A complete anatomy of Nervous system, Study notes of Anatomy

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The nervous system

Ziya Sunny, Assist.professor ,Dept.of MSN Rajiv Gandhi University of health & science, Banglore

Content

1) Neurones

2) Centeral nervous system

3) Brain

4)Spinal cord

5) Peripheral nervous system

6) Autonomic nervous system

A.)Excitability: Neurons are capable of generating and transmitting electrical impulses, known as action potentials, in response to stimuli. B.)Conductivity: Neurons can transmit electrical impulses over long distances, from the cell body down the axon to the synaptic terminals. C.)Secretion: Neurons release chemical messengers, known as neurotransmitters, into the synaptic cleft, which can activate or inhibit other neurons or target cells. D.)Plasticity: Neurons can change their structure and function in response to experience or injury, which allows for adaptation and learning. E.)Polarization: Neurons have a distinct polarity, with dendrites receiving incoming signals and the axon transmitting outgoing signals. F.)Integration: Neurons can integrate and process multiple signals from other neurons and sensory receptors to generate an appropriate output signal

 Cell bodies Cell bodies, also known as soma or perikaryon, are the main component of a neuron. They are responsible for carrying out the metabolic and regulatory functions of the neuron, including protein synthesis and energy production. The cell body contains the nucleus, which contains the genetic material of the neuron, as well as other organelles such as mitochondria, which produce energy for the cell, and ribosomes, which synthesize proteins. The dendrites and axons of the neuron extend from the cell body and allow it to communicate with other neurons and transmit signals throughout the nervous system. The size and shape of the cell body can vary depending on the type of neuron and its function within the nervous system.  Axon and Dendrites Axons and dendrites are two structures that play important roles in the nervous system. Dendrites are the short, branched extensions of a neuron that receive signals from other neurons or sensory receptors. They are covered in specialized structures called dendritic spines, which increase the surface area available for signal reception. When a dendrite receives a signal, it generates a small electrical signal that travels toward the neuron's cell body.

between neurons) and bind to receptors on the receiving neuron, triggering a new electrical impulse in that neuron. The strength and speed of nerve impulses can vary depending on a number of factors, including the diameter of the axon, the myelin sheath (a fatty insulating layer that surrounds some axons), and the presence of ion channels that allow ions to flow in and out of the neuron. The ability of neurons to generate and transmit nerve impulses is essential for many physiological processes, including movement, sensation, and thought.  Types of nerves There are three types of nerves in the human body: 1.)Sensory nerves: These nerves transmit sensory information from various parts of the body to the central nervous system (CNS), which includes the brain and spinal cord. Sensory nerves are responsible for detecting sensations such as touch, temperature, pain, and pressure. 2.)Motor nerves: These nerves transmit information from the CNS to the muscles and glands of the body, allowing for voluntary and involuntary movement and the secretion of hormones.

3.)Mixed nerves: As the name suggests, mixed nerves contain both sensory and motor fibers and are responsible for transmitting information in both directions. These nerves are the most common type of nerve in the human body and are found throughout the body.  The synapse and neurotransmitter A synapse is a junction between two neurons or between a neuron and a target cell, such as a muscle cell or a gland. At a synapse, an electrical signal (called an action potential) in the presynaptic neuron triggers the release of chemical messengers called neurotransmitters into the synaptic cleft, which is the small gap between the presynaptic and postsynaptic cells. The neurotransmitters then bind to receptors on the postsynaptic cell, leading to a change in its electrical or chemical properties.

barrier, and regulate the levels of neurotransmitters in the brain. Oligodendrocytes produce myelin, a fatty substance that forms a protective sheath around axons, which speeds up the transmission of electrical signals between neurons. Microglia are the immune cells of the nervous system, which help protect the brain and spinal cord from pathogens and other harmful substances. Ependymal cells line the ventricles of the brain and central canal of the spinal cord, producing cerebrospinal fluid, which helps cushion and protect the brain and spinal cord. In addition to their supportive roles, glial cells have been found to play a role in neural communication and information processing in the brain.  Membranes covering the brain and spinal cord (the meninges)

The membranes covering the brain and spinal cord are called the meninges. There are three layers of meninges: 1)Dura mater: This is the outermost layer and is a tough, fibrous layer that provides protection to the brain and spinal cord. It is attached to the skull and vertebrae. 2)Arachnoid mater: This is the middle layer and is a thin, web- like membrane that covers the brain and spinal cord. It contains cerebrospinal fluid, which helps cushion and protect the brain and spinal cord.

(CSF). CSF is a clear, colorless fluid that surrounds the brain and spinal cord, providing cushioning and protection against injury. The ventricles are numbered from 1 to 4 and are located deep within the brain. The first and second ventricles are located in the cerebral hemispheres, while the third and fourth ventricles are located in the brainstem. CSF is produced by specialized cells within the ventricles called choroid plexuses. It flows through the ventricles and then into the subarachnoid space, a space that surrounds the brain and spinal cord. CSF is then absorbed back into the bloodstream. The ventricles and CSF play important roles in maintaining the health and function of the brain. They help to regulate pressure within the brain, remove waste products, and deliver nutrients and oxygen to brain cells. Dysfunction of the ventricles or CSF can lead to various neurological disorders such as hydrocephalus, a condition in which there is an excessive accumulation of CSF in the brain.

3)The Brain

The human brain is a complex organ that is responsible for controlling and coordinating all the functions of the body. It is made up of nerve cells, called neurons, that communicate with each other through electrical and chemical signals. The brain is divided into several regions, each with a specific function. The cerebrum, or cortex, is the largest part of the brain and is responsible for conscious thought, reasoning, and voluntary movement. The cerebellum is located underneath

memory, language, perception, thought, and voluntary movement. It is divided into two hemispheres, the left and right, which are connected by a thick band of nerve fibers called the corpus callosum. The cerebrum is further divided into four lobes: the frontal, parietal, temporal, and occipital lobes. Each lobe has its own specific functions. For example, the frontal lobe is responsible for decision making, problem solving, and voluntary movement; the parietal lobe is involved in sensory processing and spatial awareness; the temporal lobe plays a key role in memory and hearing; and the occipital lobe is responsible for visual processing. The cerebrum is also responsible for higher cognitive functions such as language, abstract thinking, and creativity. 2 Midbrain

The midbrain is a small region of the brain that is located between the hindbrain and the forebrain. It is an important part of the brainstem, which is responsible for regulating a number of vital functions such as heart rate, breathing, and digestion. The midbrain contains several important structures, including the tectum, which is responsible for processing visual and auditory information, and the tegmentum, which is involved in movement and sensation. Another important structure located in the midbrain is the substantia nigra, which is involved in the production of dopamine, a neurotransmitter that is important for movement and reward. 3.Pons

motor movements, balance, and posture. The cerebellum receives sensory information from various parts of the body and integrates this information with motor commands from the brain to help control and refine movements. The cerebellum is composed of three distinct layers of cells, which are organized into a highly organized structure called the cerebellar cortex. The cerebellar cortex contains millions of small, densely packed cells called Purkinje cells, which are the primary output cells of the cerebellum. The Purkinje cells project their axons to various parts of the brain, including the brainstem and spinal cord, to control motor movements.  Blood supply to the brain The brain is one of the most important organs in the body, and it requires a constant supply of oxygen and nutrients to function properly. This is achieved through a complex system of blood vessels that deliver blood to the brain.

The blood supply to the brain is provided by two main arteries: the left and right internal carotid arteries and the left and right vertebral arteries. These arteries join together to form the Circle of Willis, which is a ring-shaped structure that provides blood flow to the brain.

4. Spinal Cord