Reflexes and Sensory Pathways

Questions and Answers

How does reflex time change if the stimulus intensity is increased?

If the stimulus intensity is increased, the reflex time will be decreased.

What does the spinothalamic system transmit?

Pain, temperature, and crude touch.

What does the posterior column-medial lemniscus pathway convey?

Touch, pressure, vibration, and conscious proprioception.

How does 2-point discrimination vary across different body regions?

Face is accurate Signup and view all the answers

What is the reason for differences in 2-point discrimination across body regions?

Due to the amount of mechanoreceptors and afferents in different body areas. Signup and view all the answers

What are common reflexes?

Coughing, sneezing, yawning, shivering. Signup and view all the answers

What is a reflex?

Reflexes are involuntary movements occurring almost immediately after a stimulus. Signup and view all the answers

Why does the brain still receive signals during a reflex response?

To allow for conscious awareness of the stimulus and wider responses. Signup and view all the answers

How many neurons are in monosynaptic reflex pathways?

One sensory neuron and one motor neuron. Signup and view all the answers

How many neurons are in polysynaptic reflex pathways?

At least three neurons: one sensory neuron, one or more interneurons, and one motor neuron. Signup and view all the answers

What is an example of a polysynaptic reflex?

Withdrawal reflex. Signup and view all the answers

What is a stretch reflex?

Involuntary contraction of a muscle due to rapid stretching. Signup and view all the answers

The _____ reflex is the fastest of all spinal reflexes.

stretch Signup and view all the answers

What does the stretch reflex prevent?

Tearing. Signup and view all the answers

What causes hyperactive or exaggerated reflex responses?

Upper motor neuron lesion. Signup and view all the answers

What is a muscle spindle?

A sensory receptor located in a muscle that senses its tension. Signup and view all the answers

What reflex response occurs due to inflammation of nerve ends?

Diminished (lower motor neuron lesion). Signup and view all the answers

What is a flexion withdrawal reflex?

It mediates the withdrawal of a limb from a painful stimulus. Signup and view all the answers

What are pain sensory neurons also known as?

Both A and B Signup and view all the answers

What is the function of the crossed extensor reflex?

To support the body during the withdrawal of the injured limb. Signup and view all the answers

What occurs during a crossed extensor reflex?

Strength is increased in the opposite leg to support body weight during withdrawal. Signup and view all the answers

Study Notes

Reflex Time and Stimulus

Increased stimulus intensity leads to decreased reflex time.

Spinothalamic System

Responsible for transmitting sensations of pain, temperature, and crude touch.

Posterior Column-Medial Lemniscus Pathway

Conveys nerve impulses related to touch, pressure, vibration, and conscious proprioception to the cerebral cortex.

Two-Point Discrimination

Trunk: Poor discrimination ability.
Face: Highly accurate discrimination.
Fingers: Most precise discrimination ability.

Mechanoreceptor Distribution

Differences in discrimination sensitivity are due to varying amounts of mechanoreceptors and afferents in different body areas.
High convergence in the back leads to lower sensitivity.
Low convergence in fingers leads to higher accuracy in sensation detection.

Common Reflexes

Examples include coughing, sneezing, yawning, and shivering.

Definition of a Reflex

Reflexes are involuntary movements that occur immediately after stimulus; they process through reflex arcs in the spinal cord for quick responses.

Brain and Reflex Responses

Simultaneous transmission of signals to the brain allows for conscious awareness and broader responses to stimuli.

Monosynaptic Reflex Pathways

Comprise one sensory neuron and one motor neuron.

Polysynaptic Reflexes

Involves at least three neurons: one sensory neuron, one or more interneurons, and one motor neuron.

Polysynaptic Reflex Example

Withdrawal reflex serves as an example of a polysynaptic reflex.

Stretch Reflex

Involuntary contraction of a muscle occurs due to rapid stretching; regarded as a monosynaptic reflex or myotatic reflex.
Fastest spinal reflex.

Purpose of Stretch Reflex

Protects muscles from tearing during overstretching.

Hyperactive Reflex Response

Indicative of an upper motor neuron lesion, resulting from the loss of tonic inhibition from the cerebral cortex over lower motor neurons.

Muscle Spindle Function

Sensory receptors in muscles that detect tension and changes in muscle length.
Critical for initiating reflexes and regulating muscle contraction to prevent overstretching.

Reflex Response and Nerve Damage

Inflammation or sensory receptor damage can lead to a diminished reflex response, indicating lower motor neuron lesions.

Flexion Withdrawal Reflex

Mediates limb withdrawal from painful stimuli and is classified as a polysynaptic reflex.

Pain Sensory Neurons

Also known as nociceptive neurons or nociceptors.

Crossed Extensor Reflex

Supports the opposite limb during the withdrawal of an injured limb, allowing for weight distribution.

Function of Crossed Extensor Reflex

Upon sensing pain in a foot, this reflex causes withdrawal while increasing support in the opposite leg to maintain balance.

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Description

Test your knowledge on reflex time, the spinothalamic system, and the posterior column-medial lemniscus pathway. Understand how mechanoreceptor distribution affects two-point discrimination and learn about common reflexes in the human body.