Introduction to Neuroscience

Study Notes

Neuroscience is the study of the nervous system, which consists of the brain, spinal cord, and nerve cells.
The nervous system is composed of two main types of cells: neurons and glia.
Neurons are specialized for communication, while glia provide support for neurons.
The human brain contains approximately 80-100 billion neurons.

The three main parts of a neuron are the dendrites, cell body, and axon.
Dendrites receive chemical messages from other neurons.
The cell body contains the nucleus and other structures, wrapped by a selectively permeable membrane.
The axon is a long, slender process that carries information from the cell body to the terminal buttons.
Terminal buttons contain synaptic vesicles that release neurotransmitters into the synapse.

Motor neurons conduct messages from the brain and spinal cord to muscles and organs.
Sensory neurons carry information from the body and world to the brain and spinal cord.
Interneurons conduct information between neurons in the same area.

Neurons transmit information through electrical and chemical signals.
Spatial summation combines potentials occurring simultaneously at different locations on the dendrites and cell body.
Temporal summation combines potentials arriving a short time apart, from either the same or separate neurons.

When an action potential reaches the terminal button, neurotransmitters are released into the synapse.
Neurotransmitters bind to receptors on the postsynaptic neuron, causing a change in the electrical properties of the neuron.
Reuptake is the process by which neurotransmitters are taken back into the terminal buttons by membrane proteins (transporters).

Excitation is the process by which a neuron is made more likely to fire an action potential.
Inhibition is the process by which a neuron is made less likely to fire an action potential.
Both excitation and inhibition are equally important for proper neural function.

The resting potential is the electrical state of a neuron at rest, with a negative charge on the inside compared to the outside (-70mV).
The resting potential arises from a combination of electrostatic forces, ion concentration gradients, and selective permeability.
Sodium-potassium pumps help maintain the electrical gradient.

An action potential is a brief electrical impulse that travels along an axon and allows one neuron to communicate with another.
The action potential is possible due to the semi-permeable membrane, which maintains chemical and electrical gradients across the membrane.
Depolarization changes the voltage, which may cause voltage-sensitive ion channels to open and allow ionic diffusion.
The action potential is an all-or-none event.

Glia are the other major component of the nervous system, providing support for neurons.
Astrocytes help synchronize the activity of the axon by wrapping around the presynaptic terminal and taking up chemicals released by the axon.
Microglia remove waste material and other microorganisms that could prove harmful to the neuron.
Oligodendrocytes and Schwann cells build the myelin sheath that surrounds the axon of some neurons.
Radial glia guide the migration of neurons and the growth of their axons and dendrites during embryonic development.

Neurotransmitters are chemical substances released synaptically from one neuron that affect another cell in a specific manner.
There are three general categories of neurotransmitters: amino acids, amino acid-derived, and peptides.
Examples of neurotransmitters include GABA, dopamine, norepinephrine, serotonin, and peptides.

The cell membrane is formed from two layers of lipid molecules with proteins "floating" within the bilayer.
The cell membrane is selectively permeable, allowing certain molecules to pass through while keeping others out.