psych 261 lecture 2

The Heyday of Neurosurgery

• Neurosurgery practices date back to 300 BCE, with early forms of dissection.
• The first psychosurgery was performed by Dr. Gottlieb Burckhardt in 1891.
• Antonio Egas Moniz, alongside Almeida Lima, performed frontal leucotomies in the 1930s, receiving a Nobel Prize for this work.
• Watts, Freeman, and Scoville were involved in the development and experimentation of psychosurgery, influencing mental health care in the 1930s.

The Split Brain

• Commissurotomy involves severing the connections between the right and left cerebral hemispheres.
• The first human commissurotomy occurred in 1940, with more prevalent procedures in the 1960s.
• Gazzaniga and Sperry (1967) observed little impact on daily behavior, temperament, or intellect following commissurotomy.
• The procedure sometimes resulted in "alien hand" syndrome, where the hands act independently and in conflict.

Lateralization of Function

• Speech is often localized to the left hemisphere.
• Cerebral hemispheres present with asymmetry.
• There is specialization in each hemisphere.

Cells of the Nervous System

• The brain comprises ~170 billion cells (~86 billion neurons & ~84 billion glia).
• Various brain regions demonstrate different ratios of neurons to glia cells.

Types of Neurons

• Neurons exhibit diverse shapes, corresponding to their distinct functions.
• Types include multipolar, bipolar, and unipolar neurons.
• Different neuron shapes relate to distinct functional roles.

The Neuron

• A neuron consists of the soma, dendrites, axon, and axon terminal (terminal button).
• Dendrites receive signals, the axon transmits them, and the axon terminal transmits signals to another cell.

The Soma

• The soma is the cell body of a neuron.
• It includes rough endoplasmic reticulum, lysosomes, Golgi apparatus, mitochondria, chromatin (DNA), nucleolus, and nuclear membrane.

Dendrites

• Dendrites increase the surface area for signal reception by possessing dendritic spines.
• These spines increase the number of connections neurons have with other neurons.
• Dendritic spines have dendritic shafts and dendritic heads.

Dendritic Spines

• Dendritic spines are crucial for synaptic transmission and plasticity.
• They have diverse shapes and sizes, directly relating to the neurons' function.
• They contain postsynaptic densities of specialized proteins in the spine heads where signals are received.

Semipermeable Membrane

• Cell membranes are semipermeable, allowing certain substances to pass while restricting others.
• Proteins and other specialized molecules regulate which substances pass through the membrane and when.

The Synapse

• The synapse is the junction between two neurons, enabling communication.
• Communication across the synapse involves chemical signaling using neurotransmitters.
• Chemical signals pass across the synaptic cleft between presynaptic and postsynaptic terminals.

Fast Axonal Transport

• Axon terminals communicate with other neurons by releasing chemicals which travel across the gaps between neurons.
• Kinesin uses ATP to transport cargo along microtubules from the soma to the axon terminals.
• Retrogade transport moves cargo from axon terminals to the soma (dynein).

Axon Terminal

• The axon terminal contains specialized structures for neurotransmitter release.
• Mitochondria in the axon terminal provide energy as they are responsible for various processes in the axon terminals.
• Neurotransmitters travel along specialized vesicles to specific receptors on the postsynaptic cell.

The Tripartite Synapse

• The tripartite synapse incorporates an astrocyte, the pre-synaptic neuron, and the post-synaptic neuron.
• Astrocytes play roles in modulating synaptic transmission and activity.
• It's imperative to consider this tripartite model in studies examining neuronal interactions, as well as in disease states.

A Common Scenario

• Communication between neurons happens chemically.
• Axons conduct electrical impulses, which convert to chemical signals at the synapse.
• Electrical signals enable communication between neurons.

Astrocytes

• Astrocytes are a type of glial cell that supports neurons.
• They help form the blood-brain barrier.
• Astrocytes facilitate the transport of nutrients and other molecules among neurons and blood vessels.

Synchronization of Multiple Synapses

• Astrocytes are crucial in synchronizing the activity of numerous synapses.
• They form interconnected networks that synchronize presynaptic and postsynaptic activity.

Types of Axons

• Efferent axons carry signals away from a region.
• Afferent axons carry signals toward a region.