Section 3 Flashcards
Sensorimotor System
Conscious action relies on
cognitive processes and constant sensory feedback
What are the different components required for generating complex movements?
Volition
Coordination of many muscle groups
Postural adjustments
Proprioception
Sensory signal processing
Adaptability
Categories of movement
Voluntary (under volition control)
Reflexes (involuntary)
Rhymic motor patterns
Three basic concepts of motor control
- Fine motor control requires proprioception and efference copy - used for adjusting ongoing movements
- Multiple levels of control and parallel circuits
- Motor learning and motor programs - the process that motor programs are create and modified through practice
Which of the following is incorrect?
A. fine control of movement relies on sensory feedback and a copy of the motor command
B. more cortical areas are active when performing learned vs new skills
C. Motor commands descend from the brain to the spinal cord to control motor activity
D. learning shifts the level of brain control.
B
Which of the following is an important phenomenon about motor programs?
A. they are involuntary
B. they do not rely on sensory feedback
C. they are a variable sequence of movements
D. they can be completed with any muscle groups
D
Types of muscles
Skeletal (flexors vs. extenders)
Smooth
Cardiac
What happens at the neuromuscular junction of a motor unit?
Motor neuron fires, acetylcholine is released into the synapse and the muscle fibers within the motor unit contract
Movement precision is based on the ____ ratio
innervation ratio - fine control is associated with less muscle fibers
The regulation of muscle contraction requires
proprioceptors - without proprioception you can do very little with your movements
What happens if someone loses proprioception?
the case of G.O. - no control of distance, direction, or velocity of movements
Two main types of proprioception
Golgi tendon organs - respond to changes in muscle tension
muscle spindles - respond to changes in muscle length
Firing of the Golgi tendon organs leads to
muscle relaxation
Firing of the muscle spindles leads to
muscle contraction
The role of the intrafusal muscle of the muscle spindles is to
maintain muscle spindle sensitivity so that it remains responsive to even slight changes in the length of extrafusal muscle
Stretch reflex occurs when
the length of a muscle is suddenly extended (Detected by stretch receptors aka muscle spindles) leading to contraction
[ example - keeps you from falling when you are pushed ]
The stretch reflex is the [simlest/most complex] spinal circuit
simplest
The withdrawal reflex occurs when
you touch something painful
How is the withdrawal reflex different from the stretch reflex?
the stretch reflex is monosynaptic; the withdrawal reflex is not - it involves interneurons
Two main spinal circuit principles
Recipricol innervation - for coordinating antagonistic muscles
Recurrent collateral inhibition - distribute work between different units of a muscle’s motor pool
Why do we need recurrent collateral inhibition?
if the muscle keeps firing and contracting there would be a build-up of acid and risk for injury, so there needs to be an inhibitor forcing the muscle to relax after enough work is done
Walking and the spinal cord
walking is a complex sensorimotor program in which the CNS generates coordinated patterns of motor outputs
At the bare minimum, walking is a series of
controlled stretch reflexes
What is the organization of the primary motor cortex (M1)?
somatotopically organized (disproportionate representation)
The M1 receives input from
secondary motor areas
prefrontal cortex
primary somatosensory cortex
The effects of damage to the M1 include
mostly contralateral deficits
astereognosis
response weakness
difficulty in moving body parts independently (not long-term paralysis)
The primary motor cortex receives direct inputs from all the following areas except
A. Primary somatosensory cortex
B. SMA and Premotor cortex
C. Secondary motor areas
D. Basal ganglia
D
In what ways is the primary motor cortex M1 similar to the primary somatosensory cortex S1?
A. both are somatotopically organized
B. both located in the frontal lobe
C. both receive direct inputs from neurons in the spinal cord
D. all of the above
A
The two secondary motor areas are
the premotor cortex - movement preparation
the supplementary motor areas - preparation for a rapid sequence of movements
In what ways are the two M2 areas similar
anatomically similar - connected to the M1 and each other and have direct output to the brain stem
functionally similar - electrical stimulation elicits complex movements in body parts and neurons fire prior to and during voluntary movements
Effects of damage to the secondary motor areas (SMA) include
complex movement disorders
difficulty in developing (planning/coordinating) movement strategies
lack of coordination between hands
Sensorimotor Association Areas regulate
higher levels of cognition - controlling, adapting, and being flexible with behavior
Sensorimotor Association Areas include
PFC
Posterior Parietal Cortex
Prefrontal Cortex
highest in sensorimotor hierarchy
mediates planning and decision making
mental representation of motor plan (i.e. working memory)
Damage to the PFC leads to
inability to organize thoughts in order to successfully plan
Posterior Parietal Cortex
mediates multimodal integration
action intention
body and object position references
Damage to the posterior parietal cortex results in
apraxia - inability to do what is asked
contralateral neglect (usually damage to right parietal and affects abilities on left side)
The two Descending motor pathways are
Dorsolateral corticospinal tracts - fingers, wrist, toes
Ventromedial corticospinal tracts - shoulders, trunks, hips, legs
The purpose of the descending motor pathways
the M1 sends signals to motor neurons in the spinal cord through these corticospinal tracts
Motor cortex on one side of the cerebral hemisphere primarily controls the contralateral side of the body via the ________
dorsolateral corticospinal tracts
Some muscle groups get projections from both hemispheres via these _________
ventromedial corticospinal tracts
Two subcortical Motor Areas
The Cerebellum and the Basal Ganglia
Inputs - cortical motor areas, brainstem, sensory
Output - interact with different levels of cortical motor circuit (through thalamus to cortex OR directly to brainstem and spinal cord)
All except the ____ and _____ have some direct connection to the spinal cord
prefrontal; parietal
