51 terms

Central Nervous System 2

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central nervous system
Gray matter
Whie matter

I. The Brain Interpret sensory info, issue appropriate motor commands, carry on all higher intellectual functions

II. Diencephalon
III. Brain Stem
IV. Cerebellum
gray matter
Forms the surface area (what you see when you first look at the brain, and hold it in your hand) of the brain called the cortex. It is mostly made of unmyelinated fibers and cell bodies.
White Matter
Lies deep to the cortical gray matter. A dense collection of myelinated fibers calls tracts, or bundles of axons that are connected to one part of the brain to another.
The Brain
Interpret sensory info, issue appropriate motor commands, carry on all higher intellectual functions.

a. Cerebral Hemispheres
> Gyri
> Sulci
> Fissures
> Longitudinal fissures
> Lobes
Cerebral Hemispheres
most superior part of the brain
Gyri
=elevated wrinkle or fold in the cortex of the cerebrum or cerebellum.
Sulci
=shallow grooves between gyri.
Fissures
=deeper grooves that separate larger regions of the brain.
Longitudinal fissures
separate hemispheres.
Lobes
=fissures or sulci that further divides the hemispheres
Frontal Lobe
-primary motor area of cerebrum. Thinking, reasoning, speech.
Pyramidal/corticospinal tract
part of the decending tracts that conduct motor impulses down the spinal cord.
Broca's Area
generates a motor program for the muscles of the larynx, tongue, cheeks and lips to produce speech. Damage to the area reduces a persons ability to articulate words
Superficial gray matter
cerebral cortex
Deep white matter
tracts that carry information to or from the cortex
Corpus callosum
connects the cerebral hemispheres. It joins the functions of the hemispheres so that the right and left sides communicate.
Basal nuclei
--. "islands' of gray matter buried within the white matter. Their function is to regulate voluntary motor activities by modifying instructions sent to skeletal muscle by the primary motor cortex Parkinson's disease patients have degeneration in this area.
Diencephalon
1. Thalamus
2. Hypothalmus
3.Epithalmus
Diencephalon
(interbrain) located on top of the brain stem and enclosed by the cerebral hemispheres.
Thalmus
relay station for sensory impulses
Hypothalmus
relay station for the ANS. Includes the
pituitary gland, mammillary bodies
Epithalmus
Helps to make CSF. Includes the pineal
body, choroids plexus
Brain Stem
Midbrain
Pond
Medulla oblangata
Reticula formation
Brain Stem
(under-side of Brain) thumb size, approx 3 in long
Midbrain
-vision, hearing
Pons-
respiration
Medulla Oblongata
-regulates vital life activities (BP,
Respiration, HR...)
Reticular Formation
extends the entire length of the
brainstem and is composed of gray matter. It is responsible for motor control of visceral organs.
RAS
RAS
consciousness and awake/sleep cycles
Cerebellum
: Second largest part of the Brain. Located below and
partially covered by the cerebellum. Coordinates voluntary movement and makes movement smooth. Helps to maintain balance/equilibrium. 2 hemispheres, outer cortex of gray matter, and inner region of white matter.
Spinal Cord
• 17 inches long depending on the persons height
• continuation of the brain stem
• 2 way conduction pathway to and from the brain and a major reflex center
• extends from the foramen magnum to the first or second lumbar vertebra
just below the ribs
• During spinal tap, you remove CSF around L3 because in this area there
is less of a chance of damaging the spinal cord
Protecting the CNS
Bones
Meninges 3 connected be tissue
Bones
vertebrae, skull bones
Meninges
-3 connective tissue coverings that protect the brain and
spinal cord.
Meninges
Dura matter
Arachnoid matter-middle layer.
Pia matter-innermost layer.
Dura matter
outermost protective layer, very tough.
1. Subdural space
Arachnoid matter
middle layer. Delicate, web-like.
1. Subarachnoid space
Cerebral Spinal Fluid (CSF)
Fluid occupying the 4 ventricles of the brain, the space between the meninges, and the central canal of the spinal cord.
CSF
Brain floats in CSF and therefore reduces brain weight.
• Composition similar to blood plasma from which it arises
• Contains Vitamins C, Na, Cl, Mg, H, and less Ca and K.
• pH is important in control of cerebral blood flow and breathing
• Transports hormones
• The Choroid Plexuses that hang from the roof of each ventricle produce CSF

Tissue fluid filters through capillaries in this area from the blood stream. The ependymal cells of the ventricles only allow certain ions in and water to diffuse into the ventricles.
• Adults CSF = 1/2 cup is replaced every 3 to 4 hours
• Constant motion of CSF is aided by ciliated ependymal cells
• CSF returns to the blood in the dural sinuses via the arachnoid villi
Ventricles of the Brain:
a. continuous with each other and with the central canal of the spinal cord.
b. Filled with CSF (cerebral spinal fluid)
c. Lined with ependymal cells
Lateral Ventricles
(1st and 2nd Ventricles)
1. "C" shaped
2. located deep with in each cerebral hemisphere
3. each lateral ventricle communicates with the third ventricle via the interventricular foramen.
Third Ventricle
1. located in diencephalon
11
2. continuous with the fourth ventricle via the canal-like cerebral aqueduct that runs through the midbrain.
fourth ventricle
1. located dorsal to pons and superior to medulla
2. continuous with central canal of spinal cord
3. 3 openings (apertures) connect the ventricles to the subarachnoid space
blood-brain barrier
• protective mechanism that helps maintain a stable environment for the brain....the brain needs consistency----separated from the extra cellular environment.
• Blood borne substances with in the brain's capillaries are separated from the extra cellular space and neurons by:
1. The continuous endothelium of the capillary wall.
2. Thick basal lamina surface surrounding the external face of the capillary 3. Bulbous "feet" of the astrocyte that cling to the capillary.
• Least permeable capillaries in the entire body. Astrocytes help form these tight junctions by stimulating the endothelial cells to come in extremely close contact.
• The blood brain barrier is ONLY ineffective against fats, fatty acids, oxygen, and carbon dioxide and other fat-soluble molecules such as alcohols, nicotine, and anesthetics can affect the brain.
• We are missing the blood brain barrier in some areas such as:
1. Around the 3rd and 4th ventricles because this is the region of vomiting
center of the brain stem which monitors blood for poisonous substances.
2. Hypothalmus because it regulates the chemical environment and therefore needs to sample the chemical composition of blood
3. Absent in newborns and premature infants....only develops after birth, after skull has closed.
reflex
=automatic, involuntary response to some change, either inside or outside the body. They are important in maintaining homeostasis by making adjustments to heart rate, breathing rate, and blood pressure.
components of a reflex arc
1. Receptor
2. Sensory Neuron
3. Integration Center
4. Motor Neuron
5. Effector
Receptor
=Site of stimulus action; receptor end of a dendrite
sensory neurons
=Cell body in ganglion outside CNS; axon in CNS
Integration center (CNS)
=In CNS; synapse between sensory and motor neuron, interneurons may also be involved.
motor neurons
=dendrites and cell body in CNS; axon extends into periphery
Effector
=muscle or gland outside CNS.