Chapter 13

Cerebrum Characteristics

1. Usually difficult to assign precise function to specific region (overlapping & indistinct boundaries, some aspects not easily assigned to any single region, like memory) 2. Innervation (hemispheres receiving info form opposite side of body, and hemispheres projecting motor commands to opposite side of body. I.E. right cerebral hemisphere controlling left side of body) 3. Functional differences between hemispheres (termed cerebral lateralization. I.E. Regions of brain responsible for speech in left cerebral hemisphere. Primarily affects higher-order function)

Step 2 of CSF Flow

2. CSF flows from the lateral ventricles, through the inter ventricular foramen into the third ventricle, and then through the cerebral aqueduct into the forth ventricle

Step 3 of CSF Flow

3. CSF in the fourth ventricle passes through the paired lateral apertures or the single median aperture, and into the subarachnoid space as well as the central canal of the spinal cord.

Association Areas

-Connected to adjacent motor and sensory regions -Process & interpret data or coordinate motor response -Integrate new sensory inputs w/memories -Premotor Cortex (details on different flash card) -Somatosensory association area (details on diff. card) -Visual association area (details on different card) -Auditory Association Area (see diff. card for details)

Motor Area of Cerebrum

-Control voluntary motor functions, -housed within frontal lobes, -Primary motor cortex located in pre central gyrus of lobe -control voluntary skeletal muscle activity project contralaterally within brainstem or spinal cord. -Within PREcentral gyrus

Cerebrum: Frontal Lobe (Structure)

-Deep to frontal bone. -Forms anterior part of cerebral hemisphere -Ends posteriorly at deep groove, central sulcusends inferiorly at groove, lateral sulcus

Cerebrum: Parietal Lobe (Structure)

-Deep to parietal bone -Forms superoposteriar part of cerebral hemisphere -Terminates anteriorly at central sulcus -Terminates posteriorly at parieto-occipital sulcus -Termites laterally at lateral sulcus

Sensory Areas: Primary Somatosensory Cortex

-Housed with POSTcentral gyrus of parietal lobes. -Receives somatic sensory info from: proprioceptors, touch, pressure, pain, and temperature receptors. -Sensory homunculus can be traced on postcentral gyrus -Surface indicates amount of sensory info collected within that regionlarge -Regions for lips, fingers, and genital regions.

Cerebrum: Occipital Lobe (Structure)

-Internal to occipital bone -Forms posterior part of cerebral hemisphere

Cerebrum: Temporal Lobe (Structure)

-Internal to temporal bone -Inferior to lateral sulcus

Broca's Area

-Located in inferolateral portion of left frontal lobe (in most people) -Controls muscular movement for vocalization

Primary Gustatory Cortex

-Located within insula -Involved in processing taste info

Primary Olfactory Cortex

-Located within temporal lobe -Provides conscious awareness of smells

Primary Visual Cortex

-Located within the occipital lobe -Receives & Processes incoming visual info

Primary Auditory Cortex

-Located within the temporal lobe -Receives & Processes auditory info

Motor Areas: Frontal Eye Field

-On superior surface of middle frontal gyrus -Regulates eye movements needed for reading and binocular vision

Types of Sensory Areas

-Primary Visual Cortex -Primary Auditory Cortex -Primary Olfactory Cortex -Primary Gustatory Cortex

Cerebrum: Insula Lobe (Structure)

-Small lobe deep to lateral sulcus -Can be observed by laterally pulling aside temporal lobe (only way to see it!)

Premotor Cortex

-Within frontal lobe anterior to pre central gyrus -Responsible for coordinating skilled motor activities

Visual Associal Area

-Within occipital lobe -Surrounds primary visual area -Helps process visual info -Helps us identify things we see -I.E. helps integrate visual info into recognizable face

Somatosensory Association Area

-Within parietal lobe posterior to primary somatosensory complex, integrates sensory info -Determines texture, temperature, pressure & shape of objects -Allows us to identify known objections without seeing them

Auditory Association Area

-Within temporal lobe, posteroinferior to primary auditory complex -Interprets characteristics of sound -Stores memories of sound heard in past

Step 1 of CSF Flow

1. CSF is produced by the choroid plexus in the ventricles

MUST know correct flow of Cerebrospinal Fluid

1. CSF is produced by the choroid plexus in the ventricles 2. CSF flows from the lateral ventricles, through the inter ventricular foramen into the third ventricle, and then through the cerebral aqueduct into the forth ventricle 3. CSF in the fourth ventricle passes through the paired lateral apertures or the single median aperture, and into the subarachnoid space as well as the central canal of the spinal cord. 4. As the CSF flows through the subarachnoid space, it provides buoyancy to support the brain. 5. Excess CSF flows into the arachnoid villi, then drains into the dural venous sinus. The greater pressure on the CSF in the subarachnoid space ensures that CSF moves into the venus sinuses without permitting venous blood to enter the subarachnoid space.

Step 4 of CSF Flow

4. As the CSF flows through the subarachnoid space, it provides buoyancy to support the brain.

Step 5 of CSF Flow

5. Excess CSF flows into the arachnoid villi, then drains into the dural venous sinus. The greater pressure on the CSF in the subarachnoid space ensures that CSF moves into the venus sinuses without permitting venous blood to enter the subarachnoid space.

Barrier is missing or reduced in 3 locations

1. Choroid Plexus ( Needs to be permeable to produce CSF) 2. Hypothalamus (Hormones) 3. Pineal Gland (Secretes Melatonin)

Cerebrospinal Fluid Main 7 Points

1. Clear, colorless liquid, 2. Circulates in ventricles & subarachnoid space, 3. Bathes & completely surrounds surfaces of CNS, 4. Buoyancy, 5. Prevents collapse of brain through foramen magnum, 6. Protection, 7. Environmental stability

3 Functional areas of Cerebrum

1. Motor Area 2. Sensory Area 3. Association Area

Parts of the Central Nervous System

Brain and Spinal Cord

Motor Areas: Motor Speech Area

Broca's Area

What components make up the BBB?

Capillary endothelial cells (w/tight junctions), basement membrane, perivascular feet of astrocytes

Ventricles

Cavities within the brain, derived from neural canal, lined with ependymal cells, contain cerebrospinal fluid, share communications with each other, communication with spinal cord's central canal

What are the 4 major portions of the brain?

Cerebrum, Cerebellum, Brainstem, Biencephalon

What is Cerebral Gray Matter?

Color from motor & interneuron cell bodies, dendrites, and unmyelinated axons

What is Cerebral White Matter?

Color from myelin on axons

Cerebrum Composition

Composed of 2 halves, left & right cerebral hemispheres. Separated by deep cleft: longitudinal fissure Hemispheres are separate, except at a few locations..Bundles of axons, tracts form white matter connecting regions

What protects and support the brain?

Cranial Meninges

Cranial Dural Septa

Double layers of dura mater, extend as flat partitions into the cranial cavity, separate specific parts of the brain, stabilize & support the brain. 4 locations (falx cerebri, tentorium celebelli, falx cerebella, & diaphragma sellae)

From superficial to deepest, name the meninges and the spaces between them

Dura Mater --> Subdural Space (potential space) --> Arachnoid Mater --> Subarachnoid Space --> Pia Mater

CSF Formation

Formed by Choroid Plexus, Produced by Secretion from Ependymal Cells, Originates from blood plasma, Composition somewhat similar to plasma

Cerebrum: Insula Lobe (Function)

INVOLVED IN: -Memory -Interpretation of taste

Pia Mater

Innermost of cranial meninges, thin layer of areolar connective tissue, tightly adheres to the brain, follows contours of brain surface

Where is the CSF first produced?

It is first produced by the choroid plexus in the ventricles

How does excess CSF get removed from the blood?

It is removed from the blood after flowing into the arachnoid villi, which drain into the dural venous sinuses.

What are the 3 main functions of cerebrospinal fluid?

It provides BUOYANCY, PROTECTION, & ENVIRONMENTAL STABILITY to the brain.

What is the function of the corpus callous (Important per Ebert)

It provides the main method of communication between the cerebral hemispheres (They need to talk!!)

Dura Mater

Lies external to arachnoid mater, tough dense irregular tissue, forms the periosteum on internal surface of cranial bones, layers usually fused, separate in specific areas, form large blood-filled spaces (dural venous sinuses)

Arachnoid Mater

Lies external to pia mater, partially composed of collagen & elastic fibers, trabecular extending deep to reach pia mater, extend through subarachnoid space, contains cerebrospinal fluid

Barrier NOT Absolute

Lipid-soluble compounds: - can diffuse across endothelial plasma membranes (I.E. nicotine, alcohol, some anesthetics) - Can be damaged by drugs such as cocaine

BBB Composition

Most capillaries in brain wrapped by perivascular feet (astrocyte extensions). Endothelial cells & perivascular feet both contributing to the BBB. Continuous basement membrane of endothelial cells. Tight junctions between adjacent endothelial cells (reduce capillary permeability). Astrocyte, "gatekeepers" controlling materials leaving neurons

Cerebrum

Origin of all complex intellectual functions. 2 large hemispheres on superior aspect of brain intelligence & reasoning, thought, memory, & judgment Voluntary motor, visual, & auditory activities

Cerebrum: Frontal Lobe (Function)

PRIMARILY CONCERNED WITH: -Voluntary motor functions, -concentration and verbal communication, -decision making, planning, and personality

Cerebrum: Parietal Lobe (Function)

PRIMARILY CONCERNED WITH: - General sensory functions (sensory refers to sight/taste) - I.E. evaluating shape and texture of objects.

Cerebrum: Temporal Lobe (Function)

PRIMARILY CONCERNED WITH: -Involved with hearing and smell

Cranial Meninges Parts

Pia Mater, Arachnoid Mater, Dura Mater

Subarachnoid Space

Potential space between arachnoid and overlying dura mater, becomes actual space if blood or fluid accumulators there - termed subdural hematomas

Cerebrum: Occipital Lobe (Function)

RESPONSIBLE FOR: -Processing visual info -Storing visual memories

Choroid Plexus

Specialized tissue in each ventricle, layer of ependymal cells and blood capillaries (within pia)

Blood Brain Barrier (BBB)

Strictly regulates which substances enter brain's interstitial fluid. Helps prevent neuron exposure to harmful substances (i.e. drugs, blood wastes products, variations in levels of normal substances)

Cerebrum

Superficial region of gray matter, termed cerebral cortex covers surface white matter, deep to gray matter clusters of gray matter within white matter, cerebral nuclei clusters of neuron cell bodies

How are the lateral ventricles connected to the third ventricle?

They both connect through an opening, the inter ventricular foramen

Dural Venous Sinuses

Typically triangular in cross section, lack valves, drain blood from the brain