Lecture 1
The brain is the tissue found within the skull. The outer layer is the cortex. It
has two hemispheres that are connected by the corpus callosum. The remaining
“tube” underlying the cortex is the brainstem, connected to the spinal cord, that
descends down the back within the vertebral column. The cortex of each
hemisphere forms four lobes :
Occipital visual information processing
Parietal somatosensory information, and visuospatial
Frontal motor
Temporal auditory cortex, speech
o Cortex: surface
o Subcortex: under the cortex
This is important to know because patients will show a different clinical picture
based on the location
The brain also has 18 long fiber systems. Further the distance between the brain
areas who communicate, the more complex the function is.
,The outer layer is a triple layered set of membranes, the meninges. We find the
dura mater, a tough double layer of tissue enclosing the brain. The inner pia
mater is a moderately tough tissue that clings to the brain’s surface. Between the
dura and the pia we find the middle layer, arachnoid.
The white matter is the tissue through which messages pass between different
areas of gray matter. In simple terms the white matter facilitates information
transfer (pathways, connections between brain areas) and the grey matter
information processing (brain regions). The white matter is white because of the
myelin that surrounds the axons. Myelin is crucial for signal transmission.
There are also unmyelinated pathways (the ones that signal painfulness).
Fast connections mean a better working white matter whereas slower
connections a low working one. White matter is affected by aging, so its quality
decreases with time.
most white matter is subcortical
During a blow to the head the blood vessels of the white matter tend to stretch
leading to a lesion on the axons. Because of this there is less blood supplied to
the brain, which causes a person to lose consciousness.
, Picture shows small/ moderate and
severe damage to the white matter. If the damage disrupts the white and grey
matter connection, brain functions will be lost.
To better orient ourselves in the brain we use these terminologies:
Structures close to one another are proximal, those farm from another are distal.
Movement toward a brain structure is afferent, whereas movement away from it
is efferent.
Afferent fibers enter the posterior spinal cord to bring information
in from the body’s sensory receptors. These form a strand of
entering fibers referred to as the posterior root. Efferent fibers exit
the anterior spinal cord to carry information from the spinal cord
out to the muscles, forming a similar strand, an anterior root.
One way to test this is by knocking the knee, which stimulates flexion reflexes.
, Sympathetic nervous system is for flight
of fight meanwhile parasympathetic is for
rest and digest
Persons who no longer have control over their legs due a cut(or damage) below
the cervical segments are called paraplegic. If the cut is higher, extending into
the cervical segments, they are unable to use arms as well, they are so called
quadriplegic.
The brain has three major arteries that supply oxygen and glucose:
o the anterior cerebral artery (irrigates the medial and dorsal parts of the
cortex)
o the middle cerebral artery ( irrigates the lateral surface of the cortex and
the one usually affected during 70% of stroke cases)
o the posterior cerebral artery (irrigates its ventral and posterior surfaces)
The arm/hand/face are innervated by brain regions that are located within the
area of the middle cerebral artery. The leg area receives blood supply from the
anterior cerebral artery.
If a blood clot forms in a cerebral artery it will cause a stroke. Some people
have connections between different arteries, so subsequent to a clot, other
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