Nervous and Endocrine System

• The nervous system is the body's decision and communication center
• The central nervous system (CNS) consists of the brain and spinal cord, while the peripheral nervous system (PNS) involves all the nerves
• The brain, as the control center of the nervous system, has three main parts: the forebrain, midbrain, and hindbrain, and is divided into the cerebrum, cerebellum, and brain stem
• The spinal cord, about 40-50 cm long, interconnects the brain and body, transmitting impulses and responsible for involuntary movements
• The somatic nervous system (SNS) regulates activities under conscious control, including nerves controlling the muscular system and external sensory receptors
• The autonomic nervous system (ANS) regulates involuntary activities and is subdivided into the sympathetic and parasympathetic nervous systems
• The sympathetic nervous system is responsible for the "fight or flight response," while the parasympathetic nervous system controls internal functions at rest
• Receptors in the nervous system include photoreceptors, mechanoreceptors, chemoreceptors, olfactory receptors, nociceptors, and thermoreceptors
• Neurons, the basic unit of the nervous system, carry impulses and consist of dendrites, nucleus, cell body, axon, nodes of Ranvier, myelin sheath cells, and axon terminal
• Classification of neurons: sensory or affective neurons carry impulses from sense organs to the brain, motor or effective neurons carry impulses from the brain to muscles, and associative neurons analyze and interpret data in the CNS
• The endocrine system secretes hormones into the bloodstream to regulate body processes like growth, development, metabolism, and response to stimuli
• Hormones help regulate body processes and act as chemical messengers transporting signals between cells
• Homeostasis is the state of steady internal conditions maintained by living organisms through the regulation of bodily functions by the endocrine and nervous systems
• Negative feedback mechanisms aim to reduce detected changes, while positive feedback mechanisms amplify detected changes
• The endocrine system plays a crucial role in maintaining homeostasis by keeping hormone levels at the right balance
• To achieve homeostasis, the nervous and endocrine systems maintain normal ranges of body temperature, water amount, metabolic waste, blood calcium level, and hormones in the blood