Nervous System 1- Cells and Transmitters Flashcards
How much of the oxygen in the blood system does the brain use
21%
What are the 2 main components of the nervous system
- CNS 2. Peripheral: Somatic and Visceral
What does the somatic part of the peripheral nervous system control
The musculoskeletal system
What does the visceral part of the peripheral nervous system control
The body’s organs (autonomic nervous system)
What is the CNS composed of
The brain and spinal chord
What are the key parts of a neurone
Nucleus, dendrites, cell body (soma), axon
What is a neurone
A nerve cell
What are the two types of axons
- Myelinated fibre
- Unmyelinated fibre
What is the function of dendrites
To make/ recieve contact from otehr neurones
What is the end part of a neurone called
Axon terminal
What is an axon composed of
Schwann cells
Label the bottom diagram
My= myelinated sheath
A = axon
N = Schwann cell
What happens if Schwann cells in an axon don’t have myelinated sheaths
There is slower conduction of action potential
- What is the axon terminal of the first axon called?
- What is the axon terminal of the secon axon called?
- What is the name of the gap between the two axons
- Presynaptic axon
- Postsynaptic axon
- Synapse (synaptic cleft)
What is a synapse
A gap in between two neurones so cells can commincate with one another
What are the ways in which neurones can vary
(Colin Dendle Ate Ants Surprisingly Smoothly)
- Cell body (soma)- size and shape
- Dendrites- number, branching and length
- Axon- length, diameter, branching
- Axon- myelinated or unmyelinated
- Synaptic terminals- number/ structure
- Synaptic transmission- chemical or electrical
What does the morphology of a neurone reflects
The morphology (size and shape) reflects the function of the neurone
A neurotransmitter is a chemical that is:
(Some Rats Bite Reindeer)
- Synthesised by a presynaptic neurone
- Released into the synaptic cleft
- Binds to a receptor on the postsynaptic neurone
- Either excites or inhibits the postsynaptic neurone
What is a neurone required to do?
(5 things)
- To be stimulated by a neurotransmitter released by another neurone
- To respond to the stimulus, either by being excited or inhibited
- To convey a message, via an action potential, to its terminal
- To release a neurotransmitter from the terminal which will stimulate another neurone (or muscle cell)
- To inactivate the neurotransmitter that it has released
What are the two most common inhibitory neurotransmitters?
GABA and Noradrenaline
What are the two most common excitatory neurotransmitters?
Acetlycholine and Glutamate
How are neurotransmitters synthesised
- Rough ER produces precursor peptide released in ribosome
- Ribosome fuses with golgi apparatus
- Active peptide neurotransmitter is produced
- Released from golgi apparatus in a secretory granule
- Precursor molecule binds with a specific enzyme which produces a neurotransmitter contained within a transporter protein
What does the shape of a neurone depend on
It’s cytoskeleton (type of protein filament)
What type of neurones do actin filaments produce
Little filaments (5nm)
What type of neurones do intermediate filaments produce
Give the axon a long cylindrical shape
What type of neurones do tubules produce
They are slightly bigger and have a vital function in axonal transport
What are the two types of axonal transport
Orthograde
Retrograde
Decribe orthograde transport
Molecules / sub-cellular organelles move from cell body to terminal.
2 speeds: Fast (100-400mm/day) or slow (0.25-0.5mm a day)
What motor is used in orthograde transport
Kinesin
Describe retrograde transport
From terminal to cell body
50-200mm/day
What motor is used in retrograde transport
Dynein
Give an example of retrograde transport
Once damage occurs and is sensed by terminal of the cell body molecules go back up the axon to the nucleus to trigger proteins needed for repair
What is exocytosis
Fusion and release of content
Describe transmitter release at a synapse
- Not random
- Movement of vesicles towards presynaptic axon is controlled by action potentials (influx of Ca2+)
- Neurotransmitter is released
- Neurotransmitter is recyled once it has exerted its effect
Describe the energy supply of neurones
- All of the events in neurotransmitter synthesis and release require energy
- Neurones need to generate ATP constantly
- Protein synthesis uses the most energy- blood supply vital
In 1mm3 of cerebal cortex it is estimated that there are
- 100,000 cells (neurones, neuroglia, endothelial cells)
- 4 kilometers of axon
- 500m of dendrites
- 1,000,000 synpases
This is why so much energy is needed
What is the classification name for other types of cells in the CNS apart from neurones
Neuroglial cells
How many more neuroglial cells are there than neurones in the CNS
10 x
What are the 3 types of neuroglial cells
- Oligodendrocytes
- Astrocytes
- Microglia
What do oligodendrocytes do
Form myelin sheaths for several axon
What do astrocytes do
- Control K+, glutamate and Ca2+ in the extracellular space (take up substances if too much to prevent damage as concentrations must be kept constant)
- Important roles in development and synapse formation
- Important roles in the blood-brain barrier and in local blood flow (dilate blood vessels locally if active/ constrict if not active)
What do microglia do
Respond to injury of the CNS:
- Resting microglia (protein aggregates, proinflammatory signals)
- Microglia migrates
- Fully activated microglia
