Lecture 1: Overview of Neurophysiology & Cells of the Nervous System

neurophys

Explain the hierarchy Cells → Circuits → Systems → Function.

• Cells = neurons and glia

• Circuits = interconnected neurons

• Systems = interacting brain regions/networks

• Function = behavior/output

• Behavior emerges from interactions across all levels.

What distinguishes neurons from other somatic cells?

• Diverse morphology

• Bioelectrical properties

• Specialized synaptic communication

• Together enable information processing and transmission

Describe the structure and function of a neuron.

Dendrites → Soma → Axon hillock → Axon → Axon terminals

• Dendrites receive input

• Soma integrates signals

• Hillock decides whether AP fires

• Axon conducts AP

• Terminals release neurotransmitter

Why is the axon hillock the computational region of the neuron?

• Receives summed EPSPs and IPSPs

• Integrates synaptic input

• Generates AP if threshold depolarization is reached

• Converts synaptic input into neuronal output

Explain myelin and saltatory conduction.

• Myelin electrically insulates axons

• Nodes of Ranvier contain ion channels

• AP appears to jump node-to-node

• Increases conduction speed and efficiency

Compare structural neuron classes.

• Unipolar

• Bipolar

• Multipolar

• Pseudounipolar

• Anaxonic

Different structures support different signaling functions.

Compare sensory, motor, and interneurons.

Sensory (afferent): detect stimuli

Motor (efferent): produce responses

Interneurons: connect and process information within CNS

Why does the nervous system contain many neuronal types?

• Specialized computations

• Diverse connectivity

• Efficient information processing

• Different signaling and integration properties

Compare CNS glial cells.

• Astrocytes

  • BBB

  • Neurotransmitter recycling

  • Ionic balance

  • Synapse support

  Oligodendrocytes

  • CNS myelin

  Microglia

  • Immune defense

  • Phagocytosis

  Ependymal cells

  • Produce/circulate CSF

  • Line ventricles

Compare Schwann cells and satellite cells.

• Schwann

  • PNS myelin

  • Repair support

  Satellite

  • Surround ganglia

  • Regulate local neuronal environment

What is the blood-brain barrier and why is it important?

• Specialized barrier between blood and CNS

• Maintains neural environment

• Restricts harmful substances

• Astrocytes contribute to its maintenance

Compare oligodendrocytes and Schwann cells.

• Oligodendrocytes = CNS myelin

• Schwann cells = PNS myelin

• One oligodendrocyte can myelinate multiple axons

• One Schwann cell myelinates one axonal segment

Describe microglia.

• CNS immune cells

• Hematopoietic origin

• Ramified (resting)

• Amoeboid (active)

• Remove pathogens and debris

Describe ependymal cells and glial stem cells.

• Ependymal cells line ventricles and central canal

• Produce/circulate CSF

• Glial stem cells can self-renew

• Can differentiate into neurons and glia

Compare white matter and gray matter.

Gray matter

• Cell bodies

• Dendrites

• Synapses

White matter

• Myelinated axons

• Oligodendrocytes

White appearance results from myelin.

Describe transmission at a chemical synapse.

• AP reaches terminal

• Ca²⁺ channels open

• Ca²⁺ influx

• Vesicle fusion

• Neurotransmitter release

• Receptor activation

• Postsynaptic response

What is a neural circuit and why are circuits important?

• Network of interconnected neurons

• Transform inputs into outputs

• Behavior emerges from circuit activity rather than individual neurons

Compare intracellular and extracellular recording.

Intracellular

• Measures membrane potential directly

• High detail

Extracellular

• Measures APs outside cells

• Can record many neurons

Compare calcium imaging and optogenetics.

Calcium imaging

• Measures neural activity indirectly via calcium

Optogenetics

• Controls activity with light-sensitive proteins

Combined: manipulate and observe circuits simultaneously.

Compare EEG, MEG, fMRI, and CT.

• EEG

  • Electrical activity

  • Excellent temporal resolution

  MEG

  • Magnetic activity

  • Excellent temporal resolution

  • Better localization than EEG

  fMRI

  • BOLD signal

  • Excellent spatial resolution

  CT

  • Structural imaging

  • Fast and useful in emergencies

Explain MS using cell biology.

• Immune-mediated attack on oligodendrocytes/myelin

• CNS demyelination

• Slowed or blocked AP conduction

• Causes neurological deficits (e.g., visual impairment, sensory symptoms)

• Often relapsing-remitting