muscle 1.6

Question 1

cerebral cortex : what are the lobes that make it up

Answer 1

cerebral cortex made up of 4 lobes : frontal, parietal, temporal and occipital

Question 2

cerebral cortex function and different cortex

Answer 2

planning and ongoing control of voluntary movements

• premotor area
• supplementary motor cortex
• primary motor cortex (motor cortex)
• somatosensory cortex
• parietal lobe association cortex

Question 3

parietal lobe association cortex

Answer 3

important for reaching and grasping for something

Question 4

descending pathways come from what two parts of the motor area

Answer 4

primary and premotor area

Question 5

somatotopic map - neurons of the motor cortex

Answer 5

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

Question 6

subcortical and brainstem nuclei : function

Answer 6

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

Question 7

subcortical nuclei : basal nuclei

Answer 7

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

Question 8

parkinsons disease **

Answer 8

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

Question 9

substantia nigra

Answer 9

produces dopamine and is important for transmitting messages that control movement

Question 10

gait

Answer 10

problems walking in the usual way

parkinsons trouble initiating gait

Question 11

where does parkinson’s arise and how does this disease impose its effect

Answer 11

-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

Question 12

treatment for parkinson’s **

Answer 12

restore dopamine activity :

1. stimulating dopamine receptors with an agonist
2. inhibit the enzyme that metabolizes dopamine at synapses
3. precursors of dopamine itself (levodopa or L -dopa)

Question 13

function of L dopa

Answer 13

crosses blood brain barrier and converts to dopamine in neuron and goes to dopamine receptors

-DOPAMINE CANT CROSS BBB

Question 14

cerebellum functions *

Answer 14

-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

Question 15

other functions of cerebellum*

Answer 15

(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

Question 16

cerebellar disease

Answer 16

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

Question 17

descending pathways

2 types

Answer 17

-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

Question 18

corticospinal pathway

Answer 18

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

Question 19

corticobulbar pathway

Answer 19

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

Question 20

brainstem pathways

Answer 20

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

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