There are many disorders that take place when we sleep.  One such example is called REM sleep disorder. This disorder takes place in the REM stage of sleep. This happens when your muscles do not lock fully and you are not completely paralyzed as you sleep. If you have REM sleep disorder than you act out your dreams. For example, if in your dream you are walking you will start to walk in real life.
Another sleep disorder is called Narcolepsy.  Narcolepsy is when you cannot control when you sleep. A person with Narcolepsy cannot perform everyday jobs such as driving.  A person with Narcolepsy will fall asleep at any time they can fall asleep anytime. Because of this, they cannot do many things.
 
Another sleep disorder that affects people is called Sleep Apnea. Sleep Apnea is when your airflow gets blocked while you sleep. You cannot breathe when you sleep so you wake up. When you wake up it is only momentarily so you do not realize you woke up during the night. However, this cycle of waking and sleeping can cycle about 100 times a night. This leads to less time spent in deeper sleep such as stage 3 sleep. People with sleep apnea can fell tired even after they slept a full night sleep.
 
The last sleep disorder we will talk about is restless leg syndrome. This is when your leg starts felling various types of pain such as crawling, itching, throbbing and pulling.  There is also nighttime leg twitching. This usually starts after being at rest.  Movement can provide relief to restless leg syndrome.  Symptoms of this syndrome typically worsen in the evening and towards bedtime. 


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Our body has a Circadian Rhythm. Our circadian rhythm acts as a 24-hour internal clock. Our Circadian Rhythm is regulated by the Suprachiasmatic Nucleus.  A Suprachiasmatic Nucleus is a group of nuclei located in the hypothalamus.  The Suprachiasmatic Nucleus expresses clock proteins.  The function of these clock proteins set the pace for the day of activity it controls sleep and hormone releases. 
                                       
The Homeostatic system responds to longer wake periods by adding an urge to sleep.  Neuroscientist discovered that people who are awake have an increased level of adenosine.  The level of adenosine increases during sleep.  Adenosine also decreases during cellular activity.

There are 5 stages of sleep.  The first stage is referred to as light sleep. During the first stage of sleep, muscle activity is lowered and people can be easily awakened from stage 1 sleep. The next stage is stage 2 sleep. In stage 2 sleep the breathing pattern and heart rate slow down. We spend most of our time sleeping in stage 2 sleep.  During stage 3 the brain produces delta waves. Breathing and heart rate go to their lowest level.  During stage 4 there is rhythmic breathing and very limited muscle activity. Stage 5 of sleep is known as REM (Rapid Eye Movement) sleep.  You lose consciousness during REM sleep.  You dream during this period of REM sleep. Also, your body becomes paralyzed all of your limbs lock in place. Your breathing rate and blood pressure rise as well.  During REM sleep your eyes move very rapidly back and forth under your eyelids. This is how the name REM was derived.

​Language is one of the most prominent human abilities.  A neuroscientist has learned a lot about language from stroke patients.  A problem in a language is referred to as aphasia. There are 3 types of language problems Broca’s Aphasia, Wernicke’s Aphasia and word deafness. Broca's Aphasia takes place in the left frontal lobe.  Speech is impaired and it is often slow and it requires the patient a lot of effort. Although speech is impaired people with Broca's Aphasia can still comprehend language. Wernicke’s Aphasia takes place in the left temporal lobe. People with Wernicke’s Aphasia talk at a fluent rate however they cannot make proper sentences.   word deafness takes place in both sides of the temporal lobe.  They cannot who is talking or comprehend speech. Another prominent human ability is the ability to recognize objects.  A loss of this function is called agnosia.  Agnosia is defined as the loss of ability to recognize an object. A case study for this is a patient referred to as D.B.O. D.B.O suffered from many strokes. These strokes led to damage to his temporal lobe.  This damage resulted in the visual entry to the anterior temporal lobe.  D.B.O could not name objects he saw but only objects he touched this is Agnosia. Some other parts of the brain that helps us recognize objects they are fusion face area ( FFA), Parahippocampal Place Area ( PPA)  and Visual word form area ( VWFA).  The FFA is critical for recognizing faces. Damage to the FFA will cause face blindness also known as prosopagnosia. The PPA responds to specific locations such as specific buildings or cities. VWFA recognizes written letters and words.  connections between the VWFA and the rest of the brain work to establish written language.

Patient with  Wernicke's Aphasia video : https://www.youtube.com/watch?v=3oef68YabD0
Patient with Broca’s Aphasia video : https://www.youtube.com/watch?v=JWC-cVQmEmY&t=89s

​Learning and memory is a complex process and a lot of research is currently happing about it.  One famous case study that helps us learn about memory is H.M.  H.M had severe epilepsy as a child. He had severe epilepsy as a child.  He had surgery performed on him to help him alleviate his epilepsy. During this surgery, he lost his hippocampus and his temporal lobe. He lived but he lost his ability to make long term memories. There are 2 types of memory declarative and nondeclarative.  Declarative memory is short term memory and everyday facts. Nondecaltive memory is long term memory and skilled behavior and learned habits.  The prefrontal cortex is very helpful in memory. It helps with your working memory and especially retrieving that memory.  You have semantic memory and nonsemantic memory. semantic memory helps you with object knowledge and nonsemantic memory remembers memories of specific events you witnessed. Memories are stored by changes in synaptic connections

Muscles named Flexor and Extensors works in opposite to each other, causing contraction of some and lengthening of other muscles.  There are 2 types of movement voluntary and involuntary.  Voluntary  movement is movement that you can control. Some examples are moving, talking and sitting. Involuntary movement is actions that you cannot control some examples are reflexes and breathing.  Movement can be changed based on our experience. For example if you do a phisical task more than once you are likily to get better at that task.   Our brain can fine tune movement.  To fine tune our movement our brain uses the sensitivity of muscle spindles also know as Gamma motor neurons.  Another group of motor neurons is known as the Golgi tendon organs detects the force created by contracting muscles and it signals the brain how much force is being applied.  3 parts of the brain help in movement. The motor corex controls alpha motor neurons. It can control many motions and it regulates sepcific musucle functions.  The cerbullum is the 2nd part of the brain that works with movement.  It receives information from head, limbs and cerebral cortex.   The last part of the brain is the basal ganglia.  The basal ganglia controls movemet errors and helps releses dopamine a neurotransimeter that helps with controling movement.

Hearing is one of the ways that we perceive our environment.  Our ear is the main part of the hearing system. Our ear contains 3 parts. The external ear, middle ear and the inner ear.  The external ear contains the pina and the external auditory canal and it is the visual part of our ear. The pina and the external auditory canal capture sound waves. It goes though the ear canal this causes the  tympanic membrane ( eardrum) to vibrate. This causes 3 bones the hammer, anvil and stirrup to vibrate. These vibration leads to the cochlea. Cochlea is a fluid filled structure and it is tuned to certain frequency. The cochlea features 2 different liquids ( Endolymph and Perilymph)  hat are both tuned to different frequencies.