Glimpse of Original …..
Remember the text-book’s diagram of Nervous System? Well another example of “My life is a LIE!”.
Anatomy of human brain, the REAL ONE!
- Central Nervous System
- Periferic Nervous System
- Somantic Nervous System
- Autonomous Nervous System
- Enteric Nervous System
The Building Blocks ….
Neuron is an electrically excitable biological cell that processes and transmits information through electrical and chemical signals.
What are They Made of …..
- Signals between neurons occur via specialised connections called synapses
- Axons are long slender projection of a nerve cell that conducts nerve impulses away from the cell body to other neurons, muscles, and organs
- Dendrites are branched projections of a neuron that conduct the impulses received from other neural cells to the cell body
- Soma or ‘cell body’ is the bulbous, non-process portion of a neuron or other brain cell type, containing the cell nucleus
- Myelin is a fatty white substance that surrounds the axon of some nerve cells, forming an electrically insulating layer for the proper functioning of the nervous system
Flavours of Building Blocks …..
How One treats the others …..
Pre-synaptic neuron is a nerve cell that fires the neurotransmitter (signalling molecules) as a result of an action potential entering its axon terminal.
Post-synaptic neuron in a nerve cell that receives the neurotransmitter after it has crossed the synapse and may experience an action potential if the neurotransmitter is strong enough.
Postsynaptic neurons work through temporal summation and spatial summation:
- Spatial Summation: When more than one signal is originated in same neuron, instead of being fired separately, they are summed up and then fired.
- Temporal summation: If two incoming signals overlap, then they are summed up. If sub-threshold signal reaches, then no action will be generated but if multiple sub-threshold reach neuron’s trigger zone, a suprathreshold signal with action potential might be generated.
What One is meant to do …..
What role they perform is defined by parts they bridge:
- Afferent neurons convey information from tissues and organs into the central nervous system and are also called sensory neurons.
- Efferent neurons transmit signals from the central nervous system to the effector cells and are also called motor neurons.
- Interneurons neurons, which are found only in the CNS, connect one neuron to another. They receive information from other neurons (either sensory neurons or interneurons) and transmit information to other neurons (either motor neurons or interneurons).
What about Polarity …..
Most neurons can be anatomically characterised as:
- Unipolar: dendrite and axon emerging from same process.
- Bipolar: axons and single dendrite on opposite ends of the soma.
- Multipolar: two or more dendrites, separate from the axon.
- Anaxonic: where axon cannot be distinguished from dendrites.
Central Nervous System …..
The central nervous system (CNS) is the part of the nervous system consisting of the brain and spinal cord.
It integrates information from, and coordinates and influences the activity of all parts of the body.
CNS is composed of large numbers of nerve cells, called neurons, which are supported by specialised tissue called neuroglia.
The interior of the central nervous system is organised into gray and white matter.
- Gray matter consists of nerve cells embedded in neuroglia; it has a gray color.
- White matter consists of nerve fibers embedded in neuroglia; it has a white color.
The brain plays a central role in the control of most bodily functions, including awareness, movements, sensations, thoughts, speech, and memory. Some reflex movements can occur via spinal cord pathways without the participation of brain structures.
The spinal cord is connected to a section of the brain called the brainstem and runs through the spinal canal. Cranial nerves exit the brainstem. Nerve roots exit the spinal cord to both sides of the body. The spinal cord carries signals (messages) back and forth between the brain and the peripheral nerves.
Peripheral Nervous System …..
The peripheral nervous system includes the cranial nerves, spinal nerves and their roots and branches, peripheral nerves, and neuromuscular junctions.
In the peripheral nervous system, bundles of nerve ﬁbers or axons conduct information to and from the central nervous system.
The autonomic nervous system is the part of the nervous system concerned with the innervation of involuntary structures, such as the heart. It is distributed throughout the central and peripheral nervous systems.
The somatic nervous system is the part of the peripheral nervous system associated with skeletal muscle voluntary control of body movements. The SoNS consists of afferent nerves or sensory nerves, and efferent nerves or motor nerves.
The Second Brain …..
Enteric nervous system is one of the main divisions of the nervous system and consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract.
It is now usually referred to as separate from the autonomic nervous system since it has its own independent reflex activity.
Remember Getting nervous before something bad happens of predicting someone is going to change the lane before they do so? Well this is due to the presence of chemical (information) super-highway called Brain-Gut Axis.
The information this axis shares is not just stored but due to presence of enormous number of neurons, ENS is also able to process this information and feed it’s own responses to our gut (hence anxiety and nausea).
In fact, ENS contains about 95% of Serotonin which affects our mood.
Our actual brain focuses on only a negligible amount of the overall data it processes. The brain has at least 10x feed-back mechanisms as it has feed-forward mechanisms. So it is able to make summaries of information it processes and some of these summaries are transferred to the ENS for releases different mood affecting chemicals if necessary.
The Mammoth …..
The brain contains more than 90% of the body’s neurons.
Satellite’s View …..
The brain has been divided into 3 different areas:
- Hindbrain is made up of cerebellum, pons, and medulla.
- Forebrain consists of thalamus, hypothalamus, and the cerebral cortex.
- Midbrain adjoins the pons and cerebellum; thalamus, hypothalamus etc.
Eagle’s View …..
The Brain is has two major parts:
- Cerebrum : The cerebrum is the largest part of the brain. The cerebrum controls voluntary actions, speech, senses, thought, and memory.
- Cerebellum : It has an important role in motor control, with cerebellar dysfunction often presenting with motor signs. In particular, it is active in the coordination, precision and timing of movements, as well as in motor learning.
Deep Dive ….
A Brodmann area is a region of the cerebral cortex, defined by its cytoarchitecture, or histological structure and organization of cells.
Nope …. not going there ….. Nope!! Instead:
The Cerebrum is further divided into regions called lobes:
- Occipital lobe receives and processes visual information
- Temporal lobe is important to the sense of smell; it also helps us perform complex visual tasks, such as recognising faces
- Parietal lobe receives sensory information, in the sensory projection areas, from all over the body and figures in spatial abilities. The ability to comprehend language is concentrated in 2 areas : parietal lobe and temporal lobe
- Frontal lobe is the part of the cerebral cortex responsible for voluntary movement and attention as well as goal-directed behaviour. The brain starts response messages in the motor projection areas, from which they proceed to the muscles and glands.