Chapter 14 part 3 Flashcards
Homeostasis and Tropic responses
What is Homeostasis?
Homeostasis is the maintenance of a constant internal environment.
What is Negative Feedback?
Homeostatic control by negative feedback is a process that maintains a stable internal environment in the body by reversing changes that occur from the SET POINT.
> When the factor DEVIATES the set point, a Negative feedback loop is actived to return it back to set point.
What is the Set point in Negative Feedback of Homeostasis?
The set point is an ideal value for a particular factor.
Ex: Body temp 37c
What happens in the body when there is change in Set point?
When a factor deviates from a set point, it is detected by the brain, and corrective mechanisms activate.
The conditions return back to set point and the corrective mechanisms switch off.
Explain Negative feedback on the level of blood Glucose:
If the Glucose level is high, the Pancreas secretes Insulin to convert Glucose into Glycogen, storing it.
If the Glucose level is low, the Pancreas secretes Glucagon to convert Glycogen into Glucose, to increase levels.
What is Type 1 Diabetes?
Type 1 Diabetes is a condition where the body is unable to control blood glucose levels due to LACK OF INSULIN PRODUCTION in the Pancreas.
- This person has high glucose levels.
How is Type 1 Diabetes treated?
It can be treated by injecting Insulin, which prompts the Liver to convert Glucose into Glycogen.
What are the parts of the Skin?
The skin consists of:
- Hairs, Hair erector muscles, sweat glands, Receptors, Sensory Neurones, blood vessels and fatty tissue.
How is temperature controlled by the Skin?
- Temperature change is detected by Thermoreceptors in the brain and skin.
- These receptors send nervous impulses in sensory Neurones to the Brain.
- The Brain responds by sending nervous impulses to Effectors IN THE SKIN.
- Finally these will carry out a response.
What are some mechanisms to maintain a constant body temperature?
Some Mechanisms are:
- Insulation
- Sweating
- Shivering
- Adjusting blood vessels (Vasodilation and Vasoconstriction.
What is Insulation?
Insulation is a way the body reduces heat loss.
This is by the fatty (adipose) tissue in the skin, that acts an insulating layer, preventing excessive heat loss from the body.
How do hair erector muscles respond to high and low body temperatures? (Explain)
> WHEN ITS COLD; Hair Erector muscles contract, causing the skin hairs to stand straight.
- This traps a layer of Air, and since air is an insulator, it helps REDUCE heat loss.
WHEN ITS HOT; Hair Erector muscles relax, causing skin hairs to lie flat.
- This allows Air to circulate, which INCREASES heat loss. (NO INSULATION)
Explain sweating
At high temperatures:
- Sweat glands secrete sweat
- Sweat evaporates off the skin
- Heat is lost
- Body temperature is reduced.
Explain Shivering:
At low temperatures:
- The body shivers
- This is response to rapid muscle contraction to generate heat by respiration of muscles.
- Body temperature is increased.
What is Vasodilaton?
When we feel hot:
The Arterioles widen, increasing blood (flowing through capillaries) near the skin.
- Heat loss is increased.
What is Vasconstriction?
When we feel cold:
The Arteries narrow, constricting blood flow, and reducing the amount of blood (flowing through capillaries) near the skin surface.
- Heat loss is reduced
How is HIGH body temperature controlled by Negative feedback?
The thermoreceptors in brain and skin detect the increase in temperature, sending nerve impulses to the brain, this results in:
- Increased sweating (losing heat)
- Vasodilation
- Skin hairs willl be flat
How is LOW body temperature controlled by Negative feedback?
The thermoreceptors in brain and skin detect the decrease in temperature, sending nerve impulses to the brain, this results in:
- Shivering (generating heat)
- Vasoconstriction
- Skin hairs will be upright
What are the Homeostatic organs (controlled by the brain)
- Kidneys: Regulates water and salts
- Liver: Regulates glucose levels
- Lungs: Regulates O2 and CO2 concentration
- Skin: Regulates Temperature
Why should tissue fluid be kept at narrow limits?
If too concentrated, it would take in water from cells by Osmosis, making the body dehydrated.
If too dilute, too much water leaves the fluid by Osmosis into cells, causing the tissues to become swollen and waterlogged.
What does tissue fluid do?
Tissue fluid supplies or removes substances in the cell membrane.
What is a tropic response/tropism?
Tropic responses are growth movements related to directional stimuli.
ex: light or gravity.
What is Gravitropism?
Gravitropism is a response in which
parts of a plant grow towards or away from gravity.
What is positive and negative Gravitropism?
Positive Gravitropism, is when the plant part grows downwards.
ex: roots
Negative Gravitropism, is when plant part grows upwards.
ex: stem
What is Phototropism?
Phototropism is a response in which
parts of a plant grow towards or away from the direction of light source.
What is Positive and Negative Phototropism?
Positive Phototropism is when the plant faces towards light.
Negative Phototropism is when the light faces away from light.
What is a Clinostat? How does it affect tropic responses?
A Clinostat is a clockwork/electric turntable.
When experimenting for Photo/Gravitropism, the control will be on the Clinostat.
- The Clinostat turns, allows the plant to receive equal gravity/light, so it wouldn’t face the source, resulting as Negative.
What are growth substances in plants?
Growth substances are similar to Hormones in animals.
They are produced in specific regions (parts with actively dividing cells like tips of shoots and roots) and transported to target organs (roots, shoot, buds).
What is Auxin?
Auxin is a growth substance found producing on the tips of roots and shoots.
- They are carried by Active Transport to regions to promote cell enlargement.
What is the chemical name for Auxin?
Indoleacetic acid (IAA)
How does the Auxin control shoot growth?
- Auxin is made in the shoot tip
- It is then transported through the plant.
-It is unequally distributed due to response in light and gravity - Auxin stimulates cell elongation
Explain Auxin in horizontal root that will result in POSITIVE Gravitropism:
The Auxin growth substance will accumulate on the lower side of the root.
- The root tip curves downwards by the weight.
Explain Auxins in horizontal root that will result in NEGATIVE Gravitropism:
If a shoot is horizontal in absence of light, the Auxins accumulate on the lower side due to gravity.
- This causes the lower side to grow faster than upper, so the shoot bends upwards.
Explain Auxin in Positive Phototropism:
Auxins produced at the tip of shoot will move to the shaded side, causing unequal distribution.
- As a result, the cells here will absorb MORE water than on the light side, causing the stem to bend towards light. Because the other side has heavy weight, pushing the plant
Why do Auxins move to shaded areas of a plant?
This is because Auxins are destroyed on the light side.
- Because of this there is unequal distribution.
