Types of GPCRs

States of Brain Activity Arsalan Yousuf BS 4 th Semester

SLEEP A state of unconsciousness from which the person can be aroused by sensory or other stimuli. Types of Sleep Light Sleep (Slow Wave Sleep) Deep Sleep (REM Sleep) Slow-wave sleep is frequently called “dreamless sleep”. Dreams and sometimes even nightmares do occur during slow-wave sleep. Dreams that occur in REM sleep are associated with more bodily muscle activity, and the dreams of slow-wave sleep usually are not remembered.

The brain is highly active in REM sleep, Overall brain metabolism may be increased as much as 20 %. The electroencephalogram (EEG) shows a pattern of brain waves similar to those that occur during wakefulness. Also called Paradoxical Sleep.

Basic Theories of Sleep Sleep is caused by an active inhibitory process A center located below the mid- pontile level of the brain stem that is required to cause sleep by inhibiting other parts of the brain. Raphe nuclei in the lower half of the pons and in the medulla. Nerve endings of fibers from these raphe neurons secrete serotonin. Stimulus in areas of nucleus of the tractus solitarius and diencephalon can also cause sleep. Muramyl peptide

Brain Waves ALPHA WAVES Alpha waves are rhythmical waves that occur at frequencies between 8 and 13 cycles per second Found in the EEGs of almost all normal adult people when they are awake and in a quiet, resting state of cerebration. During deep sleep, the alpha waves disappear. There is a continuous electrical activity in the brain whose intensity and the patterns results from sleep, wakefulness, or brain diseases such as epilepsy or even psychoses. The entire record is called an EEG (electroencephalogram).

BETA WAVES When the awake person’s attention is directed to some specific type of mental activity, the alpha waves are replaced by asynchronous, higher-frequency but lower- voltage beta waves. E.g. opening closing of eyes due to bright light. Occur at frequencies around 14 to 80 cycles per second. THETA WAVES Theta waves have frequencies between 4 and 7 cycles per second. They occur normally in the parietal and temporal regions in children, Occur during emotional stress in some adults, during disappointment and frustration. Also occur in many brain disorders, often in degenerative brain states. DELTA WAVES Delta waves include all the waves of the EEG with frequencies less than 3.5 cycles/second. They occur in very deep sleep, in infancy, and in serious organic brain disease. Occur strictly in the cortex independent of activities in lower regions of the brain.

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Epilepsy Uncontrolled excessive activity of either part or all of the central nervous system. 50 million people worldwide have epilepsy, 90% of epilepsy occurs in developing countries. Classified into three major types: Grand mal epilepsy, Petit mal epilepsy, Focal epilepsy. Caused due to mutations in genes that code for protein subunits of voltage-gated and ligand-gated ion channels

Grand Mal Epilepsy Extreme neuronal discharges in all areas of the brain. Grand mal seizure lasts from a few seconds to 3 to 4 minutes. Initiated by administering pentylenetetrazol, by insulin hypoglycemia, or by passage of alternating electrical current directly through the brain. Major factor that stops the attack after a few minutes is neuronal fatigue and active inhibition by inhibitory neurons.

Petit Mal Epilepsy Involves the thalamocortical brain activating system. Characterized by 3 to 30 seconds of unconsciousness. Total sequence is called Absence Syndrome or Absence Epliepsy. Brain wave pattern in petit mal epilepsy is typified as spike and dome pattern. It results from oscillation of inhibitory [GABA]–producing neurons) and excitatory thalamocortical and corticothalamic neurons.

Focal Epilepsy Can involve almost any local part of the brain, (cerebral cortex or deeper structures of cerebrum and brain stem). Most oftenly results from some localized organic lesion or functional abnormality. Causes progressive “march” of muscle contraction in the opposite side of the body “Jacksonian Epilepsy”. Another type of focal epilepsy is the psychomotor seizure. (abnormal rage, anxiety, discomfort, fear, mumbling incoherent speech)

Dementia These conditions mainly result from diminished function of neurons that secrete a specific neurotransmitter. Mental depression psychosis, might be caused by diminished formation in the brain of norepinephrine or serotonin. Drugs that block secretion of norepinephrine and serotonin, reserpine, frequently cause depression. Drugs like monoamine oxidase inhibitors, and tricyclic antidepressants, such as imipramine and amitriptyline, increase the excitatory effects of Nor-Epi and Sero. Treated by electroconvulsive therapy, commonly called “shock therapy” to increase nor-epinephrine activity.

Schizophrenia Blocking of neural signals in different areas of cerebral cortex. Dysfunctioning of signal processing. Excitement of a group of neurons that secrete dopamine in the behavioral centers of the brain Abnormal functioning around the hippocampus. Dopamine is secreted by a group of dopamine- secreting neurons whose cell bodies lie in the ventral tegmentum of the mesencephalon, medial and superior to the substantia nigra. The hippocampus is often reduced in size, especially in the dominant hemisphere.

excess dopamine is secreted by a group of dopamine-secreting neurons whose cell bodies lie in the ventral tegmentum of the mesencephalon, medial and superior to the substantia nigra. neurons give rise to the so-called mesolimbic dopaminergic system that projects nerve fibers and dopamine secretion into the medial and anterior portions of the limbic system, especially into the hippocampus, amygdala, anterior caudate nucleus, and portions of the prefrontal lobes. Schizophrenia Drugs such as chlorpromazine, haloperidol and thiothixene decrease secretion of dopamine at dopaminergic nerve endings or decrease the effect of dopamine on subsequent neurons.