
C H A P T E R T H I R T E E N. THE NERVOUS SYSTEM: NEURAL TISSUE. Two organ systems coordinate and direct activities of body. Nervous system Swift, brief responses to stimuli Endocrine system Adjusts metabolic operations Directs long-term changes.
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THE NERVOUS SYSTEM: NEURAL TISSUE
projecting from the cell body
environment for generation of nerve impulses/action potentials
injured cells - may also kill healthy cells
http://www.horton.ednet.ns.ca/staff/selig/Activities/nervous/na1.htm
2. Cell processes = dendrites (little trees)
- the receiving or input portion of the neuron
-short, tapering and highly branched
-surfaces specialized for contact with other neurons
-cytoplasm contains Nissl bodies & mitochondria
http://bcs.whfreeman.com/thelifewire/content/chp44/4401s.swf
Excitabilityhttp://www.blackwellpublishing.com/matthews/channel.html
can be generated
depolarization (increase in MP) results from opening of Na+ channels. Once threshold is
reached, more Na+ channels open and a rapid
increase in MP results
outflow of K+ restores the MP. Na+ channels begin to open and K+ channels close. K+ outflow results in hyperpolarization (below resting)
results in a refractory period.
more slowly, depolarization also
opens K+ channels which permit
the outflow of K+ . The Na+ close
the MP becomes more negative
returning to resting
2. Amino acids: glutamate & aspartate & GABA
Valium is a GABA agonist - enhancing its inhibitory effect
3. Biogenic amines: modified amino acids
Other types:
Nitric oxide - formed on demand in the neuron then release (brief lifespan)
-role in memory and learning
-produces vasodilation - Viagara enhances the effect of NO
Divisions of the nervous system
position of joints
-provide information about internal environment
-most impulses are not perceived – those that are,
are interpreted as pain or pressure
vibration, proprioception, blood vessel stretch, hearing and equilibrium
and body fluids
-analgesia: relief from pain
-drugs: aspirin, ibuprofen – block formation of prostaglandins that
stimulate the nociceptors
-novocaine – block nerve impulses along pain nerves
-morphine, opium & derivatives (codeine) – pain is felt but not perceived in
brain (blocks morphine and opiate receptors in pain centers)
1. sensory - neurons that convey sensory information from somatic
receptors in the head, body wall, senses - to the CNS
2. control of motor output - neurons that conduct voluntary impulses to skeletal muscles
-contributions from the basal ganglia, cerebellum, brain stem and SC
3. one neuron pathway – somatic motor neurons synapse directly with the effector
4. neurotransmitter – usually acetylcholine
5. effectors – skeletal muscles
6. responses - contraction
Autonomic nervous system (ANS):
- motor output branch has two divisions:
1. sympathetic
2. parasympathetic
-most organs are innervated by
both divisions which have
opposing functions
e.g. sympathetic – increases heart rate
parasympathetic – decreases rate
-
http://www.wisc-online.com/objects/framz.asp?objID=OTA502
II - Optic
III - Oculomotor
IV-Trochlear
V - Trigeminal
VI - Abducens
VII - Facial
VIII - Acoustic
IX - Glossopharyngeal
X - Vagus
XI - Accessory
XII - Hypoglossal
http://www.wisc-online.com/objects/index.asp?objID=AP11504
of the sphenoid
-right and left join at the
optic chiasma (site of cross-over)
-continue to brain as optic tracts
The oculomotor nerve (III) [Motor]
lacrimal glands, side of nose, forehead
and scalp
of pharynx, upper teeth, upper
lip and lower eyelid
lower teeth, skin over mandible
and side of head anterior to ear
-motor – muscles of chewing
-inferior alveolar nerve (branch of mandibular)
-often anesthetized in dental procedures – lower jaw
-numbs to mental nerve (branch of the IAN)
-superior alveolar nerve (branch of the maxillary)
-numbs the upper jaw
the frontal, lacrimal and
nasociliary branches
paranasal sinuses
arise from the facial nerve
from the upper lip, medial portion of cheek
lower eyelid and side of nose
the maxilla
with the infraorbital blood vessels
alveolar nerve
periodonteum and their buccal gingiva
a. dental branches + interdental + interradicular
(dental plexus)
b. internal branches – exit from the posterior superior alveolar foramina (with the posterior superior alveolar arteries)
c. external – receive information from buccal gingiva and associated molars
and nasal septum
receive info from the nasal cavity
- union of several external branches
- sensory from the chin, lower lip and labial mucosa
- enters the skull at the mental foramen
- then merges with the lingual branch of the IAN
Lingual branch of the IAN
- made up of dental branches from anterior mandibular teeth, interdental
branches form the surrounding periodonteum = dental plexus
-sensory information for the anterior mandibular teeth
Mylohyoid branch of the IAN
- joins with the mental and lingual after it emerges from the mandibular
foramen
- pierces the sphenomandibular ligament
- runs in the mylohyoid groove then onto the mylohyoid muscle
- motor commands to this muscle + anterior belly of the diagastric
(posterior belly is innervated by the facial nerve)