Human Anatomy

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Human Anatomy

• Central Nervous System
• Part I
• The Brain

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CNS

• Consists of 2 anatomical components

Brain Spinal cord
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The Brain

• 3 subdivisions
• A. Cerebrum
• B. Cerebellum
• Brainstem
• Additional Structures

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Subdivisions of the Brain

• A. Cerebrum
• B. Cerebellum
• Brainstem

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Sagittal Section of Brain

• A. Cerebrum
• B. Cerebellum
• Brainstem
• Additional
• structures

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A. The Cerebrum

• Surface forms a series of elevated ridges gyri
  (gyrus, sng.)
• Surface also has shallow depressions sulci
  (sulcus, sng.)

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Gyri of Cerebrum
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Sulci of Cerebrum
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Central Sulcus
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Lateral Sulcus
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Longitudinal Fissure
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Cerebral Hemispheres

• Cerebrum consists
• of two cerebral
• hemispheres

Left Right
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Lobes of the Cerebrum
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Lobes of the Cerebrum

• Four lobes from the surface

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Four Lobes of Cerebrum(that can be seen on the
lateral surface)

• Frontal
• Parietal
• Occipital
• Temporal

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Cerebral Lobes
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1. Frontal Lobe

• Forms the anterior portion of the cerebral
  hemispheres
• Posterior boundary is central sulcus
• Inferior boundary is lateral sulcus
• Most posterior gyrus is the precentral gyrus
• Precentral gyrus is primarily concerned with
  voluntary motor (skeletal muscles) function. It
  is also known as the primary motor cortex of the
  brain.

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Frontal Lobe
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Precentral Gyrus
Precentral Gyrus Central Sulcus
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Organization of precentral gyrus(primary motor
cortex)
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Precentral Gyrus
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Brocas Speech Area(motor speech area)
Controls muscles neccesary for vocalization (word
s)
Usually found in left frontal lobe
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Frontal Lobe
Frontal eye field
Cognitive activities judgement,
reasoning, planning See Clinical Views on pp.
459 461
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2. Parietal Lobe

• Posterior to the central sulcus
• Anterior to the occipital lobe
• Most anterior gyrus is the postcentral gyrus
• Postcentral gyrus receives information from the
  body such as touch, pressure, pain and
  temperature. It is also known as the primary
  somatosensory cortex.

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Parietal Lobe
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Postcentral gyrus
Central sulcus
Postcentral gyrus
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Organization of postcentral gyrus(primary
somatosensory cortex)
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Postcentral gyrus
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Parietal Lobe
Wernickes area understanding speech and
formulating words to express thoughts and emotions
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3. Occipital Lobe

• Forms the posterior region of each cerebral
  hemisphere
• Responsible for processing incoming visual
  information and storing visual memories
• Known as the visual cortex

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Occipital Lobe
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Occipital Lobe
Occipital lobe
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4. Temporal Lobe

• Inferior to lateral sulcus
• Involved with hearing, interpreting speech and
  language and smell
• Known as the auditory cortex

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Temporal Lobe
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Brodmann Areas (1 century ago)
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B. The Cerebellum

• 2 cerebellar hemispheres
• Coordinates and fine-tunes skeletal muscle
  movements
• Ensures the pattern of skeletal muscle
  contractions leads to smooth, coordinated
  movements
• Stores memories of previously learned patterns of
  movement (writing, piano playing, ping pong,
  Gameboy)
• Cerebrum sends rough draft of which movement it
  wants and cerebellum coordinates and fine-tunes
  the command.
• Adjusts skeletal muscle activity to maintain
  equilibrium and posture

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Effects of alcohol and drugson the cerebellum

• Disturbance of gait
• Loss of balance and posture
• Inability to touch your finger to your nose with
  your eyes closed.lack of proper proprioceptive
  information

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B. The Cerebellum
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C. Brainstem

• Consists of the following regions
• Mesencephalon
• Pons
• Medulla oblongata
• Brainstem is the most primitive part of the brain.

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Brainstem
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1. Mesencephalon
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Mesencephalon

• Roof is made up of 4 bumps called the corpora
  quadrigemina (4)
• Superior colliculi (2) visual reflex centers,
  help track objects within a visual field and
  coordinates skeletal muscles in order to keep
  object in visual field
• Inferior colliculi (2) audio reflex centers,
  involve reflex turning of head in the direction
  of a sound.BANG!

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Corpora quadrigemina
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2. Pons

• Anterior surface of brainstem
• Contains nerve pathways
• Brain Spinal cord

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3. Medulla oblongata

• Most inferior part of the brainstem and is
  continuous with the spinal cord
• Medulla ends and spinal cord begins at the
  foramen magnum
• Contains several autonomic centers that control
  the following functions
• Cardiac center controls heart rate and strength
  of contraction
• Vasomotor center controls blood pressure by
  regulating constriction or relaxation of
  arteriole walls
• Respiratory center controls rate of respiration

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Medulla oblongata
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Medulla oblongata
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Medulla oblongata

• Descending axons (motor) cross over to the other
  side in the medulla oblongata
• Ascending axons (sensory) cross over to the other
  side in the medulla oblongata
• Therefore, a stroke (CVA) on one side of the
  brain will affect the body on the opposite side

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D. Additional Structures in the Brain

• Corpus callosum
• Thalamus
• Hypothalamus

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1. Corpus callosum

• A physical connection between the 2 cerebral
  hemispheres
• A pathway of communication between the 2 cerebral
  hemispheres
• Comprised mainly of myelinated axons traveling
  from one hemisphere to the other hemisphere

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Corpus callosum
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Corpus callosum
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2. Thalamus

• Serves as a processing and final relay point for
  sensory information going to the cerebrum
• Used when you are busy trying to filter out
  visual and auditory input to get the right
  information needed to get you on task
• Sensory thalamus cerebrum

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Thalamus
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3. Hypothalamus

• Inferior to the thalamus
• CEO of ANS
• CEO of endocrine system (hormones)
• Regulates body temperature (thermostat)
• Controls emotional behavior, eating and water
  intake
• Regulates sleep-wake (circadian) rhythms

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Hypothalamus
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The Meninges

• Consists of 3 layers of connective tissue that
  surround the brain and spinal cord
• Functions as a shock absorber to prevent contact
  w/ surrounding bone (skull and vertebrae)
• From superficial to deep
• Dura mater
• Arachnoid mater
• Pia mater

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Meningeal Layers
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1. Dura mater

• Most superficial
• 2 layers
• Periosteal in contact with bone
• Meningeal deeper of the 2 layers, in contact
  with arachnoid mater

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Dura mater
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2. Arachnoid mater

• Middle layer, resembles a spider web
• Comprised of collagen and elastin fibers

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3. Pia mater

• Deepest layer, tightly adhered to brain

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Epidural and SubduralHemorrhages

• Epidural
• Bleeding between skull and endosteal layer of
  meninges
• Source of blood is usually torn artery
• Artery pressure is high, vein pressure is not as
  high
• Blood builds up in epidural space
• Causes compression of brain
• Presses brainstem against occipital bone

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2. Subdural Hemorrhage

• Source of blood is usually from torn vein
• Vein pressure is not high
• Not as acute (not rapid)

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Ventricles of the Brain

• Fluid-filled cavities within the brain
• Filled with CSF (cerebral spinal fluid)
• Store CSF do not make it
• 4 ventricles

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Ventricles of the Brain

• 2 lateral ventricles
• 3rd ventricle
• 4th ventricle
• Mesencephalic
• aqueduct
• All 4 ventricles
• are connected
• and filled with
• CSF

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Ventricles of the Brain

• 2 lateral ventricles
• 3rd ventricle
• 4th ventricle
• Mesencephalic
• aqueduct
• All 4 ventricles
• are connected
• and filled with
• CSF

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Cerebral Spinal Fluid (CSF)

• Liquid similar to plasma
• floats the brain inside skull
• Protects brain by serving as a cushion from
  sudden movements
• Transports chemical messages and nutrients and
  removes waste products to circulatory system

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Cerebral Spinal Fluid