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A Little Bit More

Despite considerable scientific interest in this winter-time behavior, it has only been recently that biologists have begun to understand which animals actually hibernate and what is involved. Hibernation requires the achievement of a torpid (inactive or numb) state during which the heart rate, breathing rate, and body temperature are reduced to very low levels. In endotherms (warm-blooded animals), hibernation results in a reduction in general metabolism to a degree never found in the deepest everyday sleep. For example, ground squirrels that normally breathe about 50 times per minute may breathe only 4 times per minute in hibernation and their heart rate may go from 200-350 beats per minute to as few as 5.

In hibernation’s state of suspended animation, only the vital life functions of an animal continue. A hibernating animal survives on about 1/100th of its normal supply of food and oxygen. The optimum environmental temperature for hibernation is about 4.5°C

(40°F). If the temperature around a hibernating animal reaches the freezing point, its metabolic rate actually increases. This increase probably helps ensure that the animal will not freeze to death. If the temperature rises above a certain point, the animal rouses.

Although Black Bears are widely credited with hibernating, they do not fulfill the requirements of “true” hibernators. Bears do sleep a lot in winter and consume a great deal of their body fat, but their body temperature, breathing rate, and pulse remain too high for them to qualify for true hibernation status. Their shallower winter dormancy is referred to more scientifically as “carnivorean lethargy”, not hibernation. Now there’s a term you can use to impress your friends!

Activities

Pulsing

The “Little Bit More” part of this unit talks about a lowered pulse in hibernating animals and we all know about doctors taking our pulse to determine our health. This is an opportunity for students to find a couple of places on their body that they can take their own pulse so they know what it’s like. If you’re in a school that has a nurse, you may want to bring her/him in to help with this exercise.

There are two places on humans where a pulse is regularly taken – the wrist and the neck.

WRIST PULSE

1. Have your students stretch out one of their arms and uncover their forearm if there is clothing obstructing the wrist.

2. Have each student turn their outstretched arm “wrist up” for this exercise.

3. With the hand opposite the outstretched arm, have each student place three middle fingers just below the base of their thumb on their wrist.

4. With gentle pressure, they should begin to feel their own pulse (this may take some trial and error). They should be able to feel the pulse of their radial artery which provides blood to the hand.

5. Once they can easily feel their own pulse, have them look at a wall clock or watch with a second hand and count the number of pulses within 15 seconds. They should write down the number they reach and multiply by 4 to determine how many pulses they have per minute. This will give them their pulse rate.

NECK PULSE

Once they’ve felt their own pulse on their wrist, they can try finding their pulse on their neck.

1. Have each student place their three middle fingers (left hand for left side of neck) just under their jaw about midway back from the front of their mouth.

2. This also may take a bit of trial and error but with gentle pressure and minor finger adjustments, they should be able to find their pulse on the carotid artery which provides blood to the brain. (Hint – if one student is able to find their carotid pulse quickly, have the others take a look where that site is located)

3. Have students again count the number of pulses for a 15 second period, multiply by 4 and determine the number per minute. This figure should be very close to the wrist pulse rate figure.

If you would like, you can have students try taking the pulse of a friend. I’d suggest they use the wrist, not the neck, however.

You may also want one or more students to try counting their pulse at-rest, after moderate activity and after vigorous activity. Be sure you chart these and see what you find out.

REMEMBER, THESE ARE NOVICES TAKING PULSES, NOT PROFESSIONALS, SO DON’T BECOME ALARMED IF SOMEONE HAS AN “UNUSUAL” PULSE RATE – THEY PROBABLY GOT IT WRONG!!!!! Typical at-rest pulse is 70 beats per minute but this does vary!

Once the students have taken their pulses and written them down, have them share the numbers they’ve reached. Would be interesting to average them out too and find out what the average pulse rate is for all those participating and interesting to see if there is any difference in girl averages and boy averages. It would also be interesting to compare the student average with the instructor’s own pulse – adult and child pulses should be different.

Key Concepts

Behavior and Regulation, Life Cycles

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