Neuroscience: Reflexes and Nerve Function

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Questions and Answers

What reflex would most likely be affected by a lower motor nerve lesion?

Quadriceps – Patellar (correct)

Biceps brachii

Gastrocnemius/soleus - Achilles

Triceps brachii

What does a hyperactive reflex indicate?

A lower motor nerve lesion

A normal response

Peripheral nerve damage

A central nervous system lesion (correct)

How are reflexes graded when they are absent?

0 (correct)

Which test would assess proprioception?

Where your body is in space Signup and view all the answers

What is a characteristic of lower motor nerve lesions when testing reflexes?

Decreased reflexes Signup and view all the answers

Which part of the brain is continuous with the spinal cord?

Brain Stem Signup and view all the answers

What is the primary function of the spinal cord?

Carrying signals between the brain and peripheral nerves Signup and view all the answers

Which cranial nerve is responsible for the sense of smell?

Olfactory Nerve Signup and view all the answers

How many cranial nerves are there in humans?

12 Signup and view all the answers

Which structure is located posterior to the brainstem?

Cerebellum Signup and view all the answers

Which of the following is NOT a part of the diencephalon?

Midbrain Signup and view all the answers

What is the function of the oculomotor nerve?

Eye movement and pupil reflex Signup and view all the answers

Which cranial nerve is involved in throat sensation, taste, and swallowing?

Glossopharyngeal Nerve Signup and view all the answers

What is the role of lower motor neurons (LMNs) in the motor pathway?

They receive signals from upper motor neurons. Signup and view all the answers

Which of the following describes the corticospinal pathway?

It travels through the brainstem and spinal cord. Signup and view all the answers

What typically results from damage to the corticospinal pathway?

Motor deficits such as paralysis. Signup and view all the answers

What is a primary function of the motor pathways in the nervous system?

To coordinate and control voluntary muscle movements. Signup and view all the answers

Where do upper motor neurons (UMNs) originate?

In the primary motor cortex. Signup and view all the answers

Which pathway is NOT classified as a primary motor pathway?

Somatosensory pathway. Signup and view all the answers

Which statement about motor pathway disruptions is correct?

They may cause tremors or weakness in movements. Signup and view all the answers

What is the outcome when lower motor neurons (LMNs) receive signals from upper motor neurons (UMNs)?

They innervate skeletal muscles to cause contractions. Signup and view all the answers

What is the primary role of the extrapyramidal pathway?

Regulating muscle tone and involuntary movements Signup and view all the answers

Which spinal segment is primarily responsible for transmitting signals to and from the legs and feet?

Lumbar Spine Signup and view all the answers

Which myotome is responsible for elbow flexion and wrist extension?

C6 Signup and view all the answers

What do dermatomes primarily relate to?

Areas of skin supplied by sensory fibers from a single spinal nerve Signup and view all the answers

Which spinal segment corresponds to knee flexion?

S2 Signup and view all the answers

How many cervical spine segments are there?

7 Signup and view all the answers

Which of the following structures is formed by fused vertebrae?

Sacral segments Signup and view all the answers

Which myotome allows for shoulder elevation?

C4 Signup and view all the answers

What function do myotomes serve?

Providing motor fibers to specific muscles Signup and view all the answers

Which spinal segments are responsible for transmitting signals from pelvic organs?

Lumbar and Sacral Signup and view all the answers

What is the primary characteristic of neonatal reflexes?

They occur involuntarily in response to stimuli. Signup and view all the answers

At what age is the Moro (startle) reflex typically integrated?

2 – 4 months Signup and view all the answers

Which reflex is responsible for an infant grasping an object placed in their palm?

Palmar grasp reflex Signup and view all the answers

What is the potential outcome of retaining the asymmetrical tonic neck reflex?

Poor head control and balance Signup and view all the answers

Which reflex is likely to cause feeding issues due to its retention?

Rooting reflex Signup and view all the answers

When is the Babinski reflex typically observed to disappear?

8 – 12 months Signup and view all the answers

Which reflex is considered permanent and assists in orienting to auditory stimuli?

Auditory orienting reflex Signup and view all the answers

How are developmental reflexes significant clinically?

They reflect brain to spinal cord signaling. Signup and view all the answers

What is the primary location of upper motor neuron (UMN) lesions?

Central nervous system Signup and view all the answers

Which of the following symptoms is characteristic of upper motor neuron lesions?

Hyperactive reflexes Signup and view all the answers

What type of muscle tone is associated with lower motor neuron (LMN) lesions?

Hypotonia Signup and view all the answers

Which of the following conditions is a typical example of an upper motor neuron lesion?

Cerebral palsy Signup and view all the answers

What is a common outcome of lower motor neuron lesions?

Atrophy of muscles Signup and view all the answers

Which symptom is typically absent in lower motor neuron lesions?

Increased muscle tone Signup and view all the answers

What characterizes spasticity as it relates to upper motor neuron lesions?

Increased muscle resistance during passive movement Signup and view all the answers

How does the location of lesions differentiate upper motor neuron lesions from lower motor neuron lesions?

UMN lesions are within the central nervous system, while LMN lesions are in the peripheral nervous system Signup and view all the answers

Which of the following might be a symptom of both upper and lower motor neuron lesions?

Muscle paralysis Signup and view all the answers

What phenomenon is commonly associated with upper motor neuron lesions, but not with lower motor neuron lesions?

Hypertonia Signup and view all the answers

In cases of lower motor neuron lesions, reflexes are usually:

Reduced or absent Signup and view all the answers

Which neurological condition is specifically a result of lower motor neuron damage?

Amyotrophic lateral sclerosis (ALS) Signup and view all the answers

Hyperactive reflexes in upper motor neuron lesions are primarily due to:

Disrupted inhibitory signals from the brain Signup and view all the answers

Study Notes

CNS Anatomy: Brain and Spinal Cord

The spinal cord connects to the brainstem and runs through the spinal canal.
Cranial nerves exit the brainstem, nerve roots exit the spinal cord.
The spinal cord transmits signals between the brain and peripheral nerves.
It controls various bodily functions including awareness, movement, thoughts, speech, memory, etc.

Major Brain Parts

Brainstem: Continuous with the spinal cord, containing the medulla oblongata, pons, and midbrain.
Cerebellum: Located posterior to the brainstem.
Diencephalon: Superior to the brainstem, containing the thalamus, hypothalamus, and epithalamus.
Cerebrum: The largest part of the brain, situated on the diencephalon.

Cranial Nerves

Twelve cranial nerves emerge from the skull.
They transmit sensory and motor information and include the olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal, vagus, accessory, and hypoglossal nerves.

Motor Pathways

Motor pathways transmit signals from the brain to muscles, enabling voluntary movements.
The corticospinal and extrapyramidal pathways are primary motor pathways.
Corticospinal Pathway: Originates in the primary motor cortex, involves upper motor neurons (UMNs) traveling through the internal capsule, brainstem, and spinal cord, synapsing with lower motor neurons (LMNs) in the spinal cord, which then signal to muscles, causing their contraction.
Extrapyramidal Pathway: Involves multiple subcortical nuclei and brain regions, controlling muscle tone, posture, and involuntary movements, having more complex connections than the corticospinal pathway.

Spinal Segments

The spinal cord is divided into segments: cervical (7), thoracic (12), lumbar (5), sacral (5), and coccygeal (1).
Each segment transmits signals to and from specific body parts. These include parts of the arms, chest, abdomen, and legs, as well as pelvic organs and genital areas in their respective zones.

Dermatomes & Myotomes

Dermatomes: Areas of skin innervated by a single spinal nerve, carrying sensory information (pain, temperature, touch) to the spinal cord and then to the brain.
Myotomes: Groups of muscles primarily innervated by a single spinal nerve, enabling voluntary muscle movement.

Deep Tendon Reflexes

Deep tendon reflexes assess spinal cord integrity and differentiate between upper and lower motor neuron lesions.
UMN lesions cause hyperactive reflexes, while LMN lesions lead to decreased reflexes.
Reflexes are tested for asymmetry, stimulus threshold, and hyperactivity/hypoactivity.

Assessments: Sensory Testing

Sensory testing involves evaluating touch, temperature, pain perception, two-point discrimination, and proprioception (body position in space).
Comparisons are made between sides and from proximal to distal extremities

Assessments: MMT

Muscle strength testing (MMT) establishes baselines for treatment, diagnosis, and injury rehabilitation programs.
Tests examine muscle strength in different gravity-related positions.
Muscle strength is graded from 0 (no contraction) to 5 (normal).

UMN vs. LMN Lesions

Upper Motor Neuron (UMN) Lesions: Damage within the central nervous system (CNS) results in increased muscle tone (hypertonia), hyperactive reflexes, spasticity, and possible weakness/paralysis. Common conditions include stroke, traumatic brain injury, multiple sclerosis, and cerebral palsy.
Lower Motor Neuron (LMN) Lesions: Damage within the peripheral nervous system (PNS) causes decreased muscle tone (hypotonia), reduced or absent reflexes, and possible muscle atrophy (wasting) and weakness/paralysis. Common conditions include amyotrophic lateral sclerosis, spinal muscular atrophy, and peripheral nerve injuries.

Neurological Signs & Symptoms

Spasticity vs. Rigidity: Spasticity is velocity-dependent increased muscle tone during stretching, while rigidity is increased muscle tone throughout the range of motion (ROM).
Flaccidity: Reduced or absent muscle tone.

Other Neurological Terms

Dysarthria: Defective speech due to muscular dysfunction.
Dyskinesia: Impaired voluntary movement.
Dysphagia: Difficulty swallowing.
Dysphasia: Impaired speech production or comprehension.
Dyspraxia: Disturbances in the control or execution of voluntary movements.
Dystonia: Prolonged muscle contractions leading to twisting and repetitive movements.
Dysesthesia: Abnormal sensation on the skin.
Ataxia: Defective muscular coordination.
Paresthesia: Numbness, prickling, or tingling sensations.
Dysreflexia: A life-threatening uninhibited sympathetic response in individuals with T6 or higher spinal cord injury.
Aphasia: Inability to speak or comprehend language.
Paralysis: Temporary or permanent loss of motor function and/or sensation.

Developmental Reflexes

Developmental reflexes are involuntary actions that aid in postural control and movement.
These reflexes emerge during fetal development and typically disappear as the nervous system matures.
They are clinically significant as problems in their development or persistence can indicate underlying developmental or neurological disorders.

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Description

This quiz covers essential concepts in neuroscience, focusing on reflexes, lower motor nerve lesions, and cranial nerves. Delve into the anatomy of the nervous system and assess your understanding of how various structures interact in motor pathways. Test your knowledge with questions on proprioception, nerve functions, and damage effects.