Neuroscience Quiz: Sensory and Motor Neurons

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Questions and Answers

What are the main structural differences between sensory and motor neurons?

Sensory neurons are pseudounipolar with their cell bodies outside the CNS, while motor neurons are multipolar with their cell bodies in the CNS.

Describe the pathway of sensory and motor neurons in relation to the spinal nerve.

Sensory neurons enter the spinal cord via the dorsal root and exit through the spinal nerve, while motor neurons exit the spinal cord through the ventral root.

How does the composition of gray matter differ from that of white matter in the spinal cord?

Gray matter contains little myelin and consists of cell bodies and dendrites, while white matter is composed of myelinated axons and has a higher lipid content.

What roles do the dorsal and ventral horns play in the spinal cord's structure?

The dorsal horn contains sensory neurons and consists of gray matter, while the ventral horn contains motor neurons and is also composed of gray matter. Signup and view all the answers

Explain the relationship between the spinal cord, spinal nerves, and the meninges.

The spinal cord and spinal nerves are protected by the meninges, which consist of three layers: pia mater, arachnoid mater, and dura mater. Signup and view all the answers

What are the primary actions of the trapezius muscle?

The trapezius muscle elevates and depresses the scapula. Signup and view all the answers

Which nerves innervate the biceps brachii and brachialis muscles?

The biceps brachii and brachialis are innervated by the musculocutaneous nerve. Signup and view all the answers

How does the innervation of the quadriceps femoris group contribute to its function?

The quadriceps femoris group is innervated by the femoral nerve, allowing it to extend the leg at the knee. Signup and view all the answers

What is the primary function of the latissimus dorsi muscle?

The latissimus dorsi extends, adducts, and medially rotates the arm. Signup and view all the answers

Describe the significance of the median nerve in the forearm muscles.

The median nerve innervates the anterior forearm muscles responsible for wrist and finger flexion. Signup and view all the answers

Which muscle group is responsible for the dorsiflexion of the foot?

The anterior leg muscles, including tibialis anterior, are responsible for dorsiflexion. Signup and view all the answers

What is the function of the rotator cuff muscles?

The rotator cuff muscles stabilize the shoulder and facilitate various arm movements. Signup and view all the answers

Explain the role of deep fascia in muscle compartments.

Deep fascia surrounds muscle compartments, providing support and preventing overexpansion. Signup and view all the answers

What actions do the gluteus maximus muscles facilitate?

The gluteus maximus muscles extend and laterally rotate the thigh. Signup and view all the answers

Identify the nerve that innervates the hypothenar muscles of the hand.

The hypothenar muscles are innervated by the ulnar nerve. Signup and view all the answers

What is a muscle twitch and how does it relate to muscle contraction?

A muscle twitch is the response to a single electrical stimulation, causing a brief contraction of the muscle. It relates to muscle contraction as myosin produces tension by pulling on actin, resulting in overlapping filaments and sarcomere shortening. Signup and view all the answers

Why are muscle responses considered graded?

Muscle responses are graded because they can vary in strength and duration depending on factors like stimulation frequency and the number of motor units recruited. Different muscle fibers (fast and slow twitch) also contribute to the variability in force production. Signup and view all the answers

What role does motor unit recruitment play in muscle contraction strength?

Motor unit recruitment increases the strength of muscle contraction by activating more motor units in response to stronger stimuli. This process ensures that as demand for force increases, more fibers contribute to the contraction. Signup and view all the answers

Explain the concept of muscle tone and its physiological significance.

Muscle tone refers to the constant slight contraction of muscles, which aids in posture and balance. It occurs involuntarily and is essential for maintaining readiness for reflexes. Signup and view all the answers

How does frequency of stimulation affect muscle contraction?

Frequency of stimulation affects muscle contraction by determining whether there is relaxation between stimuli; low frequency allows for distinct muscle twitches, while high frequency leads to complete tetanus and maximum tension. Signup and view all the answers

Describe the difference between fast twitch and slow twitch muscle fibers.

Fast twitch fibers are designed for explosive movements and fatigue quickly, while slow twitch fibers are endurance-oriented, supporting prolonged activities without fatiguing easily. This difference influences muscle responses to various tasks. Signup and view all the answers

What happens during complete tetanus and its implications for muscle function?

During complete tetanus, there is no relaxation between stimuli, resulting in sustained maximum muscle tension. This allows for powerful and sustained contractions, crucial for activities demanding high force. Signup and view all the answers

What is the significance of threshold stimulation in muscle contraction?

Threshold stimulation marks the point at which the first observable muscle contraction occurs. Anything below this level results in no contraction, demonstrating the need for sufficient stimulation to initiate muscle activity. Signup and view all the answers

What role do muscle spindle receptors play in maintaining posture?

Muscle spindle receptors detect muscle stretch and initiate muscle contraction to maintain posture. Signup and view all the answers

How does the Golgi tendon organ contribute to muscle function?

The Golgi tendon organ detects tension and force in the muscle, helping to prevent excessive contraction. Signup and view all the answers

Explain the purpose of the crossed-extensor reflex in relation to the withdrawal reflex.

The crossed-extensor reflex helps maintain balance by activating extensors in the opposite limb during withdrawal from a painful stimulus. Signup and view all the answers

What is the significance of paresthesia in the context of peripheral nerve injury?

Paresthesia indicates damage to sensory axons, resulting in abnormal sensations like pain or tingling. Signup and view all the answers

Differentiate between hyporeflexia and areflexia following a peripheral nerve injury.

Hyporeflexia is diminished reflex activity, while areflexia indicates a complete absence of reflexes. Signup and view all the answers

What is the main difference between isometric and isotonic muscle contractions?

Isometric contractions occur without a change in muscle length, while isotonic contractions involve a change in muscle length as force is generated. Signup and view all the answers

Describe the three metabolic pathways for ATP generation in muscles.

The three pathways are: Direct Phosphorylation from creatine phosphate, Anaerobic Respiration (glycolysis), and Aerobic Respiration, with each supporting different durations of energy supply. Signup and view all the answers

What sequence of energy stores is utilized during the early phases of muscle activity?

ATP stored in muscles is used first, followed by regeneration through creatine phosphate, glycogen is then broken down, and finally aerobic respiration takes over for sustained activity. Signup and view all the answers

Compare slow oxidative fibers with fast glycolytic fibers in muscle types.

Slow oxidative fibers (Type I) are characterized by slow contraction and endurance, while fast glycolytic fibers (Type IIb) are designed for swift, brief bursts of power. Signup and view all the answers

What are the primary physiological changes in skeletal muscle due to resistance training?

Resistance training leads to hypertrophy (larger muscle fibers) and hyperplasia (increase in muscle fiber number), along with more mitochondria and glycogen reserves. Signup and view all the answers

How does aging affect skeletal muscle and its recovery?

Aging leads to reduced recovery ability, decreased satellite cells for repair, fibrosis, and a general decline in muscle mass and power. Signup and view all the answers

Explain the concept of disuse atrophy in skeletal muscle.

Disuse atrophy is the reduction in muscle size and strength due to a lack of physical activity, resulting in loss of myofibrils without losing muscle fibers. Signup and view all the answers

Identify other body systems that are influenced by regular exercise.

Regular exercise positively impacts body composition, the cardiovascular system, mental health, and the immune system. Signup and view all the answers

What are the components of a reflex arc?

A reflex arc consists of sensory receptors, sensory neurons, an integration center, motor neurons, and effectors, operating without conscious thought. Signup and view all the answers

Differentiate between concentric and eccentric contractions.

Concentric contractions involve muscle shortening while performing work, whereas eccentric contractions involve muscle lengthening while generating force. Signup and view all the answers

Study Notes

Sensory and Motor neurons

Sensory neurons: Pseudounipolar, cell body outside CNS, collect information from periphery and carry to CNS, afferent, no dendrites
Motor neurons: Multipolar, cell body and dendrites located within CNS, convey information from CNS to periphery, efferent

Spinal Cord Anatomy

Sensory neurons enter spinal cord through dorsal root
Cell bodies of sensory neurons located within dorsal root ganglion
Motor neurons leave spinal cord through ventral root
Spinal nerve forms as dorsal and ventral roots come together, carrying both sensory and motor neurons
Gray matter: Darker areas of brain, little myelin present, doesn't appear white
White matter: White areas of brain, myelin present giving white color, myelinated axons in CNS
Dorsal horn: Contains sensory neurons, dorsal half of spinal cord
Ventral horn: Contains motor neurons, ventral half of spinal cord

Meninges and Vertebral Column

Meninges are layers of membranous tissue protecting brain and spinal cord
Meninges consist of pia, arachnoid mater/subarachnoid space and dura mater
Spinal cord is innervated by sacral nerves

Shoulder Muscles

Pectoral girdle: Consists of clavicle and scapula, traps help elevate or depress scapula, rhomboids retract scapula, serratus anterior helps with protraction and raising arm above head
Humerus movement: Pectoralis major flexes, adducts and medially rotates arm, deltoids abduct, lat dorsi and teres major extend, adduct and medially rotate arm
Rotator Cuff Muscles: Supraspinatus abducts arm, infraspinatus and teres minor laterally rotate arm, subscapularis medially rotates arm

Arm Muscles

Biceps brachii and brachialis: Flexes and supinates forearm at elbow joint
Triceps brachii: Extends forearm at elbow joint, returns it to anatomical position

Forearm and Hand Muscles

Anterior forearm: Flexes wrist and fingers, innervated by median and ulnar nerves
Posterior forearm: Extends wrist and fingers, innervated by radial nerve
Anterior forearm muscles: Flexor carpi ulnaris, palmaris longus and flexor carpi radialis flex wrist
Posterior forearm: Extension of wrist and fingers, radial nerve
Muscles of the hand: Hypothenar moves pinky finger (ulnar nerve), thenar moves thumb (median nerve)

Hip and Thigh Muscles

Anterior Hip: Innervated by femoral nerves, iliopsoas (iliacus and psoas major) flexes thigh at hip joint, rectus femoris extends knee, sartorius flexes hip and knee and laterally rotates thigh
Posterior Hip: Gluteus maximus extends and laterally rotates thigh
Anterior Thigh: Innervated by femoral nerve, quadriceps femoris extend leg at knee, rectus femoris extends leg and flexes hip, vastus lateralis and vastus medialis extend knee
Medial Thigh: Adduction of hip, innervated by obturator nerve
Posterior Thigh: Innervated by tibial nerve, hamstrings flex leg at knee joint, consists of biceps femoris, semitendinosus and semimembranosus
Tensor fascia: Present on lateral thigh, acts with gluteus maximus, locks knee in extension

Leg Muscles

Anterior Leg: Innervated by common fibular nerve, tibialis anterior dorsiflexes foot, extensor digitorum longus extends toes, extensor hallucis longus extends big toe
Lateral leg: Innervated by common fibular nerve, fibularis longus everts foot and plantarflexes
Posterior Leg: Innervated by tibial nerve, gastrocnemius and soleus help plantar flex, these tendons insert onto the calcaneal tendon

Nerve Supply to Limbs

Upper Limb (brachial plexus): Axillary (shoulder), musculocutaneous (biceps brachii and brachialis), radial (posterior forearm), ulnar (ulnar side of anterior forearm and most of hand), median (muscles in thumb and anterior forearm)
Lower Limb (lumbar/sacral plexuses): Femoral (anterior thigh), common fibular (lateral and anterior leg), tibial (posterior thigh), obturator (medial thigh)

Muscle Compartments in Limbs

Deep fascia surrounds muscle compartments
Fascia doesn't stretch leading to compression of nerves and blood vessels
Compression can lead to pain and reduced blood flow

Motor Unit

Motor unit is a single motor neuron and the muscle fibers it controls, all or nothing response
Small motor units (eye muscles) provide more control
Big motor units (lower limbs) provide less precise control

Muscle Twitch and Tension

Myosin produces tension pulling on actin, causing sarcomere to shorten and muscle to contract
Muscle twitch is response to single electrical stimulation

Graded Muscle Responses

Different tasks require different muscle fibers and energy expenditure
Frequency of stimulation: Influences muscle contraction strength, low frequency allows muscle relaxation, high frequency results in tetanus (no muscle relaxation)
Strength of stimulation: Sub-threshold stimuli produces no muscle contraction, threshold stimuli produces first observable contraction, stronger stimulation recruits more motor units, increasing force of contraction

Muscle Tone

Muscle tone is slight contraction of muscles, always present
Muscle tone helps with posture, driven by involuntary muscle movement
Muscle tone decreases with sleep

Isometric and Isotonic Contractions

Isometric: Muscle stays same length while developing tension
Isotonic: Muscle generates force and shortens while lifting a weight
Concentric isotonic: Muscle shortens while doing work
Eccentric isotonic: Muscle generates force while lengthening

Muscle Metabolic Pathways

Direct Phosphorylation of ADP: Creatine phosphate provides phosphate needed to convert ADP to ATP, fastest ATP production, used for quick energy bursts
Anaerobic Respiration (Glycolysis): Glucose from glycogen stores is converted to pyruvic acid, releases 2 ATP, short-term energy supply, lactic acid builds up
Aerobic Respiration: Occurs in mitochondria, requires oxygen, produces 32 ATP per glucose molecule, long-term energy supply

Energy Stores in Muscle Activity

ATP stored in muscles used first
CP regenerates more ATP
Glycogen stored in muscles broken down into glucose for ATP production
Sustained activity relies on aerobic respiration

Muscle Fiber Types

Slow oxidative fibers: Slow contraction, postural muscles, sustained endurance
Fast oxidative fibers: Fast contraction, some aerobic and anaerobic processes, sprinting/walking
Fast glycolytic fibers: Fastest contraction, mostly anaerobic, eye muscles

Effects of Exercise on Skeletal Muscle

Resistance training: Increased muscle fiber size (hypertrophy), more mitochondria, larger glycogen reserves, increased muscle fiber number (hyperplasia)
Endurance training: Increased repetitions with lower weight, increased number of mitochondria, increased oxidative enzymes, more myoglobin

Aging and Skeletal Muscle

Reduced muscle recovery, decreased satellite cells, fibrosis, decreased muscle mass, loss of muscle fibers and diameter
Disuse atrophy: Reduction in muscle size due to lack of physical activity, loss of myofibrils

Exercise and Other Body Systems

Body composition: Prevents obesity
Cardiovascular system: Stronger heart pump, increased blood flow to tissue, decreased blood pressure
Mental health: Enhanced learning and memory, lower risk of depression
Immune system: Lower risk of cancer, increase immune cell activity

Reflex Arc

Reflex arc is involuntary response, has sensory and motor components
Components: Receptor, sensory neuron, integration center, motor neuron, effector

Muscle Spindle and Golgi Tendon Organs

Muscle spindle: Detects muscle stretch, located between muscle cells
Golgi tendon organ: Detects tension, located in tendons

Reflexes

Myotatic reflex (stretch reflex): Muscle stretch activates muscle contraction, helps maintain posture
Withdrawal reflex: Painful receptors activate flexor muscles to retract limb from danger
Crossed-extensor reflex: Helps maintain balance during withdrawal reflex

Peripheral Nerve Injury

Nerve injury can lead to sensory and motor issues, loss of muscle tone, abnormal reflexes
Paresthesia: Abnormal pain, touch, or temperature sensation due to damage to sensory axons
Atrophy: Damage to one motor unit leads to loss of muscle mass
Paresis: Muscle weakness
Paralysis: Complete muscle atrophy
Hyporeflexia: Diminished reflexes
Areflexia: Absence of reflexes

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Description

Test your knowledge on the structure and function of sensory and motor neurons, as well as spinal cord anatomy. This quiz will cover the roles of various neuron types, the arrangement of gray and white matter, and the protective layers of the spinal cord. Perfect for students of neuroscience and biology.