Practice Questions Flashcards
What is the cause of basal ganglia malfunction in Parkinson’s and Huntington’s disease?
In Parkinson’s disease the malfunction is due to the death of dopaminergic neurons in substantia nigra, which leads to less movement. On the other hand in Huntington’s disease it is due to the degeneration in the striatum and reduction of GABA related neurons, which leads to the movement not being properly inhibited.
What is the role of the thalamus and how is it connected to the cortex?
The thalamus has a key role in transforming information to and from the cortex. It is the main relay station for sensory information. It is connected to the cerebral cortex via the internal capsule, which contains afferent and efferent nerve fibres to and from the thalamus.
What is the neural tube? What structure further develops to form the two hemispheres?
The neural tube forms at about day 22 of the development, which then further develops to become the rudimentary spinal cord. It’s anterior part (the anterior neural fold) then expands to form the brain hemispheres.
Why is there different distribution of neurons across the 6 levels of the neocortex?
The different distributions are due to the different functions of the cortical areas. For example, sensory areas have thicker layer 4 while motor areas have thicker level 5.
Name the main lobes, sulci and fissures.
Frontal, temporal, parietal and occipital lobes. Longotudinal fissure; Sylvian fissure, central sulcus
What is the substantial difference between the direct and indirect loops of the basal ganglia?
Basal ganglia receives direct input from cortical areas and the limbic system, however they do not project directly onto the cortex. Rather, they project indirectly through the thalamus. In the direct pathway, the input to the thalamus is less inhibitory, while in the indirect pathway, input to the thalamus is more inhibitory.
What are electrostatic gradient and osmotic balance responsible for?
An electrochemical gradient is a gradient of electrochemical potential, usually for an ion that can move across a membrane. The gradient consists of two parts, the chemical gradient, or difference in solute concentration across a membrane, and the electrical gradient, or difference in charge across a membrane. When there are unequal concentrations of an ion across a permeable membrane, the ion will move across the membrane from the area of higher concentration to the area of lower concentration through simple diffusion. Ions also carry an electric charge that forms an electric potential across a membrane. If there is an unequal distribution of charges across the membrane, then the difference in electric potential generates a force that drives ion diffusion until the charges are balanced on both sides of the membrane
By diffusion of water or solutes, osmotic balance ensures that optimal concentrations of electrolytes and non-electrolytes are maintained in cells, body tissues, and in interstitial fluid. Solutes or water move across a semi-permeable membrane, causing solutions on either side of it to equalize in concentration.
At resting state the inside of a neuron is more…..why?
At resting state, the inside of a neuron is more negative (-70m\v) than the outside (0mV). This is due to the different concentrations of ions (e.g. sodium and potassium) and organic aminos
What is the difference between active and passive potentials?
Action potential is an example of active potential, while a graded potential is an example of passive potential. The main differences are that active potentials are all-or-none, they are not graded and there is no degradation, while the opposite is true for passive potentials. Passive potentials can be inhibitory or excitatory
What is graded potential? Where does it occur?
The graded potential occurs in the dendrite and carries information until the axon hillock. It normally occurs in the grey matter and it has no threshold or refractory period. It is graded meaning it can be excitatory or inhibitory. If the sum of the graded potentials exceeds the threshold, then an action potential will be triggered.
What does LTP mean? What is it involved in?
LTP stands for long term potentiation or the increase strengthening of synapses. It is the main driver of neuroplasticity and has been mostly studied in learning and memory in animal’s hippocampus.
What does it mean that LTP is triggered by NMDA but maintained by AMPA?
What does it mean that LTP is triggered by NMDA but maintained by AMPA?
Briefly describe what happen in the post-synaptic membrane when an action potential reaches the terminal button of the presynaptic neuron?
At the end of the terminal buttons of the pre-synaptic neuron there is the synaptic cleft where neurotransmitters are released when an AP is being sent. These reach the postsynaptic receptors resulting in an increase or decrease of the resting electrical activity ofthe postsynaptic membrane.
Compare and briefly describe differences between visual receptive field of ganglion cells and visual receptive field of simple cells in the primary visual cortex.
Ganglion receptive fields:
• They make up complex cells are larger than simple cells and they don’t have discrete excitatory and inhibitory zones.
• Stimulus orientation is crucial, but position within the receptive field is less critical.
• Simple cells and, at some extent, also geniculate cells form the input to Complex cells.
• Some complex cells respond optimally only to movement in a certain direction
Receptive fields of simple cells:
• respond to different orientation (vertical, horizontal, oblique).
• Simple cells have discrete excitatory and inhibitory zones, which are larger than those found in retina and in LGN, and their size is rectangular rather than circular.
Did bipedalism affect our brain size at birth?
Humans develop a very large brain and yet because of bipedal locomotion the female of the species has a long and narrow birth canal. Hence rather than waiting, we push our babies out early.
In humans the brain continues to grow at the foetal rate for two years after birth (Bogin 1997). By 3 year of age it is at 80% adult capacity and 90% by five years of age (Dekaban & Sadowsky 1978)
