CNS
CNS
Highlight of Learning ObjectivesLearning Goals Learning Outcomes
Understand the importance of cerebrospinal fluid (CSF)
Diagram the secretion and reabsorption of CSF List the composition of CSF and compare it to the composition of plasmaExplain the significance of having a well-controlled CSF
Understand the blood-brain barrier (BBB) and its physiological significance
Diagram the blood supply to the brainDiagram the BBB and explain how it is formedExplain how BBB controls the movement of substances and its physiological significance
Part I Outline
• Protection and support of the brain– The importance and composition of cerebrospinal
fluid– The importance of blood brain barrier
• Major anatomical divisions of the brain and the primary functions of each part
3
Protection of the Brain
• 1) the bones of the cranium• 2) the cranial meninges• 3) cerebrospinal fluid Figure 15-5 M
Dura mater Arachnoid ArachnoidPia mater
Cranial Meninges
Brain Ventricles
Figure 15-6 M
Cerebral Spinal Fluid (CSF)
• Surrounds brain & spinal cord
• Cushion and protection
Figure 15-8 M
Circulation of CSF• CSF is produce by choroid
plexus in the ventricles
• CSF leave the 4th ventricle via paired lateral apertures or the single median aperture
• CSF flows through the subarachnoid space
• Excess CSF flow into the arachnoid villi, then drains into the dural venous sinuses
As CSF circulates, CSF and the interstitial fluid of the CNS have been shown to have similar ion concentrations, what kind of movement is involved?
A. osmosisB. perfusionC. diffusionD. active transporterE. conduction
Clicker Question
Vascularization
Blood supply•Internal carotid arteries•Vertebral arteries
Blood drainage•Internal jugular veins
Internal Carotid A. Vertebral A.
Basilar a
Posterior Cerebral A.
Anterior Cerebral A.
Middle Cerebral A.
The major arterial supply to the brain
Circle of Williscollateral circulation
Posterior cerebral art.
Middle cerebral art.Anterior cerebral art.
What is the composition of brain interstitial fluid?
(A)Similar to plasma(B) Different from plasma
Clicker Question
Blood-Brain Barrier• Role in water and electrolyte
homeostasis• Endothelial cells of brain microvessels– Ensheathed by astrocyte foot processes– Exhibit complex tight junctions– Very limited paracellular solute flux– Regulate composition and volume of
brain interstitial fluid
BBB and Neurovascular unit (NVU)
Abbott NJ et al. (2006) Nat. Rev. Nuero. 7-41-53
BBB ion transporters and channels
• Regulate the brain interstitial fluid volume and composition in healthy, normoxic brain
• Secretion of NaCl and water into the brain– BBB produces up to 30% of brain interstitial fluid
• Absorption of K from brain into blood– BBB maintains low interstitial [K]
Blood-brain barrier regulation of brain interstitial fluid volume and composition
Altered during ischemic stroke
Leads to cerebral edema formation
Edema is a major contributing factor to morbidity and mortality of stroke
Stroke (brain attack)
Two major causes:• Ischemic stroke– Global• E.g. during cardiac arrest
– Focal• E.g., during occlusion of a
cerebral blood vessel
• Hemorrhagic stroke– E.g., following rupture of a
cerebral blood vessel
1. A blood clot2. Endothelial cell 3. Neuron4. Free radicals
Stroke (brain attack)• Early events
• Late events
Concept map
• Blood-brain barrier• CSF• Blood• Interstitial fluid• Ion concentration in the brain• Brain edema• stroke
Part I Outline
• Protection and support of the brain– The importance and composition of cerebrospinal
fluid– The importance of blood brain barrier
• Major anatomical divisions of the brain and the primary functions of each part
22
Superior View Anterior View
Posterior View
Lateral View
Ventral View
Brain Devisions
Sagittal Plane
Coronal Plane
Cerebral Cortex - The outermost layer of gray matter making up the superficial aspect of the cerebrum.
Cerebral Cortical (Neocortex)
• Neocortex - pyramidal (75%) and granule cell– Layer 1 - axons & synapses, few cell bodies– Layer 2 - granule cell– Layer 3 – pyramidal cell– Layer 4 – granule cell– Layer 5 – large pyramidal cell– Layer 6 – pyramidal and other cells 25
Cerebral Features:• Gyri – Elevated ridges “winding” around the brain.
• Sulci – Small grooves dividing the gyri– Central Sulcus – Divides the Frontal Lobe from the Parietal
lobe
• Fissures – Deep grooves, generally dividing large regions/lobes of the brain – Longitudinal Fissure – Divides the two Cerebral
Hemispheres– Transverse Fissure – Separates the Cerebrum from the
Cerebellum– Sylvian/Lateral Fissure – Divides the Temporal Lobe from
the Frontal and Parietal Lobes
Gyri (ridge)
Fissure
(deep groove)
Sulci (groove)
http://williamcalvin.com/BrainForAllSeasons/img/bonoboLH-humanLH-viaTWD.gif
Major Regions of Human Brain
• Cerebrum– Higher brain functions
• Diencephalon– Centers for homeostasis
• Brainstem– autonomic centers and
reflex centers • Cerebellum– Involve in coordination of
movement
Lateral View
Brain Divisions
Cerebrum
• Frontal– Motor, speech, memory
formation, personality, emotion
• Parietal– Somatosensory cortex
• Occipital– Visual processing and
storing visual memories• Temporal
– Hearing, speech and language, smell
Figure 15-1 M* Note: Occasionally, the Insula is considered the fifth lobe. It is located deep to the Temporal Lobe.
Frontal Cortex
• Traditionally considered to be the seat of intelligence
• Working memory problem• Difficulty generating new
items or hypothesies• Lack of Inhibition• Perseveration• Difficulty planning
sequences or organizing strategies
Primary Motor Cortex/ Precentral Gyrus
Broca’s Area
Orbitofrontal Cortex
Olfactory Bulb
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Parietal Lobe• It plays a major role in the
following functions/actions:– Senses and integrates
sensation(s)– Spatial awareness and
perception(Proprioception - Awareness of body/ body parts in space and in relation to each other)
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Primary Somatosensory Cortex/ Postcentral Gyrus
Primary Gustatory Cortex
Somatosensory Association Cortex
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Temporal Lobe
• They play an integral role in the following functions:• Hearing• Organization/
comprehension of language
• Information retrieval• (Memory and memory
formation)
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Korbinian Broadmann - Learn about the man who divided the Cerebral Cortex into 52 distinct regions: http://en.wikipedia.org/wiki/Korbinian_Brodmann
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Primary Auditory Cortex
Wernike’s Area
Primary Olfactory Cortex (Deep)Conducted from Olfactory Bulb
Occipital Lobe – Cortical Regions
• Its primary function is the processing, integration, interpretation, etc. of VISION and visual stimuli.– Primary Visual Cortex –the
primary area of the brain responsible for sight -
– Visual Association Area – Interprets information acquired through the primary visual cortex. recognition of size, color, light, motion, dimensions, etc.
Korbinian Broadmann - Learn about the man who divided the Cerebral Cortex into 52 distinct regions: http://en.wikipedia.org/wiki/Korbinian_Brodmann
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Primary Visual Cortex
Visual Association Area
Korbinian Broadmann - Learn about the man who divided the Cerebral Cortex into 52 distinct regions: http://en.wikipedia.org/wiki/Korbinian_Brodmann
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Primary Language Areas
• Broca’s area• Wenicke’s area• Angular gyrus• Arcuate fasciculus
Language and the Aphasias
Other language dysfunctions
DyslexiaWord deafnessAnomiaConduction aphasia
The Brain from Top to Bottom: From Thought to Language. Broca’s Area, Wernicke’s Area, and Other Language-Processing Areas in the Brainhttp://thebrain.mcgill.ca/fl ash/i/i_10/i_10_cr/i_10_cr_lan/i_10_cr_lan.html
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Conduction Aphasia• Arcuate Fasciculus - A white matter tract that connects Broca’s Area and
Wernicke’s Area through the Temporal, Parietal and Frontal Lobes. Allows for coordinated, comprehensible speech.
Q: Assuming this comical situation was factually accurate, what Cortical Region of the brain would these doctors be stimulating?
Copyright: Gary Larson
Primary Motor and Somatosensory Cortex
* This graphic representation of the regions of the Primary Motor Cortex and Primary Sensory Cortex is one example of a HOMUNCULUS:
Q: What do you notice about the proportions depicted in the aforementioned homunculus?
Q: What is meant by depicting these body parts in such outrageous proportions?
* Note: Homunculus literally means “little person,” and may refer to one whose body shape is governed by the cortical area devoted to that body region.
Phineas Gage was a railroad worker in the 19th century living in Cavendish, Vermont. One of his jobs was to set off explosive charges in large rock in order to break them into smaller pieces. On one of these instances, the detonation occurred prior to his expectations, resulting in a 42 inch long, 1.2 inch wide, metal rod to be blown right up through his skull and out the top. The rod entered his skull below his left cheek bone and exited after passing through the anterior frontal lobe of his brain.
A Case Study
Remarkably, Gage never lost consciousness, or quickly regained it (there is still some debate), suffered little to no pain, and was awake and alert when he reached a doctor approximately 45 minutes later. He had a normal pulse and normal vision, and following a short period of rest, returned to work several days later. However, he was not unaffected by this accident.
Learn more about Phineas Gage: http://en.wikipedia.org/wiki/Phineas_Gage
http://www.sruweb.com/~walsh/gage5.jpg
Q: Recalling what you have just learned regarding the frontal lobe, what possible problems or abnormalities may Gage have presented with subsequent to this type of injury (remember the precise location of the rod through his brain)?
Q: It is suggested that Gage’s injury inspired the development of what at one time was a widely used medical procedure. What might this procedure be, and how does it relate to Gage’s injury?