Modulatory and Arousal Systems Flashcards
Name some examples of anatomically specific neuronal systems.
Somatotopic, retinotopic and cochleotopic projections are all examples of anatomically specific systems - these are mapped to the cortex in discrete areas.
In contrast, modulatory systems do not rely upon precise connections and are anatomically diffuse.
Specific systems typically use what type of receptors at synapses?
Ionotropic / ligand-gated ion channels
The signals in specific pathways encode what types of information?
Sensory, motor and cognitive function.
The pattern of action potential firing is information-rich.
Visualise how firing patterns of individual thalamic cells are translated into an EEG - i.e. a representation of cortical activity.
What does an EEG look like during different points in the sleep-wake cycle?
- Awake but relaxed - low amplitude, high frequency (20-40Hz)
- Asleep - high amplitude, low frequency
- 4 stages of sleep - at each stage, cortical (and thalamic) synchronisation increases, amplitude increases and frequency decreases
- Deepest sleep - frequency < 4Hz
When awake, cells in which region relay sensory information to the cortex? What happens to these cells during sleep?
Thalamic cells - of the LGN and MGN
During sleep:
- Thalamic cells become insensitive to sensory inputs and instead fire action potentials at regular intervals.
- They fire in a synchronised pattern.
- Thus the cortex recieves powerful waves of excitation at slower but regular intervals.
What does the EEG look like during REM sleep, and what are the other important features?
- Very similar to when awake
- Desynchronised activity in thalamus + cortex
- Active “higher” cortex, limbic and sympathetic systems
- Paralysis - apart from some extraocular eye and ear muscles
Describe how the sleep cycle changes over the course of a night.
Higher frequency, lower amplitude EEG acitivity when awake is associated with what?
Attention and concentration
Describe in detail the structure of the modulatory acetylcholine pathway.
Describe and explain the functions of the cholinergic modulatory system, and what happens when this system is dysfunctional.
- Desynchronises thalamic cells - sleep-wake
- Cortex/hippocampus - increased response strength and selectivity, plasticity - increased attention, cognition, learning, memory
- Dysfunction - cognitive decline, memory issues
- Alzheimer’s - basal forebrain, cortex, hippocampus degeneration
Aricept is an AchE inhibitor. Explain why it is used to treat the symptoms of Alzheimer’s.
- Alzheimer’s features cognitive decline and memory issues, partly due to lack of ACh in the cortex, hippocampus and basal forebrain.
- Aricept increases synaptic ACh and so improves cognition and memory.
Describe and explain the structure and functions of the modulatory noradrenergic system, and what happens when it is not functioning properly.
Describe and explain the structure and functions of the modulatory dopamine system, and what happens when it is not functioning properly.
- Mesocortical and mesolimbic pathways project from VTA to cortex and limbic systems.
- Nigrostriatal DAergic neurons project from substantia nigra to basal ganglia.
Describe the functions of the modulatory histamine system and what happens when it is not functioning properly.
- Diphenyhydramine - 1st generation antihistamine - over the counter sleeping pill
Describe the structure and function of the orexin (hypocretin) modulatory system.
Describe and explain the structure and functions of the modulatory serotonin system, and what happens when it is not functioning properly.
Describe what happens in the various modulatory systems when arousal from sleep to wake occurs.
- A lesion in the brainstem may result in coma
Describe what happens in the various modulatory systems when you start to fall asleep.
What happens in the various modulatory systems during REM sleep?
Describe what happens in the various modulatory systems when arousal from quiet waking to full attention/vigilance occurs.
