Summary Class notes - Neuropsychology

- Neuropsychology
- talamini
- 2020 - 2021
- Universiteit van Amsterdam
- Psychologie
192 Flashcards & Notes
1 Students
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Summary - Class notes - Neuropsychology

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  • What are the different parts of a neuron?
    • Cell body or soma; contains the metabolic machinery that maintains the neuron: common intracellular organelles.
    • dendrites; branching extensions of the neuron that receive inputs from other neurons.
    • spines; little knobs attached by small necks to the surface of the dendrites, where the dendrites receive inputs from other neurons
    • axon; single process that extends from the cell body. This structure represents the output side of the neuron.
    • synapse; specialized structure where two neurons come into close contact so that chemical or electrical signals can be passed from one cell to the next.
    • axon collaterals; some axons branch into multiple axon collaterals to pass on information to multiple neurons
    • myelin; fatty substance around the axons
    • nodes of ranvier; little gaps in the myelin
  • There are two types of transport of information, which are they and how are they handled?
    • Within a neuron; transferring information involves changes in the electrical state of the neuron as electrical currents flow through the volume of the neuron. 
    • Between neurons; information transfer occurs at synapses, typically mediated by chemical signal- ing molecules (neurotransmitters) but, in some cases, also by electrical signals.
  • Most neurons are both presynaptic and postsynaptic, what does this mean?
    • presynaptic when their axon makes a connection onto other neurons.
    • postsynaptic when other neurons make a connection onto their dendrites.
  • What is the resting membrane potential?
    • When the neuron is not actively signaling it is in it's resting state. 
    • In this state the membrane potential is −70 millivolts (mV). 
    • this means that the inside of a neuron is more negatively charged than the outside, with a difference of 70 mV
  • How does a resting potential, or any membrane potential arise?
    The two voltages, on the inside and outside of the cell depend on the concentrations of potassium, sodium, and chloride ions as well as on charged protein molecules both inside and outside of the cell.
  • There are two kinds of proteins on the neuronal membrane, which are they?
    • Ion channels; proteins with a pore through their centers, and they allow certain ions to flow down their concentration gradients. 
    • Ion pumps use energy to actively transport ions across the membrane against their concentration gradients
  • How do we call the extent to which a particular ion can cross the membrane through a given ion channel?
    The permeability
  • What does it mean that neurons are excitable?
    they can change the permeability of their membranes.
  • What causes the membrane of a neuron to have the ability to change its permeability, thus be able to become excitable?
    • Through gated ion channels; ion channels that are capable of changing their permeability for a particular ion.
    • They open or close based on changes in nearby transmembrane voltage, or as a response to chemical or physical stimuli.
  • How do we call ion channels that are unregulated, and hence always allow the associated ion to pass through?
    Non-gated ion channels
  • Na+ and Cl− concentrations are greater outside of the cell, and K+ concentrations are greater inside the cell. The difference between concentrations causes the membrane potential to exist, how come that ions don't flow out of the neuron down their concentration gradient ion concentrations inside and outside the cell are equal?
    • They do actually flow down their concentration gradient.
    • however, the ion pumps are constantly transporting ions up their concentration gradients
    • For each molecule of ATP that is hydrolyzed, the resulting energy is used to move three Na+ ions out of the cell and two K+ ions into the cell
  • There are a couple forces working with and against each other when it comes to the distribution of ions inside and outside the neuron, describe them.
    • The concentration gradient; The force of the ion concentration gradient wants to push ion from an area of high concentration to one of low concentration.
    • the electrical gradient; the membrane is more permeable to K+ than to Na+. The concentration gradient pushes K+ out of the cell, which causes the inside of the cell to become more and more negatively charged. As negative charge build on the inside of the neuron, K+ on the outside is attracted to go back in the cell.
    • The force of ion pumps; they transport ions back to where they belong, Na+ outside the cell, K+ into the cell.
  • What is electrochemical equilibrium?
    when the force of the concentration gradient pushing K+ out through the K+ channels is equal to the force of the electrical gradient driving K+ in. This causes the charge of - 70mV.
  • what is an excitatory postsynaptic potentials (EPSPs)?
    A graded potential that comes into the dendrite of the neuron causing ionic currents to flow in the volume of the cell body. These ionic currents causes the neuron to depolarize (become less negative) and make an action potential more likely.
  • What is an inhibitory postsynaptic potential (IPSP)?
    A graded potential that comes into the dendrite of the neuron causing ionic currents to flow in the volume of the cell body. These ionic currents causes the neuron to hyperpolarize (become more negative) and make an action potential less likely.
  • How do we call changes in membrane potential that vary in size?
    Graded membrane potentials

  • The small electrical current produced by the EPSP is passively conducted through the cytoplasm of the dendrite, cell body, and axon. Passive current conduction is called electrotonic conduction or decremental conduction. This is not enough to reach another neuron often. How does the neuron solve this problem?
    • Neurons generate action potentials
    • a rapid depolarization and repolarization of a small region of the membrane caused by the opening and closing of ion channels.
      • no loss in signal strength, because they continuously regenerate the signal.
  • How is an action potential able to regenerate itself?
    The action potential is able to regenerate itself due to the presence of voltage-gated ion channels located in the neuronal membrane
  • How do we call the place between the cell body and the axon, at the beginning of the axon?
    The axon hillock
  • Describe the process of an action potential.
    1. The current flow caused by the epsp's come together at the action hillock, the spike triggering zone.
    2. if the sum of the epsp's is big enough to cause a depolarization of the membrane big enough to go beyond it's treshold, −55 mV, an action potential is triggered.
    3. When the threshold is reached, voltage-gated Na+ channels open and Na+ flows rapidly into the neuron. This influx of positive ions further depolarizes the neuron, opening additional voltage-gated Na+ channels; thus, the neuron becomes even more depolarized.
    4. this self reinforcing cycle is called the Hodgkin–Huxley cycle.
    5. This huge depolarization causes the voltage- gated K+ channels open, allowing K+ to flow out of the neuron down its concentration gradient. This outward flow of positive ions begins to shift the membrane potential back toward its resting potential.
    6. The opening of the K+ channels outlasts the closing of the Na+ channels, causing a second repolarizing phase of the action potential; As a result, the membrane is temporarily hyperpolarized, meaning that the membrane potential is even farther from the threshold required for triggering an action poten- tial (e.g., around −80 mV).
    7. Hyperpolarization causes the K+ channels to close, resulting in the membrane potential gradually returning to its resting state.
    8. The large depolarization at one place of the neuron flows towards the next node of ranvier where the Na+ open up voltage-gated Na+ channels overthere. This causes the Hodgkin–Huxley cycle to start there and the proces from step 3 takes place further.
    9. the start of this process triggers an action potential to happen at the next node too. This is how an action potential moves.
  • What is the function of the hyperpolarization after an action potential?
    The neuron is in a refractory period where the voltage-gated Na+ channels are unable to open.
    • another action potential cannot be generated causing the neuron to over-fire.
    • the passive current that flows from the action potential can- not reopen the ion-gated channels that generated it. The result is that the action potential is propagated down the axon in one direction only.
  • What is the function of the myelin shed in the transport of an action potential?
    • makes the axon super-resistant to voltage loss allowing passive currents generated by the action potential to be shunted farther down the axon. Ap's don't have to regenerate that often.
      • regeneration of action potentials in myelinated axons need occur only at the nodes of Ranvier
  • How is the strength of a stimulus decided by action potentials?
    By the rate of firing of the neuron, one action potential is the same amplitude as any other, the strength of the action potential does not communicate anything about the strength of the stimulus.
  • how do we call the transfer of a signal from the axon terminal to the next cell?
    Synaptic transmission
  • synaptic transmission can either be chemical or electrical.
  • describe how chemical transmission works.
    • The arrival of the action potential at the axon terminal leads to the depolarization of the terminal membrane, causing voltage-gated Ca2+ channels to open.
    • The opening of these channels triggers small vesicles containing neurotransmitter to fuse with the membrane at the synapse and release the transmitter into the synaptic cleft. 
    • The transmitter diffuses across the cleft and, on reaching the postsynaptic membrane, binds with specific receptors embedded in the postsynaptic membrane.
    • Neurotransmitter binding induces a change in the receptor, which opens specific ion channels and results in an influx of ions leading to either depolarization (excitation) or hyperpolarization (inhibition) of the postsynaptic cell.
  • after binding with the postsynaptic membrane receptors, the remaining transmitter must be removed to prevent further excitatory or inhibitory signal transduction. How can remaining neurotransmitter be removed?
    • by active reuptake of the substance back into the presynaptic terminal.
    • by enzymatic breakdown of the transmitter in the synaptic cleft.
    • merely by diffusion of the neurotransmitter away from the region of the synapse or site of action.
  • describe how electrical transmission works.
    • the neuronal membranes are touching at specializations called gap junctions, and the cytoplasms of the two neurons are essentially continuous. 
    • These gap junction channels create pores connecting the cytoplasms of the two neurons 
    • As a result, the two neurons are isopotential (i.e., have the same electrical potential), meaning that electrical changes in one are reflected instantaneously in the other.
  • The nervous system is composed of the central nervous system (CNS), consisting of the brain and spinal cord, and the peripheral nervous system (PNS), consisting of the nerves (bundles of axons and glia) and ganglia (clumps of nerve cell bodies).
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Summary - Class notes - Neuropsychology

  • 1444600800 The History of Neuropsychology

  • What is neuropsychology?
    Understanding the relationship between brain and mind/behaviour 
  • What was Trepanation? (around 5000BC)
    Drilling a hole into the skull 
    It was thought that this would:
    - cure headaches
    - cure mental disorders (by allowing evil spirits to escape)
    = indicates importance of the brain 
  • What did Edwin Smith Papyrus do in around 3000BC in Ancient Egypt? What is the contradictory evidence for his findings?
    He recorded effects of head injury and references to hemiplegia (muscle weakness) - shows that brain & body linked 

    Contradictory evidence:
    Mummification in Ancient Egypt - the heart was preserved but the brain was thrown away. Suggests they thought the heart was sacred, not the brain.
  • What did Pythagorus propose in 582-507 BC?
    The brain hypothesis = the brain was the most important 
  • What did the Hippocrates propose in 460-370BC? What were they the first to find?
    That the brain controls everything e.g. feeling, emotion etc

    They found that paralysis occurred on the side opposite to the side of the brain lesion 
  • What did Plato propose (420-347)?
    - The mind and body are separate but connected - dualism 
    - The soul controls both mind and body

    He proposed that the soul is split into 3 elements:
    1. Appetite
    2. Reason (overrides the other 2 elements)
    3. Spirit 
    - these elements reside in the brain 
  • Who was Aristotle and what did he propose about the world? What hypothesis did he propose?
    Student of Plato

    He proposed that the world was split into 2 parts:
    1. Mind (psyche)
    2. Matter

    - non physical 
    - responsible for thought, perception, emotion, memory, imagination, pain, desire etc
    - Independent of body but works via heart to produce action

    Cardiac Hypothesis
    Heart = warm & active - it is the main organ of rational thought and the centre of the soul
    Brain = without blood - function is to cool the hot blood from the heart 
  • Why were the Greeks restricted in their investigation of the central nervous system?
    Dissection was sacrilegious - they couldn't prove/disprove their theories 
  • What did Galen (129-199/217) study?
    - The human body via gladiator wounds 
    - Dissected animals (e.g. sheep, pigs, monkeys) when they were alive = studied the living body 

    = detailed understanding of nervous and circulatory systems 
  • What did Galen find regarding the circulatory system? 
    - arteries contain blood
    - two systems of distribution: 
             1. Venous blood: created and pumped by the liver
             2. Arterial blood: created and pumped by the heart 
    - blood distributed to all organs 
  • What did Galen find in terms of the cerebellum and cerebrum?
    Cerebrum: controls sensation 
    Cerebellum: command muscles 
  • Who was Vesalius and what did he do?
    Most important man in the history of neuropsychology 

    Even though human dissection was banned by The Apostle's Creed (fear that mutilation would result in the inability of the body to be resurrected), he carried out dissection.

    He found:
    200+ errors with Galen's anatomy: 
    - demonstrated that Galen's view on circulation was incorrect - he found all blood vessels originate in the heart. The heart arteries and veins form one cycle
    - demonstrated that Galen's view on nerves was incorrect - he found that nerves stem from the brain and transmit sensation and motions commands 
    - he found that nerves are not hollow 
  • What did Willis do?
    He injected wax into nerve vessels
    - he found that there were 2 types of brain tissue - white and grey matter 

    'Circle of Willis' = vascular complex at the base of the brain

    He divided the brain into functional parts. He proposed that the brain structures itself influenced behaviour
    • cerebral gyri - control memory and will
    • corpus callosum - imagination 
    • corpus striatum - receives sensory information 
  • What did Galvini (1737-1798) study?
    Studied how neurons work - static electric charge applied to the muscle tissue of dead animal makes the muscle contract 
  • What did Gall propose (1758-1828)?
    Phrenology - personality was a result of the shape of the skull 
  • Phrenology = the beginnings of localisationism 
  • What did Flourens (1794-1867) find?
    Localisation - different parts of the brain have different functions 
    Cerebellum: coordinated movement
    Medulla: basic life functioning 
    Cerebral hemisphere: higher cognitive function 

    Tested on animals - if you have a lesion in the brain it will effect behaviour 

    - he suggested that the amount of tissue damage was important regarding lesions rather than the localisation of different functions. This is wrong, it is localisation that is important. Although the greater the mass of impaired tissue, the more disrupted the behaviour   
  • Why was Flourens unable to localise specific functions?
    - animal brains were too small
    - humans & animals are cognitively different e.g. speech
    - one area of the brain can effect multiple areas of the body
    - impairments weren't tested 
    - you need specific tests to observe specific changes in behaviour - maybe he didn't have the resources?
  • Who was Broca's famous patient? What did Broca find?

    Patient Tan - had a left hemisphere lesion 
    = good speech comprehension skills
    = impaired speech production skills (he could only say "Tan")

    Broca's area 
    Left frontal lobe
    Inferior frontal gyrus

    He found: Verbal abilities confined to the left hemisphere = lateralisation 
    = language is an example of lateralisation 
  • Who was Wernicke? (1848-1905) What did he find?
    Studied patients with: 
    - intact speech production 
    - deficit in speech comprehension
    (opposite of Broca's patients)

    Wernicke’s area
    Posterior section of superior
    Temporal gyrus
  • What did Wernicke add that we didn't already know from Broca's patient? What do they both show?
    Broca = example of single dissociation i.e. Tan could understand speech but not produce it (a fault here would be that maybe speech production is harder than comprehension) 
    Wernicke = example of double dissociation 

    = Speech production and comprehension must be separable since either can be damaged in isolation      
  • What did Brodmann (1909) discover?
    There are 52 distinct areas in the brain 
  • What did Hughlings Jackson find (1835-1911)?
    He observed the behaviour of brain damaged patients - found it was rare to lose a function entirely 
  • What did Von Monakow find?
    Diaschisis - a lesion to one part of the brain can have a knock on effect to another part of the brain - connecting areas can be dysfuctioning even if they look intact
  • What did Head (1926) discover?
    Functional pathways and representational systems
  • What did Lashley (1890-1958) discover?
    EquipotentialityEach part of the brain has the potential to support more than one function

     = A non-damaged area of the brain is capable of recovering the function of the damaged area.   
  • What did Luria (1902-1977) propose?
    The brain must encompass both localisation and equipotentiality.
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