Homeostasis and Body SystemsBiology

Role of the Nervous System

The nervous system is very important in maintaining homeostasis within our bodies.

The nervous system regulates:• Automatic Responses

– Ex = shivering when cold• Voluntary Responses

– Ex = putting on a sweater

The Brain is the Nervous System

Control CenterDifferent parts of the brain control different

nervoussystem responses:• Receive and transmit information• Regulate physiological processes like

– water balance– body temperature– hunger– sleep

The Brain also helps to regulate the Endocrine SystemThe Endocrine System is made of

glands and cells that produce and release

chemical messages in the form of HORMONES.

Hormones stimulate processes that help

maintain homeostasis.

Hormones Transported in Blood

• Hormones are chemicals• Control balance of sugar absorption

by cells, water balance in body, and much more

• Moved within blood stream past every part of body

• Recognized only by “Target Cells” with special receptor proteins that can interact with the hormones (like a lock & key)

Example of Hormone Function

Dehydration:1. Sensor cells in brain detect water

shortage because body has higher sodium concentration when water concentration is low .

2. Brain cells signal for production and release of hormones (ex. Vasopressin) which are carried in the blood throughout the body.

Example of Hormone Function cont…3. Target cells that have certain receptors

for this hormone (kidney cells) receive hormone message.

4. Message signals cell membranes of kidney tubule cells to become more permeable to water.

5. More water is reabsorbed by circulatory system and kept within body.

6. Prevents excess water from being released in urine and restores the water balance.

Feedback Systems

• Groups of body systems that work together to maintain homeostasis in the body.

• Regulates body responses to changing conditions outside and inside the body.

• Can be POSITIVE or NEGATIVE

Negative Feedback

• Body detects change• Body systems attempt to correct the

abnormal situation

Real-World Examples:

Body System Examples:

-Thermostat -Body temperature maintenance

-Driving in traffic -Blood pressure regulation

Posi

tive F

eedback

Exam

ple

Positive Feedback

• Quick response that amplifies the change (instead of “correcting it” in

negative feedback)

Real-World Examples:

Body System

Examples:

- Dominos -Blood clotting

-Crowd cheering/clapping

-Contractions

during childbirth

The End