Neuroscience Quiz: Action Potentials and Neurons
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Questions and Answers

What is the primary ion responsible for depolarization during the action potential?

  • Sodium ($ ext{Na}^{+}$) (correct)
  • Potassium ($ ext{K}^{+}$)
  • Calcium ($ ext{Ca}^{2+}$)
  • Chloride ($ ext{Cl}^{-}$)

The resting membrane potential is approximately +30 mV.

False (B)

What do you call the phase when the membrane potential decreases back toward resting potential?

Repolarization

The minimum membrane potential needed to trigger an action potential is called the _______.

<p>Threshold</p> Signup and view all the answers

Match the following phases of the action potential with their descriptions:

<p>Depolarization = Increase in membrane potential towards +30 mV Repolarization = Decrease in membrane potential back to resting level After-hyperpolarization = Dip below resting potential Absolute Refractory Period = Inability to generate another action potential</p> Signup and view all the answers

What is the primary function of interneurons in the Central Nervous System?

<p>Integration and processing of information (D)</p> Signup and view all the answers

Motor neurons conduct signals from the CNS to sensory receptors.

<p>False (B)</p> Signup and view all the answers

What component of the neuron receives signals from other neurons?

<p>Dendrites</p> Signup and view all the answers

Signals travel from sensory receptors to the CNS via __________ neurons.

<p>sensory</p> Signup and view all the answers

Match the following neuron types with their functions:

<p>Sensory Neurons = Conduct signals from sensory receptors to the CNS Motor Neurons = Transmit signals from the CNS to muscles Interneurons = Integrate and process information Ganglion = Cluster of nerve cell bodies</p> Signup and view all the answers

What is the role of receptors in the nervous system?

<p>To detect stimuli (C)</p> Signup and view all the answers

The endocrine system is not involved in maintaining homeostasis.

<p>False (B)</p> Signup and view all the answers

What are the two major systems for coordination and control in animals?

<p>Nervous system and endocrine system</p> Signup and view all the answers

The complex communication network of the nervous system is formed by _______.

<p>neurons</p> Signup and view all the answers

Match the types of neurons with their functions:

<p>Sensory neurons = Transmit signals to the CNS Intermediate neurons = Process information within the CNS Motor neurons = Carry signals to effectors</p> Signup and view all the answers

Which component of the human nervous system is responsible for interpreting information?

<p>Brain (C)</p> Signup and view all the answers

The spinal cord connects the Central Nervous System to the Peripheral Nervous System.

<p>True (A)</p> Signup and view all the answers

Name the three types of neurons mentioned.

<p>Sensory neurons, Intermediate neurons, Motor neurons</p> Signup and view all the answers

What is the main function of synapses in the nervous system?

<p>To transmit nerve impulses (A)</p> Signup and view all the answers

Synapses allow for direct physical contact between neurons.

<p>False (B)</p> Signup and view all the answers

What is the gap between the presynaptic and postsynaptic membranes called?

<p>synaptic cleft</p> Signup and view all the answers

Neurotransmitters are released from synaptic _____ to transmit signals across the synaptic cleft.

<p>vesicles</p> Signup and view all the answers

Match the following components of a synapse with their functions:

<p>Axon = Long projection that transmits impulses Synaptic Vesicles = Contain neurotransmitters Dendrites = Receive signals from other neurons Neurotransmitter Substance = Chemicals that transmit signals across the synaptic cleft</p> Signup and view all the answers

How many synapses can a single motor neuron in the spinal cord have?

<p>Over 1000 (A)</p> Signup and view all the answers

Mitochondria provide energy for neurotransmission.

<p>True (A)</p> Signup and view all the answers

The _____ neuron is the one that releases neurotransmitters at the synapse.

<p>presynaptic</p> Signup and view all the answers

What is the primary function of neurotransmitters?

<p>To transmit nerve impulses across the synapse (B)</p> Signup and view all the answers

Cholinergic neurons release norepinephrine.

<p>False (B)</p> Signup and view all the answers

What separates the presynaptic and postsynaptic membranes?

<p>synaptic cleft</p> Signup and view all the answers

The membrane of the synaptic knob closest to the synapse is called the ______.

<p>presynaptic membrane</p> Signup and view all the answers

Which neurotransmitter is associated with the sympathetic nervous system?

<p>Norepinephrine (B)</p> Signup and view all the answers

Match the neurotransmitter with its corresponding neuron type:

<p>Acetylcholine = Cholinergic neurons Norepinephrine = Adrenergic neurons</p> Signup and view all the answers

Neuroreceptors are located on the presynaptic membrane.

<p>False (B)</p> Signup and view all the answers

Neurotransmitters are stored in small ______ within the synaptic knob.

<p>vesicles</p> Signup and view all the answers

Which portion of the Peripheral Nervous System carries sensory information to the CNS?

<p>Afferent portion (C)</p> Signup and view all the answers

The efferent portion of the PNS only carries information related to involuntary functions.

<p>False (B)</p> Signup and view all the answers

What is the role of interneurons within the CNS?

<p>To process information</p> Signup and view all the answers

The brain and spinal cord are part of the _____ Nervous System.

<p>Central</p> Signup and view all the answers

Which of the following statements is true regarding sensory receptors?

<p>They receive stimuli from the environment. (A)</p> Signup and view all the answers

Match the nervous system components with their functions:

<p>Sensory Receptor = Receives stimuli from the environment Sensory Neurons = Transmit signals to the CNS Motor Neurons = Transmit signals from the CNS Interneurons = Process information within the CNS</p> Signup and view all the answers

What is the primary function of neurohormones?

<p>To affect other organs through the circulatory system (B)</p> Signup and view all the answers

Name one hormone that is stored in the posterior pituitary.

<p>Oxytocin</p> Signup and view all the answers

What is the typical resting potential of neurons in humans?

<p>-70 mV (C)</p> Signup and view all the answers

The resting potential of a neuron is the potential difference across the membrane of a stimulated neuron.

<p>False (B)</p> Signup and view all the answers

What active transport mechanism is primarily responsible for maintaining the resting potential in neurons?

<p>Na-K pump</p> Signup and view all the answers

The cytoplasm of the nerve fiber has a high concentration of _____ ions.

<p>potassium (K⁺)</p> Signup and view all the answers

Match the following ions with their location during the resting potential.

<p>K⁺ = High concentration inside the cell Na⁺ = High concentration outside the cell</p> Signup and view all the answers

What effect does the permeability of the membrane have on resting potential?

<p>Affects the rate of ion diffusion (B)</p> Signup and view all the answers

In the resting membrane, most Na⁺ channels are open.

<p>False (B)</p> Signup and view all the answers

What ion tends to diffuse out of the cell, leading to a net negative charge inside the nerve fiber?

<p>potassium (K⁺)</p> Signup and view all the answers

What initiates the release of neurotransmitters from the synaptic vesicles?

<p>Influx of calcium ions ($Ca^{2+}$) (C)</p> Signup and view all the answers

Acetylcholine attaches to any type of receptor on the postsynaptic membrane.

<p>False (B)</p> Signup and view all the answers

What is the approximate delay caused by the diffusion of acetylcholine across the synaptic cleft?

<p>0.5 ms</p> Signup and view all the answers

The process of synaptic transmission involves the release of a neurotransmitter called __________.

<p>acetylcholine</p> Signup and view all the answers

What is the duration of the refractory period?

<p>2 milliseconds (C)</p> Signup and view all the answers

Match the components of synaptic transmission with their roles:

<p>Calcium ions ($Ca^{2+}$) = Trigger vesicle fusion Acetylcholine = Neurotransmitter released Sodium ions ($Na^+$) = Generate action potential Neuroreceptor = Recognizes neurotransmitter</p> Signup and view all the answers

The refractory period allows for multiple action potentials to occur simultaneously.

<p>False (B)</p> Signup and view all the answers

What are the two phases of the refractory period?

<p>Absolute refractory period and Relative refractory period</p> Signup and view all the answers

The ______ refractory period does not allow any additional action potential to be generated no matter the strength of the stimulus.

<p>absolute</p> Signup and view all the answers

What function does the refractory period serve regarding conduction?

<p>It ensures unidirectional conduction. (D)</p> Signup and view all the answers

Match the following terms with their descriptions:

<p>Resting potential = State of the membrane before an action potential Active region = Part involved in generating the action potential Inactive region = Area just preparing to generate another action potential Trigger zone = Location where the action potential begins</p> Signup and view all the answers

The Na-K pump restores the resting concentrations of Na+ and K+ during the ______ period.

<p>refractory</p> Signup and view all the answers

During the relative refractory period, a second action potential can occur but requires a stronger stimulus.

<p>True (A)</p> Signup and view all the answers

What happens during the depolarization phase of the action potential?

<p>Sodium gates open and sodium floods into the cell (A)</p> Signup and view all the answers

During repolarization, potassium continues to outflow while sodium permeability declines.

<p>True (A)</p> Signup and view all the answers

What is hyperpolarization?

<p>A phase where the membrane potential becomes more negative than the resting potential.</p> Signup and view all the answers

The _____ pump is responsible for restoring the normal resting potential of the nerve fibre.

<p>Na-K</p> Signup and view all the answers

Match the phase of the action potential with the related event:

<p>Depolarization = Sodium gates open Repolarization = Potassium outflow Hyperpolarization = Overshoot of negativity Resting Potential = Na-K pump activity</p> Signup and view all the answers

What initiates repolarization in a nerve fibre?

<p>The closing of sodium gates (B)</p> Signup and view all the answers

All sodium channels close before potassium channels open.

<p>False (B)</p> Signup and view all the answers

How does the membrane potential change during an action potential?

<p>It becomes positive during depolarization, then returns to negative during repolarization and hyperpolarization.</p> Signup and view all the answers

Flashcards

Resting Membrane Potential

The initial state of a neuron's membrane, characterized by a negative charge inside compared to the outside.

Depolarization

The rapid increase in membrane potential, caused by sodium ions (Na+) flowing into the neuron.

Action Potential

The entire shift in the membrane potential, from resting, through depolarization and repolarization, back to resting.

Repolarization

The return of the membrane potential to the resting state, caused by potassium ions (K+) flowing out of the neuron.

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Threshold

The minimum membrane potential required to trigger an action potential.

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Afferent Nervous System

Part of the nervous system that carries sensory information from sensory cells to the Central Nervous System (CNS).

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Efferent Nervous System

Part of the nervous system that carries information from the CNS to muscles and glands.

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Voluntary Nervous System

This part of the nervous system controls voluntary actions, such as walking or talking.

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Involuntary or Autonomic Nervous System

This part of the nervous system controls involuntary functions (e.g., heartbeat, breathing, digestion).

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Neurosecretory Cells

Special neurons that release neurohormones directly into the bloodstream. These hormones can affect various organs.

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Neurohormones

Hormones produced by neurosecretory cells that travel through the blood to target organs.

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Negative Feedback Loop

A mechanism where high levels of a hormone trigger a decrease in its own production.

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Hypothalamus

A region in the brain that plays a key role in linking the nervous system to the endocrine system. It is responsible for controlling the release of many hormones.

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CNS Interneurons

Specialized nerve cells in the Central Nervous System (CNS) that connect and process information from other neurons.

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Sensory Neurons

Neurons in the Peripheral Nervous System (PNS) that transmit signals from sensory receptors to the CNS.

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Motor Neurons

Neurons in the Peripheral Nervous System (PNS) that transmit signals from the CNS to muscles.

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Ganglion

A cluster of nerve cell bodies, often located outside the central nervous system.

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Axon

A long, slender projection of a neuron that transmits signals away from the cell body.

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Synapse

The junction between two neurons where information is transmitted.

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Synaptic Cleft

The tiny gap separating the presynaptic and postsynaptic neurons.

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Presynaptic Neuron

The neuron transmitting the signal across the synapse.

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Postsynaptic Neuron

The neuron receiving the signal across the synapse.

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Neurotransmitters

Chemicals released from the presynaptic neuron to transmit signals across the synapse.

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Synaptic Vesicles

Small sacs in the presynaptic neuron that store and release neurotransmitters.

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Neurotransmission

The process of releasing neurotransmitters from the presynaptic neuron into the synaptic cleft.

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Postsynaptic Membrane

The membrane of the postsynaptic neuron that receives neurotransmitters.

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Synaptic Knob

A swelling at the end of an axon where neurotransmitters are released.

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Neuroreceptors

Specialized proteins that bind to neurotransmitters, triggering a response in the postsynaptic neuron.

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Presynaptic Membrane

The membrane of the synaptic knob, facing the synaptic cleft.

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Sensitivity

The ability of an organism to detect and respond to changes in its environment.

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Receptors

Specialized cells that receive stimuli from the environment and convert them into electrical signals.

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Effectors

Specialized cells that carry out a response to a stimulus.

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Nervous System

The body's communication network, made up of neurons that transmit signals.

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Neurons

The conducting cells of the nervous system, responsible for transmitting information.

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Central Nervous System (CNS)

The part of the nervous system that includes the brain and spinal cord.

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Peripheral Nervous System (PNS)

The network of nerves that connect the CNS to the rest of the body.

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Refractory Period

The brief period after an action potential during which a neuron cannot generate another action potential.

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How does the Refractory Period limit action potential frequency?

Limits the frequency of action potentials by preventing a neuron from firing too rapidly.

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How does the refractory period ensure unidirectional conduction?

Ensures that the action potential travels only in one direction, preventing it from going backward.

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Absolute Refractory Period

The period during which a membrane cannot generate another action potential, no matter how strong the stimulus.

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Relative Refractory Period

The brief period following the absolute refractory period, where a stronger than usual stimulus can trigger another action potential.

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What is the trigger zone?

The location where the action potential begins.

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Role of Na+ and K+ channels in the action potential

Sodium and potassium channels open and close during the action potential, allowing these ions to flow across the membrane.

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Resting potential

The state of the membrane before an action potential occurs.

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Hyperpolarization

The membrane potential becomes even more negative than the resting potential, due to the continued outflow of potassium ions ($K^+$).

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Sodium-Potassium Pump

The sodium ($Na^+$) and potassium ($K^+$) pumps actively transport ions across the membrane to maintain the correct ion concentrations and restore the resting potential.

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Sodium Channels Activation

The sodium ($Na^+$) channels open first, allowing sodium ions to flow into the nerve fibre, causing depolarization. This is the 'upward stroke' of the action potential.

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Potassium Channels Activation

The potassium ($K^+$) channels open slightly later than sodium channels, allowing potassium ions to flow out of the nerve fibre, contributing to repolarization.

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Membrane Permeability

The relative permeability of the membrane to ions changes throughout the action potential, influencing the flow of ions and the membrane potential.

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What is the resting potential?

The potential difference across the cell membrane of a neuron when it is not transmitting an impulse. It's usually around -70mV, with the inside of the neuron being negative relative to the outside.

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How is the resting potential maintained?

The resting potential is maintained by a combination of active transport, by the Na-K pump, and passive diffusion of ions through the cell membrane.

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What are the ion concentrations inside and outside a neuron?

The interior of a neuron has a high concentration of potassium ions (K⁺) and a low concentration of sodium ions (Na⁺). The fluid outside the neuron has a low concentration of K⁺ and a high concentration of Na⁺.

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Describe the function of the Na-K pump.

The Na-K pump, using energy from ATP, actively transports 3 sodium ions (Na⁺) out of the neuron for every 2 potassium ions (K⁺) transported in.

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Why is the neuron's membrane more permeable to K⁺ than Na⁺ at rest?

Potassium ions (K⁺) diffuse out of the neuron more readily than sodium ions (Na⁺) due to the higher permeability of the membrane to K⁺.

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How does the movement of K⁺ contribute to the resting potential?

The net loss of K⁺ ions from the neuron creates a negative charge inside, contributing to the resting membrane potential.

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What determines the value of the resting potential?

The value of the resting potential is primarily determined by the electrochemical gradient of potassium ions (K⁺).

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Why is the resting potential important for neuronal function?

The resting potential is crucial for the neuron's ability to generate and transmit electrical signals, like action potentials.

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What happens when a nerve impulse reaches the synaptic knob?

The arrival of a nerve impulse at the presynaptic terminal triggers a cascade of events, ultimately leading to the release of neurotransmitters into the synaptic cleft.

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What role does calcium play in synaptic transmission?

Voltage-gated $Ca^{2+}$ channels open in the presynaptic membrane, allowing calcium ions to rush into the synaptic knob, down their concentration gradient. This influx of calcium triggers the fusion of synaptic vesicles with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft.

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What happens to the neurotransmitter after it is released?

The neurotransmitter, in this case, acetylcholine, diffuses across the synaptic cleft, the space between the pre- and post-synaptic membranes. This diffusion takes about 0.5 milliseconds, creating a slight delay in the transmission of the signal.

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How does the neurotransmitter trigger an action potential in the postsynaptic neuron?

Acetylcholine binds to specific receptors on the postsynaptic membrane, causing a change in the receptor's shape and opening ion channels. This allows sodium ions ($Na^{+}$) to flow into the postsynaptic cell, generating an action potential and transmitting the signal.

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How does the signal get stopped at the synapse?

The process of synaptic transmission ends with the removal of neurotransmitter from the synaptic cleft. This can occur through enzymatic breakdown, reuptake into the presynaptic terminal, or diffusion away from the synapse.

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Study Notes

The Nervous System

  • The nervous system is responsible for coordinating and controlling physiological activities and transmitting information
  • The nervous system works with the endocrine system to maintain homeostasis
  • The hypothalamus is a significant link between the nervous and endocrine systems
  • The nervous system utilises electrical impulses and chemical messengers for communication
  • The nervous system involves three major components: the brain, the spinal cord, and nerves to all parts of the body
  • Two major divisions of the nervous system:
    • Central Nervous System (CNS): the brain and spinal cord. It is the control center for the body.
    • Peripheral Nervous System (PNS): A network of nerves that connects the CNS to other parts of the body. It carries information to and from the CNS
  • Different nerves
    • Sensory nerves bring sensory information to the CNS
    • Motor nerves carry information from the CNS and trigger responses
  • Sensory neurons: responsible for carrying information from sensory organs (eyes, ears, skin, joints, and skeletal muscle) to the CNS
  • Motor neurons: responsible for carrying information from the CNS to effectors (muscles and glands)
  • There are two types of motor neurons: conscious and unconscious.
  • Conscious pathways control voluntary movements, while unconscious ones regulate involuntary actions.
  • Interneurons: located entirely within the CNS, these neurons connect sensory and motor neurons, processing information and transmitting signals between them
  • Neurohormones: some neurons produce neurohormones which are hormones delivered through the circulatory system. The neurohormones act on other organs to regulate their function — including controlling the function of the pituitary gland
  • High levels of hormones will trigger the hypothalamus and the pituitary gland to stop their release

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Description

Test your knowledge on the action potential phases, neuron types, and their functions within the nervous system. This quiz covers key concepts like depolarization, membrane potential, and the roles of different neurons. Perfect for students studying neuroscience or biology.

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