Chaper 10 Flashcards
First order neurons
bring information from sensory receptors into the spinal cord
Second- order neuron
Conveys information between the spinal cord or brainsten to the thalamus
Third-order neuron
Conveys in formation from the thalamus to the cerebral cortex
Cutaneous
Sensory information from the skin
Cutaneous sensory information includes
Touch, nociception, and temperature
Nociception
The perception of tissue damage or potential tissue damage
Proprioception
Provides information about the position of your body in space with out the need for visual conformation
Light touch
Nonpainful (innocuous) vibration, skin stretch, and skin pressure they communicate
Ex. Feeling of coffee cup slipping out of your hands
Discriminative touch
Allows someone to specifically localize where along the skin a stimulus is occurring
Crude touch
Provides information that a mechanical stimuli has occurred
Conveyed by free nerve endings
Tonic receptors
Respond the entire time a stimulus is present
Ex. Pressure of Holding coffee cup in your hands
Phasic receptors
Adapts to a constant stimulus and stop responding wile the stimulus is still present
Ex. Pressure after putting watch on wrist
Musculoskeletal afferents in declining diameter order
Ia, Ib, II, III, and IV
Cutaneous afferents in declining diameter order
AB, AO, C
Polymodal
Small diameter primary afferents (III, IV, AO, and C)
Polymodal function
Transit signals from multiple modalities, including mechanical, thermal, and chemical stimuli
Silent nociceptors
Insensitive, become spontaneously active and respond to mechanical stimuli following tissue damage
Peripheral sensitization
Increased pain following tissue injury
Nociceptors fire more action potentials in response to a stimulus
Receptive field
The area of skin innervated by a single afferent neuron
Small distally and large proximally
Dermatome
Area of skin innervated by axons that enter the spinal cord through a single dorsal root
Dermatome are used to diagnose
a lesion affecting a single nerve root and to determine the sensory level affected by a spinal cord injury
If a lesion occurs in the peripheral nerve
Sensory impairment will be in the radial nerve
If a lesion involves a spinal nerve root
The sensory impairment will be in the C7 Dermatome
Large afferents (I and II) innervate
The muscle spindle
Small afferents (III and IV)
Convey nociceptive information
Muscle spindle
Sensory organ in muscle consisting of muscle fibers, sensory endings, and motor endings
Embedded in skeletal muscle
Intrafusal fibers
Specialized muscle fibers inside the spindle
Contractile only at their ends
Provide sensation
Extrafusal fibers
Ordinary skeletal muscle fibers outside the spindle
Larger than intrafusal
2 types of intrafusal fibers
Nuclear bag fibers
Nuclear chain fibers
Nuclear bag fibers
Have a clump of nuclei in the central region
Nuclear chain fibers
Have nuclei arranged single file
2 types of afferents
Type Ia afferents
Type II afferents
Type Ia afferents
Wrap around the central region of both nuclear bag and chain fibers
Phasic receptors
Exhibit maximal discharge during quick stretch of the muscle
Very fast
Type II Afferents
End mainly on nuclear chain fibers and some bag fibers adjacent to the type Ia afferents
Tonic receptors
Exhibit sustained firing that is proportional to the amount of stretch placed on the muscle
Gamma motor neurons
Maintains sensitivity of the spindle throughout the normal range of muscle lengths Fire, casing the ends of intrafusal fibers to contract
Gamma dynamic axons
Innervate the contractile end of nuclear bag fibers to adjust their sensitivity to the velocity of muscle length changes
Gamma static axons
Innervates the contractile ends of nuclear chain fibers and some nuclear bag fibers to tune their sensitivity to static muscle stretch
Golgi tendon organs
Encapsulated nerve endings woven among the collagen strands of the tendon near the musculotendinous junction
Information is transmitted into the spinal cord by type Ib afferents 
Joint receptors 
Respond to mechanical deformation of the capsule and ligaments
Ruffini’s endings
In the joint capsule, tonic receptors
Signal the extremes of joint range and respond more to passive than active movement
Paciniform corpuscles
In joints, Phasic receptors
Respond to movement and are silent when joint position is constant
Ligament receptors
Similar to golgi tendon organs and signal tension
Free nerve endings
Most often stimulated by inflammation
Multiple dendrites, one of the slowest conducting
Herpes Zoster or shingles
Components of varicella-zoster virus
Irritates and inflames the nerve and nerve endings causing pain and loss of cutaneous small diameter afferents
Virus released into the skin causing painful rash with eruptions
Usually limited to one or two adjacent unilateral Dermatomes
Infection is in dorsal root ganglion
Postherpetic neuralgia
Severe pain that persists longer than 120 days
Shingles treatments
Antiviral drugs, analgesic medications (glucocorticoids, acetaminophen, tramadol, nonsteroidal anti-inflammatory drugs, opioids)
Neuropathy
Dysfunction or pathology of one or more peripheral nerves
Lyrica used for neuropathic pain in feet
Progabelin side effects: makes you slow and sleepy
Somatosensory gain of function
Hypersensitivity and or spontaneous pain
Somatosensory loss of function
Decreased or total loss of somatosensation
Loss may be partial or complete
Sensory loss proceeds in the order of descending axon diameter
- Conscious proprioception and light touch
- Cold
- Fast nociception (interpretated as sharp pain)
- Heat
- Slow nociception (interpreted as aching pain)
Ataxia
Incoordination that is not due to weakness
3 types: sensory, vestibular, cerebellar
Romberg test
Used to distinguish between cerebellar ataxia and sensory ataxia
Sensory ataxia have better balance when eyes are open
Cerebellar ataxia have difficulty maintain balance with eyes open and closed
Stenosis
Narrowing
Spinal stenosis
Narrowing of spinal canal
Spondylosis
Arthritic changes to vertebral column
Coronary arterial stenosis
Blockage in coronary artery because of plaque build up
In ppl with High cholesterol
Necrotic
When tissue dies leading to need for amputation
Stocking glove pattern
Ppl with diabetes
Sensory loss, numbness, and pain or burning sensations in distal limbs
Axon type C
Slowest acting
Small diameter and unmyelinated
Meissner’s corpuscles
Sensitive to light touch
Phasic receptors
Merkel’s discs
Sensitive to pressure
Tonic receptors
Ruffini’s corpuscles
Sensitive to stretching of the skin
Detect slippage of object in hand
Tonic receptors
Synovial joints
Most common
Have synovial fluid surrounding joint in joint capsule
Ex. Shoulder, hip, elbow, knee
Supraspinal
Helps control right amount of tension in muscle spindle
