Lecture 4: Neurological System

Question 1

Afferent/Sensory neurons

Answer 1

Carry signals to spinal cord

Sensory info from environment/body to CNS for interpretation

Question 2

Efferent/motor neurons

Answer 2

Carry signals to muscle

Impulses from CNS to PNS to allow for movement/action

Question 3

Interneurons

Answer 3

Interpretive neurons between afferent and efferent nerves in CNS

Question 4

Dorsal horns

Answer 4

Cells transmit sensory info

Question 5

Ventral horns

Answer 5

Contains alpha motor neurons with axons terminating in skeletal muscle

Question 6

Motor units

Answer 6

All-or-none

All fibers in a motor unit are the same type

Question 7

Motor unit types: activation

Answer 7

Type I activated first, then Type IIa, then Type IIB

Question 8

Asynchronous activation

Answer 8

Activation is temporally spaced but summed with preceding motor unit activity

Question 9

Synchronous activation

Answer 9

Large and small motor units activated together

E.g. ballistic movements, adaptation from weight training

Question 10

Frequency coding

Answer 10

Also called rate coding

High frequency can induce high tension production

Question 11

Monosynaptic reflex arc

Answer 11

When sensory neuron is stimulated, it facilitates stimulation of a spinal motor neuron

Question 12

Myotactic reflex

Answer 12

Also called stretch reflex

Causes contraction of a muscle being stretched

Question 13

Flexor reflex

Answer 13

Initiated by painful stimulus

Causes quick withdrawal/flexion of limb

Question 14

Cutaneous reflex

Answer 14

Causes relaxation of muscle with heat or massage

Question 15

Proprioceptive receptors

Answer 15

• Sensory receptors in musculoskeletal system
• transform mechanical distortion in muscles or joints
• carry input to CNS to change joint position, muscle length & tension, stimulate motor response

Question 16

Examples of proprioceptive receptors

Answer 16

Muscle spindle
Golgi tendon organ
Joint receptors

Question 17

Muscle spindle

Answer 17

• Monitors muscle stretch
• Lies parallel to muscle fibers (mostly found in muscle belly)
• Connect into fascicles via connective tissue

Question 18

Intrafusal fibers

Answer 18

Contained within a capsule, forming a muscle spindle

Nuclear bag fibers, nuclear chain fibers

Question 19

Gamma motor neuron

Answer 19

Innervated contractile ends of muscle spindle

Question 20

Gamma bias

Answer 20

Readjustment of muscle spindle length by contracting ends of intrafusal fibers

Question 21

Gamma loop

Answer 21

Reflex arc that works with stretch reflex

Includes afferent, gamma, and alpha pathways

Question 22

Primary afferent

Answer 22

Type Ia, respond to stretch by initiating stretch reflex

Question 23

Secondary afferent

Answer 23

Type II, facilitate flexors and inhibit extensor activity

Question 24

Stretch reflex

Answer 24

Facilitates contraction (via muscle spindle) of a muscle being stretched

Question 25

Autogenic facilitation

Answer 25

Internally generated excitation of alpha motor neurons through stretch or other input

Question 26

Reciprocal inhibition

Answer 26

Relaxation of antagonist while agonists produce joint action

Question 27

Golgi tendon organs

Answer 27

Monitors muscle force/tension Connected directly to extrafusal fibers Inverse stretch reflex (initiated by high tension in muscle, inhibits contraction and causes relaxation)

Question 28

Joint sensory receptors: Ruffini ending

Answer 28

Sensory receptor in capsule that responds to change in joint positioning

Question 29

Joint sensory receptors: pacinian corpuscle

Answer 29

Sensory receptor in skin stimulated by pressure

Question 30

Cutaneous receptors

Answer 30

Found in dermis or epidermis | Sense pressure, vibration, heating, cooling, tissue damage

Question 31

Exteroception

Answer 31

Perception of environment (pressure, skin deformation) Force coordination during precision grip

Question 32

Kinesthesia

Answer 32

Sense of movement/motion Mechanoreceptors

Question 33

Merkel receptors/discs

Answer 33

Slowly adapting receptors Pressure, position, deep static touch (shapes, edges)

Question 34

Meissner corpuscles

Answer 34

Rapidly adapting receptors Light touch sensitivity

Question 35

Ruffini cylinders

Answer 35

Slowly adapting receptors Gross pressure changes and vibrations

Question 36

Electromyography (EMG)

Answer 36

- technique for evaluating and recording electrical activity produced by skeletal muscles - can learn time course of muscle contraction, contraction force, coordination of several muscles in movement sequence, ergonomics

Question 37

EMG instrumentation

Answer 37

Correct placement of electrodes = parallel to muscle fibers Prepare skin by shaving, abrading, cleaning with alcohol

Question 38

Inserted/intra-muscular/needle EMGs

Answer 38

Extremely sensitive, access to deep musculature, little cross-talk BUT: requires cert, cant reposition, painful

Question 39

Surface electrode EMGs

Answer 39

Quick and easy, no medical supervision, minimal discomfort BUT: superficial only, may affect movement patterns, cross-talk concern, limitations in dynamic activity

Question 40

Electrical noise

Answer 40

- Inherent in electronic equipment - frequency range: 0-thousands of Hz - cannot be eliminated - reduced by using high quality components

Question 41

Ambient noise

Answer 41

- electromagnetic radiation sources - impossible to avoid - dominant frequency: 60Hz - 1-3x amplitude of EMG signal

Question 42

Motion artifact

Answer 42

- Two main sources: electrode/skin interface and electrode cable - Frequency range: 0-20 - Reducible by proper circuitry and set up