Week 2 - topic 1 Flashcards
Central nervous system
contains the brain and spinal cord
- motor nerves allow actions to be completed, triggered by the central nervous system
Peripheral nervous system
contains the nerves and most sensory organs
- sensory nerves relay sensory information towards the central nervous system
Nerves
- bundles of individual neurons contained within a protective membrane.
- They act a little bit like an electrical cable sending messages to and from the CNS to the rest of the body
- sensory neurons, motor neurons and internneurons
Parts of a neuron
The neurons of the nervous system are the parts that do the talking (information transmitting).
Neurons normally contain the following elements:
- Soma (Cell Body)
- Dendrites
- Axon
- Terminal Buttons
Soma
- cell body
- Contains the nucleus of the cell and the machinery involved in the life process of the cell.
- Soma shape varies in different neuron types.
Membrane
- Made of Double layer of lipid (fatlike) molecules
- Protein molecules embedded in membrane
- Substance detectors and Security Guards
- Transporting substances in and out of the cell
Cytoplasm
- Jelly-like substance that fills the space surrounded by the membrane including the soma
- Contains organelles
Nucleus
An organelle
- Contains the chromosomes
- Chromosomes consist of DNA
- Genes contain recipes for individual proteins
- Proteins important for structure and function
- > Serve as Enzymes
Mitochondria
An organelle
- Extract energy from nutrients
- Produce a chemical called Adenosine Triphosphate (ATP)
Dendrites
Dendrites help individual neurons talk with one another
Neural messages
Neural messages are transmitted from neuron to neuron across the synapse (synaptic cleft).
*look up image
Message = action potential
Axon
Long tube that carries information from the soma of a neuron to it’s terminal buttons
Axoplasmic transport
- Items are moved around the cell via axoplasmic transport
- There are two types of axoplasmic transport:
- > Anterograde transport: movement from cell body to terminal buttons
- > Retrograde transport: movement from the terminal buttons to the cell body
Internal structure of neuron
*look up image
Microtubules
- bundles of protein filaments arranged in a hollow core
- train tracks to propel substances down axon
- to track and transport proteins for axoplasmic transport
Myelin sheath
- fatty substance that works as an insulator of the action potential
- stop message information being lost
Terminal buttons
Located at the end of an axon
Secrete a chemical into the synapse = neurotransmitter
Supporting cells in the nervous system
- neurons are roughly half of the nervous system
- There are lots of supporting cells in the nervous system (NS).
- The NS needs supporting cells because neurons have to be constantly supplied with nutrients and oxygen by the other cells in the NS to stay alive.
Glial cells
Glial Cells (means glue in Greek). (neuroglia)
- supporting cell
- Help hold neurons in place and control supply of nutrients + some chemicals used in neuronal communication
- Insulation - make sure messages don’t get scrambled
- Destroy and remove dead neurons
Types of glia in CNS
Astrocytes (star cells)
Oligodendrocytes
Microglia
Astrocytes
- star shaped glial cells
- Provide nutrients and other substances to neurons
- Regulates chemical composition of extracellular fluid (fluid surrounding neurons)
- take up and release substance to ensure balance is maintained in cellular fluid
- Surround synapses to ensure good communication between neurons
- Clear up debris from dead neurons = phagocytosis
Phagocytosis
- process of cell engulfing and digesting dead cells and debris
Oligodendrocytes
- Provide support to axons and produce the myelin sheath that surrounds axons and insulates them
- Nodes of Ranvier = naked portion of myelinated axon
Microglia
- are very small glial cells involved in phagocytosis and help protect the brain from invading microorganisms.
- important for inflammatory response in response to brain damage
- form part of brains immune system
Supporting cells in the peripheral nervous system
- The peripheral nervous system also contains supporting cells called Schwann Cells.
- They are similar in function to the oligodendrocytes in the CNS.
- Schwann cells produce myelin that cover most axons in the PNS. Just like the CNS, the myelin is segmented in the PNS.
- Each segment of myelin in the PNS is a single Schwann cell, wrapped entirely around the axon many times
- The chemical composition of myelin in the PNS is different to that of the CNS. Clinically, this is important for the condition multiple sclerosis (MS). It is an autoimmune disease that occurs to myelin in the CNS and not the PNS
The blood brain barrier
- The Blood Brain Barrier (BBB) is a barrier exists between the blood and the fluid that surrounds the cells of the brain.
- Selectively Permeable
- The main function of the BBB is to help regulate the composition of the fluid surrounding cells (extracellular fluid) in the brain.
How does the BBB keep the balance?
- Throughout most of the body, cells that line the smallest blood vessels are loosely packed
- Gaps between cells allows substances to move between the blood and the fluid that surrounds cells of the body
- In the CNS there aren’t gaps between the cells that line the smallest blood vessels
- Many substances cannot leave the blood and enter the brain
- > Tightly packed cells = BBB
Structure of BBB
- The BBB isn’t uniform throughout the CNS.
- BBB is thinner at the area postrema (initiates vomiting).
- this is so neurons can easily detect toxic substances in blood and imitate vomiting if you have been poisoned
- composition of extracellular fluid must be regulated otherwise communication in brain can be thrown off
