Cranial Nerves Lab
Handout Lab 5 - Cranial Nerves: Assessment of Functions
INTRODUCTION
The central nervous system (CNS) consists of the brain and the spinal cord. The CNS receives sensory information from other parts of the body or the body's external environment and transmits motor information to other parts of the body by way of the peripheral nervous system (PNS). The PNS of the human includes 31 pairs of spinal nerves and 12 pairs of cranial nerves. Some nerves contain only motor nerve fibers (efferent fibers); some nerves contain only sensory nerve fibers (afferent fibers); and some nerves contain both sensory and motor nerve fibers (mixed). All spinal nerves are mixed. Cranial nerves
I (olfactory), II (optic), and VIII (vestibulocochlear) are entirely sensory. Cranial nerves III (oculomotor),
IV (trochlear), VI (abducens), XI (accessory), and XII (hypoglossal) are classified as motor, although they do contain proprioceptive afferent fibers. Cranial nerves V (trigeminal), VII (facial), IX (glossopharyngeal), and X (vagus) are mixed. All cranial nerves except the olfactory nerves are connected to the brain stem (medulla, pons, mesencephalon), and all are distributed in the head and neck except the vagi, which also supply structures in the thorax and abdomen. Figure 1.1a shows cranial nerves and their origins and terminations.
Cranial nerve function is commonly assessed as part of a general physical examination of the head, eyes, ears, nose, throat, and neck by a physician, physician's assistant, nurse, or paramedic. More comprehensive examination of cranial nerve functions is usually done by specialists such as neurologists, ophthamologists, optometrists, and audiologists. Basic cranial nerve tests are included in this book because they provide a convenient framework for reinforcing the learning of cranial nerve numbers, names, and functions. More important, they hone skills of observation and reason.
[pic]
Figure 1.1 (a) Cranial Nerve Pathways
INTRODUCTION
The central nervous system (CNS) consists of the brain and the spinal cord. The CNS receives sensory information from other parts of the body or the body's external environment and transmits motor information to other parts of the body by way of the peripheral nervous system (PNS). The PNS of the human includes 31 pairs of spinal nerves and 12 pairs of cranial nerves. Some nerves contain only motor nerve fibers (efferent fibers); some nerves contain only sensory nerve fibers (afferent fibers); and some nerves contain both sensory and motor nerve fibers (mixed). All spinal nerves are mixed. Cranial nerves
I (olfactory), II (optic), and VIII (vestibulocochlear) are entirely sensory. Cranial nerves III (oculomotor),
IV (trochlear), VI (abducens), XI (accessory), and XII (hypoglossal) are classified as motor, although they do contain proprioceptive afferent fibers. Cranial nerves V (trigeminal), VII (facial), IX (glossopharyngeal), and X (vagus) are mixed. All cranial nerves except the olfactory nerves are connected to the brain stem (medulla, pons, mesencephalon), and all are distributed in the head and neck except the vagi, which also supply structures in the thorax and abdomen. Figure 1.1a shows cranial nerves and their origins and terminations.
Cranial nerve function is commonly assessed as part of a general physical examination of the head, eyes, ears, nose, throat, and neck by a physician, physician's assistant, nurse, or paramedic. More comprehensive examination of cranial nerve functions is usually done by specialists such as neurologists, ophthamologists, optometrists, and audiologists. Basic cranial nerve tests are included in this book because they provide a convenient framework for reinforcing the learning of cranial nerve numbers, names, and functions. More important, they hone skills of observation and reason.
[pic]
Figure 1.1 (a) Cranial Nerve Pathways