Anatomy - Outcome 12 Flashcards
The Nervous System
-relays messages from distant parts of the body , which lets the brain know exactly what is happening in each part
- the brain coordinates and sends out messages that cause muscles to contract stimulating glands to secrete, regulate numerous functions, and in fact, perform many of these tasks without true consciousness on our part
- in order to accomplish this, the nervous system has to hvae tremendous organization and potential
The 2 major components of the nervous system are..
-the central nervous system (CNS)
- the peripheral nervous system (PNS)
The Central Nervous System (CNS)
consists of the braine and the spinal cord
The Peripheral Nervous System (PNS)
-composed of all the nerves that extend out from the brain or spinal cord
-made up of the spinal nerves, cranial nerves, and autonomic nervous system
- the 31 pairs of spinal nerves extend from the spinal cord to distant parts of the body
- general have both motor and sensory neurons in them
- these nerves are distributed by pregion from the neck to the toes
- several of the cervical (neck) nerves innervate some of the hyoid muscles that depress the mandible and raise the larynx
- the 12 pairs of cranial nerves attach directly to the brain. (use roman numerals)
Sensory & Motor Neurons
A neuron (nerve cell) or group of neurons transmits a message (or impulse) in one direction only; therefore, it is neceessary to have both sensory & motor neurons
When you see a drawing of a nerve, it represents a bundle of nerons, some sensory and some motor - these are what enable an nerve to carry messages to and from the brain
The Reflex Arc
Conscious sensory-motor reaction is an involved system, so the nervous system has a built in short cut known as reflex arch
-this shortcut takes place in the spinal cord. This neuron has a shorter neuron that runs between it and the motor nerve leaving the spinal cord
- the action is accomplished without the person thinking about it. The message travels into the spinal cord and out again without going to the brain.
- the spinal cord and the brain are centers of the nervous activity but they cannot perform alone. They need the help of the PNS
The functional divisions of the Nervous System
-Functionally, the nervous system is divided according to whether the control is voluntary or involuntary, and according to which type of tissue is stimulated
The 2 functional divisions of the nervous system are:
- the somatic nervous system
-the autonomic nervous system
The somatic nervous system
- this system is controlled voluntarily and all its effects are on skeletal muscles
The autonomic nervous system
- is the involuntary division and controls automatic activity
- it controls smooth muscles, cardiac muscles, and gland
The autonomic system is composed of 2 parts:
-the sympathetic system - is expendable taking effect during emergencies. Has both motor and sensory fibers and is not willfully controlled. The motor fibers supply smooth and cardiac muscle glands. The sensory fibers carry sensations from the various organs of the body
- the parasympathetic system - neceesary to live and facilitates our minute-to-minute functions
The Trigeminal Nerve (Cranial Nerve V)
- the primary source of innervation to the oral cavity is the trigeminal nerve
The trigeminal nerve has 3 divisions:
- opthalmic division (V1)
-maxillary division (V2)
-mandibular division (V3)
The three divisions funcion to innervate the skin of the anterior face and head region
Opthalmic Division (V1)
- the smallest of the three divisions.
- provides sensation to the skin above the eye and up into the forehead
Maxillary Division (V2)
-passes through the base of the skull through the foramen in the sphenoid bone and lies in a depression in the bone behind and below the ey
- provides sensation to the upper teeth and oral cavity, mucous membrane, periosteum, nasal cavity, and temporal region
The maxillary division (V2) splits into the 4 terminal branches:
- Posterior Superior Alveolar Nerve (PSA)
- Middle Superior Alveolar Nerve (MSA) / Anterior Superior Alveolar Nerve (ASA)
- Greater Palatine (GP)
- Nasopalatine (NP)
Posterior Superior Alveolar Nerve (PSA)
-leaves the sphenoid bone and travels along the posterior part of the maxillary tuberosity
-supplies the buccal gingiva of the molars
- enters the bone to supply the maxillary second and third molars and the distobuccal and lingual roots of the maxillary first molar
- also supplies part of the maxillary sinus
Middle Superior Alveolar Nerve (MSA) / Anterior Superior Alveolar Nerve (ASA)
- are the two branches of the maxillary division within the infraorbital canal (directly below the eye socket)
- supply the skin of the nose, lower eyelide, skin and mucosa of the upper lip and maxillary labial gingiva
- MSA nerve lies in the wall of the sinus to supply the maxillary bicuspids and the mesiobuccal root of the maxillary first molar - also supplies part of the maxillary sinus and the adjacent gingiva
- the ASA nerve extends downward anterior to the wall of the sinus to supply the maxillary anterior teeth (incisors/cuspids) and associated labial gingiva - important to note that some of these nerves provide sensations to the soft tissue while some innervate the teeth themselves
Greater Palatine (GP) Nerve
- one of two branches with the other being the lesser palatine nerve (which relates to the soft palate)
- supplies most of the mucosa of the hard palate
Nasopalatine (NP) Nerve
- is the nerve at the anterior portion of the palate
- supplies the lingual gingiva adjacent to the maxillary central and lateral incisors
Mandibular Division (V3)
-passes through the skull through the foramen ovale (sphenoid bone) and travels downward where it breaks up into a number of branches:
-five motor nerves for the muscles of mastication (temporal, masseter pterygoids)
- the auriculotemporal nerve which supplies the area above and in front of the ear
-buccal nerve
-lingual nerve
-inferior alveolar nerve (IAN)
Buccal Nerve
-spreads out on the surface of the buccinator muscle and dthen penetrates the muscle
-lowest of its branches is called the long buccal nerve and lies in the posterior portion of the mandibular mcobuccal fold where it supplies the mandibular buccal gingiva up to the mental foramen
- remainder of the buccal nerve supplies the skin and mucosa of the cheeck and most of the maxillary buccal gingiva
Lingual Nerve
-is one of the longest branches of the mandibular division
- supplies sensation to the floor of the mouth, mandibular lingual gingiva, and the anterior two-thirds of the tongue
Inferior Alveolar Nerve (IAN)
-primarily serves the lower teeth although it does have a small motor branch, the mylohyoid nerve that supplies the mylohyoid muscle and the anterior belly of the digastric muscle
- runs parallel with the lingual nerve, then enters the mandible through the mandibular foramen and continues in the mandibular canal which ones obliquely downward and forward in the ramus, then horizontally forward in the body
- within the mandibular canal, the IAN gives off branches to the mandibular molars and bicuspids
- at the mental foramen, it divides into the mental nerve which supplies the skin of the lower lip and chin
- in the second branch, the incisive nerve supplies the mandibular anterior teeth and labial gingiva
PSA Innervates..
Mucosa: Buccal Gingiva - maxillary molars
Teeth: Mx 3rd & 2nd molars, DB, and lingual root of mx. first molar
MSA Innervates..
Mucosa: Buccal Gingiva, bicuspids
Teeth: Mx. bicuspids, MB root of the first mx. molar
Nasopalatine Innervates..
Mucosa: Lingual Gingiva/ Mx. Incisors
ASA Innervates..
Mucosa: Labial Gingiva/ mx. anteriors
Teeth: Mx. anteriors
Greater Palatine Innervates..
Mucosa: Hard Palate (except Lingual Mx incisors)
Lesser Palatine innervates..
Mucosa: Soft Palate
Inferior Alveolar Innervates..
Teeth: Molars, Bicuspids
Mental Nerve Innervates..
Mucosa: Mucosa and skin of lower lip and chin
Buccal Nerve Innervates..
Mucosa: Buccinator muscle. Buccal gingiva of mandibular molars and bicuspids. Skin and mucosa of the cheek
Incisive Nerve Innervates..
Teeth: Incisors
Lingual Nerve Innervates..
Mucosa: Anterior 2/3 of the tongue, lingual mucosa
Facial Nerve (Cranial Nerve VII)
-majority of the facial nerve leaves the brain through the stylomastoid foramen behind the ear
-comes forward and enters the parotid gland where it separates into a number of branches to provide motor supply to the muscles of facial expression
- also includes the special sensory fibers for taste which relate to the anterior 2/3rds of the tongue
- also has a salivary function as well
Infiltration Anesthesia
-technique most frequently used to anesthetize the maxillary teeth
- achieved by depositing the material directly under the tissue at the height of the mucobuccal fold and near the alveolus at the site of the dental procedure
-is possible in the maxilla because the porous nature of the cancellous bone allowing the solution to diffuse through the bone and reach the apices of the teeth
- can also be used as a secondary injection to anesthetize gingival tissues surrounding the mandibular teeth
Block Anaesthesia
-because the extremely dense, compact bone of the mandible does not permit diffusion of the anesthetic solution, infiltration anesthesia is not generally possible
- commonly required for most mandibular teeth
- solution is deposited near the nerve, and the entire area served by that nerve is anesthetized
- an Inverior Alveolar Nerve Block commonly called “mandibular block” anesthetized half of the lower jaw, including teeth, tongue, and lip
- if anesthesia is required for the mandibular anterior teeth or bicuspids only, the solution may be deposited at the mental foramen
