Organization of the Organization of the Nervous SystemNervous System

BT520: Principles of Neuroscience

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

Sym: redParasym: blue

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