Homeostasis

Homeostasis: 

Homeostasis The Body’s Thermostat

The Story of The Titanic: 

The Story of The Titanic The Titanic collided with an iceberg at 11:40 pm on 14th April 1912. About 650 passengers were lowered in lifeboats capable of holding 1178; the remaining passengers entered the sea as the Titanic sank. Hundreds of people thrashed about in water that was less than -2°C. It was 4:10am before another ship arrived to collect the survivors. Only 705 of the 2207 survived - 1502 died.

The Story of The Titanic: 

The Story of The Titanic Many of the passengers had life jackets and there was a lot of debris to hang onto. It was a calm and still night. Why did some of them die? Why did some survive?

The Need For Homeostasis: 

The Need For Homeostasis Homeostasis is the maintenance of a constant internal environment . Main control centre: BRAIN (hypothalamus)

Conditions that need to be kept the same include: : 

Conditions that need to be kept the same include: Temperature pH Concentration of solutes (glucose, salts, carbon dioxide) Water potential

Why is homeostasis important?: 

Why is homeostasis important? Temperature, pH and substrate concentration can affect the rate of enzyme- catalysed reactions . If the environment is not stable, the rate of enzymatic reactions decreases, thus affecting life processes.

Examples of Homeostatic Processes: 

Examples of Homeostatic Processes Regulation of carbon dioxide level Regulation of blood glucose level Regulation of water potential Regulation of body temperature (new)

Principles Of Homeostasis: 

Principles Of Homeostasis Homeostatic processes involve: Stimulus A change in the internal environment Receptor Detects the stimulus or the change Corrective mechanism Responds to bring back the original condition Negative feedback Information about the change as effected by corrective mechanism is fed back to the control centre

Feedback Mechanism: 

Feedback Mechanism … is the regulation of a process by the results or products of the process. Corrective mechanism Normal condition Stimulus (above normal) Negative Feedback

Feedback Mechanism: 

Feedback Mechanism … is the regulation of a process by the results or products of the process.

The Mammalian Skin: 

The Mammalian Skin Body Temperature Control

How do we maintain our body temperature in a hot environment?: 

How do we maintain our body temperature in a hot environment?

Red cheeks: 

Red cheeks

Hair lies flat: 

Hair lies flat

Sweating: 

Sweating

Anatomy Of The Skin: 

Anatomy Of The Skin

The Mammalian Skin – regulation of body temperature: 

The Mammalian Skin – regulation of body temperature

Summary Functions: 

Summary Functions Traps air to form an insulating layer when cold. Contracts to make hair stand upright. Secrete sweat. When sweat evaporates, it cools the body. Detect changes in temperature, sensations of touch, pain and so on. Sends impulses to the CNS / brain / spinal cord. Dilate or constrict to supply more or less blood to the capillaries in the skin. Stores fats and provides insulation against cold. hair hair erector muscle sweat glands nerve endings/ receptors arterioles adipose tissue neurone

Slide 19: 

Regulation of body temperature Humans are ____________ (internal source of heat). Core temperature kept at about 37 °C . endotherms

How do we maintain our body temperature?: 

How do we maintain our body temperature? http://www.think-bank.com/iwb/flash/homeostasis.swf

Think: Body temperature readings: 

Think: Body temperature readings Where on the body can body temperature readings be taken from? ANUS FINGER SKIN SURFACE EAR MOUTH

Investigation: 

Investigation In cold weather, some warm-blooded animals crowd closely together in a group. Design an experiment to investigate the advantage of crowding in temperature control.

Thinking Point: Can the set point be altered?: 

Thinking Point: Can the set point be altered? Fever . Chemicals called pyrogens released by white blood cells raise the set point of the thermoregulatory centre causing the whole body temperature to increase by 2-3 °C. This helps to kill bacteria (white blood cells work best at this temperature). Hibernation . Some mammals release hormones that reduce their set point to around 5°C while they hibernate. This drastically reduces their metabolic rate and so conserves their food reserves.

Exercise: 

Exercise Draw the negative feedback loop for the regulation of temperature. Normal body temperature Corrective Mechanism 1. 2. 3. Corrective Mechanism 1. 2. 3. Normal body temperature stimulus stimulus Negative feedback Negative feedback

Slide 25: 

Regulation of carbon dioxide level Changes in carbon dioxide concentration of blood automatically affect the rate of breathing . During exercise, carbon dioxide in blood increases . This causes rate of breathing to increase . Increased exhalation helps body to get rid of carbon dioxide faster. As a result, the carbon dioxide level returns back to normal. The restoring of the normal state gives a negative feedback which switches off the mechanism that causes the rate of breathing to increase.

Slide 26: 

Regulation of blood glucose level Changes in blood glucose concentration is detected by pancreas which secretes either: (After eating) insulin is secreted which concerts excess glucose to glycogen . (During starvation) glucagon is secreted which converts stored glycogen in liver to glucose. As a result, the glucose level returns back to normal. The restoring of the normal state gives a negative feedback which switches off the mechanism that causes the change in the hormone produced.

Slide 27: 

Regulation of water potential Changes in water potential in the blood is detected by osmoreceptors in the hypothalamus which causes the pituitary gland to secrete either: (After sweating) more ADH to increase water reabsorption so that less urine is produced (After drinking) less ADH to decrease water reabsorption so that more urine is produced As a result, the water potential returns to normal. The restoring of the normal state gives a negative feedback which switches off the mechanism that causes more or less of the hormone to be produced.