Nervous and endocrine systems
The brain does not work alone: it is part of a body-wide communication network.
Central and peripheral nervous systems
The central nervous system is the brain and spinal cord. The peripheral nervous system connects them to the rest of the body. Its somatic division controls voluntary movement and carries sensory information; its autonomic division controls automatic functions such as heart rate and digestion.
Fight or flight
The autonomic system has two branches. The sympathetic nervous system prepares the body for action in stressful situations, raising heart rate, widening pupils, and slowing digestion: the 'fight or flight' response. The parasympathetic nervous system calms the body afterward, supporting 'rest and digest' functions.
The endocrine system
The endocrine system uses hormones carried in the blood. The pituitary gland, often called the master gland, controls many other glands. The adrenal glands release adrenaline and cortisol in stress, the thyroid regulates metabolism, and the pancreas regulates blood sugar through insulin. Hormones act more slowly than nerve signals but have longer-lasting effects.
Flashcard
Activates the body's fight-or-flight response
Check your understanding
A hiker sees a bear and feels her heart pound and breathing speed up. Which system is most active?