Somatosensory System Flashcards
What side of the spinal cord are somatosensory neurons found?
The dorsal side
What side of the spinal cord are the motor neurons found?
The ventral side
What is meant by somatotropic maps?
The brain is organized in regions that correspond to different parts of the body. These regions are called somatotropic maps.
What two types of afferent fibers are part of the somatosensory system?
- The mechanosensory afferent (touch and pressure)
2. The Nocireceptive afferent (pain and temperature)
At what part of the brain will the mechanosensory fibers cross to the other side?
The Caudal Medulla
Where do the nociceptive fibers cross over?
They cross over immediately, in the spinal cord.
How does the mechanosensory fiber lead to an action potential?
The pressure on the skin leads to the phospholipid bilayer of the sensory neuron to go further apart. This drop in tension/pressure between the phospholipids leads to the opening of Na+ channels.
What is the difference between large and small receptive fields?
Large receptive fields have a low precision as stimulations in the field are hard to discriminate and they have a high sensitivity, as every stimulus will result in a response.
Name the types of mechanoreceptors.
- Meissner corpuscle (most abundant, but less sensitive than Merkel)
- Merkel cell (most precise, but less sensitive)
- Ruffini corpuscle (detects the direction of movement)
- Pacinian corpuscle (detects pressure)
What mechanosensors have a large receptive field?
Panacinian and Ruffini
What mechanosensors have a small receptive field?
Merkel and Meissner
What are the slow-adapting sensors and fast-adapting sensors good for?
The slow-adapting can keep feeling whether an object is touched and the rapidly adapting only feel change, but the stimulation quickly dies out.
Where are the receptors for proprioception found and how are they called?
They are found in the muscles.
- Muscle spindles (change in muscle length)
- Golgi Tendon (change in muscle tension)
Together they map the positioning of the limbs
What is a dermatome?
The innervated area of sensory axons of a single dorsal root ganglion.
what nerve mediates sensory input in the face?
Cranial nerve V (trigeminal nerve)
What happens if you lose a finger, for example?
The somatotropic map in the brain changes, so two areas that were unrelated start to represent the area that is missing. (phantom pain)
what nerves feel temperature and pain?
Free nerve endings
What receptors are found on the free nerve endings?
TRP channels that are adapted Ca2+ and Na+ transporters.
When do TRPs open?
They open in reaction to heat and chemical irritants (substances released by damaged tissues)
What is the effect of Capsaicin on the fibers?
Capsaicin affects C-fibers. they bind to the thermoreceptors and open their ion channels. This is perceived as heat by the body.
Why do people perceive acid reflux in the esophagus as the pain of the skin?
The sensory neurons responsible for the feeling of pain from the viscera project on the same neurons in the dorsal horn, making the brain process the information as skin pain.
What types of sensory fibers are there?
- AB - mechanoreceptor
- AD - Thermoreceptor and pain
- C-fiber - unmyelinated thin fibers, used for the longer perception of pain
How is the pain sensation being relieved?
Inhibitory neurotransmitters in the dorsal root ganglions are used to block certain pain signals.
What are the 5 important cell types in the retina? Briefly explain their function
- Photoreceptors (cones are rods) = detect light and create action potentials
- Horizontal cells = interconnect synapses between Bipolar and photoreceptor
- Bipolar cells = transports signals from cones and rods to ganglion cells
- Amacrine Cells = interconnect synapses between bipolar and ganglion
- Ganglion cells = they make up the optic nerve
