PSY2003 W3 Sensorimotor System - (L) Flashcards
What does motor control involve?
A dynamically chaning mix of conscious and uncousious regulation of muscle force by complex and continous sensory feedback
What types of motor control are there?
Voluntary, Goal-directed, habit, involuntary
What are some examples of voluntary motor control?
Running, walking, talkin gplayin gguitar
What are goal-directed motor control?
concious explicit automatic
What are habit based motor control?
unconcisous, implicit automatic
What are some examples of involuntary motor control?
eye movemen, facial expressions, jaw, tongue, postrual muscles, digestive tracts etc.
What does the learned threat affect?
Cortex and limbic system (avoidance)Being able to assess dangerous situations from our knowledge
What does looming threat trigger?
Sensorimotor midbrain (avoidance) coordinated response
What does pain trigger?
Spinal cord (escape)
What governes motor control?
Upper nad lower motor neurons
Where are the lower motor neurons?
begin in the brainstem or spinal cord and prokects to the muscle
Where are the upper motor neurons?
hiher centres and project down to meet the lower motor neurons
How do individual muscle fibers act?
All or Nothing manner
Control of muscle force dependes on the way in which lower motor neurons activate different types of muscle fibres
How much of our body weight is muscle?
around 40%
What are the three types of muscles
Cardiac, smoot and skeletal
Where can the smallest and largest be found?
stapedius (inner ear), gluteus maximus (hip/bottom)
What do muscles do?
Contract and relax only
How do you achieve such a range of movement and forces?
antagonisit carragement combined with co-ordinated action
How do muscle contract?
Interlockig filaments, muscle fibres are pulling towards each other or relax by extending
How is the release of acetylcholine help contract a msucle?
actin and myosin filament The release of acetylcholine leads to release of calcium from inside the muscle cell (fibre). This causes the myosin head to change shape, enabling it to bind with the actin filament. ATP (provides energy for cells) is required to break the bond between the myosin head and the actin filament
What does neurotransmitters have to do with muscle contraction
Neurotransmitter is the one causing the process.
How do enzymes help a muscle to relax
ATP is produced by oxidative metabolism, which stops upon death. So the muscle become contracted and remains that way until enzymes begin to breakdown the actin/myosin.
What is requirment of a muscle for it’s normal functioning
Level of control and strenght
What is the Size principle ?
Units are recruited in order of size, fine control typically require at lower force
What are slow muscle fibres?
sitting, relatively still they don’t get tired
What are fast fatigue resistant muscle fibers?
fast, large amount of force, quite quickly they can maintain for a while but not forever
What are fast fatiguable msucle fibres?
tired quickly but more force
How can training affect muscle fibres?
Training and exercise lead to changes in the thickness of muscle fibres and the proportion of different muscle fibre types
What does fewer fibres mean?
greater movement resolution (finger tips/tongue)
What are motor units
a single alpha motor neuron and all the muscle fibres it innervates
What is the final common pathway for motor control?
motor unit
What happens when alpha motor neuron is activated?
depolarisation and casues contraction of all muscle fibres in that unit
Why are muscel units distributed throughout the muscle
to provide evenly distributed force
What happens when more motor units fire?
more fibres cnotract more power
What is a motor pool?
all the lower motor neurons that innervte single muscle, the pool contrain both alpha and gamme motor neurons, often arranged in a rod like shpae
What are cell bodies in the ventral horn activated by
Sensory information from muscle, descending informaitno from brain
What are refelxes?
Reflexes can be quite simple or quite complex. They can operate without engaging with the brain, and are critical for the avoidance of injury and effective motor control.
What does the control system (CNS) need to know to contract and relax muscles?
how much tension is on the muscle and what is the length of the muscle
How do we sense tension of a muscle
golgi tender organs sense tension
How do we sense the stretch (length) of a muscle?
muscle spindles sense stretch
Where is the Golgi tendon organes (GTO)
within the tenden (where the muscle joins to the bone)
What does the GTO do?
it sends ascending sensory information to the brain via the spinal cord about how much force there is in the muscle
What is the GTO critical for?
proprioception
What can the GTO do when there is extreme tension
GTO act to inhibt muscle fibres to prvent damage
Why are intrafusal fibres innervated seperately to extrafusals
because if the intrafusal msucle fibre is controlled by same motor neurons as extrafusals, when the muscel slacks the system wont be sensitive to slight changes
What neuron innerates intrafusal fibers
gamma motor neurons
What are muscel spindles?
muscle sensory receptros, embedded within most mucles, composed of intrafusal fibers
What does reciprocal innervation of antagonisitc muscles explain?
why the contraction of on emuscel induces the relaxation of the other (Sherrington’s Law of reciprocal innervation)
What system detects if you are upright or not orientation?
vestibular system
What happens to specify a pattern of motor activity that will resotre uprightness and safe landing (e.g. cats)
Information from the vestibular system is combined with visual, somatosensory and proprioceptive sensory input
What is critical for computing the desried motor activity
the cerebellum
What is the primary motor cortex?
exerts quite direct top down control over muscular activity, with as few as one synapise (in spine) beween a cortical neuron and innervatino of muscle cells
Where to motor commads originate from ?
motor cortex pyramidal cells layer 5-6 motor neurons)
Where are cell bodies of the motor cortex located?
gray matter of cortex
Where do pyramidal cell axon project to?
Can project directly or indirectly to spinal cord and onto lower brainstem motor neurons. These axons form the pyramidal tract
What might happen with pyramidal cortical control?
it may operate in co operation with brainstem control
What is a reasonable representatio nbut an oversimplificatin of the omtor cortex?
homunculus
Where do motor commands orginate from ?
motor cortex (M1) pyramidal cells (upper motor neurons)
What is the pyramidal tract?
descdening projections from the spinal cord onto lower motor neurons
What the dorsolateral tract (motor cortex)
both contain a direct corticospinal route, an indirect route via braintem nuclie, view red nuclues. Innervate contralateral side of one segment of spinal cord, sometimes prokect directly to ampha motor neuron, prokect to distal msucle (fingers)
What is the ventromedia tracts ( motor crotex)
both contain a direct corticospinal route, an indirect route via braintem nuclie, via tectum, vestibular nuclei, reticular formation and cranal nerve nuclie. Diffuse innervation prokecting to btoh sides and multiple segments of spinal cord. Porkect to proximal muscles of trunk adn limbs
What is the most basic unit of the motor system
motor unit
What happens without our awarness
great deal of complew motor activity
How are variable muscle force provided?
varaibel muscle force is provided by gradual recruitment of motor unites
Why are robots unable to move as well do ?
No cerebelumm, unable to process and adapt as quickly
What is the brainstem structure?
Pathways and nuclei within the brainstem (and midbrain) connect sensory input to motor output in quite direct ways, providing an evolutionary ancient but still very important control systems
What is the basal ganglia?
a group of nuclei lying deep within cerebral hemispheres, beneath the cortex that acts as a gate keeper for control of the motor systems
Where does the basal ganglia receive information?
receives excitatory input from many areas of cortex (glutamate)
What are basal ganglia outputs?
output goes back to cortex via the thalamus, mainly inhibitory (GABA)
What is the complex internal connectivity involving 5 principle nuclei (basal ganglia)
substantia nigra, candate and putamen, globbus pallidus, subthalamis nucleus
What is the selection proble mwith basal ganglia
multiple command systems, spatially distributed, processing in parallel, al act through final common motor path, cannot do more than one thing at a time
What does the basal ganglia do ?
disinhibtiory gating of motor cortex output
What is the cerebellum ?
a large brain structure that acts as a parallel processor enabling smoot, co ordinted movements, it may also be very important in a range of cogntive tasks
What are the input and outputs of the cerebellum?
Cortical, spinal and vestibular
What are cortical inputs/outputs of the cerebellum?
mostly from motor cortex (copies of motor commands) and somatosensory and visua lareas o parietal cortex
What are spinal inputs/outputs of the cerebellum?
proprioceptive information about lib position and movement (muscle spindles orther mechanorceptors)
What are vestibular outputs/imputs of the cerebellum?
rotational and acceleratory head movement
What is the cerebellar funcitons?
knows what the current motor command is (coritcal input), knows about actual body position and omvement (spinal vestibular input and it projects back to motor cortex
What is in collaboration with basal ganglia and cortical circuits?
motor control and motor learning
What are functional brain imagining studies have demonstrated?
the involvement of the cerebellum in a wide variety of non motor tasks
Where do motor commands originate in ?
in upper motor neurons of primary motor cortex, they descend along corticospinal tracts to lower motor neurons originating n spinal cord
What is the final common pathway of motor control?
the motor unit innervated by a single alpha neuron
What governes precise motor control ?
size principle, different types of muscle fibres and antagonistic arragement of muscle
Motor commands are gated by what?
basal ganglia nuclei, a system of disinhibition
What does the cerebellm provide ?
precise control, ine adjustment and co-ordination of motor activity based on continual sensory feedback
How do lower motor neurons contribute to motor control
reflexes - wants to contract (focus on contraction)
Receptors sense strecht of a muscle and the lower motor neurons will contract to limit dange
How do upper motor neurons contribute to motor control
Motor commands originate in upper motor neurons of primary motor cortex - (enunciate)
Enunciation and Inhibition
Damage to upper neuron
low muscle mass, low power, hype reflexia ( due to lack of inhibition) spastisity (spasmes)
Damge to lower motor neurons
lower musle mass, lower power, hypotonic, hypo reflexia
