Insect Nervous System Animation

Jim Kalisch Author

03/11/2019 Added

1233 Plays

Description

video describes the function of an insect's nervous system

Searchable Transcript

Search:

[00:00:04.540]The nervous system is composed of neurons.
[00:00:07.140]The nervous system's functions are
[00:00:08.610]to gather information about the environment,
[00:00:10.590]process this information, and then use the information
[00:00:13.500]to modify neural programs that result
[00:00:15.370]in behavioral performance.
[00:00:18.350]The input to the system is a stimulus captured
[00:00:20.670]by a sensory neuron, which transduces the stimulus energy
[00:00:24.050]into an electrical signal, also called action potential.
[00:00:28.380]This electrical signal travels
[00:00:29.910]in one direction along the neuron membrane,
[00:00:32.600]towards a neuron extremity,
[00:00:34.130]until reaching the synaptic cleft,
[00:00:36.820]which is the junction between two neurons.
[00:00:40.110]There, the action potential triggers
[00:00:41.830]the release of neurotransmitters,
[00:00:43.260]which can either be excitatory
[00:00:44.610]or inhibitory in nature.
[00:00:46.380]The importance of the nervous system
[00:00:47.840]to the functional integrity of animals makes it
[00:00:50.340]an extremely sensitive target to poisons.
[00:00:53.380]During this animation, we will explain how
[00:00:55.410]the stimulus travels as an electrical signal along
[00:00:57.680]the neuron membrane, and how it is chemically transmitted
[00:01:00.490]to a second neuron or cell.
[00:01:02.970]We will also demonstrate how pesticides
[00:01:05.210]can interfere with this process.
[00:01:07.480]Any living cell possesses
[00:01:08.850]a transmembrane electrical potential
[00:01:10.960]so that the outside of the cell
[00:01:12.810]is positive with respect to the inside.
[00:01:15.400]In neurons, the power source used
[00:01:17.450]to transmit the stimulus is
[00:01:19.190]the transmembrane electrical potential generated
[00:01:22.320]by a controlled distribution of different ions.
[00:01:26.530]Using energy from ATP,
[00:01:28.760]an ionic pump creates a charge imbalance across the membrane
[00:01:32.440]by carrying three sodium ions out of the neuron
[00:01:35.900]for every two potassium ions carried in.
[00:01:39.580]In a resting neuron, the sodium ions
[00:01:42.310]and the potassium ions
[00:01:43.740]are therefore asymmetrically distributed across
[00:01:45.970]the cell membrane, making the inside negative relative
[00:01:49.260]to the outside.
[00:01:50.530]The neuron membrane is therefore polarized.
[00:01:55.340]The basis of the nerve excitability resides
[00:01:57.910]in the ability of the membrane
[00:01:59.440]to undergo transient changes in membrane potential
[00:02:02.470]in response to external stimuli.
[00:02:04.700]These changes are caused by inward
[00:02:06.880]and outward currents of the sodium
[00:02:09.380]and potassium ions respectively.
[00:02:11.960]A stimulus to the neuron causes
[00:02:13.730]an action potential to move along the axon.
[00:02:16.870]The first phase of the action potential
[00:02:19.050]is caused by a sharp increase
[00:02:21.010]in sodium ion conductance or permeability.
[00:02:24.380]Leading to its inward movement
[00:02:26.150]through sodium ion channels,
[00:02:28.500]the local depolarization causes
[00:02:30.810]the adjacent sodium channel to open, and so on.
[00:02:34.960]A rapid change in potential differences across
[00:02:37.480]the membrane follows increasing potassium conductance,
[00:02:40.530]leading to its outward movement
[00:02:42.100]through the potassium ion channel.
[00:02:43.920]The sharp increase in outward potassium flux causes
[00:02:47.390]the decrease of sodium conductance
[00:02:49.900]by closing sodium ion channels.
[00:02:53.370]The action potential moves in one direction
[00:02:55.950]as a wave of depolarization
[00:02:57.930]because after each opening of a sodium ion channel,
[00:03:01.240]a short refractory period follows,
[00:03:03.800]during which the sodium ion channel cannot open again.
[00:03:07.100]This signal moves until reaching the synaptic cleft.
[00:03:12.200]Within the central nervous system,
[00:03:14.020]neurons communicate by means of chemical transmitters
[00:03:16.650]across a specialized junction,
[00:03:18.320]which is called a synapse.
[00:03:20.050]In synapses, the electrical signal
[00:03:22.240]is transduced into chemical signal,
[00:03:24.540]which are received at the membranes
[00:03:26.300]of other nerves or muscles.
[00:03:28.320]Chemical transmission is therefore initiated
[00:03:30.980]by depolarization resulting from an action potential.
[00:03:34.360]Both excitatory and inhibitory neurotransmitters
[00:03:37.720]have been identified in synapses.
[00:03:40.490]In the excitatory synaptic transmission
[00:03:42.920]when the wave of depolarization achieves
[00:03:44.960]the synaptic region,
[00:03:46.410]voltage-gated calcium ion channels open,
[00:03:49.580]allowing the inward calcium ion movement
[00:03:52.020]into the presynaptic neuron.
[00:03:54.380]The increase in calcium ions inside
[00:03:56.700]the neuron triggers the exocytosis release
[00:03:59.980]of the acetylcholine neurotransmitter
[00:04:02.550]into the synaptic cleft.
[00:04:05.130]Acetylcholine molecules move randomly
[00:04:07.300]within synaptic clefts,
[00:04:08.910]and it is about equally possible
[00:04:10.620]for any given molecule to meet acetylcholinesterase
[00:04:13.860]or acetylcholine receptor sites.
[00:04:16.210]Molecules that reach the enzyme
[00:04:18.030]are broken into choline and acetate,
[00:04:20.180]which are reabsorbed by the presynaptic membrane
[00:04:23.120]to form new acetylcholine molecules.
[00:04:25.970]Molecules that bind to receptor sites
[00:04:28.070]cause depolarization of the postsynaptic membrane,
[00:04:31.270]which is then transmitted along the axon,
[00:04:34.170]as explained earlier.
[00:04:37.290]The inhibitory synaptic transmission
[00:04:39.410]presents similar processes to the excitatory transmission.
[00:04:42.930]In this case, however,
[00:04:44.230]the GABA receptor is the primary inhibitor receptor
[00:04:47.370]at the insect neuromuscular synapsis.
[00:04:50.140]The inhibitor neurotransmitter GABA binds
[00:04:53.200]to the GABA receptor, causing the opening
[00:04:55.970]of chloride ion channels
[00:04:57.720]and consequent chloride ion inward movement
[00:05:01.000]into the neuron membrane.
[00:05:02.570]This conductance increase causes hyperpolarization
[00:05:05.560]of the membrane, blocking the excitatory stimuli.
[00:05:09.140]The importance of the nervous system
[00:05:10.720]to the functional integrity of animals makes it
[00:05:13.160]an extremely sensitive target to poisons.
[00:05:15.570]Therefore, most insecticides have
[00:05:17.560]been directed primarily at the disruption
[00:05:19.570]of the nervous system functions.
[00:05:22.820]Insecticides that act on the sodium channel
[00:05:25.120]can either work by keeping the channel open,
[00:05:27.210]leading to repetitive discharge,
[00:05:28.820]resulting in excitation, or keeping them closed
[00:05:31.330]for a longer period of time,
[00:05:32.830]resulting in depression.
[00:05:34.590]Other groups of insecticides interact
[00:05:36.520]with acetylcholine in various ways.
[00:05:43.410]Acetylcholine inhibitors bind to acetylcholinesterase,
[00:05:46.580]preventing acetylcholine binding to it,
[00:05:48.970]leading acetylcholine binding
[00:05:50.450]to the receptors more frequently.
[00:05:56.760]Acetylcholine agonists bind to acetylcholine receptors,
[00:05:59.840]mimicking the effect of acetylcholine,
[00:06:02.170]causing an excitatory response.
[00:06:09.030]Acetylcholine antagonists bind to acetylcholine receptors,
[00:06:12.470]blocking the effect of acetylcholine,
[00:06:14.390]leading to paralysis.
[00:06:16.330]Antagonists prevent impulse propagation
[00:06:18.870]across the synapse.
[00:06:21.030]Other insecticides act on GABA receptors or transmitters.
[00:06:24.950]GABA antagonists inhibit effects of GABA,
[00:06:27.860]resulting in excitation.
[00:06:29.910]Since GABA acts to increase chloride conductance,
[00:06:32.910]thereby hyperpolarizing the membrane,
[00:06:34.980]inhibition of this effect would result in excitation,
[00:06:38.520]whereas GABA agonists increase affinity
[00:06:40.900]of receptor for GABA, resulting in depression.

The screen size you are trying to search captions on is too small!

You can always jump over to MediaHub and check it out there.

Comments

0 Comments

Insect Nervous System Animation

Description

Searchable Transcript

Comments icon comment

Related Channels

Comments