Lecture 13: Somatic Sensation Flashcards
Is the dorsal root ganglion considered to be part of the central or peripheral process?
the central process
Describe the location of the different parts of the primary afferent neuron
the sensory endings of the axon are the sensory receptors and these are located in places like the skin
there is axon which leads to these sensory endings and this makes up the peripheral process
the cell body is located in the dorsal root ganglion
there is the central process and the dendrites in the CNS
What are the two different somatosensory pathways called?
anterolateral and dorsal column pathway
Describe the anterolateral pathway
the axons (afferent) cross over at the level of the spinal cord (across and forward) and then go up to the brainstem
What is the anterolateral pathway for?
pain and temperture
Describe the dorsal column pathway
this enters the dorsal root and stays on that side then crosses over higher (in the medulla oblongata)
What is the dorsal column pathway for?
sensory modalities of fine touch (tactile sensation), vibration and proprioception
Receptive fields vary in _______ and _______ on different parts of the body
size and density
What is the reticular activating system?
Network of _______ located in the _______ _______ that project ______ to the ________ to mediate _______ as well as both ________ to the _______ and directly to the ________ for activation of _______, desynchronised cortical _______ patterns. This is for __________ and _________ to the cerebellum
network of neurons located in the brain stem that project anteriorly to the hypothalamus to mediate behaviour, as well as both posteriorly to the thalamus and directly to the cortex for activation of awake, desynchronised cortical EEG patterns.
this is for proprioreception and touch to the cerebellum
What is the purpose of a sensory receptor in the skin?
to convert a physical stimulus to action potentials in the primary sensory neuron via the process of transduction
What is the process of transduction?
When one form of energy is converted to another
What are the 4 different “nodes”/types of receptors in the skin?
- temperature (thermoreceptors)
- position of limbs (proprioreceptors)
- touch receptors
- pain (nocireceptors)
Describe thermoreceptors
different types are more active at warm or cold temperature ranges, especially responsive to a changing temperature
Describe the proprioreceptors
these detect position in space and are muscle spindles, golgi tendon organs and joint capsules
In a proprioreceptor, what is wrapped around the muscle spindle and why is this?
nerve endings are wrapped around the muscle spindle to give sensory information about changes in muscle length
What does the golgi tendon organs detect?
muscle tension
What are touch receptors (mechanoreceptors) sensitive to?
mechanical deformation due to stretch, pressure (they detect rapid changes)
What do pain receptors respond to?
extreme mechanical, temperature, and/or chemical stimuli
What are 5 different touch receptors?
tactile (Meissner's corpuscle) tactile (merkel's) corpuscle free nerve endings Pacinian corpuscle Ruffini corpuscle
Describe what Meissner corpuscles detects and why their location is important?
this is to detect light touch
they are located in the folds of non-hairy skin which is important for the interaction of our body surface with something that we are touching
What do pain receptors look like and where are they located?
pain fibres are branching to have a wide receptive field everywhere in the body except in the brain
Where is the pacinian corpuscle located? Why is this important? What does it detect?
it is located deep in the skin which allows for mechanical transduction over quite a large area of skin surface
it detects deep pressure
Describe the Ruffini corpuscles
what are they?
what do they give feedback about?
they are stretch receptors that are sensitive to orientation and what direction the skin is being pulled
it gives feedback about the position of joints in fingers and tactile sensation
Describe the hair receptor
there are fine axons around the basis of the hair
this is the part of the somatosensory sensation because it lets us know about air flow