Cranial Nerves
Cranial nerves are a set of 12 pairs of nerves that emerge directly from the brain and brainstem. They are responsible for controlling various functions such as sensation, movement, and autonomic activities in the head and neck. Each cranial nerve has specific functions and innervates specific areas, playing a crucial role in the overall functioning of the nervous system.
8 Key excerpts on "Cranial Nerves"
eBook - ePubFunctional and Clinical Neuroanatomy
A Guide for Health Care Professionals
- Jahangir Moini, Pirouz Piran(Authors)
- 2020(Publication Date)
- Academic Press(Publisher)
...When the full name of each cranial nerve is used, then just its Roman numeral is required, such as olfactory nerve (I). Every cranial nerve is attached to the brain adjacent to its associated nuclei, whether sensory, motor, or both. For the sensory nuclei, postsynaptic neurons relay information to other nuclei, or to centers in the cerebral cortex or cerebellar cortex, for processing. Motor nuclei information is similarly processed, as they receive input from higher brain centers, or from various nuclei found along the brainstem. The Cranial Nerves are classified as follows: • Mostly sensory —carrying somatic sensory information (pressure, touch, temperature, vibration, pain) or special sensory, such as sight, hearing, balance, and smell • Motor —dominated by axons of somatic motor neurons • Mixed (sensory and motor) —a mixture of sensory and motor fibers Cranial Nerves have not only these primary functions but also secondary functions. Cranial Nerves III, VII, IX, and X also contribute to the parasympathetic autonomic system. The 12 pairs of Cranial Nerves connect to the under portion of the brain, primarily on the brainstem (see Fig. 10.1). They pass through small holes called foramina in the cranial cavity within the skull. This allows them to extend between the brain and their peripheral connections. It is important to note that the sensory fibers of the Cranial Nerves are termed proprioceptive. Fig...
eBook - ePub- Min Suk Chung, Beom Sun Chung(Authors)
- 2020(Publication Date)
- Academic Press(Publisher)
...Chapter 3 The cranial nerve, the spinal nerve The Cranial Nerves consists of 12 pairs of nerves, most of which emerge from the brainstem. In terms of function, the cranial nerve contains somatic sensory nerve, somatic motor nerve, visceral sensory nerve, and visceral motor nerve. Correspondingly, each cranial nerve contains the nucleus (or nuclei) in the central nervous system, and may contain the ganglion (or ganglia) in the peripheral nervous system. The functions and locations of the nuclei and ganglia are discussed in detail. Readers can be familiarized with the nuclei with assistance from the stained slices of the brainstem. In succession, the spinal nerves (cervical, thoracic, lumbar, and sacral nerves) from the spinal cord are studied, with respect to the components of the spinal nerves (somatic sensory nerve and somatic motor nerve). For full understanding of the cranial and spinal nerves, regional anatomy knowledge is necessary. Keywords Cranial nerve; brainstem; spinal nerve; spinal cord; nucleus; ganglion The cranial nerve Cranial nerve I The first two Cranial Nerves, CN I and II, are often regarded as the extended parts of the brain. Technically speaking, CN I and II are the extensions of cerebrum and thalamus, respectively (Fig. 1.61). CN I and II belong to the central nervous system, because the two nerves are enclosed by the pia mater which covers the central nervous system (Fig. 1.7). This explains why CN I and II have no sensory ganglion, a structure of the peripheral nervous system (Fig. 2.6) (Table 2). CN I is discussed briefly in this neuroanatomy book, since it is rather close to the neurophysiology field. Fig. 3.1 Olfactory pathway. The 1st neuron of CN I originates from receptor of the olfactory mucosa in the upper nasal cavity. The 1st neuron [short bipolar neuron (Fig. 2.5)] synapses with the 2nd neuron in the olfactory bulb. The 2nd neuron runs through the olfactory tract. The olfactory bulb and tract are beneath the frontal lobe (Fig...
eBook - ePub- Ruth Hull(Author)
- 2021(Publication Date)
- Lotus Publishing(Publisher)
...There are 12 pairs of them, 10 which originate from the brain stem and 2 which originate inside the brain. They are named according to their distribution or function and numbered according to where they arise in the brain (in order from anterior to posterior). Most of the Cranial Nerves contain both motor and sensory fibres and so are mixed nerves. Only three are purely sensory: the olfactory, optic and vestibulocochlear nerves. Figure 6.14 An overview of the brain and Cranial Nerves Cranial Nerves Number Name Function I Olfactory Smell II Optic Vision III Oculomotor Motor function: Movement of eyelid and eyeball; control of lens shape and pupil size Sensory function: Proprioception in eyeball muscles IV Trochlear Motor function: Movement of eyeball Sensory function : Proprioception in superior oblique muscle of the eyeball V Trigeminal – has three branches: the ophthalmic, maxillary and mandibular branches Motor function: Chewing Sensory function: Sensations of touch, pain and temperature from the skin of the face and the mucosa of the nose and mouth, and sensations supplied by proprioceptors in the muscles of mastication VI Abducens Motor function: Movement of eyeball Sensory function: Proprioception in lateral rectus muscle of the eyeball VII Facial – has five branches: the temporal, zygomatic, buccal, mandibular and cervical branches Motor function: Facial expression; secretion of...
eBook - ePub- J. L. Wilkinson(Author)
- 2014(Publication Date)
- Butterworth-Heinemann(Publisher)
...Chapter 6 Cranial Nerves Publisher Summary The Cranial Nerves are numbered in rostrocaudal order. These are classified into three main morphological groups. The first group comprises of those supplying muscles derived from cranial myotomes, namely, the oculomotor (III), trochlear (IV), abducent (VI) that supply the eye muscles, and the hypoglossal (XII) supplying the tongue. The second group comprises of those innervating muscles of branchial arch origin, namely, the trigeminal (V), facial (VII), glossopharyngeal (IX), vagus (X), and accessory (XI). The third group comprises of those serving special senses, namely, the olfactory (I), optic (II), and vestibulocochlear (VIII). This chapter discusses the components of cranial nerve and its functions. Spinal nerves have four components—somatic afferent, visceral afferent, visceral efferent, and somatic efferent. The chapter discusses the distribution of the glossopharyngeal nerve. The tympanic nerve carries sensory fibers from the tympanic plexus of middle ear, from mastoid air cells, and pharyngotympanic tube...
eBook - ePub- Hugh Wagner, Kevin Silber(Authors)
- 2004(Publication Date)
- Taylor & Francis(Publisher)
...On the sensory side, there is a little more variety, with some serving the major senses. The 10th cranial nerve is called the vagus nerve and serves the internal organs rather than the head. This nerve, together with the 3rd, 7th and 9th Cranial Nerves, is part of the parasympathetic nervous system (see Topic D2). Table 1. Functions of the 12 Cranial Nerves Nerve pair Sensory Motor I Olfactory Smell II Optic Vision III Occulomotor Eye movements IV Trochlear Eye movements V Trigeminal Sensation of mouth and face Mastication VI Abducens Eye movements VII Facial Facial movement VIII Auditory Audition and balance IX Glossopharyngeal Gustation Swallowing and vocalization X Vagus Internal organs Internal organs XI Spinal Accessory Neck movement XII Hypoglossal Tongue movement D2 T HE AUTONOMIC NERVOUS SYSTEM Key Notes The structure of the autonomic nervous system (ANS) The ANS serves those functions that are not under voluntary control. It has two branches. The sympathetic nervous system mainly activates systems. The parasympathetic nervous system mainly calms things down. At all preganglionic synapses of both systems the neurotransmitter is acetylcholine. At the target organ synapses the neurotransmitter substances in the sympathetic system is predominantly norepinephrine. In the parasympathetic system it is predominantly acetylcholine. The sympathetic branch of the ANS The sympathetic nervous system controls functions that activate the body, including the ‘fight-or-flight’ response. This includes causing epinephrine excretion, and diverting blood from digestive processes to muscles. The parasympathetic branch of the ANS The parasympathetic nervous system returns the body to its normal state once increased activities are over, and actively promotes the storage of energy. Its actions tend to be antagonistic to those of the sympathetic nervous system. The excesses of modern living The autonomic nervous system has evolved to cope with natural environmental events...
- Robert L. Maynard, Noel Downes(Authors)
- 2019(Publication Date)
- Academic Press(Publisher)
...Chapter 21 Peripheral Nervous System Chapter 21.1 Cranial Nerves Making Sense of the Cranial Nerves Various Cranial Nerves are mentioned in the other chapters of this book; in this chapter, we treat them as a group and try to discover some underlying principles that explain their complexity. The search for such principles has been underway since the late 19th century. Balfour, in 1885, demonstrated that the head of vertebrates was segmented in the same way as the rest of the body. Once this was established it seemed safe to assume that the Cranial Nerves should follow a pattern similar to that of the spinal nerves, with each cranial nerve associated with a particular segment. The segments were named from premandibular at the front of the skull, to the obvious occipital segments at the back. Thinking along these lines can be traced through the works of Goodrich (1930), De Beer (1951) and Young (1962), and represents an important aspect of classical comparative anatomy. This linking of Cranial Nerves with segments might be regarded as the first of four lines of attack on the problem of making sense of the Cranial Nerves, although recent work has shown that segmentation of the head is more complex than first thought. A second line of attack involves examination of the Cranial Nerves in terms of whether they represent dorsal or ventral roots of segmental nerves. Each spinal nerve has a dorsal and a ventral root which join just as the nerve leaves the vertebral column. The dorsal root is distinguished by the presence of a dorsal root ganglion where the cell bodies of the afferent neurones reside. These neurones carry sensory information from the periphery to the spinal cord...
eBook - ePub- Richard S. Snell, Michael A. Lemp(Authors)
- 2013(Publication Date)
- Wiley-Blackwell(Publisher)
...The olfactory and vestibulocochlear nerves are entirely sensory in function. The accessory and hypoglossal nerves are entirely motor in function. The facial, glossopharyngeal, and vagus nerves are both motor and sensory. Because these nerves are not directly associated with the eye and orbit, only a brief account of each nerve is given here. The different components of the Cranial Nerves, their functions, and the openings in the skull through which the nerves leave the cranial cavity are summarized in Table 10-2. The Sensory Nerves Olfactory Nerves (Cranial Nerve I) The olfactory nerves are responsible for conducting the sensations of smell from the upper part of the nasal mucous membrane to the olfactory bulbs in the skull. Origin and Course The olfactory nerves arise from the olfactory receptor nerve cells in the olfactory mucous membrane located in the upper part of the nasal cavity above the level of the superior concha (Fig. 11-1). The olfactory receptor cells are scattered among supporting cells. Each receptor cell consists of a small bipolar nerve cell with a coarse peripheral process that passes to the surface of the membrane and a fine central process. From the coarse peripheral process a number of short cilia, the olfactory hairs, arise and project into the mucus covering the surface of the mucous membrane. These projecting hairs react to odors in the air and stimulate the olfactory cells. The fine central processes form the olfactory nerve fibers (Fig. 11-1). Bundles of these nerve fibers pass through the openings of the cribriform plate of the ethmoid bone to enter the olfactory bulb inside the skull. Central Connections Olfactory Bulbs This ovoid structure lies in the anterior cranial fossa and possesses several types of nerve cells including the large mitral cell (Fig. 11-1). The incoming olfactory nerve fibers synapse with the mitral cells...
eBook - ePubThe Physiological Basis of Behaviour
Neural and Hormonal Processes
- Kevin Silber(Author)
- 2005(Publication Date)
- Routledge(Publisher)
...The spinal cord itself is not a single nerve but a collection of different nerves, each with its own function. For example, there are ascending, afferent, nerves which carry messages to the brain from peripheral receptors and descending, efferent, nerves which carry messages from the brain to muscles, glands, and so on. A good way to think about the spinal cord is as a multi-lane motorway carrying information up and down its length. We do not need to concern ourselves now with any greater detail concerning the spinal cord. However, as a final word on the subject, the spinal cord carries nerves for both the somatic and autonomic nervous systems and we will need to look more closely at the latter in Chapter 4. The brain It is tempting to think of our brain as something solid: in fact, it is anything but. Rose described the brain as ‘two fistfuls of pink-grey tissue, wrinkled like a walnut and something of the consistency of porridge…’ (1976:21). To keep this soft organ in place and protected, the brain is covered by a membrane called the dura mater and encased in a hard, bony skull. The human brain is a very complex organ. On its surface you can see a number of folds (Figure 3.2). These are called sulci and are there because our brains have outgrown our heads. The surface area of the brain is so large that it would not fit inside our heads unless it was folded up. In fact, two thirds of the surface of the brain lies within these sulci. We will start our analysis of the brain’s structure by looking at how it is divided up. These divisions are based partly on the brain’s evolutionary development and partly on the gross anatomical features (the large, easily-defined structures) that were visible with the naked eye to the pioneers of neuroanatomy...
