Introduction
The nervous system is a complex network of nerves and cells that transmits signals to and from the brain. In humans, the nervous system comprises two parts: the central nervous system (CNS) and the peripheral nervous system (PNS).
The CNS consists of the brain and spinal cord, while the PNS includes all other nerves outside these structures. The CNS is responsible for thinking, memory, voluntary muscle movements, sensory perception, and emotions. The PNS controls involuntary muscle movements such as breathing and digestion.
Central Nervous System (CNS)
The central nervous system comprises the brain and the spinal cord. It is responsible for controlling all voluntary and involuntary functions of the body.
The central nervous system comprises the brain and the spinal cord. The brain controls all voluntary and involuntary functions in your body, whereas the spinal cord connects your brain to all parts of your body.
Brain
The brain is the organ of the central nervous system in humans and most other vertebrates. The brain controls many essential functions such as memory, awareness, intelligence, sensation, language and problem-solving.
This section covers the basics of the human brain and how it works. The mushroom-shaped brain is housed within the skull. The brain is divided into four sections:
- Brain stem
- Cerebrum
- Cerebellum
- Diencephalon
The weight of the brain is somewhere between 1.3 and 1.4 kgs. It consists of nerve cells known as neurons and supporting cells known as glia.
Grey matter in the brain tissue comprises neurons and other cells. White matter is the brain tissue that consists primarily of axons, which are long, slender nerve fibres.
White matter carries signals between different parts of the brain or between the brain and other body parts. Grey matter does not move calls from one part of the brain to another but instead processes information from sensory input or sends instructions to muscles.
Brainstem
The brainstem, also known as the Medulla oblongata, is the lower part of the brain. It sits between the cerebrum and the spinal cord and is sometimes called the hindbrain. The brainstem controls breathing, heart rate, and other essential functions.
The most important job of the brain stem in the nervous system in humans is to control essential functions like breathing and heart rate. It also connects to many parts of your body, telling them what to do.
Cerebrum
The cerebrum is the most significant part of the brain, and it is also the most developed. It consists of two hemispheres joined by a large bundle of nerve fibres called the corpus callosum. The cerebrum controls all voluntary actions, thoughts, and feelings.
The cerebrum is divided into two hemispheres. The left hemisphere controls logical reasoning, speech, and language comprehension. The right hemisphere controls creativity, spatial skills, and facial recognition.
Each hemisphere is further divided into:
- Frontal lobe
- Temporal lobes
- Parietal lobe
- Occipital lobe
Diencephalon
The diencephalon is a part of the brain located in the middle of the brainstem. It controls many bodily functions, such as breathing, heart rate, and digestion.
The diencephalon is a part of the brain located in the middle of the brainstem. It controls many bodily functions, such as breathing, heart rate, and digestion.
The diencephalon consists of two primary structures: The thalamus and the hypothalamus. The thalamus regulates sensations from all parts of our body except for taste and smell. It also helps us sleep by sending messages to our body when it needs to slow down or rest. The hypothalamus regulates our body temperature and water intake through urination by sensing changes in our environment with its receptors on our skin.
Spinal Cord
The spinal cord is the bundle of nerves that connects the brain to the rest of the body in the nervous system in humans. It is made up of nerve cells, which are called neurons.
The spinal cord comprises 31 segments and is shaped like a tube. It starts at the base of your brain and ends at your pelvis. The spinal cord contains bundles of nerves that carry messages between your brain and all parts of your body, except for your head.
Adult women’s spinal cords are 43 cm long, whereas adult men’s spinal cords are 45 cm long and weigh 35-40 grams. It is found within the vertebral column (backbone).
Meninges
The meninges are three layers of tissue that cover and protect the brain. The outermost layer is tough, white, and fibrous. It is called the dura mater. The middle layer is a thin, elastic membrane called the arachnoid membrane or arachnoid mater. The innermost layer is a delicate sheet of tissue called the pia mater or pia maters.
Cerebrospinal Fluid (CSF)
Cerebrospinal fluid is a clear, colourless body fluid that circulates in the brain and spinal cord. It helps protect the brain and spinal cord from injury by acting as a cushion.
The CSF is produced in the choroid plexuses of the brain’s ventricles. The CSF flows through these cavities, bathes the brain and spinal cord, and then passes out through openings called cerebral aqueducts into larger spaces called subarachnoid space.
Neurons
Neurons are cells found in the brain of the nervous system in humans. They are responsible for sending messages to other cells. A neuron has three parts: the cell body, dendrites, and axon. The cell body contains the nucleus and cytoplasm, which stores proteins and organelles needed to function correctly.
Dendrites extend from the cell body and act as antennae, receiving messages from other neurons. Axons are long fibres that extend out of the cell body and send messages to other neurons.
Peripheral Nervous System (PNS)
The peripheral nervous system is a part of the nervous system in humans that is not located in the brain or the spinal cord. It has two parts:
Somatic Nervous System
The somatic nervous system is one of the two divisions of the autonomic nervous system. The somatic nervous system is responsible for voluntary muscle control, except those that control eye muscles.
The somatic nervous system consists of sensory neurons, motor neurons, and interneurons. Sensory neurons are activated by stimuli in the environment, such as touch or pressure.
Signals activate motor neurons from the brain and spinal cord to control muscle movement. Interneurons are found between sensory and motor neurons to simultaneously send alerts to one another or both types of neurons.
Autonomic Nervous System
The autonomic nervous system (ANS) is the part of the peripheral nervous system in humans that controls involuntary actions.
It regulates heart rate, digestion, breathing, and other functions. The ANS comprises the sympathetic nervous system and the parasympathetic nervous system.
The sympathetic nervous system is responsible for activating responses to emergencies. It boosts blood pressure and heart rate, increases respiration, and constricts blood vessels to provide more oxygen to muscles during periods of intense physical activity.
The parasympathetic nervous system slows down these responses to return the body to its resting
state.
Conclusion
In humans, the nervous system is a complex network of cells that transmit information from one part of the body to another. It also controls the body’s movements and senses.
The nervous system comprises two main parts: the central nervous system and the peripheral nervous system. The central nervous system consists of the brain and spinal cord, while the peripheral nervous system consists of all other nerves that branch out from these two structures.