(2)4 is efferent nerve, which can transmit nerve impulses from nerve center 3 to effector 5.
(3) Xiaoming accidentally touched something hot with his finger and immediately retracted his hand. At this time, the pathway of nerve impulse transmission is 1 receptor →2 afferent nerve →3 nerve center →4 efferent nerve →5 effector (biceps brachii contraction and triceps brachii relaxation) to retract the hand. After retracting his hand, he felt fever, which originated from the somatosensory center of the cerebral cortex.
(4) The basic structure of neurons consists of cell body and process. The cell bodies of neurons are mainly concentrated in the brain and spinal cord. In the brain and spinal cord, where the cell bodies are dense, the color is dark, called gray matter; The processes of neurons are mainly concentrated in the peripheral nervous system. In the area where nerve fibers converge in the brain and spinal cord, bright white is called white matter. So in the brain and spinal cord, gray matter is composed of cell bodies of neurons, and white matter is composed of nerve fibers. In the picture, A is gray matter and B is white matter. Therefore, in the spinal cord, the dense area of neuronal cell body is gray matter.
(5) As shown in the figure, the nerve center of reflex is in the spinal cord, and it does not need the participation of cerebral cortex, which belongs to unconditional reflex (simple reflex).
So the answer is: (1) 1 receptor.
(2)4? efferent nerve
(3) 1→2→3→4→5? The somatosensory center of the cerebral cortex?
(4) a? grey matter
(5) Simple reflection