Motor behavior Unit 1

What is motor control?

-study of how the nervous system coordinates muscles and joints to produce purposeful movements

-looks at mechanisms that allow us to plan, initiate, execute, and regulate movement

-happening in the moment

What is motor behavior?

-The study of human movement created by muscular actions, including why and how movements are planned, produced, executed, learned, and refined

What is motor learning?

-Study of how practice and experience lead to relatively permanent changes in ability to preform skilled movements

-Acquisition and retention of motor skills through practice, feedback, and adaption

-Changes overtime with practice 

Both motor control and motor learning involve?

-Nervous system’s role in controlling muscles

-Emphasize perception, cognition, and action 

-Work together to produce skilled movement 

Sensory feedback examples?

-Sight

-Hearing

-Body position sense

-Touch

-Balance and orientation 

What is sensation?

-Physiological detection of physical and physiological signals, like temperature and muscle stretch

-Ex: hearing a sound

What is perception?

-Brain’s interpretation of sensation

-Ex: recognizing the sound as your phone ringing 

What is mind body connection?

-Bidirectional relationship between the mind’s thoughts and emotions 

-The body’s physiological functioning 

What is cognition?

-The process involved in thinking, knowing, remembering, learning, and decision making 

What is psychophysics?

-The sensitivity and relationship between detection and interpretation 

What is skill?

-Quality of movement

What is ability?

-Capacity to preform skilled actions

What is talent?

-Genetic abelites

What is coordination?

-Specific patterning of body and limbs to the environment

What is psychomotor skill?

-Characteristics like precision, manual control, cognitive processing / decision making, and reaction time 

Imagine a motor action and explain it in the context of being a motor skill?

-Throwing a baseball

• Throwing a baseball involves controlling your arm, wrist, fingers, torso, and legs in a coordinated sequence 

• Emphasis on the movement- accuracy, speed, and efficiency of the throw

Imagine a motor action and explain it in the context of being a psychomotor skill?

-Throwing a baseball

• Throwing a baseball as a pitcher in a game requires judgment (which pitch to throw), timing (when to release the ball), and perception (adjusting based on the batter stance

• Emphasis on the integration of mind and body- cognition (thinking and strategizing) and motor control (movement)

Types of Sensory receptors?

-Mechanoreceptors

-Thermoreceptors

-Nociceptors

-Photoreceptors

-Chemoreceptors

-Proprioceptors

What are Mechanoreceptors and where are they located?

-detect mechanical forces: touch, pressure, vibration, stretch

-Location: Skin, muscles, tendons, inner ear, blood vessels.

What are Thermoreceptors, and where are they located?

-detect temperature changes

-Location: Skin (dermis and epidermis), hypothalamus.

What are Nociceptors, and where are they located?

-pain receptors; detect harmful stimuli

-Location: Skin, muscles, joints, bones, most internal organs.

What are Photoreceptors, and where are they located?

-Detect light

-Location: Retina of the eye.

What are Chemoreceptors, and where are they located?

-detect chemical stimuli

-Location: Taste buds (tongue), Olfactory epithelium (nose), Carotid bodies & aortic bodies

What are Proprioceptors, and where are they located?

-Sense body position and movement

-Location: Muscles, tendons, joints, inner ear.

Describe a scenario that creates high sensory receptor acuity

-Reading Braille with your fingertips.

• The fingertips have many densely packed mechanoreceptors.

• Each receptor has a small receptive field, meaning it only responds to a tiny area of skin.

• When touching raised Braille dots, your brain can distinguish the location of each bump with high precision

Describe a scenario that creates low sensory receptor acuity

-Feeling a fly land on your back

• The skin on your back has fewer receptors spread out over a large area.

• Each receptor has a large receptive field, meaning it covers a bigger portion of skin

• Because of this, you might feel “something” touched your back but can’t pinpoint the exact location.

What is proprioception?

-The body’s ability to sense its position in spaces

-Tells you where your body parts are relative to each other and to the environment, even without looking.

-Receptors involved: Muscle spindles, Golgi tendon organs, joint receptors, vestibular apparatus (inner ear).

What is Kinesthesia?

-The body’s ability to sense the movement of muscles and joints from somatosensory sources

-Tells you how your limbs are moving, including direction, speed, and range of motion.

-Receptors involved: Same as proprioception, but with greater emphasis on muscle spindles and joint movement feedback.

Muscle Spindle is concerned with _____ while the GTO is concerned with ______?

- Muscle length and the rate of change in length (stretch).

-muscle tension/force of contraction.

What is the golgi tendon organ?

-A type of mechanoreceptor that responds primarily to muscle tendons

What are Intrafusal fibers?

-Specialized muscle fibers found inside the muscle spindle.

-Serve as sensory receptors that detect changes in muscle length and the rate of stretch. They do not generate significant force.

-Innervation:

• Sensory afferents (detect stretch)

• Gamma motor neurons (adjust spindle sensitivity)

What are Extrafusal fibers?

-The regular skeletal muscle fibers that make up most of the muscle.

-Responsible for generating force and movement.

-Innervation: Activated by alpha motor neurons.

Sensory afferents leaving the Muscle Spindle?

-Primary Afferents (Group Ia fibers)

-Secondary Afferents (Group II fibers)

What are Primary Afferents (Group Ia fibers)?

-Innervate: Wrap around the central region of both nuclear bag and nuclear chain intrafusal fibers.

-Function:

• Detect muscle length.

• Detect rate of change in length (velocity of stretch).

-Key Role: Super fast response → important in the stretch reflex (like the knee-jerk test).

What are Secondary Afferents (Group II fibers)?

-Innervate: Primarily the nuclear chain fibers (toward their ends).

-Function:

• Detect static muscle length (how stretched the muscle is at a given moment).

• Less sensitive to velocity.

What process allows the muscle spindle to continue to be effective in detecting and sending sensory information even when the muscle shortens during contraction?

-Alpha-Gamma Coactivation

What is the Alpha-Gamma Coactivation process?

-When a muscle contracts, the extrafusal fibers (force-producing fibers) shorten.

-If the intrafusal fibers inside the muscle spindle weren’t adjusted, they’d go slack and stop detecting stretch.

-To prevent this, gamma motor neurons stimulate the intrafusal fibers to contract at the same time as the extrafusal fibers.

-This keeps the muscle spindle taut and sensitive, so it can continue to detect changes in muscle length even during contraction.

What is AMI?

-Arthrogenic Muscle Inhibition

-Reflex inhibition of muscles surrounding a joint after injury (like swelling, pain, or inflammation).

-Mechanism:

• Joint receptors and afferents from swelling/pain send inhibitory signals to the spinal cord.

• This decreases excitability of alpha motor neurons to the affected muscle.

-Effect: The muscle (often the quadriceps after knee injury) can’t fully activate, even if you try voluntarily.

What is extensor thrust?

-Reflex extension of the limb when pressure is applied to the sole of the foot.

-Mechanism:

• Pressure stimulates cutaneous receptors

• Excites extensor motor neurons → causes the limb to straighten/extend.

What is a withdrawal reflex (flexor reflex)?

-Automatic flexion of a limb to pull away from a painful stimulus

-Mechanism:

• Nociceptors (pain receptors) are activated.

• Afferent fibers stimulate interneurons in the spinal cord.

• Excite flexor motor neurons → limb rapidly withdraws.

What is a crossed extensor reflex?

-Reflex that complements the withdrawal reflex to maintain balance.

-Mechanism:

• While one limb withdraws (flexes), the opposite limb reflexively extends to support body weight.

• Involves interneurons that cross the spinal cord midline

What does the Vestibular system do?

-body’s balance and spatial orientation system.

-tells your brain about head position, movement, and equilibrium, so you can stay upright, coordinate movement, and keep your vision stable.

-Gives you a sense of where you are in space (e.g., tilting, turning, or moving forward).

-Works with proprioception and vision to ensure smooth, coordinated body movements.

-Keeps your eyes focused on an object even when your head moves.

What is Righting?

-Righting is the set of reflexes that restore the normal alignment of the head, trunk, and limbs in relation to gravity and the environment.

-It’s primarily controlled by the vestibular system, visual input, and proprioception.

What are the structures of the eye?

-Cornea → clear front layer; bends (refracts) light most strongly.

-Aqueous Humor → fluid-filled space between cornea & lens.

-Lens → changes shape (accommodation) to fine-tune focus.

-Vitreous Humor → gel filling the eyeball, maintaining shape.

Anatomy of the Retina (sensory layer)

-Rods → dim-light (night) vision, black & white.

-Cones → color vision (red, green, blue sensitive), sharp detail.

-Macula lutea → central region with high cone density.

-Fovea centralis → sharpest vision, only cones.

-Optic disc (blind spot) → where optic nerve exits; no photoreceptors.

Parts of the central processing in the brain?

-Lateral Geniculate Nucleus (LGN) of the thalamus → relay station.

-Primary Visual Cortex (V1, occipital lobe) → first cortical processing of vision.

-Higher Visual Areas →

• Dorsal stream ("where pathway") → motion, spatial awareness.

• Ventral stream ("what pathway") → object recognition, color, detail.

What is the flow of vision?

-Light → Cornea → Pupil → Lens → Retina (rods/cones) → Optic Nerve → Optic Chiasm → Optic Tract → LGN (thalamus) → Visual Cortex → Higher Processing

What is Focal vision?

-Vision that uses the fovea (center of the retina) for sharp detail.

-requires head movement to center gaze and maintain sharpness

-conscious processing

-Identifies objects and details

What is Ambient vision?

-Uses both foveal detection and peripheral detection

-widespread subconscious processing

-Both dorsal and ventral streams

-detection of motion and relationships among objects

What is the Dorsal stream?

-Where/ how pathway

-Function:

• Processes spatial location, movement, and motion.

• Guides action and movement based on where objects are.

What is the ventral stream?

-What pathway

-Function:

• Processes object identity, color, shape, and detail.

• Recognizes faces, objects, and symbols.

What is Optic flow?

-Eye movement and movements of objects in the environment cause changing patterns of light to strike the retina

-Function: Provides critical information about speed, direction, and distance during movement.

What is Tau?

-A variable that represents time-to-contact with an object based on visual information.

How does optic flow effect tau?

-As an object approaches, its image on the retina expands.

-The brain calculates tau from the rate of expansion in the optic flow, helping predict when the object will reach you.

-Example: Catching a ball – your brain estimates when it will reach your hand using optic flow and tau

How does optic flow effect motion perception?

-Optic flow provides continuous visual feedback about:

• Self-motion → how you’re moving through space.

• Object motion → how other objects move relative to you.

-Example: Driving on a road – the visual flow of the surroundings tells you speed and direction.

What is anticipation timing?

-The ability to coordinate a motor action to intercept or respond to a moving object.

How does optic flow effect anticipation timing?

-Helps the brain predict future positions of moving objects.

-Works with tau to time movements accurately.

-Example: Hitting a tennis ball – your brain uses the expansion of the ball’s image (optic flow) and tau to time your swing.

What is a motor unit?

-Single motor neuron (alpha MN) and all the muscle fibers it innervates

-Contain the same type of muscle fibers (slow + fast)

What is an innervation ratio?

-The number of muscle fibers per single MN (15-2,000)

What are the physiological features of a small motor unit?

-Few muscle fibers

-Slow-twitch (type 1)

-Small cell bodies, thin axons

-Low threshold (easily activated)

-Generate low force

-High fatigue resistance (can sustain long contraction)

-Fine, precise movements (eye muscle/ hand muscle)

What are the physiological features of a large motor unit?

-Many muscle fibers

-Fast twitch (type 2)

-large cell bodies, thick axons

-High threshold (need strong stimuli)

-Generate high force

-Low fatigue resistance (fatigue quickly)

-Gross powerful movements (quads/ calf muscles)

What is the size principle?

-MU’s fire in order from small to large and are de-recruited in opposite order

-Small MU have a low activation threshold, so they fire first

-As demand for force increases, large motor units are recruited

The size principle ensures?

-Energy efficiency

-Smooth, controlled increases in force

-Protects muscles from fatigue

How does the size principle apply to decruitment?

-On the way down

-When the required force decreases, large motor units drop out first

-Small motor units remain active until the force demand is minimal

-Recruitment= small—> large

-Decruitment= large—> small

What is the all or none principle?

-Within a MU all the muscle fibers fire or none fire

-Either contracts completely or not at all

What are the 3 ways in which the nervous system regulates force output?

-Motor unit recruitment

-Rate coding of motor units

-Coordination of motor units and muscles

What is motor unit recruitment?

-Increasing the number of active units

-Follows size principle: small—> large

What is rate coding of motor units?

-Changing the firing frequency of motor neurons

-low frequency—> single twitches

-Moderate frequency—> summation (twitches add together)

-High frequency—> tetanus (smooth, sustained contraction)

What is coordination of MU?

-How well units are activated together + across muscles

-Includes

• synchronization of firing within a muscle

• Intermuscular coordination (different muscles working together)

-Imporoves with traning + skill practice

Firing rates for motor units range from?

-5 to 120 Hz

Define and describe the 2 types of neuromuscular coordination?

-Intramuscular

-Intermuscular

What is intramuscular coordination?

-The patterning and use of motor units within a muscle of across muscle task groups

What is intermuscular coordination?

-Coordination of muscle groups and body segments

What is discharge patterning?

-Manipulation of the firing rates to meet specific task and demands

What is tonic firing?

-Continuous, steady firing for sustained, low-force contractions

What is phasic firing?

-Bursts of high-frequency firing for rapid, powerful movements

What are doublets and triplets?

-Two or three very rapid impulses in succession to maximize force briefly

What is muscle wisdom?

-Slowing discharge rate of MU during fatiguing conditions to maintain force output

What is synchronization?

-Firing rates across MU’s to maximize force output for short bursts

-        What is compartmentalization?

-Smaller and independently controlled groups of muscle groups of muscle fibers contained within a single muscle or across a group of muscles activated for a purpose of coordination

What are the important mechanical properties of the muscle-tendon complex?

-Force-length relationship

-Force-velocity relationship

-Stretch shortening cycle

-Compliance

-Viscosity/ Damping

What is a force length relationship?

-Muscle force depends on the overlap between actin and myosin filaments

-Optimal length= maximal cross-bridge formation —> highest force

-Too short or too stretched= reduced force

What is force velocity relationship?

-Muscle force depends on contraction speed.

-Concentric (shortening): Higher velocity → lower force.

-Eccentric (lengthening): Higher velocity → greater force (muscle resists lengthening strongly)

-Isometric Contraction (no movement): Velocity = 0, muscle can generate a relatively high force

What is stretch shortening cycle?

-Muscles and tendons store elastic energy during a stretch (eccentric phase).

-This stored energy is released in the shortening (concentric phase) → increases power output.

What is compliance (Stiffness vs Elasticity)?

-The tendon can stretch and recoil, acting like a spring.

-Stiffer tendon: Better force transmission, less energy storage.

-More compliant tendon: More energy storage, better shock absorption.

What is viscosity/ damping?

-Muscle tissue resists changes in length depending on the speed of stretch.

-Provides stability and protection from injury during rapid movements.

What does SE stand for?

-SE=Series Elastic Component

• Elastic structures in line with the contractile element.

• Mostly the tendons and cross-bridge elasticity.

• Stores and releases elastic energy during muscle action.

What does CE stand for?

-CE = Contractile Element

• The active, force-generating part of the muscle.

• Made up of actin–myosin cross-bridges that produce tension when ATP is used.

What does PE stand for?

-PE = Parallel Elastic Component

• Passive elastic structures that run alongside the contractile element.

• Includes connective tissue (epimysium, perimysium, endomysium).

• Provides resistance when the muscle is stretched.

What is the length-tension relationship?

-How the force a muscle can generate depends on its length at the time of contraction.

-Too Short (Over-contracted): force production decreases

-Optimal length (resting length): maximum active length

-Too long (overstretched): force production decreases

Describe the organization of the Nervous System and its classification systems

• Two division

-central (CNS)

-peripheral (PNS)

The PNS is divided into?

-Sensory (afferent)

-Motor (efferent)

Sensory controls?

-Visceral sensory endings

-Somatic sensory endings

Motor is split into?

-Somatic

-Automatic

Somatic controls?

-Skeletal muscle

Automatic is split into?

-Sympathetic

-Parasympathetic

Sympathetic and Parasympathetic controls?

-Smooth muscles

-Visceral glands

What is a neuron?

-Specialized cell that receives, processes, and transmits, information through electrical and chemical signals.

What is a soma?

-Main part of the neuron that contains the nucleolus and organelles

-Maintains health of the neuron

-Integrates incoming signals from dendrites

What are dendrites?

-Extensions for the soma

-Receive incoming signals (neurotransmitters) from other neurons and carry them toward the soma