ASVAB General Science: Nervous System
The nervous system is a complex network of specialized cells and tissues that coordinate and regulate body functions. It's divided into two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS). Let's explore the major components and their functions.
The Central Nervous System consists of the brain and spinal cord.
The brain is the command center of the nervous system. It has several major parts:
- Cerebrum: The largest part of the brain, responsible for higher functions like thinking, learning, and memory. It's divided into left and right hemispheres, each controlling the opposite side of the body.
- Cerebellum: Located at the back of the brain, it coordinates movement, balance, and posture.
- Brain stem: Connects the brain to the spinal cord and controls vital functions like breathing, heart rate, and blood pressure.
- Thalamus: Acts as a relay station for sensory and motor signals.
- Hypothalamus: Regulates body temperature, hunger, thirst, and circadian rhythms. The spinal cord extends from the brain stem and runs down the back. It carries messages between the brain and the rest of the body and controls some reflexes.
The Peripheral Nervous System includes all the nerves outside the CNS. It's further divided into the somatic nervous system, which controls voluntary movements and relays sensory information, and the autonomic nervous system, which regulates involuntary functions like heart rate, digestion, and breathing. The autonomic nervous system has two subdivisions: the sympathetic which activates the "fight or flight" response, and the parasympathetic, which promotes the "rest and digest" state.
Neurons are the basic units of the nervous system. They consist of a cell body, dendrites (which receive signals), and an axon (which transmits signals). Neurons communicate through electrical and chemical signals called neurotransmitters. Glial cells support and protect neurons, providing nutrients and oxygen, removing dead neurons, and insulating axons.
The nervous system performs several crucial functions:
- Sensory input: Gathering information from sensory receptors.
- Integration: Processing and interpreting sensory information.
- Motor output: Sending signals to muscles and glands.
- Homeostasis: Maintaining internal balance.
- Higher cognitive functions: Enabling thinking, learning, and memory.
Disorders of the nervous system can have wide-ranging effects on the body. Common conditions include Alzheimer's disease, Parkinson's disease, multiple sclerosis, and epilepsy.
The nervous system interacts closely with other body systems, particularly the endocrine system, to maintain overall health and respond to environmental changes.