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Flashcards in chapter 11 - CNS Deck (65)
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1

primary regions of the brain

cerebrum
thalamus
pineal gland (part of epithalamus)
hypothalamus
pituitary gland
mid brain
pons
medulla oblongata
spinal cord
cerebellum

2

brains ventricles are lined with

Ependymal cells.

The ependyma is made up of ependymal cells called ependymocytes, a type of glial cell. These cells line the CSF-filled ventricles in the brain and the central canal of the spinal cord. These are nervous tissue cells with a ciliated simple columnar shape much like that of some mucosal epithelial cells.

3

locations of the ventricles of the brain

The brain ventricles are four cavities. within each cerebral hemisphere the two large, C shaped, lateral ventricles are located in the frontal, temporal and occipital lobes. A thin membrane called ‘septum pellucidum’ separates them

the third ventricle is under the corpus callosum in the brains mid line. surrounded by the diencephalon. connected to the lateral ventricles via the intraventricular foramen.

the fourth ventricle is in the brain stem and a narrow ‘cerebral aqueduct’, which runs through the mid brain, joins it to the third ventricle.

The ventricles are all an important part of the “ventricular system.” The ventricles are interconnected with each other, and also with the central canal of the spinal cord and with the subarachnoid space (a space between two of the linings that separate the brain from the skull). CSF is produced by the lining of the ventricles. The CSF then circulates throughout the ventricular system and is eventually reabsorbed in the subarachnoid space.

4

cerebrum and cerebral cortex

Cerebrum is the largest and the most prominent part of the brain, whereas the cerebral cortex is the outer layer of the cerebrum. Cerebral cortex is actually a part of the cerebrum. ... The cerebrum has both gray and white matter, whereas the gray matter is considered to be the cerebral cortex.

5

pituitary gland attachment

The gland is attached to a part of the brain (the hypothalamus) that controls its activity. The anterior pituitary gland is connected to the brain by short blood vessels. The posterior pituitary gland is actually part of the brain and it secretes hormones directly into the bloodstream under the command of the brain.

6

cerebral hemispheres

cerebrum is divided into two large hemispheres, one on the left and one on the right.

they form the superior part of the brain and account for 83% of its mass.

7

corpus callosum

the corpus callosum is a deep bridge of nerve fibers that connects the hemispheres, separated by a layer of dura mater.

it lies superior to the lateral ventricles, deep inside the longitudinal fissure.

8

gyri, sulcus and fissure

the cerebrums surface is covered in gyri, which are separated by shallow or deep grooves.

each shallow groove is called a sulcus

each deep groove is called a fissure. The fissures separate large regions of the brain.

all these grooves form distinct patterns in normal brains, with the gyri and sulci being more prominent.

9

sulci

divide each hemisphere into frontal, parietal, temporal and occipital lobes (as well as a structure called the insula)

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insula

is a brain lobe but is buried deep within the lateral sulcus, forming a portion of the brain floor.

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median longitudinal fissure

separates the cerebral hemispheres

12

transverse cerebral fissure

separates the cerebral hemispheres from the cerebellum below them

13

3 basic regions of each cerebral hemisphere

cerebral cortex - is superficial grey matter

white matter - more internal

basal nuclei - are islands of grey matter located deep inside the white matter

14

Cerebrum - Cerebral Cortex

Thin outer layer of cerebrum made up of grey matter

Grey matter contains: dendrites, nueron cell bodies, glia, blood vessels

It lacks fibre tracts

Is the centre of the conscious mind: awareness, communication, sensation, memory, understanding and initiation of voluntary movements

Contains 75% of all neuron cell bodies of the NS.

2-4mm thick BUT makes 40% off brain mass

Surface area tripled by convolutions/folding of the surface into gyri, sulci, fissures and the Insula.

Cortical functions are specialised, which exhibits a phenomenon known as ‘lateralisation’. No functional area acts on its own, and conscious actions use the entire cortex in varying ways.

15

Cerebrum - Cerebral White Matter

Beneath the cerebral cortex is white matter comprising most of the cerebrum.

Contains myelinated axon bundles. Some pass between hemispheres, others carry impulses from the cortex to nerve centres of the brain and spinal cord.

The internal cerebral white matter controls communication between areas of the cerebrum and between the cerebral cortex and lower centres of the CNS. Myelinated fibers bundled into large tracts make up most of the white matter.

The fibers are classified by the directions in which they run.

Association fibers connect the various parts of the same brain hemisphere. Adjacent gyri are connected by short association fibers called ‘acruate fibers’. Different cortical lobes are connected by long association fibers which are bundled into tracts.

Corresponding grey areas of both hemisphere are connected by commissural fibers or commissures, which allow the hemispheres to function together. The corpus callosum in the largest commissure.

Projection fibers enter the cerebral cortex from the spinal cord or lower brain areas or descend to lower areas from the cerebral cortex. They allow motor output to leave the cerebral cortex and also sensory information to reach it.

Project fibers are different from association and commissural fibers in that they run vertically.

Projection fibers at the top of the brainstem form a compact ‘interal capsule’ passing between the thalamus and certain basal nuclei. They then have a fan like radiating pattern through the cerebral white matter and are therefore referred to as the ‘corona radiata’

16

Dominant hemisphere

In most people one hemisphere of the cerebrum is dominant, controlling the use and understanding of language.

Left hemisphere usually responsible for activities such as speech, writing reading, and complex intellectual functions.

The non-dominant hemisphere controls non-verbal functions and intuitive and emotional thoughts.

The dominant hemisphere controls the motor cortex of the non-dominant hemisphere.

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Function of the cerebrum

Aside from sensory and motor control, memory and reasoning, the cerebrum also coordinates intelligence and personality. Functions overlap between regions of the cerebral cortex.

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Three functional areas of the cerebral cortex

The motor cortex

The sensory cortex

The association cortex

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Each cerebral hemisphere controls the motor and sensory functions of the...

Contralateral (opposite) side of the body

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Motor areas

Most of the cerebral cortex motor areas are located in the frontal lobes and are further defined as the:

Primary motor cortex
Premotor cortex
Broca’s area
Frontal eye field

Impulses from large ‘pyramidal cells’ in the motor areas travel through the brain stem in to the spinal cord via the ‘corticospinal’ tracts that form synapses with lower motor neurons. Their axons leave the spinal cord, reaching the skeletal muscle fibers.

21

Tracts

Bundles of neuron processes in the central nervous system (CNS)

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The primary motor cortex

Also known as the ‘somatic motor cortex’

Located in the precentral gyrus of the frontal lobe of both hemispheres

The mapping of the CNS structures of the body is referred to as somatotopy.

23

The premotor cortex

Lies just anterior to the precentral gyrus in the frontal lobe and helps to plan movements

24

Broca’s area
(Motor cortex)

Is found anterior to the inferior region of the premotor area and is more prevelant in the left hemisphere.

It has a motor speech area and also becomes active just before speaking or when planning other voluntary motor activities.

25

The frontal eye field
(Motor cortex)

Is superior to broca’s area, located partly in and anterior to the premotor cortex.

It controls voluntary eye movements.

26

The central sulcus

separates the primary motor areas from the somatosensory areas

27

Sensory areas of the cerebrum

Interpret impulses such as skin sensations, which are picked up in the anterior portion of the parietal lobes.

Posterior occipital lobes affect vision

Temporal lobes affect hearing

Taste and smell receptors are located deeper within the cerebrum

Sensory fibers also cross similar to motor fibers

Additional sensory areas include the insular and occipital lobes

28

Primary Somatosensory Cortex
(Sensory cortex)

Lies in the post central gyrus of the parietal lobe. Just posterior to the primary motor cortex.

Its neurons receive input from the somatic sensory receptors of the skin.

It also receives input from position sense receptors in the joints, skeletal muscles and tendons.

29

Somatosensory association cortex
(Sensory cortex)

Is found just posterior to the primary somatosensory cortex, is interconnected and functions primarily to integrate temperature, pressure, and related information.

30

Primary visual (striate) cortex
(Sensory cortex)

Mostly buried in the ‘calcarine sulcus’ of the occipital lobe but also extends to the extreme posterior occipital tip.

It is the largest cortical sensory area, receiving visual information from the retinas of the eyes.