Why is central nervous system important…
Hyderabad: This is in continuation to the last article focusing on neural system and mechanisms of neural coordination in a human body. Today, we will continue discussion on the central nervous system focusing on midbrain and hindbrain, and how reflex action happens. Midbrain • The midbrain is located between the thalamus/ hypothalamus of the forebrain […]
Hyderabad: This is in continuation to the last article focusing on neural system and mechanisms of neural coordination in a human body. Today, we will continue discussion on the central nervous system focusing on midbrain and hindbrain, and how reflex action happens.
Midbrain
• The midbrain is located between the thalamus/ hypothalamus of the forebrain and pons of the hindbrain.
• A canal called the cerebral aqueduct passes through the midbrain.
• The dorsal portion of the midbrain consists mainly of four round swellings (lobes) called corpora quadrigemina.
Hindbrain
• The hindbrain comprises pons, cerebellum and medulla (also called the medulla oblongata).
• Pons consists of fibre tracts that interconnect different regions of the brain.
• Cerebellum has very convoluted surface in order to provide the additional space for many more neurons.
• The medulla of the brain is connected to the spinal cord.
• The medulla contains centres which control respiration, cardiovascular reflexes and gastric secretions.
• Three major regions make up the brain stem – midbrain, pons and medulla oblongata.
• Brain stem forms the connections between the brain and spinal cord.
Reflex action and reflex arc
• We must have experienced a sudden withdrawal of a body part which comes in contact with objects that are extremely hot, cold, pointed or animals that are scary or poisonous.
• The entire process of response to a peripheral nervous stimulation, that occurs involuntarily, i.e., without conscious effort or thought and requires the involvement of a part of the central nervous system is called a reflex action.
• The reflex pathway comprises at least one afferent neuron (receptor) and one efferent (effector or excitor) neuron appropriately arranged in a series.
• The afferent neuron receives signal from a sensory organ and transmits the impulse via a dorsal nerve root into the CNS (at the level of spinal cord). The efferent neuron then carries signals from CNS to the effector.
• The stimulus and response thus form a reflex arc as shown below in the knee-jerk reflex.
To be continued…
