Neuroscience Somethesis Steven Youngentob Flashcards
To what kind of stimulus do slowly adapting mechanoreceptors respond?
Enduring
To what kind of stimulus do rapidly adapting mechanoreceptors respond?
At the onset and sometimes the termination of a long stimulus
What is one similarity between the two kinds of tactile receptors (slowly adapting and rapidly adapting)?
They are both more active at the beginning of a stimulus
Name this: the portion of the skin directly innervated by the receptor terminals and the area of adjacent tissue through which a stimulus can be conducted through the receptor.
The receptive field
Areas of the skin most sensitive to touch, ie fingers, have what large or small receptive fields?
Small, and the largest # of receptive fields per unit area.
What type of mechanoreceptor is a Merkel’s cell?
Slowly adapting
What type of mechanoreceptor is a Meissner’s corpuscle?
Rapidly adapting
What type of mechanoreceptor is a Pacinian corpuscle?
Rapidly adapting
What are the two major ascending systems carrying somatosensory information to the cerebral cortex?
- Dorsal column-lemniscal system
2. Anterolateral system
What is the main function of the dorsal column-lemniscal system?
To mediate tactile sensations including vibration sense and proprioception
What is the main function of the anterolateral system?
To carry information mostly about pain and temperature sensation
The tactile information transmitted by the _______ provides crude touch and pressure information, poo localizing ability on the body and little capacity for fine intensity discrimination.
Anterolateral system
- Sacral axons enter the spinal cord and are packed where?
2. The axons added at higher levels are packed at successively more _____ positions.
- Near the midline
2. Laterally
Is the cuneate fascicle more lateral or more midline in the spinal cord?
Lateral
Is the gracile fascicle more lateral or more midline in the spinal cord?
Midline
The dorsal column-lemniscus system has nerve fibers that enter the dorsal column and travel up what side of the body?
Ipsilateral to the ipsilateral side of the caudal medulla
What are the nuclei where dorsal nerves synapse and where are the nuclei located?
Gracile and cuneate nuclei, together called the dorsal column nuclei, in the caudal medulla
What is different about a second order receptive neuron, as compared with a regular receptor neuron?
The second-order receptive neuron has both excitatory and inhibitory regions
How does a receptive field become larger?
It receives more input from primary sensory neurons
T or F: Receptive fields have overlapping areas.
True
What is the medial lemniscus?
The bundle of fibers traveling from the dorsal column nuclei to the brain. They are delivering contralateral information from second order sensory neurons that have decussated upon entering the spinal column.
The fibers of the medial lemniscus synapse on the _____ of the thalamus.
ventral posterior nucleus
How many sections is the ventral posterior nucleus divided into? What are they called?
Two, the medial and lateral division.
The medial division of the ventral posterior nucleus received input from what?
Input from the face
The lateral division of the ventral posterior nucleus receive input from what?
Input from the trunk and limbs
Sensory information about a particular modality from one part of the body is processed by collections of neurons that form what?
Discrete functional units in the thalamus
Within the thalamic nuclei, __1__ is represented mediolaterally and __2__ is represented anteroposteriorly.
- place
2. modality
The cortical region that receives somatosensory input from the central posterior nucleus is located:
in the postcentral gyrus (primary somatosensory cortex)
The projections of the medial and lateral divisions of the VPN are directed to different portions of the postcentral gyrus: Which goes to which side?
The lateral division projects to the medial and superior portions of the postcentral gyrus.
The medial division projects to the lateral portion of the postcentral gyrus.
The somatosensory cortex is subdivided into four cytoarchitectural regions called:
Brodmann’s areas 1, 2, 3a and 3b.
In what subdivisions of the somatosensory cortex do the thalamic fibers terminate?
3a and 3b
The cells 3a and 3b project where in the postcentral gyrus?
1 and 2
What did early electrophysiological experiments show?
That the body surface is represented in the brain in an orderly fashion.
Wilder Penfield found that stimulation of the postcentral gyrus produced tactile sensations where?
On the opposite side of the body
Why were Wilder Penfields experiments important clinically?
They explained how a disturbance in the somatosensory system could be localized clinically.
What is a Jacksonian seizure?
Numbness beginning at the fingertip and progressing to the shoulder, spinal cord and then down the ipsilateral leg
In the most posterior portion of the somatosensory cortex, there are vertical columns that only respond to __1__. These cells are primarily found in areas __2__, but most of all in area __3__.
- When a stimulus moves across the skin in a particular direction
- 1 and 2
- 2
