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F214 > 1. Communication and Homeostasis > Flashcards

1. Communication and Homeostasis Flashcards

0
Q

Receptors: what do they do? How are they adapted?

A

Detect stimuli and are specific, they only detect one particular stimulus.
Some are cells and proteins.

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1
Q

Why respond to the environment?

A

Increases chance of survival.

Maintain optimum conditions for the metabolism of an organism.

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2
Q

What are effectors and how do they communicate with receptors?

A

Effectors are cells that bring about a response to a stimulus to produce an effect. They communicate with receptors via hormone and the nervous system (cell signalling).

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3
Q

What is homeostasis and why is it important?

A

Homeostasis is the maintenance of a constant internal environment.
It is vital for cells to function normally and to stop them being damaged.
Changes in your external environment can affect your internal environment.

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4
Q

The effect of high internal temperature on enzymes?

A

At about 40 degrees human enzymes may become denatured. The enzyme’s molecules vibrate too much, which breaks the hydrogen bonds that hold them in their 3-D shape. The shape of the enzyme’a active site is changed and it no longer works as a catalyst. This means metabolic reactions are less efficient.

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5
Q

What is the effect of low internal temperature on enzymes?

A

Enzyme activity is reduce due to low kinetic energy this slows the rate of metabolic reactions.

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6
Q

What is the optimum internal temperature for metabolic enzymes?

A

37 degrees

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7
Q

How do homeostatic systems respond to changes?

A

Homeostatic systems respond by negative feedback.
Receptors detect when a level is too high or too low which is communicated to effectors which counteract the change. This is the negative feedback mechanism. It does not work for large changes.

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8
Q

What is positive feedback? When might it happen?

A

Positive feedback is where effectors respond to amplify a change. It might happen when platelets are forming a blood clot. The process ends with negative feedback to return the body to a constant environment.
Positive feedback is not part of homeostatic systems as it does NOT maintain a constant internal environment.

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9
Q

What are the three main types of neurone and what does each one do?

A

Sensory neurones transmit nerve impulses from receptors to the CNS.
Motor neurones transmit nerve impulses from the CNS to effectors.
Relay neurones transmit nerve impulses between sensory neurones and motor neurones.

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10
Q

What is the role of a sensory receptor in inducing a response?

A

Sensory receptors are transducers, they convert the energy of a stimulus into electrical energy which is transmitted across the nervous system as a nerve impulse.

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11
Q

Detail how a sensory receptor converts the energy of a stimulus into an electrical impulse.

A

The resting potential of the cell is altered when a stimulus is detected. The cell becomes more permeable to ions altering the potential difference of the cell slightly. This is the generator potential. A bigger stimulus excites the cell more causing a greater movement of ions and a greater generator potential. If the generator potential is large enough an action potential forms this only occurs if the threshold level is exceeded.

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12
Q

Describe the structure of a sensory neurone.

A

Receptor cells are connected to a dendrite which carries impulses towards the cell body.
The cell body is connected to an axon which in turn is connected to axon terminals at the CNS away from the cell body.

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13
Q

Describe the structure of a motor neurone.

A

Many dendrites from the CNS connect to the cell body. The cell body is connected to a long axon connected to axon terminals at the effector cells.

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14
Q

How does a neurone form and maintain its polarised resting state? What is the charge of the resting state?

A

The resting state is formed and maintained by sodium-potassium ion pumps and potassium ion channels. The pumps pumps out 3 Na+ ions to 2K+ ions using ATP. The potassium ion channel facilitates diffusion down the concentration gradient (they move out of the cell)
The charge of the resting state is -60 mv.

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15
Q

What are the 5 stages of an action potential?

A
  1. Stimulus
  2. Depolarisation
  3. Repolarisation
  4. Hyperpolarisation
  5. Resting potential
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16
Q

Describe stage 1 of an action potential.

A

Stimulus. The neurone cell membrane becomes excited by the stimulus. Causing sodium ion channels to open.
More and more Na+ ions diffuse into the cell down the electrochemical gradient. This makes the inside of the cell less negative.

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17
Q

Describe stage 2 of an action potential.

A

Depolarisation. If the potential difference of the neurone cell membrane exceeds the threshold potential (-50mv) many. More voltage gated sodium ion channels open an more sodium ions diffuse into the cell down the electrochemical gradient into the neurone drastically increasing the potential difference (to about +40 mv) forming an action potential.i

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18
Q

Describe stage 3 of an action potential.

A

Repolarisation. At a potential difference of about +40mv the sodium ion channels close and the voltage gated potassium channels open.
The potassium ions move out of the cell down the concentration gradient beginning to repolarise the neurone back to its resting potential.

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19
Q

Describe stage 4 of an action potential.

A

Hyperpolarisation. The voltage gated potassium ion channels are slow to close so there is an ‘overshoot’ past the resting potential.

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20
Q

Describe stage 5 of an action potential.

A

Resting potential. The ion channels are reset; the sodium-potassium pump returns the membrane to its resting potential (-60mv).

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21
Q

What is the ‘refractory period’?

A

The period after hyperpolarisation where the neurone cannot be affected by a stimulus (it cannot transmit an action potential).

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22
Q

Which way do Na+ ions diffuse after entering a neurone? What effect does this cause and why?

A

Sideways. Causes a ‘wave of depolarisation’ due to the refractory period of the previous neurone.

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23
Q

How is a larger stimulus communicated?

A

A larger stimulus causes more frequent impulses.

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24
Q

Describe the structure of a myelinated neurone.

A

Schwann cells arranged side by side which produce a lipid layer called myelin on the exterior of the cells. In between the Schwann cells are the nodes of ranvier (where depolarisation occurs).

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25
Q

In a myelinated neurone a nerve impulse is transmitted far faster than in a non myelinated neurone. What is the effect called, why and how does it occur?

A

The effect is called saltatory conduction. Only the nodes of ranvier can be depolarised in a myelinated neurone so the action potential ‘jumps’ from one node to the other causing a sharp increase in speed of an action potential.

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26
Q

Define the term ‘synapse’.

A

A synapse is a junction between a neurone and the next cell.

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27
Q

Name the key features of an cholinergic synapse.

A 
Synaptic knob
Vesicles of acetylcholine
Synaptic cleft
Voltage gated calcium ion channels
Presynaptic and postsynaptic membranes.
Sodium ion channels with acetylcholine receptors.
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28
Q

Detail the stages of an action potential being transmitted across a synapse.

A
  1. Action potential arrives at the synaptic knob
  2. Voltage gated Ca2+ channels open and calcium ions diffuse into the Presynaptic knob.
  3. The calcium ions cause the vesicles of acetylcholine to move to and fuse with the Presynaptic membrane.
  4. The acetylcholine is released by exocytosis which diffuse across the synaptic cleft. The acetylcholine reaches and binds to the specific complementary receptors on the postsynaptic membrane.
  5. Sodium ion channels on the postsynaptic membrane open and cause a generator potential. If enough open then the neurone becomes depolarised past the threshold potential causing and passing on an action potential.
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29
Q

What is the role of acetylcholinesterase?

A

Acetylcholinesterase is the enzyme which hydrolysed acetylcholine to ethanoic acid and choline. This is to prevent the continuous transmission of an action potential.

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30
Q

Describe synaptic convergence.

A

Many small impulses from many neurones connect to one neurone to form one large action potential.

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31
Q

Describe summation.

A

Many low level signals combine to form an action potential from many smaller stimuli.

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32
Q

An advantage of a synapse?

A

Make sure impulses are only transmitted in one direction.

33
Q

What is an endocrine gland?

A

An endocrine gland are ductless glands which release or secrete hormones directly into the blood.

34
Q

How might an endocrine gland be stimulated?

A

By electrical impulse or the change on concentration of a specific substance.

35
Q

What is the name of the cells and tissue which the hormone is targeting?

A

The target cells and target tissue (the hormone travels around the bloodstream and only binds to its single specific site)

36
Q

What are the 5 stages of the action of a hormone?

A
  1. stimulus
  2. receptors
  3. hormones
  4. effectors
  5. response
37
Q

Detail stage 1 of the action of a hormone.

A

Stimulus. A specific stimulus is detected (e.g. Low blood glucose concentration)

38
Q

Detail stage 2 of the action of a hormone.

A

Receptors. Receptors detect the stimulus (e.g. The receptors on the pancreas cells detect the low blood glucose concentration)

39
Q

Detail stage 3 of the action of a hormone.

A

Hormones. The endocrine gland releases the hormone required to produce the desired effect in response to the stimulus (e.g. The pancreas releases glucagon into the blood to counteract a low blood glucose concentration.)

40
Q

Detail stage 4 of the action of a hormone.

A

Effectors. Target cells detect the hormone and produce the intended effect (e.g. Target cells in the liver detect glucagon and convert glycogen into glucose)

41
Q

Detail stage 5 of the action of a hormone.

A

Response. The effect is realised in the body (e.g. Glucose is released into the blood thus increasing the blood glucose concentration.)

42
Q

Explain the terms primary and secondary messenger.

A

The hormone is the primary (or first) messenger, it carries the message from the endocrine gland to the target cell receptors.
The secondary messenger delivers the message the second half of the way, from the receptor to the rest of the cell.

43
Q

Outline the process of the release of cAMP from adrenaline to the body.

A

The hormone adrenaline is the primary messenger (it cannot fit inside the cell). It binds to the specific receptors on the target cell which is associated with the enzyme in the membrane called adenylate cyclase.
Adenylate cyclase becomes activated by the presence of the hormone in the receptor and begins to catalyse the reaction converting ATP into cyclic AM.

44
Q

Name and describe the difference between the two types of gland in the body.

A
  1. Endocrine - releases hormones directly into the blood.

2. Exocrine - secretes chemical through ducts into cavities or onto the surface of the body.

45
Q

Is the pancreas an endocrine or exocrine gland?

A

It’s both!

46
Q

The majority of the pancreas is what kind of tissue?

A

Exocrine tissue made up of acinar cells.

47
Q

Where are acinar cells found?

A

They are found in the pancreas surrounding the pancreatic duct. A duct that goes to the duodenum (part of the small intestine).

48
Q

What is the role of the acinar cells in the pancreas?

A

Acinar cells release the digestive enzymes amylase, trypsinogen and lipase into the small intestine from the pancreatic duct in order to help digest food.

49
Q

What is the endocrine tissue in the pancreas called? What cells is it made up of?

A

The endocrine tissue is called the islets of langerhans and they are made up of alpha an beta cells.

50
Q

What is the role of alpha cells in the pancreas?

A

They are part of the endocrine tissue - the isle of langerhans and secrete the hormone glucagon into the blood.

51
Q

What is the role of beta cells in the pancreas?

A

Beta cells are one type of cell which make up the islets of langerhans and are responsible for secreting the hormone insulin into the blood.

52
Q

Describe the structure of the adrenal gland.

A

The adrenal gland has an outer structure called the cortex and an inner structure called the medulla.

53
Q

Outline the role of the cortex in the adrenal gland.

A

The cortex is responsible for releasing steroid hormones such as cortisol.

54
Q

Outline the role of the medulla in the adrenal gland.

A

The medulla is responsible for secreting catecholamine hormones (modified amino acids) such as adrenaline.

55
Q

What part of the brain monitors internal body temperature and is responsible for thermoregulation?

A

The hypothalamus.

56
Q

How are changes in external body temperature detected?

A

External receptors on the skin.

57
Q

Give examples of bodily responses to being too cold.

A 
Vasoconstriction.
Less sweating.
Erector pili muscles contract. (Hair stands on end)
Shivering.
Adrenaline and thyroxine are released.
58
Q

Give examples of bodily responses for being too hot.

A 
Vasodilation.
Sweating.
Erector pili muscles relax.
No shivering.
No adrenaline / thyroxine released.
59
Q

Why is it important to regulate insulin levels?

A

Insulin is used to control the levels of glucose in the blood. Glucose is vital in respiration of body cells.

60
Q

Where is insulin secreted from?

A

Insulin is secreted by the beta cells, cells which make up part of the islets of langerhans.

61
Q

What structures in a beta cell allow it to fulfil its function?

A

The cell membrane has potassium and calcium ion channels. Usually the potassium channels are open and the calcium channels closed.

62
Q

Describe the process that occurs when glucose concentrations outside of a beta cell increase.

A

Glucose begins to diffuse into the cell . The glucose is metabolised by glucokinase into glucose phosphate and finally metabolised into ATP. The ATP produced causes the potassium ion channels to close. Due to this the potassium ions can no longer diffuse out of the cell and the inside of the cell becomes less negative. The change in potential difference causes the voltage gated calcium channels to open. The calcium ions cause the vesicles containing insulin to move to the membrane of the beta cell and fuse with it releasing the insulin by exocytosis.

63
Q

What is diabetes mellitus?

A

Diabetes mellitus refers to where the body cannot control its blood glucose levels.

64
Q

What does diabetes mellitus lead to?

A

Diabetes mellitus can lead to hyperglycaemia (high blood glucose levels) or hypoglycaemia (low blood glucose levels)

65
Q

What types of diabetes are there? What are the differences are there between them?

A 
Type 1 (insulin-dependant) diabetes: where the body's own immune system attacks the beta cells in the islets of langerhans, the body can no longer manufacture sufficient insulin and cannot store excess glucose as glycogen.
Type 2 (non-insulin dependant) diabetes: the individuals response to insulin is diminished, the receptors on the surface of the liver and muscle cells lose their ability to respond to insulin in the blood.
66
Q

What factors contribute to causing type 2 diabetes?

A

Obesity
A diet high in refined sugars
Family history
Asian/Afro-Caribbean origins

67
Q

How is type 2 diabetes treated?

A

Type 2 diabetes is usually treated through careful monitoring and control of the diet. Individuals may have their diet supplemented with insulin.

68
Q

How is and how might type 1 diabetes be treated?

A

Type 1 diabetes is treated using insulin injections. Blood glucose is closely monitored to ensure that the correct dose of insulin is administered.
Type 1 diabetes could also be controlled using diabetes produced from genetically modified bacteria or by using stem cells by developing the stem cells into beta cells into type 1 sufferers.

69
Q

What are some advantages of producing insulin from genetically produced bacteria?

A

Cheaper than extraction from animal pancreases
Larger quantities of insulin can be produced using GM bacteria
Producing human insulin is more effective in producing the desired response than pig or cattle insulin and is far less likely to cause an allergic reaction in a patient.
For ethical or religious reasons some individuals may reject the use of pig or cattle insulin (vegetarians and Muslims for instance)

70
Q

What is the role of blood in the body?

A

Blood acts as a solvent and delivers many useful substances to cells around the body such as glucose, fatty acids and amino acids.
Blood also removed waste products of metabolic processes from the body, this includes carbon dioxide and urea.

71
Q

How does the heart respond to increased respiratory demands of the body?

A

Increased number of beats per minute
Increased strength of contractions
Increased volume of blood pumped in each stroke.

72
Q

Why is the heart described as being myogenic?

A

It can control its own muscle contractions.

73
Q

What is the SAN? What is its role?

A

The SAN stands for the sinoatrial node. It is a region of tissue in the heart tissue which can initiate an action potential in order to contract the cardiac muscle.

74
Q

The sinoatrial node can initiate an action potential in the heart. How does it travel through the heart in order to contract the cardiac muscle?

A

The action potential travels as a wave of excitation over the atria walls through the atrioventricular node (AVN) and down the purkyne fibres to the ventricles causing them to contract.

75
Q

The Sinoatrial nerve and the Medulla Oblongata are connected. How?

A

The medulla Oblongata supplies two nerves to the SAN, the vagus nerve and the accelerator nerve.

76
Q

What is the role of the vagus nerve?

A

The vagus nerve slows down the heart rate.

77
Q

What is the role of the accelerator nerve?

A

The accelerator nerve speeds up the heart rate.

78
Q

How does the presence of adrenaline in the blood affect the heart?

A

The presence of adrenaline, which binds to receptors on cardiac muscle, speeds up heart rate.

79
Q

What is the average resting heart rate?

A

60-80 bpm

80
Q

Where in the medulla Oblongata controls heart rate?

A

The cardiovascular center.

81
Q

What factors affect heart rate?

A

Stretch receptors in muscles tell the medulla Oblongata that the muscle is undergoing work and respiring and will soon need oxygen for respiration (heart rate increases)
Respiring releases CO2 which reacts with water to form carbonic acid. This lowers the pH of the blood and is detected by chemoreceptors in the carteroid arteries, the aorta and the brain (heart rate increases)
Adrenaline increases heart rate by binding to receptors on the cardiac muscle (heart rate increases)
Blood pressure is monitored by stretch receptors in the walls of the carotid sinus (a swelling in the carteroid artery) if blood pressure is high then heart rate slows down and vice versa.

F214 (4 decks)

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