NS BIOL 105 S25 Terms for Exam 2

Exam Overview

• Focus on key concepts related to action potential, auditory, and visual systems.

• Important areas include:

  • Brain regions: amygdala and hippocampus.

  • Glial cells and split-brain patients.

Auditory System

Ear Structure

• Outer Ear:

  • Function: Picks up sound waves from the environment.

• Middle Ear:

  • Function: Conveys and amplifies sound waves.

• Inner Ear:

  • Function: Translates sound waves into nerve impulses.

Sound Characteristics

• Loudness:

  • Definition: Psychological aspect related to the magnitude of sound.

• Pitch:

  • Definition: Psychological aspect related to frequency of sound.

• Amplitude:

  • Definition: Magnitude of displacement in a sound pressure wave.

• Frequency:

  • Definition: Number of times per second that pressure changes repeat.

Sound Localization Cues

• Interaural Time Difference:

  • Time difference in sound reaching both ears.

• Interaural Level Difference:

  • Difference in sound intensity reaching both ears.

• Doppler Effect:

  • Change in wavelength/frequency as sound source moves.

Visual System

Photoreceptors

• Rods:

  • Enable black and white vision; function in dim light.

• Cones:

  • Enable color vision; function in bright light; three types exist.

Visual Processing

• Phototransduction:

  • Process of light absorption and response creation by cells.

• Receptive Field:

  • Region of sensory space that triggers neuron firing.

Maps in Sensory Processing

• Map:

  • Projection of axon organization reflective of body/organs.

• Tonotopic Map:

  • Frequency mapping from cochlea in auditory structures.

• Somatotopic Map:

  • Sensory pathways arranged according to body organization.

• Retinotopic Map:

  • 2D representation of retinal image in primary visual cortex.

Glial Cells

• Glia:

  • Support cells for neurons providing protection and support.

• Types of Glial Cells:

  • Astrocytes:

    • Star-shaped; regulate ionic environment and neurotransmitter reuptake; most abundant.

  • Oligodendrocytes:

    • Myelin sheath producers in the CNS.

  • Schwann Cells:

    • Myelin sheath producers in the PNS.

  • Microglia:

    • Repair damaged neural tissue; function as immune cells.

Action Potential Basics

• Ion Channel:

  • Integral membrane proteins that allow selective ion flow.

• Action Potential:

  • Electrical signal propagating along axons/muscle fibers.

• Ion:

  • Charged atom or molecule.

• Synaptic Bouton:

  • Swelling at axon end, specialized for neurotransmitter release.

Receptor Types

• Receptors:

  • Proteins on post-synaptic membrane sensing neurotransmitters.

• Ionotropic Receptors:

  • Directly linked to ion channels; fast response.

• Ligand Gated Ion Channels:

  • Opened by ligand presence; controls ion flow.

• Metabotropic Receptors:

  • Indirectly linked to ion channels; slower response via GPCRs.

Action Potential Characteristics

1. Self-regenerating.

2. All-or-none voltage change.

3. Initiates at axon hillock and propagates.

4. Induces synaptic transmission.

Neurotransmitters Overview

• Excitatory Neurotransmitters:

  • Depolarizes neurons, e.g., Glutamate (allows Na+ and Ca++ influx).

• Inhibitory Neurotransmitters:

  • Hyperpolarizes neurons, e.g., GABA (allows Cl- influx).

• Mechanisms for Neurotransmitter Recovery:

  • Diffusion: Away from the synapse.

  • Reuptake: Neurotransmitter re-enters presynaptic terminal.

  • Enzymatic Destruction: Occurs in cytosol/synaptic cleft.

Common Neurotransmitters

• Acetylcholine (ACh):

  • Excitatory neurotransmitter at motor neuron synapses; significant in the autonomic nervous system.

• Glutamate:

  • Predominant excitatory neurotransmitter in brain.

• GABA:

  • Major inhibitory neurotransmitter.

Neurotoxins and Related Concepts

• Neurotoxin:

  • Substances harmful to nerve tissue.

• Examples include:

  • Tetrodotoxin:

    • Blocks voltage-sensitive Na+ channels, causing paralysis.

  • Atracotoxin:

    • Slows Na+ channel inactivation, causes hyperactivity.

• Excitotoxicity:

  • Neuron death due to excessive glutamate activity; involves elevated Ca++ levels.

  • EAAT2:

    • Transporter clearing glutamate; mutations linked with ALS.

Questions for Understanding

1. Functions of dendrites, soma, and axon?

2. Role of Na+, K+, and Ca++ in action potentials?

3. Definition and propagation of action potentials in myelinated vs. unmyelinated axons?

4. How neurotransmitters can excite or inhibit neurons?