Landmarks of the brain Flashcards
what is the circle of willis
circulatory anastomosis that supplies oxygenated blood to the brain and surrounding structures
where is the circle of willis
inferior part of the brain
the divisions of the brain
forebrain, midbrain and hindbrain
what forms the forebrain
- telencephalon - cerebral hemispheres (cortex, basal ganglia and limbic system)
- diencephalon (thalamus and hypothalamus)
what forms the hindbrain
- pons (cerebellum)
- medulla
what is the central sulcus
a fissure that divides the frontal and parietal lobes
- it is located under the parietal
what is the corpus callosum
bundle of nerve fibres which connects the right and left brain hemispheres made up of white matter composed of -genu -rostrum -trunk (body) -splenium
what are the gyrus
folds in the brain separated by sulci
how many layers and distinct areas does the cortex have
6 layers and 52 distinct regions (Brodmann areas)
what is the cerebrum
primary motor cortex located in the pre central gyrus anterior to central sulcus
what does the cerebrum control
it controls voluntary movement - mainly of hands and face
how does the cerebrum control movement of the body
by working in conjunction with motor planning areas of the cerebral cortex
function of the motor cortex
voluntary movements
function of the premotor area
control of trunk, anticipatory postural adjustments
function of the supplementary motor area
initiation of movement, orientation planning, bimanual sequential movements
function of Broca’s area
motor control of speech (usually left cerebrum)
function of area analagous to Broca’s area on opposite side
planning non-verbal communication
what is the consequence of damage to motor planning areas
apraxia - unable to perform movements or sequence of movements despite intact muscles
broca’s aphasia - impaired speaking and writing
how does visual information travel to the primary visual cortex
from retina via thalamus
what does the primary visual cortex discriminate
shape, size, location and texture of objects
what information does the secondary visual cortex analyse
colour and motion
what is the optic chiasm
X-shaped structure formed by the crossing of the optic nerves in the brain.
Nerve fibres from half of each retina cross over to the opposite side of the brain.
function of broca’s area
controls movement involved in speech (face and tongue of adjacent motor cortex)
what do lesions in the broca’s area involve
difficulty with verbal expression - speech is slow laboured and telegraphic in style
where is wernicke’s area
superior temporal gyrus on left hemisphere
what is the function of wernicke’s area
understanding of spoken words
what do lesions in wernicke’s area involve
receptive aphasia (difficulty in understanding speech of others) and lose ability to monitor their conversation
links of cerebrum (prefrontal cortex) with other areas
prefrontal cortex has links with all parts of neocortex (except primary motor & sensory) and with contralateral side via corpus callosum
what is the cerebrum involved in
highest brain functions (executive function)
- abstract thought, planning
- decision making
- anticipating outcomes, judgement
- social behaviour
what are the schizophrenia negative symptoms associated to
hypofrontality
how does the corpus callosum differs in normal people from autistic people
changes in size of corpus callosum in autistic people
what do lesions of vermis (tumours in children medulloblastoma) consist in
inability to stand upright, nystagmus, impaired eye scanning
characteristics of disease of anterior lobe
associated with chronic alcoholism
staggering drunken gait when sober
characteristics of disease of the neocerebellar cortex superior cerebellar peduncle
incoordination of voluntary movements (particularly of upper limb)
action tremor
function of basal ganglia
important subcortical system which regulates voluntary movement
composition of basal ganglia
striatum (caudate nucleus and putamen)
pallidum (internal and external globus pallidus)
sub thalamic nucleus
what do the neurons linking the substantia nigra and the striatum (nigrostriatal pathway) use
dopamine
during motor activity
symptoms of parkinson’s disease
degeneration of nigrostriatal dopamine neurons
what is the limbic system involved in
emotions (fear, anxiety, aggression, pleasure), memory, appetite, sleep
composition of limbic system
- cingulate gyrus
- fornix
- thalamus
- stria terminalis
- septal nuclei (social behaviour)
- amygdala (fear and anxiety)
- hippocampus (memory, mood)
- hypothalamus (stress, sleep, appetite)
what is the hippocampus involved in
learning and memory
also modulates mood and response to stress
what does the limbic do
converts short-term memory to long-term memory
what do lesions in the hippocampus result in
memory impairments
where is the amygdala located
in temporal lobe anterior to the hippocampus
function of the amygdala
mediates feelings of fear, anxiety and social learning (interprets facial expression, body language, social signals)
what do lesions in the amygdala result in
fearless behaviour, increased risk-taking and poor social judgement
what is associated with heightened activation of amygdala
PTSD and other anxiety disorders
how is the amygdala in schizophrenic patients
smaller
how is the amygdala in autistic children
larger than normal –> social impairments
where is the hypothalamus located
anterior/inferior to thalamus, floor of 3rd ventricle
function of hypothalamus
regulates appetite, body temperature, reproductive functions, neuroendocrine stress response, emotionality
the reward pathway
neuron projection from ventral tegmental area to ventral striatum (nucleus accumbens )
why is it necessary the activation of the reward pathway
to experience pleasure
what is addiction
loss of behavioural control over drug-taking
stimulates reward pathway
