Lecture nine: control of movement Flashcards
what are Extrafusal Muscle fiber?
<2muscles attached to the bones by tendons, for movement”
Activated by alpha motor neurons
Intrafusal muscle fibers
set makes muscle spindle
Wrapped by afferent fibers (sensory endings)
But also: activated by gamma motor neurons
For detection of muscle length
For detection of muscle length
Golgi tendon organ
for detection of change in muscle tension
Pacinian corpuscles and free nerve endings
for detection compression of muscle (during contraction) and waste products
What does Myofibrils consist of?
Myofibrils in extrafusal fibers consist of Actin and Myosin
mechanism of muscle contraction
- Myosin (yellow) binds actin (pink).
- Myosin heads fall over and slide forward along the actin.
- Myosin heads release
- Rest condition
What is the Monosynaptic stretch-reflex?
- weight falls on hand
2.detection
muscle extension - reflexive muscle contraction
What is the Polysynaptic inhibitory-reflex?
Inhibition α neuron by Golgi tendon organ
prevents excessive tension on muscle
Lift more by sedating Golgi tendon organs
Explain the function of monosynaptic stretch
reflexes
Monosynaptic stretch responses function to control limb
movements when weight is applied or removed quickly
and to maintain upright posture.
Contrast the structures and function of
polysynaptic reflexes with monosynaptic reflexes:
Monosynaptic reflexes include a single synapse involved
in simple reflexes like the patellar reflex. Polysynaptic
reflexes involve multiple synapses involved in more
complex reflexive behavior, such as inhibiting a
withdrawal reflex. Polysynaptic reflexes contain at least
one interneuron between the sensory neuron and the
motor neuron.
Corticospinal paths
Lateral group:
for independent limb movements:
(very importat sh$t)
Rubrospinal tract (via red nucleus)
lower arms, hands (not fingers)
lower legs, feet (not toes)
Corticobulbar tract
neck, face, eyes, tongue
Lateral corticospinal tract
arms, hands, fingers
legs, feet, toes
Rubrospinal tract
Rubrospinal tract (via red nucleus)
lower arms, hands (not fingers)
lower legs, feet (not toes)
Corticobulbar tract
neck, face, eyes, tongue
Lateral corticospinal tract
Lateral corticospinal tract
arms, hands, fingers
legs, feet, toes
What is the Ventromedial group for:
for balance (body posture) and walking and controlled via nuclei in brainstem
Ventral corticospinal tract
Body posture: trunk and upper legs
tectospinal tract
Orientation: trunk and head/eye movements
vestibulospinal tract
Body posture: trunk and legs
reticulospinal tract (1: lateral PRF)
Walking: bending legs
reticulospinal tract (2: medial MRF
Walking: stretching legs
reticulospinal tracts for autonomic functions:
: muscle tension, breathing, coughing, sneezing
The lateral group consists
of the
the corticospinal tract, the corticobulbar tract, and the
rubrospinal tract. This system is primarily involved in control
of independent limb movements, particularly movements of
the hands and fingers.
The Cerebellum
motor coordination
Cerebellum: damage
lateral system
problems with timing (agonist-antagonist) muscles results in tremor in particular at the endpoint of movements
What is the SMA
SMA: Supplemantary Motor Cortex
SMA: in particular for planning movement sequences
Neuron specifically active during “pull-push” sequence
(not during “push”, “pull”, “turn” only, or during other sequences such as: “Push-Pull”)
PMC
Premotor Cortex: planning movements
Damage to parietal lobe leads to
Apraxia (no action)
inability to carry out complex actions
without pareses
What are the symptoms of 1: Limb apraxia after damage to left parietal lobe
Use wrong body parts
Correct body parts but incorrect movement
Wrong sequence of movements
Especially during:
Imitating actions
Demonstrating actions with tools
Constructional apraxia
Constructional apraxia after damage to right parietal lobe
Problems with copying figures
Problems with building larger objects from smaller elements
In fact more a visual problem: difficulty with combining the individual elements to recognize a whole object
Explanation left-right difference:
Left parietal: representation own body (limb apraxia)
Right parietal: representation outside world (constructional apraxia)
Basal Ganglia:
motor gating
parts of the basal Ganglia
- Caudate nucleus
- Globus pallidus
- Putamen
where do informations for caudate nucleus and putamen come from»?
Caudate en Putamen: input from primary motor and somatosensory cortex and substantia nigra
where do informations from globus pallidus go?
output to motor nuclei brainstem and primary motor and premotor cortex and SMA (via thalamus)
