What is the name for the process of converting a stimulus into an action potential group of answer choices?


The basic pathway for a nerve impulse is described by the stimulus response model

  • A stimulus is a change in the environment (either external or internal) that is detected by a receptor
  • Receptors transform environmental stimuli into electrical nerve impulses
  • These impulses are then transmitted via neurons to the central nervous system where decision-making occurs
  • When a response is selected (consciously or unconsciously), the signal is transmitted via neurons to effectors
  • Effectors are organs (either muscles or glands) that produce a response to a stimulus
  • A response is a change in the organism resulting from the detection of a stimulus

Overview of the Stimulus-Response Pathway

What is the name for the process of converting a stimulus into an action potential group of answer choices?

Three types of neurons are required to transmit information via the stimulus-response pathway:

  • Sensory neurons transmit information from sensory receptors to the central nervous system (CNS)
  • Relay neurons (interneurons) transmit information within the CNS as part of the decision-making process
  • Motor neurons transmit information from the CNS to effectors (muscles or glands), in order to initiate a response


While these three types of neurons share common features, their basic structure may differ slightly according to their function

  • This includes their length, cell body (soma) position and the comparative distribution of dendrites and axon terminals

Types of Nerve Cells

What is the name for the process of converting a stimulus into an action potential group of answer choices?

  • Neurons communicate with each other via electrical events called ‘action potentials’ and chemical neurotransmitters.
  • At the junction between two neurons (synapse), an action potential causes neuron A to release a chemical neurotransmitter.
  • The neurotransmitter can either help (excite) or hinder (inhibit) neuron B from firing its own action potential.
  • In an intact brain, the balance of hundreds of excitatory and inhibitory inputs to a neuron determines whether an action potential will result.

Neurons are essentially electrical devices. There are many channels sitting in the cell membrane (the boundary between a cell’s inside and outside) that allow positive or negative ions to flow into and out of the cell.

Normally, the inside of the cell is more negative than the outside; neuroscientists say that the inside is around -70 mV with respect to the outside, or that the cell’s resting membrane potential is -70 mV.

This membrane potential isn’t static. It’s constantly going up and down, depending mostly on the inputs coming from the axons of other neurons. Some inputs make the neuron’s membrane potential become more positive (or less negative, e.g. from -70 mV to -65 mV), and others do the opposite.

These are respectively termed excitatory and inhibitory inputs, as they promote or inhibit the generation of action potentials (the reason some inputs are excitatory and others inhibitory is that different types of neuron release different neurotransmitters; the neurotransmitter used by a neuron determines its effect).

Action potentials are the fundamental units of communication between neurons and occur when the sum total of all of the excitatory and inhibitory inputs makes the neuron’s membrane potential reach around -50 mV (see diagram), a value called the action potential threshold.

Neuroscientists often refer to action potentials as ‘spikes’, or say a neuron has ‘fired a spike’ or ‘spiked’. The term is a reference to the shape of an action potential as recorded using sensitive electrical equipment.

What is the name for the process of converting a stimulus into an action potential group of answer choices?

A neuron spikes when a combination of all the excitation and inhibition it receives makes it reach threshold. On the right is an example from an actual neuron in the mouse's cortex. (Image: Alan Woodruff / QBI)

Synapses: how neurons communicate with each other

Neurons talk to each other across synapses. When an action potential reaches the presynaptic terminal, it causes neurotransmitter to be released from the neuron into the synaptic cleft, a 20–40nm gap between the presynaptic axon terminal and the postsynaptic dendrite (often a spine).

After travelling across the synaptic cleft, the transmitter will attach to neurotransmitter receptors on the postsynaptic side, and depending on the neurotransmitter released (which is dependent on the type of neuron releasing it), particular positive (e.g. Na+, K+, Ca+) or negative ions (e.g. Cl-) will travel through channels that span the membrane.

Synapses can be thought of as converting an electrical signal (the action potential) into a chemical signal in the form of neurotransmitter release, and then, upon binding of the transmitter to the postsynaptic receptor, switching the signal back again into an electrical form, as charged ions flow into or out of the postsynaptic neuron.

What is the name for the process of converting a stimulus into an action potential group of answer choices?

An action potential, or spike, causes neurotransmitters to be released across the synaptic cleft, causing an electrical signal in the postsynaptic neuron. (Image: By Thomas Splettstoesser / CC BY-SA 4.0)

Video: Action potentials in neurons

Concepts and definitions

Axon – The long, thin structure in which action potentials are generated; the transmitting part of the neuron. After initiation, action potentials travel down axons to cause release of neurotransmitter.

Dendrite – The receiving part of the neuron. Dendrites receive synaptic inputs from axons, with the sum total of dendritic inputs determining whether the neuron will fire an action potential.

Spine – The small protrusions found on dendrites that are, for many synapses, the postsynaptic contact site.

Membrane potential – The electrical potential across the neuron's cell membrane, which arises due to different distributions of positively and negatively charged ions within and outside of the cell. The value inside of the cell is always stated relative to the outside: -70 mV means the inside is 70 mV more negative than the outside (which is given a value of 0 mV).

Action potential – Brief (~1 ms) electrical event typically generated in the axon that signals the neuron as 'active'. An action potential travels the length of the axon and causes release of neurotransmitter into the synapse. The action potential and consequent transmitter release allow the neuron to communicate with other neurons.

Neurotransmitter – A chemical released from a neuron following an action potential. The neurotransmitter travels across the synapse to excite or inhibit the target neuron. Different types of neurons use different neurotransmitters and therefore have different effects on their targets. 

Synapse – The junction between the axon of one neuron and the dendrite of another, through which the two neurons communicate.

QBI research

QBI Laboratories working on neurons and neuronal communication: Professor Stephen Williams, Professor Pankaj Sah

QBI Laboratories working on synapses: Dr Victor Anggono, Professor Joseph Lynch, Professor Frederic Meunier

Conversion of sensory stimuli

What is the name for the process of converting a stimulus into an action potential group of answer choices?

Principal steps of sensory processing.

In physiology, transduction is the translation of arriving stimulus into an action potential by a sensory receptor. It begins when stimulus changes the membrane potential of a receptor cell.

A receptor cell converts the energy in a stimulus into an electrical signal.[1] Receptors are broadly split into two main categories: exteroceptors, which receive external sensory stimuli, and interoceptors, which receive internal sensory stimuli.[2][3]

Transduction and the senses

The visual system

In the visual system, sensory cells called rod and cone cells in the retina convert the physical energy of light signals into electrical impulses that travel to the brain. The light causes a conformational change in a protein called rhodopsin.[1] This conformational change sets in motion a series of molecular events that result in a reduction of the electrochemical gradient of the photoreceptor.[1] The decrease in the electrochemical gradient causes a reduction in the electrical signals going to the brain. Thus, in this example, more light hitting the photoreceptor results in the transduction of a signal into fewer electrical impulses, effectively communicating that stimulus to the brain. A change in neurotransmitter release is mediated through a second messenger system. Note that the change in neurotransmitter release is by rods. Because of the change, a change in light intensity causes the response of the rods to be much slower than expected (for a process associated with the nervous system).[4]

The auditory system

In the auditory system, sound vibrations (mechanical energy) are transduced into electrical energy by hair cells in the inner ear. Sound vibrations from an object cause vibrations in air molecules, which in turn, vibrate the ear drum. The movement of the eardrum causes the bones of the middle ear (the ossicles) to vibrate.[5][6] These vibrations then pass into the cochlea, the organ of hearing. Within the cochlea, the hair cells on the sensory epithelium of the organ of Corti bend and cause movement of the basilar membrane. The membrane undulates in different sized waves according to the frequency of the sound. Hair cells are then able to convert this movement (mechanical energy) into electrical signals (graded receptor potentials) which travel along auditory nerves to hearing centres in the brain.[7]

The olfactory system

In the olfactory system, odorant molecules in the mucus bind to G-protein receptors on olfactory cells. The G-protein activates a downstream signalling cascade that causes increased level of cyclic-AMP (cAMP), which trigger neurotransmitter release.[8]

The gustatory system

In the gustatory system, perception of five primary taste qualities (sweet, salty, sour, bitter and umami [savoriness] ) depends on taste transduction pathways, through taste receptor cells, G proteins, ion channels, and effector enzymes.[9]

The somatosensory system

In the somatosensory system the sensory transduction mainly involves the conversion of the mechanical signal such as pressure, skin compression, stretch, vibration to electro-ionic impulses through the process of mechanotransduction.[10] It also includes the sensory transduction related to thermoception and nociception.

References

  1. ^ a b c Molecular cell biology. Lodish, Harvey F. (4th ed.). New York: W.H. Freeman. 2000. ISBN 0-7167-3136-3. OCLC 41266312.{{cite book}}: CS1 maint: others (link)
  2. ^ "Definition of EXTEROCEPTOR". www.merriam-webster.com. Retrieved 2018-03-29.
  3. ^ "Definition of INTEROCEPTOR". www.merriam-webster.com. Retrieved 2018-03-29.
  4. ^ Silverthorn, Dee Unglaub. Human Physiology: An Integrated Approach, 3rd Edition, Inc, San Francisco, CA, 2004.
  5. ^ Koike, Takuji; Wada, Hiroshi; Kobayashi, Toshimitsu (2002). "Modeling of the human middle ear using the finite-element method". The Journal of the Acoustical Society of America. 111 (3): 1306–1317. Bibcode:2002ASAJ..111.1306K. doi:10.1121/1.1451073. PMID 11931308.
  6. ^ W., Clark, William (2008). Anatomy and physiology of hearing for audiologists. Ohlemiller, Kevin K. Clifton Park, NY: Thomson Delmar. ISBN 978-1-4018-1444-1. OCLC 123956006.
  7. ^ Eatock, R. (2010). Auditory receptors and transduction. In E. Goldstein (Ed.), Encyclopedia of perception. (pp. 184-187). Thousand Oaks, CA: SAGE Publications, Inc. doi:10.4135/9781412972000.n63
  8. ^ Ronnett, Gabriele V.; Moon, Cheil. L (2002). "G Proteins and Olfactory Signal Transduction". Annual Review of Physiology. 64 (1): 189–222. doi:10.1146/annurev.physiol.64.082701.102219. PMID 11826268.
  9. ^ Timothy A Gilbertson; Sami Damak; Robert F Margolskee, "The molecular physiology of taste transduction", Current Opinion in Neurobiology (August 2000), 10 (4), pg. 519-527
  10. ^ Biswas, Abhijit; Manivannan, M.; Srinivasan, Mandyam A. (2015). "Vibrotactile Sensitivity Threshold: Nonlinear Stochastic Mechanotransduction Model of the Pacinian Corpuscle". IEEE Transactions on Haptics. 8 (1): 102–113. doi:10.1109/TOH.2014.2369422. PMID 25398183. S2CID 15326972.

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