Lesson Video: The Central Nervous System | Nagwa Lesson Video: The Central Nervous System | Nagwa

Lesson Video: The Central Nervous System Biology

In this video, we will learn how to describe the structure and function of the different parts of the central nervous system.

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Video Transcript

In this video, we’ll learn how to describe the structure and function of the different parts of the central nervous system. We’ll start by learning to describe the different divisions of the brain, including the three membranes that surround and protect the brain and spinal cord. Then, we’ll explore the basic structure of the brain divisions, how to identify the different lobes of the cerebrum, and discuss the different function of each of these brain divisions. We will also outline the components of the spinal cord and learn to identify the structures of the spinal cord when shown in cross section. Finally, we’ll briefly discuss how the structure of the spinal cord supports the transmission of nerve impulses to and from the brain.

The human nervous system has three main functions: gathering sensory information, processing the gathered sensory information, and coordinating a motor response to the process sensory information. The central nervous system, or CNS, is a part of the human nervous system that is responsible for receiving sensory information, processing sensory information, and coordinating an appropriate motor response. To carry out all of these actions, the CNS uses its two major components, the brain and the spinal cord.

Since the brain and spinal cord perform some of the most critical functions of our bodies, they are heavily protected. The first layer of protection for the brain and spinal cord are the bones that encase these two structures. The brain is surrounded by the skull, whereas the spinal cord is surrounded by many small bones called the vertebrae. Underneath the bone, there are three more layers of protection in the form of membranes called the meninges. These three membranes each have a specific function and name. The outermost membrane that lines the bones is called the dura mater. Dura mater is Latin for tough mother and helps describe the texture of this membrane, which is very thick and durable.

Underneath the dura mater is the arachnoid mater. If the word “arachnoid” reminds you of spiders and cobwebs, great catch! The term is derived from the Greek word for spider. The arachnoid mater gets its name because it has the consistency and appearance of a spider web. And much like a spider web, while it is thin, it’s very strong and able to stabilize the movement of the brain within our skull.

The membrane closest to the brain and spinal cord is called the pia mater. Pia mater is Latin for tender mother. This is meant to describe the delicate structure of this membrane. However, while delicate, the pia mater adheres tightly to the surface of the brain and spinal cord like a plastic wrap. This forms a resistant barrier around these structures, making it difficult for foreign bodies to act upon the brain and spinal cord.

Now that we know how the brain and spinal cord are protected from physical damage, let’s take a look at each component of the CNS in detail, starting with the brain. From a developmental perspective, the brain has three divisions, the forebrain, the midbrain, and the hindbrain. Each of these divisions contains multiple parts. The forebrain is mainly composed of the cerebrum and deeper brain structures like the thalamus and the hypothalamus. The midbrain is the smallest of the three brain divisions and is mainly composed of the tectum, the cerebral aqueduct, the tegmentum, and the cerebral peduncles. The hindbrain, which is the lowest of the three brain divisions, has three main parts: the pons, the cerebellum, and the medulla oblongata.

Let’s take a deeper dive into the function of the different brain components found within the forebrain, midbrain, and the hindbrain. The forebrain is the largest and most developed part of the human brain. And as mentioned, the forebrain consists primarily of the cerebrum and deeper brain structures, including the thalamus, hypothalamus, hippocampus, optic nerves, and the olfactory bulb. These structures of the forebrain are responsible for reasoning, memory, language, sensory perception, and emotional responses.

The cerebrum comprises the bulk of the forebrain and is split into two halves or hemispheres. The hemispheres communicate and transmit information to one another through a thick track of nerve fibers. The outermost layer of the cerebrum is called the cerebral cortex and is easily identified by its characteristic wrinkled appearance. The term “cortex” is derived from the Latin term for bark, which helps describe this thick piece of tissue that comprises the cerebral cortex.

The wrinkled appearance of the cerebral cortex is created by folds in the brain tissue. These folds help increase the surface area of the brain, which allows for a greater number of neurons to fit within the skull. Therefore, the more folds or wrinkles there are in the brain, the greater number of neurons and the higher intelligence of the animal. And the largest wrinkles are used as landmarks to help researchers distinguish the four distinct sections of the cerebrum.

Each hemisphere of the cerebrum has four lobes: a frontal lobe, a parietal lobe, an occipital lobe, and a temporal lobe. The frontal lobes are important for managing higher level cognitive functions that support our ability to achieve a goal. These functions cover a wide range of actions, such as the control of voluntary movements, language production, decision-making, reasoning, and memory formation. So when you plan a schedule, pay attention to instructions, imagine the future, hold two different ideas in your mind, or use reasoned arguments, it’s the frontal lobe in action.

The parietal lobe contains a somatosensory map of the body. So the lobes are critically important for integrating sensory information and using that information to move us through space. These two functions are called somatosensation and proprioception. Somatosensation uses areas of the parietal lobe to process touch sensations like pressure, pain, and temperature. This helps us understand what sensory information we are encountering. Proprioception uses areas of the parietal lobe to sense the orientation and location of our body parts. This helps us understand where our bodies are located in space.

The occipital lobe is the visual processing center of the human brain. It contains the visual cortex, which processes information from the eyes and interprets this information into images that create our perception of the world. These lobes also contain the visual receiving and association areas, which process visual images of language, making them critical for reading and comprehension. So whenever you can recognize the words of another language but have difficulty understanding them, you’re only using the visual receiving areas of the occipital lobe.

The temporal lobes are dedicated to processing auditory information, memory, and emotion. A large portion of the temporal lobes contain the auditory cortex, which supports auditory perception and processing. This helps us not only understand what we’re hearing when it comes to speech and emotions, but it also helps us appreciate complex sounds like music. The temporal lobes are also specifically responsible for supporting the retention of visual memories and integrating them with sensations of taste, sound, sight, and touch. Finally, the inner middle portion of the temporal lobes contain the hippocampus and the amygdala, which are crucial for memory formation and emotional processing.

The forebrain also contains a fifth lobe called the insula. These lobes are best visualized if looking at the brain in cross section as the insula is hidden beneath the four other lobes of the cerebrum. The insula acts as a sort of receiving zone that reads the state of the entire body and generates feelings that can bring about actions like eating or decision-making. It also contains the gustatory complex, which is responsible for our perception of taste.

Now that we’re well acquainted with the forebrain, let’s discuss the midbrain. The midbrain is the smallest of the three brain divisions and is located at the topmost part of the brain stem. As a part of the brain stem, it helps connect the brain and the spinal cord. As mentioned, the structures found within the midbrain include the tectum, the cerebral aqueduct, the tegmentum, and the cerebral peduncles.

Since the primary role of the midbrain is to act as a sort of relay station, these structures contain important centers for many of the functions of the midbrain, functions such as relaying visual and auditory information, contributing to reflexes, supporting motor control, as well as contributing to sleeping, waking, alertness, and temperature regulation. The diversity of functions supported by the midbrain helps the central nervous system in calculating responses to sensory information, changes in the environment, as well as carrying out actions that do not require conscious awareness, like coughing or startling upon hearing a large sudden sound.

Beneath the midbrain is the hindbrain, which is the lowest brain division and comprises the lower structures of the brain stem. Structures of the hindbrain include the pons, the cerebellum, and the medulla oblongata. Together, these structures support and coordinate functions that are crucial to human survival.

The word “pons” is derived from the Latin term for bridge, which helps to describe one of the major roles of the structures, that is, to connect the midbrain to the medulla. Other functions of the pons include serving as an origin point for four out of 12 cranial nerves and supporting involuntary actions like the intensity and frequency of breathing.

The word “cerebellum” is derived from the Latin term for little brain. This describes how this small, dense, coral-shaped structure contains more neurons than both hemispheres of the cerebrum. The large number of neurons found within the cerebellum form an important hub that processes all of the information arriving to the brain and all of the commands going out of the brain. This enables the cerebellum to optimize the brain’s abilities and coordinate our voluntary movements to make them smooth, precise, and perfectly timed. The large number of neurons within the cerebellum also helps to interpret and process the brain’s intentions.

At the bottom of the brain stem is the medulla oblongata. The medulla oblongata is important for our survival because it contains all of the control centers for our autonomic and involuntary functions like heart rate and blood pressure.

Beneath the hindbrain is the second organ of the central nervous system, the spinal cord. The spinal cord is a thick bundle of nerve fibers and nervous tissue that creates a two-way pathway between the brain and the body. The spinal cord is divided into four regions: the cervical region, the thoracic region, the lumbar region, and the sacral region. These regions contain 31 segments with 31 pairs of spinal nerves. Each region has a slightly different set of spinal nerves. For example, there are eight cervical spinal nerves, 12 thoracic spinal nerves, five lumbar spinal nerves, and six sacral spinal nerves. Each of the 31 segments of the spinal cord has roughly the same internal structure, which can be best visualized when looking at the spinal cord in cross section.

When looking at the spinal cord in cross section, there’s a distinctive letter H shape found at its core. The H shape is typically gray in color, which is derived from the high concentration of neuron cell bodies that make up the thick bundle of nerve fibers found in the spinal cord. The gray matter core is surrounded by white matter, which is comprised of myelinated neuron axons. The meylin found on these axons is what gives the adjacent space a whitish color.

This structure of the spinal cord supports the flow of nerve impulses from the brain to the body and from the body to the brain. Sensory information is carried by the sensory neurons, traveling from the periphery to the spinal cord through the dorsal root, crossing a structure called the dorsal root ganglion that hosts the cell bodies of sensory neurons. Then, sensory information travels towards the brain directly or, as shown here, towards neurons in the spinal gray matter. Once inside the spinal cord, the sensory neurons connect with relay neurons in one of the top arms of the H-shaped gray matter core, which are called the dorsal horns.

After sensory information has been processed in the brain, the brain will send a nerve impulse back out to the periphery. To reach the appropriate effector organs, the nerve impulse will travel through the ventral horn, which is one of the lower arms of the H-shaped gray matter core. This highly structured circuitry is used to transmit both voluntary commands sent from the brain as well as reflex arcs that only involve communication with the spinal cord.

Now that we’ve reviewed all the components and functions of the central nervous system, we’re ready to try a practice problem.

What is the central nervous system comprised of? (A) The brain and the spinal cord. (B) The brain and the cranial nerves. (C) The peripheral nerves in the external limbs. (D) The spine and the spinal nerves.

To answer this question, we’ll review the structure of the human nervous system, paying close attention to the components of the central nervous system. The human nervous system has three main functions. They are gathering sensory input, processing sensory input, and responding to sensory input via motor output. All of these functions are carried out by the two main parts of the human nervous system.

The two main parts of the human nervous system are the central nervous system and the peripheral nervous system. The central nervous system is comprised of the brain and the spinal cord. These two components help to process and interpret gathered sensory input as well as coordinate an appropriate motor output response. The peripheral nervous system refers to all of the nerves outside of the brain and spinal cord. These components help to gather sensory input and execute the appropriate motor output. With this information, we’re now ready to answer our question. The central nervous system is comprised of the brain and the spinal cord.

Let’s review what we’ve learned in this video. The central nervous system is comprised of the brain and the spinal cord. The brain and the spinal cord are surrounded by the meninges, which are the dura mater, the arachnoid mater, and the pia mater. The brain is divided into the forebrain, the midbrain, and the hindbrain. The four lobes of the cerebrum are the frontal, temporal, parietal, and occipital lobes. The spinal cord is divided into four regions: the cervical, thoracic, lumbar, and sacral regions.

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