Questions for research:
1. Organs in the major divisions of the nervous system….
2. Functions of the nervous system….
a. Neurons and synapses
Most neurons send signals via their axons, although some types are capable of dendrite-to-dendrite communication. (In fact, the types of neurons called amacrine cells have no axons, and communicate only via their dendrites.) Neural signals propagate along an axon in the form of electrochemical waves called action potentials, which produce cell-to-cell signals at points where axon terminals make synaptic contact with other cells. b. Neural circuits and systems
The basic neuronal function of sending signals to other cells includes a capability for neurons to exchange signals with each other. Networks formed by interconnected groups of neurons are capable of a wide variety of functions, including feature detection, pattern generation, and timing. c. Reflexes and other stimulus-response circuits
The simplest type of neural circuit is a reflex arc, which begins with a sensory input and ends with a motor output, passing through a sequence of neurons in between. For example, consider the "withdrawal reflex" causing the hand to jerk back after a hot stove is touched. The circuit begins with sensory receptors in the skin that are activated by harmful levels of heat: a special type of molecular structure embedded in the membrane causes heat to change the electrical field across the membrane. If the change in electrical potential is large enough, it evokes an action potential, which is transmitted along the axon of the receptor cell, into the spinal cord. There the axon makes excitatory synaptic contacts with other cells, some of which project (send axonal output) to the same region of the spinal cord, others projecting into the brain. 3. Cranial and spinal nerves…
Cranial nerve| Origin| Innervation|
Olfactory| Telencephalon| Transmits the sense of smell from the nasal cavity. Located in olfactory foramina in thecribriform plate of ethmoid.| Optic| Diencephalon| Transmits visual signals from the retina of the eye to the brain. Located in the optic canal.| Oculomotor| Anterior aspect of Midbrain| Innervates the levator palpebrae superioris, superior rectus, medial rectus, inferior rectus, andinferior oblique, which collectively perform most eye movements. Also innervates the sphincter pupillae and the muscles of the ciliary body. Located in the superior orbital fissure.| Trochlear| Dorsal aspect of Midbrain| Innervates the superior oblique muscle, which depresses, rotates laterally, and intorts the eyeball. Located in the superior orbital fissure.| Trigeminal| Pons| Receives sensation from the face and innervates the muscles of mastication. Located in thesuperior orbital fissure (ophthalmic nerve - V1), foramen rotundum (maxillary nerve - V2), andforamen ovale (mandibular nerve - V3).| Abducens| Nuclei lying under the floor of the fourth ventricle Pons| Innervates the lateral rectus, which abducts the eye. Located in the superior orbital fissure.| Facial| Pons(cerebellopontine angle) above olive| Provides motor innervation to the muscles of facial expression, posterior belly of the digastric muscle, and stapedius muscle. Also receives the special sense of taste from the anterior 2/3 of the tongue and provides secretomotor innervation to the salivary glands (except parotid) and thelacrimal gland. Located in and runs through the internal acoustic canal to the facial canal and exits at the stylomastoid foramen.| Acoustic or Vestibulocochlear(or auditory-vestibular nerveor acoustic nerve| Lateral to CN VII (cerebellopontine angle)| Senses sound, rotation, and gravity (essential for balance and movement). More specifically, the vestibular branch carries impulses for equilibrium and the cochlear branch carries impulses for hearing. Located in the internal acoustic canal.| Glossopharyngeal| Medulla|...