Motor Control and Reflexes Quiz

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Questions and Answers

What type of muscle do alpha motor neurons primarily innervate?

Cardiac muscle

Smooth muscle

Adipose tissue

Skeletal muscle (correct)

Where are the cell bodies of motor neurons located?

Thalamus

Cerebral cortex

Dorsal horn of the spinal cord

Ventral horn of the spinal cord (correct)

Which reflex is classified as monosynaptic?

Withdrawal reflex

Stretch reflex (correct)

Inverse stretch reflex

Flexion withdrawal reflex

What function do spinal interneurons serve concerning movements?

Coordinate complex movements and provide proprioceptive feedback Signup and view all the answers

Which statement about spinal reflexes is true?

Spinal reflexes can be overridden. Signup and view all the answers

What does the size of body structures in the primary motor cortex indicate?

The number of neurons dedicated to motor control Signup and view all the answers

Which cortices are involved in the voluntary control of movement?

Premotor cortex and primary motor cortex Signup and view all the answers

What is the primary function of the middle level in motor control?

Correction of errors during movement execution Signup and view all the answers

What describes the somatotopic map of the primary motor cortex?

It reflects the degree of skill required for different body movements Signup and view all the answers

Which component of movement is considered 'involuntary' despite being part of voluntary movements?

Corrections based on real-time feedback Signup and view all the answers

Which pathway is primarily responsible for controlling voluntary, skilled movements?

Corticospinal pathway Signup and view all the answers

What is the primary role of the extrapyramidal pathway?

Regulation of trunk and postural muscles Signup and view all the answers

Which condition is characterized by decreased dopamine input to the basal nuclei?

Parkinson disease Signup and view all the answers

Which of the following is a symptom of spasticity resulting from damage to descending pathways?

Constant muscle contraction Signup and view all the answers

What term describes the resistance of skeletal muscle to stretch under normal conditions?

Muscle tone Signup and view all the answers

What characterizes hyperkinetic disorder?

Excessive motor movements Signup and view all the answers

Which of the following describes bradykinesia?

Slowed movements Signup and view all the answers

Which condition results in jerky, random involuntary movements of limbs and face?

Choreiform movements Signup and view all the answers

Which disease is known for causing widespread neuronal loss in the basal nuclei due to a genetic mutation?

Huntington disease Signup and view all the answers

Which of the following describes dysmetria?

Inability to target movements correctly Signup and view all the answers

What is the role of the cerebellum in motor control?

Receiving sensory information for balance and coordination Signup and view all the answers

Which of the following is NOT a deficit associated with cerebellar damage?

Muscle weakness Signup and view all the answers

What does the magnitude of the withdrawal reflex depend on?

The magnitude of the pain stimulus Signup and view all the answers

Which statement correctly describes the ipsilateral response in the withdrawal reflex?

Flexor muscles contract while extensor muscles relax Signup and view all the answers

What primary function do muscle spindles serve in the body?

Reporting muscle length Signup and view all the answers

What is the role of interneurons in the withdrawal reflex?

They act as connectors between sensory input and motor output Signup and view all the answers

Which characteristic is true for the contralateral response in the withdrawal reflex?

Flexor muscles relax while extensor muscles contract Signup and view all the answers

What type of muscle fibers do Golgi tendon organs communicate with?

Extrafusal muscle fibers Signup and view all the answers

What is the primary role of Ia afferent fibers in muscle spindles?

Detecting changes in muscle length Signup and view all the answers

What does the term 'irradiation' refer to in the context of the withdrawal reflex?

The increase in reflex response with stronger stimuli Signup and view all the answers

Which of the following describes the afterdischarge phenomenon?

The response continues even after the pain stimulus ceases Signup and view all the answers

Which reflex is responsible for protecting limbs from injury?

Withdrawal reflex Signup and view all the answers

What type of reflex is categorized as polysynaptic?

Reflex that requires multiple neurons and synapses Signup and view all the answers

What muscle spindle characteristic contributes to its sensitivity?

Intrafusal fibers Signup and view all the answers

Which of the following best describes the function of the flexor withdrawal reflex?

To initiate a protective response to harmful stimuli Signup and view all the answers

What do Golgi tendon organs primarily report?

Muscle tension Signup and view all the answers

Which part of the brain plays a role in initiating movement based on sensory information?

Cerebral cortex Signup and view all the answers

What is the primary function of gamma motor neurons?

Innervate intrafusal muscle spindle Signup and view all the answers

Which reflex is specifically responsible for controlling muscle tension?

Inverse stretch reflex Signup and view all the answers

In the context of spinal reflexes, which statement is true regarding monosynaptic and polysynaptic reflexes?

Monosynaptic reflexes do not involve interneurons. Signup and view all the answers

Which of the following accurately describes the role of spinal interneurons?

They coordinate complex movements through voluntary feedback. Signup and view all the answers

What defines the withdrawal reflex in terms of its properties?

It is a protective reflex that responds to harmful stimuli. Signup and view all the answers

What is the primary function of the amygdala within the limbic system?

Processing and regulating emotions Signup and view all the answers

Which neurotransmitters are commonly targeted in the treatment of mood disorders?

Serotonin and norepinephrine Signup and view all the answers

What is the role of the hippocampus in learning processes?

Consolidation of short-term memories into long-term memories Signup and view all the answers

What is typically observed in a person with aphasia?

Difficulty in articulating or comprehending language Signup and view all the answers

Which type of muscle action is characterized by the contraction of flexor muscles while extensor muscles relax?

Flexion Signup and view all the answers

Which condition is often characterized by hallucinations and delusions?

Schizophrenia Signup and view all the answers

What does reciprocal innervation of muscles ensure during movement?

Balanced contraction and relaxation of flexor and extensor muscles Signup and view all the answers

Which brain region is primarily responsible for language comprehension?

Wernicke’s area Signup and view all the answers

Which of the following statements accurately describes the contralateral response in the withdrawal reflex?

Extensor muscle contraction takes place. Signup and view all the answers

What is the primary characteristic of the withdrawal reflex regarding its synaptic nature?

It is a polysynaptic reflex. Signup and view all the answers

How does the magnitude of the withdrawal reflex respond to varying intensities of a pain stimulus?

It increases with the strength of the stimulus. Signup and view all the answers

What phenomenon describes the maintained response after the termination of a stimulus in the withdrawal reflex?

Afterdischarge. Signup and view all the answers

What role do interneurons play in the withdrawal reflex?

They connect sensory inputs to motor outputs. Signup and view all the answers

Which statement about irradiation in the context of the withdrawal reflex is true?

It indicates enhanced response rates with increased stimulus intensity. Signup and view all the answers

What follows the activation of sensory neurons in the pathway of the withdrawal reflex?

Integration with motor neuron activation pathways. Signup and view all the answers

What best describes the feedback loops involved in the withdrawal reflex?

They enable sustained reflex action post-stimulus. Signup and view all the answers

What aspect of consciousness is measured by neural activity near the scalp?

State of consciousness level Signup and view all the answers

Which of the following is true regarding EEG measurement?

Frequency relates to levels of responsiveness Signup and view all the answers

What physiological change occurs during REM sleep?

Increased inhibitions of skeletal muscle activity Signup and view all the answers

Which structure in the brain is involved in regulating circadian rhythms?

Preoptic area of the hypothalamus Signup and view all the answers

In motivational psychology, motivation is best described as a drive towards what?

Goal-directed behavior Signup and view all the answers

What primary neurotransmitter is involved in the mesolimbic dopamine pathway?

Dopamine Signup and view all the answers

What neuron activity is associated with increased histamine during sleep?

Aminergic neurons Signup and view all the answers

Continuous activation of reward-related brain areas is linked to which phenomenon?

Self-stimulation experiments Signup and view all the answers

What pattern characterizes low amplitude and high frequency brain activity?

Awake and alert state Signup and view all the answers

Which of the following best describes the emotional experiences associated with consciousness?

They accompany conscious experiences Signup and view all the answers

What is the primary function of muscle spindles?

Detect muscle length. Signup and view all the answers

Which type of muscle fibers do Golgi tendon organs respond to?

Extrafusal fibers. Signup and view all the answers

What response is activated by the Golgi tendon organ when there is increased muscle tension?

Excitation of motor neurons in the ipsilateral flexor. Signup and view all the answers

What type of afferent fibers are responsible for reporting information from the Golgi tendon organ?

Ib afferents. Signup and view all the answers

What is the characteristic of Ia primary afferent fibers related to muscle spindles?

Detect changes in muscle length. Signup and view all the answers

The stretch reflex primarily controls which aspect of muscle function?

Muscle length. Signup and view all the answers

Which of the following best describes the relationship between muscle spindles and extrafusal muscle fibers?

They are located in parallel with one another. Signup and view all the answers

What is the primary purpose of the withdrawal reflex?

To protect limbs from injury Signup and view all the answers

Which statement accurately describes the stretch reflex?

It is responsible for controlling muscle length. Signup and view all the answers

How do gamma motor neurons contribute to muscle spindle sensitivity?

By activating intrafusal fibers to maintain sensitivity Signup and view all the answers

What effect does the activation of the primary afferent fibers have during the stretch reflex?

Excitation of motor neurons innervating the extensor Signup and view all the answers

Which type of reflex is classified as polysynaptic?

Withdrawal reflex Signup and view all the answers

What is the role of intrafusal fibers in the muscle spindle?

To provide sensory information about muscle length Signup and view all the answers

Which type of stretch reflex is primarily responsible for knee jerking?

Monosynaptic stretch reflex Signup and view all the answers

What is the consequence of prolonged muscle shortening on muscle spindle activity?

Decreased spindle responsiveness Signup and view all the answers

What initiates the activation of the muscle spindle during a stretch reflex?

Change in muscle length Signup and view all the answers

The inverse stretch reflex primarily regulates which aspect of muscle function?

Muscle tension Signup and view all the answers

Study Notes

Consciousness

State of consciousness: Level of arousal (awake, asleep, etc.)
Measured by behavior and brain activity
Conscious experience: Thoughts, feelings, desires, ideas, etc.
This is the capacity to experience one's existence, rather than just reacting to stimuli like an automaton.
A laptop, for example, would not be considered conscious.

The Electroencephalograph (EEG)

Measures the activity of neurons near the scalp in the gray matter of the cortex.
Voltage (typically 20-100 microvolts) is measured
Frequency is related to responsiveness levels.
Amplitude is linked to synchronous neural activity.
EEG patterns change during different mental states and sleep stages

EEGs and Mental States

Alpha rhythm: Observed when relaxed with eyes closed, has slow frequencies
Beta rhythm: Seen when alert, has fast frequencies

Stages of Sleep

Awake: Characterized by low amplitude, high frequency waves
NREM (Non-Rapid Eye Movement) sleep: Slow-wave sleep, has progressively higher amplitude and lower frequency waves as sleep deepens, (stages 1-4). Specifically:
- Stage 1: Transition to sleep.
- Stage 2: Light sleep.
- Stage 3: Deeper sleep.
- Stage 4: Deepest sleep. (NREM Stages 3 & 4 are sometimes combined).
REM (Rapid Eye Movement) sleep: Characterized by low amplitude, high frequency waves, associated with dreaming, temporary skeletal muscle inhibition, rapid eye movements

Physiological Changes During Sleep

Reflects changes in brain activity at each sleep stage
During REM sleep, there is an increase in eye movements, and inhibition of skeletal muscle. Also, heart rate and respiration rates increase.
Sleep apnea is a sudden reduction in respiration.

States of Consciousness and Brain Regions

Preoptic area of hypothalamus: Plays a critical role in regulating sleep.
Suprachiasmatic nucleus (SCN) of the hypothalamus: Regulates the circadian rhythm.
Reticular activating System: A critical neural network involved in regulating arousal and consciousness

Regulating States of Consciousness

Aminergic neurons (Norepinephrine, serotonin) and cholinergic neurons (acetylcholine) are active in different states of consciousness.
These neurons are influenced by the presence and level of certain neurochemicals
Chemical factors are involved in the regulations of states of consciousness.
The interplay between these chemicals results in specific states of consciousness.
Histamine and GABA are two specific chemicals involved in regulating consciousness.

Motivation and Emotion

Motivation: Produces goal-directed behavior.
Emotions: Accompany our conscious experiences.

Mesolimbic Dopamine Pathway

A key part of the brain's reward pathway.
Dopamine is the primary neurotransmitter.

Self-Stimulation Experiments

Continuous activation of reward-related areas of the brain.

Limbic System

Involved in emotions
Includes the olfactory bulb, hippocampus (memory) and amygdala

Altered States of Consciousness

Schizophrenia: Diverse set of problems in basic cognitive processing, including delusions and hallucinations; affects about one out of every 100 people.
Mood disorders:
- Depression: Decreased activity in the anterior limbic system. Treatments increase serotonin and norepinephrine levels.
- Bipolar disorder: Swings between mania and depression. Treatments include lithium, which reduces certain synaptic signaling pathways.

Learning and Memory

Declarative memory: Conscious experiences put into words.
- Short-term: Hippocampus and other temporary lobe structures.
- Long-term: Many parts of the association cortex.
Procedural memory: Skilled behavior.
- Short-term: Widely distributed.
- Long-term: Basal nuclei, cerebellum, premotor cortex.
Sleep: Plays a role in consolidating short-term memories into long-term memories
Hippocampus: Important structure in learning and memory

Inside the Brain

H.M.: Amnesic patient who underwent medial temporal lobe removal affecting different brain areas.

Language

Broca's area: Usually in the left hemisphere; articulation.
Wernicke's area: Usually in the left hemisphere; comprehension.
Aphasia: Language deficit

Parietal Damage

Sensory neglect: A condition resulting from parietal lobe damage characterized by a reduction in awareness of one side of the body or one side of space.

When Things Go Wrong

Descriptions of cases of brain damage, or brain diseases. Cases are often cited with the use of specific medical terminology.

Motor Behavior

Purposeful or goal-directed: Voluntary and reflexive.

Muscle Control: Extension vs. Flexion

Extension: Extensor muscle contracts, agonist, increases the angle
Flexion: Flexor muscle contracts, agonist, decreases the angle
Antagonistic muscles have opposing actions during movements

Reciprocal Innervation of Muscles

Coordinated activation and relaxation of flexor and extensor muscles.
Maintaining limb position is a balance of flexor and extensor muscle tension.

Motor Neurons

Only excitatory (acetylcholine).
Alpha: Innervate skeletal (extrafusal) muscle.
Gamma: Innervate muscle spindle (intrafusal) muscle.
Cell bodies located in the ventral horn of the spinal cord (spinal nerves).
Receive input mainly from interneurons.

Spinal Afferent (Sensory) and Efferent (Motor) Pathways

Sensory information travels up the spinal cord in the dorsal columns.
Descending motor commands travel down the spinal cord.
Interneurons also are located in different levels throughout the spinal cord.

Spinal Interneurons

Receive inputs from different receptor types involved with movement and sensory information.
Involved in complex movements
Involved in length monitoring of muscles on both sides of the body
Coordinating complex movements

Spinal Reflexes

Withdrawal reflex: Protects limbs from injury.
Stretch reflex: Controls muscle length (monosynaptic and polysynaptic).
Inverse stretch reflex: Controls muscle tension.
Reflexes can be modified, these reflexes can be overridden

Flexion Withdrawal Reflex

Polysynaptic: Involves multiple interneurons.
Involves inhibition of ipsilateral extensor, and excitation of ipsilateral flexor.
Cross-extensor reflex: Involves inhibition of contralateral flexor, and excitation of contralateral extensor.

Magnitude of Withdrawal Reflex

Depends on the magnitude of the pain stimulus.
Recruitment of interneurons increases in response to greater stimuli
Feedback loops in the spinal cord are involved in the response

Properties of Withdrawal Reflex

Ipsilateral, contralateral, polysynaptic, irradiation, afterdischarge

Monosynaptic Stretch Reflex (Knee Jerk)

Excitation of motor neuron innervating the ipsilateral extensor.
Inhibition of motor neuron innervating the ipsilateral flexor.
Activation and stretch receptor causes the reflex

Muscle Spindle and Golgi Tendon Organ

Muscle spindle: Parallel to muscle fibers, reports muscle length, vital for the stretch reflex and muscle length control
Golgi tendon organ: In series with muscle fibers, reports muscle tension, involved with the inverse stretch reflex and controlling muscle tension

Muscle Spindle Properties

Reports muscle length.
Afferents (la and II): Types of nerve fibers, La (primary) detects changes in muscle length, II (secondary) detects static length.
In parallel with extrafusal muscle fibers.
Intrafusal fibers: Maintain muscle spindle sensitivity.
Alpha-gamma coactivation.

Response of la (primary) and II (secondary) Afferents

la primary: Signals dynamic and some static changes in muscle length.
II secondary: Signals static muscle length.

Muscle Spindles Can Lose Sensitivity

Results with voluntary flexion and extension as muscles lengthen and shorten.
Muscle spindle collapses leading to reduction in sensitivity.

Gamma Motor Neurons Maintain Muscle Spindle Sensitivity

Alpha-gamma coactivation maintains sensitivity.
Intrafusal fibers contract and muscle spindle is stretched.

Alpha-Gamma Coactivation

Motor command, alpha and gamma motor neuron activation.
Extra-fusal muscle activation and shortening is linked to maintaining spindle sensitivity.
Change in length activates the muscle spindle

Properties of Stretch Reflex

Resists changes in muscle length.
Mono- and polysynaptic components.
Feedback from muscle spindles.

Properties of Golgi Tendon Organ

Reports muscle tension.
In series with extrafusal muscle fibers.
Ib afferents.
Underlies inverse stretch reflex.

Motor Control Involves Many Brain Areas

Corticospinal pathway: Skilled movements.
Extrapyramidal pathway: Trunk and posture.
Voluntary movements have an involuntary component.
Multiple brain regions are involved with motor control
Middle level: Executes individualized muscle contractions. Also makes corrections based on sensory information.
Brain stem: Plays a critical role with muscle contraction, and control
Cerebellum: Involved with timing, planning, error correction and learning new motor skills.
Basal Nuclei: Determine the sequence of movements necessary for the execution of an action
Higher Centers: Conscious initiation of movement

Direct Cortical Control of Movement

Corticospinal and extrapyramidal pathways.
Crossing of the pathways in the medulla.
Involvement with alpha and gamma motor neurons.

Descending Motor Pathways

Corticospinal: Originates in the primary motor cortex, compact and direct to spinal cord, controls contralateral muscles, predominately involved with hands and feet, and skilled voluntary movements
Extrapyramidal: Originates from neurons in the brainstem, diffused and indirect via the brainstem, involved in trunk and postural muscles, controls upright posture, balance, and walking

Muscle Tone

Resistance of skeletal muscles to stretch.
Normal: Slight and uniform.
Damage to descending pathways:
- Hypertonia: Abnormally high muscle tone
- Spasticity: Overactive motor reflexes
- Rigidity: Constant muscle contraction.
Damage to motor neurons:
- Hypotonia: Abnormally low muscle tone
- Atrophy: Loss of muscle mass
- Decreased or missing reflexes

Basal Nuclei (Ganglia)

Structure: A group of nuclei located deep within the brain.
Function: Involved in regulating movement, muscle tone, and posture.

Basal Nuclei Movement Disorders

Parkinson's disease: Reduced dopamine input to basal nuclei, resulting in akinesia, bradykinesia, muscular rigidity, and resting tremor.
Huntington's disease: Widespread loss of neurons in the brain, especially in the basal nuclei, resulting in hyperkinetic disorders, like choreiform movements.

Deep Brain Stimulation

A surgical treatment to help control movement disorders like Parkinson's disease through stimulating specific areas of the brain.

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Description

Test your knowledge on the intricate functions of motor neurons, reflexes, and the motor cortex. This quiz covers key concepts related to voluntary and involuntary movements as well as the pathways involved in motor control. Perfect for students studying neuroscience or physiology!