L4 Flashcards
what is cerebral white matter responsible for
communication between cerebral area and between the cerebral cortex and lower CNS centres
what does white matter mostly consist of
myelinated axons bundled into large tracts
what are projection tracts
extend vertically from the brain to the spinal cord forming the internal capsule
can see in a caronal section inferiorly close to the brainstem
what are commissural tracts
they cross from one hemisphere to the other
what is the biggest commissural tract
the corpus collosum
how many axons are in the corpus callosum
300 million
the corpus collosum is so large that there are 4 parts of it. what are these called
the splenium, body, genu and rostrum
what is the splenium
it is the posterior part of the corpus callosum which has tracts coming from the temporal and occipital lobes
tracts from the body of the corpus collosum come from……
the parietal lobe and parts of the frontal lobe (frontal lobe - the anterior part)
what does genu mean
it mens bend which is why it is the bent part of the corpus collosum
where do tracts from the genu come from
anterior parts of the frontal lobe
how could someone end up with split brain
a corpus callosum transection
or
if you are born without one
what is a a corpus callosum transection
it is a form of treatment in patients with severe
and disabling epilepsy
it prevents the spread of epileptic discharge
from one hemisphere to the other
what is it called when you are born without a corpus collosum
acallosal
what are the symptoms of having split brain
there are no obvious changes in intellect and behaviour but they may have problems with certain tasks
e.g. object in right hand with eyes closed, can be
named; object in left hand can not be named
what is the anterior commissure
Includes axons that
connect the middle & inferior temporal gyri of
the two sides of the brain
it is like a smaller version of the corpus collosum therefore it is another example of a commissural tract
what are association fibers
they connect lobes and gyri within the hemisphere
ganglia means….
more than one
what is the corpus striatum made up of
the caudate nucleus (looks like a commor) and the lentiform nucleus
what is the lentiform nucleus made up of
the putamen (pod) and the globus pallidus (pale globe)
what is the corpus striatum functionally associated with
the subthalamic nuclei and the substantia naira
what is the striatum made up of
putamen and the caudate nucleus
what is the pallidum made up of
globus pallidus
the external (GPe) & internal (GPi) divisions
what is the basal ganglia made up of
corpus striatum, subthalamic nuclei and the substantia nigra
describe what the basal ganglia looks like in the brain
a sleeping lizard. the basal ganglia has a head, body and tail
the head is the lentiform nucleus
the body and tail is caudate nucleus
what structure sits at the end of the tail of the basal ganglia
the amygdaloid nucleus/amygdala
there is one on each side of the brain
what is the the amygdaloid nucleus
the limbic system
what is the internal capsule
projection fibers to and from the spinal cord which run deep into the lentiform nucleus
where does the posterior limb of the internal capsule lie between
between the lentiform nucleus and the thalamus
where does the anterior limb of the internal capsule lie between
between the lentiform and the caudate nucleus
what structures make up the internal capsule
the anterior limb, the genu and the posterior limb
what 2 structures have major connections to the basal ganglia
the substantia nigra and the motor cortex
how does the basal ganglia play a role in movement
the BG receives input from the substantia nigra and the motor cortex and then sends signals back to them
however the BG don’t have direct access to the motor neurons in the cerebral cortex so it has to make the connection through the thalamus.
Hence have cortical-basal ganglia-thalamic-cortical loop
in motor control the basal ganglia’s function is too…….
inhibit unnecessary movements and act as a break so that only have movement and exquisite movement when we need it
it also plays a role in regulating attention and cognition (plays a role in memory)
how is the break that the basal ganglia puts on movement removed
brake is released by input form the cerebral cortex and the substantia nigra to start movement
how does input form the cerebral cortex and the substantia nigra take the brake off movement
the basal ganglia’s inhibitory neurons are tonically active which means that they are inhibiting the excitatory neurons
this break is removed by excitatory neurons in the cortex which activate inhibitory neurons which inhibit the inhibitory neurons (the brake) which means that the excitatory neurons are free to fire
what causes Parkinson’s disease
substantia nigra dopamine neuron degeneration
what are the symptoms of Parkinson’s disease
– rigidity – tremor (at rest) – difficulty initiating movement – postural instability – shuffling gait – stiff facial expression (mask-like face)
what is the treatment for Parkinson’s disease
replacement of dopamine
stem cell therapy
deep brain stimulation
what paired structures are found in the diencephalon
thalamus, hypothalamus and epithalamus
what % of the diencephalon does that thalamus take up
80%
this is the dominant structure of the diencephalon because of its structure not its function
the thalamus forms what part of the 3rd ventricle
superior lateral walls
how many nuclei are there in the thalamus
about 12
what connects the 2 thalamus together
the interthalamic adhesion (also called the intermediate mass)
what are the key roles of the thalamus
relaying sensation, motor activities, cortical arousal, learning and memory
why is the thalamus divided into several groups
Each collection sends information up to different parts of the cortex
the thalamus is known as……
the gateway to the cerebral cortex
where is the hypothalamus located
below the thalamus in the hypothalamic sulcus
it is superior to the brainstem and extends from the optic chiasm
the hypothalamus forms what part of the 3rd ventricle
the inferolateral wall
why if you were to have a tumor of the hypothalamus could you end up with a visual impairment
because of the hypothalamuses proximity to the optic chiasm
what are the main homeostatic roles of the hypothalamus
Autonomic control centre (eg. respiration)
Centre for emotional response (limbic system)
Body temperature regulation (thermosensitive neurons)
Regulation of food intake (appetite & satiety centres)
Regulation of water balance and thirst (thirst centre)
Regulation of sleep-wake cycles (with pineal gland)
Control of endocrine system functioning
(eg. ovaries, testes to produce egg, sperm)
what are the symptoms of damage to the hypothalamus
various neuroendocrine disturbances
autonomic dysfunction (respiratory, cardiovascular and gastrointestinal systems)
disturbances in temperature regulation,
water balance, sexual behavior and
food intake
changes the level of consciousness, sleepwake cycle and emotional behavior
what most commonly damages the hypothalamus
tumors
a early symptom of this is visual defects because of encroaching on the optic chiasm or optic tract
what is the epithalamus
it is a small cone shaped body that is attached to the roof of the 3rd ventricle
what can be found in the epithalamus
it contains Ca2+ salts such as pineal sand (in adults) and radiopaque)
This means that you can see these in an xray and it is used as a landmark to see where you are in the brain
what is one role for the epithalamus
it generates melatonin which is the sleep inducing signal. this peaks at night
note that you only have one pineal gland but there are other features of the epithalamus that are bilateral
