Nervous System and Neurons Overview
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Questions and Answers

What is a key difference in the speed of transmission between the nervous and endocrine systems?

  • The endocrine system is typically faster than the nervous system.
  • The nervous system is typically faster than the endocrine system. (correct)
  • Both systems have equally rapid transmission speeds.
  • Both systems have equally slow transmission speeds.

How are signals transmitted within the nervous system?

  • By nerve impulses along nerve fibers. (correct)
  • By the lymphatic system.
  • By hormones traveling through the bloodstream.
  • By chemical diffusion between cells.

Which system typically results in a more localized response?

  • The endocrine system, as hormones target specific organs.
  • The nervous system due to direct nerve connections. (correct)
  • Both systems produce localized responses to the same degree.
  • The endocrine system because of blood vessel density

What is a primary distinction regarding the duration of effect between the nervous and endocrine systems?

<p>The nervous system effects are typically short-lived, while the endocrine system's are longer lasting. (B)</p> Signup and view all the answers

Which type of communication system involves the transmission of a signal through the bloodstream?

<p>The endocrine system. (D)</p> Signup and view all the answers

Which of the following best describes the nature of the responses mediated by the nervous system?

<p>Rapid, localized, and short-lived. (A)</p> Signup and view all the answers

How can effects of the nervous system be characterized?

<p>Temporary and reversible. (A)</p> Signup and view all the answers

What determines if an organism can respond to a stimulus?

<p>The inherent ability to react to changes. (D)</p> Signup and view all the answers

What is the role of a taste chemoreceptor cell in the context of sensory transduction?

<p>To convert the energy of a stimulus into a receptor potential (C)</p> Signup and view all the answers

How does a taste chemoreceptor initiate a signal in the sensory neurone it synapses with?

<p>By releasing a chemical transmitter that creates a generator potential (B)</p> Signup and view all the answers

What is the defining characteristic of a generator potential's impact on an action potential?

<p>The generator potential either triggers a full action potential or fails to do so (B)</p> Signup and view all the answers

How does the intensity of a stimulus affect the activity of a chemoreceptor cell?

<p>A stronger stimulus results in a greater receptor potential and more chemical transmitter released (A)</p> Signup and view all the answers

Which process describes what happens when a taste chemoreceptor is continuously stimulated?

<p>Decreased neurotransmitter production, therefore decreasing action potential production (C)</p> Signup and view all the answers

In the reflex arc, what is the role of the sensory neuron and how is a signal initiated?

<p>The sensory neurone receives the chemical neurotransmitter to cause generator potentials and action potentials (B)</p> Signup and view all the answers

What distinguishes a receptor potential from a generator potential?

<p>The receptor potential occurs in the receptor cell, the generator potential occurs in the sensory neurone (D)</p> Signup and view all the answers

Which of these statements correctly describes the specificity of taste chemoreceptors?

<p>Taste chemoreceptors are specific to a single type of dissolved chemical stimulus (A)</p> Signup and view all the answers

What is the primary role of voltage-gated channels in a neuron's axon?

<p>To open or close, controlling the movement of specific ions across the membrane in response to changes in voltage. (A)</p> Signup and view all the answers

How does the sodium-potassium pump contribute to establishing the resting potential of a neuron?

<p>By actively transporting three sodium ions out of the axon for every two potassium ions moved in. (A)</p> Signup and view all the answers

What is the primary difference between leak channels and voltage-gated channels?

<p>Leak channels are always open, allowing diffusion, whereas voltage-gated channels open or close in response to a stimulus. (D)</p> Signup and view all the answers

Why is the inside of the axon negatively charged compared to the outside at resting potential?

<p>Due to the imbalance in ion movement, with substantially more potassium ions diffusing out than sodium ions diffusing in. (B)</p> Signup and view all the answers

What is the chemical gradient in the context of axonal resting potential?

<p>The difference in concentration of ions between the inside and outside of the axon. (D)</p> Signup and view all the answers

Why is the axon membrane 100 times more permeable to potassium ions than sodium ions?

<p>Because the membrane possesses many more leak channels for potassium ions than for sodium ions. (C)</p> Signup and view all the answers

What effect does the electrical gradient have on ion movement across the axon membrane?

<p>It causes positive potassium ions to accumulate on the outside, contributing to the positively charged external environment. (C)</p> Signup and view all the answers

Which of the following is NOT directly involved in establishing the resting potential of a neuron's axon?

<p>The opening of voltage-gated sodium channels initiating action potential. (D)</p> Signup and view all the answers

What primarily contributes to the overall negative charge inside an axon at resting potential?

<p>The presence of large, negatively charged proteins within the cytoplasm. (A)</p> Signup and view all the answers

What is the typical speed range for an action potential traveling along an axon?

<p>0.5 to 100 m/s (D)</p> Signup and view all the answers

What is meant by the equilibrium established in an axon at resting potential?

<p>A state where there is no net movement of ions due to balanced chemical and electrical gradients. (A)</p> Signup and view all the answers

Which factor primarily enables saltatory conduction, leading to faster transmission of action potentials?

<p>Myelin sheath (D)</p> Signup and view all the answers

What is the key event that changes the resting membrane potential to the action potential?

<p>The influx of sodium ions through voltage-gated channels. (D)</p> Signup and view all the answers

According to the provided information, which axon would likely have the fastest transmission speed?

<p>Human motor axon to leg muscle (C)</p> Signup and view all the answers

What is the threshold potential crucial for regarding an action potential?

<p>It is the minimum level of depolarization required to open all voltage-gated sodium channels. (C)</p> Signup and view all the answers

What effect does an increased axon diameter typically have on the speed of action potential transmission?

<p>Increases transmission speed due to reduced ion leakage and increased current flow (A)</p> Signup and view all the answers

What occurs immediately after the membrane reaches approximately +40 mV during an action potential?

<p>Voltage gates on sodium channels close and voltage gates on potassium channels begin to open. (D)</p> Signup and view all the answers

How does temperature typically affect the diffusion of ions and, consequently, nerve impulse speed in an axon?

<p>Higher temperatures speed up ion diffusion and nerve impulses, up to a point (A)</p> Signup and view all the answers

Which ion movements are crucial for establishing the resting potential of an axon?

<p>The movement of potassium ions through leak channels and the presence of large negative proteins. (C)</p> Signup and view all the answers

Which of the following best describes the effect of the myelin sheath on action potential transmission speed?

<p>The myelin sheath allows saltatory conduction, greatly increasing transmission speed. (A)</p> Signup and view all the answers

What is the role of the positive feedback mechanism during depolarization?

<p>To promote constant change to reach the action potential threshold by opening more sodium channels due to sodium ion influx. (B)</p> Signup and view all the answers

Based on the table, how does the diameter of the Squid giant axon and lack of myelin affect its transmission speed compared to the human motor axon to leg muscle?

<p>The squid axon transmits much slower despite its larger diameter because of lack of myelin. (B)</p> Signup and view all the answers

How does the overall positive charge from the tissue fluid surrounding the axon affect potassium ions?

<p>It repels potassium ions, making their outward movement more difficult. (C)</p> Signup and view all the answers

How does the action potential at the end of an axon compare to the initial action potential?

<p>The final action potential is the same size as the first action potential. (C)</p> Signup and view all the answers

What is the primary role of myelin in nerve impulse transmission?

<p>To act as an electrical insulator, enabling saltatory conduction. (B)</p> Signup and view all the answers

What are the nodes of Ranvier?

<p>Breaks in the myelin sheath where action potentials can occur. (D)</p> Signup and view all the answers

How does saltatory conduction speed up nerve impulse transmission?

<p>By allowing action potentials to ‘jump’ between nodes of Ranvier. (B)</p> Signup and view all the answers

What is the role of local circuit currents in the transmission of a nerve impulse?

<p>To initiate depolarization of the adjacent section of membrane. (A)</p> Signup and view all the answers

In unmyelinated neurons, how does the movement of sodium ions during an action potential lead to further depolarization?

<p>The movement of sodium ions causes passive movement towards less positively charged regions, triggering further depolarization. (B)</p> Signup and view all the answers

Why is nerve impulse transmission faster in myelinated neurons compared to unmyelinated neurons?

<p>Because action potentials 'jump' between nodes of Ranvier in myelinated neurons. (D)</p> Signup and view all the answers

What is the consequence of an action potential being propagated along a neuron?

<p>The action potential is propagated without any decrease in amplitude. (B)</p> Signup and view all the answers

In the context of the Mexican wave analogy, what does saltatory conduction represent?

<p>The wave passing around the stadium in 20 or so large stages. (C)</p> Signup and view all the answers

Flashcards

Stimulus and response

The ability of an organism to detect changes in its environment and respond accordingly. This allows organisms to survive by adapting to threats or opportunities.

Endocrine system

A system that uses hormones to regulate and coordinate bodily functions. Hormones are chemical messengers that travel through the bloodstream to target organs.

Nervous system

A system that uses nerve impulses (electrical signals) to transmit information quickly and specifically throughout the body.

Hormones

Chemical messengers used by the endocrine system to regulate bodily functions.

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Nerve impulses

Electrical signals that travel along nerve fibers to transmit information rapidly within the nervous system.

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Target organs

Organs or tissues that respond to specific hormones.

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Homeostasis

The process of maintaining a stable internal environment within an organism, regardless of external changes.

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Survival and reproduction

The ability to pass on genetic traits to offspring.

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Voltage-gated channels

Channels that open and close to allow ions to move across the axon membrane. They are specific to either sodium or potassium ions.

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Leak channels

Channels that remain open and allow diffusion of ions across the axon membrane. They are more prevalent for potassium ions.

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Sodium-potassium pump

Type of membrane protein that actively transports potassium ions into the axon and sodium ions out of it, maintaining the resting membrane potential.

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Resting potential

The difference in electrical charge between the inside and outside of an axon. This occurs as there is a higher concentration of sodium ions outside the axon and a higher concentration of potassium ions inside the axon.

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Polarized axon

The state of the axon when it is not transmitting a nerve impulse, with a negative charge inside and a positive charge outside.

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Chemical gradient

The natural movement of ions across the membrane from an area of high concentration to an area of low concentration. For example, sodium ions diffuse into the axon and potassium ions diffuse out.

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Electrical gradient

The difference in electrical charge across the axon membrane, which influences the movement of ions.

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Permeability

The measure of how easily ions can move across a membrane. The axon membrane is more permeable to potassium ions than sodium ions.

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Saltatory conduction

The process of transmitting a nerve impulse along a myelinated neuron, where action potentials 'jump' from one node of Ranvier to the next, enhancing the speed of transmission.

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Myelin

The insulating fatty sheath surrounding the axon of a neuron, preventing action potentials from forming except at the nodes of Ranvier.

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Nodes of Ranvier

Small gaps in the myelin sheath along the axon of a neuron, where voltage-gated ion channels and sodium-potassium pumps are concentrated.

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Local circuit currents

The movement of positively charged ions within the axon due to an action potential, contributing to depolarization of the adjacent section of membrane.

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Refractory period

The period after an action potential during which another action potential cannot be generated, ensuring that the nerve impulse travels in one direction.

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Continuous conduction

The process of transmitting a nerve impulse along an unmyelinated neuron, where the action potential spreads continuously down the axon.

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Speed of nerve impulse transmission

The speed at which a nerve impulse travels along a neuron, influenced by factors like myelin sheath presence and axon diameter.

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Action potential

A change in membrane potential that travels along the axon of a neuron, transmitting information.

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What are taste chemoreceptor cells?

Taste chemoreceptor cells are specialized cells that convert chemical stimuli into electrical signals, known as receptor potentials.

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What kind of stimuli do taste chemoreceptor cells respond to?

Taste chemoreceptor cells respond to dissolved chemicals, which are the molecules that make up tastes like sweet, sour, salty, bitter, and umami.

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Are taste chemoreceptor cells all the same?

Taste chemoreceptor cells can be classified into several types, depending on the specific chemical they are sensitive to, such as sweet, sour, salty, bitter, or umami.

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What is a receptor potential?

A receptor potential is a change in the electrical potential across the membrane of a taste chemoreceptor cell, caused by the binding of a taste molecule. It is a graded potential, meaning its strength is proportional to the intensity of the stimulus.

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How do taste chemoreceptor cells communicate with sensory neurons?

The chemical transmitter released from the taste chemoreceptor cell stimulates the connected sensory neuron, resulting in the initiation of a nerve impulse.

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How does the strength of the taste stimulus affect the signal transmission?

The strength of the receptor potential generated by the taste chemoreceptor cell determines the amount of neurotransmitter released, which in turn, influences the frequency of action potentials generated in the sensory neuron.

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What happens to taste chemoreceptor cells after prolonged exposure to a taste?

If the stimulus is sustained for an extended period, the chemoreceptor cells show adaptation, meaning their sensitivity to the stimulus decreases. This gradual decrease in response is a protective mechanism that prevents sensory overload.

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What is a reflex arc?

A reflex arc is a simple neural pathway that involves a sensory neuron, a relay neuron (sometimes), and a motor neuron. It is a rapid, involuntary response to a stimulus, bypassing the conscious brain.

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What is resting potential?

The resting potential, or resting membrane potential, is the electrical potential difference across the membrane of a neuron when it is not transmitting a signal.

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What role do negatively charged proteins play in resting potential?

Negatively charged proteins within the cytoplasm of the axon contribute to the overall negative charge of the cell, helping maintain resting potential.

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How is equilibrium maintained in resting potential?

An equilibrium is reached where there's no net movement of ions across the membrane. This balance is maintained by the opposing forces of chemical and electrical gradients.

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What is an action potential?

The action potential is a rapid depolarization of the axon membrane that travels down the axon, transmitting a signal.

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What is depolarization?

Depolarization is the process where the membrane potential becomes less negative, moving closer to zero or even becoming positive.

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What are voltage-gated sodium channels?

Voltage-gated sodium channels are proteins embedded in the membrane that open in response to changes in membrane potential, allowing sodium ions to flow in.

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What is threshold potential?

The threshold potential is the critical level of depolarization that must be reached for an action potential to occur.

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What happens after the action potential is reached?

Once the action potential is reached, voltage-gated sodium channels close, preventing further sodium influx. At the same time, voltage-gated potassium channels open, allowing potassium ions to flow out.

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Action Potential Propagation

The ability of a neuron to conduct a nerve impulse, where the signal's strength remains constant throughout the axon.

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Myelin Sheath

The insulation around an axon that speeds up nerve impulse transmission.

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Axon Diameter and Speed

The larger the diameter of an axon, the faster the nerve impulse travels.

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Temperature and Speed

Higher temperatures increase the speed of ion diffusion, leading to faster nerve impulse transmission.

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Ectothermic Animals

Animals that rely on external sources for body temperature regulation, like reptiles and amphibians.

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Study Notes

Nervous Communications and Neurons

  • The nervous system coordinates homeostatic mechanisms by using nerve impulses or hormones as signaling methods.
  • The nervous system is faster than the endocrine system.
  • The endocrine system involves chemical communication through the bloodstream.
  • The nervous system uses nerve impulses that travel along specific pathways.
  • The central nervous system (CNS) is composed of the brain and spinal cord, coordinating responses.

Structure of Neurons

  • Neurons (nerve cells) transmit electrochemical signals (nerve impulses) throughout the body.
  • A neuron has a cell body, dendrites, and an axon.
  • Dendrites receive incoming signals, and the axon transmits signals away from the cell body.
  • The axon is often covered by a myelin sheath, increasing the speed of nerve impulse transmission.
  • Gaps in the myelin sheath (nodes of Ranvier) allow the impulse to "jump" between these points in a process called saltatory conduction.
  • Sensory neurons relay information from sensory receptors to the CNS.
  • Relay neurons or interneurons connect sensory and motor neurons in the CNS.
  • Motor neurons transmit information from the CNS to effectors (muscles and glands).

Stimulus and Response

  • Organisms respond to internal or external stimuli.
  • Responses increase an organism's chance of survival.
  • Examples of stimuli include temperature, predators, food source.
  • Responses include movement, behaviors or chemical production.

Sensory Receptors

  • Sensory receptors detect stimuli and convert them into nerve impulses.
  • Chemoreceptor cells in taste buds are specific to dissolved chemicals.
  • Chemoreceptor cells are transducers, converting stimulus energy into a receptor potential.
  • Receptor potential leads to a generator potential which if reaches or exceeds set threshold, produces action potential.
  • Taste chemoreceptor cells respond to salt, sour, bitter, sweet and potential savory tastes.
  • Receptors adapt to a constant stimulus over time, reducing frequency of impulses.

The Reflex Arc

  • Reflex arcs are involuntary, rapid responses to stimuli.
  • The reflex arc pathway comprises: stimulus, receptor, sensory neuron, relay neuron, motor neuron, and effector.
  • Sensory neurons transmit impulses to the spinal cord.
  • Relay neurons connect sensory and motor neurons in the spinal cord or brain.
  • Motor neurons transmit impulses from the CNS to an effector organ.
  • Reflexes primarily result from spinal cord processing, bypassing the brain.
  • Adaptive value of reflex arcs includes defending against harmful or dangerous stimuli.

The Nerve Impulse

  • The resting potential of a neuron is maintained by a difference in ion concentrations across the membrane.
  • The action potential is a temporary reversal of membrane potential that propagates along the axon.
  • During the action potential, the sodium channels open allowing sodium into the cell, then the potassium channels open to allow potassium out.
  • These changes in polarity cause the action potential to spread along the neuron.
  • The refractory period ensures the action potential travels in one direction.

Transmission of Impulses Along a Neuron

  • In myelinated neurons, the myelin sheath prevents current leakage, causing the signal to jump between the nodes of Ranvier - a process known as saltatory conduction.
  • In unmyelinated neurons, the impulse travels continuously along the axon.
  • Myelinated neurons transmit impulses faster than unmyelinated neurons which limits the spread of action potentials preventing backward signal transmission
  • Speed of nerve impulse transmission depends on axon diameter, myelination, and temperature.

Speed of Nerve Impulse Transmission

  • The myelin sheath increases impulse transmission speed.
  • Larger axon diameters increase impulse transmission speed.
  • Warmer temperatures increase transmission speed.
  • The refractory period determines impulse frequency.

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Description

This quiz covers the essential aspects of the nervous system, including its role in homeostasis and its comparison with the endocrine system. Learn about the structure and function of neurons, including components like the axon and dendrites, and the process of signal transmission. Test your understanding of how nerve impulses are transmitted effectively throughout the body.

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