L9 make things happen Flashcards
What do efferent nerves do?
Carry impulses away from the central nervous system
Where do efferent nerves end?
Either on muscles or on glands
What are the 3 types of muscles?
Smooth
Cardiac
Skeletal
Skeletal muscles are under what’s direct control?
CNS
How many skeletal muscles are there in a human body?
Around 640
Where does muscle sit in a complex motor system?
At the end
What kind of connections do skeletal muscles have with the motor system?
Feed-forward and feed-back connections
What are skeletal muscles made of?
Muscle fibres
Each muscle fibre receives input from how many spinal motor neurons?
One
Where do spinal motor neuron cell bodies live?
In the ventral horn of the spinal cord
How many fibres do one spinal neuron contact?
Several
What is a motor unit?
All muscle fibres supplied by one motor neuron
When will fibres perform a short contraction?
Each time the motor neuron fires an action potential
Why skeletal muscles are called striate?
It contains alternating stripes of actin and myosin filaments
Consequence of nerve fibre activation.
Firing action potentials along the muscle fibre membrane and trigger Ca++ release
What does firing action potentials allow?
Allows myosin proteins to latch on to actin fibres, leading to contraction
What will happen if there is no further inputs from nerve fibre activation?
Ca++ is reabsorbed, myosin let go of the actin and the muscle relaxes
What does myofibrils made of?
Protein filaments
What does sarcoplasmic reticulum contain?
Ca++ ions and voltage gated Ca++ channels
When the muscle is at rest, what happens to the myosin binding site?
It will be covered up by tropomyosin (protein)
What happens when actin and myosin are not attached when the muscle is at rest?
Actin and myosin will slide past each other and the muscle will become longer
What makes tropomyosin leave?
Ca++
When myosin head bends backwards, what does it release and what does it do?
ADP and myosin head pulls itself forward
What causes a release from actin?
ATP binding to myosin
Before myosin ready to undergo new binding cycle and pulling cycle, what does it do?
Myosin uses energy from ATP hydrolysis to stretch itself
What do skeletal muscles contain?
Muscle fibres and spindles which incorporate stretch receptors
How does stretch receptors send signals back to the spinal cord?
Through fast conducting A-beta fibres
Gamma motor neurons control what kind of contractions?
Muscle spindle contractions
What does alpha motor neurons control?
Ordinary muscle fibres
How can muscle spindle afferents form monosynaptic reflex arcs in the spinal cord?
Muscle spindle afferents connect straight to alpha motor neurons
What are muscle spindles?
Receptors for muscle stretch in the two-neuron stretch reflex (stretch receptors within the body of a skeletal muscle that primarily detect changes in the length of the muscle)
Other than simple, direct connection, what are the other connections that allow reflex to serve postural control function?
Synergistic and inhibitory
Muscles can only ____ (pull, push, contract)
Pull & contract
Muscle contracted, stretched
Agonist, extensor
Muscle relaxed, bending a limb
Antagonist, flexor
Other than stretch receptors, reflexes can also be triggered by? Name 2 sample reflex
Sensory afferents
nociceptive withdrawal reflex, pupillary light reflex
With the ‘reflex’ theory of nervous system we mean that
The nervous system is entirely reactive to external stimuli
Simple spinal motor circuits can sometimes exhibit ______ patterned activity. Give an example.
spontaneous; central pattern generators
What is often predictive rather than reactive to external stimuli? and what does it depend?
Motor control; context (the ‘cognitive state’ of the subject)
What can isolated spinal cords able to do?
Orchestrating complex movements
Can spinal cord orchestrating complex and intricate movement patterns?
Yes
Primary motor cortex (M1) connects directly to ___________ via the _________
Spinal motor neurons; cortico-spinal tract
Name the motor related areas of cortex. (6)
Frontal eye fields Supplementary motor area Primary motor cortex Somatosensory cortex Broca's area Premotor area
What is Penfield’s Homunculi? (recognise)
A distorted representation of the human body, based on a neurological “map” of the areas and proportions of the human brain
Which 3 cortex have a somatotopic organisation?
Primary, supplementary and premotor cortex
How are the primary, supplementary and premotor cortex tuned?
Movement direction tuned
What do primary, supplementary and premotor cortex collaborate with to compute movement intentions?
Basal ganglia and the spinal cord
How are overall movement direction is specified?
By a ‘population vector’ which weights preferred direction of each neuron by how strongly it is activated
How can population vectors can be ‘read out’ in real time?
With multi-electrode arrays
Reading out population encoding of motor intention makes what possible?
Brain-machine interfaces
Where does the cortico-spinal tract originate?
The deep layers of M1
Instead of specifying which motor unit to contract, how do neurons encode movement?
Encode the direction to move a limb in
Which areas specify co-ordinated movements involving more than one muscle or limb?
Supplementary and pre-motor areas
Which cortex contains mirror neurons?
Pre-frontal cortex
What do the mirror neurons do?
Encode ‘actions’ irrespective of who the action is performed by
Which side does the Broca’s area lateralise?
To the left
What does the Broca’s area do?
Produce grammatical speech
Damage to Broca’s leads to __________ while leaving the ability to _______ intact.
motor aphasia; understand speech
Wernicke’s area is not well defined, but which part does it involve?
Boundary of the superior temporal and parietal area on the left hemisphere
Which area is more responsible for speech understanding?
Wernicke’s area
Broca’s aphasia is usually associated with lesion to the __________
left frontal cortex
What is the name of the big fibre bundle that connects Broca’s and Wernicke’s area?
Arcuate Fasciculus
The further up you go the motor hierarchy, the _____ activity will precede the _______
more; actual movement initiation
Already in the ________ you can get electrical activity as much as half a second prior to a spontaneous, self-timed movement. (bereitschaftspotential/ _____)
supplementary motor area; readiness potential
If electrically stimulate M1, people will_______.
feel their limbs are being moved
If stimulate _______, they feel they want to move
supplementary motor areas
