Neuroscience: Inhibitory Signals and Action Potential

Inhibitory Signals

• Inhibitory signals make a cell less likely to fire.
• Summation occurs at the axon hillock, where all incoming signals are added together.
• The neuron fires when the sum of excitatory signals is 15 mV stronger than inhibitory signals.
• The threshold value for firing is -55 mV.
• The neuron's resting potential is -70 mV.

Resting Membrane Potential

• The inside of the cell is more negatively charged than the outside.
• This is due to the concentration of ions inside and outside the cell.
• Key ions include positively charged sodium (Na+) and potassium (K+).
• Ion channels in the cell membrane control the movement of ions.
• Concentration gradients and electrical gradients drive ion movement.

Action Potential

• An action potential is a sudden change in voltage across the cell membrane.
• It occurs at one section of the cell at a time, creating a chain reaction.
• Sodium channels open when the membrane potential reaches -55 mV, causing Na+ to rush into the cell.
• This depolarizes the cell, making it more positive inside.
• Potassium channels then open, allowing K+ to move out of the cell, repolarizing it.

Refractory Period

• The Na+/K+ pump actively moves 3 Na+ ions out of the cell and 2 K+ ions in.
• This helps restore the resting membrane potential.
• It requires energy and is not passive diffusion.

Myelinated Axons

• In myelinated axons, the action potential jumps from one node of Ranvier to the next, called saltatory conduction.
• Saltatory conduction increases the speed of signal transmission.
• It is energy efficient as fewer ions need to move.

Synaptic Transmission

• Cells in the nervous system communicate through synaptic transmission.
• Neurotransmitters are released from the presynaptic neuron and bind to receptors on the postsynaptic neuron.
• Neurotransmitters can be excitatory or inhibitory.
• Receptors are ligand-gated ion channels.
• Reuptake removes neurotransmitters from the synapse.

Short-Term Memory

• George Miller described the capacity of short-term memory as 7 plus or minus 2 items.
• Chunking information into meaningful units can increase short-term memory capacity.
• Chase and Ericsson's research demonstrated that digit span could be increased with practice.
• This increase in capacity is due to chunking, not a fundamental change in short-term memory.

Working Memory Model

• Baddeley and Hitch proposed a model with three components:
  • Central executive: controls the flow of information.
  • Phonological loop: processes auditory information.
  • Visuo-spatial sketchpad: processes visual information.
• Episodic buffer: holds together different parts of our current perception or thought.

Memory Encoding

• The depth of processing influences memory strength.
• Deeper processing, such as semantic processing, leads to better encoding.
• Craik and Lockhart's levels of processing theory emphasizes the importance of elaborative rehearsal.

Memory Retrieval

• Retrieval involves reactivation of encoded information and associated schemas.
• Each retrieval can revise memory based on current schemas.

Effective Study Strategies

• Minimize distractions and multi-tasking.
• Actively engage and take notes during lectures.
• Link new knowledge to existing knowledge.
• Organize information.
• Generate your own study materials.
• Space learning episodes and use interleaving.
• Create retrieval cues.
• Practice retrieval.

Language Hierarchy

• Language is organized hierarchically, with phonemes, morphemes, syntax, and semantics.

Phonemes

• Basic units of sound that carry meaning.
• Languages differ in their sets of phonemes.
• Changing a phoneme can change the meaning of a word.

Morphemes

• Smallest units of language carrying meaning.
• Include words, prefixes, and suffixes.
• Content morphemes carry semantic information.
• Function morphemes have a grammatical role.

Syntax

• The structure of language.
• Rules for ordering words are learned implicitly.
• Cued by word order and function words.

Semantics

• The meaning of language.
• Relies on content words.
• Involves mapping words onto mental concepts.

Broca's Aphasia

• Characterized by difficulty processing syntax.
• Damage to Broca's area, located in the left hemisphere, especially the frontal lobe.

Emotions

• Discrete models categorize emotions into basic, blended, social, intellectual, and homeostatic categories.
• Dimensional models describe emotions based on valence, arousal, and motivation.

Basic Emotion Theories

• Darwin suggested that basic emotions are evolutionarily preserved and adaptive.
• Ekman's definition of basic emotions includes:
  • Distinctive universal signals.
  • Distinctive physiology.
  • Distinctive subjective experience.
  • Automatic appraisal.
  • Distinctive universal triggers.
  • Presence in other primates.
  • Presence in infants.

Psychological Constructionist Theories

• Emotions emerge from our interpretations of events and our physiological responses.
• Emotions are not pre-defined but constructed based on experiences and context.

Explore the mechanisms behind inhibitory signals and action potentials in neurons. This quiz covers topics such as resting membrane potential, ion movement, and the thresholds for neuronal firing. Test your knowledge and understanding of these fundamental concepts in neuroscience.