Nervous System Functions and Levels
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Questions and Answers

In serial processing, an incoming signal is divided and sent through multiple pathways simultaneously.

False (B)

Amplification within a neuronal pool increases the strength of the incoming signal and transmits it in numerous directions.

True (A)

Convergence occurs when a single incoming signal results in multiple, separate excitatory signals.

False (B)

After-discharge is a short-lasting output that occurs only when an incoming signal is still present.

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

Synaptic after-discharge is caused by long-acting synaptic transmitter substances at the surface of postsynaptic neurons.

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

Reverberatory circuits are a mechanism for after-discharge where signal flow is strictly one-way without any feedback loops.

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

Inhibitory mechanisms in the nervous system help prevent continuous re-excitation and uncontrolled signals throughout the brain.

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

Inhibitory interneurons prevent signals from spreading diffusely by synapsing at the axons or terminals of adjacent less excited neurons.

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

Recurrent inhibition occurs when a collateral terminal from a pathway excites an inhibitory interneuron, which then inhibits the initial excitatory neuron of a different pathway.

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

The nervous system can adjust the sensitivity of information pathways through both short-term fatigue mechanisms and long-term receptor downgrading or upgrading.

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

Fatigue mechanism leads to decreased sensitivity of overused pathways and decreased sensitivity of underused pathways.

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

Long-term adjustments in pathway sensitivity are facilitated by downgrading or upgrading of synaptic receptors, impacting sensitivities of the synapses.

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

The somatosensory system is a sensory system associated with the environmental conditions that effect the body from the outside world.

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

Sensory receptors convert environmental signals into neural signals by a process called action reduction.

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

Mechanoreceptors detect changes in temperature, sound, and chemical concentrations.

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

Proprioceptors monitor the position of joints, the tension in tendons, and also can measure the level of blood glucose.

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

Receptor adaptation is a progressive increase in receptor response to a constant stimulus.

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

Phasic receptors send constant signals to the brain for many minutes or hours.

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

Tonic receptors adapt quickly to continuous stimulation.

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

The macula in the vestibular apparatus is an example of a phasic receptor.

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

A sensory unit consists of multiple sensory axons.

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

The receptive field of a sensory unit is the area where a stimulus produces a response.

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

Recruitment of sensory units involves reduction in the number of active sensory units as stimulus intensity increases.

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

Overlapping of sensory units only happens within the same receptor type.

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

Golgi tendon apparatuses are classified as phasic receptors

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

The number of impulses transmitted by phasic receptors is related to the change rate of the stimulus.

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

A sudden painful stimulus gives a single pain sensation.

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

Mechanosensitive pain receptors are primarily excited by extreme temperatures.

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

Thermosensitive pain receptors are sensitive to extreme heat or cold.

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

Chemosensitive pain receptors are only activated by direct damage to nerve fibers.

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

Aspirin reduces pain by increasing the production of prostaglandins.

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

Ischemia can cause pain due to the accumulation of lactic acid in tissues.

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

Muscle spasm can directly stimulate chemosensitive pain receptors.

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

Prostaglandins reduce the sensitization of pain nerve fibers.

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

Substance P, histamine, and potassium ions are all examples of chemicals that can stimulate chemosensitive pain receptors.

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

Referred pain is experienced in the exact same location as the source of the tissue damage.

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

Stimulation of large A fibers opens the pain gate by exciting inhibitory interneurons.

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

Acupuncture inhibits pain signals by stimulating large sensory fibers that project to the dorsal column of the spinal cord, which then results in decreased transmission of pain signals.

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

Nociceptors are only stimulated when the temperature is below 10°C or above 45°C.

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

Warm receptors are stimulated by Aδ fibers and C fibers, while cold receptors are only stimulated by C fibers.

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

An increase in the stimulated surface area makes it difficult to determine gradations of temperature.

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

Flashcards

Types of Neuronal Pool Processing

Neuronal pools can process incoming signals in different ways, allowing for sequential (serial) processing, parallel processing, and signal amplification (amplification).

Divergent Output

When a signal enters a neuronal pool, it can create an excitatory output in one direction and an inhibitory output in another.

Convergence

Multiple incoming signals can converge on the same neuronal pool, where they are summed together.

After-Discharge

After an incoming signal stops, a neuronal pool can continue to produce an output signal for a period of time.

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Synaptic After-Discharge

Synaptic after-discharge is a type of after-discharge caused by a long-acting neurotransmitter at the synapse.

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Reverberatory Circuit

A reverberatory circuit is a type of neural circuit where a neuron feeds back to re-excite itself, creating a loop of activity.

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Inhibitory Mechanisms

Inhibitory mechanisms help to stabilize neuronal circuits by preventing runaway excitation, which can lead to uncontrolled brain activity.

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Inhibitory Interneuron

A type of neuron that inhibits the activity of other neurons, preventing the spread of signals in a neural pathway.

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Recurrent Inhibition

A circuit where a neuron sends a collateral branch back to excite an inhibitory interneuron, which then inhibits the initial neuron, creating a feedback loop.

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Pathway Sensitivity Adjustment

The ability of the nervous system to adjust its sensitivity to different stimuli, either by short-term fatigue or long-term changes in receptor proteins.

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Fatigue Mechanism

A type of short-term sensitivity adjustment where frequently used pathways become fatigued and less sensitive.

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Synaptic Receptor Downgrading/Upgrading

A type of long-term sensitivity adjustment where overused pathways decrease receptors, reducing sensitivity, and underused pathways increase receptors, increasing sensitivity.

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Somatosensory System

The system that receives and processes sensory information from different parts of the body.

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Sensory Receptors

Specialized cells or neurons that convert sensory stimuli into neural signals.

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Mechanoreceptors

Sensory receptors that respond to mechanical stimuli, such as touch, pressure, vibration, and movement.

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Proprioceptors

Sensory receptors that provide information about the position of joints, tension in muscles, and movement.

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Gate Control Theory (Large Fiber Stimulation)

Large nerve fibers (A fibers) suppress pain by stimulating inhibitory interneurons in the spinal cord, closing the 'gate' on the pain signal.

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Gate Control Theory (Small Fiber Stimulation)

Small nerve fibers (C fibers) amplify pain by inhibiting inhibitory interneurons, opening the 'gate' on the pain signal.

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Thermal Sensations

The body's ability to detect and respond to temperature changes.

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Cold Receptors

Sensory receptors that respond to temperatures slightly below body temperature, peaking at just under 10 degrees Celsius.

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Warmth Receptors

Sensory receptors that respond to temperatures slightly above body temperature.

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Double pain sensation

A sudden, sharp pain followed by a slower, burning pain, often experienced in response to a damaging stimulus.

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Pain receptors (nociceptors)

Free nerve endings that respond to painful stimuli.

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Mechanosensitive pain receptors

Pain receptors that are triggered by excessive pressure or tissue damage.

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Thermosensitive pain receptors

Pain receptors that are sensitive to extreme heat or cold.

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Chemosensitive pain receptors

Pain receptors that are sensitive to various chemicals released at injury sites.

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Substance P

A chemical that plays a role in pain sensation, released at injury sites.

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Aspirin (and non-steroidal anti-inflammatory drugs)

A substance that prevents the formation of prostaglandins, which are involved in pain sensitization.

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Referred pain

Pain felt in a different location from the source of the injury.

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Ischemia

Reduced blood flow to tissues, often caused by muscle spasms.

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Muscle spasm

A prolonged contraction of a muscle, which can cause pain by directly stimulating pain receptors or indirectly by causing ischemia.

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Sensory Receptor Adaptation

The gradual decrease in the response of a receptor to a continuous stimulus. Receptors initially respond strongly but then their activity declines even though the stimulus remains constant.

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Tonic Receptors

Receptors that adapt slowly and incompletely, providing continuous information about a stimulus as long as it's present.

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Examples of Tonic Receptors

Examples of tonic receptors include those in joint capsules, muscle spindles, and pain receptors.

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Phasic Receptors

Receptors that adapt rapidly and completely, responding only to changes in stimulus intensity.

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Examples of Phasic Receptors

Examples of phasic receptors include pressure receptors in the skin and some touch receptors.

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Sensory Unit

A single sensory neuron and all its branches, forming the functional unit of the sensory system.

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Receptive Field

The area of the body that, when stimulated, activates a particular sensory unit.

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Recruitment of Sensory Units

Increasing the intensity of a stimulus activates more sensory units.

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Overlapping Sensory Units

Overlap of receptive fields from different sensory units in the skin.

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Tactile Receptors

Specialized mechanoreceptors responsible for detecting touch, pressure, and vibration.

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Study Notes

Nervous System Functions

  • Coordinate the activities of other systems (along with the endocrine system) through senses and responses to internal and external events; maintaining homeostasis.
  • Store experiences (memory) and establish patterns of response based on prior experiences (learning).

Functional Levels of the CNS

  • Intercommunication between the external and internal environments is mediated by the sensory-somatic and autonomic peripheral nervous systems, respectively.
  • The CNS can be divided into three functional levels: spinal cord, lower brain (subcortical), and higher brain (cortical).

Spinal Cord Level

  • Conduit for signals between the periphery and the brain.
  • Contains reflex control centers.

Lower Brain Level (Subcortical)

  • Controls subconscious bodily functions, such as arterial pressure, respiration, and emotional responses.

Higher Brain Level (Cortical)

  • Transforms lower CNS functions into precise operations.
  • Essential for thought processes.
  • Large memory storehouse.

Neuronal Pools

  • Interconnected neurons.
  • Process signals in specialized ways, such as serial or parallel processing or amplification.
  • Input signals can excite, inhibit, or facilitate neurons within the pool.
  • Convergence allows the summation of multiple input signals.

Synaptic After-discharge

  • Prolonged output discharge after an incoming signal.
  • Caused by persistent synaptic transmitter substances or parallel signals converging on an output neuron or reverberation of neurons.

Stabilization of Neuronal Circuits

  • Critical to prevent uncontrolled signal transmission.
  • Inhibitory mechanisms prevent widespread re-excitation.

Presynaptic Inhibition

  • Inhibition occurs before the signal reaches the synapse.
  • Mechanisms include opening Cl and K ion channels, blocking Ca channels.

Postsynaptic Inhibition

  • Inhibition originates at the postsynaptic membrane.
  • Can be due to IPSP generation or synaptic fatigue.

Anatomical Inhibition

  • Lateral Inhibition: Inhibitory interneurons prevent signal spreading to neighboring neurons.
  • Recurrent Inhibition: Collateral signals excite inhibitory interneurons, leading to inhibition of the initial excitatory neuron.

Adjustment of Pathway Sensitivity

  • Fatigue Mechanism (Short-term): Overused pathways become less sensitive, while underused pathways become more sensitive.
  • Downgrading/Upgrading (Long-term): Receptor proteins adjust to increase or decrease sensitivity dependent on usage.

Sensory Receptors

  • Specialized cells or neurons that transduce environmental signals (mechanical, light, sound, chemical, temperature) into neural signals (action potentials).
  • Five types based on the stimulus: mechanoreceptors, thermoreceptors, nociceptors, electromagnetic receptors, and chemoreceptors.
  • Types associated with somatosensory system: somatic senses (tactile, proprioceptive, etc.), special senses (vision, smell), and visceral sensations.

General properties of receptors

  • Sensitivity: High specificity for a particular stimulus.
  • Specificity: Transmit only one type of sensory information.
  • Receptor potential/generator potential: Produce a graded potential in response to a stimulus, which can trigger an action potential.

Adaptation of Receptors (Desensitization)

  • Tonic Receptors: Slowly and incompletely adapt (e.g., pain receptors, muscle spindles).
  • Phasic Receptors: Rapidly adapt (e.g., pressure receptors, smell).

Sensory Units & Receptive Fields

  • A sensory unit has a sensory neuron and the receptor regions whose activation affects it.
  • Receptive fields: Area stimulated with input leading to activation of sensory unit.
  • Increased recruitment of receptors with stronger stimulation.

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CNS 1 PDF

Description

Explore the intricate functions of the nervous system, including its role in coordinating bodily activities and maintaining homeostasis. This quiz covers the functional levels of the CNS, focusing on the spinal cord, lower brain, and higher brain, along with their specific roles and operations.

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