Cranial Nerve Lab
- Due Apr 30, 2021 at 11:59pm
- Points 105
- Questions 11
- Time Limit None
- Allowed Attempts Unlimited
Instructions
Cranial Nerves
HASPI Medical Anatomy & Physiology
Neurons
The neuron is the cell of the nervous system capable of conducting and sending nerve impulses throughout the body. All neurons share the same basic structure, including a cell body, dendrites, and axons. The cell body, or soma, holds the nucleus and major organelles of the neuron. Nerve impulses are generated in the cell body and the branch-like fibers called dendrites that extend out from the cell body. Once the nerve impulse has been generated, it flows down the dendrite, through the cell body, and down the axon.
The axon is an extension of the neuron that contacts other neurons to propagate (send or continue) the nerve impulse to its target. The axon can branch several times at its end and these branches are called axon terminals. Many axons are also coated with a lipid covering called the myelin sheath, created by Schwann cells that are responsible for insulating and speeding up nerve impulses.
Just as there are many different types of cells in the body that each perform a specific function, there are also a wide variety of neurons. Neurons can be classified by shape, the direction they relay information, the neurotransmitter they produce, or the location in the body. The following table provides a few examples of different types and classifications of neurons.
|
Classification of Neurons |
|
|
Type of Neuron |
Description |
|
Direction of Impulse |
|
|
Sensory or Afferent Neurons |
Have specialized receptors that receive external stimuli and send it to the CNS; the 5 senses: touch, vision, sound, taste, smell |
|
Motor or Efferent Neurons |
Transmit impulses from the CNS to glands and muscles throughout the body |
|
Interneurons or Association Neurons |
Only found in the spinal cord and brain; capable of relaying information between sensory, motor, and interneurons |
|
Polarity of Axon and Dendrite |
|
|
Unipolar Neuron |
Dendrite and axon originate from the same location |
|
Bipolar Neuron |
Has a single dendrite and an axon at opposite ends of the cell body |
|
Multipolar Neuron |
Has more than two dendrites with an axon that projects from the cell body |
|
Shape and Location in the Body |
|
|
Purkinje |
Huge neurons in the cerebellum |
|
Basket |
Found in the cortex and cerebellum |
|
Pyramidal |
Pyramid-shaped cell body |
|
Type of Neurotransmitter Produced |
|
|
Cholinergic |
Produce the neurotransmitter acetylcholine |
|
GABAergic |
Produce the neurotransmitter gamma aminobutyric acid (GABA) |
Nerves
Nerves are bundles of axons that extend out from the CNS into the body. Each axon is surrounded by a protective tissue layer called the endoneurium. Bundles of axons together in a group are called fascicles, and each fascicle is surrounded by perineurium. Bundles of fascicles are wrapped together with epineurium to make a nerve. Nerves are generally categorized into two groups depending on where they originate. Spinal nerves are connected to the spinal cord, and cranial nerves are connected directly to the brain. Humans have 31 pairs of spinal nerves and 12 pairs of cranial nerves.
The Cranial Nerves
Most of the cranial nerves extend from the brainstem at the base of the skull, but cranial nerves I and II actually extend from the cerebrum. Cranial nerves are numbered I-XII. The following table is a summary of the number, name, and function of the cranial nerves.
|
Cranial Nerve |
Sensory or Motor |
Function |
|
|
I |
Olfactory |
Sensory |
Olfaction, also known as smell |
|
II |
Optic |
Sensory |
Vision |
|
III |
Oculomotor |
Motor |
Eye movement, pupil dilation |
|
IV |
Trochlear |
Motor |
Eye movement |
|
V |
Trigeminal |
Both |
Sensation in the skin on the face and head, mastication (chewing) |
|
VI |
Abducens |
Motor |
Eye movement |
|
VII |
Facial |
Both |
Facial movement, taste, saliva, and tear secretion |
|
VIII |
Vestibulocochlear |
Sensory |
Balance, posture, and hearing |
|
IX |
Glossopharyngeal |
Both |
Swallowing, taste, and saliva secretion |
|
X |
Vagus |
Both |
Taste, visceral sensation |
|
XI |
Accessory |
Motor |
Movement of the head and shoulders |
|
XII |
Hypoglossal |
Motor |
Movement of the tongue |
Procedure
Physical examination of the cranial nerves during a medical assessment is common when examining the eyes, ears, nose, throat, neck, and head. The following lab will allow you to test the function of each of your cranial nerves.