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Phases of an Action Potential - Resting Potential, Threshold, Rising, Falling, & Recovery Phases

By: HWC, Views: 7156

In this tutorial, we will review the phases of an action potential measured from a small area of a neuron's membrane. The action potential can be divided into five phases: the resting potential, threshold, the rising phase, the falling phase, and the recovery phase. When the neuron is at rest,...

Role of complement proteins

By: HWC, Views: 7497

• Non-specific and specific defense mechanisms work through the functions of complement proteins. • As soon as pathogens penetrate the physical barrier of the skin, other resistance mechanisms begin. • Cells, such as macrophages, phagocytize pathogens. • These cells increase exposu...

Plant Defense Mechanisms from Pathogens

By: HWC, Views: 7199

Plants and pathogens have coevolved such that pathogens can recognize plants by the sugars, or other molecules, they produce. Plants, in turn, can recognize pathogens by the molecules they produce. The ability to recognize pathogens allows plants to activate defense systems that can prevent wides...

Proteins Defined, Hierarchy & Composition of Cells

By: HWC, Views: 7215

Proteins are long chains of amino acids linked together by peptide bonds. Together with the other three biological macromolecules—carbohydrates, lipids, and nucleic acids—proteins are the building blocks of cells. Proteins are the most complex and abundant biological macromolecules in cel...

Type of Cell Junctions - Desmosome, Hemidesmosomes and Gap Junctions

By: HWC, Views: 8091

Cell Junctions: Cell junctions are found in some multi-cellular organisms. They exist of complexes and are found between cells and between cells and other structures. The junctions provide a way for cells to connect and exchange signals. What are tight junctions, desmosomes, and gap junctions...

Action potentials - electrical characteristics and generation

By: HWC, Views: 7586

• An action potential is the nervous impulse or signal for long distance communication. Each action potential is generated at the cell's trigger zone. • Action potentials are considered an all-or-nothing phenomena because they are either generated or not. • The generation of an action...

Second Messengers in the Inositol-lipid Signaling Pathway

By: HWC, Views: 7017

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...

Nervous pathway to the Neuromuscular (NMJ)

By: HWC, Views: 8291

• A nervous impulse, also called an action potential, starts from the brain or spinal cord to signal skeletal muscle cell contraction. Action potentials continue along a motor neuron to the muscle cell. • The signal to contract must cross a synapse - the neuromuscular junction (NMJ) - betwe...

Mechanisms of capillary exchange

By: HWC, Views: 7892

■ The primary role of capillaries is to permit the exchange of nutrients and wastes between the blood and tissue cells (via interstitial fluid). ■ Oxygen and nutrients move from the blood to the cells. ■ Carbon dioxide and other wastes move from the cells to the blood. The three ba...