The nervous system controls mental and physical activities, whether they are voluntary or involuntary. The nervous system sends electrical signals around the body, allowing the body to react to its surroundings quickly. Without the nervous system, we would not be able to function normally. The ability of the nervous system to monitor and respond to the surrounding depends on the transmission of signals from one neuron to the next and within the neuron itself.
Nervous System: The organ system that carries electrical messages throughout the body.
Central Nervous System (CNS): Includes the brain and spinal cord.
Peripheral Nervous System (PNS): Nerves that connect all parts of the body to the brain.
Nerve: A cable-like bundles of axons that make up the peripheral nervous system.
Autonomic Nervous System (ANS): Controls all involuntary activities not under conscious control like breathing.
Somatic Nervous System (SNS): Controls voluntary activities that are under conscious control.
Neuron: The structural and functional units of the nervous system. Consists of three parts:
Cell Body: Contains the nucleus and other cell organelles.
Dendrite: Extends from the cell body and receives nerve impulses from other neurons.
Axon: An extension of the cell body that transmits nerve impulses to other cells.
Myelin Sheath: Outer layer of the axon that serves as an insulator for the axon. There are gaps on the myelin sheath that allow the electrical signal to move along the axon quickly.
Glial Cells: Support neurons and produce myelin
Nerve Impulse: Electrical signal transmitted by a neuron.
Synapse: Where an axon terminal meets another neuron cell.
Neurotransmitter: Chemical that transmits signals across synapses from the axon terminal of one neuron to the dentrites of the next neuron.
The nervous system is divided into two parts:
2. Peripheral nervous system(PNS): All the neurons and sensory organs in the body not included in the central nervous system.
The motor system can be divided into:
The brain has three major parts:
1. Cerebrum: the main part of the brain, divided into
4 lobes, controlling conscious functions:
2. Cerebellum: Controls body movement
3. Brain stem: The lowest part of the brain that connects the brain to the spinal cord, sending nerve impulses between the two. It also controls unconscious functions, including the heart rate and breathing.
Nervous tissues consist of neurons and glial cells. Neurons transmit electrical signals called nerve impulses.
Nerve impulses occur when there is a change in electrical charge across the membrane of a neuron.
Neurons communicate with each other at synapses. Types of synapses:
Sensory receptors are special cells on every sense organ (eyes, ears, mouth, nose, and skin) that respond to a particular stimulus. Upon noticing a stimulus, the sensory receptors send nerve impulses to sensory nerves that then carry the nerve impulses to the brain to be interpreted.
Light passes through the eye, which senses light, by passing through the cornea, pupil, lens, and then the retina, which contains receptor cells. These receptor cells send nerve impulses to sensory nerves that then goes to the brain.
Both of these senses pertain to the body's ability to recognize chemicals. The taste receptors are the taste buds on the tongue, and the odor receptors inside the nose sense chemicals in the air. Both of these receptors send nerve impulses to the brain, which then interprets these chemicals.
Sound waves enter the auditory canal, then the eardrum, and the cochlea. The sound waves move around the hairs inside the ear, which send nerve impulses to the auditory nerve.
This system, which maintains the body's balance, is also controlled by the ears. When your body moves, there is Fluid in the ear that moves with your head. Tiny hairs in your ear sense this movement and sends messages to the peripheral nervous system, which then controls your body and makes sure you do not lose your balance.
Because your sense of touch is your body's ability to sense pressure, the pressure receptors on your skin, tongue, lips, palms, and feet serve to send nerve impulses to the brain. Moreover, some of these receptors can also note differences in temperature.
Psychoactive drugs, which include alcohol, caffeine, nicotine, and marijuana, affect the central nervous system by influencing the transmission of nerve impulses. Drug abuse is when people use psychoactive drugs without the approval of a medical professional or for reasons the drug was not intended for, and drug addiction is the continued use of these types of drugs.