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Biology Alevels > Topic 6 > Flashcards

Topic 6 Flashcards

1
Q

What is homeostasis

A

involves using physiological systems to maintain a constant internal environment within fixed limits

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2
Q

Why is maintaining a stable internal temperature and PH important

A

To ensure that the enzymes involved in metabolic reactions are operating at the optimal temperatures

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3
Q

What is negative feedback

A

Used in homeostasis
If the stimulus is above the limits ,then the body will work to reduce it and vice versa

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4
Q

When does blood glucose levels rise

A

After a carbohydrate containing meal

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5
Q

What are the two hormone involved in maintaining blood glucose

A

Insulin

Glucagon

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6
Q

What is the main organ involved in maintaining blood glucose levels

A

Pancreas

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7
Q

What is the area of the pancreas where cells secrete insulin

A

Islets of langerhan

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8
Q

What are the two types of cells which secrete hormones

A

Beta cells secrete insulin

Alpha cells secrete glucagon

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9
Q

What happens when blood glucose levels are too high

A
  1. Pancreas detects the rise in blood glucose
  2. a cells stop secreting glucagon and b cells start secreting insulin
  3. Insulin binds to receptors on liver and muscle cells
  4. Muscle cells are stimulated to take up more glucose
  5. Liver cells are stimulated to take up glucose and initiate glycogenosis
  6. Blood glucose levels drop down
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10
Q

What happmes when blood glucose is too low

A
  1. The pancreas detects a drop in blood glucose
  2. a cells start secreting glucagon and b cells stop secreting insulin
    3.Glucagon binds to receptors on liver cells
  3. This activates glycogenolysis
  4. Liver cells release glucose into the blood
  5. Blood glucose levels return to normal
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11
Q

Define glycogenesis

A

The process of excess glucose being converted to glycogen when blood glucose is too high

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12
Q

Define glycogenolysis

A

1.The hydrolysis of glycogen back into glucose in the liver

  1. Occurs when blood glucose levels are lower than usual
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13
Q

Gluconeogenesis

A
  1. Process of creating glucose from noncarbohydrate stores in the liver
  2. This occurs if all glycogen has been hydrolysed into glucose and your body still needs more glucose
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14
Q

What organ regulates water potential

A

The kidneys

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15
Q

How does the kidneys regulate water potential

A

In the kidneys, water is filtered out of the blood and then reabsorbed so that the water potential of blood can be controlled

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16
Q

Where in the kidneys is water filtered

A

In the nephron

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17
Q

Where is the nephron located

A

Found in the cortex and medulla layers of the kidney

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18
Q

What is the hormone for the regulation of blood glucose

A

The hormone ADH is used in the regulation of blood glucose

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19
Q

Where is ADH secreted

A

It is secreted by the posterior pituitary gland in the brain

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20
Q

What is the role of ADH

A

It controls how permeable the distal convoluted tubule (DCT) and collecting duct is to water which changes the amount of water that is reabsorbed

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21
Q

What happens if blood water potential is too high

A

1.Osmoreceptors in the hypothalamus detect the rise in water potential

2.The posterior pituitary gland releases less ADH into the blood
3.Less ADH results in the DCT and collecting duct becoming less permeable to water so less water is reabsorbed
4.This results in a larger amount of more dilute urine being produced

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22
Q

What happens if blood water potential is too low

A

1.Osmoreceptors in the hypothalamus detect the drop in water potential
2.The posterior pituitary gland releases more ADH into the blood
3.More ADH results in the DCT and collecting duct becoming more permeable to water so more water is reabsorbed
4.This results in a smaller amount of more concentrated urine being produced

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23
Q

How are nerve impulses transmitted

A

Via neurons

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24
Q

What are three types of neurons

A

Motor
Sensory
Relay

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25
Q

What is the role of sensory neurone

A

Sensory neurons transmit impulses from receptors to the CNS

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26
Q

Give two ways person with type 1 diabetes controls blood glucose

A

Treat with insulin

Control diet

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27
Q

Role of all three neurons

A

Sensory : transmits information from receptors to CNS
relay: transmits signals from sensory to motor

Motor : transmits impulses from CNS to an effector

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28
Q

When a neurone is at rest is the inside of cell membrane negative or positive

A

Negative

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29
Q

What is the resting potential

A

-70 mv

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30
Q

How is resting potential maintained

A

By sodium -potassium pumps

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31
Q

Describe the process in how resting potential is maintained

A

Sodium-potassium pumps move sodium out of the neuron and potassium into the neurone

The cell membrane is permeable to potassium but not sodium, so the potassium inside the neuron moves out down its concentration gradient

This means that overall there are more positive charges on the outside of the cell than on the inside which results in the inside being more negative than the outside

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32
Q

How does depolarisation occur

A

When a neuron is stimulated, Na+ voltage-gated channels open so Na+ ions move into the membrane, depolarizing it

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33
Q

How does an action potential occur

A

this depolarization reaches the threshold potential of about -55mV, it is the beginning of an action potential

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34
Q

Describe repolarisation

A

Na+ voltage-gated channels then close and K+ voltage-gated channels open, repolarising the membrane

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35
Q

What is the threshold value

A

-55mV

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36
Q

What is the refractory period

A

The refractory period ensures that the impulse only travels in one direction as the membrane cannot be stimulated

37
Q

What is a myelinated nerve

A

A myelinated nerve is covered by a myelinated sheath which is an electrical insulator

38
Q

What is saltatory conduction

A

Depolarisation only occurs at these Nodes of Ranvier so the impulse jumps from one Node to the next, speeding it up
This is called saltatory conduction

39
Q

What is the gaps between neurons called

A

the Nodes of Ranvier

40
Q

What affects the speed of transmission

A

The bigger the axon diameter, the faster the speed of transmission

Temperature affects the speed of transmission - it is fastest at 40C but decreases at any other temperature

41
Q

What is a synapse

A

A synapse is where an impulse is transferred from one neuron to another

42
Q

Describe the presynaptic neuron

A

The area of the neuron before the synapse is called the presynaptic knob and it is filled with vesicles containing chemicals called neurotransmitters

43
Q

Describe the cholinegic synapse

A

In a cholinergic synapse, the neurotransmitter is acetylcholine

44
Q

Describe the transmission of acetylcholine

A

An action potential reaches the presynaptic knob
This causes Ca2+ voltage-gated channels to open and calcium ions to enter the presynaptic knob
The influx of Ca2+ ions causes vesicles containing the neurotransmitter acetylcholine to fuse with the membrane of the presynaptic knob
Acetylcholine is released into the synaptic cleft and binds with receptors on the postsynaptic membrane
This triggers Na+ ion channels to open which results in Na+ entering the membrane and depolarisation occurring
The acetylcholine in the synaptic cleft is broken down by the acetylcholinesterase enzyme so that the post-synaptic membrane is not triggered multiple times
There are only receptors on the post-synaptic membrane so the impulse only travels in one direction (unidirectionality)

45
Q

Describe the pacinian corpuscle

A

it is a mechanoreceptor (ie detects pressure and vibrations) and it is found in the skin

46
Q

Where is the pacinian corpuscle

A

A Pacinian Corpuscle is made up of the end of a sensory neuron wrapped in layers of connective tissue called lamellae

47
Q

What does the pacinian corpuscle do when a stimulus is applied

A

When a stimulus is applied, eg a nudge, the lamellae deform and press on the sensory nerve ending
This causes sodium ion channels called stretch-mediated sodium ion channels to open and sodium ions to enter the cell
This causes a change in the charge of the cell called a generator potential

48
Q

How is action potential created in the pacinian corpuscle

A

If this generator potential reaches above a certain threshold, it will form a nerve impulse known as an action potential

49
Q

Where are photoreceptors

A

Another example of a receptor is a photoreceptor (light receptor) in the retina of the eye.

50
Q

What does photoreceptors do

A

photoreceptor cells that detect light

51
Q

What are two types of photoreceptors

A

rods and cones

52
Q

Describe Rod cells

A

Rods are very sensitive to light but they have low visual acuity. They can only detect monochromatic light (black and white)

53
Q

Why do rod cells only detect monochromatic light

A

this is because many rods join to one neuron so the signal is amplified

but the light from two close points cannot be told apart

54
Q

Describe cons cells

A

Cones are less sensitive to light but they have high visual acuity. They can detect light in colour (red, green, and blue)

55
Q

Why do cone cells detect light in colour

A

this is because one cone joins to one neuron so the signal is weaker but the light from two close points can be told apart

56
Q

How do organisms survive by responding to their internal environment

A

Internal: ensuring that body temperature and pH are optimal for metabolism

57
Q

How do organisms survive by responding to their external environment

A

External: avoiding harmful environments or changing by responding to changes in the environment.

58
Q

How do plants respond to external stimuli

A

Plants respond to external stimuli like gravity and light

Plants grow towards the light to maximize photosynthesis

They sense gravity so that shoots and roots grow the correct way

59
Q

What is tropism

A

A plant’s growth response to a stimulus is called a tropism.
a positive tropism is a growth towards a stimulus
a negative tropism is growth away from a stimulus

60
Q

Describe phototropism (negative and positive)

A

Phototropism is the growth response of plants to lights

shoots have a positive phototropic response: they grow towards the light

roots have a negative phototropic response: they grow away from the light

61
Q

Describe gravitropism

A

Gravitropism is the growth response of plants to gravity

shoots are negatively gravitropic: they grow away from the direction of the pull of gravity

roots are positively gravitropic: they grow towards the direction of the pull of gravity

62
Q

What are growth factors

A

Growth factors are chemicals that speed up or slow down plant growth

63
Q

Describe the role of auxins

A

Auxins are a group of growth factors that stimulate growth by causing cells to elongate

64
Q

Describe how concentration of auxin effect plant elongation

A

In shoots, high concentrations of auxin cause cell elongation but in roots, high concentrations of auxin inhibit cell elongation

65
Q

What is IAA

A

IAA (Indoleacetic Acid) is a type of auxin that is produced in the shoots of flowering plants

It moves around the plants to control tropisms

66
Q

How does IAA work in phototropism

A

Phototropism: IAA accumulates on the more shaded side of shoots and roots

This causes shoots to bend towards the light and roots to bend away from the light

67
Q

How does IAA work in gravitropism

A

Gravitropism: IAA accumulates on the underside of shoots and roots
This causes shoots to bend upwards and roots to bend downwards

68
Q

Describe taxes

A

Tactic responses (taxes) are when organisms move towards or away from a directional stimulus (eg light)

69
Q

Describe taxes

A

Tactic responses (taxes) are when organisms move towards or away from a directional stimulus (eg light)

70
Q

How do woodlice have a phototaxic response

A

woodlice have a phototaxic response (taxes response to light): they move away from a light source

this helps them to remain in dark conditions that will keep them safe from predators

71
Q

What is kineses

A

Kinetic responses (kineses) are when organisms move in response to a non-directional stimulus.

72
Q

How do woodlice respond to humidity

A

woodlice have a kinetic response to humidity: in a humid environment, they move and turn less often so they will stay where they are

but in a dry environment, they move and turn more so that it is more likely they will move into a humid environment

73
Q

How is the cardiac muscle a myogenic muscle

A

Cardiac muscle is a myogenic muscle: it will contract on its own without a nerve impulse

74
Q

Describe the role of a pacemaker

A

The heart has a pacemaker that regulates these contractions called the SAN (sinoatrial node)

75
Q

Describe how impulses travel from the atria to the ventricles

A

The SAN sends out a wave of electrical activity over the atria of the heart which causes the left and right atria of the heart to contract at the same time
The ventricles of the heart are separated from the atria by a band of non-conducting tissue, so the signal passes through the AVN (atrioventricular node)
the AVN has a slight delay which allows the atria to fully empty before the ventricles contract
The impulse travels from the AVN down the bundle of His (a bundle of nerves that are found in the septum or middle of the heart) and into the Purkyne tissue
The Purkyne tissue causes the ventricles to contract simultaneously from the bottom up

76
Q

What is the role of the sinoatrial node

A

The SAN sends out a wave of electrical activity over the atria of the heart which causes the left and right atria of the heart to contract at the same time

77
Q

What is the advantage of the slight delay of the AVN

A

the AVN has a slight delay which allows the atria to fully empty before the ventricles contract

78
Q

What is the flow of impulses from atria to ventricle

A

Sinoatrial node —> atrioventricular node —> bundle of his-> purkyne tissue

79
Q

What is the rate of SAN controlled by

A

The rate that the SAN sends out impulses is unconsciously controlled by the brain and the autonomic nervous system

80
Q

What is the role of the sympathetic and the parasympathetic

A

The sympathetic nervous system helps the body get ready for action while the parasympathetic nervous system calms it down

81
Q

What is the role of the medulla oblongata in controlling SAN

A

medulla oblongata controls the SAN
The medulla oblongata receives impulses from baroreceptors (pressure receptors) and chemoreceptors (chemical receptors)

82
Q

Where are baroreceptors found

A

Baroreceptors are found in the aorta and carotid arteries (in the neck) and are stimulated by high and low blood pressure

83
Q

What do baroreceptors do when blood pressure is high

A

If blood pressure is too high, baroreceptors send impulses to the medulla oblongata which passes them to the parasympathetic nervous system. This causes the SAN to reduce heart rate

84
Q

What do chemoreceptors do and where do you find them

A

Chemoreceptors are found in the aorta, the carotid arteries, and the medulla and respond to changes in O2 concentration and blood pH

85
Q

What do chemoreceptors do if blood CO2 is too low

A

If blood CO2 is too low (which causes blood pH to be high), chemoreceptors send impulses to the medulla oblongata which passes them to the parasympathetic nervous system. This causes heart rate to decrease

86
Q

What happens if blood O2 is too low

A

If blood O2 is too low (which causes blood pH to be low), then impulses are sent along the sympathetic nervous system which increases heart rate.

87
Q

What happens if blood O2 is too low

A

If blood O2 is too low (which causes blood pH to be low), then impulses are sent along the sympathetic nervous system which increases heart rate.

88
Q

Exercise increases heart rate
Describe role of receptors and the nervous system in this process

A

Chemoreceptors detect rise in CO2

Send impulses to cardiac centre
More impulses in the SAN
By the sympathetic

Biology Alevels (7 decks)

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