Neural Signaling Flashcards
Pain Perception Receptors
Nociceptors are located on the skin and contain transient receptor potential channels (TRP), which act as receptors for many pain stimuli
Values of Oscilloscope
Resting Potential: -70mV
Depolarization: 30-40mV
Repolarization: -80mV
Summation
Multiple releases of excitatory neurotransmitters combine to cause an action potential, and can combine excitatory and inhibitory neurotransmitters
Inhibitory neurotransmitters counter the excitatory ones so threshold potential is not reached, and threshold potential will only be reached if there are more excitatory than inhibitory neurotransmitters
All or None Principle
Action potential ofthe same magnitude will always occur if threshold potential is reached to open voltage-gated ion channels
If threshold potential is not reached, action potential can not be generated hence neuron will not fire
Inhibitory Synapses
Hyperpolarize (more negative) postsynaptic neuron
Neurotransmitters get released into the synaptic cleft, which causes chloride ions to enter or potassium ions to leave due to opening of ion channels
This makes it difficult for postsynaptic neuron to generate impulse in response to excitation by other synapses in the same postsynaptic cell
Inhibitory neurotransmitters bind to a specific receptor
Basic Components of Neuron
Dendrite: Short-branched fibers that convert chemical information from other neurons into electrical signals
Axon: Elongated fiber that transmits electrical signals to terminal regions for communication with other neurons
Soma (Cell Body): Contains nucleus and organelles where essential metabolic processes occur
Repolarization
After depolarization, voltage-gated potassium channels open and diffuse out of the axon down concentration gradient
The exit of positively charged potassium ions causes the inside of the neuron to develop a net negative charge because Chloride ions are inside which restores potential of membrane
Emergent Property and Consciousness
Emergent Property: A property arising from the interaction of many components in a complex system
Consciousness: The feelings, sensations, thoughts and awareness of oneself and the environment
Depolarization
When threshold potential is reached, voltage-gated sodium channels open
Sodium ions diffuse into the axon down the concentration gradient which reduces membrane potential and causes more sodium channels to open
More sodium ions diffuse into the axon which causes inside of neuron to develop a net positive charge compared to the outside
This results in depolarization as potential is reversed
Synapses
Junctions between neurons and receptor or effector cells
Synaptic Transmission
The conduction of a nerve impulse from the presynaptic to the postsynaptic neuron through the synaptic cleft
Sensory, Relay and Motor Neurons
Sensory detects the stimulus and sends impulse to CNS, where relay neuron takes impulse from sensory and sends it to motor. Motor receives impulse and facilitates response to stimulus
What is Acetylcholine
A neurotransmitter that is largely used at the neuromuscular junction, meaning it’s released by motor neurons and binds to muscle receptors
Formed by combining choline with acetyl group, and is secreted by the presynaptic membrane of the neuron
Acetylcholine binds to the receptor on the post synaptic membrane, and once it has been released from the receptor an enzyme called acetylcholinesterase breaks it down back into choline and acetate
Choline is reabsorbed back into the presynaptic neuron where it’s recycled to form another acetylcholine neurotransmitter
Propagation of Action Potential Along a Nerve Fiber
When a nerve impulse is being self propagated along a neuron, each successive area of the neuron membrane reaches its threshold and causes the next area to be depolarized
As sodium ions enter the axon, they flow to adjacent areas which causes those areas to become less negative which leads to opening of voltage-gated sodium channels and further depolarization
This causes the action potential to move along the axon, with the areas that have been already depolarized not being able to again because of the refractory period, making action potential unidirectional
What does Nervous System Consist of (not neuron)
Central Nervous System (CNS): Brain and Spinal Cord
Peripheral Nervous System (PNS): Connects all parts of the body to the nervous system which contains motor and sensory nerves
Pain Perception Process
Skin encounters stimulus which activates specific TRP channels in nociceptors
Activation of TRP channels opens them, causing positively charged ions (sodium) to enter the free nerve ending
The surplus of positive ions causes depolarization of the free nerve ending
If depolarization reaches threshold potential, action potential is generated where an electrical impulse is travelled along the axons of sensory neurons to the spinal cord (CNS)
In the CNS, the sensory neuron releases neurotransmitters onto relay neurons, which then send the signal to higher brain centers
The brain interprets the location and intensity of the signal from the neuron, which leads to the conscious experience of pain
Cocaine
Acts at dopamine synapses where dopamine is used as a neurotransmitter
Binds to the dopamine reuptake transporters, membrane proteins that pump dopamine back into the presynaptic neuron
Because cocaine binds to the transporters, dopamine builds up in the synaptic gap and postsynaptic neuron is continuously excited and filled with dopamine
Process of Synaptic Transmission
Action potential occurs in presynaptic neuron and travels to axon terminal and reaches its end
The depolarization of the presynaptic membrane causes the opening of voltage-gated calcium channels, which diffuse into the neuron
This causes vesicles that contain neurotransmitters to fuse with the plasma membrane of the presynaptic neuron and expel its contents through exocytosis
The neurotransmitters diffuse within the synaptic cleft and some will bind to receptors located on the postsynaptic neuron plasma mb
The binding to the receptors causes sodium channels to open to enter the postsynaptic neuron which cause the postsynaptic neuron to depolarize which results in an action potential
The neurotransmitter is then reabsorbed by the presynaptic neuron or broken down in the synapse by enzymes
Differences with Myelinated and Unmyelinated Axon
White in color : Gray in color
Have Nodes of Ranvier : Don’t have Nodes of Ranvier
Due to presence of NOR, speed of transmission of nerve impulses is high : Due to lack of NOR, speed of transmission of nerve impulses is low
Don’t lose impulse during conduction : Can lose impulse during conduction
Neurons with long axons are myelinated : Neurons with short axons are unmyelinated
Threshold Potential
Threshold to initiate nerve impulse
-55mV
Myelin Sheath
Insulating layer around the axon which improves conduction speed of electrical impulses
Refractory Period
The time needed for the concentration gradients of Sodium and Potassium ions to be restored by active transport
Following depolarization, resting potential must be restored via the sodium potassium pump to go back to original potential
Neonicotinoid Pesticides and Acetylcholine Receptors
Neonicotinoids bind to acetylcholine receptors in the synapses in the CNS of insects
Acetylcholinesterase is unable to break down neonicotinoids therefore binding is irreversible which makes insect undergo paralysis then death due to lack of neural transmission
Resting Potential
Electrical potential across plasma membrane of a neuron that is not conducting an impulse
Sodium-potassium pump is used to generate resting potential
Where are Neonicotinoid Pesticides Banned
EU and Ontario, Canada
