Neuroscience: Scientific Process and Neural Communication

Scientific Process

Systematic method for conducting scientific research.

Reductionist Approach

Analyzing brain by breaking it into levels.

Molecular Neuroscience

Study of chemical processes in the brain.

Cellular Neuroscience

Focus on nerve cells and their functions.

Systems Neuroscience

Examines groups of nerves performing functions.

Behavioral Neuroscience

Investigates how systems produce observable behavior.

Cognitive Neuroscience

Studies brain activity related to mental processes.

Observation

Initial step of hypothesizing findings.

Replication

Repeating experiments to ensure reliability.

Interpretation

Analyzing and explaining collected data.

Verification

Reconfirming results through repeated experiments.

Animal Research Importance

Models human brain for accurate neuroscience studies.

Ethical Animal Research

Guidelines ensuring humane treatment of research animals.

Reduction (Three Rs)

Minimize animal use in experiments.

Refinement (Three Rs)

Improve living conditions for research animals.

Replacement (Three Rs)

Use alternatives to animals when possible.

Animal Welfare

Ethical treatment of animals in research.

Animal Rights

Opposition to animal use in research.

Neurons in Human Brain

Approximately 85 billion neurons present.

Golgi Method

Stains neurons using silver chromate technique.

Immunohistochemistry (IHC)

Technique showing protein presence in tissues.

In Situ Hybridization (ISH)

Technique for detecting mRNA in tissues.

Neuron Doctrine

Neurons function as individual units.

Reticular Theory

Neurons form a continuous network.

Neuron Components

Soma, axon, axon terminals, dendrites.

Soma Function

Maintains cell's essential functions.

Axon Function

Transmits action potentials away from soma.

Axon Hillock

Initiates action potentials in neurons.

Axon Terminals

Release neurotransmitters to communicate with targets.

Dendrites Function

Receive signals from other neurons.

Synapses

Connections between neurons for communication.

Neuron Classification

Based on number of neurites.

Unipolar Neurons

Single process extending from the soma.

Bipolar Neurons

Two processes extending from the soma.

Multipolar Neurons

Multiple processes extending from the soma.

Primary Sensory Neurons

Bring sensory information to the CNS.

Motor Neurons

Innervate muscles to produce movement.

Interneurons

Connect other neurons; most abundant type.

Glia Classification

Methods include IHC and ISH techniques.

Astrocytes

Clean neurotransmitters, maintain blood-brain barrier.

Oligodendrocytes

Myelinate multiple CNS neurons.

Schwann cells

Myelinate single PNS neuron.

Ependymal cells

Direct cell migration in brain development.

Microglia

Phagocytes that remove debris and dead cells.

Resting Membrane Potential

Electrical charge difference across neuron membrane.

Typical resting potential value

Typical value is -65mV in neurons.

Sodium-Potassium Pump

Maintains resting potential by moving Na+ and K+.

Equilibrium potential for K+

Calculated using Nernst equation for potassium ions.

Nernst equation

Used to calculate equilibrium potential for specific ions.

Goldman equation

Calculates resting potential considering multiple ion permeabilities.

Threshold phase

Voltage-gated sodium channels open, depolarizing the neuron.

Rising phase

Na+ influx causes rapid depolarization.

Overshoot phase

Membrane potential approaches ENa due to Na+ permeability.

Falling phase

K+ efflux causes repolarization of the membrane.

Undershoot phase

Membrane potential drops below resting potential due to K+.

Absolute refractory period

Na+ channels cannot reopen until membrane repolarizes.

Ionic forces

Determine resting potential through concentration and electrical gradients.

K+ equilibrium significance

RMP is closest to K+ equilibrium potential.

Neurons vs Glia

Neurons focus on communication; glial functions discovered later.

Astrocytes in Parkinson's

Can convert to neurons to combat disease.

Impact of oxygen deprivation

RMP approaches 0 as sodium-potassium pump fails.

Relative refractory period

Hyperpolarized state requiring more current to reach threshold.

All-or-none principle

Action potential fires fully or not at all.

Sodium channel structure

Four domains with six helices each, voltage sensor in S4.

Sodium channel mutations

Altered function can lead to epilepsy or reduced excitability.

Grasshopper mouse adaptation

Mutation allows sodium channel inactivation by scorpion venom.

Inhibiting action potentials

Reducing firing by inhibiting sodium channels.

Action potential propagation

Opening sodium channels triggers sequential depolarization along axon.

Direction of action potentials

Move away from cell body due to closed sodium channels.

Conduction velocity factors

Influenced by axon structure, diameter, myelin, and channels.

Axonal diameter effect

Wider axons conduct action potentials faster.

Saltatory conduction

Nodes of Ranvier regenerate action potentials, myelin prevents current loss.

Neuron physiology determinants

Genetics and functional role influence unique properties.

Adaptation in neurons

Decreased firing rate over time in response to stimuli.

Local anesthetics mechanism

Block sodium channels to prevent action potentials.

Lidocaine interaction

Binds to S6 region, blocking Na+ flow when open.

Multiple sclerosis impact

Demyelination disrupts action potential propagation in nerves.

Remyelination process

Rebuilding myelin sheath using glial cells.

Electrical synapses

Bidirectional ion flow through gap junctions formed by connexons.

Chemical synapses

Unidirectional transmission across a wider synaptic cleft.

Synaptic transmission termination

Mechanisms include diffusion, reuptake, and breakdown of neurotransmitters.

Vesicle fusion mechanism

V-SNARE and T-SNARE proteins bind to facilitate fusion.

Agonists vs antagonists

Agonists mimic neurotransmitter action; antagonists block receptors.

Neurotransmitter-gated channels

Directly open ion channels; G-protein-coupled receptors activate second messengers.

Synaptic integration purpose

Combine inputs to encode information in a neuron.

EPSPs and IPSPs

Contribute to action potential generation in post-synaptic cells.

Spatial vs temporal summation

Spatial combines inputs from different locations; temporal combines over time.

Temporal summation

Combining potentials arriving at axon hillock.

Dendritic length constant

Distance over which voltage decays in dendrites.

Membrane resistance

Resistance to current leaking from the axon.

Internal resistance

Resistance to current traveling down the axon.

Modulator effect

Increases membrane resistance, enhancing length constant.

Neurotransmitter criteria

Criteria to classify substances as neurotransmitters.

Presynaptic synthesis

Neurotransmitters synthesized and stored in presynaptic neuron.

Experimental response

Molecule produces same response when applied experimentally.

Neurotransmitter transporter

Builds concentration of transmitter across membranes.

Nucleus

Origin of release; contains cell bodies.

Tract

Pathway where neurons extend; refers to axons.

Neuropharmacological analysis

Uses agonists/antagonists to study receptor effects.

Ligand binding method

Radioactively labels ligand to study binding locations.