أسباب وأعراض الحمل خارج الرحم

 💢 فسيو عصبي , motor 4

#Physiology_of_CNS 14

#CNS

#⃣Spinal organization of motor systems :👇👇👇

## ايش هاد العنوان ي دكتور🤔 حاااضر هاد معناه ي حلوين👇👇

🔷تنظيم العمود الفقري للأنظمة الحركية👌 وهاد بتم عن طريق 3 اشياء👇

0⃣Convergence :👇👇👇

🔹occurs when a single α-motoneuron receives its input from many muscle spindle group Ia afferents in the homonymous muscle. 

🔹produces spatial summation because although a single input would not bring the muscle to threshold, multiple inputs will.

 

🔹also can produce temporal summation when inputs arrive in rapid succession .

1⃣Divergence :👇👇👇

🔹occurs when the muscle spindle group Ia afferent fibers project to all of the α-motoneurons that innervate the homonymous muscle👌

2⃣ Recurrent inhibition (Renshaw cells ):👇👇👇

🔹Renshaw cells are inhibitory cells in the ventral horn of the spinal cord👌

🔹They receive input from collateral axons of motoneurons and, when stimulated, negatively feedback (inhibit) on the motoneuron 👌

#⃣Brain stem control of posture :👇👇👇

1⃣Motor centers and pathways :👇👇👇

🔸 Pyramidal tracts (corticospinal and corticobulbar) pass through the medullary pyramids👌

 

🔸All others are extrapyramidal tracts and originate primarily in the following structures  

of the brain stem: 👇👇👇

A.Rubrospinal tract:👇👇

🛑 originates in the red nucleus and projects to interneurons in the lateral spinal cord👌

🛑Stimulation of the red nucleus produces stimulation of flexors and inhibition of Extensors👌

B.Pontine reticulospinal tract:

🛑 originates in the nuclei in the pons and projects to the ventromedial spinal cord.

 

🛑 Stimulation has a general stimulatory effect on both extensors and flexors, with the  

predominant effect on extensors👌

C. Medullary reticulospinal tract:👇👇👇

🛑 originates in the medullary reticular formation and projects to spinal cord interneurons in the intermediate gray area. 

🛑 Stimulation has a general inhibitory effect on both extensors and flexors, with the  

predominant effect on extensors👌

D. Lateral vestibulospinal tract:

قد يعجبك ايضا

🛑originates in Deiters nucleus and projects to ipsilateral motoneurons and  

interneurons.

 

🛑 Stimulation causes a powerful stimulation of extensors and inhibition of flexors👌

E.Tectospinal tract:👇👇

🛑originates in the superior colliculus and projects to the cervical spinal cord. 

🛑is involved in the control of neck muscles 👌

💢 فسيو العصبي ، motor 5

#Physiology_of_CNS 15

#CNS

2⃣Effects of transections of the spinal cord :👇👇👇

*⃣Paraplegia:👇👇

■ is the loss of voluntary movements below the level of the lesion. 

■ results from interruption of the descending pathways from the motor centers in the  

brain stem and higher centers. 

*⃣Loss of conscious sensation below the level of the lesion .

*⃣Initial loss of reflexes—spinal shock.

■ Immediately after transection, there is loss of the excitatory influence from α- and γ-motoneurons. Limbs become flaccid, and reflexes are absent. With time, partial recovery and return of reflexes (or even hyperreflexia) will occur.

🔴Remember that:👇👇

(1) If the lesion is at C7, there will be loss of sympathetic tone to the heart. As a result, heart rate and arterial pressure will decrease👌

(2) If the lesion is at C3, breathing will stop because the respiratory muscles have been  

disconnected from control centers in the brain stem👌

(3) If the lesion is at C1 (e.g., as a result of hanging), death occurs👌

3⃣Effects of transections above the spinal cord:👇👇👇

🛑Lesions above the lateral vestibular nucleus:👇👌

■ cause decerebrate rigidity because of the removal of inhibition from higher centers,  

resulting in excitation of α- and γ-motoneurons and rigid posture. 

🛑 Lesions above the pontine reticular formation but below the midbrain:👇👌

■ cause decerebrate rigidity because of the removal of central inhibition from the pontine reticular formation, resulting in excitation of α- and γ-motoneurons and rigid  

posture.

🛑Lesions above the red nucleus:👇

■ result in decorticate posturing and intact tonic neck reflexes.