2 Nervous SystemNervous system: The system of cells, tissues and organs that regulates the body's responses to internal and external stimuliThe nervous system is made up of: nervous tissue, the brain, and the spinal columnPlays a key role in maintaining internal balance
3 Nervous System The brain – control center for the nervous system Hypothalamus- regulates water balance, body temperature, feeding, sleep and the endocrine systemEndocrine system: made up of glands and cells that release hormones into the blood
4 Endocrine SystemHormones: chemical messengers in the body. They regulate internal balances like water and blood sugar balanceOnly certain target cells are able to respond to the hormone. If an organ has a receptor for that hormone than it will respond
5 Endocrine SystemReceptors: proteins that fit the shape of a specific hormone molecule. They work in a lock and key fashionDehydration example:hypothalamus detects that the body is short of water (concentration of sodium increases)
6 Endocrine SystemHypothalamus signals the pituitary gland to release vasopressin (a type of hormone) into the bloodstream.Vasopressin binds to the receptors in the kidneyVasopressin causes the tubules in kidneys to become more permeable to water
7 Nervous SystemRemember: reabsorbing water and losing less in the urine prevents the body from going into dehydration.Feedback- Body automatically sensing changing conditions
8 Nervous System Feedback is important for maintaining internal balance Feedback can cause the body to counteract the initial condition or enhance them.
9 Nervous SystemNegative feedback: body reacts to internal conditions that need to change by trying to change the balance away from them.Ex: dehydration, blood pressureBlood pressure: nervous system sensors in neck detect change. Signal is sent to brain. Brain responds by increasing heart rate. Increased heart rate increases blood pressure.
10 Nervous SystemThe brain also signals blood vessels to constrict which also increase blood pressure.Positive feedback: adjusts internal conditions toward the initial. Ex: being cut
11 Review:Nervous system: fast acting responses such as thirst hungerEndocrine: slower and longer lasting responses such as secretion of vasopressin
12 Nervous system has two types of cells: Neurons: produce and send nerve impulsesGlial – protects, supports, and insulates neurons