The Brain and Cranial Nerves

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The Brain and Cranial Nerves

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Major Parts of the Brain

• Brain stem continuous with spinal cord
• Midbrain
• Pons
• Medulla Oblongota

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Major Parts of the Brain

• Cerebellum Posterior to brain stem

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Major Parts of the Brain

• 3. Diencephalon superior to the brain stem
• Thalamus
• Epithalamus
• Hypothalamus
• Subthalamus

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Major Parts of the Brain

• 4. Cerebrum largest part of the brain
  supported by the diencephalon and brain stem

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Brain Stem

• Medulla Oblongata
• Continuous with spinal cord
• Contains both motor and sensory tracts

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Brain Stem / Medulla

• Contains portrusions of white matter called
  called pyramids

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Brain Stem / Medulla

• The crossing of pyramids result in neurons in
  the left cerebral cortex controlling skeletal
  muscles on the right side of the body and neurons
  in the right cerebral cortex controlling skeletal
  muscles on the left side

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Brain Stem / Medulla

• There are reflex centers for regulation of
  heart rate, respiratory rate, vasoconstriction,
  swallowing, vomiting

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Brain Stem / Pons

• Superior to the medulla
• Helps control breathing
• It relays nerve impulses related to voluntary
  skeletal movements from the cerebral cortex to
  the cerebellum

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Brain Stem / Midbrain

• Extends from the pons to the diencephalon
• Cerebral Peduncles, superior colliculi, and
  inferior colliculi located here

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Brain Stem / Midbrain

• Cerebral Peduncles contain major motor tracts

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Brain Stem / Midbrain

• Superior colliculi help with reflex head
  turning in response to visual stimuli
• Responsible for the pupillary reflex and
  accomodation reflex (adjusts shape of lens for
  far versus close vision)

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Brain Stem / Midbrain

• Inferior coliculi helps with reflex head
  turning in response to auditory stimuli
• Reflex center for startle reflex

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Cerebellum

• Vermis - central constricted area
• Cerebellar hemispheres lateral lobes

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Cerebellum

• Cerebellar cortex superficial layer of the
  cerebellum made up of gray matter

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Cerebellum

• Arbor Vitae Deep to the gray mater made up of
  tracts (White Matter)

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Cerebellum

• Main function Regulates posture and balance

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Diencephalon / Thalamus

• A pair of oval masses of grey matter, organized
  into nuclei, with interspersed tracts of white
  matter

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Diencephalon / Thalamus

• Intermediate mass Joins the right and left
  halves of the thalamus

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Diencephalon / Thalamus

• Surrounds the third ventricle

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Diencephalon / Thalamus

• It registers conscious recognition of pain,
  temp., light touch, and pressure.
• You need your cerebral cortex to understand the
  nature of the pain.

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Diencephalon / Hypothalamus

• Inferior to the thalamus

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Diencephalon / Hypothalamus

• Mammillary bodies serve as reflexes related to
  the sense of smell

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Diencephalon / Hypothalamus

• Infundibulum Connects the pituitary gland to
  the hypothalamus

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Diencephalon / Hypothalamus

• Axons from the paraventricular and supraoptic
  nuclei form the hypothalamohypophyseal tract
  extends through the infundibulum to the posterior
  pituitary

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Diencephalon / Hypothalamus

• Functions
• Control of the ANS
• Production of hormones
• Regulation of emotional and behavioral patterns
• Regulation of eating and drinking
• Control of body temperature

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Diencephalon / Epithalamus

• Superior and posterior to thalamus

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Diencephalon / Epithalamus

• Pineal Gland It secretes the hormone melatonin.

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Diencephalon / Subthalamus

• Below the thalamus
• Helps control body movements

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Circumventricular Organs

• Part of the diencephalon called CVOs that can
  monitor chemical changes in the blood because
  they lack a blood-brain barrier

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Circumventricular Organs

• Part of the hypothalamus, the pineal gland, and
  the pituitary gland

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Circumventricular Organs

• Thought to be the site of entry into the brain of
  HIV.

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Cerebrum

• Largest part of the brain

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Cerebrum

• Cerebral cortex is composed of grey matter
• The deep grooves are called fissures
• Shallower grooves are called sulci

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Cerebrum

• Beneath the cortex lies cerebral white matter

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Cerebrum

• Longitudinal fissure separates it into right and
  left halves

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Cerebrum

• The corpus callosum (a bundle of white fibers)
  connects it internally.

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Cerebrum

• Each cerebral hemisphere is separated into four
  lobes (frontal, parietal, temporal, and occipital)

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Cerebrum

• White matter is under the cortex and consists of
  myelinated axons running in three principle
  directions

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Cerebrum

• Association fibers connect and transmit nerve
  impulses between gyri in the same hemisphere

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Cerebrum

• Commissural fibers connect gyri in one cerebral
  hemisphere to the corresponding gyri in the
  opposite hemisphere

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Cerebrum

• Projection fibers transmit impulses from the
  cerebrum to other parts of the brain and spinal
  cord

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Cerebrum

• Basal ganglia are paired masses of grey matter
  internally located in each cerebral hemisphere

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Cerebrum

• The Basal Ganglia function in controlling
  muscular movements

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Cerebrum

• Huntingtons disease is a hereditary degenerative
  disorder of the basal nuclei.
• Patients may suffer from abrubt, jerky, almost
  continuous movements called chorea

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Cerebrum

• Limbic System found in the cerebral hemispheres
  and diencephalon

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Cerebrum

• It functions in emotional aspects of behavior and
  memory, and is associated with pleasure and pain
• We tend to remember things associated with strong
  emotions. (Think back to the events you remember
  from early childhood. What emotions pop up?)

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Lobes of the Cerebrum

• Central Sulcus Separates the frontal lobe from
  the parietal lobe

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Lobes of the Cerebrum

• Precentral gyrus immediately anterior to the
  central sulcus

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Lobes of the Cerebrum

• Postcentral gyrus Located immediately posterior
  to the central sulcus

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Lobes of the Cerebrum

• Lateral cerebral sulcus Separates the frontal
  lobe from the temporal lobe

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Parieto-occipital sulcus

• Separates the parietal lobe from the occipital
  lobe

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Blood-Brain Barrier (BBB)

• Prevents passage of many substances from blood
  into brain tissue

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Blood-Brain Barrier (BBB)

• Endothelial cells of brain capillaries are sealed
  together by tight junctions

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Blood-Brain Barrier (BBB)

• Processes of astrocytes press up against the
  brain capillaries and only allow certain
  substances to pass from the blood to neurons

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Blood-Brain Barrier (BBB)

• Glucose (water soluble) crosses the BBB via
  active transport

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Blood-Brain Barrier (BBB)

• Other water soluble substances such as
  creatinine, urea, and most ions cross slowly

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Blood-Brain Barrier (BBB)

• Proteins and antibiotics cannot cross

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Blood-Brain Barrier (BBB)

• Lipid soluble substances such as oxygen, carbon
  dioxide, alcohol, and most anesthetic agents
  cross easily

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Protective coverings of the Brain

1. Cranium
2. Cranial Meninges continuous with the spinal
   meninges

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Protective coverings of the Brain

• Cranial Meninges made up of
• Dura Mater outer
• Arachnoid Mater middle
• Pia Mater inner

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Protective coverings of the Brain

• Subarachnoid space between the arachnoid mater
  and pia mater which contains cerebrospinal fluid

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Protective coverings of the Brain

• Three extensions of the dura mater separate parts
  of the brain

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Protective coverings of the Brain

• Falx Cerebri Separates the two hemispheres

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Protective coverings of the Brain

• 2. Falx Cerebelli Separates the two
  hemispheres of the cerebellum

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Protective coverings of the Brain

• 3. Tentorium Cerebelli Separates the cerebrum
  from the cerebellum

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Cerebrospinal Fluid

• Clear colorless liquid

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Cerebrospinal Fluid

• Protects the brain and spinal cord against
  physical and chemical injuries

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Cerebrospinal Fluid

• Caries glucose, oxygen, and other chemicals from
  blood to neurons and neuroglia

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Cerebrospinal Fluid

• Circulates through cavities in the brain and
  spinal cord and in the subarachnoid space of the
  brain and spinal cord

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CSF-filled cavities within Brain

• 1. Lateral Ventricles Within each hemisphere
  of the cerebrum

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CSF-filled cavities within Brain

• 2. Third Ventricle A narrow cavity along the
  midline superior to the hypothalamus and between
  the R. and L. halves of the thalamus

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CSF-filled cavities within Brain

• 3. Fourth Ventricle between the brain stem and
  the cerebellum

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Circulation of CSF

• CSF is formed by filtration from networks of
  capillaries called choroid plexuses (found in the
  ventricles) and in the brain tissue

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Circulation of CSF

• It circulates through the
• Lateral ventricles
• Third ventricle
• Cerebral aqueduct
• Fourth ventricle
• Then down through the central canal and around
  the brain (subarachnoid space)

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Circulation of CSF

• Most of the fluid is absorbed by the arachnoid
  villi

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Sensory Areas

• Sensory Areas of the cerebral cortex are
  concerned with the reception and interpretation
  of sensory impulses

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Sensory Areas

• Primary Somatosensory area located in the
  postcentral gyrus

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Sensory Areas

• Primary Somatosensory Area Localizes exactly
  the points of the body where sensations originate

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Sensory Areas

• Primary Visual Area located in the occipital
  lobe and receives impulses that convey
  information for vision

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Sensory Areas

• Primary Auditory Area located in the superior
  part of the temporal lobe

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Sensory Areas

• Primary Auditory Area Helps you interpret
  pitch, rhythm, and loudness of speech

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Sensory Areas

• The primary gustatory area it receives impulses
  for taste and is located in the parietal lobe

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Sensory Areas

• Primary Olfactory Area Located in the medial
  aspect of the temporal lobe and receives impulses
  for smell

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Motor Areas

• Govern muscular movements

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Motor Areas

• Primary Motor Area is in the precentral gyrus

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Motor Areas

• Primary Motor Area - It has cell bodies of
  neurons that descend to the cord

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Motor Areas

• Brocas Area Is located in the frontal lobe
  close to the lateral cerebral sulcus and is the
  motor speech area

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Association Areas

• Association areas are concerned with complex
  integrative functions such as memory, emotions,
  reasoning, will, judgement, personality traits,
  and intelligence

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Association Areas

• Wernickes Area Is a broad region in the
  temporal and parietal lobes

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Association Areas

• Wernickes Area Responsible for understanding
  language, but it may be more involved in sounding
  out unfamiliar words.

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Aphasia

• Aphasia is the inability to use or comprehend
  words due to injury to the association or motor
  speech areas

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Aphasia

• Receptive Aphasia You have problems with
  comprehension but your own language is ok

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Aphasia

• Expressive Aphasia You may comprehend language
  but your speech does not make any sense

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Cranial Nerves

• Twelve pairs of cranial nerves originate from the
  brain

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Cranial Nerves

• Some cranial nerves (I, II, VIII) contain only
  sensory fibers and are called sensory nerves

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Cranial Nerves

• The rest are mixed nerves because they contain
  both sensory and motor fibers