1、 Composition of nervous system
The nervous system consists of central nervous system and peripheral nervous system. The basic organization of the nervous system is nervous tissue.
1. Central nervous system: including the brain in the cranial cavity and the spinal cord in the vertebral canal.
2. Peripheral nervous system: It is a nerve component other than brain and spinal cord.
2、 Basic activity mode of nervous system
When the nervous system regulates the body's activities, it makes appropriate responses to the stimulation of the internal and external environment, which is called reflex. Reflex is the basic activity mode of nervous system.
The morphological basis of reflex activity is the reflex arc, which is composed of receptors, afferent nerves, nerve centers, efferent nerves and effectors.
3、 Central nervous system
1. Spinal cord
It is located in the spinal canal and divided into 31 segments according to the access range of 31 pairs of spinal nerve roots, namely 8 cervical segments, 12 thoracic segments, 5 lumbar segments, 5 sacral segments and 1 caudal segment.
Functions of spinal cord: conduction function, reflex function.
2. Brain
The brain is located in the cranial cavity, and its shape and function are more complex than those of the spinal cord. The brain is divided into 6 parts: telencephalon (brain), diencephalon, cerebellum, midbrain, pons, and medulla oblongata. 12 pairs of brain nerves. The thinking activity of the brain is realized by a large number of reflex activities connecting neurons.
(1) Brain stem: located in the front of the posterior cranial fossa, it consists of the medulla oblongata, pons, and midbrain. The functions of brain stem include: conduction function, low level center of reflex, and function of reticular structure.
(2) Medulla oblongata: there are many basic life activity centers in the medulla oblongata, such as blood vessel movement, respiration, heartbeat and vomiting centers. Therefore, the medulla oblongata is called the "life center".
(3) Cerebellum: located in the posterior cranial fossa, below the occipital lobe of the brain, at the back of the medulla oblongata and pons. The fourth ventricle is between pons, medulla oblongata and cerebellum.
Functions of cerebellum: coordinate body movement, regulate muscle tension, and maintain balance; Cerebellar injury will not lead to the loss of random movement (muscle paralysis), but there will be postural, balanced gait and motor control disorders, as well as decreased muscle tension. Muscle relaxation and other phenomena may also cause pronunciation disorders.
4、 Peripheral nervous system
1. Composition of spinal nerve
Spinal nerves are 31 pairs of peripheral nerves connected to the spinal cord. From top to bottom, the spinal nerves are 8 pairs of cervical nerves, 12 pairs of thoracic nerves, 5 pairs of lumbar nerves, 5 pairs of sacral nerves, and 1 pair of caudal nerves.
2. Brain nerves
Brain nerves refer to the peripheral nerves connected with the brain, a total of 12 pairs. Vagus nerve is the longest and most widely distributed nerve in the brain.
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