What is the Nervous System?

What is the Nervous System?

The nervous system is a network of cells made by the central neurons. The nerves are made to transmit signals from neuron to neuron. Nerves are made in pairs. They are called ‘dense’, ‘sparse’, ‘mixed’, or other types.

These pairs are-

1) Dense – Spinal cord

2) Sparse – Cranial nerves

3) Mixed nerves – Visceral Cords & plexuses & autonomic ganglia (plexuses).

4 ) Autonomic ganglia.

5 ) Somatic sensory and motor nerve fibers. These spinal cords consist of two sets of paired bundles of axons, one set for afferent sensation and another for efferent volition. These fibers that go from the posterior to the anterior are called sensory or afferent fibers and those that go from anterior to posterior are called efferent fibers. The nerve fiber bundles run in the white matter of the cord, while neuronal cell bodies lie within its gray matter.

These cells originate from neuroblasts, which migrate in a chain alongside the spinal nerves. As they protrude through the opening to become a part of a peripheral nervous system, their axons separate from one another and come together to form all sensory nerve roots for dorsal parts of the body except the cardiac plexus which is formed by autonomic neurons whose axons don’t have a myelin sheath.

Types of the nervous system:

1. central nervous system

2. peripheral nervous system

3. autonomic nervous system

4. neural network

5. nervous tissue

6. brain stem

7. spinal cord anatomy and physiology, part 1: functions of the spinal cord and brainstem during sleep; physiological states; dreaming; pain; movements (facial expressions, breathing); consciousness (awake and asleep)–this is good for people looking for definitions to terms like “sleep center” or other things that aren’t commonly used by doctors who don’t study dream psychology/physiology eg: neural correlates of the experience of flow in the dreaming-this paper includes a helpful diagram that shows what happens to all parts of the brain while you dream.

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it shows that all parts of the brain are active while dreaming from information from EEGs, but only certain areas have enough activity for people to report having a vivid dream of being able to remember their dreams on waking up. surprisingly, although there is an abundance of vivid dreaming in the REM stage, there is no more rapid eye movement than during non-REM sleep stages.

what is the function of the nervous system:

1. neural control of movement

2. sensory input from the environment and motor output to the environment

3. regulation of internal body function via hormonal effectors

4. storage and retrieval of information

5. integration of a multitude of complex signals into a single cohesive response

6. generation of coherent patterns of electrical impulses, with precise spatial and temporal coordination between different regions

peripheral nervous system:

the peripheral nervous system is a vast network of nerves that connect the central nervous system to every other part of your body, including your skin, sensory organs ( eyes, ears, tongue ), and muscles.

Autonomic nervous system:

the autonomic nervous system regulates involuntary actions such as breathing and heartbeat. it does this by splitting into two divisions:  the sympathetic division which promotes arousal or fight-or-flight reactions; and the parasympathetic division which inhibits these reactions.

neural network:

in computer science, artificial neural networks (ANN) are systems of interconnected ‘neurons’ loosely based on the way biological nervous systems function.

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nerve tissue:

nerve tissue is made up of neurons and glial cells. glial cells provide support for the neurons in many different ways, including providing nutrients to them via blood vessels (the process known as neurogenesis) and maintaining homeostasis by taking away excess neurotransmitter molecules. glia limits the amount of stimulus that reaches a neuron; without this self-regulatory mechanism, any signal would cause an uncontrolled firing of the neuron.

nervous system anatomy:

the nervous system is a network of cells called neurons that relay information to the brain and spinal cord.

nervous tissue:

nerve tissue is made up of neurons and glial cells. glial cells provide support for the neurons in many different ways, including providing nutrients to them via blood vessels (the process known as neurogenesis) and maintaining homeostasis by taking away excess neurotransmitter molecules. glia limits the amount of stimulus that reaches a neuron; without this self-regulatory mechanism, any signal would cause an uncontrolled firing of the neuron.

information processing:

the nervous system processes both sensory and motor information. the former is used to detect changes in your environment and then respond to them; the latter is used to move and position your body and other objects (such as tools) in the world around you.

how does the nervous system work:

the nervous system consists of a series of tiny nerve cells known as neurons. it is through this network that messages are sent from your brain to your muscles and organs, telling them what to do.

a neuron:

a neuron is an electrically excitable cell found in the bodies of all living organisms from simple animals to complex human beings. a cell has four main parts: a nucleus, cytoplasm, mitochondria, and an axon.

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axons:

the axon is a long wire-like structure that transmits electrical impulses away from the cell body or soma. neurons have multiple dendrites extending from their soma into which other neurons’ axons terminate; such connections between neurons form neural pathways.

soma:

the body of a neuron, containing the nucleus and cytoplasm. dendrites emerge from the soma; they are short branching extensions that receive signals from other neurons.

dendrites:

the cell body (or soma) of a neuron is typically about 1mm long and contains most of the organelles including mitochondria, endoplasmic reticulum, ribosomes, etc; it also contains the nucleus where genetic information is stored in DNA molecules made up of nucleotides (e.g. adenine (A), cytosine (C), guanine (G) and thymine (T)). axons extend away from the cell body and carry the nerve impulse away from the neuron toward a synapse or terminal buttons.

myelin sheath:

A myelin sheath, also known as a myelin membrane, is a layer of glial cells that surround some neurons in order to form an insulating substance that increases the velocity at which signals are transmitted along an axon.

nervous tissue structures:

nerve tissue is made up of neurons and glial cells. glial cells provide support for the neurons in many different ways, including providing nutrients to them via blood vessels (the process known as neurogenesis) and maintaining homeostasis by taking away excess neurotransmitter molecules. glia limits the amount of stimulus that reaches a neuron; without this self-regulatory mechanism, any signal would cause an uncontrolled firing of the neuron.

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