Brain Structure and Function

Brain Navigation Using Neuroanatomy Terms

• Directional Terms:

  • Dorsal (top/superior) vs. Ventral (bottom/inferior)

  • Rostral (front/anterior) vs. Caudal (back/posterior)

  • Medial (toward the midline) vs. Lateral (away from the midline)

• Planes of View:

  • Coronal (Frontal Plane): Divides brain into front & back halves.

  • Sagittal Plane: Divides brain into left & right halves.

  • Horizontal (Transverse Plane): Divides brain into top & bottom.

Functions of Major Brain Areas

• Frontal Lobe: Decision-making, planning, voluntary movement (motor cortex), personality.

• Parietal Lobe: Sensory processing, spatial awareness, touch perception.

• Temporal Lobe: Auditory processing, memory (hippocampus), language (Wernicke’s area).

• Occipital Lobe: Vision processing (primary visual cortex).

• Cerebellum: Coordination, balance, fine motor control.

• Brainstem: Vital functions (breathing, heart rate, reflexes).

Multipolar Motor Neuron (Structure & Function)

Drawing Components:

• Dendrites: Receive input from other neurons.

• Cell Body (Soma): Processes information.

• Axon: Transmits electrical signals.

• Axon Hillock: Where action potential initiates.

• Myelin Sheath: Increases signal speed.

• Nodes of Ranvier: Gaps in myelin for saltatory conduction.

• Axon Terminals: Release neurotransmitters to the next neuron/muscle.

Function:

• Transmits motor signals from CNS to muscles (efferent neuron).

IPSPs, EPSPs, Summation, and Action Potentials

• EPSPs (Excitatory Postsynaptic Potentials): Depolarize the neuron (Na+ in), increasing chance of action potential.

• IPSPs (Inhibitory Postsynaptic Potentials): Hyperpolarize the neuron (Cl- in or K+ out), decreasing chance of action potential.

• Summation:

  • Spatial Summation: Multiple synapses firing at once.

  • Temporal Summation: One synapse firing rapidly over time.

• Action Potential Process:

  1. Resting Potential: -70mV

  2. Depolarization: Na+ influx

  3. Repolarization: K+ efflux

  4. Hyperpolarization: Overshoot of K+

  5. Return to Resting Potential

Functions of Major Neurotransmitters

• Acetylcholine (ACh): Muscle contraction, memory (Alzheimer’s linked to ACh deficits).

• Dopamine (DA): Reward, movement (Parkinson’s & schizophrenia).

• Serotonin (5-HT): Mood, sleep, appetite (linked to depression).

• GABA: Inhibitory neurotransmitter (reduces neural activity, anxiety regulation).

• Glutamate: Main excitatory neurotransmitter (learning, memory).

• Norepinephrine (NE): Alertness, arousal, fight-or-flight.

Key Case Studies & Their Impact

• Phineas Gage: Damage to prefrontal cortex → Personality & decision-making changes.

• HM (Henry Molaison): Hippocampus removal → Anterograde amnesia (new memories lost).

• Broca’s Patient (“Tan”): Left frontal lobe damage → Speech production loss (Broca’s area).

• Split-Brain Patients: Corpus callosum severed → Lateralization of brain functions studied.

Neuropsychological Techniques & Their Importance

• MRI & fMRI: Structural & functional imaging of the brain.

• EEG: Measures electrical activity (useful for sleep & epilepsy studies).

• TMS (Transcranial Magnetic Stimulation): Temporary activation/inhibition of brain areas.

• PET Scan: Tracks metabolic activity using radioactive glucose.

• Lesion Studies: Examining damage effects to understand function.

Why Many Techniques Are Needed:

• No single method provides a complete picture.

• Some techniques give structural details, others show function.

• Different resolutions and levels of invasiveness.

Ethics in Neuroscience Research (IACUCs, IRBs, & 3 R’s)

• IACUC (Institutional Animal Care and Use Committee): Oversees ethical treatment of animals in research.

• IRB (Institutional Review Board): Protects human subjects in research (informed consent, minimizing harm).

• 3 R’s in Animal Research:

  • Replacement: Use alternatives when possible (e.g., computer models).

  • Reduction: Use the fewest animals necessary.

  • Refinement: Improve procedures to minimize distress.