Neuro chapter 1 (class notes)

Neurons

Receive and transmit information

Glia

Exchange chemicals with adjacent neurons.

They do not transmit information over long distances like neurons do.

They support, protect, and nourish neurons.

They are 1/10 the size of a neuron, but they are 10x more numerous than neurons in the brain. So they take up the same total space

Membrane

Separates inside and outside of cell. It's made up of two layers of fat (phospholipids) that float into and out of the cell

Three small, uncharged molecules that move freely across the membrane

Water, oxygen, and carbon dioxide

Four charged ions that pass through protein channels

Sodium, potassium, calcium, chloride

Dendrites

Branching fibers (like a tree). Narrower further from the cell body. Referred to as the information receiver

Axon

Thin fiber. Referred to as the information sender

Soma

The cell body. Contains the nucleus, ribosomes, mitochondria

Presynaptic terminals (end bulbs)

Swelling at tip of axon. This is where the axon releases chemicals through synaptic gap

Afferent neurons

Brings information into a structure (A for Admission)

Efferent neurons

Sends information away from a structure (E for Exit)

S

A

M
E

Sensory

Afferent

Motor

Efferent

Sensory neurons

Sends messages from skin and senses to the brain

Motor neurons

Send messages from brain to muscles

Interneurons

Work in the brain and spinal cord to help process and transmit information

Nucleus

The structure that contains chromosomes

Mitochondria

Provides energy to the cell. Powerhouse of the cell

Ribosomes

Site of protein synthesizers

Endoplasmic reticulum

Network of thin tubes that transport newly synthesized proteins to other locations

Myelin sheath

Covering found on axon that insulates and increases speed of action potential

Nodes of Ranvier

Interruption (gaps) in the myelin sheath. Facilitates rapid conduction of nerve impulses

Saltatory conduction

(jumping) of the action potential from node to node along myelinated axon

Multiple Sclerosis (MS) cause

Loss of myelin which prevents movement of action potentials down the axon

Astrocyte

Star-shaped glia in the CNS

It helps synchronize the activity of axons, enabling them to send messages in waves

It removes waste material that is created when neurons die

Oligodendrocyte

Type of glia in the CNS that is like a lawyer (ligo) and lawyers need a brain and backbone

Surrounds and insulates certain axons in the brain and spinal cord

Builds myelin sheaths around axons in the brain and spinal cord

Schwann cells

Glia in the PNS that are like swans swimming in peripheral ponds

Surrounds and insulates certain axons in the periphery of the body

Builds myelin sheaths around axons in the periphery of the body

Radial glia

Glia in the CNS; radial tires are needed for migrating

Guides migration of neurons *during embryonic development

Guides growth of axons and dendrites *during embryonic development

Microglia

Glia in the CNS; microfiber towel to clean up

Proliferates in the area of brain damage

Removes toxic materials

Blood-brain barrier (BBB)

Made up of endothelial cells in the brain that are so tightly knit molecules can’t pass between them

Keeps most viruses, bacteria, and harmful chemicals out of the brain

Damaged cells in the brain don’t regenerate

It is needed to minimize the risk of brain damage

Some things can slip through like herpes, which will stay in your brain forever

Molecules that can cross BBB passively or freely

• Small uncharged molecules (water, oxygen, carbon dioxide)

• Molecules that dissolve in the fats of capillary walls (lipid soluble) (eg. psychiatric drugs or abused drugs like nicotine, marijuana, or heroin)

Active transport

A protein-mediated process that pumps necessary or useful chemicals from the blood to the brain (eg glucose, amino acids, thiamine/other vitamins, certain hormones)

Nerve impulse

The electrical message transmitted down the axon.

There is an exchange of chemicals between the inside and the outside of the cell

Electrical polarization

The difference in electrical charge between two locations

Concentration gradient

The difference in distribution for various ions between the inside and the outside of the cell

• Sodium is 10x more concentrated outside the membrane than inside

• Potassium is 20x more concentrated inside the membrane than outside

• The outside of the cell is more positively charged

• The inside of the cell is more negatively charged

Selective permeability

Some molecules can pass much more freely through the membrane than others

Molecules that can cross both directions in the membrane at all times

• Oxygen

• Carbon dioxide

• Water

• Urea

Molecules that cross through protein channels in the membrane

• Sodium

• Potassium

• Calcium

• Chloride