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Science Nervous Tissue (Synapses (Chemical Transmission across the…
Science
Nervous Tissue
CNS
Brain
Spinal Cord
Non-mylinated cells
Longer myelinated axons
Neurons
Facilitiate nerve impulses (ie Action Potential)
Across membrane
Parts
Soma = Large Cell Body
Dedrites = Small projects from soma
Axon = Long tail from som signal is sent along
Axon Terminal = End of axon
Between Axon Terminal and denrites of the next neuron is
synapse
Action Potential = Nerve impule
Neurons bundled together to form nerves
Action potentials trigger
Neurotransmiters
to release across a synapse
Bind to pot Synaptic-receptors
Continue nerve implse
Resting Potential and Action Potential
Resting potential
Neuron not transmitting
Transporting Sodium/Potassium
Maintains polarity
Three sodiums out
Two Potssiums in
Active transport
Requires ATP (energy)
Sodium/Potassium Pump
Gated Sodium Ion Channels closed
-70 mV
Action Potential
Stimulated by receptor cell or another neuron
Action potential generated
Neuron always ready to conduct a impulse
Negative fluid of inside (relative)
Correct channels open and potential passes down cell
Electriacel potntial from ions moving across neuron cell membrane
Depolerisation
Wave of depolerisation spreads down axon
Triggers some voltage depenent sodium gates to open
Sodium Ions pore in
+40 mV reached
Sodium gates close and Potassium gates open
Polerisation returns
-50 mV reached opens up other sodium cells
#
Myelinted cells / Saltaory Conduction
Schwnn cells
Thick
Lipid
Wrap around axon
Slaltory Conduction occurs only in Myelinted cells
Increases speed of conduction
#
Node of Ranvier - Mylinted Sheth
Inbetween Swann cells
Ion exchnge occurs here
Saltaory Conduction
Sodium Ions entering Axon displace potassium ions down axon
Potassium Ions reach next node of Ranvier - decreasing depolerisation to -50mV
Triggers Sodium Channels to open
Triggers next Node of Ranvier to begin depolerisation
Only small part of Axon used - Less ATP used, fewer IONS exchanged
Speed of an action potential
Factors
Diameter
Myelination of Neuron
Number of synapses involved
Synapses
End of neuron
Next Neuron = Effector cell
Neurotransmitters diffuse across the synapse
Intiate action potential on dendrite on other Neuron
Parts
Synaptic bulb
End of pre-synaptic neuron
Contains many Mitochondria
Needed for ATP
Neurotransmitters
Stored in vesicles in Synaptic bulb
Vesicles fuse with surface to release neutrotransmitters
Voltage-gated calcium ion channel
Common Neurotransmittor
Acetylcholine - most common
Released by exocytosis
Diffuse across the cleft
Bind to receptor sites
Sodium Ion channels
Cholinergic synapses
Chemical Transmission across the synapse
Action potential arrives at synaptic bulb
Calcium channels open
Calcium ions diffuse into neuron(down concentration gradient)
Calcium moves synaptic vessels towards presynaptic membrane
Vesicles fuse into membrane
Release Neurotransmitters
Neurotransmitters defuse across synaptic cleft
Synaptic delay
Neurotransmittor binds to postsynaptic cell
receptors
Neurotransmitters open sodium channels in membrane
Creates ESPS (Exitatory Post Synaptic Potential)
Membrane more receptive to incoming signals
Threshold reached, action potential generated
Neutrotransmitters excite cell
Enzymes act on Neurotransmitters and break them down once it has acted on the Membrane
Electroencephalograph (EEG) test
Looks at the activity of the brain cell
Nerve impulses traveling creates electrical signals
Can be detected bia detectors attached to a persons skull
Graphical results
See if there is an abnormality
Parkinsons disease
Not able to produce
dopamine
naturally
Helps smooth and normal movement
L-Dopa used to replace dopamine
Serotonin is another neurotransmitters that might need to be replaced with a drug if in low supply
Symptoms
Slow Movement
Tremors when moving
Speech problems
Poor balance