Please enable JavaScript.
Coggle requires JavaScript to display documents.
Motor control (Somatic Reflexes (Nature of reflexes: quick, involuntary…
Motor control
Somatic Reflexes
Nature of reflexes: quick, involuntary and stereotypes reactions of peripheral effectors to stimulation
Muscle Spindle - is a stretch receptor located in a muscle. It is a cigar shaped affair containing 3-12 modified muscle fibres, wrapped in fibrous capsule
Stretch Reflex - when muscle is stretched, it contracts to maintain tone. This is the stretch reflex. (Tendon reflex is an example of monosynaptic reflex arc)
Reciprocal inhibition - for reflexes like knee jerk to work, there must simultaneously be reciprocal inhibition of antagonistic muscles
-
Cross Extensor reflex - to lift one foot quickly to avoid injury (flexor reflex), the body must maintain balance. Involves the cerebellum and spinal. The flexor reflex is ipsilateral; the crossed extensor reflex is contralateral.
Golgi-tendon reflex: organs are proprioceptors located at the junction of a muscle and its tendon. Golgi tendon organs produce an inhibitory response called the golgi tendon reflex when muscles contracts too tightly (prevents damage to tendon)
Motor Commands: Initiation, checking and command centers
-
Intention to contract a muscle originates in the premotor (motor association) Area of the frontal lobes. It can be modified and coordinated by the basal nuclei and cereberllum, so the resulting muscle contraction is smooth. Program transmitted to Primary motor area in the Precentral Gyrus
-
Cerebellum Motor functions: motor coordination, learning motor skills, maintaining muscle tone and posture, smooth muscle contractions, coordinated eye and body movements and Lesions: clumsy, awkward gait
Command sent from Primary motor area to the brainstem and spinal cord via descending tracts. This ultimately leads to muscle contraction
PNS protections: the connective tissue layers are epineurium, perineurium and endonerurium
Descending Spinal Tracts down the brainstem and spinal cord. The upper motor neuron begins with a soma in cerebral cortex/ brainstem and has an axon that terminates on a lower motor neuron in the brainstem/ spinal cord. The axon of the lower motor neuron leads the rest of the way to the muscle or other target organ.
Corticospinal tracts: carry motor signals from cerebral cortex for finely coordinated limb movements. Fibres form ridges called pyramids on the anterior surface of medulla oblongata. These fibres decussate in the lower medulla and form the lateral corticospinal tract on the contralateral side on the spinal cord.
Uncrossed fibres form the anterior corticospinal tract on the ipsilateral side. These fibres decussate lower in the spinal cord and control contralateral muscles
Tectospinal Tract begins in a midbrain region called the tectum and crosses to contralateral side of midbrain. It descends through brainstem to the upper spinal cord on that side, going only as far as the neck. It is involved in reflex turning of the head, especially to sights and sounds
Lateral and medial reticulospinal tract originate in the reticular formation of the brainstem. They control muscles of the upper and lower limbs, to maintain posture and balance
Lateral and medial vestibulospinal tracts begin in the brainstem vestibular nuclei, which receive impulses for balance from the inner ear. The lateral vestibulospinal tract passes down the naterior column of the spinal cord and facilitates neurons that control extensor muscles of the limbs, inducing limbs to stiffen and straighten. Importnat for dalance
The medial vestibulospinal tract splits into ipsilateral and contralateral fibres that descend through the anterior column on both sides of the SC and terminate in the neck. It plays a role in the control of head position
-