Week 4 Flashcards
When someone is spinning in circles quickly and they stop, why do they feel like they are still spinning in the opposite direction even though no movement is occuring?
This is possible because when they are spinning around quickly they are accelerating causing depolarization and increased firing rates. When they stop, the reason they feel like they are spinning in the opposite direction is because the deacceleration is leading to hyperpolarization and a decrease in firing rates in the opposite direction
Why does someone get the spins when they drink too much?
- alcohol is a blood thinner (decreased blood density)
- the density between the endolymph and hair cells is disrupted/imbalanced
- less density in cupula, hair celld more artificially
Describe each of the words in Benign Paroxysmal Positional Vertigo
Benign - not life threatening
Paroxysmal - sudden, brief epochs
Positional - symptoms triggered by specific head positions or rotations
Vertigo - false sense of rotational motion; mild to intense dizziness
In which population is BPPV present in mostly?
Older adults
What is the cause of BPPV?
- idiopathic (unknown cause)
- hit to the head
What is the pathophysiology of BPPV?
- otolith dislodged into semicircular canal
- especially when lying down
- canal becomes more sensitive
What is the treatment for BPPV (in posterior canal)
epley maneuver: direct crystal out of the canal
- nystagmus
Meniere’s disease is typically present unilaterally. What does this mean?
affects only one side of an organ, the body, or another structure.
What is the cause of Meniere’s disease?
idiopathic
What is the pathophysiology of Meniere’s Disease?
- excess fluid in the labyrinth (canals)
- in turn increases endolymphatic pressure
- decreased firing in affected side and increased firing on intact side
- sense of spinning
Name and describe all of the sensory receptors
- Chemoreceptors: chemical concentrations
- Thermoreceptors: changes in temperature
- nocciceptors: pain stimulus
Mechanoreceptors: mechanical changes
What are the A-fibers of nociceptors?
detect sharp localized pain
Thermoreceptors detect cold ____ more than heat receptors
3x
What are the C-fibers of nociceptors?
Dull, burning, delayed pain
Tactile/cutaneous receptors detect…
touch, pressure and vibration
Name some mechanoreceptors
cutaneous, baroreceptors, proprioceptors
What do baroreceptors detect?
blood pressure changes (autonomic nervous system)
What do proprioceptors detect?
position of joints (eg. muscle spindles) - arguable cutaneous can provide information about position of joint as well
What axon innervates cutaneous receptors?
Aβ
How is stimulus intensity/duration signaled?
with mechanoreceptors, signals can be modulated by two factors: the duration and strength of stimulus
i.e. longer and stronger stimulus leads to increased firing rate and increased neurotransmitter release
Tonic receptors do what?
slowly adapt to continual stimulation
Phasic receptors do what?
rapidly adapt to continual stimulation, then are reactivated when stimulus end
Cutaneous receptors under skin provide information about…
vibration, pressure, and temperature
What are cutaneous receptive fields?
a neuron’s cutaneous receptive field (RF) is the area of skin that, when stimulated, produces or changes responses in the neuron
- encompasses the spatial extent of the receptor surface from which the sensory neuron recieves input
What is a hot spot within a receptive field?
area that is most sensitive
Receptive fields can vary, depending on the…
location (anatomy)
Describe superficial receptors (type 1)
- smaller receptive fields
- lie close along the epidermis
- are densely packed with multiple hot spots
Describe deep receptors (type 2)
- larger receptive fields with only one hot spot
What are polysynaptic pathways?
mediate flexion and cross-extension reflexes
- e.g. excites extensor muscles of the contralateral limb to aid in “withdrawl” from the nociceptors afferent of the ipsilateral limb (pained side)
