BIOM 3200 Chapter Notes - Chapter 3: Cerebrospinal Fluid, Precentral Gyrus, Arachnoid Mater

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Unit 3: The Nervous System
Caudally= posteriorly (near the tail)
Rostrally= near the front end of the body
Coronally (frontally)= divided front and back “belly and back”
Brain- composed of neurons and support cells
- Sensory peripheral nerves send information to the brain, which integrate the information and
generates a response
Response can be motor functions, or higher brain functions
The brain is connected caudally with the spinal cord
- Ascending tracts convey information from the periphery to the brain
- Descending tracts send motor nerve impulses down the spinal cord
Brain develops from the embryonic ectodermal neural tube
- Cavity becomes a fluid-filled ventricular system
- Walls develop into neurons of the brain
Front-to-back:
- Telencephalon
- Diencephalon
- Mesencephalon
- Metencephalon
- Myelencephalon
Parts of the brain:
- Cerebral hemispheres
- Thalamus and hypothalamus
- Midbrain
- Pons and cerebellum
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- Medulla oblongata
The telencephalon develops at an accelerated rate
- The cerebral hemispheres cover the thalamus, hypothalamus, and parts of the pons and
cerebellum
The Ventricles
- Cavities of the neural tube remain as cavities during development of the mammalian brain
The brain contains fluid-filled chambers called ventricles:
- Filled with cerebral spinal fluid (CSF), which is produced by specialized tissue found in each of
the ventricles, called choroid plexus
- CSF provides nourishment and protection as a shock absorber
- The large lateral (side) ventricles are deep in the cerebral hemispheres and join caudally
(towards the back) and at the midline to the 3rd ventricle at the level of the diencephalon
- At the level of the midbrain, the ventricle narrows into the aqueduct, which communicates with
the 4th ventricle at the level of the pons, cerebellum, and medulla
**The ventricle system continues into the spinal cord as the central canal
** CSF escapes the ventricles through small openings called foramen (located in the lateral ventricles
and 4th ventricle), and into the subarachnoid space
The Meninges
3 connective tissue layer that surround the brain and spinal cord
Outer layer dura mater (tough connective tissue)
Middle layer arachnoid mater (delicate membrane)
Inner layerpia mater (delicate membrane that is intimately associated with the surface of the brain)
Subarachnoid space
- Space between pia and arachnoid mater filled with CSF
- Provides a buoyant layer that protects the brain from mechanical damage
- CSF drains through specialized areas of the meninges called arachnoid villi into venous
circulation
** The brain and spinal cord are continuously bathed and float in a layer of CSF
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Cerebrum
- Higher brain functions arise in the cerebrum
- Large, wrinkled, mushroom-shaped structure that partially covers the whole brain
- Grooves called sulci form elevated folds balled gyri
Surface grey matter (consists of cell bodies)
Deep inside whiter matter (consists of myelinated axons that connect the grey areas with other parts
of the brain
Cell bodies found in white matter often collect in groups (clump) and form distinct grey areas,
called nuclei
Divided into left and right hemispheres by a deep groove called a longitudal fissure
Each area of the cerebrum can be divided anatomically, and named corresponding to the skull
bones over top of them
Central sulcus
- Divides the cerebrum coronally into the anterior (front) and posterior (back) parts
- - marks the division of the frontal and parietal lobes
Lateral sulcus
- A large groove found on each side of the brain and marks the temporal lobe from the frontal
and parietal lobes
Posterior part of the cerebrum is the occipital lobe
Each area corresponds to a specific function
Precentral gyrus
- Part of the frontal lobe adjacent to the central sulcus
- Consists of upper motor neurons, which sends its axons down through the brain and spinal cord,
to synapse on lower motor neurons
- Lower motor neurons leave the spinal cord (as part of the PNS), and innervate skeletal muscles
at the neuromuscular junctions
- Therefore, the precentral gyrus is involved in voluntary muscle movement
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