Nervous System Functions and Signals
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Questions and Answers

What are the three primary functions of the nervous system?

  • Sensory, Motor, and Digestive
  • Motor, Cognitive, and Sensory
  • Sensory, Integrative, and Motor (correct)
  • Sensory, Integrative, and Homeostatic

What is the term for the electrical signal conducted by neurons?

  • Action potential (correct)
  • Neural wave
  • Nerve impulse
  • Signal potential

Which branch of the nervous system is responsible for analyzing incoming sensory information?

  • Voluntary
  • Sensory
  • Integrative (correct)
  • Motor

Which type of cell in nervous tissue is responsible for support and protection?

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

What does the sensory function of the nervous system primarily involve?

<p>Detecting changes via sensory receptors (B)</p> Signup and view all the answers

Which of the following best describes a neuron?

<p>Electrically excitable cellular structures (C)</p> Signup and view all the answers

What is the main purpose of the nervous system in maintaining health?

<p>To maintain homeostasis (C)</p> Signup and view all the answers

How do effectors function in the nervous system?

<p>They respond to stimuli. (C)</p> Signup and view all the answers

What is the primary function of Action Potentials in excitable cells?

<p>To facilitate communication over short and long distances (A)</p> Signup and view all the answers

Which type of ion channel is most prevalent in neurons?

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

Which type of ion channel responds to changes in membrane potential?

<p>Voltage-gated channels (A)</p> Signup and view all the answers

What characterizes Graded Potentials in comparison to Action Potentials?

<p>Graded Potentials allow communication over short distances only (A)</p> Signup and view all the answers

What is a characteristic function of Ligand-gated channels?

<p>Respond to chemical stimuli (D)</p> Signup and view all the answers

Leak channels are characterized by which of the following?

<p>They alternate between opening and closing (D)</p> Signup and view all the answers

Which of the following statements about resting membrane potential is true?

<p>Resting membrane potential is maintained by various ion channels (D)</p> Signup and view all the answers

Which type of stimuli do Mechanically-gated channels react to?

<p>Mechanical vibration or pressure (C)</p> Signup and view all the answers

What primarily determines the amplitude of a graded potential?

<p>Strength of the stimulus (B)</p> Signup and view all the answers

What is the main characteristic of graded potentials compared to action potentials?

<p>Graded potentials can be summed together (C)</p> Signup and view all the answers

Which phase of an action potential involves the membrane potential becoming more negative?

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

What must occur for an action potential to be generated?

<p>Membrane potential reaching threshold (A)</p> Signup and view all the answers

Which type of channels are primarily involved in the conduction of action potentials?

<p>Voltage-gated channels for Na+ and K+ (A)</p> Signup and view all the answers

How do graded potentials differ in their propagation compared to action potentials?

<p>Graded potentials are decremental (C)</p> Signup and view all the answers

During which phase of an action potential does the membrane potential increase rapidly?

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

What is one major feature of action potentials compared to graded potentials?

<p>Action potentials propagate along the axon (B)</p> Signup and view all the answers

What is necessary for repair to occur in the peripheral nervous system (PNS)?

<p>Functional Schwann cells (A)</p> Signup and view all the answers

Which step is NOT involved in the repair process in the PNS?

<p>Myelination of axons (B)</p> Signup and view all the answers

What is a common symptom of multiple sclerosis?

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

What is a common treatment for depression?

<p>Selective serotonin reuptake inhibitors (SSRIs) (B)</p> Signup and view all the answers

Which type of depression is characterized by recurring episodes of mania and depression?

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

What causes excitotoxicity in the CNS?

<p>High levels of glutamate (C)</p> Signup and view all the answers

What defines epilepsy?

<p>Short, recurrent attacks of various functions (B)</p> Signup and view all the answers

What type of depression is persistent but less severe than major depression?

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

What is the typical amplitude range of action potentials?

<p>Typically about 100 mV (B)</p> Signup and view all the answers

Which factors contribute to the speed of action potential propagation?

<p>Amount of myelination and temperature (B)</p> Signup and view all the answers

How does the duration of graded potentials compare to that of nerve impulses?

<p>Graded potentials are typically longer than nerve impulses (D)</p> Signup and view all the answers

What distinguishes action potentials from graded potentials regarding polarity?

<p>Action potentials consist of depolarizing and repolarizing phases (D)</p> Signup and view all the answers

Which statement best describes refractory periods in graded potentials?

<p>There are no refractory periods in graded potentials (B)</p> Signup and view all the answers

How does myelination affect action potential propagation?

<p>Myelination increases the speed of action potential propagation (C)</p> Signup and view all the answers

What occurs to action potentials as they propagate along a neuron?

<p>They maintain their strength (D)</p> Signup and view all the answers

Which of the following statements is true regarding the duration of nerve impulses?

<p>Nerve impulses can range from 0.5 to 2 msec (D)</p> Signup and view all the answers

What triggers ligand-gated channels to open?

<p>Binding of a ligand (A)</p> Signup and view all the answers

Which type of neurons primarily contains voltage-gated channels?

<p>All types of neurons (B)</p> Signup and view all the answers

What is the state of the membrane potential of a non-conducting neuron?

<p>Positive outside and negative inside (B)</p> Signup and view all the answers

What maintains the resting membrane potential in neurons?

<p>N a+/K+ pumps (B)</p> Signup and view all the answers

Which types of stimuli can open mechanically gated channels?

<p>Mechanical stimuli such as touch (C)</p> Signup and view all the answers

Which statement best describes graded potentials?

<p>They represent small deviations in resting membrane potential. (D)</p> Signup and view all the answers

Which ions are primarily responsible for determining the resting membrane potential?

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

What effect do most anions have on the intracellular environment of a neuron?

<p>They cannot leave the cell. (D)</p> Signup and view all the answers

Flashcards

What is the main function of the nervous system?

The nervous system is responsible for detecting changes in the environment, processing this information, and responding to it.

How is the nervous system organized?

The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS).

What does the central nervous system consist of?

The central nervous system (CNS) consists of the brain and spinal cord.

What does the peripheral nervous system consist of?

The peripheral nervous system (PNS) consists of nerves that connect the CNS to the rest of the body.

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How is the PNS subdivided?

The PNS is further divided into the somatic nervous system and the autonomic nervous system.

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What are neurons?

Neurons are specialized cells that transmit electrical signals throughout the nervous system.

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What are neuroglia?

Neuroglia are specialized cells that support and protect neurons.

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What are action potentials?

Action potentials are electrical signals that travel along neurons.

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Communication in Excitable Cells

Excitable cells communicate using signals called action potentials (long distance) and graded potentials (short distance).

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Resting Membrane Potential

A resting membrane potential exists due to an uneven distribution of ions across the cell membrane.

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What are Graded Potentials?

Graded potentials are short-lived changes in membrane potential caused by stimuli like neurotransmitters or sensory input.

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Leak Channels

Leak channels are always open, allowing ions to pass through the membrane passively.

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Ligand-gated Channels

Ligand-gated channels open when a specific molecule binds to a receptor on the channel.

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Mechanically-gated Channels

Mechanically-gated channels open in response to physical deformation of the membrane.

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Voltage-gated Channels

Voltage-gated channels open or close in response to changes in the membrane potential.

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Graded Potential

The change in membrane potential due to a stimulus.

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Action Potential

A nerve impulse that travels down the length of a neuron.

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Propagation of Action Potentials

The process by which an action potential travels along the axon.

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Continuous Conduction

The movement of an action potential along an unmyelinated axon.

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Saltatory Conduction

The faster movement of an action potential along a myelinated axon.

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Propagation Speed

The speed at which an action potential travels along an axon.

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Synapse

A junction where a neuron communicates with another cell.

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Neurotransmitter

A chemical messenger released by a neuron at the synapse.

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Voltage Difference

The difference in charge across the neuron's membrane, with the inside being negative and the outside being positive.

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Factors Affecting Resting Membrane Potential

Uneven distribution of ions across the neuron membrane, selective permeability of the membrane to sodium and potassium ions, and active transport by the sodium-potassium pump contribute to the resting membrane potential.

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How Graded Potentials are Generated

Graded potentials are generated by the opening of ligand-gated or mechanically-gated ion channels.

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Graded Potential Amplitude

The size or magnitude of a graded potential is directly proportional to the strength of the stimulus. A stronger stimulus leads to a larger graded potential.

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Graded Potential Summation

Multiple graded potentials can summate, adding their effects on the membrane potential. This can either increase or decrease the overall change in voltage.

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Depolarization

The initial phase of an action potential where the membrane potential becomes more positive.

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Repolarization

The second phase of an action potential where the membrane potential returns to its resting negative value.

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Action Potential Threshold

For an action potential to occur, the membrane potential must reach a critical threshold level. Below this threshold, no action potential will be generated.

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Sodium Channel Opening (Action Potential)

Voltage-gated sodium (Na+) channels open and allow sodium ions to flow into the cell, causing depolarization.

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Potassium Channel Opening (Action Potential)

Voltage-gated potassium (K+) channels open and allow potassium ions to flow out of the cell, causing repolarization.

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Peripheral nerve repair

The process of repairing damaged peripheral nerves involves three main steps, including chromatolysis, Wallerian degeneration, and formation of regeneration tubes.

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Chromatolysis

A change in the neuron's cell body that occurs after an injury, characterized by the swelling of the cell body and the displacement of the nucleus.

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Wallerian degeneration

The breakdown of the distal portion of an injured axon, starting at the site of injury and extending to the axon's terminal. This process is essential for clearing the damaged axon and preparing for regeneration.

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Regeneration tube

A tube-like structure formed by Schwann cells that guide the regenerating axon to its target. This is crucial for restoring neuronal function.

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Multiple Sclerosis (MS)

A chronic autoimmune disease that damages myelin sheath, leading to the progressive deterioration of the nervous system. The cause is still unknown, but genetic and environmental factors may play a role.

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Depression

A mental health disorder characterized by persistent sadness, loss of interest in activities, feelings of helplessness, and potentially suicidal thoughts. Several types of depression exist, each with its own characteristics.

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Epilepsy

A neurological disorder characterized by short, recurrent attacks of motor, sensory, or psychological dysfunction caused by abnormal simultaneous electrical discharges from neurons in the brain.

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Excitotoxicity

The destruction of neurons caused by prolonged activation of excitatory synapses. It is often triggered by high levels of glutamate in the brain.

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Study Notes

Nervous Tissue Overview

  • The nervous system maintains homeostasis by controlling conditions within healthy limits.
  • The nervous system has various branches and cell types.
  • The chapter aims to detail the structure and function of nervous tissue.

Nervous System Overview

  • Neurons are electrically excitable cells.
  • Nervous impulses travel in specific directions.
  • Key neuron types include sensory, interneurons, and motor neurons.

Nervous System Organization

  • The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS).
  • The CNS comprises the brain and spinal cord.
  • The PNS includes cranial, spinal nerves, enteric plexuses, and sensory receptors.

Functions of the Nervous System

  • The nervous system detects changes via sensory receptors.
  • It analyzes sensory data, stores aspects, and directs appropriate actions.
  • It responds to stimuli via effectors.

Histology of Nervous Tissue

  • The study of nervous tissue structure.
  • Includes neurons and neuroglia (nerve support cells).

Neurons (Structure)

  • Neurons are electrically excitable cells.
  • Their parts include dendrites, cell body, axon, and axon terminals.
  • Diagrams illustrate a nerve impulse's path and neuron structure.

Neuronal Classification

  • Neurons are classified structurally by the number of processes emanating from their cell body (multipolar, bipolar, pseudounipolar).
  • Functionally, they are classified by the direction of nerve impulse propagation (sensory, motor, interneurons).

Neuroglia

  • Neuroglia makes up approximately half the total volume of the nervous system.
  • Neuroglia are non-excitable cells that support and protect neurons.
  • They are crucial for maintaining the chemical environment around neurons and can multiply and divide.
  • Several types of neuroglia exist in the central and peripheral nervous systems (4 in CNS, 2 in PNS).
  • Neuroglia support neurons in a variety of ways.

Myelination of Neurons

  • Myelin is a fatty substance that surrounds some axons.
  • It's produced by Schwann cells (PNS) and oligodendrocytes (CNS).
  • Myelin dramatically increases the speed of impulse transmission.

Gray Matter vs. White Matter

  • Gray matter lacks myelin and contains neuron cell bodies.
  • White matter is rich in myelinated axons.
  • These structures are prevalent within the brain and spinal cord.

Electrical Signals in Neurons

  • Excitable cells communicate via action potentials and graded potentials.
  • Action potentials facilitate over long or short distances, while graded potentials are limited to shorter distances.
  • These signals depend on the existence of a resting membrane potential and specific ion channels.

Resting Membrane Potential

  • The membrane of a non-conducting neuron has a negative charge inside and a positive charge outside.
  • This difference is caused by uneven ion distribution across the membrane
  • Selective membrane permeability factors are involved.
  • The Na+/K+ pump plays a critical role in maintaining this potential.

Graded Potentials

  • Small deviations in the resting membrane potential.
  • Generated by the opening of mechanically gated or ligand-gated ion channels.
  • Their amplitude varies with the strength of the stimulus.
  • Can be summed (temporal or spatial).

Action Potentials

  • A rapid sequence of events that reverses and eventually restores the membrane potential.
  • Consists of two phases: depolarization and repolarization.
  • The strength of a stimulus determines whether an action potential occurs.
  • All-or-none principle applies to action potentials. The signal strength remains unchanged as it propagates along the axon.

Propagation of Action Potentials

  • Action potentials travel from the trigger zone down the axon to the axon terminals.
  • Propagation occurs through continuous or saltatory conduction.
  • Factors affecting conduction speed include axon diameter, myelination, and temperature.

Signal Transmission at Synapses

  • A synapse is the connection between two neurons or a neuron and an effector.
  • Two main types of synapses exist: electrical and chemical.
  • Chemical synapses involve neurotransmitters for signal transmission.

Postsynaptic Potentials

  • Excitatory postsynaptic potentials (EPSPs) are depolarizing.
  • Inhibitory postsynaptic potentials (IPSPs) are hyperpolarizing.
  • Often, postsynaptic potentials are summed.

Neurotransmitter Receptors

  • Neurotransmitters (chemical messengers) at chemical synapses can trigger excitatory or inhibitory postsynaptic potentials.
  • Receptors are either ionotropic or metabotropic.
  • Ionotropic receptors directly open ion channels, whereas metabotropic receptors utilize a second messenger system.

Removal of Neurotransmitters

  • Neurotransmitters are cleared from the synaptic cleft to terminate signaling.
  • Removal methods include diffusion, enzymatic degradation, and reuptake into cells.

Summation

  • Summation occurs when multiple presynaptic neurons simultaneously or sequentially release neurotransmitters onto a postsynaptic neuron.

Neural Circuits

  • Functional groups of interconnected neurons that perform a particular task. Different types of neural circuits (e.g., simple series, diverging, converging, reverberating, parallel after-discharge).

Regeneration & Repair of Nervous Tissue

  • The nervous system exhibits plasticity but neurons have limited regenerative capacity.

Neurogenesis in the CNS

  • There is minimal repair in the central nervous system due to inhibitory neuroglia.
  • Factors like the absence of growth stimulants and rapid scar tissue formation hinder repair.

Damage and Repair in the PNS

  • Nerve repair is more likely in the peripheral nervous system than in the central nervous system, provided the cell body is intact.

Neural Disorders (Multiple Sclerosis & Depression)

  • Multiple sclerosis is an autoimmune disease causing myelin sheath destruction.

  • Depression presents as various types with common symptoms like lack of interest, sadness, helplessness and potentially suicidal thoughts.

Other Neural Disorders (Epilepsy & Excitotoxicity)

  • Epilepsy involves recurrent seizures.
  • Excitotoxicity is neuronal damage caused by prolonged stimulation from excitatory neurotransmitters.

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Test your knowledge on the primary functions and mechanisms of the nervous system. This quiz covers various aspects, including electrical signals, types of cells, and ion channels involved in neural communication. It’s perfect for students studying neurobiology or related fields.

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