NEUR1020 W5

• What is a neuron?

  Nerve cells that send messages through the body
• What are the different parts in a neuron?

  Cell body, dendrites, axon, axon terminals
• What is the cell body?

  Contains nucleus and all structure necessary for cell functioning
• What are dendrites?

  Receives signals from the input zone from many other neurons or sensory organs
• What are axons?

  Sends signals, output from axon hillock at cell body to the axon terminals. Axons are wrapped in myelin sheath for efficient transmission of signals
• What are axon terminals?

  End of the neuron and it forms synapses with other neurons to secrete neurotransmitters to send signals
• What are glial cells?

  Supporting cells for neurons, and is crucial for brain function
• What are the 3 types of glial cells?

  Oligodendrocytes (fatty substance producing myelin sheath).

  Astrocytes (supplies nutrients from blood to neurons, maintaining "blood-brain barrier").

  Microglia (Brain's immune system and cleans up toxic substances).
• What is the multiple sclerosis disorder?

  Involves the loss of myelin, hence disrupting efficient neural communication throughout the body
• What is a synapse?


  The join between an axon terminal of one neuron to dendrites of another neuron for transmitting signals
• What is the difference between pre-synaptic and post-synaptic?

  Pre-synaptic goes from cell body to axon terminal (before synapse), while post-synaptic goes from dendrite to cell body (after synapse)
• What are neuron signals?

  Action potential, which are electrical signal pulses travelling along the axon. They are a fixed size that is either on or off
• What percentage of the brain is water?

  70%
• What is the cell membrane wall of the cell body of a neuron?

  Forms barrier between extra-cellular and intra-cellular fluid from a lipid bilayer
• Why is there different concentrations inside and outside a cell across the membrane?

  Because it gives difference in electrical charge potential
• Are there more positive ions (Na+ and K+) inside or outside a neuron?

  More outside
• What is membrane potential?

  Difference in the electrical charge (voltage) between inside and outside the cell
• What is resting potential?

  At rest, more positive ions are outside than inside, giving an overall negative potential (-70mV)
• What are the 3 important types of ion channels?

  Sodium potation pump, voltage-dependent ion channels, ligand-gated ion channels
• What is the sodium potassium pump for?

  Actively pumps Na+ and K+ across membranes, but overall pumps positive charge out of the cell to maintain the negative resting membrane potential (3 Na+ in, 2 K+ out). This uses 70% of brain energy and 25% of total body energy
• What is action potential?


  Transmission of electrical signal along the axon
• Do input from other neurons via synapses on dendrites increase or decrease membrane potential?

  Increase
• What is the different between depolarisation and repolarisation?

  Depolarisation is when membrane potential goes back to 0, while repolarisation is when membrane potential goes back to the -70mV resting potential (threshold)
• What is the voltage-dependent ion channel for?

  Opens when membrane potential reaches threshold voltage, but closes at resting potential. This allows flow of ions across cell membrane, where Na+ channels will open when V exceeds threshold to depolarise and K+ channels will open to get back to repolarisation
• What is the fixed size and all-or-none principle?

  Fixed size is that the size of action potentials are always the same for that neuron, while all-or-none is either a full action potential will be fired or not (no such thing as small or large potentials)
• What determines the strength of the neuron signal?

  The rate of repeated action potentials
• What happens in the undershooting of repolarisation?

  There is a refractory period, which makes it more difficult for another action potential to occur and preventing action potential going backwards
• Where does action potential start?

  Axon hillock, which has the lowest threshold to trigger action potential
• What does the depolarisation of an action potential cause to neighbouring regions?

  Causes the neighbouring regions to pass threshold to trigger the action potential
• What are neurotransmitters and how are they released?

  Chemical messengers that are released from the pre-synaptic terminal through depolarisation of axon terminal. They act on post-synaptic receptors
• What are synaptic vesicles?

  Stores neurotransmitters in the pre-synaptic terminal. It joins to the cell membrane wall to release neurotransmitters into the synaptic cleft.
• What are neurotransmitter receptors?

  Gates on the post-synaptic side (dendrite) where neurotransmitters in synaptic cleft joins to, activating it to open the ion channels and hence changing the membrane potential on the post neuron
• Explain the "lock and key" concept of the neurotransmitter receptors.

  Each receptor only binds to specific neurotransmitters, so neurotransmitters only activate their specific type of receptor
• What is the purpose of the re-uptake pump?

  Clears neurotransmitters from the synaptic cleft by sucking leftovers back into the pre-synaptic terminal
• What is the purpose of enzymes that float around the synaptic cleft?

  Breaks down neurotransmitters by changing its molecular shape so that it no longer acts and binds with receptors
• What is Parkinson's disease and how is it treated?

  Parkinson's disease is the loss of dopamine neurotransmitters (motor function) in the basal ganglia deep in the brain, which affects movements. This is treated by L-dopa (levodopa) replacing dopamine in the brain
• How do anti-depressant drugs work differently to L-dopa?

  Low levels of serotonin neurotransmitters causes depression. SSRI and MAOI act to keep serotonin in the synaptic cleft longer so it increases serotonin signalling
• What is ligand-gated ion channel?

  Different neurotransmitters bind and open different ion channels to change membrane potential in different ways
• What is the difference between depolarisation and hyperpolarisation?

  Depolarisation is less negative while hyperpolarisation is more negative
• What is the difference between excitatory and inhibitory signals of neurotransmitters?

  Excitatory is when receptor opens channels that cause depolarisation, getting closer to the threshold for action potential. Inhibitory is when receptor causes hyperpolarisation, getting further from threshold for action potential