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Biology final > Communication and homeostasis Module 5 > Flashcards

Communication and homeostasis Module 5 Flashcards

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1
Q

What’s a stimulus?

A

Any change in the internal or external environment

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2
Q

What do receptors do?

A

Detect specific stimuli

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3
Q

What are effectors?

A

Cells that bring about a response to a stimulus, to produce an effect

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4
Q

Example of cell signalling between adjacent cells?

A

Cells in the nervous system communicate secreting chemicals called nuerotransmiters, which send signals to adjacent cells such as nerve cells or muscle cells

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5
Q

Example of cell signalling between long distant cells?

A

Hormonal system, releases chemicals called hormones which travel in the blood and act on distant cells

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6
Q

What is homeostasis and why is it important?

A

Homeostasis, is the maintenance of a constant internal environment

Provides right condition for cells to function

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7
Q

Describe a homeostatic systems response to a change via negative feedback?

A

Receptors detect when a level is too high or too low, and the information is communicated to effectors via the nervous system or hormonal system

The effectors respond to counteract the change - bringing the level back to normal

= negative feedback mechanism

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8
Q

Can negative feedback mechanisms cope with huge changes?

A

NO

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9
Q

What do sensory neurons do?

A

Transmit nerve impulses from receptors to the central nervous system (brain and spinal cord)

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10
Q

What do relay neurons do?

A

Transmit nerve impulses between sensory neurons and motor neurons

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11
Q

What do motor neurons do?

A

Transmit nerve impulses from the CNS to the effectors

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12
Q

Describe the general story from stimulus to response?

A

Stimulus

Receptors

Sensory neuron takes information to CNS where it’s processed and decides what response is required

Motor neurons to effectors

Response

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13
Q

What does the nervous system send information as?

A

Nerve impulses

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14
Q

Why are sensory receptors known as tranducers?

A

They convert Stimulus energy (eg.light, chemical) into the form of nerve impulses

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15
Q

Describe how sensory receptors convert stimulus energy into nerve impulses?

A

When a Nervous system receptor is in it’s resting state, there’s a difference in charge between the inside and the outside of the cell - so there’s a voltage across the membrane which is known as potential difference

This potential difference is generated by ion pumps and ion channels

The potential difference when a cell is at rest is called the resting potential

When a stimulus is detected, the cell membrane is excited and becomes more permeable, allowing more ions to move in and out of the cell - altering the potential difference

The change in potential difference due to a stimulus is called the generator potential

A bigger stimulus excites the membrane more, causing a bigger movement of ions and a bigger change in potential difference = larger generator potential

If the generator potential is large enough (reaches the threshold level) it will trigger an action potential (nerve impulse) along a neurone

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16
Q

Describe the mechanoreceptor pacinian corpuscles?

A

They detect mechanical stumuli, eg pressure and vibrations

They are found in your skin, and contain the end of a sensory neuron called a sensory nerve ending, which is wrapped in lots of layers of connective tissue called lamellae

When a Pacinan corpuscle is stimulated, the lamellae are stimulated, the lamellae are deformed, and press on the sensory nerve ending

Causing deformation of the stretch mediated sodium channels in the sensory neurons cell membrane

So the Sodium ion channels open and the sodium ions diffuse into the cell, creating a generator potential which if passes the threshold will cause an action potential

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17
Q

What do dendrons / dendrites do?

A

Carry nerve impulses towards the cell body

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18
Q

What do axons do?

A

Carry nerve impulses away from the cell body

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19
Q

Structure of a sensory neuron in direction of the impulse?

A

Connects to receptor cells via dendrites, which then goes on to one long dendron which connects to the cell body

Then one short axon carries impulses from the cell body to the CNS

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20
Q

Describe the structure of a relay neuron in direction of the impulse?

A

Have many short dendrites that carry nerve impulses from the sensory neurons to the cell body

And many short axons that carry nerve impulses from the cell body to motor neurons

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21
Q

Describe the structure of a motor neuron in the direction of the impulse?

A

Have many short dendrites that carry nerve impulses from the CNS, to the cell body

And one long axon, which carries the nerve impulses from the cell body to effector cells

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22
Q

Describe how neuron cell membranes are polarised at rest?

A

The outside of the membrane is more positively charged compared to the inside, as there more positive ions outside than in = polarised as difference in charge

Resting potential = -70mV

The resting potential is created and maintained by Sodium Potassium pumps (SOPI, 2 Sodium out, 3 Potassium in)

Sodium can’t diffuse back in, as there are no ion channels for it, but there are potassium ion channels so the K+ ions diffuse back out

Making it more positive on the outside than the inside

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23
Q

Describe the process of a neuron cell membrane becoming depolarised when stimulated and an action potential being generated?

A

The stimulus excites the neuron cell membrane, causing Na+ ion channels to open, to membrane has become more permeable to Na+ ions, so they diffuse into the neuron down a electrochemical gradient. making the inside of the neuron less negative

If the potential difference reaches the threshold (around -55mV), voltage gated Na+ channels open. More Na+ ions diffuse into the neurone.

This is positive feedback

At a potential difference of around -+30mV, the Na+ ion channels close and voltage gated K+ ion channels open. The membrane is now more permeable to K+, so they diffuse out down a concentration gradient.

This is repolarisation- and is a negative feedback process

Hyperpolarsiation - K+ ion channels are slow to close, so there is a slight overshoot, where too many K+ ions diffuse out of the nueron, the potential becomes more negative than the resting potential (less than 70mV)

Resting potential - the ion channels are reset, the SOPI pumps returns the membrane to it’s resting potential

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24
Q

What’s a positive feedback mechanism do?

A

Amplify a change from the normal level

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25
Q

Example of positive feedback in the blood?

A

When you have a wound, platelets are activated which releases a chemical that activates more platelets, which forms a blood clot at the site

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26
Q

Describe how the action potential moves along the neuron as a wave of depolarisation?

A

When an action potential happens, some of the sodium ions that enter the neuron diffuse sideways

This causes sodium ion channels in the next region of the neuron to open and Na+ ions to diffuse into that part

This causes a wave of depolarisation to travel along the nuerone

The wave moves away from the parts of the membrane in the refractory period, because these parts can’t fire an action potential

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27
Q

What is the refractory period?

A

After an action potential the neurone cell membrane can’t be excited again straight away, as channels are recovering

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28
Q

What does a bigger stimulus cause?

A

More frequent impulses to the brain, (not a larger voltage)

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29
Q

In the peripheral system, what are myelinated nuerones?

A

Nuerones with a myelin sheath made up of schwann cells which is an electrical insulator

Between the Schwann cells are tiny patches of bare membrane called the nodes of ranvier, Na+ ion channels are concentrated here

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30
Q

Why do action potentials go faster in myelinated neurones?

A

Depolarisation only occurs at the nodes of ranvier (where sodium ions can get through the membrane),

The neurons cytoplasm conducts enough electrical charge to depolarise the next node, so the impulse jumps from node to node

This is called salatory conduction and it’s really fast

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31
Q

How does an impulse travel along a non-myelinated nueron?

A

The impulse travels along the whole length of the axon membrane

32
Q

What’s a synapse?

A

The junction between a neuron and another nueron, or between a neuron and an effector cell

33
Q

What’s the tiny gap between the cells at a synapse called?

A

Synaptic cleft

34
Q

What does the presynaptic neuron have a swelling called and what does it contain?

A

Has a swelling called a synaptic knob, which contains synaptic vesicles filled with chemicals called neurotransmitters

35
Q

What happens when an action potential reaches the end of a nuerone?

A

Causes neurotransmitters to be released into the synaptic cleft, they then diffuse across the postsynaptic membrane and bind to specific receptors

36
Q

What’s the pre synaptic and post synaptic membrane?

A 
Pre = before the synapse
Post = after the synapse
37
Q

What happens when the neurotransmitters bind to receptors on the post synaptic membrane?

A

They might trigger an action potential (in a neuron)
Cause muscle contraction (in a muscle cell)
Cause a hormone to be secreted from a gland cell

38
Q

Describe exactly in 3 main steps how neurotransmitters transmit nerve impulses between neurones?

A

An action potential arrives at the synaptic knob of the presynaptic neurone
The action potential stimulates voltage gated Ca2+ in the presynaptic neuron to open
Ca2+ diffuses into the synaptic knob

The influx of calcium ions into the synaptic knob, causes the synaptic vesicles to move to the presynaptic membrane, they then fuse with the presynaptic membrane
The vesicles release the neurotransmitter into the synaptic cleft via exocytosis

The nuerotransmitter diffuses across the synaptic cleft and binds to specific receptors on the post synaptic membrane
Causing Na+ ion channels in the postsynaptic neuron to open
The influx of Na+ in the postsynaptic membrane causes depolarisation. An action potential on the postsynaptic membrane is generated if the threshold is achieved

Neurotransmitter is removed from synaptic cleft so the response doesn’t keep happening

39
Q

What’s synaptic divergence?

A

When one nuerone connects to many neurones information can be dispersed to different parts of the body

40
Q

What’s synaptic convergence?

A

When many nuerones connect to one nuerone, information can be amplified

So stimuli may arrive from different sources

41
Q

What’s spatial summation, and how does it finely tune the nervous response?

A

When neurones converge, the small amount of neurotransmitter released from each nuerone can be enough altogether to reach the threshold potential in the postsynaptic neurone and trigger an action potential

42
Q

What’s temporal summation, and how does it finely tune the nervous response?

A

Where 2 or more nerve impulses arrive in quick sucession from the same presynaptic neurone. which makes the action potential more likely, as more neurotransmitter has been released

43
Q

What do synapses make sure on the direction of transmitions?

A

That they only go one way

44
Q

What is the hormonal system made up of?

A

Endocrine glands and hormones

45
Q

What are endocrine glands?

A

Groups of cells that are specialised to secrete hormones

46
Q

Whar are hormones?

A

Chemical messengers

They are either proteins or steriods

47
Q

How can endocrine cells be stimulated to secrete hormones?

A

Change of concentration of a specific substance

Or electrical impulses

48
Q

How do hormones travel around the body?

A

They diffuse into the blood

49
Q

Describe a very basic story of hormones acting on the liver target cells?

A

Stimulus- low blood glucose concentration

Receptors on pancreas cells detect the low blood glucose concentration

The pancreas releases the hormone glucagon into the blood

Effector step - Target cells in the liver which have specific receptors to the hormone, detect the glucagon, and convert glycogen into glucose

Response - Glucose is released into the blood, so glucose concentration increases

50
Q

Describe the process of adrenaline acting as the first messenger on cells?

A

Adrenaline binds to specific receptors on the cell membrane

When adrenaline binds it activates an enzyme in the membrane called adenylyl cyclase

Activated adenylyl cyclase, catalsyes the production of a second messenger called cyclic AMP (cAMP) from ATP

cAMP activates a cascade of enzyme controlled reactions, which makes more glucose available to the cell, by catalysing the breakdown of glycogen into glucose

51
Q

Describe where adrenal glands are found, and their structure?

A

They are endocrine glands, found just above the kidneys

Each adrenal gland has an outer part called the cortex and an inner part called the medulla

52
Q

Function of the cortex in the adrenal glands?

A

Secretes steroid hormones such as cortisol and aldosterone when you are stressed

Effects of these are:
Stimulating the breakdown of proteins and fats into glucose, increasing the amount of energy available so the brain and muscles can respond to the situation

Increasing blood volume and pressure by increasing the uptake of sodium ions and water by the kidneys

Supressing the immune system

53
Q

Describe the function of the medulla in the adrenal glands?

A

Secretes catechloamine (modified amino acid) hormones such as adrenaline and noradrenaline when you stressed

Effects are:
Increase in heart and breathing rate
Cuasing cells to break down glycogen into glucose
Constricting some blood vessels, so that blood is diverted to the brain and muscles

54
Q

Where is the pancreas found?

A

Bellow the stomach

55
Q

Describe what islets of langerhan are and their function?

A

They are areas of the pancreas that contain endocrine tissue, and are found in clusters around blood capillaries, so they can secrete hormones directly into the blood

They are made up of Alpha cells that secrete a hormone called glucagon

And beta cells which secrete a hormone called insulin

Which both help to control blood glucose concentration

56
Q

Describe what an ectotherm is an their 4 features?

A

Reptiles and fish

Can’t control their body temperature internally - so they control their body temperature by changing their behaviour

So their internal temperature is dependent on their external temperature

Activity levels depend on the external temperature more active in higher temps and less active in lower temps

They have a variable metabolic rate, and they generate very little heat themselves

57
Q

Describe what an endotherm is and 4 features of them?

A

Mammals, birds

Control body temperature internally via homeostasis, and also by behaviour

Their internal temperature is less affected by the external temperatures

Their activity level is not dependent on the external temperature

They have a constantly high metabolic rate and they generate a lot of heat from metabolic reactions

58
Q

3 mechanisms to reduce body temperature?

A

Sweating
Hairs lie flat
Vasodilation

59
Q

Describe how Sweating reduces body temperature?

A

More sweat is secreted from sweat glands when the body is too hot, the water evaporates and takes heat away from the body

60
Q

Describe how hairs lying flat reduces body temperature?

A

When it’s hot erector pill muscles releax, so the hairs lie flat, less air is trapped, so less insulation and heat can be more easily lost

61
Q

Describe how vasodilation reduces body temperature?

A

Arterioles near the surface of the skin dilate, more blood flows through the capillaries in the surface layers of the dermis, so more heat is lost from the skin by radiation, and the temperature is lowered

62
Q

4 mechanisms which increase body temperature?

A

Shivering
Hairs stand up
Vasoconstriction
Hormones

63
Q

Describe how shivering increases body temperature?

A

Muscles contract in spasms, making the body heat up from increased respiration

64
Q

Describe how hairs standing up increases body temperature?

A

Erector pili muscles contract when it’s cold, making the hairs stand up, the traps more air for insulation

65
Q

Describe how vasoconstriction increases body temperature?

A

When it’s cold aterioles near the surface of the skin constrict, so less blood flows through the capillaries, in the surface layers of the dermis. Reducing heat loss

66
Q

Describe how hormones increase body temperature?

A

Adrenaline and thyroxine increase metabolism so more heat is produced

67
Q

Describe how the hypothalamus controls body temperature in mammals?

A

The hypothalamus (part of the brain) receives information about the temperature from thermoreceptors ( the ones in the hypothalamus detect internal temperature, and the ones in the skin (peripheral thermoreceptors detect external temperature

Thermoreceptors send impulses along sensory neurons to the hypothalamus, which sends impulses along motor neurons to effectors to restore the temperature back to normal (eg . vasodialtion or vasoconstriction)

68
Q

Describe how beta cells from the ilsets of langerhan in the pancrease releasing the hormone insulin, lowers the blood glucose concentration?

A

Insulin binds to specific receptors on the cell membranes of liver cells and muscle cells

It increases the permeability of cell membranes to glucose so the cells take up more glucose

Insulin also activates enzymes that convert glucose to glycogen

Cells are able to store glycogen in their cytoplasm as an energy source

The process of forming glycogen from glucose is called glycogenesis

It also increases the rate of respiration of glucose, especially in muscle cells

69
Q

Describe how alpha cells from the islets of langerhans in the pancreas releasing glucagon raises the blood glucose concentration?

A

Glucagon binds to specific receptors on the cell membranes of liver cells

Glucagon activates enzymes that break down glycogen into glucose

The process of breaking down glycogen is called glycogenolysis

Glucagon also promotes the formation of glucose from fatty acids and amino acids, which is called gluconeogenesis

Glucagon also decreases the rate of respiration of glucose in cells

70
Q

What type of process is maintaining blood sugar levels?

A

Negative feedback

71
Q

Describe how Beta cells secrete insulin when they are depolarised?

A

When blood glucose concentration is high more glucose enters the beta cells via facilitated diffusion

More glucose in a Beta cell causes the rate of respiration to increase, making more ATP

The rise in ATP triggers the K+ ion channels in the Beta cell plasma membrane to close

This means K+ ions can’t can’t get through the membrane, so they build up inside the cell

This makes the inside of the cell less negative, as there more K+ ions within the cell- so the plasma membrane is depolarised

Depolarisation triggers calcium ion channels in the membrane to open, so calcium ions diffuse into the beta cell

This causes vesicles containing insulin to fuse with the beta cell plasma membrane, releasing insulin via exocytosis

72
Q

What is type 1 diabetes?

A

An auto immune disease, in which the body attacks and destroys the beta cells in the islets of langerhans, so the person can’t produce any insulin, so blood concentration stays high which can be deadly

73
Q

How do you treat type 1 diabetes?

A

Regular insulin injections, or a constant insulin pump

Can have islet cell transplation

74
Q

What’s type 2 diabetes?

A

When the Beta cells don’t produce enough insulin, or when the body’s cells don’t respond properly to insulin, so the blood glucose concentration is higher than normal

Acquired later in life than type 1 and is heavily linked to obesity

75
Q

How is type 2 diabetes treated?

A

Lifestyle changes

Medicine which reduces amount of glucose released by liver, and makes other cells more sensitive to insulin

76
Q

Advantages of having insulin produced by gentically modified bacteria, compared to being extracted from animals?

A

Cheaper
Larger quantities can be produced
They make human insulin which is more effective than using pig or cattle insulin- which is more likely to be rejected by immune system or cause an allergic response

Ethical and religious reasons

77
Q

How could stem cells be used to cure diabetes?

A

Could be grown into Beta cells
Implanted into pancreas of someone with type 1 diabetes
So they can now make insulin as normal

Biology final (28 decks)

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