Lec 04- General Sensory Mechanisms II Flashcards
What makes up the primary somatosensory area?
Brodmann’s area 1,2,3
What makes up the somatosensory association area?
Brodmann’s area 5, 7
What are the results of widespread bilateral excision of somatosensory area I?
Loss of ability to:
- Localize discretely the different sensations in different parts of the body (crude localization still possible)
- Judge critical degrees of pressure against the body
- Judge weights of objects
- Judge shapes or forms (asterognosis)
- Judge texture of materials
**Pain and temperature sense = still preserved but poorly localized
Where does the somatosensory area II receive signals from?
- Brain stem (transmitted upward from the body bilaterally)
- Secondarily from somatosensory area II
- Other sensory areas of the body (visual and auditory)
What is required for function of somatosensory area II?
Projections from somatosensory area I
What does the removal of somatosensory area II do to the neurons in somatosensory area I?
Removing II has no apparent effect on response of neurons in I
Which layers of the somatosensory cortex receive input signals from lower brain centers?
1
2
Which layer of the somatosensory cortex has large neurons in it that project to distant areas such as basal nuclei, brainstem, and spinal cord?
5
6
Which layers of the somatosensory cortex send information through corpus callosum to the opposite hemisphere?
2
3
Which layer of the somatosensory cortex has its axons project to the thalamus?
6
How are receptor potentials created?
By opening modality gated channels (Na+ channels) that are opened in response to membrane deformation caused by the touch or pressure
Touch/pressure > membrane deformation > Na+ channel opens > receptor potential
if the receptor potential is strong enough (through summation), it may generate an AP at the _______________ on the primary sensory neuron
1st node of Ranvier
Where do the primary sensory neurons originate from?
from peripheral receptors
Merkel’s receptors
Through which roots of the spinal nerves do the primary sensory neurons enter the spinal cord?
dorsal roots
Where are the cell bodies of the primary sensory neurons located?
dorsal root ganglia
Where do the primary sensory neurons synapse?
in spinal cord with secondary neurons
Where do the secondary sensory neurons originate from?
spinal cord gray matter
Where do the secondary sensory neurons travel through?
myelinated columns of the spinal cord
Do the secondary sensory neurons decussate?
YES
Where do the secondary sensory neurons synapse?
thalamus with tertiary neurons
Where do the tertiary sensory neurons travel through?
internal capsule
Myelinated pathway between thalamus and some of the basal nuclei
Where do the tertiary sensory neurons synapse?
somatosensory cortex
Where does two-point discrimination touch travel?
dorsal column-medial lemniscal pathway
What is two-point discrimination touch?
the ability to distinguish 2 separate points as close as 2mm apart
Why is lateral inhibition important?
- Blocks the lateral spread of excitatory signals
- Increases the degree of contrast in the cerebral cortex
