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Biology 9.3 > `Homeostasis > Flashcards

`Homeostasis Flashcards

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1
Q

How is the intrinsic rhythm of the heart controlled

A

By impulses initiated in the sinoatrial node (SAN) and then spreads through the atrioventricular node (AVN) and the bundle of his to give a regular rhythm

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2
Q

What is the response of the heart to change as a result of

A

A result of the negative feedback system

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3
Q

When your body demands more glucose and oxygen what is one way your heart can respond

A

1)The rate at which the heart beats can increase and the volume of blood pumped at each heartbeat

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4
Q

how can the cardiac volume be increased

A

By a more efficient contraction of the ventricle

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5
Q

How can you calculate the cardiac output

A

Cardiac output = cardiac volume X heart rate

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6
Q

What happens to the heart during exercise

A

The heart rate begins to increase before the exercise begins. The cardiac volume increases more slowly, as it becomes clear from the changes in the body that exercise is going to continue

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7
Q

What is most of the nervous control in the heart

A

By the autonomic nervous system

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8
Q

How are nerve impulses sent to the cardiac centre

How does the cardiac centre respond

A

Chemicals, stretch and pressure receptors in the lining of the blood vessels and the chambers of the heart send nerve impulses to the cardiac centre

By sending impulses to the heart along parasympathetic and sympathetic nerves

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9
Q

How in the SAN stimulated

A

Nerve impulses travel down the sympathetic nerve from the cardiac centre in the brain to the heart to release noradrenaline

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10
Q

What does the stimulation of the SAN cause

A

an increase in the frequency of the signals from pacemaker region so heartbeats faster

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11
Q

What do impulses in the parasympathetic nerve release

what effect does this have

A

acetylcholine which inhibits SAN and slows the heart down

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12
Q

where are baroreceptors found

A

In the sinuses of the carotid arteries in the neck and on the aorta

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13
Q

What are baroreceptors important for

A

In feedback control of the heart rate during exercise

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14
Q

Explain what baroreceptors do during exercise

A

When exercise begins blood vessels dilate (vasodilation) in response to hormone adrenaline and blood pressure falls

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15
Q

What happens when stimulation from baroreceptors are reduced

A

The cardiac control centre immediately sends signals along the sympathetic nerve to stimulate the heart rate and increase blood pressure again by vasoconstriction

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16
Q

Explain what baroreceptors do when Excercise is stopped

A

Blood pressure in arteries increases as the heart continues to pump harder and faster than it needs to so baroreceptor is stretched. They send more sensory nerves via the parasymapthetic system to slow down the heart causing widening blood vessels

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17
Q

Where are chemoreceptors found

A

in the wall of the aorta and carotid arteries

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18
Q

what are chemoreceptors sensitive to

A

Carbon dioxide levels

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19
Q

What do chemoreceptors detect

Explain how this happens

A

As the level of CO2 increases the PH decreases which is detected by the aorta and carotid chemoreceptors
They send impulses along sensory neurons and to the cardiac control centre in the medulla, this increases the impulse traveling down the sympathetic nerve

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20
Q

What does the chemoreceptor do for the heart

A

It reduces the number of impulses to the cardiac centre reducing heart rate and makes it go back to the intrinsic rhythm

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21
Q

What does adrenaline stimulate

A

The cardiac centres in the brain, increasing the impulses in the sympathetic neurons supplying the heart, increasing frequency off excitation and so increasing the heart rate

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22
Q

What is osmoregulation

A

The maintenance of the osmotic potential in the tissues of a living organism within narrow limits by controlling water and salt concentrations

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23
Q

What are the cells of land-living mammals surrounded by

A

Tissue fluids that come from the blood capillaries

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24
Q

How can osmotic damage of cells be prevented

A

By controlling blood potential of blood the body can control the water potential of the tissue fluid

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25
Q

What’s the main organ involved in the water balance of the body

A

The kidney

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26
Q

What does lover play an important role in

A

In the deamination of excess amino acids in protein metabolism

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27
Q

What are hepatocytes and what does it do

A

liver cells and they deaminate excess amino acids

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28
Q

What do hepatocytes do to amino acids

A

They remove amino acid groups and convert it first to ammonia and then less toxic urea, which can be excreted by the kidney

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29
Q

What is the ornithine cycle

A

The process by which the ammonia produced from deamination of proteins

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30
Q

How is Osmoregulation brought about

What does it help us do

A

By the kidneys, which is more concentrated than the body fluids.

conserve water

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31
Q

How does the kidney look in humans

A

reddish brown organ attached to the back of the abdominal cavity
surrounded by a thick layer of fat (protects them from mechanical damage)

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32
Q

What do kidneys do

A

control the water potential of the blood that passes through them

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33
Q

Where Is the urine stored

A

in the bladder

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34
Q

What are the two main roles of the kidney

A

Excretion and osmoregulation

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35
Q

What are the three main functions carried out by the kidney in its osmoregulation role

A

Ultrafiltration, selective reabsorption and tubular secretion

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36
Q

What are nephrons

A

microscopic tubules that make up each kidney

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37
Q

What are the two main nephrons

what function do they carry out

A

Cortical nephrons
They have a loop of Henle that only just reaches into the medulla

Juxtamedullary nephrons
Have loop of Henle that penetrates right through the medulla
(particularly efficient for producing concentrated urine)

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38
Q

What’s the first stage of osmoregulation

What is it responsible for

A

Ultrafiltration

formation of tissue fluids

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39
Q

Why does ultrafiltration occur

A

Due to the combination of very high blood pressure in the glomerulus.

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40
Q

What makes up the malpighian body

A

The glomerulus and Bowmans capsule

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41
Q

Why does high blood pressure develop in the glomerular capillaries

A

The diameter of the blood vessel coming into the glomerulus is greater than that of the blood vessels leaving

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42
Q

What do the cells of Bowman’s capsule next to the capillaries act as

A

an additional filter

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43
Q

What are podocytes

A

Special cells that make up the wall of the capsule

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44
Q

What are pedicles

A

Extensions of the podocytes that wrap around the capillaries, forming slits that ensure any cells, platelets or large plasma proteins that have left the capillary do not get through into the tubule itself

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45
Q

What does the filtrate that enters the capsule contain

A

glucose, salt, urea and man other substances

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46
Q

Why is ultrafiltration described as passive and indiscriminative

A

it removes urea from the blood and but also removes a lot of water, glucose salt, and other substances

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47
Q

Why is glucose never ever excreted

A

It’s needed for cellular respiration

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48
Q

What is the main function if the kidney tubule after the ultrafiltrate has entered the nephron

A

To return to the most of what has been removed from the blood back to its rightful place

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49
Q

Wat does microvilli do when on the lining on the cell

A

Increases the surface area through which substances can be absorbed

50
Q

What happens by the time the filtrate reaches the loop of Henle

A

it is isotonic with the tissue fluids that surround the tubules

51
Q

Where is the loop of Henle found

What does it work closely with

A

Found in the medulla of the kidney

works with a network of capillaries known as vasa recta

52
Q

What does the Vecta recta and Loop of Henle do

A

They create water potential gradient between filtrates and the medullary tissue fluid enables water to be reabsorbed from the distal convoluted tubule and collecting duct

53
Q

Why is there a high concentration of sodium and chlorine in the medulla

What does this create

A

Due to the flow of fluid in opposite directions in the adjacent limbs of the loop of Henle

countercurrent multiplier

54
Q

What is a countercurrent multiplier

A

a biological system that uses active transport to set up and maintain concentration gradients

55
Q

What do the changes that take place in the descending limb of the loop of Henle depend on

A

On the high concentration of sodium and chloride ios in the tissue of the medulla, and these are the result of events in the ascending limb of the loop

56
Q

What is the descending limb permeable of

A

Water but it isn’t permeable of sodium and chloride ions

57
Q

Explain how the descending limb works

A

The fluid entering is isotonic with the blood
As it travels down the lib into the medulla, the external concentration of sodium and chloride ions in the tissue fluid of the medulla and the blood in the vasa recta is higher an higher.
Water moves out a concentration gradient
It then moves into the blood of the vasa recta down the water potential
when the fluid reacher hairpin bend at the bottom of the loop it is very concentrated and hypertonic to the arterial blood

58
Q

What is the ascending limb permeable to

A

Sodium and chloride ions but no water

59
Q

Explain how the ascending limb works

A

Sodium and chlorine ions move out of the very concentrated fluid in the loop of Henle into the tissue fluid of the medulla down a concentration gradient
The thicker section of the ascending limb I also impermeable to water but sodium and chloride ions are actively pumped out of the tube in the tissue fluids of the medulla and the blood of the vasa recta
this gives tissues of medulla very high sodium and chloride ion concentration and causes water to pass out the descending limb
Due to the fact that ascending limb is impermeable to water the fluid in ascending limb becomes less concentrated

60
Q

What is distal convoluted tubule permeable to and to what extent

A

Water

depends on the level of antidiuretic hormone (ADH)

61
Q

What does the collecting duct do

A

balances water

62
Q

Why is water removed from the medulla

What does this allow

A

Because of the increase in the concentration of sodium ions

This allows for the creation of hypertonic urine

63
Q

Where is urine first collected

A

In the pelvis of the organ and then passed to the bladder

64
Q

What is the urethra

A

The tube in which urine passes out the body

65
Q

Give some reasons why kidneys produce such high concentrated urine

A

1) A relatively large proportion of juxtamedullary nephrons
2) A long loop of Henle
3) Higher no. of foldings on the cell membrane
3) Higher no. of mitochondria

66
Q

How is the osmotic potential kept at such a narrow range

A

By balancing water and salt taken in by eating and drinking with the water and salts lost by sweating

67
Q

Where is ADP produced and where is it secreted

A

Produced in the hypothalamus and secreted into the posterior lobe

68
Q

How does ADP get across the membrane

A

It binds to a specific receptor and, triggering a reaction forming in cAMP as a second messenger

69
Q

What does the cAMP do

A

Sets up a series of reactions that cause vesicles within the cell lining the tubules to move out, and fuse with, the cell membrane

70
Q

What does the amount of ADH released control

A

the number of channels that are inserted

71
Q

What happens when ADH levels drop

A

cAMP levels drop and water channels are within from the membrane and repackaged in vesicles.

72
Q

What happens when the concentration of inorganic ions in the blood rises

A

The water potential becomes more negative

73
Q

What do osmoreceptors in the hypothalamus detect

A

They detect an increasingly negative water potential in the blood

74
Q

How do osmoreceptors detect negative water potential

A

They send nerve impulses to the posterior pituitary, which in turn releases stored ADH in the blood. the ADH is picked up by receptors in the cell of the kidney tubules.ADH increases the permeability of the distil convoluted tubule and the collecting duct to water. Water leaves the tubules by osmosis into the surrounding capillary network

75
Q

When does water potential become more negative

A

When it becomes more dilute

76
Q

What is the most common form of diabetes

What is it a result of

A

Diabetes mellitus

insufficient insulin being produced

77
Q

What is the name of a rare form of diabetes

How is it caused

A

diabetes insipidus

When an individual produces large volumes of ADH

78
Q

What does lack of ADH cause?

A

The distal convoluted tubules and collecting ducts are permanently impermeable in water

79
Q

What is thermoregulation

A

The way in which organisms control their internal body temperature

80
Q

What kind of surface area for small animals have

A

large surface-area-to-volume ratio

81
Q

Give an example of how animals cool down

A

By the evaporation of water from the body surfaces

82
Q

how can energy be transferred to or from an environment

A

By radiation

83
Q

Where are convection currents set up

A

They are set up around relatively hot objects, so adaptations to prevent cooling by these currents are common in animals

84
Q

Why do land habitat animals need to control body temperature

A

Either to avoid damage to their cells or to enable them to give an active life

85
Q

How are animals often classified

A

According to the main mechanisms of temperature control as either endotherms or ectotherms

86
Q

What are endotherms

A

Organisms that rely on their own metabolic processes to provide at least some warming and usually has a body temperature

87
Q

What are endotherms adapted to do

A

Adapted to conserve body temperature and also take advantage of warmth from the environment when possible

88
Q

What are Ectotherms

A

Organisms that rely heavily on the external environment to control their body temperature

89
Q

What do ectotherms have

A

They usually have behavioral and structural modifications that take advantage of the environment

90
Q

How do ectotherms cool down

A

Move to shade, into water or mud

91
Q

What is one big advantage that ectotherms carry

A

They need less food

The advantage of environments that don’t have

92
Q

What is the main example of endotherms

A

Mammals

93
Q

What is the difference between human and other mammals in terms of temperature regulation

A

We can help manipulate the temperature by using things like heaters and air conditioners

94
Q

What is the major homeostatic organ involved in thermoregulation in most endotherms

A

The skin

95
Q

What does the skin help prevent

A

overheating in a number of ways

96
Q

How does cooling by radiation, convection, and conduction take place

A

From the blood flowing through the skin

97
Q

How is the cooling controlled

A

VIA the arteriovenous shunt

98
Q

What happens when you exercise or external temp rises

A

The shunt is closed, which allows more blood to flow through the capillaries at the surface of the skin and vasodilation occurs

99
Q

What happens to your skin hairs when you’re hot

A

The erector pili muscles, which are attached to the hair follicles, are relaxed and the body hairs are flat

100
Q

What happens as sweat is released

A

colling akes place as the water evaporates

101
Q

What is vasoconstriction

A

The narrowing of the blood vessels by the relaxation of their muscle walls, increasing blood flow

102
Q

What is vasodilation

A

The widening of the blood vessels by contraction of their muscle walls, reducing blood flow

103
Q

How does the body keep cool

A 
.Sweat production is reduced
.Cooling by evaporation is reduced
.Erector pili is contracted
.Metabolic rate of the body speeds up
.involuntary contractions, shivering
104
Q

What are the two types of receptors in thermoregulation

A

Receptor in the brain (monitors temp of the blood)

Receptors in the skin (Change in external temperature)

105
Q

Where are the temperature receptors located in the brain

A

Hypothalamus

106
Q

What happens when the temp of the blood flowing the body increases

A

The thermoregulatory centre is activated and sends impulses along the autonomic motor nerves to effectors that increase the blood flow through the skin and sweating

107
Q

What are the main things that happen when blood temperature increases

A

.The erector pili muscles are relaxed so hair lie flat

.The metabolic rate may be reduced to lower the amount of warming in the body

108
Q

What are the main things that happen when blood temperature decreases

A

The thermoregulatory centre reacts by sending nerve impulses along the autonomic motor nerves to effectors
.Reduction in the blood flow through the capillaries in the skin, along with with the reduction n the production of sweat and contractions
.The erector pili muscles raise the hairs
.shivering etc takes place (involuntary contractions)

109
Q

What have some mammals and birds living in cold environments developed

A

Countercurrent exchange systems in their limbs that allow body temperature to be conserved
Arterial blood is cooled and venous blood is warmed

110
Q

How can the problem of cold environments be overcome

A

Hibernation

111
Q

What happens during hibernation

A

Animals go into a deep sleep and metabolic rate is decreased. Then the core temperature is greatly lowered

112
Q

What brings animals out of hibernation

A

Higher temperature and longer days

113
Q

After hibernation why does the metabolic rate need to increase quickly

A

So the animal can find something to eat quickly without being preyed on

114
Q

What is a big problem for animals in hot environments

A

Being able to cool down

115
Q

How do they save a lot of water in hot environments

A

They do not sweat

116
Q

How is the brain cooled in animals that live in extremely hot environments

A

A countercurrent exchange system is put into place

117
Q

Give examples of behavioral modifications that help modify both endotherms and ectotherms body temperature

A

1) Basking (Bask in the sun when body temperature is falling)
2) Sheltering
3) Evaporating
4) moving in and out of the sun

118
Q

What is aestivation

A

One extreme physiological adaptations for avoiding hot, dry conditions

119
Q

What happens during aestivation

A

Their metabolic rate slows right down and becomes completely inactive
often bury themselves in mud

120
Q

What animals aestivate

A

molluscs, frogs, crocodiles to lungfish and snakes

Biology 9.3 (1 decks)

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