Have you ever thought about why people sleep or what purpose sleep serves? This is something that many have wondered for years. Studying what happens when the average person sleeps, how lon

Movement.html

Movement

Voluntary movement involves complex interactions among different brain regions. One main movement area in the brain is the motor cortex, which is located at the rear of each frontal lobe. In this lecture, we will discuss two other structures, the basal ganglia and the cerebellum, which interact with the motor cortex to produce movement. The role that each structure plays in movement will be considered along with examples of how movement changes when each is impacted by an abnormal process. The basal ganglia are a collection of nuclei interacting with the motor cortex. The basal ganglia are made up of a set of subcortical structures that lie deep inside the brain.

These structures are critical for organizing sequences of movement and for learning motor skills. The main parts are the caudate nucleus, the putamen, and the globuspallidus. The basal ganglia's components work in a loop, receiving information from several cortical areas and then sending the output via the thalamus. Specifically, the caudate and the putamen receive input from the cerebral cortex and send the output to the globuspallidus. Once the globuspallidus has processed the information, it is returned to the motor cortex via the thalamus.

The globuspallidus actually inhibits the thalamus and stops it from inhibiting movement, thus, the basal ganglia works to select (cause) a movement by ceasing to inhibit it. It is like a mother holding her child back when the child wants to take off on a bike for the first time. If the father comes along and stops the mother from holding the child back, the child can take off.

Additional Materials

View a Pdf Transcript of Major Motor Structures

Movement Disorders.html

Movement Disorders

Disorders of the basal ganglia such as Parkinson's disease help to illustrate the role of the basal ganglia in movement. Parkinson's disease involves the loss of pigmented cells in the substantia nigra. These cells are located in the midbrain, and they normally release dopamine into the caudate and the putamen. These cells die off when a person develops Parkinson's disease, and the dopamine that would normally be released to stop the thalamus from inhibiting movement is depleted. Individuals with this disorder have problems with movement and usually develop four cardinal symptoms: rigidity, bradykinesia (motor slowness), postural instability, and resting tremor. This increase in motor activity is due to the drug L-dopa, which helps replace dopamine in the brain. (Note: You might want to research L-dopa, dopamine, and the blood-brain barrier). When people with Parkinson's disease take this drug, they are able to move and interact more freely—but excessive movement is often an unfortunate side effect.

People with cerebellar disorders have problems with balance, coordination, and timing when executing precise movements. When reaching for a target, they might miss it. For example, a person with this disorder trying to catch a ball thrown toward him or her might time the hand movements incorrectly and close his or her hands after the ball arrives. A person with cerebellar damage may appear drunk when moving; having a person walk a straight line or touch the tip of his or her nose is a test of the cerebellar function. The cerebellum is one structure that is highly susceptible to alcohol intoxication, which people such as police officers use to their advantage.

Sleep.html

Sleep

Our sleep-wake cycle is a biologically driven rhythm of rest and activity that we go through on a daily basis. This rhythm is also called the circadian rhythm (which means about a day). It is like an endogenously running clock that our brain maintains even without any other time cues. Without external cues, the rhythm shifts and runs slightly longer than twenty-four hours but it continues to make us sleepy at about the same time and alert at others. External cues (also called Zeitgerbers) can cause a shift, like changing where the hands are on an analogue clock, but like a clock, the amount of time of a sleep-wake cycle is set

Generally, we can say that sleep is a time where we slip into a period of decreased brain activity. Of course, there is the exception that occurs during REM sleep. How do we know what our brain activity level is during sleep? We use EEG machines to measure the change in brain waves. The use of EEG machines enables scientists to characterize and quantify the brain activity during sleep. There are five different phases; four are referred to as stages 1 to 4, and the remaining stage is called REM sleep. Other than the changes in eye movement during REM sleep, there is another connection between sleep and movement. During REM sleep, the pons (a structure in the brain stem) inhibits motor neurons that control the body’s large muscles. The inhibition of the large muscles is necessary because if we move around during REM sleep, we might become injured due to the decrease in or lack of conscious processing.

Additional Materials

View a Pdf Transcript of Suprachiasmatic Nucleus