the human brain Flashcards
what are the two main classes of cells in the nervous system?
. neurons
. glial cells
what are neurons?
. generate electrical signals
. they have a cell body ( soma)
. they have dendrites coming out of the cell body
. they have an axon
. end of the axon there is axon terminal
. in the axon terminal synapses are located
what are glial cells?
. they have supporting roles
.e.g. oligodendrocytes which are responsible for myelinating axons within the CNS
e.g. astrocytes - wrap around capillaries in the CNS , to form part of the brain;blood barrier
what is the function of myelin ?
. to increase the speed and reliability of impulse conduction
what are the two main components of the CNS?
. CNS- brain and spinal cord
. PNS- sensory and motor axons
what does the brain do for us?
. acquiring knowledge . storing information . controlling motor behaviour e.g. elemental movements(e.g. respiration, heart rate) . complex voluntary/willed action . language and communication
what is the gross brain structure?
. bilaterally symmetrical
- right and left hemispheres
. each with 3 major divisions
- cerebrum ( largest )
- cerebellum
- brainstem ( smallest )
what are the two main components of the cerebrum ?
1. telencephalon ( forebrain ) . cerebral cortex . basal ganglia 2. diencephalon ( between brain ) . thalamus . hypothalamus . epithalamus
what is the largest part of the telencephalon?
. cerebral cortex: which is responsible for conscious sensation/perception, voluntary movements and higher cognitive ( e.g. language) functions
what is the cerebral cortex?
the largest part of the telencephalon
which is responsible for conscious sensation/perception, voluntary movements and higher cognitive ( e.g. language) functions
what is the basal ganglia?
. located in the telencephalon
. responsible for movement planning and control
what is the thalamus?
. located in the diencephalon
. largest division in the diencephalon
. contains various nuclei which are connected to cerebral cortex
what is the hypothalamus?
. located in the diencephalon
. contains various nuclei for regulating appetites and endocrine function ( via connections with pituitary gland)
what is the epithalamus?
. located in the diencephalon
. contains the pineal gland which secretes melatonin and regulates the circadian rhythms
what is the brain made of?
. made of gray matter
. made of white matter
what is gray matter?
. contains the cell bodies and dendrites of neurons along with synaptic inputs received from the terminal axons of other neurons: it is a site of information processing
how are neuron cell bodies arranged?
- layers or sheets, as in the cerebral cortex
2. groups/clusters( nuclei ) as in the thalamus and basal ganglia
what is white matter?
. contsind axons of neurons and their associated myelin sheaths formed by oligodendrocytes
what is the white matter white?
. myelin sheath is the cell membrane of the oligodendrocytes wrapped around the segments of the CNS axons
. its mainly white
what is the main function of white matter?
. routes for direct, long-range connections or ‘projections’ between neurons in different gray matter regions
. information transfer
what are the main white matter pathway in the brain?
- corpus callosum :
carries axons between neuron cell bodies in the right and left cortical hemispheres - internal capsule :
carries axons between neuron cell bodies in different thalamic nuclei to different parts of the cerebral cortex
why is the cerebral cortex folded?
. to pack its large surface area into the skull
what do the cerebral cortex folds consist of?
. ridges= gyrus
. furrows= sulcus
how many lobes does the cerebral cortex contain?
. cerebral cortex is divided into 4 major lobes
what are the 4 lobes in the cerebral cortex?
. frontal lobe= motor/movement . parietal lobe= somatic sensation e.g. touch, temperature, pain, joint sense . temporal lobe= auditory/hearing . occipital lobe= vision
what does the central sulcus divide?
. the central sulcus divides 2 lobes
. frontal lobe
. parietal lobe
what does the lateral sulcus divide?
the lateral sulcus divides the frontal and parietal lobe from the temporal lobe
what is the main function of frontal lobe?
. controlling voluntary movements
what is the main function of parietal lobe?
. controlling somatic sensation
what is the main function of temporal lobe?
controlling hearing
what is the main function of the occipital lobe?
controlling vision
what are the 2 methods for visualizing the living brain?
- X-ray computed tomography (CT)
2. magnetic resonance imaging (MRI)
what is the principle behind an X-ray?
. person lies in a scanner
. x-ray beam is fired repeatedly into their head at different angles
. x- ray passes through the persons head with different attenuations
. hard tissue ( e.g. bone) doesn’t allow x-ray to pass through so appear as white
. soft tissue ( e.g. water) appear as black in x-ray images
. compile as sequential slices
. useful for looking at gross pathologies(e.g. stroke and tumours )
what is the principle of MRI?
. maps hydrogen nuclei/water concentration
. person lies in a scanner
. also compile sequential slices of head and to form images
. forms better differentiation between gray and white matter
how does MRI soft tissue differentiation work?
. radio frequency pulses applied form the magnetic field around the head cause the odd proton number in hydrogen and water to temporarily align with the external source and resonate with particular time (T) constants
.T1= all aligned: white matter lighter than grey matter .T2= lost alignment: white matter darker than grey matter
how do we know about the different functions of different brain regions?
- clinical neurology and structural brain imaging:
. examining surviving patients ( with stroke, trauma, diseases)
which results in selective deficits resulting from localized brain damage - functional brain imaging
what is functional brain imaging?
. examining healthy, neurologically-intact volunteers
. the scanner will be looking for localized increases in brain activity while they perform a specific task in the brain scanner
. the scanner is looking for regions in the brain which the oxygen or glucose consumption has gone up which is indicative that part of the brain is neurally active
what are 2 methods for identifying regions of increased brain activity , mapped onto structural scans?
- positron emission tomography (PET)
2. functional magnetic resonance (fMRI)
what is the principle behind PET and fMRI?
. is to look at oxygen , with high levels of oxygen implying an area of high brain activity
what PET?
. inject isotope into an artery of px
. when it reaches a region of the brain which is using a lot of oxygen , the positron annihilate on collisions with electrons producing 2 gamma rays which travel in opposite directions to detectors in scanner around head
. method for localizing changes in cerebral blood flow
what fMRI?
. non-invasive : based on differences in resonance of haemoglobin versus deoxy-haemoglobin molecules when exposed to a strong magnetic field provided by the scanner
. method for localizing blood oxygenation level dependent changes
how to find what part of the human cerebral cortex was associated with visual function ?
- put a healthy person into a scanner
. have eyes open and look at something in scanner
. the scanner will record neural activity throughout their whole brain - in next scan which is the control , the subject will close their eyes
. record all brain activity - difference between test minus control = brain regions specifically activated by the stimulus
eye closed brain activity minus from eyes open brain activity gives you the regions of the brain that are active when you’re using visual part of cortex
