Download Theme 6. Vision

Biomed T4
Neuroscience – Final Exam – VT04
2004-03-03
Theme 1. Action potenial
The nervous impulse is an electrical signal that travels with a speed of up to 100 m/s along a
nerve fibre.
Describe an action potential and the underlying events. Make a drawing and discuss. For
instance: Which ion currents pass through the membrane? What are the properties of the
currents? What is Hodgkin's cycle? Why is the membrane potential passing 0 mV? What is an
after hyperpolarization? What is a refractory period? (6p)
Theme 2. Myelination of axons
The speed of the action potential can vary depending on if the axon is myelinated or not.
Can you describe how myelination occurs in the peripheral nervous system and by which
mechanism this can have an impact on speed of transmission. (6p)
Theme 3. Synaptic transmission
In synapses utilizing (small) synaptic vesicles rapid recycling of the vesicles is esssential.
Describe the two different mechanisms which are thought to mediate synaptic vesicle recycling.
(6p)
Theme 4. GABA receptors
The amino acid GABA is the major inhibitory neurotransmitter in the brain. GABA binds to and
activate a receptor subtype called GABA A receptor, which belongs to the group of ligand-gated
ion channels or ionotropic receptors. Could you briefly describe these receptors? (3p)
What happens when GABA binds to the GABA A receptor at a membrane potential of about 90mV? (2p)
The GABA A receptor is the target for various drug of clinical importance. Could you mention
one class of such substances? (1p)
Theme 5. Early development of the mammalian nervous system.
a) When does the development of the human nervous system begin? (1p)
b) Describe in words and using simple drawings the process of neuralization of the embryo from
its beginning until the presence of a neural tube (3p)
c) The neural crest. What is it, what does it give rise to? - You may incorporate your answer to
this question in your answer to b) above. (2p)
Theme 6. Sense of hearing
Mechanical vibrations in the air can be experienced as sound if the frequencies and amplitudes
are adequate. The vibrations are transmitted to the hair cells in the cochlea via the tympanic
membrane and the ossicles.
(1) Describe the organisation of the hair cells in the organ of Corti and their transduction
mechanisms? (4p)
(2) Describe the way the nerve impulses elicited by the hair cells take to the brain. Thalamus
nuclei? How is the auditory cortex organised and where is it localised? (2p)
Biomed T4
Neuroscience – Final Exam – VT04
2004-03-03
Theme 7. Locomotor control system
Different regions of the CNS control different aspects of the locomotor behaviour. Describe the
main roles of the following CNS regions in the control of locomotion:
1. The spinal cord; (2p)
2. The brainstem; (1p)
3. The primary motor cortex; (1p)
4. The cerebellum. (2p)
Theme 8: Control of Eye Movements
Eye movements are among the first voluntary movements to develop in the growing child. All
our eye movements serve a specific purpose:
a) What is the overall purpose of eye movements? (1p)
b) Describe three types of eye movements and their respective function. (3p)
1.
Saccades – fast movement that brings a new target on to the fovea.
2.
Smooth pursuit – follows a moving target and keeps it on the fovea.
3.
Vergence movements – brings targets at different distances on to the fovea.
4.
Vestibulo-ocular movements – stabilize the eyes when the head moves fast.
5.
Optokinetic movements – stabilize the eyes when the head moves slowly to
follow a moving target.
(Three of these is sufficient = 3p)
c) Give a brief account of the central mechanisms controlling the horizontal saccadic eye
movements: What structures are involved, including their key roles. (2p)
Theme 9. Processing of visual information in the cerebral cortex.
1.
2.
3.
4.
5.
6.
How is the visual field mapped onto area 17 (V1) ? (1p)
How are the eyes mapped onto area 17 (V1) ? (1p)
What is meant by “orientation selectivity”? (1p)
What are the “orientation columns”? (1p)
Which area is particularly important in processing motion ? (1p)
Which areas are particularly important in the identification of objects based on the visual
properties of the object (color, shape etc)? (1p)
Theme 10 Sleep.
All mammals sleep, the length and form however vary between species; describe the sequence of
states and stages of sleep on a typical (adult human) night. (6p)
Biomed T4
Neuroscience – Final Exam – VT05
2005-03-02
Theme 1. Nervous tissue
Nervous tissue within the CNS can be divided into gray and white matter.
a)
What is the white matter composed of and how it is organized at the subcellular level. (3p)
b)
Corpus callosum is one major structure composed of white matter. Where is it localized
(make a simple drawing) and what is its main role (3p).
Theme 2. Electrical properties of neurons.
Action potentials are all-or-none electrical events that are responsible for electrical signalling in
the CNS.
a)
Describe in the ionic mechanisms underlying the depolarizing and repolarizing phases of
action potentials as well as those mediating the fast and slow afterhyperpolarizations. (3p)
b)
Describe at least two mechanisms that can change the firing frequency of neurons and
explain the mechanisms. (3p)
Theme 3. Presynaptic mechanisms
In the nerve terminal the action potential is converted into release of neurotransmitter. Describe
the different steps which underlie this conversion. The key proteins involved should be included
in the description. (6p)
Theme 4. Pain
You have have bumped your chin bone against a chair.
a)
Describe the components of the pain perception, their time course and the morphological
reasons for the time course of each component. (3p)
b)
Describe why rubbing the site of injury with your hand decreases the pain. (3p)
Theme 5. Hearing
Describe how the vibrations of the tympanic membrane and the ossicles produce nerve impulses
in the cochlea. Include in the description:
a)
how the cochlea differentiates between low and high-frequency vibrations (2p)
b)
the organisation and function of the receptor cells (2p)
c)
the most abundant cation in the extra- and intracellular solutions and the ion flux over the
receptor cell membrane during stimulation. (2p)
Theme 6. Vision
The retina is a complex tissue which contains different cell types that are involved in
transmission of visual signals.
a)
Which different morphological cell types exist in the retina? (3p)
b)
How are these cell types connected ? (3p)
Theme 7. The motor system – postural control
The upright position of the body depends on an intricate postural control system. Characterize the
postural control system by describing the following:
Biomed T4
Neuroscience – Final Exam – VT05
2005-03-02
a)
Which types of sensory signals are used for postural control (3p);
b)
Describe the two principles of operation of the postural control system: feed-back and feedforward, give examples (3p);
Theme 8. The motor system – control of voluntary movement
When we have decided to make a certain movement, for example to start walking across the
street when we see the green light coming on, the CNS will have to initiate activity in the proper
motor program. This means that not only is a process of movement initiation necessary, but also
a process of selection of which one of all available motor programs should be activated.
a)
Which CNS components (i.e. brain structures) are primarily involved in motor program
selection? (1p)
b)
The output signal from these CNS components is inhibitory on to the target neurons. How,
in principle, is a movement initiated via these inhibitory connections? (1p)
c)
Describe the sequence of signaling between the responsible CNS components that leads to
movement initiation. (4p)
Theme 9. Addiction mechanisms
Drugs of abuse exert their addictive properties by affecting neurotransmission at the level of a
group of brain structures.
a)
How are these structures collectively named? Describe briefly the components of this
circuitry? (3p)
b)
All addictive drugs share a common effect within the brain, which involves a specific
neurotransmitter. Which is this neurotransmitter? (1)
c)
Describe one of the mechanisms by which psychostimulants, such as cocaine and
amphetamines, regulate the neurotransmitter in question? (2)
Theme 10. Learning & Memory
Memories can be classified into declarative and procedural memories.
a)
What structures in the brain are important for the formation of new declarative memories?
Where is it believed that long-term storage of memories are located? (3p)
b)
Mention some structures that are of importance for procedural (non-declarative) memories?
(3p)
Biomed T4
Neuroscience – Final Exam – VT06
2006-03-08, 9-14
Theme 1 Vascular system and cerebrospinal fluid.
After a cerebral bleeding blood may enter the ventricular system and affect the sensitive balance
between production and resorption of cerebrospinal fluid (CSF).
a)
Describe the meninges of the brain and how they are located in relation to the CSF.
Describe the anatomical organization of the ventricles? Where is CSF produced and where
is it resorbed back to the blood circulation? (4p)
b)
Describe the main arteries that conduct blood to the brain and define the role of the circle
of Willis. (2p)
Theme 2 Development.
Describe the organization of the growth cone and how it is regulated during axon growth.
Describe the main mechanisms used and give examples of molecules involved. (4p)
Explain the term trophic factor. (2).
Theme 3 Ion channels.
Ions traverse the plasma membrane through ion channels and thus change the membrane
potential.
a)
Describe (i) the structure of ion channels, (ii) how they can recognize and select among the
different ions, and (iii) what mechanisms determine the direction of the flux of ions. (3p)
b)
Describe the mode of operation and function of non-gated and gated channels. (2p)
c)
Describe the different types of gated channels (1p)
Theme 4 Signal transduction.
Mention three distinct intracellular targets that can be regulated by activation of G-protein
coupled receptors and describe the signal transduction pathway involved. (6p)
Theme 5 Vision.
Describe how light, hitting the retina, becomes electrical impulses in the optic nerve. Describe
the types of cells involved, the transduction mechanism in the photoreceptors, receptor
molecules, channels, electrical events, transmitter substances. (6p)
Theme 6 Locomotion.
Characterize the locomotor system in mammals:
a)
Describe the locomotor (walking) movements, main features of locomotor pattern and its
modification with increase of locomotor speed (2p)
b)
Give a definition of locomotor CPG (central pattern generator), list experimental evidences
for its existence (2p)
c)
Describe the role of the sensory input from the limb receptors for the control of locomotion
(2p)
Biomed T4
Neuroscience – Final Exam – VT06
2006-03-08, 9-14
Theme 7 Cerebellum and motor control.
Cerebellum has an important role in the control of movements. Describe briefly the following:
a)
What aspects of motor control are regulated by the cerebellum? (1p)
b)
Which are the two, principally different, kinds of information that are being processed in
the cerebellum, and how is this information used? (2p)
c)
A cellular mechanism that is thought to underlie the regulatory function of the cerebellar
cortex is called long-term depression (LTD). Explain briefly what is meant by LTD, and
how this mechanism is thought to underlie the regulatory function of the cerebellum. (3p)
Theme 8 The autonomic nervous system.
Describe a situation where the sympathetic nervous system becomes activated and what effect
such activation has on the body. Include information on how the sympathetic nervous system is
organized. (6p)
Theme 9 Complex brain functions.
a)
Describe the regions in the cerebral cortex that control language functions. (4p)
b)
What is the role of the amygdala? (2p)
Theme 10 Synaptic plasticity.
a)
Describe the most common intracellular mechanism thought to underlie short-term
potentiation. (2p)
b)
Describe at least one important mechanism for long-term potentiation at the Schaffer
collateral to CA1 pyramidal cell synapse in the hippocampus. (4p)