lecture 5 - movement control

Question 1

what region is responsible for planning of voluntary movement

Answer 1

-descending systems - neurons descend from cortex to the neurons in the body

Question 2

what is the brainstem concerned with

Answer 2

-concerned with unconscious movement control, things such as movement and posture
-things we don’t put a lot of thought into

Question 3

-basal ganglia
-cerebellum

Answer 3

-basal ganglia : gatekeeping mechanism , responsible for allowing movements we want to make to be made and stopping movements - connects to motor cortex
-cerebellum - more unconscious control, motor coordination and balance etc - connects to brain stem centre

Question 4

motor cortex

Answer 4

-motor cortex descents down to local circuit neurons - connect to motor neurone pools

Question 5

description
motor cortex
-function

-monkey study

Answer 5

-premotor and primary motor cortex in the frontal lobes
-premotor is more responsible for planning than primary motor
-primary cortex responsible for starting off movements
-responsible for planning and more precise control in voluntary movements

-monkey study
-trained monkey to respond with an action when they saw a particular cue
-but there was a delay between seeing the cue and seeing a go signal that indicated for you to do the signal
-so by recording brain activity they found that during the delay period whilst waiting to produce the response , the premotor cortex is active

Question 6

organisation of the motor cortex
-contralateral control
-type of organisation

Answer 6

-contralateral control - (neurons in motor cortex on the left hemisphere are responsible for movements on the right side of the body
-somatotopically organised (penfield 1930). its grouped by body part-
-muscles are disproportionately represented eg hands or digits have more space in motor cortex than arm etc-look at penfie guy who represents what we would look like according to amount of body part represented in cortex

Question 7

motor mapping
-wilder penfield 1937 and the montreal procedure

Answer 7

-montreal procedure developed whilst treating epileptic patients and operating on them

-4 patients suffering from epilepsy: went through some pre surgery process where the patient would be conscious, would stimulate the nerves of the brain in order to record what responses they produced
-identified areas of the brain which caused seizures (have bursts of excess activity)

Question 8

what does motor map represent/not represent
-whatdo lesions in the motor cortex cause

Answer 8

map doesnt represent individual muscles / body parts, but co ordinated groups of muscles

-lesions to motor cortex regions cause deficits in muscle groups (because the muscle groups do actually overlap, not as distinct as thought)

Question 9

TMS
transcranial magnetic stimulation of motor cortex
-the video

Answer 9

-magnetic coil over motor cortex
-when delivers a magnetic pulse part of body moves
-hempisphere activates response in opposite side of body

Question 10

key motor areas having more representation in the motor cortexin animals

Answer 10

in animals
-increased representation of paws in racoons (they have tiny people hands and are dexterous)
-increased representation of whiskers in rats and mice
-increased representations of the nose in the star nose mole

-all innate

Question 11

if someone learns a skill will we see a change in the motor cortex as a result of their learning

Answer 11

-several studies show this
-looking at violinists or string players
-they have larger representation for left hand digit : require extra control (catania and kaas, 1995)

Question 12

basal ganglia
-functions
-major structures

Answer 12

underneath the cortex
-gatekeeper for initiating movements (preparation for movement)
-full of dopaminergic synapses and their receptors- a key part of this region
-striatum (caudate nucleus,putamen)
-pallidum ( globus pallidus, substantiatnigra)
-thalamus
-subthalamic nucleus

Question 13

the basal ganglia
-what does the pathway do
-things to be aware of

Answer 13

-allows the start/initiation of intended movements
-regions are linked in a circuit of inhibitory(reduced change action potential sends) and excitatory impulses
-some regions will be constantly inhibited/activated (tonic)
-others will be inhibited / activated for brief periods of time only (transient)
-correct regulation of this is vital in allowing movement to begin

Question 14

direct pathway
-and which neurons are tonic and transient

Answer 14

-caudate and putamen
-globus pallidus internal - va/vl complex thalamus-frontal cortex
-globus pallidus tonically active

Question 15

the direct pathway in a situation where no movement is being planned

Answer 15

-in this situation no movement is being planned
-when a is at rest (striatum) is currently not firing

-the neuron in the globus pallidus (b) is tonically active , always firing and sending out signals, it has an inhibitory connection with the thalamus,(c) it stopping the thalamus from sending out signals

-thalamus has other inputs from other regions which are excitatory , (but cell has to add al inputs together to get an outcome)
so thalamus isn’t communicating with the moto cortex and no motor actions are starting (no excitation of D -motor cortex)

Question 16

direct pathway in movement

Answer 16

-a is transiently excited (frontal cortex signals to a , the striatum) striatum fires so burst of transient activity

-striatum (a) has a inhibitory connection to the global pallidus so it switches it off (b is transiently is inhibited)

-c is disinhibited so other inputs can excite it (c is va vl complex)

-leading to excitation of D(the motor neuron cortex)

Question 17

dopamine : the nigrostriatal pathway
-what is this

Answer 17

-substantia niagra to striatum
involved in the basal ganglia loop and the initiation of movement

Question 18

explain the nigrostriatal pathway

Answer 18

-links substantia nigra and striatum (caudate/putamen)
-provides additional excitatory impulses
-more likely to inhibit the globus pallidus
-allows the frontal cortex to initiate movement

Question 19

disorders of basal ganglia : movement initiation, involed in direct pathway

Answer 19

-direct pathway: involved in the release of the upper motor neurons from inhibition
-linked to parkinsons disease
-hypokinesis (reduced initiation of movement)

Question 20

parkisons disease (and dopamine)
-what is it
-symptoms

Answer 20

-neurodegenerative progressive disorder - described by dr james parkinson in 1817
-the most recognised symtomps are those that affect movement
: tremor
-slowness of movement (bradykinesia)
-rigidity
-postural instability

Question 21

what causes the movement issues in parkinsons disease

Answer 21

-issue in the substantia nigra
-substantia nigra gets its name from the melanin in the cells (produce melanin)

-in a healthy individual when you look at the region, the cells will be evident due to shading
-in parkinsons those are the cells that die off, reduced shading in those with parkinsons
-(melanin containing cells die off)

-causes ? unclear _combined genetics and environment?

Question 22

parkinson’s disease direct pathway

Answer 22

-death of the dopaminergic neurons in the nigrostriatal pathway
-reduction of activation of the striatum
-the striatum cannot inhibit the globus pallidus
-the thalamus continues to be inhibited
-movement therefore cant be easily initiated

Question 23

treatment of parkinsons disease

Answer 23

-l dopa
- L-Dopa

• Artificial precursor to dopamine, which can cross the blood brain barrier
• Increases the concentration of dopamine in the synaptic cleft (agonist of dopamine)
• As the cells continue to die, however, this treatment will gradually become less effective (it doesnt matter that theres extra materials to make dopamine from, theres simply arent the receptors for the dopamine to bind to
• Also: side effects due to increased dopamine in other pathways

Question 24

the indirect pathway
-what does it do

Answer 24

works to stop unwanted movements

Question 25

indirect pathway explained

Answer 25

-By increasing the ability of the globus pallidus (internal) to inhibit the thalamus * External segment inhibits the internal segment, preventing it from inhibiting the thalamus * External segment also inhibits the subthalamic nucleus, which excites the internal segment, further preventing it from inhibiting the thalamus to stop movement -cerebral cortex/striatum inhibit the external segment and excites subthalamic nucleus -so were taking out the inhibito of the internal segments and were boosting the region that boosts the internal segments -internal segment can inhibit thalamus -thalamus doesnt signal to cortex-movement is not initiatied

Question 26

disorders of the basal ganglia, movement inhibition (involved with indirect pathway)

Answer 26

-the indirect pathway: involved in increasing the level of inhibition -linked to huntingtons disease :hyperkinetic (increased unwwanted movement)

Question 27

huntingtons disease

Answer 27

-described by george huntington 1872 -genetic disorder caused by the mutation of the huntington gene on chromosome 4 -symptoms usually begin mid life (30-50 years) -changes in mood -problems with co ordination -decline in both physical and mental capacities -results in death within 10-20 years

Question 28

huntigtons is ______ dominant

Answer 28

autosomal dominant -if we have a dominant disorder it means that in order for somebody to inherit huntigntons they only need to inherit one copy of the gene from a parent

Question 29

what happens to the brain in huntingtons disease -and its effects

Answer 29

-profound but selective atrophy of the caudate and putamen -loosing much tissue mass from the regions -some associated degeneration of the frontal and temporal cortices -alteration in mood-usually depression -changes in perosnality - increase in irritability, suspiciousness, eccentric behaviour motor symptoms: -rapid, jerky movement with no clear purpose -can involve a finger of a whole extremetity, speech apparatus

Question 30

what's happening to the indirect pathway in huntingtins disease

Answer 30

-were losing the caudat and putamen because of the atrophy, so its no longer able to inhibit the external segments of the globus pallidus means that segment is much better able to inhibit the internal segment directly and indirectly by inhibiting the sub thalamic nucleus -sub thalamic nucleus cant excite the internal segments, thalamus is free to signal to the motor cortex and produce this unwanted extra movemnets

Question 31

treatments of huntingtons disease and side effects

Answer 31

-no cure -drug tetrabenazine is used to treat the chorea (unvoluntary movements) associated with it -antagonist of dopamine blocks dopamine receptors and depletes other amines -side effects include parkinsonism and depression

Question 32

three types of muscle

Answer 32

-skeletal/ striate muscles : movement of the bones -smooth muscle- forms organs such as stomach and bladder -cardiac muscles (a mix of smooth and striated) contracts the heart (last two are involuntary control)

Question 33

how are muscles arranged

Answer 33

-arranged in antagonistic pairs-each making only one movement -Contraction of the skeletal muscles is initiated by the lower motor neurons * The cell bodies of the LMNs are found in the spinal cord and brainstem * Their axons run down to particular muscles ,to form the Neuromuscular Junction

Question 34

the neuromuscular junction -what happens at this synapse -motor neuron pool -moto unit

Answer 34

-motor neuron synapses with skeletal muscle fibres -ACh acts as an excitatory NT at this synapse -nicotnic receptors -Each motor neuron innervates several fibres within one muscle * The motor neuron pool: All the neurons innervating one muscle * The motor unit: All the fibres in a muscle innervated by one neuron

Question 35

the lower motor neurons -size of motor unit relates to...

Answer 35

-the size of the motor unit relates to the type of movement that can be produced -when they innervate many fibres, movements will be coarser -eg biceps -when only a few fibres are innervated by one axon, movements are more precise eg eye movement

Question 36

organisation of lower motor neurons -spinal cord -arms and legs

Answer 36

-somatotopic organisation of the lmns -in the spinal cord,the neurons that act on the muscles of the trunk are located medially -the neurons for the arms and legs are found more laterally

Question 37

amytrophic lateralsclerosis (ALS) -discovery -what is it

Answer 37

-known as motor neuron disease or lou gehrigs disease -first link between symptoms and the neurological disorder by jean martin charcot (1874) -causes unknown in 90% cases -a degeneration of both upper motor neurons and lower motor neurons

Question 38

what happens in ALS

Answer 38

Progressive neurodegenerative disease * Neurons in the brain and spinal cord begin to die * Begins with weakness in the affected regions which gradually worsens over time as muscles waste * Different classifications according to which neurons are affected first * Sensory nerves and cognitive abilities are preserved * Symptoms and rate of progression vary between people

Question 39

what is augmented/alternative communication treatment

Answer 39

-one of the last muscular groups to be affected are the extraocular muscles (eye movements) -Augmentative/Alternative Communication (AAC)systems use this to help people with ALS communicate -Various technologies allow eye movements to be used like a computer mouse ◦ Graphical User Interfaces: Using images to indicate communication goals (e.g. Shravani et al., 2020) ◦ Using smooth-pursuit eye-movements to write with the eyes(Lenglet et al., 2019)