Chapter 2 (PART 1) - The Neural Basis for Cognition - Neurons - PSYC340

Chapter 2 for PSYC340 exam 1 split into two parts, this part is all about neurons

Complexity

The brain and nervous system are very complex

Integration

The brain integrates information from all senses. Nerves connect with at least 10,000 other nerve cells

Adaptability

The brain has to adapt to changing environment (ex. the brain uses different parts when walking to class vs being in class)

Neuroplasticity

Brain’s capacity for physical changes in response to experience

The brain’s ability to change, especially during childhood, by reorganizing after damage or by building new pathways based on experience

Developing new connections with new experience

Who first demonstrated Neuroplasticity, and what did she use to do so?

Dr. Mariam Diamond and colleagues at UC Berkeley

Caged rats in a stimulating (fun) vs unstimulating (nothing to do) environments

Brain matter of the rats in the stimulating environments was thicker (it developed more)

What are the two types of brain cells?

Glial Cells

Neurons

Glial cells

Cells that support, nourish and protect neurons

Physically and chemical buffering neurons

Removes dead neurons

Gives oxygen to neurons

Neurons

Cells specialized to receive and transmit information in the nervous system (Nerve cells)

What are the basic parts of a neuron?

Dendrites

Cell body (soma)

Axon

Myelin Sheath

Node of ranvier

Axon terminals

Dendrites (parts of a neuron)

Branch like protrusions at the top of the neuron which detect incoming signals.

Cell body/soma (parts of a neuron)

Contains the nucleus and cellular machinery

Axon (parts of a neuron)

Thin fiber that connects neurons so they can communicate. Transmits signals to other neurons via action potential

Myelin Sheath (parts of a neuron)

Covers the axons, insulates them and facilitates neural communication

Nodes of ranvier (parts of a neuron)

Refer to the gaps in the myelin sheath

Axon terminals (parts of a neuron)

Connect to other neurons

What are the three types of neurons?

Sensory (afferent) neurons

Motor (efferent) Neurons

Interneurons

Sensory (afferent) Neurons (types of neurons)

Transmit information from environment to central nervous system (CNS)

Any physical sensation

Takes information from the environment and body and sends it to our brain

Motor (efferent) Neurons (types of neurons)

Transmits information from the central nervous system (CNS) to muscles/organs/glands

Interneurons (types of neurons)

Connect the brain regions

ex. can enable connection between afferent and efferent neurons

Enables us to do higher order cognitive functions

Action potential (communication within neurons)

Electrical signals that enable communications within neurons

If the stimulus reaches threshold, an action potential is fired and propagates (moves) down the axon

The process of action potential

In response to a signal, the soma end of the axon becomes depolarized

The depolarization spreads down the axon. Meanwhile, the first part of the membrane repolarizes. Because the Na channels are inactivated and additional K channels have opened, the membrane cannot depolarize again.

The action potential continues to travel down the axon.

Depolarizing (Process of action potential)

Small gates in the cell wall open, allows fluid containing positive charged ions flows in and stops change differential.

Repolarizing (process of action potential)

Changing back from positive ions to negative ions.

All-or-none law

The strength in which a neurons fires is independent to the strength of the stimulus. If the stimulus exceeds the threshold level, then the neuron fires (all). If it doesn’t reach the threshold, it doesn’t (none).

Either the stimulus fires or it doesn’t

If the signal is sent, it is always the same magnitude (neurons only have one strength they can send)

How to measure action potential

The size is not measured; size remains consistent

The rate of firing is what’s measured (how intense the stimulus is)

Low intensities: slow firing

High intensities: fast firing

Neurotransmitters (communication between neurons)

Chemical released by one neuron to communicate with another neuron

Synapse (communication between neurons)

The region where axons of one neuron and dendrites of another come together.

Presynaptic neurons (communication between neurons)

Neuron that releases the neurotransmitters

Postsynaptic neuron (communication between neurons)

Neuron that receives the neurotransmitters

Reuptake (communication between neurons)

Reabsorption of a neurotransmitter by the presynaptic neuron

Excitatory effects (neurotransmitters)

Encourages the next neuron to fire (ex. serotonin)

Inhibitory effects (neurotransmitters)

Keeps the next neuron from firing (ex. GABA)

GABA (Inhibitory effects)

The brains break petal

Keeps neurons from firing to neurons we don’t want it to go to

Neural representations

How our brain represents different objects, experiences, memories, cognitive functions

Feature detectors (Neural representations)

Neurons that fire only to specific qualities of stimuli

Orientation, movement, length

Found in early stages of visual processing

Sensitive to lines and combinations of lines

Sensory coding (Neural representations)

How neurons represent characteristics of the environment

Specificity coding (sensory coding)

Representation via single dedicated neurons

ex. a neuron for your pet, neuron for your mom

Sparse coding (sensory coding)

Representation via a pattern of firing across a small number of neurons

ex. the area around you when walking to class

Distributed coding (sensory coding)

Many neurons working together to encode information