Central Nervous System ppt

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?