - optic for sight
• cranial nerve 3 - ocular motor controlling many aspects of the eye including sympathetic and parasympathetic of the eye and pupil and muscles
• cranial nerve 4 - trochlear, control the superior oblique
• cranial nerve 5 - trigeminal that controls sensory to the face and three branches
• cranial nerve 6 - abducens controls lateral rectus in eye, another extraocular muscle
• cranial nerve 7 - facial responsible for motor to face and control taste in the anterior tongue
• cranial nerve 8 - vestibulococlear for balance and auditory
• cranial nerve 9 - glossopharyngeal for the tongue posterior aspect of the tongue for taste
• cranial nerve 10 - vagus nerve, parasympathetic input into heart, induce bradycardia
• cranial nerve 11 - spinal accessory controls sternocleidomastoid to turn the head side to side and innervates the trapezius for elevating shoulders
• cranial nerve 12 - hypoglossal or motor to tongue

Answer 9

• after L2 spinal nerves coming off spinal cords are cauda equina
• C1-C8 cervical nerves
• T1-T12 thoracic
• L1-L5 lumbar
• S1-S5 sacral
• two sets of roots that come off the ventral aspect of the spinal cord and two sets of roots that come off the dorsal

Answer 10

• anterior horns on the ventral aspect or frontal of the spinal cord responsible for motor
• dorsal horns sensory
• ventral roots, the coming off the front aspect of the spinal cord, the ventral aspect, are going to consistent with anterior horns
• ventral roots carry motor nerves
• dorsal roots carry sensory
• dorsal roots feed into a ganglion

Answer 11

• ganglion is collection of synapsing neurons
• dorsal root ganglion associated with each dorsal root which carries sensory fibers
• so sensory fibers are going to synapse in the dorsal root ganglion
• ventral roots are motor and dorsal are sensory
• ventral roots, which are motor, have efferent fibers
• so signal is coming down from brain into the anterior horns and out through the ventral roots to target organ

Answer 12

• if we are controlling the arms at the level of the spinal cord, the ventral root will come out of the spinal cord
• the command will come from the brain down the anterior horns and then through the ventral roots and then out to the arms to command them to move
• dorsal horn and root contain sensory so they are afferent
• those fibers are coming from the target organ to the spinal cord through the dorsal roots, into the dorsal root ganglion and then into the dorsal roots and then into dorsal horns and up the spinal cord to the brain to communicate that signal back to the brain

Question 13

notes

Answer 13

• 31 spinal nerves
• spinal types: motor and sensory
• sensory = afferent
• motor = efferent
• motor = anterior
• posterior = sensory
• nerve = peripheral
• track = central
• white matter = myelin, faster
• cortex = outer layer
• descending = motor
• ascending = sensory