Neuroscience Flashcards
Descartes
separated the mental processes of the mind from the physical processes of the brain - sees the mind as a separate entity existing outside the biology yet in control of our actions and thoughts
Neurons
fundamental building block of the nervous system
specialized for communication
organized into signalling pathways to communicate via synaptic transmission
Receptive Zone of the Neuron
receives signals from other neurons (dendrites)
- dendrites branch from the cell body
- reach out to other neurons and receive signals to be relayed to the dendritic branch of the cell body where some signals will be conveyed down the axon
Transmission Zone of the Neuron
pass on signals to other cells (axon and terminal ends)
The Axon
once a neuron receives a signal in the receptive zone, it is passed down a long fibre called the axon
- varies in length
- approaching the transmission zone at the end of the are the terminal ends
Terminal Ends
at the end of the transmission zone
reach out to make connection with the receptive zone of nearby neurons
Glial Cells
provide structural support, nourishment and insulation for the neuron
Cell Membrane
selectively permeable
separates the intracellular fluid from the extracellular fluid
Resting Potential
each of the ions contain either a positive or negative charge
the starting baseline for the differing concentrations of ions produces an electrical imbalance between the outside and the inside of the neurons
-controlled by 2 forces
–70mv inside the cell compared to the outside
Diffusion
the tendency for molecules to distribute themselves evenly in a medium
Electrostatic Force
the repulsion between ions with the same charge
Leaky Channel
allows potassium (+) to pass through the cell membrane (at all times) out of the neuron as they are drawn to the negatively charged protein (-) molecules
Voltage Gated Channels
stays closed during resting potential
Dorsal
refers to the back side of the axis
- to the top at level of the head
- to the back at the level of the spinal chord
Ventral
means to the front or to the belly
Rostral
top of the axis
Caudal
bottom of the axis
Medial
central/midline (in the brain)
Lateral
towards the outside (of the brain)
Lesion Studies
case studies of accidental brain injury - link anatomy with cognitive and behavioural deficits that occur
Phinneus Gage
the victim of a tragic railway accident - iron rod went completely through left cheek and top of skull
- survived and almost recovered completely
- major behavioural change - went from optimistic and lively to selfish and profane, erratic and unreliable
Advantages of Lesion Studies
a direct measure to a brain structure’s function
Disadvantages of Lesion Studies
hard to selectively target particular regions and draw conclusions
-can be overcome by studying legions in animals
Ablation Studies
researcher destroys/removes/inactivates a certain region of the brain and observes result in behaviour
Penfeild
used the stimulation and single cell recording technique - electrically stimulate an area and observe result to build an anatomical map
-Montreal Procedure
CT Scans
take a series of X-ray slices of the brain and piece them together to produce a picture
- helpful in diagnosing brain injuries
- limited by low resolution (can’t examine fine brain anatomy)
MRI
powerful magnetic fields are generated and align the hydrogen atoms in the brain
-can localize tissue when aligned
Structural Neuroimaging
used for a larger scale
- CT Scans
- MRIs
Functional Neuroimaging
PET Scans
fMRIs
EEG
Position Emission Tomography (PET)
how brain function relates to cognitive tasks
- a radioactive tracer is injected into the blood stream
- detects it in brain’s metabolic processes
- more active brain areas will use more metabolic processes
- relative patterns of activity can be constructed
- limited because it requires radioactive tracer to be injected which is invasive
Functional Magnetic Resonance Image (fMRI)
can produce a relatively clear image of a brain;s activity without radioactive tracers
measures the blood-oxygen dependent signal and uses the same principles as the MRI
measures the relative use of oxygen throughout the brain
more active = more metabolic resources
Limited because it only produces a rough image of brain activity and timing is off
Electroencephalogram (EEG)
cap of sensitive electrodes record electrical activity in the brain through the scalp
rough image of overall activity from populations of neurons
can be more informative - averaging out signals across many repeated trials, noise can be balanced out and the consistent effect on the read out by the specific repeated stimulus during ERP remains
-ERP can be hard to interpret but certain markers can signify different types of neural processing
Hindbrain
region at the base of the brain that connect the brain the the spinal cord
- medulla, pons, reticular formation, cerebellum
- primarily involved in the regulation of vital bodily functions
Medulla
most caudal part; lies directly above spinal cord
-breathing, digestion, regulation of heart rate
Pons
rostral to medulla
- relays info about movement from the cerebral hemispheres to the cerebellum
- contains nuclei that are generally part of the reticular formation
- processes some auditory info and thought to be involved in emotional processing
Reticular Formation
a set of interconnected nuclei found throughout the hindbrain (excluding cerebellum)
Ascending Reticular Formation
arousal and motivation, and part of a large network responsible for conscious experience
- circadian rhythms
- damage leads to loss in brain function (or even coma)
Descending Reticular Formation
posture, equilibrium and motor movement
Cerebellum
coordinates all movement
- motor commands pass through and signal muscles to contract
- sensory signals return to the cerebellum for immediate error correction
Midbrain
involved in processing visual and auditory information
- Tectum, Tegmentum
- structures involved in perception, arousal and motor control
Tectum
dorsal portion of midbrain - perception and action
-superior and inferior colliculus
Superior Colliculus
eye movements and visual reflexes
Inferior Colliculus
auditory integration
Tegmentum
includes nuclei in reticular formation, red nucleus, substantia nigra
Red Nucleus
important in the regulation and production of movement
- projects directly to the cerebellum and spinal cord
- plays a lesser role in humans than in less advanced vertebrates
- serves primarily as a relay station for info for higher motor areas to/from cerebellum and spinal chord
- controls many motor behaviours in developing infants
Substantia Nigra
interconnected region with projections into a variety of forebrain regions
- motor planning, learning, reward seeking
- contains neurons that produce the neurotransmitter ‘dopamine’ (released during rewarding behaviours)
- damage can lead to motor tremor (Parkinson’s)
Forebrain
uppermost and largest region of the brain composed of several structures, the most prominent being the cerebral cortex
- emotion, memory, perception, thought
- limbic and cortex
Hypothalamus
directing stress responses, regulating energy metabolism (feeding, digestion, metabolic rates, regulating reproduction)
- Fight, Flight, Feeding and Fucking
- exhibits these regulatory roles through neurons that are capable of producing a variety of regulatory hormones
- via pituitary gland and key subcortical structures
Pituitary Gland
Inferior to hypothalamus; “master gland” of the endocrine system
- regulates and releases a variety of vital hormones
- anterior and posterior
Anterior Pituitary Gland
receives signals from the brain via hypothalamus and releases stimulating hormones to regulate other important endocrine glands
Posterior Pituitary Gland
extension fo hypothalamus, releases oxytocin and vasopressin
Oxytocin
involved in physiological functions such as lactation and uterine contractions (and bonding, love and trust)
Vasopressin
blood hormone, regulates levels of thirst by interacting with kidneys to regulate glucose levels
Thalamus
“relay station” to cerebral cortex
- axons from every sensory modality (except olfaction) synapse here
- processes and relays information selectively to areas of the cerebral cortex
Amygdala
below surface of each temporal lobe, receives sensory info from thalamus, contains nuclei that decode emotions (esp. threatening)
-damage leads to deficits of classically conditioned fear responses, PTSD
Hippocampus
temporal lobe; memory formation
- related to your ability to hold short-term memories and transferring short term to long term
- connected to amygdala - strong emotions connected/triggered by particular memories
- ability to navigate through world - contains spatial map
- contains adult neurogenesis (related to memories)
- Damage leads to alzheimer’s, amnesia
Interconnectivity
functions are more complex and less well understood than suggested here
-each region is intimately connected and their boundaries are poorly defined
Cerebral Cortex
ultimate control and information-processing center
- evolutionarily the newest part of the brain
- 4 Lobes: Frontal, Occipital, Parietal, Temporal
Gyri and Sulci
ridges and indents; increase surface area
Fissures
large sulci that subdivides the cortex
Occipital Lobe
basic visual processing
- more complex processing of visual info begins
- Damage: functionally blind
Temporal Lobe
below syvian fissure
- higher visual processing (form and identity)
- primary auditory cortex: basic auditory processing
- memory and language
Parietal Lobe
anterior to occipital lobe, above syvian fissure, rostral to central sulcus
- somatosensory processing (touching)
- spatial representations (location and movement of visual objects)
- spatial representation of the world - guiding eye and body movements, visual attention
- Damage: somatosensory deficits, loss of sensation, deficits in orienting, attention, coordination, complete loss of attention
Frontal Lobe
most complex, rostral end
- motor processing
- decision making
- language, strategy formation, inhibition, manipulation of items in short term memory
- Damage: spontaneous inappropriate behaviour, loss of motivation, decision making and learning deficits, difficulty in understanding language, motor deficits
Asymmetry
the idea that there are functions that are specialized to just one side of the brain
Double Dissociation
when damage in a particular brain area, but not areas, produces a specific behavioured deficit
Broca’s Area
vital for motor production and speech (left frontal lobe)
Wernicke’s Area
vital for the comprehension of speech (left temporal region)
Corpus Callosum
thick bundle of axons that allow the 2 hemispheres to communicate
-passes through the centre
Split-Brain Syndrome
one side of the brain has no idea what the other has received
-most everyday activities are unaffected because most stimuli arrive on both sides of the body simultaneously
Threshold
under the influence of the nearby neuron and random ion flow, sometimes a large enough change in the resting charge will occur to reach a certain level
–50mv triggers action potential
Action Potential (Step-byStep)
The Fundamental unit of communication for neurons
-50mv threshold is reached
sodium channels open
diffusion causes (+) sodium to rush into neuron
charge on inside becomes more +’ve than outside
electrostatic force pushes (+) potassium out through leaky channel
+‘ve charge builds up inside
voltage gated potassium channels open
more (+) potassium ions leave
inside peaks at +40mv and sodium channels close
sodium stops entering cell, but (+)potassium still rushes out
+‘ve charge inside decreases rapidly and overshoots -70mv resting potential
Voltage gated potassium channels close
Enters short refractory period, where it cannot shoot another action potential until it settles and recovers
Sodium/Potassium Pump
removes sodium from cell and replaces potassium
- active throughout and after action potential
- expels 3 sodium ions and replaces them with 2 potassium
- moves slowly and utilizes exteroize energy
- important for maintaining ion balance
Myelin Sheath
fatty, insulating tissue made up of glial cells that coats many axons to make communication more efficient
- oligodendrocytes in the CNS
- schwann cells in the PNS
Saltatory Conduction
a process whereby the action potential jumps across the myelin sheath when it reaches it
Nodes of Ranvier
open regions on the axon between myelin segments
-re-strengthens the signal after it was weakened by the myelin sheath through ion channel cascades
Frequency and Pattern
encodes different types of messages
-a strong signal will lead to many sequential action potentials; a weak signal will lead to fewer in the same amount of time
Synapse
the area of connection between the terminal end of a neuron and the receptive zone of another
-not a direct physical connection
Neurotransmitters
chemicals in the terminal ends
stored in vesicles and move toward cell membrane as action potential move toward terminal ends
-vesicle fuses to cell wall and they are released into extracellular fluid
-many different types and each have a different function
Synaptic Cleft
space between two neurons
- neurotransmitters float freely
- other molecules exist here and can have direct effects
Receptors
funf along the membrance of the post-synaptic neuron and receive specific neurotransmitters
-neurotransmitters bind to specified receptor to continue signal transmission by a number of possible actions
Excitatory Post-Synaptic Potential (EPSP)
neurotransmitters modify nearby ion channels
- Na+ channels open and Na+ ions flow in
- increases positivity and moves charge closer to the -50mv threshold
- -> depolarizes
- a single one is not enough to reach threshold, so a number of them have to occur
Temporal Summation
EPSPs occurring one after the other
Spatial Summation
EPSPs occurring all at once - simultaneous from multiple pre-synaptic connections
Inhibitory Post-Synaptic Potential (IPSP)
inhibits transmission of a signal
- Cl- channels open and Cl- enters the cell
- increases negativity adn moves charge away from the threshold
- ->hyperpolarizes
Neurogenesis
birth of neurons
- begins at 18 days - outer layer at back of embryo thickens and forms a plate
- edges of plate curl upwards and fuse together by day 21
- neural tube is completely closed by day 28 and will eventually become the CNS
Stages of Neural Development
Neurogenesis
Migration
Differentiation
Maturation
Neural Tube
ventricular zone lies within and is lined with founder cells (begin dividing at day 28)
- Day 28-42: cel division is symmetrical
- Day 42-125: asymmetrical
- cells migrate outwards from the ventricular zone
Migration
the travelling of neurons to their correct location
- begins immediately after first neuron is born (day 42) and continues 6 weeks after that
- neurons are usually produced before glial cells
Radial Glial Cells
produces before neurons and are fibres that extend outward from the ventricular zone and provide scaffolding and end up at outer layer cortex
- used by neurons to migrate out
- grow as the brain increases in thickness so that they always end up at outermost surface
- later neurons travel a longer distance
Differentiation
transformation of unspecified cells into specializes cell types that differ in structure and function
- following migration, the neuron tkes on a specific function that is partly determined by genetics
- by the location in the ventricular zone where a founder cell originated
- sensitive to the input a neuron receives from its connection with other neurons (environmental input also plays an important role)
Plasticity
making connections with other neurons is a matter of survival because more neurons are produced than needed.
neurons that fail to make connections are pruned away
this increases the brains processing efficiency and retains only the useful connections
Maturation
growth of neurons by establishing connections with other neurons
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