On the somatosensory homunculus, which of the following parts would be the largest
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The somatosensory system consists of primary, secondary, and tertiary neurons.
Sensory receptors housed in the dorsal root ganglia project to secondary neurons of the spinal cord that decussate and project to the thalamus or cerebellum.
Tertiary neurons project to the postcentral gyrus of the parietal lobe, forming a sensory homunculus.
A sensory homunculus maps sub-regions of the cortical postcentral gyrus to certain parts of the body.
Key Terms
decussate: Where nerve fibers obliquely cross from one lateral part of the body to the other.
postcentral gyrus: A prominent structure in the parietal lobe of the human brain and an important landmark that is the location of the primary somatosensory cortex, the main sensory receptive area for the sense of touch.
organization: The quality of being constituted of parts, each having a special function, act, office, or relation; to systematize.
thalamus: Either of two large, ovoid structures of gray matter within the forebrain that relay sensory impulses to the cerebral cortex.The somatosensory system is distributed throughout all major parts of our body. It is responsible for sensing touch, temperature, posture, limb position, and more. It includes both sensory receptor neurons in the periphery (eg., skin, muscle, and organs) and deeper neurons within the central nervous system.
Structure
A somatosensory pathway will typically consist of three neurons: primary, secondary, and tertiary.
In the periphery, the primary neuron is the sensory receptor that detects sensory stimuli like touch or temperature. The cell body of the primary neuron is housed in the dorsal root ganglion of a spinal nerve or, if sensation is in the head or neck, the ganglia of the trigeminal or cranial nerves.
The secondary neuron acts as a relay and is located in either the spinal cord or the brainstem. This neuron’s ascending axons will cross, or decussate, to the opposite side of the spinal cord or brainstem and travel up the spinal cord to the brain, where most will terminate in either the thalamus or the cerebellum.
Tertiary neurons have cell bodies in the thalamus and project to the postcentral gyrus of the parietal lobe, forming a sensory homunculus in the case of touch. Regarding posture, the tertiary neuron is located in the cerebellum
Sensory receptors housed in the dorsal root ganglia project to secondary neurons of the spinal cord that decussate and project to the thalamus or cerebellum.
Tertiary neurons project to the postcentral gyrus of the parietal lobe, forming a sensory homunculus.
A sensory homunculus maps sub-regions of the cortical postcentral gyrus to certain parts of the body.
Key Terms
decussate: Where nerve fibers obliquely cross from one lateral part of the body to the other.
postcentral gyrus: A prominent structure in the parietal lobe of the human brain and an important landmark that is the location of the primary somatosensory cortex, the main sensory receptive area for the sense of touch.
organization: The quality of being constituted of parts, each having a special function, act, office, or relation; to systematize.
thalamus: Either of two large, ovoid structures of gray matter within the forebrain that relay sensory impulses to the cerebral cortex.The somatosensory system is distributed throughout all major parts of our body. It is responsible for sensing touch, temperature, posture, limb position, and more. It includes both sensory receptor neurons in the periphery (eg., skin, muscle, and organs) and deeper neurons within the central nervous system.
Structure
A somatosensory pathway will typically consist of three neurons: primary, secondary, and tertiary.
In the periphery, the primary neuron is the sensory receptor that detects sensory stimuli like touch or temperature. The cell body of the primary neuron is housed in the dorsal root ganglion of a spinal nerve or, if sensation is in the head or neck, the ganglia of the trigeminal or cranial nerves.
The secondary neuron acts as a relay and is located in either the spinal cord or the brainstem. This neuron’s ascending axons will cross, or decussate, to the opposite side of the spinal cord or brainstem and travel up the spinal cord to the brain, where most will terminate in either the thalamus or the cerebellum.
Tertiary neurons have cell bodies in the thalamus and project to the postcentral gyrus of the parietal lobe, forming a sensory homunculus in the case of touch. Regarding posture, the tertiary neuron is located in the cerebellum
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