Title: Brain
1Brain Cranial Nerves
2Major Parts of the Brain
- Brain stem continuous with the spinal cord.
- Medulla oblongata.
- Pons.
- Midbrain.
- Cerebellum posterior to the brain stem.
3Major Parts of the Brain
- Diencephalon superior to the brain stem.
- Thalamus.
- Hypothalamus.
- Cerebrum supported on the diencephalon and
brain stem. - Largest part of the brain.
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5Brain Blood Supply
- Arteries
- Internal carotid arteries
- Vertebral arteries
- Veins
- Internal jugular veins
6Brain Blood Flow
- The brain consumes about 20 of the oxygen and
glucose used at rest. - A brief slowing of blood flow may cause
unconsciousness.
7Brain Blood Flow
- An interruption of blood flow for 1 to 2 minutes
impairs neural function. - Total deprivation of oxygen for 4 minutes causes
permanent injury. - If the blood entering the brain has a low level
of glucose, mental confusion, dizziness,
convulsions, and loss of consciousness may occur.
8Blood Brain Barrier
- The blood-brain barrier (BBB) protects the brain
from harmful substances and pathogens. - It prevents the passage of many substances from
the blood to the brain tissue. - Tight junctions seal together endothelial cells
of brain capillaries. - Astrocytes selectively allow some substances
through and not others.
9Breaching the BBB
- The BBB prevents the passage of harmful
substances into the brain, but it also prevents
the passage of useful drugs. - Drugs are injected in a concentrated sugar
solution to facilitate passage. - The high osmotic pressure causes cells lining the
barrier to shrink and makes the membrane leaky.
10Protective Coverings
- Cranial Meninges.
- Dura mater.
- Arachnoid mater.
- Pia mater.
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12Cerebrospinal Fluid (CSF)
- Clear colorless liquid.
- Protects the brain and spinal cord from chemical
and physical injuries. - Carries oxygen, glucose, and other needed
chemicals from the blood to the neurons and
neuroglia. - Circulates in the subarachnoid space (between the
arachnoid mater and pia mater).
13Protective Coverings
- Extensions of the dura mater separate the parts
of the brain. - Falx cerebri separates the two hemispheres of
the cerebrum. - Falx cerebelli separates the two hemispheres of
the cerebellum. - Tentorium cerebelli separates the cerebrum from
the cerebellum.
14Formation of CSF in the Ventricles
- CSF is formed in the ventricles.
- Formed by ependymal cells that cover the choroid
plexuses of the ventricles.
15Formation of CSF in the Ventricles
- There are 4 ventricles.
- Functions of CSF.
- Mechanical protection.
- Shock absorption.
- Buoys the brain.
- Chemical protection optimal chemical
environment. - Circulation medium of exchange for wastes and
nutrients.
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20Hydrocephalus
- Abnormalities of the brain can interfere with
drainage of CSF from the ventricles and
subarachnoid space. - CSF pressure increases causing hydrocephalus.
- In infants this causes the fontanels to budge.
21Hydrocephalus
- Tumors, inflammation, developmental malformations
can all cause hydrocephalus. - Pressure buildup can damage the delicate nervous
tissue. - A surgeon can implant a drain line called a shunt
to divert CSF. - In adults, hydrocephalus may occur after head
injury, meningitis, or subarachnoid hemorrhage.
22Brain Stem
- Between the brain and spinal cord.
- 3 regions.
- Medulla oblongata.
- Pons.
- Midbrain.
23Medulla Oblongata
- A continuation of the spinal cord.
- Sensory (ascending) tracts and motor (descending)
tracts travel through the white matter of the
medulla. - Many nerves decussate (cross over) in the medulla.
24Medulla Oblongata
- Cardiovascular center regulates the heartbeat and
the diameter of the blood vessels.
25Medulla Oblongata
- The medullary rhythmicity area adjusts the rhythm
of the breathing and controls reflexes for
vomiting, coughing, and sneezing.
26Medulla Oblongata
- The nuclei for the following cranial nerves
reside in the medulla - VIII (vestibulocochlear).
- IX (glossopharyngeal).
- X (vagus).
- XI (accessory).
- XII (hypoglossal).
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29Pons
- Pneumotaxic area and apneustic area regulate
breathing. - Nuclei for cranial nerves V (trigeminal), VI
(abducens), VII (facial), and VIII
(vestibulocochlear).
30Midbrain
- The midbrain or mesencephalon contains the
superior colliculi (visual actvities) and
inferior colliculi (auditory pathways). - The midbrain contains the substantia nigra which
release dopamine to help control subconscious
muscle activities. Loss of these neurons results
in Parkinson disease. - Cranial nerves III (oculomotor) and IV
(trochlear) originate here.
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32Cerebellum
- The second largest part of the brain.
- A main function of the cerebellum is to evaluate
how well movements are being carried out and
correct for discrepancies. This helps to smooth
out movements.
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34Diencephelon
- Epithalamus.
- Contains the pineal gland which secretes
melatonin. - Thalamus.
- Relays sensory information to the cortex.
- Provides crude perception of touch, pressure,
pain, and temperature.
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36Diencephelon
- Subthalamus.
- Controls body movements.
- Hypothalamus.
- Controls and integrates activities of the ANS.
- Regulates emotional and behavioral patterns.
- Regulates cicadian rhythms.
- Regulates eating and drinking behavior.
- Produces hormones oxytocin and ADH.
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38Cerebrum
- Sensory areas interpret sensory impulses.
- Motor areas control muscular movement.
- Association areas function in emotional and
intellectual processes. - Basal areas regulate gross muscle movements and
regulate muscle tone. - Limbic system functions in survival behaviors.
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42Brain Injuries
- Concussion an abrupt, temporary loss of
consciousness following a blow to the head. - Most common brain injury.
- Signs headache, drowsiness, lack of
concentration, confusion, amnesia.
43Brain Injuries
- Contusion bruising of the brain due to trauma
and includes leakage of blood. - Signs - immediate loss of consciousness,
transient cessation of respiration, decreased
blood pressure.
44Brain Injuries
- Laceration tear of the brain usually from a
skull fracture or gunshot wound. - Rupture of large blood vessels.
- Consequences cerebral hematoma (localized pool
of blood, usually clotted), edema, and increased
intracranial pressure.
45Cerebral Cortex Areas and Functions
- Sensory areas receive and interpret sensory
information.
46Cerebral Cortex Areas and Functions
- Motor areas initiate movements.
- Association areas deal with integrative
functions - Memory.
- Emotions.
- Reasoning.
- Will.
- Judgement.
- Personality.
- Intelligence.
47Sensory Areas
- Primary somatosensory area receives sensations
for touch, proprioception, pain, itching, tickle,
and thermal sensations. - Located in the postcentral gyrus of the parietal
lobes. - Primary visual area.
- Primary auditory area.
- Primary gustatory area taste.
- Primary olfactory area.
48Motor Areas
- Primary motor area located in the precentral
gyrus of the frontal lobe. - Brocas speech area coordinates the
contractions of speech and breathing muscles.
49Association Areas
- Somatosensory association area integrates and
interprets sensations. - Visual association area evaluates what is seen.
- Auditory association area evaluates sounds.
50Association Areas
- Wernickes (posterior language) area interprets
the meaning of speech. - Common integrative area.
- Premotor area controls learned skilled
movements. - Frontal eye field area controls voluntary
scanning movements of the eyes.
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52Aphasia
- An inability to use or comprehend words.
53Aphasia
- Damage to Brocas area results in nonfluent
aphasia. - Inability to properly articulate to form words.
- These people know what they wish to say, but
cannot speak.
54Aphasia
- Damage to the auditory association area results
in fluent aphasia. - Faulty understanding of spoken words.
- Word deafness inability to understand spoken
words. - Word blindness inability to understand written
words.
55Cranial Nerve I - Olfactory
- Type sensory.
- Function smell.
- Anosmia loss of sense of smell.
56Cranial Nerve II Optic Nerve
- Type sensory.
- Function vision.
- Anopia blindness in one or both eyes.
57Cranial Nerve III - Oculomotor
- Type mixed (mainly motor).
- Function movement of the upper eyelid and
eyeball. Accomodation of the lens for nearn
vision and constriction of the pupil. - Strabismus deviation of the eye in which both
eyes dont focus on the same object. - Ptosis drooping of the upper eyelid.
- Diploia double vision.
58Cranial Nerve IV Trochlear Nerve
- Type mixed (mainly motor).
- Function movement of the eyeball.
- Diplopia and strabismus occur with trochlear
nerve damage.
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60Cranial Nerve V Trigeminal Nerve
- Type mixed.
- Function conveys impulses for touch, pain,
temperature and proprioception. Chewing. - Trigeminal neuralgia (tic douloureux) pain to
branches of the trigeminal nerve. - Dentists apply anesthetic to branches of this
nerve.
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62Cranial Nerve VI - Abducens
- Type mixed (mainly motor).
- Function movement of the eyeball.
- With damage to this nerve the eye cannot move
laterally beyond the midpoint and usually points
medially.
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64Cranial Nerve VII Facial Nerve
- Type mixed.
- Function Propriception and taste. Facial
expression. Secretion of saliva and tears. - Injury produces bells palsy (paralysis of facial
muscles).
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66Cranial Nerve VIII Vestibulocochlear Nerve
- Type mixed (mainly sensory).
- Function conveys impulses for equilibrium and
hearing. - Injury can cause vertigo, ataxia (muscular
incoordination), nystagmus (rapid movement of the
eyeball), and tinnitus.
67Cranial Nerve IX Glossopharyngeal Nerve
- Type mixed.
- Function taste and somatic sensations from the
posterior 1/3 of the tongue. Elevates the
pharynx during swallowing and speech. Stimulates
the secretion of saliva. - Injury causes decreased salivary secretion, loss
of taste, and difficulty swallowing.
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69Cranial Nerve X Vagus Nerve
- Type mixed.
- Function taste and somatic sensations.
Swallowing, coughing, and voice production.
Regulates GI tract and heart rate. - Injury interferes with swallowing, paralyzes
vocal cords, and causes the heart rate to
increase.
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71Cranial Nerve XI Accessory Nerve
- Type mixed (mainly motor).
- Function Proprioception. Swallowing, movement
of head and shoulders. - If the nerves are damaged the SCM and Trapezius
become paralyzed.
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73Cranial Nerve XII Hypoglossal Nerve
- Type mixed (mainly motor).
- Function Proprioception. Movement of the tongue
during speech and swallowing. - Injury results in difficulty in chewing,
speaking, and swallowing. When protruded, the
tongue curls towards the affected side and
atrophies on the affected side.
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75Cranial Nerves
- On Old Olympus Towering Tops A Fin And German
Viewed Some Hops. - This mnemonic device helps you memorize the names
of the cranial nerves. - The first letter from each word corresponds to
the first letter of each cranial nerve.