Somatosensory Flashcards
How does receptive field relate to two point discrimination?
The receptive field is the area that, when stimulated, causes a membrane potential change in a given neuron. Small receptive fields are found in areas like the fingertips where receptor density is high. In small receptive field areas, the individual is able to discriminate small variations in sensory input.
What is a proprioceptive receptor?
Respond to static limb and joint posture or dynamic movement of limb
Meissner’s Corpuscles
- Location
- Size of receptor field
- What they sense
- Dermal papillae in hairless skin
- Small
- Vibration (5 - 40 Hz)
The golgi tendon organ measures […] and consists of […] fibers
Muscle force, tension
A_alpha - slow adapting
Free nerve endings have a […] receptive field
Large
The attached image is a cross-section of the postcentral gyrus or somatosensory cortex with labeled Brodmann areas. What does each area do?
3a - proprioception (deep)
3b - cutaneous receptors (mechanoreceptors)
1 - cutaneous receptors (mechanoreceptors)
2 - proprioception (deep)
5 - vision and proprioception
7 - texture and tactile feedback
Merkel’s Disks
- Size of receptor field
- What they sense
- Small
- Pressure that is discrete, small indentations in skin
What are the 2 fiber types that sense pain?
A_delta (III) and C (IV) fibers
Explain what referred pain is.
Visceral and cutaneous nociceptor axons enter the spinal cord by the same route. Within the spinal cord, there is substantial mixing of information from these two sources. The cross-talk gives rise to referred pain, which is when visceral nociceptor activation is perceived as a cutaneous sensation.
Nociceptors
- Where are these not found
- What are the 2 types and what do they respond to?
- Two special subtypes
- Brain
- Adelta - respond to mechanical injury accompanied by tissue injury
- C polymodal - respond to mechanical, thermal and chemical stimuli
- Thermonociceptors - respond to extreme heat
- Chemonociceptors - respond to tissue damage, inflammation and insect venom
Pruriceptors
- Type of sensation conducted
- Type of fiber found in
- Where located
- Receptive field
- Itch
- Histamine selective C-fibers
- Epidermis and epidermal/dermal transition layer, not in dermis
- Large
Crude touch receptors
- Crude touch results from the stimulation of […] that act as […] threshold mechanoreceptors
- Stimuli they respond to
- Stimuli that […] result in tissue damage
- free nerve endings; high
- Pinch, rub, squeeze, stretch
- Do not
The muscle spindle consists of a nuclear bag fiber type and nuclear chain fiber type.
- What are the nerve fibers associated with each of these
- What do they sense?
Nuclear bag
- A_alpha - slow adapting
- Length, rate of change of length, velocity
Nuclear chain
- A_beta - slow adapting
- Length and tension
What is the difference between pain and nociception?
- Nociception is the sensory process that provides the signals that trigger pain
- Pain is the feeling or perception of unbearable sensations arising from part of the body
Ruffini endings (as proprioceptive receptors) measure […] and are made of […] fibers
Joint movement and pressure
A_alpha - slow adapting
If given a blank representation of the somatosensory cortex (or motor cortex really) as below, how should you be able to distingish which areas of the cortex correspond to areas of the body?
What is hyperalgesia?
What is allodynia?
- Increased sensitivity of part of the body to nociceptive stimuli
- Pain provoked by a normally non-painful stimulus
What are transient receptor potential channels?
Specialized surface membrane receptors that transduce thermal sensation. They help confer temperature senstivitiy of the receptor. They are ion channels (Ca2+, Mg2+, Na+)
Pacinian corpuscles
- Location
- Size of receptive field
- What they sense
- Deep in dermis, fascia of muscle and bone etc.
- Large
- Vibration (60Hz to 300 Hz)
What are the types of proprioceptive receptors?
Muscle spindles
Golgi tendon organs
Ruffini endings
Thermoreceptors
- What are the 2 types
- Types of fibers
- Respond to warmth and those respond to cold
- A_delta (III) and C (IV) fibers
What types of receptors are mechanoreceptors?
Pacinian corpuscles
Meissner’s corpuscles
Ruffini Endings
Merkel’s disks
Hair cells
Mechanoreceptors are sensitive to […] and have mechanosensitive […].
Bending and stretching
Ion channels
Nociceptors are activated by […]
Stimuli that have the potential to damage tissue
What is the adaptation rate to a stimulus?
The rate at which a stimulus, although present, ceases to cause a firing response in the cell
Hair follicles
- What they sense
- How they sense it
- Motion, direction, velocity, orientation
- Bending hair causes deformation of follicle which in turn stretches, bends or flattens nearby nerve endings which increase or decrease their AP firing rate
Ruffini Endings
- Location
- Size of receptor field
- What they sense
- Deep in dermis, fascia around muscle and bone, etc.
- Large
- Stretch
