Neural Reflexes in Physiology
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Questions and Answers

What type of reflex is exemplified by the patellar reflex?

  • Disynaptic reflex
  • Monosynaptic reflex (correct)
  • Complex reflex
  • Polysynaptic reflex

What is the primary role of the sensory neuron in a stretch reflex?

  • To inhibit motor output
  • To relay sensory information (correct)
  • To initiate voluntary movement
  • To facilitate muscle contraction

Which component is involved in controlling movement at joints?

  • Cerebral cortex
  • Peripheral nerve
  • Efferent motor neuron
  • Myotactic unit (correct)

Where do the synapses of the integrating center for a stretch reflex primarily occur?

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

What defines the myotactic unit in the context of reflexes?

<p>The collection of reflex pathways controlling a joint (C)</p> Signup and view all the answers

What type of reflex is characterized by the integration of sensory information into an involuntary response?

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

Which of the following correctly describes monosynaptic reflexes?

<p>Consists of a single synapse between sensory and motor neurons (D)</p> Signup and view all the answers

In the classification of neural reflexes, what is the difference between somatic and autonomic reflexes?

<p>Somatic reflexes involve voluntary control while autonomic reflexes are involuntary (B)</p> Signup and view all the answers

What role do proprioceptors play in skeletal muscle reflexes?

<p>Provide feedback about muscle position and movement (C)</p> Signup and view all the answers

Which type of reflex is considered to have the capacity for divergence/convergence?

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

Which of the following is an example of a sensory receptor involved in autonomic reflexes?

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

What distinguishes learned reflexes from innate reflexes?

<p>Learned reflexes are acquired through experience (A)</p> Signup and view all the answers

Which statement accurately describes visceral muscle movement?

<p>It is primarily controlled by autonomic reflexes (A)</p> Signup and view all the answers

What is the primary role of synergists in muscle action?

<p>To assist in the contraction of a muscle. (B)</p> Signup and view all the answers

Which reflex is associated with the contraction of the quadriceps muscle?

<p>Stretch reflex. (B)</p> Signup and view all the answers

What is the result of reciprocal inhibition in muscle reflexes?

<p>Inhibition of the somatic alpha motor neuron. (D)</p> Signup and view all the answers

What characterizes the flexion (withdrawal) reflex?

<p>It moves the affected body part away from a stimulus. (A)</p> Signup and view all the answers

Which neuron is involved in facilitating the response in a stretch reflex?

<p>Alpha motor neuron. (A)</p> Signup and view all the answers

What occurs during the crossed extensor reflex?

<p>Contraction of the contralateral limb. (D)</p> Signup and view all the answers

Which type of reflex directly withdraws the ipsilateral limb from a painful stimulus?

<p>Flexion (withdrawal) reflex. (D)</p> Signup and view all the answers

What happens to extensors during a withdrawal reflex?

<p>They are inhibited. (A)</p> Signup and view all the answers

The somatic alpha motor neuron is primarily responsible for what function?

<p>Executing voluntary muscle contractions. (A)</p> Signup and view all the answers

Which statement correctly describes divergence in the spinal cord?

<p>It allows multiple motor responses to a single stimulus. (C)</p> Signup and view all the answers

What is the primary role of the crossed extensor reflex?

<p>To maintain balance when one foot is lifted (C)</p> Signup and view all the answers

Which part of the nervous system is responsible for integrating the least complex reflexes?

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

What is a function of central pattern generators?

<p>Maintaining repetitive activity (B)</p> Signup and view all the answers

Which structures work together for voluntary movements?

<p>Cerebral cortex, cerebellum, and basal nuclei (B)</p> Signup and view all the answers

What happens when the left foot is lifted?

<p>The right leg is activated to maintain balance (D)</p> Signup and view all the answers

How do interneurons function in the crossed extensor reflex?

<p>They stimulate contralateral extensor muscles (A)</p> Signup and view all the answers

Which structure is inaccurately referred to as 'basal ganglia'?

<p>Basal nuclei (D)</p> Signup and view all the answers

What role does the cerebellum play in motor control?

<p>Maintaining balance and posture (B)</p> Signup and view all the answers

What is the main function of the Golgi tendon organ?

<p>Provides feedback on muscle tension (A)</p> Signup and view all the answers

Where does integration of sensory information primarily occur for somatic reflexes?

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

Which component is NOT part of the autonomic reflex arc?

<p>Efferent neuron (D)</p> Signup and view all the answers

What type of receptor is stimulated by muscle stretch?

<p>Muscle spindle (D)</p> Signup and view all the answers

Which reflex is primarily responsible for regulating blood pressure?

<p>Visceral autonomic reflex (C)</p> Signup and view all the answers

Which part of the nervous system processes responses to both excitatory and inhibitory signals?

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

What stimulus do proprioceptors detect?

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

What type of neurons excite extrafusal muscle fibers?

<p>Alpha motor neurons (A)</p> Signup and view all the answers

Which response does the autonomic reflex NOT directly influence?

<p>Voluntary muscle movement (A)</p> Signup and view all the answers

Which of the following is a function of the muscle spindle?

<p>Senses changes in muscle length (D)</p> Signup and view all the answers

Which statement about visceral reflexes is true?

<p>They can involve the brainstem and hypothalamus. (D)</p> Signup and view all the answers

What is the primary role of sensory neurons in reflex arcs?

<p>To carry signals from receptors to the CNS (C)</p> Signup and view all the answers

Which reflex type is primarily concerned with maintaining muscle tone?

<p>Stretch reflex (D)</p> Signup and view all the answers

What type of muscle fibers are stimulated by alpha motor neurons?

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

What structure is primarily responsible for voluntary movements in the body?

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

Which of the following is not a major symptom of Parkinson's disease?

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

Which type of neuron is primarily found in the basal nuclei?

<p>Dopaminergic neurons (D)</p> Signup and view all the answers

How do cardiac and smooth muscles differ from skeletal muscles?

<p>They move lumenal contents rather than bones (A)</p> Signup and view all the answers

Which pathway is primarily involved in the control of skeletal muscle movement?

<p>Corticospinal pathway (D)</p> Signup and view all the answers

What happens to most corticospinal pathways in relation to the spinal cord?

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

How are visceral muscles typically controlled?

<p>Internal pacemaker and autonomic nervous system (D)</p> Signup and view all the answers

Which part of the nervous system influences the movement of cardiac and smooth muscles?

<p>Autonomic nervous system (C)</p> Signup and view all the answers

What neurological structure is most commonly affected in individuals with Parkinson's disease?

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

Which components are involved in the intrinsic control of smooth muscle movement?

<p>Internal pacemaker and hormones (C)</p> Signup and view all the answers

What is the primary characteristic of a monosynaptic reflex?

<p>Direct connection between sensory and motor neurons (A)</p> Signup and view all the answers

Which structure is crucial for detecting changes in muscle stretch within the myotactic unit?

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

What best defines the term 'myotactic unit' in the context of reflexes?

<p>A collection of pathways controlling a joint (A)</p> Signup and view all the answers

Which response most accurately describes the role of sensory neurons in the stretch reflex?

<p>They initiate the reflex response by relaying input to the spinal cord. (C)</p> Signup and view all the answers

In the context of the patellar reflex, which term best represents the integrating center?

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

What is the primary difference between monosynaptic and polysynaptic reflexes?

<p>Monosynaptic reflexes involve a single synapse. (D)</p> Signup and view all the answers

Which type of receptor is NOT classified as a sensory receptor in autonomic reflexes?

<p>Motor neurons (D)</p> Signup and view all the answers

Which statement accurately describes the role of divergence in polysynaptic reflexes?

<p>Divergence allows a single stimulus to produce effects on multiple targets. (D)</p> Signup and view all the answers

What differentiates innate reflexes from learned reflexes?

<p>Learned reflexes develop through experience. (B)</p> Signup and view all the answers

In the context of neural reflexes, the term 'tonic control' refers to what?

<p>Continuous modulation of activity of autonomic reflexes. (D)</p> Signup and view all the answers

Which of the following components is involved in the autonomic reflex arc?

<p>Postganglionic autonomic neuron (A)</p> Signup and view all the answers

In which part of the nervous system is the integration center for somatic reflexes primarily located?

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

What type of reflex is characterized by the integration of various inputs from multiple sources?

<p>Polysynaptic reflex (D)</p> Signup and view all the answers

What role do contralateral extensor muscles play during the crossed extensor reflex?

<p>They help maintain balance by holding up body weight. (B)</p> Signup and view all the answers

Which of the following structures is primarily responsible for voluntary movement control?

<p>Basal nuclei (D)</p> Signup and view all the answers

What are central pattern generators primarily responsible for?

<p>Maintaining repetitive activities (D)</p> Signup and view all the answers

In what circumstance do flexors get inhibited according to the reflexive response?

<p>When lifting the left foot (B)</p> Signup and view all the answers

How does the body react when weight shifts to the left leg?

<p>Extensors contract on the left leg. (A)</p> Signup and view all the answers

Which type of reflex is characterized by the response of lifting one foot leading to the extension of the other leg?

<p>Crossed extensor reflex (C)</p> Signup and view all the answers

Which of the following best describes the role of the cerebellum?

<p>Coordinating postural reflexes and balance (C)</p> Signup and view all the answers

What happens during the activation of the crossed extensor reflex?

<p>Interneurons stimulate extensor muscles in the opposite leg. (D)</p> Signup and view all the answers

What is the primary function of the withdrawal reflex?

<p>To move the affected body part away from a painful stimulus (C)</p> Signup and view all the answers

Which statement accurately describes the role of antagonists in muscle action?

<p>They inhibit the contraction of the agonist muscle (C)</p> Signup and view all the answers

During the stretch reflex, what role does the interneuron play?

<p>It inhibits the somatic alpha motor neuron to prevent contraction (B)</p> Signup and view all the answers

What occurs in the crossed extensor reflex following a painful stimulus?

<p>The contralateral limb is extended while the ipsilateral limb is flexed (C)</p> Signup and view all the answers

What type of muscle fibers are primarily stimulated by alpha motor neurons?

<p>Extrafusal muscle fibers (C)</p> Signup and view all the answers

What is the immediate result of reciprocal inhibition in a muscle reflex?

<p>The agonist muscle is contracted while the antagonist is inhibited (C)</p> Signup and view all the answers

Which structure plays a critical role in the divergence of signals within the spinal cord during reflexes?

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

What role do nociceptors play in reflex actions?

<p>They transmit pain signals to the spinal cord and brain (B)</p> Signup and view all the answers

In which reflex is the term 'divergence' most relevant?

<p>Crossed extensor reflex (D)</p> Signup and view all the answers

What is the primary response of the quadriceps muscle during a stretch reflex?

<p>Contraction to stabilize the knee (A)</p> Signup and view all the answers

What is the primary pathway utilized for voluntary movements?

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

Which basal nuclei structure is notably impacted in Parkinson's disease?

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

Which of the following is NOT a major motor symptom of Parkinson's disease?

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

How do cardiac and smooth muscles primarily differ from skeletal muscles in their control?

<p>They can contract autonomously (A)</p> Signup and view all the answers

What type of neuron initiates the voluntary movement signal from the primary motor cortex?

<p>Upper motor neuron (A)</p> Signup and view all the answers

What role do intrinsic gap junctions play in muscle movement control?

<p>They facilitate communication between cardiac muscle cells (D)</p> Signup and view all the answers

Which pathway is primarily involved in integrating the control of skeletal muscle movements?

<p>Lateral corticospinal tract (A)</p> Signup and view all the answers

What is the function of the dopaminergic neurons located in the basal nuclei?

<p>Facilitating voluntary movement (C)</p> Signup and view all the answers

Which cranial structure is responsible for transmitting motor signals to skeletal muscles?

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

In the context of human movement control, what do the pyramids refer to?

<p>Corticospinal pathways that cross over (C)</p> Signup and view all the answers

What is one primary function of the Golgi tendon organ?

<p>Provide feedback for posture maintenance (B)</p> Signup and view all the answers

Which structure is primarily involved in integrating sensory information for skeletal muscle reflexes?

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

Which type of reflex is characterized by connections involving interneurons?

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

Which component of the reflex arc is responsible for carrying signals away from the central nervous system to the target muscle?

<p>Efferent neuron (D)</p> Signup and view all the answers

What aspect is primarily regulated by autonomic reflexes?

<p>Involuntary bodily functions (D)</p> Signup and view all the answers

Which of the following best describes the role of preganglionic autonomic neurons?

<p>They transmit signals to postganglionic neurons (A)</p> Signup and view all the answers

Which receptor type plays a key role in detecting changes in muscle tension?

<p>Golgi tendon organ (C)</p> Signup and view all the answers

What physiological response is generally initiated by visceral reflexes?

<p>Altered heart rate (D)</p> Signup and view all the answers

How does the muscle spindle contribute to reflex action during stretch?

<p>By providing sensory feedback about stretch (C)</p> Signup and view all the answers

Which part of the nervous system is directly responsible for controlling involuntary reflexes?

<p>Autonomic nervous system (D)</p> Signup and view all the answers

In which location does integration of autonomic reflexes primarily occur?

<p>Spinal cord (D)</p> Signup and view all the answers

Which of the following is NOT a target for responses mediated by autonomic reflexes?

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

What role do interneurons serve in reflex arcs?

<p>They connect sensory and motor pathways (D)</p> Signup and view all the answers

Which reflex mechanism is primarily involved in protecting against muscle overstretching?

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

Flashcards

Neural reflex

An involuntary response triggered by sensory input, processed by the nervous system.

Autonomic reflex

A reflex mediated by the autonomic nervous system, controlling involuntary functions like heart rate and digestion.

Somatic reflex

A reflex mediated by the somatic nervous system, controlling voluntary muscle movements.

Monosynaptic reflex

A reflex involving only one synapse between the sensory neuron and motor neuron.

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Polysynaptic reflex

A reflex involving multiple synapses between multiple neurons.

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Proprioceptors

Sensory receptors located in muscles, tendons, and joints, providing information about body position and movement.

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Divergence in reflexes

A single stimulus activating multiple motor neurons, allowing for coordinated responses to multiple targets.

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Convergence in reflexes

Multiple stimuli integrating into a single response, allowing for complex responses to various inputs.

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Stretch Reflex Example

The patellar reflex is an example of a stretch reflex, where a tap on the tendon below the kneecap causes extension of the leg.

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Myotactic Unit

A myotactic unit is a group of pathways that control movement at a joint, involving sensory neurons, muscle spindles, and integrating centers in the spinal cord.

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Muscle Spindle Role

Muscle spindles are sensory receptors within muscles that detect muscle length and stretching.

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Integrating Center

The integrating center in a myotactic unit is located in the spinal cord and receives sensory input from the muscle spindle before sending signals to motor neurons.

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Synergists

Muscles that work together to produce a movement, helping the primary muscle.

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Antagonists

Muscles that oppose the action of another muscle, creating a balanced movement.

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Stretch Reflex

A reflex that causes a muscle to contract in response to a stretching stimulus.

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Reciprocal Inhibition

A reflex that inhibits the antagonist muscle while the agonist muscle is contracting.

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Flexion (Withdrawal) Reflex

A reflex that causes a limb to withdraw from a painful stimulus.

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What are the roles of synergists and antagonists in movement?

Synergists enhance the prime mover's action, while antagonists oppose it, creating controlled movement.

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What is the function of the stretch reflex?

The stretch reflex protects muscles from overstretching by contracting the muscle when stretched.

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Explain how the flexion (withdrawal) reflex protects the body

The flexion reflex moves a limb away from a painful stimulus, preventing further injury.

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Visceral Sensory Receptor

A specialized sensory receptor that detects changes in internal organs, such as pressure, temperature, or chemical composition.

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Preganglionic Autonomic Neuron

A neuron that originates in the CNS and transmits signals to a ganglion in the autonomic nervous system.

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Postganglionic Autonomic Neuron

A neuron in the autonomic nervous system that receives signals from a ganglion and transmits them to the target organ or tissue.

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Autonomic Ganglion

A cluster of nerve cell bodies in the autonomic nervous system where preganglionic neurons synapse with postganglionic neurons.

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Target Cell

The specific cell, tissue, or organ that is affected by the signals transmitted by the nervous system.

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Interneuron

A neuron that connects other neurons within the CNS.

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Somatic Alpha Motor Neuron

A neuron that originates in the CNS and controls the contraction of skeletal muscle fibers.

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Tonic Output

A continuous, low-level signal that is maintained by a neuron.

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Extrafusal Muscle Fiber

A skeletal muscle fiber that is directly involved in muscle contraction.

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Golgi Tendon Organ

A sensory receptor located within a tendon that detects changes in muscle tension.

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Muscle Spindle

A sensory receptor located within a muscle that detects changes in muscle length.

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Crossed Extensor Reflex

A postural reflex that maintains balance by extending the opposite leg when the other leg is lifted. It's activated when the foot is lifted from the ground, for instance, when stepping on a tack. Sensory input from the painful stimulus crosses to the opposite side of the spinal cord, stimulating the contralateral extensor muscles and inhibiting the flexors on that side.

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Central Pattern Generators

Groups of interneurons in the spinal cord that generate repetitive, rhythmic patterns of neural activity. These patterns are responsible for coordinated movements, such as breathing or walking.

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Spinal Cord in Movement Control

The simplest level of motor control. Integrates reflexes and houses central pattern generators for rhythmic movements. Can be modulated by higher brain centers for more complex actions.

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Cerebellum's Role in Movement

The cerebellum refines movement coordination, postural reflexes, and balance, as well as hand-eye coordination.

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Basal Nuclei Function

A collection of structures involved in movement planning, decision-making, and initiating movements. They work closely with the cerebral cortex to generate smooth, coordinated movements.

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Cerebral Cortex in Movement Control

The highest level of motor control, responsible for planning, initiating, and executing complex voluntary movement sequences. It receives input from the basal nuclei and cerebellum.

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Ascending Tract

A pathway of nerve fibers that carry sensory information from the body (e.g., pain, temperature) to the brain. It's crucial for relaying information needed for movement coordination.

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Why is 'Basal Ganglia' inaccurate?

The term 'ganglia' refers to clusters of neurons located outside the central nervous system. Basal nuclei are deep within the brain, not peripheral ganglia. The term 'basal nuclei' is more accurate because it reflects their location.

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Voluntary Movement Control

Consciously controlled movements, utilizing the corticospinal tract connecting the primary motor cortex to muscles.

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Extra-pyramidal Tracts

Neural pathways outside of the corticospinal tract, involved in coordination and fine control of movement. They involve the basal nuclei, which are groups of neurons that help to smooth and refine movements.

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Basal Nuclei

Groups of neurons that play a crucial role in regulating movement, learning, and planning. They include the substantia nigra, involved in movement initiation and coordination.

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Parkinson's Disease

A neurodegenerative disease characterized by tremor, slow movements, and rigidity, primarily due to damage to the dopaminergic neurons in the substantia nigra.

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Dopaminergic Neurons

Neurons that use dopamine as a neurotransmitter, crucial for smooth movement control and other brain functions. These neurons are found in the substantia nigra and other areas of the brain.

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Visceral Muscle Control

Regulation of involuntary movements of smooth and cardiac muscle, mainly involving the autonomic nervous system.

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Internal Pacemaker

A specialized group of cells within the heart that generates electrical impulses, controlling the rhythm of heartbeats.

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Gap Junctions

Direct connections between cells that allow for rapid communication and synchronized activity, important in coordinating smooth muscle contraction.

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Autonomic Nervous System

The part of the peripheral nervous system that controls involuntary functions such as heart rate, digestion, and breathing, playing a major role in regulating visceral muscle activity.

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Hormonal Control of Visceral Muscles

Hormones can influence visceral muscle activity, providing a longer-lasting, widespread effect on muscle contraction.

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What are autonomic reflexes?

Involuntary, controlled by the autonomic nervous system. Regulate vital functions, like heart rate and digestion.

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What is the integrating center of a reflex?

The part of the CNS that processes sensory input and decides on a response. Can be in the spinal cord, brainstem, etc.

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What is a visceral receptor?

A sensory receptor in internal organs, like the heart or stomach. Detects changes like pressure or chemicals.

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What is a preganglionic neuron?

An autonomic neuron that starts in the CNS and relays signals to a ganglion.

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What is a postganglionic neuron?

An autonomic neuron that picks up the signal from a ganglion and sends it to the target organ.

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What is an autonomic ganglion?

A cluster of neurons outside the CNS where preganglionic neurons synapse with postganglionic neurons.

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What is a somatic reflex?

A reflex controlled by the somatic nervous system. Affects skeletal muscles, like the knee-jerk reflex.

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What are proprioceptors?

Sensory receptors in muscles, tendons, and joints. They tell the brain about body position and movement.

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What is a Golgi tendon organ?

A proprioceptor in tendons, sensitive to muscle tension.

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What is a muscle spindle?

A proprioceptor in muscles, sensitive to stretching.

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What are intrafusal fibers?

Modified muscle fibers inside a muscle spindle. They are sensory receptors.

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What are extrafusal fibers?

Regular muscle fibers that contract and cause movement.

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What is the stretch reflex?

A reflex that causes a muscle to contract when it is stretched. Helps prevent muscle damage.

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What is reciprocal inhibition?

When a muscle contracts, its opposing muscle is inhibited. Allows controlled movement.

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Gray Matter & Somatic Alpha Motor Neuron

Gray matter in the spinal cord contains the cell bodies (somas) of somatic alpha motor neurons, which control skeletal muscle contraction.

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White Matter & Ascending Pathways

White matter in the spinal cord contains pathways of axons that transmit sensory information to the brain, crucial for coordinating complex movements.

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Interneuron & Reciprocal Inhibition

Interneurons in the spinal cord play a crucial role in reciprocal inhibition, inhibiting the antagonist muscle while the agonist is active.

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Spinal Cord in Movement

The simplest level of movement control: integrates reflexes, houses central pattern generators (CPGs) for rhythmic movements, and can be modulated by higher brain centers.

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Central Pattern Generator (CPG)

Groups of interneurons in the spinal cord that generate repetitive, rhythmic patterns for movement, like breathing or walking.

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Cerebellum's Role

Refines movement coordination, contributes to postural reflexes, balance, and hand-eye coordination.

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Cerebral Cortex in Movement

The highest level of motor control, responsible for planning, initiating, and executing complex voluntary movement sequences.

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What are neural reflexes?

Involuntary responses triggered by sensory input. The nervous system integrates sensory information and generates a reaction.

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What are the types of reflexes based on the efferent division?

Somatic reflexes control skeletal muscles, while autonomic reflexes control smooth muscle and glands.

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How are reflexes classified based on their integrating center?

Reflexes can be integrated in the brain or the spinal cord.

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What are the different levels of motor control?

The spinal cord, cerebellum, basal nuclei, and cerebral cortex each contribute to different aspects of movement control, from simple reflexes to complex motor plans.

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Study Notes

Control of Body Movement

  • Body movement is controlled by a complex interplay of neural and other mechanisms.
  • The nervous system integrates sensory information to produce involuntary and voluntary movements.
  • Reflexes are rapid, involuntary responses to stimuli.
  • Neural reflexes involve the integration of sensory information into an involuntary response.
  • Autonomic reflexes control the actions of smooth and cardiac muscle, and glands.
  • Skeletal muscle reflexes involve the contraction of skeletal muscles.
  • Proprioceptors are specialized sensory receptors that detect position and movement.
  • Muscle spindles and Golgi tendon organs are key proprioceptors.
  • The cerebellum plays a crucial role in integrating sensory information for coordination and balance, including postural reflexes and hand-eye movements.
  • Voluntary movements are coordinated by the cerebral cortex, cerebellum, and basal nuclei. Basal nuclei are involved in planning and initiating movements and the corticospinal tract is crucial.
  • Visceral reflexes control the actions of smooth and cardiac muscles and glands.
  • Visceral reflexes involve various receptors: osmoreceptors, chemoreceptors, baroreceptors, touch receptors, thermoreceptors, special senses
  • Visceral reflexes may be controlled by the spinal cord, hypothalamus, thalamus, brainstem, and the limbic system.
  • Visceral reflexes can cause excitation or inhibition of various bodily functions.
  • Different types of classifying reflexes: innate, learned reflexes, somatic reflexes (skeletal muscles), vs. visceral reflexes (smooth and cardiac muscles)
  • Classifying by integration site: cranial reflexes, spinal reflexes

Classifying Neural Reflexes

  • Efferent division: Two types: somatic and autonomic
  • Location of integration: Can occur in the brain or spinal cord
  • Innate or learned?: Some reflexes are innate, others learned
  • Number of synapses: Monosynaptic (one synapse) and polysynaptic (more than one synapse) reflexes

Classifying Autonomic Reflexes

  • Regulate homeostasis (e.g., heart rate, blood pressure, breathing)
  • Includes salivary, swallowing, gagging, coughing, sneezing, and vomiting.

Components of a Somatic (Skeletal Muscle) Reflex

  • Receptors (proprioceptors)
    • Joint receptors: stimulated by mechanical distortion (Pacinian, Ruffinian)
    • Golgi tendon organs: stimulated by muscle tension
    • Muscle spindles: stimulated by stretch
  • Stimulus and Response: The reflex arc begins with a stimulus, which is detected by a receptor. This triggers an action potential in a sensory neuron that passes to the spinal cord, where synapses and interneurons occur.
  • Sensory neuron: transmits signal from receptor.
  • Motor neuron: sends signal from spinal cord to effector.
  • Synapses: relay station within CNS through interneurons.
  • Effector: the skeletal muscle

Muscle Spindles & Golgi Tendon Organs

  • Muscle Spindles: Specialized receptors that detect changes in muscle length and help maintain posture and control movement.
  • Golgi Tendon Organs: Receptors that monitor the tension in the tendons and provide feedback about muscular contractions.

Muscle Spindles During Stretch

  • Muscle spindles respond to changes in muscle length (stretching).
  • This leads to a reflex contraction, to prevent overstretching and maintain posture.

A Stretch Reflex = Patellar Reflex

  • A monosynaptic reflex arc (one synapse) between sensory and motor neurons.
  • Small time delay between the stimulus (stretch) and response (contraction).

Controlling Movement at Joints

  • Myotactic unit: the collection of pathways controlling a joint.
  • Includes: Synergists, Antagonists
  • Classified by Reflex Type: Stretch reflexes and Reciprocal inhibition reflexes.

Flexion (Withdrawal) Reflex

  • Moves body parts away from a stimulus (e.g., a painful stimulus).

Flexion (Withdrawal) Reflex - Divergence

  • Contraction of one limb (ipsilateral) and extension of the contralateral limb are involved (divergence).

Crossed Extensor Reflex

  • Maintains balance during withdrawal.
  • Stimulates contralateral muscles to maintain balance; extension of the opposite limb.

Levels of Motor Control

  • Spinal cord: Reflexes, Central pattern generators controlling repetitive activities (e.g. breathing, walking)
  • Cerebellum: Postural reflexes, balance, and hand-eye movements. Motor coordination and error correction.
  • Cerebral cortex + basal nuclei: Decision making, planning, movement initiation, and voluntary movements, utilising the corticospinal tract. Higher level motor control

Where exactly are the Basal Nuclei?

  • Deep within the cerebrum.

Voluntary Movements and the Corticospinal Tract

  • Voluntary movements use the corticospinal tract as the main pathway from the brain to muscles.
  • Upper motor neurons: begin in the cerebral cortex, descend through the spinal cord brainstem, synapse with lower motor neurons.
  • Lower motor neurons: located in the spinal cord and brainstem, sending axons to the skeletal muscles.

Differences in Control of Visceral Muscles

  • Cardiac and smooth muscles differ from skeletal muscles in control mechanisms.
  • Controlled by internal pacemakers, intrinsic gap junctions, the autonomic nervous system (ANS), and hormones and often involve the spinal cord for reflexes and other regions of brain for more complex signals.

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BIO 305 Chapter 13 Reflexes Student Copy PDF

Description

Test your knowledge on neural reflexes, including the patellar reflex, sensory neurons' roles, and the classification of reflexes. This quiz covers various aspects of both somatic and autonomic reflexes as part of physiology studies. Dive into the fascinating world of reflex actions and muscle control.

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