| Date | May 2011 | Marks available | 3 | Reference code | 11M.3.HL.TZ1.5 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Explain | Question number | 5 | Adapted from | N/A |
Question
Define the term stimulus.
Outline the functions of the following parts of the brain.
Medulla oblongata:
Outline the functions of the following parts of the brain.
Hypothalamus:
Explain the effects of psychoactive drugs on synaptic transmission.
Outline how endorphins act as painkillers.
Markscheme
stimulus is a change in the (internal/external) environment that can be detected
medulla oblongata: controls autonomic functions of the body such as heart rate/blood pressure/ventilation/swallowing/vomiting/digestion/cranial reflexes
hypothalamus: links nervous and endocrine systems/produces hormones secreted by posterior pituitary/controls hormonal secretion by pituitary/maintains homeostasis such as control of body temperature/hunger/thirst/fatigue/circadian cycles
psychoactive drugs may increase or decrease transmission (to the post-synaptic membrane);
may increase the release/delay the breakdown/interfere with storage/uptake/reabsorption of neurotransmitters;
may mimic the action of neurotransmitters;
inhibitory drugs may reduce the effect of excitatory neurotransmitters/increase the effect/release of inhibitory neurotransmitters;
inhibitory drugs can hyperpolarize the post-synaptic neuron;
endorphins released by pituitary gland (during stress, injury or exercise);
endorphins block transmission of impulses at synapses involved in pain perception;
bind to receptors in the membrane neurons (involved in) sending pain signal;
block release of neurotransmitters;
Examiners report
Candidates were not able to give a concise definition that was complete. The definition of stimulus is given in the syllabus.
Outlining the functions of the two parts of the brain was done fairly well by many candidates who were able to get the two marks.
Outlining the functions of the two parts of the brain was done fairly well by many candidates who were able to get the two marks.
As noted on the G2 forms, candidates were not sure what to include in their explanations of the effects of psychoactive drugs on synaptic transmission. The more able candidates were able to bring in different ways drugs could either increase or decrease synaptic transmission.
This section on how endorphins act as painkillers was very poorly done by most. It seemed that endorphins had not specifically been studied.
