Chapter 13: Control of Body Movement単語カード | Quizlet

Voluntary Movements

Conscious awareness of movement

- Physical awareness

- Purposeful movement

Involuntary movements

No conscious awareness

- unconscious

- automatic

Combination of voluntary and involuntary

- learned actions that become automatic

- reflexes that can be consciously blocked or augmented

- muscle memory

Neural Reflexes: Afferent information

INPUT:

Sensory input

- collect info for a desired movement

- proprioception

INTEGRATION

Processing

- assess input or develop a specific intended movement

- determine necessary action

- motor program

*formulate the neural activity required for the action

Neural Reflexes: Efferent Information

OUTPUT:

Descending pathways

- motor output

- send appropriate signals to appropriate areas

ACTION:

Desired action

- motor neuron pool and associated muscle activation

*motor units

1. Type of efferent control

(autonomic vs. somatic)

2. Location of integration

(spinal vs. cranial)

3. Development of reflex

(innate vs. learned or conditioned)

4. # of neurons in the pathway

(monosynaptic vs. polysynaptic)

How can neural/motor reflexes be categorized?

autonomic controlled reflexes

Visceral reflexes

- occur in organs

- most are unconscious, some are conscious (ex. urination)

- most have tonic activity

Location of integration

- Spinal (can also be influenced by brain)

- Cranial (can modify relfex)

Polysynaptic

monosynaptic

-single synapse between sensory neuron that received and motor neuron responds

-e.g. knee jerk

polysynaptic

-at least 1 interneuron between sensory and motor neuron

-e.g. withdrawl reflex

somatic controlled reflexes

Skeletal muscles - voluntary (doesn't rely solely on sensory coming in)

Location of Integration:

- Cranial

(integration or inhibition - primary motor cortex with influence of other areas)

- Spinal

"reflex action"

(May be influenced by the brain)

- moderate a reflex action

- block a reflex action

Monosynaptic or Polysynaptic

Stimulation vs. Inhibition

- activity at the neuromuscular junction is ALWAYS excitatory

- stimulate myofiber: get a twitch

- stop stimulating myofiber: relax myofiber

- inhibition must occur at the somatic motor neuron

- block development of AP in somatic motor neuron

Muscle receptors

Golgi tendon organs

Joint receptors

What are the three types of proprioceptors (sensory receptors) that are found in skeletal muscle reflex control?

upper motor neurons

motor neurons in the CNS (brain and spinal cord) that control the lower motor neurons in the peripheral nervous system

lower motor neurons

somatic motor neurons that are in the PNS

categorized into:

Alpha motor neurons

Gamma motor neurons

alpha motor neurons

type of lower motor neuron

innervates extrafusal fibers

generates tension/force

gamma motor neurons

type of lower motor neuron

innervates intrafusal fibers

detects muscle stretch

Extrafusal fibers

contractile myofibers

innervated by alpha motor neuron

- flaccid paralysis

- polio

covered by muscle spindles

function: to develop force/contraction

muscle spindles

buried among the extrafusal fibers of the muscles

1. connective tissue capsule

2. intrafusal fibers

- contractile myofiber ends (gamma motor neurons)

3. non-contractile center

- sensory stretch receptors

Intrafusal fibers

contractile myofiber ends

innervated by gamma motor neurons

function: to maintain shape of receptive area in the center

tonic activity at rest

Muscle spindles have what kind of activity? Meaning they are firing even when relaxed.

monosynaptic spinal reflex

Are muscle stretch (muscle-spindle reflexes) a monosynaptic or polysynaptic spinal stretch relfex?

When muscles stretch and strengthen, muscle spindle sensory afferent neurons fire more.

The reflex response is muscle contraction to prevent damage from over-stretching.

Why does a muscle stretch trigger a stretch reflex?

Negative feedback control:

1. stretch signal

(activates alpha motor neuron)

2. Contract extrafusal fibers

(compress receptive area)

3. No more stretch

(return to tonic signal rate)

- turn system off

in more detail:

1. muscle stretch

-> increased afferent signals to spinal cord

-> spinal cord

-> increased efferent signals through alpha motor neurons

2. muscle contracts

How does a muscle stretch trigger a stretch reflex?

***Without gamma motor neurons, muscle contraction causes the spindle firing rate to decrease.

Alpha motor neuron stimulation w/o stretch receptor activation causes a problem:

- it compresses the stretch receptor area and you lose the ability to detect stretch. (you end up dropping the weight)

Why does the shortening of extrafusal fibers in a muscle stretch become a problem?

(in terms of not having the gamma motor neurons (intrafusal fibers))

alpha-gamma coactivation

Alpha and Gamma motor neurons both activated

- contraction of extrafusal fibers is to develop force

Direction of pull: towards center

- contraction of intrafusal fibers is to maintain shape of receptive area

Direction of pull: each end of the muscle spindle (the intrafusal fibers are also pulling towards its center.

* works together to keep muscle contracting

Golgi tendon organs

receptors sensitive to tension in tendons

free nerve endings in tendons

***Isometric phase of voluntary muscle contraction

- stretch elastic components of muscle

- increase tension on tendons

- increase firing of golgi tendon receptors to keep muscles from shortening - keep same length. STILL AT REST

alpha-gamma coactivation:

- maintain appropriate tension

golgi tendon organ:

- increase sensory information to CNS allowing for

*better motor control: posture and movement

Muscle spindles and Golgi tendon organs: why have both?

joint reflexes

Myotatic units

All pathways involved in control of a joint movement:

- reflex components

- agonist & synergists & antagonists

Integration of multiple individual reflexes into a functional response

- desired reflex

- reciprocal inhibition

Monosynaptic vs. poly- or multisynaptic

Ipsilateral vs. contralateral

Patellar tendon or knee jerk (stretch reflex)

Stimulus: tap to tendon - detects stretch in muscle

Receptor: muscle spindle stretch receptors

Desired Action:

- # synapses: monosynaptic

- Ipsi-contra?: ipsilateral

- Effect on alpha motor neuron: excitation, causes it to contract and swing forward

Reciprocal inhibition: antagonist flexor must relax

- # synapses: poly (2)

- Ipsi-contra?:

ipsilateral

- effect on alpha motor neuron: relax hamstring

agonist pathway (monosynaptic)

antagonist pathway

(polysynaptic)

works together because you have anterior muscles that contract and posterior muscles that need to relax in order to kick

In a patellar tendon or knee jerk reflex (stretch reflex)

there are two efferent pathways why?

withdrawal or flexion reflex

Stimulus: pain (stepping on something sharp)

Receptor: nociceptors

Desired Action: pull foot away (flex)

- # synapses: multisynaptic

- Ipsi-contra?: ipsilateral

- effect on alpha motor neuron: excite (stimulate)

Reciprocal inhibition:

- # synapses: multisynaptic

- Ipsi-contra?: ipsilateral

- effect on alpha motor neuron: relax

Crossed extensor reflex

Stimulus: pain (stepping on something sharp)

Receptor: nociceptors

Desired Action:

- # synapses: multisynaptic

- Ipsi-contra?: contralateral

- effect on alpha motor neuron: excite (stimulate)

Reciprocal inhibition:

- # synapses:

multisynaptic

- Ipsi-contra: contralateral

- effect on alpha motor neuron: relax

1. spinal cord

(spinal cord reflexes & some central pattern generators)

2. cerebellum & brainstem

(postural reflexes & hand and eye movement)

3. Cerebral cortex & basal ganglia

(true voluntary movements)

Where are the places CNS integration can occur?

CNS Control of Movement:

Reflex Movements

Simple movements & postural reflexes

Most are spinal or brainstem reflexes:

1. no input from cerebral cortex is needed

2. info also goes to other parts of the brain to be assessed

- response can be modulated:

enhanced or inhibited

Sensory info:

- proprioceptors, golgi tendon organs, muscle stretch receptors

- may also be used for following voluntary or postural reflexes

postural reflexes

maintenance of body position

most are integrated in the brainstem

sensory info: proprioceptors, vestibular apparatus, vision, tactile receptors

CNS Control of Movement:

Voluntary Movements

Desired movement

- often learned movement

May become involuntary

- automatic movements

- muscle memory

Integrated in the cerebral cortex

- but coordinated with input from other parts of the brain

- basal ganglia

- cerebellum

Sensory info:

- may be developed without external sensory input

- proprioceptors, vestibular apparatus, vision, tactile receptors

Rhythmic movements

- initiated by cerebral cortex

- maintained by central pattern generators: CPGs

- interneuron networks in brain and spinal cord

- some rhythmic movements maintained by spinal cord only

- variation of the pattern requires new cerebral cortex input

voluntary

but they can become involuntary

Are rhythmic movements voluntary or involuntary?

feedforward reflexes

preps body for movement

sensory feedback

allows continuous, smooth movement

coordination of movement

integration of multiple parts of the brain

1. Planning

2. Initiating

3. Executing

What are the 3 components of voluntary movements?

Planning the movement

"Higher Centers": integration from multiple areas

- Sensory cortex: current position info

- Prefrontal cortex & motor association areas: determines appropriate movement and the results

- Basal ganglia & thalamus: refinement of movement

Initiating the movement

Motor cortex to brain stem: starting action of specific motor units

- cortex area & # motor units

- Basal ganglia & cerebellum: modication of the movement

- humunculus

Executing the movement

local level of control: CNS to PNS

- brain stem to spinal cord:

direct motor cortex influence

- Basal ganglia & cerebellum: modifcation of movement

- Spinal cord to motor unit

- Continuous sensory feedback

Corticospinal pathway (cortex to spine)

(pyramidal or direct tracts)

- lateral, anterioral, corticobulbar tracts

- start at cerebral cortex and then work your way down: Descending pathway

What is the Voluntary Movement Pathway?

What are the different tracts?

Where does it start?

Lateral corticospinal tracts

(think Lateral = meduLLa = Low part of Limbs -> L!!!!!)

80-90% of pyramidal fibers

decussation in medulla

distal limbs, hands, feet

Anterior corticospinal tracts

(think Anterior = Axial)

10-20% of pyramidal fibers

decussation at level of synapse in spinal cord

axial trunk skeleton muscles

- hoola hooping

- also some proximal parts of limbs

Corticobulbar tracts

motor cortex to brainstem and cranial nerves

cortex -> bulb

decussation is variable

skeletal muscles in the head

- eyes, tongue, chewing, face, speech, neck

Brainstem pathway

May be a component of the extrapyramidal tracts

muscles of the trunk

- balance, posture, walking

most do NOT decussate

- which side of the brain controls movement in your right in external oblique muscle? idk...if they don't decussate, then it must be the right side??

involuntary - bc it begins in the brainstem

Pathway overlap and complement

corticospinal and brainstem pathways overlap in function

- corticospinal: most fine or detailed movement; most voluntary movement

- brainstem: most gross movements of balance, posture, and orienting the body relative to a stimulus; most involuntary movements of tonus, posture and balance

spastic paralysis

upper motor neurons are affected

reflexes still occur

flaccid paralysis

alpha lower motor neurons affected

muscles go limp and atrophy

hypertonia

increased muscle tone causes rigidity, spasms, cramps, spasticity after stretching

increase alpha motor neuron activity

decreased descending pathway inhibition

- C. tetani: block NT release to inhibitory interneurons

hypotonia

decreased muscle tone causes flaccid muscles

decrease alpha motor neuron activity

neuromuscular junction disorders

disorders of the muscle itself

Parkinson's

Symptoms:

- akinesis and bradykinesis in voluntary movements

- shuffling and unsteady gate

- lack of blinking

- tremors at rest

Malfunction of basal nuclei(ganglia) and activation of motor cortex

- degeneration of substantia nigra

--- decreased dopamine release to basal ganglia

--- decreased excitatory input to motor cortex

imbalance between excitatory and inhibitory input to basal nuclei and cortex

Treatments:

- L-dopa: dopamine receptor agonists, MAO and other dopamine enzyme inhibitor, electrical stimulation of underactive area, destruction of overactive areas

- undifferentiated embryonic stem cells

Cerebellar disease (intension tremor)

Symptoms: gate ataxia, tremors when moving, lack of coordination of movements, difficulty learning new movements and modification of movements

cerebellar damage: trauma and chemicals