Spinal anterior horn motor neurons whose axons innervate skeletal muscles are called lower motor neurons. These cells activate skeletal muscles to produce characteristic movements of a body part. The activity of these motor neurons is influenced by two sources. First,…
The olfactory and taste systems sample the rich chemical environment that surrounds us. Information provided by these systems is intimately associated with the enjoyment of foods and beverages. When we refer to the taste of food, what we mean is…
Humans have the ability to control posture and movements of the body and eyes relative to the external environment. The vestibular system mediates these motor activities through a network of receptors and neural elements. This system integrates peripheral sensory information…
Hearing is one of the most important senses. In combination with vision and the ability to speak, it contributes, in a significant way, to the quality of life. In our daily routine, we unconsciously sort out meaningful sounds from background…
Vision is the sensory modality that perhaps captures the imagination more than any other. Phrases such as “He is the apple of my eye,” or “Her eyes flashed with anger,” or “I see what you mean” are common in the…
The somatosensory system conveys information from sensory receptors in the skin, joints, and skeletal muscles that allows one to perceive and respond to stimuli arising either from the external environment or from the position of or the movement of the…
One crucial role of the somatosensory system is to supply the brain with information related to insults that cause tissue damage. These signals ascend the neuraxis in a fiber bundle called the anterolateral system (ALS). Anyone who has used a…
When you reach into your pocket to determine the types of coins present, you are gathering information through the activation of specialized receptors of the somatosensory system. Specifically, the size of a coin is determined by noting the joint angles…
The telencephalon is the largest part of the human brain, constituting about 85% of total brain weight, and is that portion in which all modalities are represented. Various sensory inputs (such as vision and hearing) are localized in some areas,…
Although it is considered by some investigators to be part of the brainstem, the diencephalon is treated here as a portion of the forebrain. The diencephalon includes the dorsal thalamus, hypothalamus, ventral thalamus, and epithalamus, and it is situated between…