Diagram of neuron structure
(1) As can be seen from Figure 1, the structure in Figure 1 involves 3 neurons, including 2 synapses, where A is the axon (nerve fiber), and B is the dendrite. (2) In Figure 2, ① is the receptor, ② is the afferent nerve, ③ is the efferent nerve, ④ is the effector, and ⑤ is the nerve center. At rest, the membrane potential is negative on the inside and positive on the outside. After being stimulated, the membrane potential becomes positive on the inside and negative on the outside. Therefore, after the receptor is stimulated, the outer membrane potential of the stimulated site changes from positive potential to negative potential. (3) Because nerve cells have more dendrites, the relative surface area of nerve cells is large, so that they can adapt to the information transmission function. (4) Studies have shown that children who live in a stimulating environment have a thicker cerebral cortex and a greater number of synapses in structure ⑤. It shows that the formation process of unconditioned reflex can significantly affect the number of synapses, which is beneficial to the development of intelligence. Therefore, the answer is: (1) 3 2 (2) ① from positive potential to negative potential (3) dendrites (or protrusions) (4) increase in synapses.
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Names of parts of the nervous system
Schematic diagram of nerve distribution in fingers
(1) The basic structure of a neuron includes two parts: cell body and process. The process of a neuron generally includes a long axon with few branches and several short dendrites with dendritic branches. The axon and the myelin sheath covering the outside are called nerve fibers, and the small branches at the end of the nerve fibers are called nerve endings. Nerve endings are distributed throughout the body; in the figure 1 is the nucleus, 2 is the cell body, 3 is the process, 4 is the nerve fiber, and 5 is the nerve ending. (2) When the finger sticks a nail, the [A] receptor receives the "pain" stimulation and generates a nerve impulse, and the nerve impulse is transmitted from the [B] afferent nerve to the specific [E] nerve center in the spinal cord. After the neuron receives the signal of "pain", it immediately generates a nerve impulse and transmits it to [C] efferent nerve, and then from C to [D] effector, and D shrinks the stimulus of "pain". Response back to the finger. While completing the above reflexes, the neurons in the spinal cord leading to the brain will also transmit impulses to the brain, causing people to feel pain. However, due to the long path to the brain, the fingers have already retracted before the brain makes a judgment. , This kind of reflex is born, it is a simple reflex, and its meaning is to prevent the fingers (body) from being seriously injured. (3) The axon and the myelin sheath covering it are called nerve fibers. Many nerve fibers are gathered into bundles and surrounded by a membrane formed by connective tissue to become a nerve. The B afferent nerve and C efferent nerve in Figure 2 are bundles of [4] nerve fibers in Figure 1, and the outer membrane is formed. The nervous system consists of the brain, spinal cord and the nerves they send out. The brain and spinal cord are the central parts of the nervous system, called the central nervous system; the cranial nerves coming out of the brain and the spinal nerves coming out of the spinal cord are the peripheral parts of the nervous system, called the peripheral parts. nervous system. Therefore, the B afferent nerve and the C efferent nerve in Figure 2 belong to the peripheral nervous system. (4) Observing Figure 2, we can know that there are three neurons that constitute the reflex arc: one located in the afferent nerve and two located in the nerve center. Therefore, the answer is: (1) cell body; protrusion; nucleus; nerve fiber; nerve endings (2) receptors; afferent nerve; nerve center; efferent nerve; effector; avoid serious damage to fingers (body) (3) [4] Nerve fibers; Peripheral (4) III.
The distribution of human brain functional areas, the location and function of functional areas, detailed explanation
The human brain consists of the cerebrum, cerebellum, diencephalon, and brainstem. Among them: The brain is the most advanced part of the central nervous system and the main part of the brain. Divided into the left and right cerebral hemispheres, the two are connected by the corpus callosum composed of nerve fibers.
The brain stem (brainstem) connects the cerebral hemispheres upwards and connects the spinal cord downwards, in an irregular columnar shape.
Nerve impulses traveling through the spinal cord to the brain enter in a crossing pattern: Impulses from the right side of the spinal cord travel to the left side of the brainstem before entering the brain; impulses from the left side of the spinal cord travel to the right side of the brainstem and then to the brain .
The function of the brain stem is mainly to maintain the life of the individual, including important physiological functions such as heartbeat, respiration, digestion, body temperature, and sleep, all of which are related to the function of the brain stem. The cerebellum is located below the cerebrum and occipital lobe, just behind the brainstem, and is the second largest part of the brain.
The cerebellum consists of two hemispheres, with gray matter on the outside and white matter on the inside. In terms of function, the cerebellum and cerebral cortex work together to control the movement of muscles to regulate posture and body balance.
The forebrain belongs to the highest part of the brain and is the most complex and important nerve center in the human brain. The forebrain is divided into four parts: the visual thalamus, hypothalamus, limbic system, and cerebral cortex.
Extended information The phenomenon that the human left cerebral cortex is dominant in language activity is related to certain genetic factors, but it is mainly formed gradually in life practice, which is closely related to the human habit of using the right hand for labor.
Because the left hemisphere is dominant in language activity, the left hemisphere is generally called the dominant hemisphere or primary hemisphere, and the right hemisphere is the secondary hemisphere. But studies have pointed out that the right hemisphere also has its own special and important functions. Reference: Baidu Encyclopedia - Human Brain.
Find the distribution map of human lumbar nerves, it is best to have the number of lumbar vertebrae and the names of the corresponding nerves. (Just like in the book) It's okay if you have a camera to take pictures
The positioning diagnosis of lumbar disc herniation is based on the understanding of medical history and careful physical examination, not only the diagnosis opinion of lumbar disc herniation can be made, but also the positioning diagnosis can be basically made. This is mainly based on the characteristic symptoms and signs produced by different nerve roots under the compression of herniated disc tissue.
Since more than 95% of lumbar disc herniation occurs in the L4, L5 or L5S1 intervertebral space, which compresses the L5 or S1 nerve root, it mainly manifests as sciatica symptoms. Another 1% to 2% of lumbar disc herniation occurs in the intervertebral space between L3 and 4, compressing the L4 nerve root and causing femoral nerve symptoms.
Disc herniation at L1, 2 and L2, 3 with symptoms of obturator or femoral nerve involvement. (T: represents the human thoracic spine; L: represents the human lumbar spine; S: represents the human sacral spine) 1. T12L1 intervertebral disc herniation, L1 nerve root compression, pain in the groin area or anterolateral thigh.
Numbness, hypoalgesia, inversion of the lower abdominal wall, or diminished or absent cremasteric reflex may occur in this area. 2. L1, 2 intervertebral disc herniation, L2 nerve root compression, pain on the outer side of the thigh or anterolateral side. You can also feel pain in the proximal end of the anteromedial thigh, with decreased sensation in the same area.
Numbness or loss of sensation occurs when nerve roots are severely affected. Hip flexor strength weakened to varying degrees, adductor reflex weakened.
3. L2, L3 intervertebral disc herniation and L3 nerve root compression, pain in the anterior inner thigh, a few cases of knee pain in the groin area, numbness in the inner knee, and numbness in the anterior inner thigh when the nerve is seriously involved. The adductor or quadriceps strength is weakened to varying degrees, and the adductor reflex is weakened.
4. L3, 4 intervertebral disc herniation and L4 nerve root compression. Pain in the lower back, hip, outer thigh, and front calf. Numbness in the anteromedial part of the calf, weakness of the quadriceps, and weakened or absent knee reflexes. 5. L4, L5 intervertebral disc herniation and L5 nerve root compression.
Low back pain, sacroiliac pain, hip pain, pain radiating down to the posterolateral thigh and calf. Numbness on the outside of the calf or including the big toe and dorsum of the foot, and occasionally foot drop. Knee and ankle jerks were generally unchanged.
6. L5S1 intervertebral disc herniation, S1 nerve root compression, low back pain, sacroiliac pain, hip pain, pain radiating down to the thigh, calf posterolateral and heel pain. Numbness of the posterolateral aspect of the calf and the dorsum of the foot including the outer 3 toes. Weakened muscle strength is rare. If there is a change in muscle strength, it will manifest as plantarflexion of the foot and weakness of flexion mother.
Ankle reflexes generally diminish or disappear. 7. Central lumbar disc herniation is usually between L4 and 5 or between L5 and S1. It can also be high lumbar disc herniation that compresses the cauda equina nerve, causing low back pain, bilateral thigh and calf back pain, bilateral thigh and calf back pain Numbness in lateral, plantar and perineal areas.
Weakness or paralysis of the bladder and rectal sphincters. Ankle and anal reflexes were absent.
The structure of neurons
The basic structure of neurons is composed of dendrites, axons, myelin sheath, and nucleus. The transfer forms a current, and its tail is a receptor, which is conducted by chemical substances (chemical transmitters) (dopamine, acetylcholine), and a current conduction is formed between two synapses after an appropriate amount is transferred.
The cell body is composed of nucleus, cell membrane, and cytoplasm, and has the function of communicating and integrating input information and transmitting information. There are two types of protrusions: dendrites and axons. The dendrites are short and branched, and directly protrude from the cell body to form dendrites. Their function is to receive impulses from the axons of other neurons and transmit them to the cell body.
The axon is long and less branched, and is a slender protrusion with uniform thickness, often originating from the axon mound. Extended information: According to the functional classification of neurons, it can be divided into three categories: 1. Sensory (afferent) neurons: receive stimuli from inside and outside the body, and transmit nerve impulses to the central nervous system.
The end of neurons, some are free, and some differentiate into cells or tissues that are specialized to receive specific stimuli. Distributed throughout the body. In a reflex arc, typically connects to an interneuron.
In the simplest reflex arcs, such as the stretch reflex that maintains skeletal muscle tone, they can also directly synapse with efferent neurons in the center. 2. Motor (efferent) neurons: Nerve impulses are transmitted from the cell body through the axon to the end, causing muscle contraction or gland secretion.
The endings of the efferent nerve fibers are distributed to the skeletal muscle to form the motor end plate; when they are distributed to the visceral smooth muscle and glandular epithelium, they wrap around muscle fibers or pass between glandular cells.
In the reflex arc, the general way of connecting with interneurons is aggregation, that is, many afferent neurons form synapses with the same neuron, so that impulses from many different sources act on the same neuron simultaneously or successively. It is the integration of the central nervous system, making the response more precise and coordinated.
3. Contact (intermediate) neurons: receive nerve impulses from other neurons, and then transmit the impulses to another neuron. Interneurons are distributed in the central nervous system such as the brain and spinal cord. It is the most numerous of the three types of neurons.
Its arrangement is very complex, there are divergent, convergent, chain-like, ring and so on. The contact points for information transfer between neurons are synapses. Complex reflex activity is a chain of neurons that are connected by synapses between afferent neurons, interneurons, and efferent neurons. Reference source: Baidu Encyclopedia - Neuron.
Where is the human nervous system located?
The composition of the nervous system mainly includes the central nervous system and peripheral nervous system, as follows: 1. Central nervous system: mainly includes the cerebrum, cerebellum, brainstem, and spinal cord.
The central nervous system is the headquarters of the human body. It mainly enables people to carry out normal daily activities, as well as the movement of hands and feet, as well as functions such as normal language, thinking communication and creation; 2. Peripheral nervous system: including peripheral Nerves, neuromuscular junctions, muscles, nerve roots, nerve plexuses.
Generally distributed in the muscles and limbs, and even internal organs.
The main function of the peripheral nervous system is to allow the limbs to move correctly after receiving instructions from the brain, that is, to be able to hold chopsticks correctly, read books, write correctly, and create ideas. However, the central nervous system and the peripheral nervous system need to cooperate with each other. , Only then can the body language be unified.
Nerve tissue: composed of nerve cells and glial cells Nerve cells Nerve cells: also called neurons, about 10^12 glial cells: 10-50 times the number of neurons, supporting and protecting neurons , the role of nutrition and insulation, and also participate in the metabolism of neurotransmitters and active substances. Nissl bodies: strongly basophilic, evenly distributed, in large neurons, such as spinal motor neurons, in the form of thick plaques, in small nerves Cells, such as neurons within a ganglion, are granular.
Under the electron microscope, Nissl bodies are composed of well-developed rough endoplasmic reticulum and free ribosomes to form axons: under the light microscope, the part where the cell body emits axons is called the axon mound, and there are no Nissl bodies in this area, so the staining is lighter. Systemic glial cells Astrocytes: the largest type of glial cells, with star-shaped cell bodies Oligodendrocytes: distributed near neuron cell bodies and around axons, with fewer protrusions.
Under the electron microscope, it can be seen that most of the oligodendrocytes protruding ends expand into a flat film, wrapping the axons of neurons to form myelin, so it is the myelin-forming cell of the central nervous system Microglia: it is the smallest glial cell .
Microglia are evolved from blood mononuclear cells that migrate into the nervous tissue. When the nervous system is damaged, they can transform into macrophages, which swallow the debris of dead cells. Ependymal cells: lining the ventricles and the central canal of the spinal cord The luminal surface forms a single layer of epithelial-like ependyma.
The ependymal cells in the choroid plexus can produce the glial cells of the peripheral nervous system Schwann cells in the cerebrospinal fluid: they participate in the formation of nerve fibers in the peripheral nervous system. The Schwann cells have a basement membrane on their outer surface and can also secrete neurotrophic factors to promote Survival of injured neurons and regeneration of their axons Satellite cells: a layer of flat or cuboidal cells enclosing the neuron cell body in a ganglion cell composition.
According to whether glial cells form myelin sheath, they can be divided into myelinated nerve fibers and unmyelinated nerve fibers. Narrow, called Nodes of Ranvier Myelinated nerve fibers of the central nervous system: The structure is basically the same as the myelinated nerve fibers of the peripheral nervous system, but the cells that form the myelin sheath are oligodendrocytes.
The flat film at the end of multiple processes of oligodendrocytes can envelop multiple axons and unmyelinated nerve fibers of the peripheral nervous system: the Schwann cells are irregular long columns with varying numbers and depths of vertical lines on the surface There are thinner axons in the concave groove, and Schwann cells do not wrap them.
Therefore, a nerve fiber can contain many axons. Due to the tight junction between adjacent Schwann cells, there are no Ranvier knots.