Group Living Has Advantages and Disadvantages

When animals live together in groups such as flocks or herds

Disadvantage- Group promote competition for food and increased transmission of parasites and other diseases.

Advantage - Benefits relate to group defense against predators through increased vigilance and through protection in numbers.

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#Unit 7. System Physiology – Animal

Between heartbeats, influx of positively charged sodium ions causes a slow rise in the resting membrane potential in the positive direction. 

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#Unit 7. System Physiology – Animal

When the potential reaches a threshold voltage of about −40 millivolts, the L-type calcium channels become “activated,” causing the action potential.

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#Unit 7. System Physiology – Animal

L-type calcium channels become inactivated (i.e., they close) within about 100 to 150 milliseconds after opening

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#Unit 7. System Physiology – Animal

When the L-type calcium channels become inactivated at about the same time, greatly increased numbers of potassium channels open.

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#Unit 7. System Physiology – Animal

Large quantities of positive potassium ions diffuse out of the SA node.

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#Unit 7. System Physiology – Animal

Potassium channels remain open for another few tenths of a second, with resultant excess negativity inside the fiber; this process is called hyperpolarization.