Overview of Nervous System

Nervous system of all humans is made up of highly specialized types of cells called nerve cells. It is capable of sensing, receiving, and transmitting various types of inputs. The neural organization is much simpler in the lower invertebrates. For Example – Hydra is composed of a network of neurons. 

The neural system is organized in vertebrates. where a brain, many ganglia, and neural tissue are all present. 

Human Nervous System

The area of the human body that regulates a person’s voluntary and unconscious movements is known as the nervous system. When the neurological system notices bodily-affecting environmental changes, the endocrine system joins forces with it. They transmit messages in the form of electrical impulses and convey messages to and from the sense organs. There are two main components of the human nervous system:

• The central nervous system (CNS)
• The peripheral nervous system (PNS)
  

Central Nervous System

The portion of the nervous system that is made up mostly of the brain and spinal cord is known as the central nervous system (CNS). The CNS is the Central Processing Unit of the human body. It is a structure of nervous tissue positioned along the rostral (nose end) to caudal (tail end) axis of the body. An enlarged section at the rostral end is a brain. The Central Nervous System consists of the brain and the spinal cord.

Brain

One of the biggest and most complicated organs in the human body is the brain. Soft tissue, including grey and white matter, non-neuronal cells, and nerve cells make up the brain. The primary functioning component of the CNS is the brain. The white matter consists of axons and oligodendrocytes. White matter is found in the inner layer of the cortex. The grey matter consists of neurons and unmyelinated fibers. Grey matter creates the outermost layer of the brain and is pinkish grey in tone.

The human brain is composed of three major parts:

• Forebrain
• Midbrain 
• Hindbrain.

Brain Parts	Second Name	Location	Structure Contain
Forebrain	Prosencephalon	The anterior part of the brain	The forebrain structures consist of the cerebrum, thalamus, hypothalamus, pituitary gland,  etc.
Midbrain	Mesencephalon	The smaller and central part of the brainstem	the midbrain is the consists of the tectum, the cerebral aqueduct, the tegmentum, and the cerebral peduncles, etc
Hindbrain	Rhombencephalon	The central region of the brain	It is composed of the medulla oblongata, the pons, and the cerebellum.

 Details of Brain Parts

Forebrain  Parts

Cerebrum

The cerebrum, which is the biggest component of the brain, controls temperature as well as initiates and coordinates movement. Other regions of the brain are responsible for speaking, decision-making, reasoning, problem-solving, emotions, and learning, among other functions.

Thalamus

Vertebrate brains have a midline symmetrical structure called the thalamus. It lies halfway between the midbrain and cerebral cortex. The thalamus receives a sensory impulse that flows from the surface of the body and interprets it as a sensation.
The cerebral cortex subsequently processes this feeling and interprets it as touch, pain, or temperature.

Hypothalamus

The release of hormones from the pituitary gland is one of the numerous biological processes that the hypothalamus, a region of the brain, plays a critical role in regulating. The hypothalamus’ job is to keep your body’s internal equilibrium in check. It is referred to as homeostasis. Many essential bodily functions, such as heart rate, blood pressure, and body temperature, are stimulated or inhibited by the hypothalamus.

Pituitary Gland

Since that regulates the operations of many other endocrine glands, the pituitary gland is sometimes referred to as the “master” gland of the endocrine system. At the base of the brain, the pituitary gland, which is no bigger than a pea, is situated.

Midbrain Parts

Tectum

The part of the mesencephalon, or midbrain, that lies between the forebrain and the hindbrain is known as the tectum. The auditory and visual impulses are controlled by the tectum of the midbrain. It originates from the alar plate of the neural tube during embryonic development.

Cerebral Aqueduct

The cerebral aqueduct is the structure within the brainstem that connects the third ventricle to the fourth. It is located within the midbrain, surrounded by periaqueductal grey matter (PAG) with the tectum of the midbrain located posteriorly and the tegmentum anteriorly.

Tegmentum

A general region of the brainstem is called the tegmentum. The ventral region of the midbrain is known as the tegmentum. This highly diverse and integrative area contains a network of nuclei responsible for many vital functions including arousal, consciousness, sleep-wake cycles, etc.

Hindbrain Parts

Medulla Oblongata

The bottom portion of the brainstem is made up of a long stem-like structure called the medulla oblongata, or just the medulla. Signals between the spinal cord and the higher regions of the brain must travel through the medulla oblongata, which is essential. 

Pons

The pons enables the communication between the left and right hemispheres of the brain regarding the senses. All muscle function other than eye movement may be lost if the pons is destroyed.

Cerebellum

The region of the brain located behind the brain stem and between it and the cerebrum. The cerebellum regulates balance for standing and walking as well as other intricate motor activities.

Spinal Cord

A lengthy bundle of nerves and cells called the spinal cord runs from the lowest part of the brain to the lower back. It relays messages from the brain to the rest of the body. The spinal cord serves as the body’s primary information processing system, taking data from the brain and transmitting it to a network of branching nerves that connect to every other part of the body. There are 31 pairs in humans, including 8 cervical, 12 thoracics, 5 lumbar, 5 sacral, and 1 coccygeal. Each pair links the spinal cord to a particular area of the body.

Organ	Function
Motor	directs your body’s voluntary muscle movements.
Sensory	monitors sensation of touch, pressure, temperature and pain
Autonomic	regulates digestion, urination, body temperature, heart rate, and dilation/contraction of blood vessels

The spinal cord relays information up to the brain through spinal tracts through the final common pathway to the thalamus and ultimately to the cortex.

Peripheral Nervous System

The nerves and ganglia that are located outside the brain and spinal cord make up the peripheral nervous system (PNS), one of the two parts that make up the nervous system. The portion of the nervous system that is made up of all the nerves that are external to the central nervous system is called the peripheral nervous system (PNS). The CNS and the body components are connected through a network of nerves.

Afferent Neurons

Afferent neurons, also called sensory neurons, are the nerve fibers responsible for bringing sensory information from the outside world into the brain.

Efferent Neurons

Efferent neurons, also called motor neurons, are the nerve fibers responsible for carrying signals from the brain to the peripheral nervous system in order to initiate an action

The peripheral nervous system is divided into two parts

1. Somatic Nervous System

2. Autonomous Nervous System

Somatic Nervous System

All of the body’s voluntary muscle systems and the process of voluntary stretch reflex are under the control of the somatic nervous system. The voluntary control of body movements by skeletal muscles is a function of the somatic nervous system. Both efferent (motor) and afferent (sensory) nerves make up the somatic nervous system.

Types Of Somatic  Nervous System

Thus the somatic nervous system consists of two parts: 

• Spinal nerves : They are mixed nerves that carry sensory information into and motor commands out of the spinal cord. 
• Cranial nerves : They are the nerve fibers that carry information into and out of the brain stem.

Autonomous Nervous System

The autonomic nervous system (ANS),  referred to as the vegetative nervous system, is that supplies smooth muscle and glands, and internal organs. A regulatory system that regulates biological functions primarily involuntarily is called the autonomic nervous system. as the pulse, digestion, breathing, pupil response, urination, and level of sexual arousal

Types of  Autonomous Nervous System

There are three branches to the ANS

• The sympathetic nervous system, 
• The parasympathetic nervous system
• The enteric nervous system.

Sympathetic Nervous System

The sympathetic nervous system’s primary process is to stimulate the body’s fight or flight response The sympathetic nervous system directs the body’s rapid involuntary response to dangerous or stressful situations. The sympathetic nervous system can accelerate heart rate, widen bronchial passages, decrease motility of the large intestine, constrict blood vessels, etc. The body’s attentiveness and heart rate are increased by a sudden rise of hormones, which increases the flow of blood to the muscles. The hypothalamus sends signals to the adrenal glands via the autonomic nervous system to activate the sympathetic nervous system.

Parasympathetic Nervous System

The parasympathetic nervous system is in charge of activating “rest-and-digest” or “feed-and-breed” processes that take place when the body is at rest. The parasympathetic nerve system speeds up digestion while slowing down breathing and heart rate.
The ANS’s craniosacral division is another name for the parasympathetic nervous system. The brain and the sacral region of the spinal cord contain the parts of its central nervous system.

Enteric Nervous System

The enteric nervous system (ENS) or intrinsic nervous system is one of the main divisions of the autonomic nervous system (ANS). It consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract.  The ENS is also called the second brain. It is derived from neural crest cells. The enteric nervous system is capable of operating independently of the brain and spinal cord

Neurons

A Neuron is a structural and functional unit of the nervous system. A neuron or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. A neuron is a microscopic structure composed of three major parts namely

• Cell Body
• Dendrites
• Axon