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Effect of the environment on coat color in the Himalayan rabbit Animation

By: HWC, Views: 2229

An organism's phenotype—the combination of traits that we observe—is the product of interactions between its genotype and the environment. For example. a Himalayan rabbit is completely white at birth. But within weeks, the fur on the rabbits ears, nose, tail. and lower legs darkens. The...

Metabolic Rate, Heat and Thermoregulation - response to heat and cold stresses

By: HWC, Views: 6845

• A neuron group in the anterior portion of the hypothalamus controls heat balance. • Neurons in the preoptic region of the hypothalamus integrate signals that come from thermoreceptors. • The temperature control center in the preoptic region propagates control signals to two other part...

Factors that increase metabolic rate and heat production

By: HWC, Views: 6643

• All vital biochemical reactions are temperature dependent. • The overall rate at which metabolic reactions use energy is known as the metabolic rate. • Metabolic rate greatly determines body temperatures. • Temperature is maintained by balancing the loss of heat to the environment...

Second Messengers in the Inositol-lipid Signaling Pathway

By: HWC, Views: 5862

Extracellular signals produce specific responses in target cells through the action of intracellular second messengers. Here, we focus on three second messengers, IP3, DAG, and Ca2+, all involved in the inositol-lipid signaling pathway. A hormone-receptor signal on the cell surface leads to the a...

Griffith's experiments

By: HWC, Views: 3767

In the late 1920s, Fred Griffith was attempting to develop a vaccine against a bacterium that causes pneumonia. To find out why two strains of the bacteria differed in their deadliness, he injected mice with four different mixtures. Mice injected with R cells remained healthy. When Griffith ex...

The Hypothalamus: The Body's Thermostat (Human Thermostat)

By: HWC, Views: 5871

Normal body function requires a relatively constant body temperature, which is regulated by the body's thermostat, a region of the brain called the hypothalamus. The hypothalamus generates a temperature set point for the body and appears to be the major site for the integration of temperature inf...

Chemical Changes

By: HWC, Views: 6049

Observe the burning logs of wood. The logs burn to emit heat, light and carbon dioxide. What is left behind is ash. This residue is a new substance with a different molecular structure than the original wood. Similarly when baking the dough into bread, it becomes fluffy and light. There is a ch...

Stimulus (introduction)

By: HWC, Views: 6299

• Blood pressure determines the flow of blood to and from capillaries. • Low blood pressure results in reduced blood flow. • High blood pressure can cause blood vessels to break. In humans, sensitivity is due to portions of the nervous system called receptors. Receptors are typicall...

Nerve Impulse Transmission Animation

By: Administrator, Views: 9991

How nerves transmit impulses. Stimulation of a nerve occurs at a receptor. Sensory receptors Specialized to specific types of stimulation such as heat, cold, light, pressure, or pain. React by initiating a chemical change or impulse. All-or-none principle Means that no transmission occ...