Ascending And Descending Pathways Flashcards
What are thermoreceptors?
Temperature response
Cold and hot exist
Some in eye cause vasodilation/constriction
Threshold for pain found here
What is a mechanoreceptor?
Receives mechanical stimulus
Responds to stretch [Golgi tendon, muscle spindle fibers]
What are osmoreceptors?
Responders that regulate fluid intake and release
Monitor osmotic level of blood
Where are osmoreceptors found?
Within the brain and kidney
What are chemoreceptors?
Respond to changes in pH (7.42)
Where are chemoreceptors found?
Within tissue and hypothalamus
What are nociceptors?
Responders for pain
Lets us know something is potentially destroying tissue
Where are afferent receptor cell bodies located?
Dorsal root ganglion
What is the largest organ and greatest receptor?
The skin
Has mostly mechanoreceptors
What allows skin to be able to desensitize?
It has fast and slow adapting receptors
Describe the monosynaptic reflex arc pathway.
Sensory receptor -> afferent neuron -> interneuron (to motor neuron, excitatory or inhibitory) -> efferent neuron
What type of epithelium is skin?
Keratinized stratified squamous epithelium
What’s the name for hairless skin?
Glabrous skin
What are the functions of skin?
Protection
Prevention of evaporation
Direct contact with world
What type of somatosensory receptor is most common in skin?
Mechanoreceptors
Which mechanoreceptor is rapid-adapting, encapsulated, and responsible for light touch?
Meissner’s corpuscles
Which mechanoreceptor is responsible for light touch and tickling and is slow-adapting?
Merkel’s discs
Which mechanoreceptor is responsible for deep pressure, is encapsulated, and is slow-adapting?
Ruffini endings
Which mechanoreceptor is onion-like, responsible for detecting vibration and deepest pressure, and is fast-adapting?
Pacinian corpuscles
Which mechanoreceptor is also found in the pancreas?
Pacinian corpuscles
What size are Pacinian corpuscles?
1-4mm
The order of 2-point discrimination:
:index finger -> thumb -> lip -> big toe -> forearm -> sole -> back -> calf
How does a rapid-adapting response graph look?
Initial response peak when you first stimulate, then another peak when you stop
Which mechanoreceptors are fast-adapting?
Pacinian corpuscles and Meissner’s corpuscles
Which mechanoreceptors are slow-adapting?
Merkel’s discs and Ruffini endings
How does a slow-adapting response graph look?
Fires the most at initial response and continues firing during the duration, firing rate decreases until stimulus is removed
Which mechanoreceptors are mostly in the hand?
Meissner’s corpuscles and Pacinian corpuscles
What is lateral inhibition?
Stimulating nerves lateral to nerve that was initially stimulated
Aa afferent axon characteristics:
Most myelination, fastest
13-20um
80-120 m/s
Proprioceptors of skeletal muscle
AB afferent axon characteristics:
6-12 um
35-75 m/s
Mechanoreceptors of skin (touch)
A£ afferent axon characteristics:
1-5 um
5-30 m/s
Pain and temperature receptors
C afferent axon characteristics:
No myelination, slowest
0.2-1.5 um
0.5-2 m/s
Temperature, pain, and itch receptor
How does the dorsal column medial lemniscus pathway travel up the spinal cord?
Ipsilateral
How does the anterolateral pathway travel up the spinal cord?
Contralateral
Why are the lateral dorsal columns of the spinal cord larger?
It has to carry sacral and lumbar information
What are dermatomes?
Spinal nerve distribution areas
Disease follows these
Shingles characteristics
Follows dermatomes
Is unilateral
About an inch wide
Most dangerous one is along ophthalmic division of CN5
Characteristics of fast pain:
Stimulation from mechanical and thermal receptors
A£ fibers carry signal
Prickling sensation
Easily localized
Characteristics of slow pain:
Stimulation of polymodal nociceptors
C fibers carry signal
Poorly localized
The dorsal horn contains:
: Cell bodies of interneurons, where afferent neurons terminate
The lateral horn contains:
: cell bodies of autonomic efferent nerve fibers
The ventral horn contains:
: cell bodies of somatic efferent neurons
How does acupuncture work?
It stimulates endogenous morphine to inhibit pain
Opiate neurons inhibit pain neurons from going to the thalamus
What is the main descending pathway?
Corticospinal pathway
Corticospinal pathway
Large fiber bundles -> decussation at brainstem -> terminate on LMN in ventral horn of SC
Rubrospinal secondary pathway
Red nucleus -> Ipsilateral in SC -> ventral horn
Which pathway can be regenerated with physical therapy after injury?
Rubrospinal pathway
Which feedback loop causes ALS?
Spinal cord -> muscle contraction and movement -> sensory receptors -> spinal cord
What happens from the frontal cortex to the premotor cortex?
Analysis and getting ready
What happens at the local level of voluntary movements?
The movement
Specific muscles that move
What percent of force muscle degeneration between 30-80 years of age?
30-40%
How does Polio affect the body?
It destroys motor neurons
How does ALS affect the body?
Affects motor neurons
Excitotoxic: over excitation of glutamate to motor neurons, extra Ca2+ in excels
What type of disorder is muscular dystrophy?
X-linked
What are costamers?
A structural binding protein that links mayo fibrils to sarcolemma
What protein is responsible for the effects of muscular dystrophy?
Dystrophin
Why does muscular dystrophy occur?
Dystrophin protein built incorrectly -> as myofibril does it’s job it rips the sarcolemma and muscle atrophies
