Central Nervous System

peripheral nervous system

Neurons

Glial cells

With the participation of the central nervous system, the body's regular responses to internal and external stimuli are called reflexes

reflex arc

excited

Reflexes formed through learning and training during life after birth are called unconditioned reflexes

Conditioned reflexes are established through learning and training on the basis of unconditioned reflexes

When not stimulated, nerve fibers are in a resting state. At this time, the concentration of Na ions outside the nerve cell is higher than that inside the membrane, and the concentration of K ions is lower than inside the membrane. The permeability of the nerve cell membrane to different ions is different: at rest, the membrane is mainly permeable to K property, causing K ions to flow out, making the cation concentration outside the membrane higher than inside the membrane. Due to the specific ion distribution characteristics inside and outside the cell membrane, the potential on both sides of the cell membrane is negative inside and positive outside, which is called the resting potential.

When a certain part of the nerve fiber is stimulated, the permeability of the cell membrane to Na increases, Na ions flow in, and a temporary potential change occurs on both sides of the membrane at this part, showing a positive state inside and negative outside. The membrane potential at this time is called action potential. The adjacent unexcited parts are still negative on the inside and positive on the outside. Due to the existence of potential difference between the excited site and the unexcited site, charge movement occurs, thus forming a local current.

synaptic structure

cerebral cortex

Appropriate stimulation → receptor → afferent nerve → spinal cord → efferent nerve → effector

The hypothalamus is a higher-level center that regulates visceral activities. It also connects visceral activities with other physiological activities to regulate major physiological processes such as body temperature, water balance, and food intake. The cerebral cortex is the high-level regulator of many low-level central activities. It regulates the activities of centers at all levels, which makes the autonomic nervous system not completely autonomous.

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