membrane potential

Examples of membrane potential in the following topics:

• Mechanics of the Action Potential

  • Resting potential.
  • The membrane potential (or, voltage across the membrane) at this state is -70 mV, with the inside being negative relative to the outside.
  • If the membrane potential reaches -55 mV, it has reached the threshold of excitation.
  • Eventually, the cell potential reaches +40 mV, or the action potential.
  • This expulsion acts to restore the localized negative membrane potential of the cell.

• Stages of the Action Potential

  • Neural impulses occur when a stimulus depolarizes a cell membrane, prompting an action potential which sends an "all or nothing" signal.
  • A neuron at resting potential has a membrane with established amounts of sodium (Na+) and potassium (K+) ions on either side, leaving the inside of the neuron negatively charged relative to the outside.
  • As these positive ions rush in, the membrane of the stimulated cell reverses its polarity so that the outside of the membrane is negative relative to the inside.
  • This expulsion acts to restore the localized negative membrane potential of the cell, bringing it back to its normal voltage.
  • The sodium gates cannot be opened again until the membrane is repolarized to its normal resting potential.

• Neurotransmitters

  • A neuron has a negative charge inside the cell membrane relative to the outside of the cell membrane; when stimulation occurs and the neuron reaches the threshold of excitement this polarity is reversed.
  • When the chemical message reaches the axon terminal, channels in the postsynaptic cell membrane open up to receive neurotransmitters from vesicles in the presynaptic cell.
  • Inhibitory neurotransmitters cause hyperpolarization of the postsynaptic cell (that is, decreasing the voltage gradient of the cell, thus bringing it further away from an action potential), while excitatory neurotransmitters cause depolarization (bringing it closer to an action potential).
  • If there is no receptor protein in the membrane of the postsynaptic element, then the neurotransmitter has no effect.
  • The depolarizing (more likely to reach an action potential) or hyperpolarizing (less likely to reach an action potential) effect is also dependent on the receptor.

• Olfaction: The Nasal Cavity and Smell

  • The area in the nasal cavity near the septum is reserved for the olfactory mucous membrane, where olfactory receptor cells are located.
  • In humans, there are about 10 million olfactory cells, each of which has 350 different receptor types composing the mucous membrane.
  • Recent research shows that pheromones play a role in human attraction to potential mates, the synchronization of menstrual cycles among women, and the detection of moods and fear in others.

• Habituation, Sensitization, and Potentiation

  • Potentiation, habituation, and sensitization are three ways in which stimuli in the environment produce changes in the nervous system.
  • Three ways in which this occurs include long-term potentiation, habituation, and sensitization.
  • One way that the nervous system changes is through potentiation, or the strengthening of the nerve synapses (the gaps between neurons).
  • Long-term potentiation (LTP) is the persistent strengthening of synapses based on recent patterns of activity: it occurs when a neuron shows an increased excitability over time due to a repeated pattern, behavior, or response.

• Audition: Hearing, the Ear, and Sound Localization

  • It includes the pinna, the ear canal, and the most superficial layer of the ear drum, the tympanic membrane.
  • Once the wave has vibrated the tympanic membrane, sound enters the middle ear.

• Humanistic Psychology

  • Humanistic psychology adopts a holistic view of human existence through explorations of meaning, human potential, and self-actualization.
  • It adopts a holistic approach to human existence through investigations of concepts such as meaning, values, freedom, tragedy, personal responsibility, human potential, spirituality, and self-actualization.
  • This approach focuses on maximum human potential and achievement rather than psychoses and symptoms of disorder.
  • He believed that every person has a strong desire to realize his or her full potential—or to reach what he called "self-actualization."
  • Perhaps most importantly, the humanistic perspective emphasizes the need to strive for positive goals and explains human potential in a way that other theories cannot.

• Specific Learning Disorder

  • The DSM does not require that a single domain of difficulty (such as as reading, mathematics, or written expression) be identified—instead, it is a single diagnosis that describes a collection of potential difficulties with general academic skills, simply including detailed specifiers for the areas of reading, mathematics, and writing.
  • However, some potential causes or contributing factors are:

• Other Steps

  • Dendrites, which are extensions of neurons, receive the impulse and allow the synapse to increase in strength; this is known as long-term potentiation.
  • Long-term potentiation initiates NMDA (N-methyl-D-aspartate) receptors, which in turn influence the flow of information between neurons.

• Substance Abuse and Health

  • This chart compares the relative danger of particular substances based on the dependence level developed and the potential physical harm to the user and others.
  • Heroin, with an extremely high dependence and high potential for physical harm, is an extremely dangerous substance.