Back to Revision NotesQ1.
The basic notion here is that there is a circadian rhythm (M) which
is out of phase (M) with the entraining zeitgebers (M) after time zone
displacement (M). Hence the activity/sleep (M) and core temperature rhythms
need to be entrained to the new cycle (M). Whilst this re-entrainment is
happening there is a temporary form of internal disassociation which impairs
performance on physical and mental tasks = jet lag (M). Book 5, p.73.
1 mark for each (M) = 8 marks.
Biological aspects worth 12 marks:
suprachiasmatic nuclei (SCN) generate endogenous rhythm (output may
be hormonal) §3.8.2; light influences SCN via retinohypothalamic tract
§3.8.4; output from SCN and caudate nuclei to pineal §3.8.5;
electrical stimulation of SCN mimics effect of light §3.8.7; melatonin
secretion from pineal in dark §3.9; pineal 180° out of phase with
SCN §3.9; pineal driven by SCN §3.10; GABA (agonist triazolam)
implicated as SCN neurotransmitter §3.10.2 (8 points worth about 1.5
marks each - flexibly).
Motivation in homeostatic systems has four characteristic: changing
responsiveness to constant stimuli; it is goal-directed (an animal will
employ a range of behaviours to remove an unwanted intruder); it provides
a common currency by which an animal chooses between competing activities
(to fight or to feed etc.); it potentiates species-specific activity (the
behaviours used in combat are species typical) (Bk. 1. Ch.7).
Motivation is made up of internal and external factors.
Finally, appetitive and consummatory behaviours are differently controlled
and feeding at least appears to have a dopamine-based reward centre. (Bk.
5, Ch. 2).
It is reasonable to argue that aggression and its motivation have the
four characteristics listed above, however with respect to changing responsiveness
to constant stimuli there is no sense in which combat satiation reduces
motivation, exhaustion might, but the recency of a fight does not reduce
the tendency of an animal to fight to, say, protect the nest. Clearly with
aggression there are internal and external factors at play (hormones and
other animals respectively).
It is quite possible to argue that threat is appetitive and victory
is consummatory behaviour, though it is not clear whether they are differently
controlled. The studies of Flynn (Bk. 2, p. 275) suggest predation and
threat may be controlled by different regions of the brain, although those
of Adams (Bk 5. p109) suggest that different regions of the hypothalamus
influence different species-typical behaviours. Finally, there is no evidence
for an aggression reward centre.
5 marks each for: motivation, aggression, linking them, general
quality.
a) Gene activation (Bk 4: §5.8), protein synthesis (Bk 4: §5.6,
5.8), glycoprotein synthesis (§5.8), thickening of synaptic apposition
zones (§5.5), re-location of synapses on dendritic spikes (§5.5),
NMDA receptor activation - second messenger systems and retrograde signals
(§5.7.3). 12 marks
Also could include Long-Term Potentiation, dendrite density changes.
b) The Hebbian synapse is one in which activity in a primary synapse strengthens a secondary synapse to the same post-synaptic cell (Bk 4: §5.4) A diagram would help. The data in (a) are all consistent with changes in the primary synapse. Only gene activation, protein synthesis, glycoprotein synthesis are consistent with changes in a secondary synapse. There is no direct proof for the concept of a Hebbian synapse. 8 marks (4 for Hebb synapse, 4 for linking).
The basic mechanism is through neuron/target interactions. A neuron which makes contact with an appropriate target is in a position to obtain appropriate chemotrophic factor. However, the neuron must make a sufficient number of functioning synapses in order to survive. The factor is transported through the neuron where it sustains the cell. The larger the target, the greater the amount of chemotrophic factor that it produces and hence the larger the number of neurons it can maintain. Nerve growth factor is a chemotrophic factor, although different targets produce different factors. Another aspect is the timing of innervation. Axons have to reach the appropriate target within a short time window, whilst the target is producing the appropriate NGF. Neurons need to be functionally active to survive. A final aspect if that neurons need an appropriate input. Whisker barrel cells in the cortex that do not receive even an indirect input from the peripheral receptors die (Book 4: §3.2)
Up to 16 marks for the data, + 8 for understanding, with max allowed of 20.
The effect of pain is no different from that of vision: they both alter
the way an animal behaves. They can lead to subtle changes in behaviour
or to major changes depending on the nature of the sensation and the context.
Furthermore, they can all lead to , or be associated with, feelings. Thus
particular sensations, including pain, create particular moods.
Vision has both a proximal and a distal component. The proximal stimulus
is interpreted in a way that deduces the nature of the distal object. There
is no equivalent for pain: is has only a proximal component and the nature
of the agent that gave rise to the proximal stimulus cannot be deduced
from the pain (Bk. 3 §4.1).
In terms of the neurophysiology, there are no "fundamental" differences between them. They may differ marginally in the sense organs used or their thresholds of response, but they all transduce one form of energy into action potentials and use the nervous system to convey that information to the brain. The extent of processing that that information undergoes varies from sense to sense but the principles are the same.
Where there is a fundamental difference is in the discrimination. There
are numerous visual sensations (movement, colour, depth, etc.), but pain
just hurts. The hurt may vary in intensity, but it lacks any range. The
kind of descriptive words used in the McGill pain questionnaire refer to
location, duration or intensity, not quality. Hence a stabbing pain would
be one that changes its location in a short space of time in a small areas
(p181).
A final distinction is that pain may be masked, i.e. stress-induced
analgesia. There is no equivalent for vision (Bk. 3, §5.4.4).
Impression mark based on 6 for pain, 6 for vision, 8 for logic, structure, clarity, etc.
a) Students need to describe the anatomy (7 marks) and function (7 marks) of the cortex as given in Book 2 §8.7.5, 8.8, with additional information from pp 258, 259.
b) There is no straightforward answer to this, although the thrust must
be towards social complexity and awareness - the ability to integrate information
from several sensory modalities. Birds are predominantly visual, have good
memories and good spatial maps (Bk. 2, §8.7.4). Many students will
refer to language, but that only applies to one primate (Bk. 2, §11.2,
11.4)
6 marks
Alternatively, for a good answer based on anatomy and function only
gross = 7 marks, fine = 7 marks, plus 6 impression marks for part b material.
The effect of activity at a synapse may be to cause an excitatory or inhibitory post-synaptic potential (M). EPSPs result from an influx of sodium ions into the post-synaptic cell. IPSPs can result from an influx of chloride or closing of sodium channels (M). These PSPs are small (M), graded (M) and decrease with distance from the synapse (M). They also are summative (M). There is temporal (M2) and spatial (M2) summation. Further, those synapses nearest to the axon hillock have the greatest effect on the axon hillock (M2). It is when the extent of depolarization of the cell body, caused by the summed effects of the various IPSPs and EPSPs is sufficient to open voltage-gated sodium channels (M) (i.e. threshold (M)), that the axon fires (M2). Book 2 §4.3.
One mark for each M, 2 for each M2 + 4 for understanding.
Explanation of survival of the species, versus explanation of the current position (i.e. survival of the individual) - 6 marks.
Use of examples, 6 marks = 2 each x 3.
Understanding and cogency of argument - 8 marks.
Book 5, §4.5, especially 4.5.3; Book 1 §4.3.
Definition of what depression is. Not simply just in terms of exogenous vs. endogenous. Psychological vs. neurological. Definitions of normal/abnormal.
Complications with other diseases. 8 marks
Explanations and treatment aspects. 1 social, 2 familial, 3 grounded social and 4 biological "causes" (the latter including neurotransmitter imbalance and genetic predisposition. 4 marks each => 16.
Max mark limited to 20!
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