Medulla oblongata
Lower part of mid brain. Length; 2'5cm
Medulla oblongata extends from pons above and is continuous with spinal cord below and extends from foramen magnum to the pons.
The central canal of spinal cord continuous upward into medulla.
Both medulla and pons help form ventricle wall of fourth ventricle.
The outer aspect is composed of white mater, which passes between brain and spinal cord and grey mater, which lies centrally.
Network of grey mater and white mater called reticular formation.
Medulla oblongata
1. External features
Anterior
posterior
2. Internal features
Pyramid decussation; crossing
Sensory decussation
Olive
Reticular formation
Medulla oblongata has special features;
1. Decussation of pyramids
Control motor activity; cerebrum to spinal cord
In medulla, motor nerves descending from the motor area in cerebrum to spinal cord in pyramidal tracts cross from oneside to another .
This means processing of impulse from right side to left side or from left side to right side occurs in medulla. That's why left hemisphere of cerebellum control the right half of body and right hemisphere of cerebrum control the left half of body.
These tracts are main pathway to skeletal (voluntary muscle)
2. Sensory decussation
Control sensory activity; spinal cord to cerebrum
Some of sensory nerves ascending to cerebrum from spinal cord cross from one side to the other in medulla.
3. Olive
Situated lateral to each pyramid is an oval shaped swelling called Olive.
In medulla oblongata vital centers, consisting group of cell bodies (nuclei) associated with autonomic reflex center, these are-
Cardiovascular center
Respiratory center
Reflex center
Cardiovascular center
The cardiovascular center in medulla oblongata control the rate of cardiac contraction. It also control blood pressure.
Respiratory center
The respiratory centre in medulla oblongata control the rate and depth of breathing and maintain respiratory rhythm.
Reflex center
Activate reflex in response of foreign bodies.
Connection made between afferent and efferent neuron.
Protect body from harm, irritants present in stomach and respiratory track stimulate the medulla oblongata, activating the reflex center. The vomiting, coughing, sneezing, reflex start to expel the irritants outside.
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