Homeostasis & Positive & Negative Feedback

Chordate Traits

Dorsal hollow nerve cord, notochord, pharyngeal pouches, and tail beyond the anus.

Notochord

Flexible support rod that becomes the backbone in vertebrates.

Dorsal Hollow Nerve Cord

Tube along the back that develops into the spinal cord and brain.

Pharyngeal Pouches

Structures that can develop into gills, ears, or throat parts.

Tail (Chordates)

Extension beyond the anus used for movement or balance.

Levels of Organization (Animals)

Cells → Tissues → Organs → Organ Systems → Organism.

Epithelial Tissue

Covers internal and external body surfaces.

Muscle Tissue

Contracts to create movement.

Nervous Tissue 

Transmits electrical messages through the body.

Connective Tissue

Provides support and structure (includes bone and cartilage).

Homeostasis

Maintaining stable internal conditions despite external changes.

Feedback Inhibition (Negative Feedback) 

The result of a process limits or stops the process to maintain balance.

Example of Feedback Inhibition (House)

Thermostat turns furnace on/off to keep temperature steady.

Example of Feedback Inhibition (Human)

Shivering generates heat when cold; sweating cools the body when hot.

Goal of Feedback Systems

Keep internal conditions within narrow, safe ranges.

Systems Working Together

Nervous, muscular, respiratory, circulatory, digestive, and excretory systems interact to maintain homeostasis.

Ectotherm

Cold blooded animal; relies on environment for temperature (e.g., lizard).

Endotherm

Warm blooded animal; maintains temperature internally (e.g., human).

Too Hot Response 

Sweat glands activated, blood vessels dilate, body cools.

Too Cold Response

Shivering generates heat, blood vessels constrict, body warms.

Hypothalamus Function

Brain region that detects body temperature changes and triggers responses.

Cellular Respiration

Process that uses oxygen to produce energy (ATP) from nutrients.

Gas Exchange in Animals

Small animals use diffusion; large ones use gills, lungs, or air passages.

Digestive System Function

Breaks down food into usable nutrients.

Circulatory System Function 

Transports oxygen and nutrients throughout the body.

Respiratory System Function

Removes carbon dioxide from the body.

Excretory System Function 

Removes nitrogenous waste like urea.

Nervous System

Detects and processes stimuli using receptors and sends responses.

Receptors

Cells that detect sound, light, and chemicals in the environment.

Musculoskeletal System

Muscles + skeleton working together for movement.

Invertebrate Skeleton Types

Flexible (fluid pressure) or external (exoskeleton).

Vertebrate Skeleton

Internal skeleton made of bone.

High Blood Sugar

Pancreas releases insulin → Cells absorb glucose → Blood sugar decreases.

Low Blood Sugar 

Pancreas releases glucagon → Liver releases stored glucose → Blood sugar increases.

Insulin Function

Hormone that lowers blood glucose levels.

Glucagon Function 

Hormone that raises blood glucose levels.

Type 1 Diabetes

Pancreas cannot produce insulin; glucose stays in blood, reducing energy production.

Liver Role in Homeostasis 

Converts ammonia to urea, detoxifies drugs, and regulates blood glucose.

Result of Too Much Glucose

Cell and organ damage, leading to diabetes.

Result of Too Little Glucose

Low energy, dizziness, or fainting.

Positive Feedback Definition

Enhances a process instead of counteracting it.

Positive Feedback Example

Childbirth: pressure on cervix → hormone release → contractions increase until baby is born.

Homeostasis Purpose

To keep the internal environment balanced and stable.

Negative Feedback Goal 

Return conditions to normal (balance).

Positive Feedback Goal

Drive process to completion (e.g., childbirth).

Failure of Homeostasis

Can lead to disease, like diabetes.

Example of Interacting Systems

Digestive and circulatory systems work together to provide cells with nutrients and oxygen.

Why is feedback inhibition essential for homeostasis?

Because it prevents systems from overreacting, keeping internal conditions stable by reversing changes when they go too far.

How does the hypothalamus act like a thermostat?

It detects temperature changes and triggers mechanisms like sweating or shivering to restore balance.

What would happen if feedback inhibition failed in temperature regulation? 

The body could overheat or become hypothermic, since corrective responses would not stop or start properly.

Why do ectotherms rely on behavioral changes for temperature regulation?

They can’t generate heat internally, so they move to different environments (like sun or shade) to maintain body temperature.

Why is negative feedback considered stabilizing?

Because it counters deviations from a set point, bringing the system back to equilibrium.

How is positive feedback different from negative feedback?

Positive feedback amplifies a change until an event ends, while negative feedback reverses a change to restore stability.

Why is childbirth an example of positive feedback?

Hormones cause contractions, which increase pressure, triggering more hormones and stronger contractions until birth.

What would happen if the pancreas stopped releasing insulin?

Blood glucose would stay high, preventing cells from getting energy—leading to diabetes symptoms.

Why do large animals need specialized respiratory and circulatory systems? 

Diffusion alone can’t deliver oxygen or nutrients efficiently across their larger body volume.

How does the liver help maintain blood glucose levels?

It stores glucose after meals and releases it when levels drop, preventing dangerous highs and lows.

How do the digestive and circulatory systems work together?

Digestive system breaks food into nutrients → Circulatory system transports them to cells for energy.

Why are the nervous and muscular systems linked in movement?

The nervous system sends electrical signals that tell muscles when and how to contract.

How does shivering warm the body?

Muscle contractions use energy and generate heat, raising body temperature.

Why is sweating an effective cooling mechanism?

Evaporation of sweat removes heat from the skin’s surface, lowering body temperature.

What kind of feedback loop is blood glucose regulation? 

Negative feedback—because insulin and glucagon act to restore blood sugar balance.

How does diabetes represent a failure of homeostasis?

The feedback system that regulates blood sugar is broken, leading to harmful glucose levels.

Why do chordates have a notochord and nerve cord?

They provide structural support and a communication network for movement and sensory processing.

Why is segmentation an advantage in animal body plans?

It allows flexibility, redundancy, and specialization of body parts.

What could happen if waste removal systems failed?

Toxins and carbon dioxide would build up, poisoning cells and disrupting homeostasis.

How do organ systems interact to maintain homeostasis? 

They share information and resources—for example, the respiratory, circulatory, and excretory systems work together to exchange gases and remove wastes.