muscle 1.6 Flashcards
cerebral cortex : what are the lobes that make it up
cerebral cortex made up of 4 lobes : frontal, parietal, temporal and occipital
cerebral cortex function and different cortex
planning and ongoing control of voluntary movements
- premotor area
- supplementary motor cortex
- primary motor cortex (motor cortex)
- somatosensory cortex
- parietal lobe association cortex
parietal lobe association cortex
important for reaching and grasping for something
descending pathways come from what two parts of the motor area
primary and premotor area
somatotopic map - neurons of the motor cortex
map out major body parts in primary motor cortex
sizes depend on number of neurons we have controlling each part
-right-left switch over for controlling
subcortical and brainstem nuclei : function
interact with the cortex to control movements
-via indirect pathways to the motor neurons that ascend to the cerebral cortex and descend from the brainstem nuclei
function :
- planning and monitoring movements
- establish specific sequence of movements needed to accomplish a desired action
- learning skilled movements
subcortical nuclei : basal nuclei
they form a link in some of the looping parrallel circuits
- can facilitate or suppress movements
- basal nuclei to thalamus up to sensory motor cortex back to basal nuclei
parkinsons disease **
degenerative, progressive disease that affects the cells in the basal nuclei and substantia nigra
-causes decrease in DOPAMINE
symptoms
bradykinesia : slowness of movement
akinesia : reduced amount of movement
tremor at rest : involuntary shaking, tremor decreases with significant movement
rigidity : stiffness
postural instability : imbalance
change in facial expression : masklike, unemotional appearance
-shuffling gait with loss of arm swing
substantia nigra
produces dopamine and is important for transmitting messages that control movement
gait
problems walking in the usual way
parkinsons trouble initiating gait
where does parkinson’s arise and how does this disease impose its effect
-initial defect arises in neurons of the substantia nigra (not sure why)
-They project to the basal nuclei where they release dopamine from their axon terminals
→ have a decreased level of dopamine that is released which leads to a decrease activation of the sensorimotor cortex : sensory info→ motor response
treatment for parkinson’s **
restore dopamine activity :
- stimulating dopamine receptors with an agonist
- inhibit the enzyme that metabolizes dopamine at synapses
- precursors of dopamine itself (levodopa or L -dopa)
function of L dopa
crosses blood brain barrier and converts to dopamine in neuron and goes to dopamine receptors
-DOPAMINE CANT CROSS BBB
cerebellum functions *
-influences posture and movement
does this by input to the brainstem nuclei and to the thalamus which are going to the sensorimotor cortex and then the brainstem and spinal cord interneuron pathways which descend eventually to motor neurons
-feedback from the sensorimotor cortex and receptors **??
-receptors in eyes, muscles, skin, tendons etc
- direct path to sensorimotor cortex
- stores memories of movements
- compares what muscle should be doing vs what it is actually doing
other functions of cerebellum*
(at back of head looks like ball of yearn)
- provides timing signals
- helps coordinate movements with several joints
- stores memories of these movements
- helps plan movements
- looks for an error between intended vs performed
cerebellar disease
cannot perform limb or eye movement smoothly
- they move with an intention tremor (parkinson’s is a resting tremor)
- difficult to combine movements of several joints, cant achieve this with successful execution
descending pathways
2 types
-from various brain regions to the motor neurons
corticospinal pathways and brainstem pathways
- both end at synapses on alpha motor neurons, gama motor neurons or on interneurons
- overall effect of descending input to afferent system is to regulate their influence on either local or brain motor areas
corticospinal pathway
cell bodies are in the sensorimotor cortex and terminate in the spinal cord
- crossover near the junction of the spinal cord and brainstem
- if damaged movements are slower, weaker individual finger movements difficult, gripping stuff hard
corticobulbar pathway
cell bodies are in the sensorimotor cortex and ends in the brainstem
(spinal vs bulbar) (think of them together because of cross over)
controls indirectly and directly the interneurons of the motor neurons
- helps control eyes, mouth and throat as well as sudden movements of head and neck _(_all in head)
- voluntary movements of distal extremeties
- BOTH have convergence and divergence many neurons synapse on one neuron and visa versa **
- if damaged movements are slower, weaker individual finger movements difficult, gripping stuff hard
brainstem pathways
are uncrossed and affect muscles on the same side of the body, but a few do cross over to influence contralateral muscles
- involved in coordination of larger muscle groups and proximal portions of lymph
- fibres descend as distinct pathway named after the region they are from
more PROXIMAL
