Neural Signaling

Question 1

Pain Perception Receptors

Answer 1

Nociceptors are located on the skin and contain transient receptor potential channels (TRP), which act as receptors for many pain stimuli

Question 2

Values of Oscilloscope

Answer 2

Resting Potential: -70mV
Depolarization: 30-40mV
Repolarization: -80mV

Question 3

Summation

Answer 3

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

Question 4

All or None Principle

Answer 4

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

Question 5

Inhibitory Synapses

Answer 5

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

Question 6

Basic Components of Neuron

Answer 6

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

Question 7

Repolarization

Answer 7

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

Question 8

Emergent Property and Consciousness

Answer 8

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

Question 9

Depolarization

Answer 9

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

Question 10

Synapses

Answer 10

Junctions between neurons and receptor or effector cells

Question 11

Synaptic Transmission

Answer 11

The conduction of a nerve impulse from the presynaptic to the postsynaptic neuron through the synaptic cleft

Question 12

Sensory, Relay and Motor Neurons

Answer 12

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

Question 13

What is Acetylcholine

Answer 13

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

Question 14

Propagation of Action Potential Along a Nerve Fiber

Answer 14

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

Question 15

What does Nervous System Consist of (not neuron)

Answer 15

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

Question 16

Pain Perception Process

Answer 16

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

Question 17

Cocaine

Answer 17

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

Question 18

Process of Synaptic Transmission

Answer 18

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

Question 19

Differences with Myelinated and Unmyelinated Axon

Answer 19

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

Question 20

Threshold Potential

Answer 20

Threshold to initiate nerve impulse

-55mV

Question 21

Myelin Sheath

Answer 21

Insulating layer around the axon which improves conduction speed of electrical impulses

Question 22

Refractory Period

Answer 22

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

Question 23

Neonicotinoid Pesticides and Acetylcholine Receptors

Answer 23

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

Question 24

Resting Potential

Answer 24

Electrical potential across plasma membrane of a neuron that is not conducting an impulse

Sodium-potassium pump is used to generate resting potential

Question 25

Where are Neonicotinoid Pesticides Banned

Answer 25

EU and Ontario, Canada