Potensial Berjenjang (Graded Potential)

Summary

The script discusses the concept of graded potentials, which are small deviations from the resting membrane potential in neurons. These potentials can either hyperpolarize or depolarize the membrane, making it more or less negative. Graded potentials occur in response to stimuli, such as the opening of mechanoreceptive or ligand-gated ion channels, leading to the influx of ions like sodium or calcium. The amplitude of these potentials varies with the strength of the stimulus, and they can summate or cancel each other out. They play a crucial role in the generation of action potentials and are named based on their location and the type of stimulus that causes them, such as postsynaptic potentials or receptor potentials.

Takeaways

• 🔬 Grade potentials are small deviations from the resting membrane potential, causing the membrane to become more or less polarized.
• 🌟 Grade potentials can be hyperpolarized (more negative) or depolarized (less negative or more positive) depending on the stimulus.
• 🧠 These potentials occur in the dendrites of sensory neurons and in the cell bodies and dendrites of motor and interneurons.
• 💡 Grade potentials are initiated by the opening of mechanosensitive or ligand-gated ion channels, allowing ions to flow across the membrane.
• 🚪 The opening of these channels is triggered by mechanical stimuli or binding of neurotransmitters like acetylcholine.
• 🔋 The influx of positive ions such as sodium or calcium during depolarizing potentials makes the inside of the cell more positive, leading to membrane depolarization.
• 🔌 Conversely, the influx of negative ions like chloride during hyperpolarizing potentials increases the negative charge inside the cell, making it more hyperpolarized.
• 📊 Grade potentials vary in amplitude, which depends on the strength and duration of the stimulus, as well as the number of open ion channels.
• 🔁 Grade potentials can summate; when multiple depolarizing or hyperpolarizing potentials occur, they can add up to form a larger potential.
• ⚡ Opposing grade potentials can cancel each other out if they are of opposite polarities, potentially neutralizing the membrane potential.
• 🏷 Grade potentials are also known as postsynaptic potentials when they occur in response to neurotransmitter release at the synapse, or as receptor potentials when they occur at sensory receptors.

Q & A

What is the resting membrane potential and its significance?

The resting membrane potential is the difference in electrical charge across the cell membrane when the cell is at rest. It is significant because it sets the baseline for the cell's ability to generate an action potential in response to stimuli.

What is a graded potential and how does it differ from an action potential?

A graded potential is a change in the membrane potential that varies in amplitude depending on the strength of the stimulus. It differs from an action potential, which is an all-or-nothing response that reaches a threshold and propagates along the axon.

How do mechanoreceptors and ligand-gated channels contribute to the generation of graded potentials?

Mechanoreceptors and ligand-gated channels can open in response to mechanical or chemical stimuli, allowing ions such as sodium or calcium to enter the cell. This influx of positive ions can depolarize the membrane, contributing to the formation of a graded potential.

What is the role of dendrites in the generation of graded potentials?

Dendrites are involved in the generation of graded potentials as they receive synaptic inputs from other neurons. The summation of these inputs in the dendritic region can lead to either depolarization or hyperpolarization of the membrane potential.

What happens during depolarization and hyperpolarization of the membrane potential?

During depolarization, the inside of the cell becomes less negative or more positive due to the influx of positively charged ions. Hyperpolarization, on the other hand, occurs when the inside of the cell becomes more negative due to the efflux of positively charged ions or the influx of negatively charged ions.

How do the amplitudes of graded potentials vary and what factors influence them?

The amplitudes of graded potentials vary depending on the strength of the stimulus and the number of ion channels that open. A stronger stimulus or more open channels will result in a larger amplitude, indicating a greater change in membrane potential.

What is the relationship between the duration of ion channel opening and the amplitude of a graded potential?

The duration that ion channels remain open influences the amplitude of a graded potential. The longer the channels are open, the more ions can enter or exit the cell, leading to a larger change in membrane potential.

Can graded potentials summate, and what are the conditions for this to occur?

Yes, graded potentials can summate when multiple graded potentials of the same type (either depolarizing or hyperpolarizing) occur close together in time. This summation can result in a larger overall change in membrane potential.

What is the significance of the threshold for an action potential to be generated?

The threshold is the level of membrane potential depolarization that must be reached for an action potential to be generated. If the graded potential does not reach this threshold, the cell will not produce an action potential.

What are some examples of different types of graded potentials mentioned in the script?

Examples of different types of graded potentials include postsynaptic potentials, which occur at the synapse in response to neurotransmitter release, and receptor potentials, which occur at sensory receptors in response to stimuli such as touch.

How do the spatial and temporal summation of graded potentials influence the generation of an action potential?

Spatial summation refers to the summation of graded potentials across different parts of the cell membrane, while temporal summation refers to the summation of potentials over time. Both types of summation can increase the amplitude of the graded potential, potentially reaching the threshold necessary to trigger an action potential.

Outlines

00:00

🔬 Graded Potentials and Membrane Polarization

This paragraph discusses the concept of graded potentials, which are small deviations from the resting membrane potential in neurons. It explains how these potentials can either hyperpolarize (become more negative) or depolarize (become less negative) the membrane. The paragraph also describes how graded potentials occur in the dendrites of sensory neurons and can be influenced by mechanical or chemical stimuli. The process of depolarization and hyperpolarization is illustrated with the opening of ion channels allowing the influx of sodium or calcium ions, which carry a positive charge and thus depolarize the membrane, or the efflux of potassium ions, which carry a negative charge and hyperpolarize it. The amplitude of the graded potential is related to the strength of the stimulus and the number of ion channels that open.

05:00

🌐 Interaction of Graded Potentials and Types

The second paragraph delves into the interaction of graded potentials, highlighting how they can summate—either by adding together if they are of the same type (both depolarizing or both hyperpolarizing) or by cancelling each other out if they are of opposite types. It also explains how the duration and number of open ion channels affect the amplitude of the graded potential. The paragraph introduces different types of graded potentials based on the stimuli that cause them and where they occur, such as postsynaptic potentials in the dendrites in response to neurotransmitters or receptor potentials at sensory receptors. The discussion also touches on the threshold for action potential generation and how graded potentials that do not reach this threshold will not trigger an action potential, thus stopping the nerve impulse.

Keywords

💡Graded Potential

Graded potentials are small deviations from the resting membrane potential that can either hyperpolarize or depolarize the membrane without reaching threshold to generate an action potential. In the video, it is mentioned that these potentials occur in the dendritic part of neurons and are influenced by the strength of the stimulus, varying in amplitude accordingly.

💡Resting Membrane Potential

The resting membrane potential is the difference in electrical charge across the cell membrane when the cell is not transmitting signals. It is typically polarized, meaning the inside of the cell is more negative relative to the outside. The video script refers to this state before any stimulus is applied, which is the baseline for the graded potentials discussed.

💡Depolarization

Depolarization is the process where the membrane potential becomes less negative, moving towards a more positive charge. In the context of the video, depolarization occurs when there is a response to a stimulus that allows positively charged ions, such as sodium, to enter the cell, leading to a graded potential of depolarization.

💡Hyperpolarization

Hyperpolarization is the increase in the negative charge of the membrane potential, making it more negative than the resting potential. The script mentions that this occurs when there is a response that makes the membrane less polarized, allowing for an increase in the negative charge inside the cell, contributing to a graded potential of hyperpolarization.

💡Ion Channels

Ion channels are proteins embedded in the cell membrane that allow specific ions to pass through. The video explains that the opening of these channels, either mechanically or due to ligand binding, is crucial for the generation of graded potentials as it allows ions like sodium and calcium to enter the cell.

💡Action Potential

An action potential is a large, rapidly propagating electrical signal that occurs when the membrane potential reaches a certain threshold. The video implies that if the graded potential gets close enough to this threshold, it can trigger an action potential, which is essential for signal transmission in neurons.

💡Neurotransmitters

Neurotransmitters are chemical messengers that transmit signals across a synapse from one neuron to another. The script describes how the binding of neurotransmitters can cause the opening of ion channels, leading to the influx of ions and the generation of postsynaptic potentials.

💡Postsynaptic Potential

A postsynaptic potential is a change in the membrane potential of the postsynaptic neuron in response to the release of neurotransmitters from the presynaptic neuron. The video mentions that these potentials can be either depolarizing or hyperpolarizing, depending on the type of neurotransmitter and receptor involved.

💡Receptor Potential

A receptor potential is the initial electrical response generated in a sensory receptor when it is stimulated. The script gives an example of this when touching a sharp point, which generates a receptor potential that is then transmitted as a graded potential.

💡Synaptic Transmission

Synaptic transmission is the process of signal transfer from one neuron to another through the synapse. The video script discusses how neurotransmitters released into the synaptic cleft can bind to receptors on the postsynaptic neuron, leading to the generation of postsynaptic potentials.

💡Summation

Summation is the process where multiple graded potentials are added together to either enhance or reduce the overall potential. The video explains that if two depolarizing graded potentials occur close in time, they can summate to reach the threshold for an action potential, or if they are of opposite polarities, they can cancel each other out.

Highlights

Grade potential, or potential difference, is a small deviation from the resting membrane potential.

Grade potential can make the membrane more polarized or less polarized, becoming more negative or less negative.

Grade potential occurs when a stimulus causes the opening of mechanoreceptors or ligand-gated channels, allowing ions to enter and exit the cell.

Mechanoreceptors and ligand-gated channels are found in the dendrites of sensory neurons, motor neurons, and interneurons.

Grade potential happens in the dendritic parts and can be seen in the provided image.

There are two types of grade potential: hyperpolarization and depolarization.

A response to a stimulus that makes the membrane more polarized or more negative is called hyperpolarization.

Depolarization occurs when the response makes the membrane less polarized or more positive.

The resting membrane potential is when the cell is not triggered, and the mechanoreceptors are closed.

Positive ions such as sodium and calcium entering the cell cause depolarization.

The entry of positive ions like sodium and calcium increases the internal charge, leading to depolarization.

Binding with acetylcholine opens channels, allowing sodium and calcium to enter, causing depolarization.

The entry of chloride ions, which have a negative charge, increases the negativity of the cytosol, resulting in hyperpolarization.

The amplitude of the grade potential varies depending on the strength of the stimulus.

A stronger stimulus results in a larger amplitude due to more ion channels opening and a longer duration.

Grade potentials can sum up if they are of the same type, increasing the overall potential.

Opposite grade potentials can cancel each other out if they are combined.

Grade potentials have different names depending on the type of stimulus and where they occur, such as postsynaptic potentials or receptor potentials.

Postsynaptic potentials occur in response to neurotransmitters at the synapse.

Receptor potentials occur at sensory receptors, such as when touching a sharp point.

Transcripts

Hai potensial berjenjang atau grade

potensial adalah deviasi kecil dari Mbak

potensial membran istirahat yang membuat

membran menjadi lebih terpolarisasi di

dalam itu menjadi lebih negatif atau

kurang terpolarisasi di dalamnya kurang

negatif potensial berjenjang terjadi

ketika adanya stimulus yang menyebabkan

terbukanya kanal mekanik maupun karena

ligan sehingga memungkinkan Hyeon masuk

dan mengeksitasi membran plasma karena

on mekanik maupun karena ligan itu

banyak ditemukan di dendrit dari neuron

sensoris sedangkan karena ligan itu

banyak di dendek maupun Salma dari

neuron motoris maupun interneuron tapi

intinya adalah grade potensial itu

terjadinya adalah di bagian dendrit

maupun sama seperti terlihat pada gambar

ini potensial

yang itu ada dua yaitu potensial

berjenjang yang bentuknya

hiperpolarisasi dan potensial berjenjang

yang bentuknya adalah depolarisasi

ketika ada respon atau stimulus namun

membuat membran itu lebih terpolarisasi

atau didalamnya menjadi lebih negatif

maka ini disebut potensial berjenjang

hiperpolarisasi jadi semakin negatif

jika ada respon menyebabkan membran itu

menjadi kurang terpolarisasi atau kurang

negatif naik itu disebut potensial

berjenjang depolarisasi menjadi lebih

positifnya ketika potensial membran itu

istirahat atau sel itu tidak terpicu

maka karena gelombang mekanik akan

tertutup ketikan ada tekanan misalnya

maka akan menyebabkan karena gerbang

mekanik ini terbuka sehingga

memungkinkan ion kalsium maupun natrium

masuk ke

Hai karena masuknya ion yang positif ini

natrium maupun kalsium itu membawa

muatan positif maka akan mendepolarisasi

menipu larisas membran maka dikatakan

potensial berjenjang yang tipe

depolarisasi kemudian misalnya contoh

kedua ketika potensial membran istirahat

maka karena ligan disini akan tertutup

tapi ketika Adanya ikatan dengan

asetilkolin karena Lini akan terbuka

sehingga memungkinkan natrium maupun

kalsium itu masuk ya dan secara

bergantian kalium akan keluar nah

masuknya natrium dan kalsium ini akan

menyebabkan di dalam sel itu akan

menjadi lebih positif sehingga potensial

bercinta yang terbentuk ada potensial

berjenjang depolarisasi ikatan dengan

gliserin itu terbuka maka akan

memungkinkan ion klorida yang muatan

negatif masuk

porno ion klorida masuk muatannya

negatif maka akan meningkatkan

negativitas dari sitosol sehingga

dikatakan potensial berjenjang nya

adalah hiperpolarisasi jika makin

menjauhi minus 76 ikata smaka akan

semakin mendekati sel itu untuk di

Munculkan potensial aksi tapi Makin

menjauh maka akan membuat sel itu untuk

tidak dapat melanjutkan impuls saraf

karena tidak akan memicu potensial aksi

nah sinyal elektrik itu dikatakan

berjenjang karena dia bervariasi dalam

amplitudonya Mengapa bervariasi karena

tergantung pada kekuatan stimulus makin

besar stimulus yang datang kekuatannya

maka akan makin besar amplitudo yang

ditimbulkan Kenapa terjadi begitu karena

menentu

Hai dari semakin banyak atau tidaknya

karena lgerbang ligan maupun mekanik

yang terbuka dan berapa lama sih karena

gerbang itu terbuka Kalau makin lama

atau makin banyak kenal yang terbuka

tentunya akan pakai banyak ion yang

masuk ke dalam sel kalau yang masuk

adalah ion positif maka amplitudo ini

atau geraknya ke atasnya tapi jika yang

masuk adalah ion yang muatannya negatif

contohnya tadi Florida maka geraknya

akan ke bawah terhype terpolarisasi nah

perhatikan di sini ya ini simbol satu

kecil maka yang terbentuk adalah

amplitudo yang kecil ini sedang dan ini

yang kuat rumah si adalah proses ketika

potensial berjenjang itu ditambahkan

jika ada dua potensial berjenjang

depolarisasi yang datang dan kemudian

dijumlahkan maka akan semakin besar

potensial berjenjang depolarisasi nya yg

hai ketika ada dua potensial berjenjang

hiperpolarisasi itu ditambahkan maka

semakin besar pula potensial berjejer

hiperpolarisasi nya kalau ada dua yang

potensial berjenjang yang berlawanan

yang satu depolarisasi dan yang satunya

hiperpolarisasi maka mereka dapat saling

menempel atau menghapus satu sama lain

sehingga potensial berjenjang akan

menghilang ini contohnya ya datang

stimulus satu yang berdekatan dengan

stimulus kedua maka akan di-zoom asikan

atau dijumlahkan sehingga akan muncul

potensial berjenjang depolarisasi yang

lebih besar nah potensial berjenjang itu

punya banyak ada beberapa nama

tergantung pada tipe stimulus yang

menyebabkannya dan tergantung pada di

mana beredar potensial atau potensial

bersin yang itu terjadi ketika potensial

berjenjang itu terjadi dendrit atau koma

dari neuron sesuai

Radar respon dari adanya

neurotransmitter maka itu disebut dengan

potensial postsinaptic potensial

berjenjang yang terjadi pada reseptor

sensoris contohnya tadi ya di ujung jari

menyentuh bolpoin maka itu dinamakan

potensial reseptor