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Organization of the Organization of the Nervous SystemNervous System
BT520: Principles of Neuroscience
Braitenberg’s “Vehicles”
You don’t need complex systems to show complex behavior
Simple systems in their interaction with a complex world can show complex behavior
… like Braintenberg’s Vehicles Braitenberg, V. (1984). Vehicles: Experiments in synthetic psychology.
Cambridge, MA: MIT Press.
Vehicle-I
Vehicle-2a: Express “dislike”
Runs away Charges towards
Vehicles – IIb: Express “liking”
“adoration”
“fancifulness”
Directions
On the same sideIpsilateralOn the opposite sideContralateral
On both sidesBilateralToward the middleMedialAway from the middleLateral
Toward the top of the head/body
Superior
Toward the tailCaudal
Toward the noseRostral
Toward the backDorsal
Toward the belly (front)VentralDescriptionDirection
Sections
Nodes and Edges
Nodes: nucleus, gray matter, cortex, ganglia
Edges/Wire: tracts, peduncles, fasciculi, commisure, nerves
Organizational Chart
Developing Brain
Embryonic stages of the brain
telencephalon Mesencephalon
Metencephalon Myelencephalon
Diencephalon
Peripheral Nervous System
somatic: sensory: innervate skin, muscles & joints, and provide
info about muscle and limb position etc. motor: skeletal muscle
autonomic: sympathetic: participates in response of the body to
stress, reaction to an emergency situation – “fight and flight”
parasympathetic: conserve body resources, maintenance of homeostasis – “rest and digest”
Enteric system: controls smooth muscle of the gut.
Somatic Nervous System Nerves
12 cranial nerves 33 spinal nerves
Nerves Nerve is a bundle of fibers (axons) Sensory, motor, pain, or mixed Labeled line hypothesis
Cranial Nerves
Cranial Nerves
Olfactory Nerve: Smell Optic Nerve: Vision Oculomotor Nerve: eye movement, pupil dilation Trochlear Nerve: eye movement
Controls superior oblique muscle Trigeminal Nerve: Somatosensory information (touch, pain)
from the face and head; muscles for chewing. Abducens Nerve: Eye movement
Controls lateral rectus muscle
Eye Muscles
Trigeminal Neuralgia TN (Trigeminal Neuralgia / tic douloureux) is a disorder of the
fifth cranial (trigeminal) nerve Causes episodes of intense, stabbing, electric shock-like pain in
the areas of the face where the branches of the nerve are distributed - lips, eyes, nose, scalp, forehead, upper jaw, and lower jaw.
It's called the "suicide disease". Something as simple and routine as brushing the teeth, putting
on makeup or even a slight breeze can trigger an attack, resulting in sheer agony for the individual.
Trigeminal neuralgia (TN) is not fatal, but it is universally considered to be the most painful affliction known to medical practice.
Cranial Nerves
Facial Nerve: Taste (anterior 2/3 of tongue); somatosensory information from ear; controls muscles used in facial expression.
Vestibulocochlear Nerve: Hearing; balance Glossopharyngeal Nerve: Taste (posterior 1/3 of tongue);
Somatosensory information from tongue, tonsil, pharynx; controls some muscles used in swallowing.
Vagus Nerve: Sensory, motor and autonomic functions of viscera (glands, digestion, heart rate)
Spinal Accessory Nerve: Controls muscles used in head movement
Hypoglossal Nerve: Controls muscles of tongue
Types of Nerve Fibers
Type A: large myelinated fast fibers of SC (120m/s) Type A (skeletal muscle), Type A (muscle spindle)
Type B: small myelinated fast fibers (3-15 m/s) Preganglionic fibers of ANS
Type C: small unmyelinated slow fibers (0.5 m/s) Autonomous fibers to visceral targets
Myelin Sheath
Glands
Exocrine glands: have ducts Salivary glands, lachrymal glands etc
Endocrine glands: no ducts; release hormones into blood stream Pituitary gland, thyroid gland, pancreas etc
Sympathetic Nervous System
Paravertebral sympathetic chains Two prevertebral symp chains
Celiac and hypogastric ganglia Nerves extending from various ganglia to
internal organs
Sympathetic Nervous System
Parasympathetic Nervous System
Preganglionic and Postganglionic parasym neurons Preganglionic fibers pass uninterrupted to the organ that
has to be controlled In the wall of the organ are located the postganglionic
neurons
Vagus Nerve
About 75% of all parasym fibres are in vagus nerve (X cranial nerve)
Vagal nerve stimulation (VNS) For treating arrhythmias For epilepsy For depression Exact method
of therapeutic action is unknown
Autonomic reflexes
Cardiovascular autonomic reflexes High pressure in large arteries activates baroreceptors; feedback
from baroreceptors reaches brain stem activates parasym and inhibits symp.
Gastrointestinal reflexes Ex: smell/presence of appetizing food nose and mouth
vagal, glossopharyngeal and salivary nuclei of brain stem activates secretory glands of mouth and stomach
Sympathetic has mass discharge Alarm or stress response Inc. arterial pressure Inc. blood flow to active muscles Inc. rates of cellular metabolism throughout
the body Inc. blood glucose Inc. muscle strength
Parasym produces localized responses Examples:
Parasym cardiovascular reflexes Can act only on the heart
Can control secretion of mouth glands or of stomach glands
Spinal cord and sympathetic nerves
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