Nervous System on a large scale

nerves= neural cables containing axons

• part of peripheral nervous system-- muscles, glands, sensory organs
• central nervous system is only the brain and the spinal cord, it is where messages are received, processed and then sent back out 
• peripheral nervous system is throughout the body. It includes sensory organs, glands, muscles
• autonomic-- controls self-regulated action of internal organs and glands (heartbeat)
• sympathetic: arousing-- provides activation and energy when needed
• parasympathetic: calming-- helps conserve energy, controls blood flow to sex organs and is constantly telling them to stay calm
• somatic-- controls voluntary movements of skeletal muscles
• peripheral nervous system connects the central nervous system with the rest of the body

Types of Neurons

• sensory neurons: carry messages from peripheral system to central system
• motor neurons: carry messages from central system to peripheral system
• interneurons: connect sensory and motor neurons
• reflexes- burning hand example: reflex happens without aid of brain, controlled by nervous system alone= sensory--> interneuron--> motor neuron in less than 1 sec
• in the brain, the nervous system is less like a chain and more like a web

Endocrine system-- secretes chemical messages through hormones

• hormones can be chemically identical to neurotransmitters, but take much longer to send
• messages stay in place longer: example- still feeling stressed after finishing a test
• pituitary gland: growth hormones and controls release of other hormones (master gland)
• nervous  system directs endocrine secretions, which then affect the nervous system