Summary
Highlights
The sympathetic branch activates during stress responses, releasing noradrenaline. It increases bodily activities like heart rate and breathing, dilates pupils, and halts digestion, often known as the 'fight-or-flight' response.
The nervous system, often associated with the brain and spinal cord, extends throughout the entire body. This video will construct a diagram of the nervous system, with a blank form available on the presenter's website.
The human nervous system is an intricate network of nerve cells collecting and processing information from the world, directing bodily organs and muscles through electrochemical messages. It is divided into two primary parts: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
The CNS is responsible for complex processing, encompassing the brain (for both conscious and unconscious processing) and the spinal cord. The spinal cord transmits information to and from the brain and body and can also perform basic motor reflexes.
The PNS is a body-wide network of messenger neurons. Sensory (afferent) neurons deliver information to the CNS, while motor (efferent) neurons transmit information away from the CNS. The PNS is further divided into the Somatic Nervous System (SNS) and the Autonomic Nervous System (ANS).
The SNS controls skeletal muscles and is a voluntary system, meaning it is under conscious control (e.g., deciding to move an arm).
The ANS controls internal organs and glands and is an involuntary system, not under conscious control (e.g., heart rate, insulin release). The ANS itself has two branches: sympathetic and parasympathetic.
The parasympathetic branch activates during rest, releasing acetylcholine. It decreases bodily activities like heart rate and breathing, constricts pupils, and stimulates digestion. Homeostasis is the balance maintained between these two systems for a normal internal environment.
The gut contains approximately 100 million nerve cells, aiding in food processing and digestion, which is comparable to the number of nerves in a cat's brain.