lecture 8 * biology and cognition *

1. extrafusal muscle fiber
2. intrafusal muscle fibers
3. raped afferent fibers
4. gamma motor neurons
5. golgi tendon

muscles attached to the bones by tendons

used for movement

activated by alpha motor neurons

they do not move joints they contract along with the large muscle fibers

gives information on length of muscle

spindle

dorsal route

sensory endings

activate gamma motor neurons

precise motor information

detection of stretch (" tension") on muscle

information about how much stretch is on the muscle

1. muscle spindels ( MS)
2. golgi tendon

MS1 fires slow constant rate

MS1 slow and constant

MS2 fires quickly

GTO gogli tendon for abrupt movemet

myofibrils

in extrafusal fibers

actin and myosin

pull in action

1. myosin (yellow) binds action (pink)

2. myosin heads release

3. myosin heads fall over and slide forward along

4. resit condition

reflex that provides direct communication between sensory and motor neurons innervating the muscle

weight falls on hand

dorsal sensors detect change

activate alpha motor neurons

contract the muscles

reflective muscle contraction

inhibition a neuron by golgi tendon organ prevents excessive tension on muscle

chloride channels open and the firing stops

lift more by sedating golgi tendon organs

rostral region

representation of how much. motor cortex is devoted to each part of the body

1. lateral group
2. ventromedial group

independent limb movements:

1. rubrosiinal tract
2. corticotubular tract
3. lateral corticispinal tract

via red nucleus ): lowe arms hands (not fingers lower legs, feet (not toes)

neck face eyes tongue

arms hands fingers legs feet toes

for balance ( body posture) and walking

body posture : trunk and upper legs

motor coordination

sends information on exact contribution of muscles and timing

dentate nucleus

thalamus

to cortex and red nucleus

planned movements

from cortex

pontine nucleus

problems with timing ( agonist antagonist) muscles

you go to your goal overshoot

stop at the right moment undershoot

Supplementary Motor Area

during " pullpush" sequence

each neuron codes for a specific movement sequence

plan is converted before the motor cortex

intentions come from the back of the brain

motorplan makes it happen

apraxia

inability to carry out complex actions without paralysis

1. limb
2. constructional

use wrong body parts

correct body parts but incorrect movement

wrong sequence of movements especially during imitating actions

problems copying figures

problems during building larger objects from smaller elements

in fact more visual problem : difficulty with combining the individual elements to recognize a whole object

representation of own body (limb apraxia)

epresentation of outside world (constructional apraxia)

a group of structures found deep within the cerebral hemispheres used in motor functions

caudate nucleus

globus pallidus

putamen

input from primary motor and somatosensory cortex and substantia nigra

output to motor nuclei brainstem and primary motor and premotor cortex and SMA via thalamus

doing all the " plans we have with something we see"

allows us to do just one of them

tourettes

1. direct path
2. indirect path

promotes more activity

1. cortex activates caudate and putamen
2. more inhibition GPi
3. less inhibition thalamus
4. more excitation cortex

less inhibition = more excitation

thalamus excitatory role

inhibits motor activity

1. cortex activates caudate and putamen
2. more inhibition GPe
3. less inhibition subthalamic nucleus
4. more inhibition thalamus
5. less excitation cortex

inhibit GPe or GPi

inhibits thalamus

less inhibition = more inhibition thalamus

role : excite thalamus

inhibits subthalamic nucleus

D1 : excite direct patch

D2 : inhibit indirect path

1. Parkinson's diesses
2. Huntington's diessese

motor problems due to loss of dopaminergic neurons in substantia nigra

rigidity and tremor

starting and stopping to move difficult

impapired postural reflexes are

treat with L dopa

or electrical stimulation STN / GPI ( inhibit indirect pad )

movements due to loss of caudate/putamen neurons that inhibit the GPe

heritable : involuntary movements
dystonia : cramped posture
athetosis : wiggling toes
ballismus : wild movements
in the end also memory loss and mood problems