Review! Vocabulary

The tendency of an organism to maintain a stable, constant

internal environment

homeostasis

The body’s internal temperature.

Core temperature

The body’s external temperature.

surface temperature

A specialized porous structure in the leaf of a plant that helps it

achieve internal balance.

stomata

Specialized cells of the nervous system which relay signals to the spinal cord and

brain.

Sensory Neurons

An involuntary response that happens internally.

Physiological Response

A response that is outwardly observed that is consciously

controlled.

Behavioral Response

A response that is outwardly observed that is NOT

consciously controlled.

Reflex

This system is made up of the brain, the spinal cord, and the nerves that are found throughout the body and

regulates automatic responses.

Nervous System

A type of cell in the nervous system that produces, sends,

and receives signals.

Neurons

A type of nerve cell that protects, supports, and insulate

neurons.

Glial Cells

A specialized part of the brain that is part of the nervous and endocrine system and

regulates physiological processes like water balance, body temperature,

feeding, and sleep.

Hypothalamus

A body system made up of glands that releases hormones.

Endocrine System

Chemical messengers that travel through the bloodstream.

Hormones

Proteins that fit the shape of a hormone similar to a “lock and

key.” Once the hormone is bound, the cell is ready to

respond.

Receptors

A hormone released from the pituitary gland during dehydration causing

kidneys to reabsorb more water and less water to be excreted in urine.

Vasopressin

A gland that is part of the hypothalamus and releases

vasopressin

Pituitary Gland

A system that keeps automatic responses from vastly changing

internal conditions.

Feedback Systems

A system that shuts off a response that the body originally

had because it was out of balance.

i.e. water balance and hypothalamus stops releasing vasopressin

Negative Feedback

A feedback system that adjusts internal conditions towards the

initial condition.

i.e. Blood clot, so you send more clotting fibers to reduce blood loss.

Positive Feedback

How does the endocrine system and the nervous system each contribute to

maintaining homeostasis?

• The nervous system senses the outside environment and initiates a series of reactions in the body to allow the body to respond. The endocrine contributes to homeostasis by producing hormones or chemical messengers that carry out a process that helps restore balance in the body.

Explain the role that sensory neurons play in the maintenance of homeostasis in the

human body.

• Sensory neurons receive signals and trigger the brain to respond to external stimuli.

Describe the general way that feedback systems work to adjust internal conditions

in response to change.

• A positive feedback system adjusts the body internally towards an initial condition. Oxytocin/child birth is positive feedback.

Describe the general way that feedback systems work to adjust internal conditions

in response to change.

• A negative feedback system stops the response that the body had to being out of equilibrium. For example, when one goes from dehydrated to hydrated vasopressin causes the kidneys to absorb more water. Once the person is hydrated, negative feedback tells the hypothalamus to stop producing vasopressin..