special senses
The RAS (reticular activating
system) is found in the reticular
formation, which is in the
brainstem. It controls
wakefulness and sleep. The
RAS neurons have axons that
extend from the reticular
formation to the cerebral cortex
through the thalamus. Increased
activity of the RAS wakes us
up from sleep (arousal). Sleep
is a state of altered consciousness.
There are two types of sleep:
1. REM sleep (rapid eye movement) (also called paradoxical sleep): during
this stage, our eyes will move rapidly in different directions. This means
that the cerebral cortex is very active and that the brain is producing
waves similar to waves produced during wakefulness. These waves are
called beta waves. The peripheral muscle tone is inhibited during this
stage; therefore, it is very hard to wake up someone in this stage. Dreams
in this stage are remembered the next day.
2. NREM (Non-REM sleep) (also called slow waves and deep sleep): this
stage is associated with slower waves called delta waves. This is when
the body repairs muscles and tissues, stimulates growth and
development, boosts immune function, and builds up energy for the next
day. Dreams in this stage are not remembered the next day. The NREM
sleep consists of four stages.
Ascending (sensory tracts) and descending tracts (motor tracts like the
corticospinal tract) will stop momentarily in the reticular formation, which
might wake us up. For example, a person might wake up from a pinch or hot/
cold water. A night shift security guard continues to walk in order to stimulate
his motor tracts (corticospinal tract which activates the RAS); therefore, staying
awake.
The sleep cycle consists of NREM sleep and REM sleep. REM sleep starts after
60-90 minutes from falling asleep, and they will start to reappear every 90-
, minute intervals for progressively
longer periods of time. Their
duration will increase a few
minutes at first (10 minutes) but
will increase for 30 minutes
towards the end of the sleep cycle.
duration will progressively
decrease. Around 25% of the sleep
cycle is spent in REM sleep, and the
other 75% is spent in NREM sleep.
We can record the electrical patterns
in our brain by using an EEG
(electroencephalogram). It can
differentiate the different waves by
measuring the activity of muscle
tones. When there is no muscle tone
activity then this means that we are in the REM sleep, and the EEG will detect
beta waves. It is easier to wake a person during the NREM sleep. Our heart rate
during sleep is very low but relatively increases and becomes irregular during
the REM sleep.
Memory
Learning is the ability to acquire new information or skills through instructions
or experiences. However, memory is the process by which the information
acquired through learning is stored and retrieved.
There are 3 types of memories:
1. Immediate memory: information that you recall for a few seconds. For
example, a mobile number you are dialing.
2. Short-term memory: information that you recall for a few weeks or a
month. For example, the material we study for our exams. We only need
to register the information to be able to recall it.
3. Long-term memory: information that you recall for a long period of
time. This type of information must be processed, consolidated and
registered. Consolidation is the activation of memory stores. This
happens either chemically, anatomically, or both. Anatomical changes
occur by increasing the number of synapses by diverging the axon of the
same neuron. These changes are permanent.
The RAS (reticular activating
system) is found in the reticular
formation, which is in the
brainstem. It controls
wakefulness and sleep. The
RAS neurons have axons that
extend from the reticular
formation to the cerebral cortex
through the thalamus. Increased
activity of the RAS wakes us
up from sleep (arousal). Sleep
is a state of altered consciousness.
There are two types of sleep:
1. REM sleep (rapid eye movement) (also called paradoxical sleep): during
this stage, our eyes will move rapidly in different directions. This means
that the cerebral cortex is very active and that the brain is producing
waves similar to waves produced during wakefulness. These waves are
called beta waves. The peripheral muscle tone is inhibited during this
stage; therefore, it is very hard to wake up someone in this stage. Dreams
in this stage are remembered the next day.
2. NREM (Non-REM sleep) (also called slow waves and deep sleep): this
stage is associated with slower waves called delta waves. This is when
the body repairs muscles and tissues, stimulates growth and
development, boosts immune function, and builds up energy for the next
day. Dreams in this stage are not remembered the next day. The NREM
sleep consists of four stages.
Ascending (sensory tracts) and descending tracts (motor tracts like the
corticospinal tract) will stop momentarily in the reticular formation, which
might wake us up. For example, a person might wake up from a pinch or hot/
cold water. A night shift security guard continues to walk in order to stimulate
his motor tracts (corticospinal tract which activates the RAS); therefore, staying
awake.
The sleep cycle consists of NREM sleep and REM sleep. REM sleep starts after
60-90 minutes from falling asleep, and they will start to reappear every 90-
, minute intervals for progressively
longer periods of time. Their
duration will increase a few
minutes at first (10 minutes) but
will increase for 30 minutes
towards the end of the sleep cycle.
duration will progressively
decrease. Around 25% of the sleep
cycle is spent in REM sleep, and the
other 75% is spent in NREM sleep.
We can record the electrical patterns
in our brain by using an EEG
(electroencephalogram). It can
differentiate the different waves by
measuring the activity of muscle
tones. When there is no muscle tone
activity then this means that we are in the REM sleep, and the EEG will detect
beta waves. It is easier to wake a person during the NREM sleep. Our heart rate
during sleep is very low but relatively increases and becomes irregular during
the REM sleep.
Memory
Learning is the ability to acquire new information or skills through instructions
or experiences. However, memory is the process by which the information
acquired through learning is stored and retrieved.
There are 3 types of memories:
1. Immediate memory: information that you recall for a few seconds. For
example, a mobile number you are dialing.
2. Short-term memory: information that you recall for a few weeks or a
month. For example, the material we study for our exams. We only need
to register the information to be able to recall it.
3. Long-term memory: information that you recall for a long period of
time. This type of information must be processed, consolidated and
registered. Consolidation is the activation of memory stores. This
happens either chemically, anatomically, or both. Anatomical changes
occur by increasing the number of synapses by diverging the axon of the
same neuron. These changes are permanent.
