Chapter 4 - Neuroanatomical Bases by Which Neural Circuits Mediate Behavior

What is the major pathway for somatosensory information called (touch).
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What is the major pathway for somatosensory information called (touch).
The dorsal column-medial lemniscal pathway
How does the dorsal column-medial lemniscal pathway work?
Somatosensory information enters the central nervous system through the dorsal root ganglion cells.

The flow of information ultimately leads to the somatosensory cortex.

Fibers that relay information from different parts of the body maintain an orderly relationship to each other and form a neural map of the body surface in their pattern of termination at each synaptic relay

**CHECK Figure 4-1**
touch
-spinal cord, dorsal root ganglion
-sends to the medulla
-sends to the pons
-sends to the midbrain
-sends to the cerebral cortex
-somatic sensory cortex
Example of a simple behavior being mediated by many parts of the brain
simple act of hitting a tennis ball
tennis player watching an approaching ball uses
visual cortex to judge the size, direction, and velocity of the ball.

The premotor cortex develops a motor program to return the ball.

The amygdala acts in conjunction with other brain regions to adjust the heart rate, respiration, and other homeostatic mechanisms and also activates the hypothalamus to motivate the player to hit well.
To execute the shot, the tennis player utilizes....
The motor cortex sends signals to the spinal cord that activate and inhibit many muscles in the arms and legs.

The basal ganglia become involved in initiating motor patterns and perhaps recalling learned movements to hit the ball properly.

The cerebellum adjusts movements based on proprioceptive information from peripheral sensory receptors.

The posterior parietal cortex provides the player with a sense of where his body is located in space and where his racket arm is located with respect to his body.

Brain stem neurons regulate heart rate, respiration, and arousal throughout the movement.
Involved in storing the memory of returning the tennis ball
The hippocampus

is not involved in hitting the ball but is involved in storing the memory of the return so that the player can brag about it later.
What are the two horns for the gray matter on each side of the spinal cord divided into?

from figure 4-3
Dorsal Horns (posterior)
Ventral Horns (anterior)
What does the dorsal horn contain? (orange)
groups of secondary sensory neurons (sensory nuclei) whose dendrites receive stimulus information from primary sensory neurons that innervate the body's skin, muscles, and joints

-large motor neurons
What does the ventral horn contain? (green)
groups of motor neurons (motor nuclei) whose axons exit the spinal cord and innervate skeletal muscles.

-smaller neurons
Fibers of the gracile fascicle carry...
somatosensory information from the lower limbs
Fibers of the cuneate fascicle carry...somatosensory information from the upper bodySomatosensory pathway for touch/stretchepicritic systemSomatosensory pathway for pain/temperatureprotopathic systemWhat are the four major groups of the nuclei of the thalamusanterior medial ventrolateral, and posterior with respect to the internal medullary lamina, a sheet-like bundle of fibers that runs the rostrocaudal length of the thalamusFunction of the anterior groupreceives its major input from the mammillary nuclei of the hypothalamus and from the presubiculum of the hippocampal formation. The role of the anterior group is uncertain, but because of its connections, it is thought to be related to memory and emotion. The anterior group is mainly interconnected with regions of the cingulate and frontal corticesFunction of the medial groupconsists mainly of the mediodorsal nucleus. This large thalamic nucleus has three subdivisions, each of which is connected to a particular portion of the frontal cortex. The nucleus receives inputs from portions of the basal ganglia, the amygdala, and midbrain and has been implicated in memory and emotional processingFunction of the ventrolateral groupconsists mainly of the mediodorsal nucleus. This large thalamic nucleus has three subdivisions, each of which is connected to a particular portion of the frontal cortex. The nucleus receives inputs from portions of the basal ganglia, the amygdala, and midbrain and has been implicated in memory and emotional processingFunction of the posterior groupincludes the medial and lateral geniculate nuclei, the lateral posterior nucleus, and the pulvinar. The medial geniculate nucleus is a component of the auditory system and is organized tonotopically based on the sound frequency information carried by its inputs; it conveys auditory information to the primary auditory cortex in the superior temporal gyrus of the temporal lobe. The lateral geniculate nucleus receives information from the retina and conveys it to the primary visual cortex in the occipital lobe. Compared to rodents, the pulvinar is enlarged disproportionately in the primate brain, especially in the human brain, and its development seems to parallel the enlargement of the association regions of the parietal, occipital, and temporal cortices. It has been divided into at least three subdivisions and is extensively interconnected with widespread regions of the parietal, temporal, and occipital lobes, as well as with the superior colliculus and other nuclei of the brain stem related to vision6 layers of the neocortex1) Molecular Layer 2) external granule- dense 3) external pyramidal- moderate 4) internal granule-dense 5) internal pyramidal- sparse 6) polymorphic- moderateDescending Lateral corticospinal pathway FlowExample: playing the piano Originate in the primary motor cortex and terminate in the ventral horn of the spinal cord Flow Path -primary motor cortex -internal capsule -midbrain -pons -medulla (pyramid fiber) -medulla - spinal cord juncture (pyramidal decussation) -through the lateral corticospinal tract - cervical spinal cord - lateral intermediate zone and lateral motor nucleiPrincipal components of voluntary movement of the motor system-motor cortex -basal ganglia -thalamus -midbrain cerebellum -spinal cord