Nervous System/ Endocrine System

Nervous System

• Nervous system: The system of cells, tissues and organs that regulates the body's responses to internal and external stimuli

• The nervous system is made up of: nervous tissue, the brain, and the spinal column

• Plays a key role in maintaining internal balance

Nervous System

• The brain – control center for the nervous system

• Hypothalamus- regulates water balance, body temperature, feeding, sleep and the endocrine system

• Endocrine system: made up of glands and cells that release hormones into the blood

Endocrine System

• Hormones: chemical messengers in the body. They regulate internal balances like water and blood sugar balance

• Only certain target cells are able to respond to the hormone. If an organ has a receptor for that hormone than it will respond

Endocrine System

• Receptors: proteins that fit the shape of a specific hormone molecule. They work in a lock and key fashion

• Dehydration example:

• hypothalamus detects that the body is short of water (concentration of sodium increases)

Endocrine System

• Hypothalamus signals the pituitary gland to release vasopressin (a type of hormone) into the bloodstream.

• Vasopressin binds to the receptors in the kidney

• Vasopressin causes the tubules in kidneys to become more permeable to water

Nervous System

• Remember: reabsorbing water and losing less in the urine prevents the body from going into dehydration.

• Feedback- Body automatically sensing changing conditions

Nervous System

• Feedback is important for maintaining internal balance

• Feedback can cause the body to counteract the initial condition or enhance them.

Nervous System

• Negative feedback: body reacts to internal conditions that need to change by trying to change the balance away from them.

• Ex: dehydration, blood pressure

• Blood 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.

Nervous System

• The brain also signals blood vessels to constrict which also increase blood pressure.

• Positive feedback: adjusts internal conditions toward the initial. Ex: being cut

• Review:

• Nervous system: fast acting responses such as thirst hunger

• Endocrine: slower and longer lasting responses such as secretion of vasopressin

• Nervous system has two types of cells:

• Neurons: produce and send nerve impulses

• Glial – protects, supports, and insulates neurons