Search results
Results from the WOW.Com Content Network
Episodes of vasovagal syncope are typically recurrent and usually occur when the predisposed person is exposed to a specific trigger. Before losing consciousness, the individual frequently experiences early signs or symptoms such as lightheadedness, nausea, the feeling of being extremely hot or cold (accompanied by sweating), ringing in the ears, an uncomfortable feeling in the heart, fuzzy ...
In the brain, serotonin is a neurotransmitter and regulates arousal, behavior, sleep, and mood, among other things. [9] During prolonged exercise where central nervous system fatigue is present, serotonin levels in the brain are higher than normal physiological conditions; these higher levels can increase perceptions of effort and peripheral muscle fatigue. [9]
If there is underlying fear or anxiety (e.g., social circumstances), or acute fear (e.g., acute threat, needle phobia), the vaso-motor centre demands an increased pumping action by the heart (flight or fight response). This is set in motion via the adrenergic (sympathetic) outflow from the brain, but the heart is unable to meet requirements ...
Neurons generate action potentials resulting from changes in the electric membrane potential. Neurons can generate multiple action potentials in sequence forming so-called spike trains. These spike trains are the basis for neural coding and information transfer in the brain.
A leg and foot rotation test can be used to investigate changes in neuron activity within the labyrinth, or the inner ear. When the head is rotated while the leg and foot are rotated 90 degrees, the vestibular signals cause the brain to inhibit movement in the direction of the rotation.
In this simplified brain circuit, damage to orexin-secreting neurons in the hypothalamus can lead to inhibition of motor neurons, thus lowering muscle tone. Cataplexy is considered secondary when it is due to specific lesions in the brain that cause a depletion of the hypocretin neurotransmitter.
Electromyographic studies and nerve conduction studies show normal motor conduction velocity and latency with decreased amplitude of compound muscle action potentials. Pathologically, it is a noninflammatory axonopathy without demyelination. [3] Antibodies attack the coating of the motor neurons without causing inflammation or loss of myelin ...
Central pattern generators are groups of neurons in the spinal cord that are responsible for generating stereotyped movement. It has been shown that in cats, rhythmic activation patterns are still observed following removal of sensory afferents and removal of the brain., [1] indicating that there is neural pattern generation in the spinal cord independent of descending signals from the brain ...