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Questions and Answers
What characterizes somatic reflexes?
What characterizes somatic reflexes?
- Quick, involuntary, and stereotyped reactions. (correct)
- Conscious, adaptable, and emotional responses.
- Slow, voluntary, and variable reactions.
- Prolonged, voluntary, and unpredictable actions.
Somatic reflexes exclusively involve glandular secretions.
Somatic reflexes exclusively involve glandular secretions.
False (B)
What is the role of afferent nerve fibers in a somatic reflex arc?
What is the role of afferent nerve fibers in a somatic reflex arc?
To carry sensory information from the receptors to the spinal cord.
In a reflex arc, the integrating center primarily consists of ______ of the spinal cord's gray matter.
In a reflex arc, the integrating center primarily consists of ______ of the spinal cord's gray matter.
What is the function of efferent nerve fibers in a reflex arc?
What is the function of efferent nerve fibers in a reflex arc?
Effectors in a reflex arc are the sensory receptors that detect stimuli.
Effectors in a reflex arc are the sensory receptors that detect stimuli.
What type of receptors are muscle spindles?
What type of receptors are muscle spindles?
Muscle spindles inform the brain of muscle ______ and body movements, which helps control posture and balance.
Muscle spindles inform the brain of muscle ______ and body movements, which helps control posture and balance.
What is the main function of the stretch reflex?
What is the main function of the stretch reflex?
The stretch reflex decreases muscle tone.
The stretch reflex decreases muscle tone.
How many modified muscle fibers are typically found within a muscle spindle?
How many modified muscle fibers are typically found within a muscle spindle?
Stretch reflexes often involve feedback to pairs or sets of ______ muscles.
Stretch reflexes often involve feedback to pairs or sets of ______ muscles.
In the context of a reflex arc, what directly stimulates the quadriceps to contract and produce the knee-jerk reaction?
In the context of a reflex arc, what directly stimulates the quadriceps to contract and produce the knee-jerk reaction?
The hamstring muscles contract during the quadriceps contraction in the knee-jerk reflex.
The hamstring muscles contract during the quadriceps contraction in the knee-jerk reflex.
What is the role of muscle spindles in monitoring body position and movement, and what type of receptors are they considered?
What is the role of muscle spindles in monitoring body position and movement, and what type of receptors are they considered?
In a stretch reflex, tapping the patellar ligament especially excites the nerve endings of the muscle spindle in the ______.
In a stretch reflex, tapping the patellar ligament especially excites the nerve endings of the muscle spindle in the ______.
What is the pathway for stretch signals traveling to the spinal cord within a reflex arc?
What is the pathway for stretch signals traveling to the spinal cord within a reflex arc?
The branch of the afferent nerve fiber stimulates motor neuron that supplies hamstring muscles.
The branch of the afferent nerve fiber stimulates motor neuron that supplies hamstring muscles.
What diagnostic insights can be gained from testing somatic reflexes?
What diagnostic insights can be gained from testing somatic reflexes?
Match each component of the reflex arc with its function.
Match each component of the reflex arc with its function.
Flashcards
Reflexes
Reflexes
Quick, involuntary, stereotyped reactions of glands or muscles to stimulation.
Somatic Reflexes
Somatic Reflexes
Reflexes involving skeletal muscle.
Somatic Reflex Arc Steps
Somatic Reflex Arc Steps
Somatic receptors sense input; afferent fibers carry sensory information to the spinal cord; the pathway moves through an integrating center; efferent fibers carry motor impulses; effectors contract.
Muscle Spindles
Muscle Spindles
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Proprioceptors
Proprioceptors
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Muscle Spindle Function
Muscle Spindle Function
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The Stretch Reflex
The Stretch Reflex
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Study Notes
Somatic Reflexes
- Reflexes are quick, involuntary, stereotyped reactions of glands or muscles to stimulation.
- Reflexes may include glandular secretion or contractions of all three types of muscle.
- Reflexes involving skeletal muscle are called somatic reflexes.
Reflex Arcs
- A somatic reflex arc includes a series of steps:
- Somatic receptors in the skin, muscles, or tendons sense an input.
- Afferent nerve fibers carry sensory information from the receptors to the spinal cord.
- The pathway moves through an integrating center, comprised of interneurons in the spinal cord's gray matter, or afferent neurons synapse directly onto efferent neurons in some reflexes.
- Efferent nerve fibers carry motor impulses to the muscles.
- Effectors, which are the muscles, contract to carry out the response.
Muscle Spindles
- Many somatic reflexes involve stretch receptors called muscle spindles, which are embedded in the muscles.
- Muscle spindles are proprioreceptors that monitor position and movement.
- Muscle spindles inform the brain of muscle length and body movements.
- The brain then sends motor commands back to the muscle to control muscle tone, posture, and balance.
- Muscle spindles consist of seven or eight modified muscle fibers enclosed in a fibrous capsule.
The Stretch Reflex
- The stretch reflex occurs when a muscle is suddenly stretched, causing it to contract and increase tone to become stiffer.
- This response helps maintain posture.
- Stretch reflexes often feed back to pairs or sets of antagonistic muscles.
- The process occurs when tap on the patellar ligament excites nerve endings of muscle spindle in quadriceps femoris.
- Stretch signals travel to the spinal cord via the primary afferent fiber and dorsal root.
- The primary afferent neuron stimulates the alpha motor neuron in the spinal cord.
- Efferent signals in the alpha motor nerve fiber stimulate the quadriceps to contract and producing a knee jerk.
- Simultaneously, a branch of the afferent nerve fiber stimulates an inhibitory motor neuron in the spinal cord.
- That neuron inhibits the alpha motor neuron that supplies hamstring muscles.
- Hamstring contraction is inhibited so hamstrings (knee flexors) do not antagonize quadriceps (knee extensor).
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