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ST2 Biology > Homeostasis > Flashcards

Homeostasis Flashcards

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1
Q

What is a tolerance limit?

A

a limit of conditions in which an organism can effectively operate within, the survival of an organism can be threatened when these conditions fluctuate from tolerance limits

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2
Q

Name 4 factors for which organisms have tolerance limits.

A

Body temperature, water availability, carbon dioxide/pH levels in the brain, and blood sugar levels

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3
Q

How do organisms detect changes in the internal and external environment?

A

Via sensory receptors

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4
Q

What is the purpose of homeostasis?

A

To maintain a stable internal and external environment, enabling the survival of an organism

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5
Q

Compare the structure and function of sensory neurons, interneurons and motor neurons

A

Sensory neurons are unipolar, have cell body half way down its axon. Axon synapses with interneuron to transmit message to CNS, transmits signal from sensory receptors. only found in PNS

Interneurons are usually multipolar. Dendrite synapses with sensory neurons. Axon synapses with interneurons or motor neurons, transmitting signal.Only found in the CNS.

Motor neurons are usually multipolar. dendrite synapses with interneuron, axon synapses with effector, enabling a response to be carried out. only found in PNS

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6
Q

What 2 structures make up the central nervous system (CNS)? What types of neurons are in the CNS?

A

Brain and spinal cord
Interneurons

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7
Q

Describe the structure of a nerve pathway from receptor to effector

A

Receptor – sensory neuron – interneuron/s – motor neuron – effector
Receptor detects a stimulus, transmitting a nerve impulse that travels along the sensory neuron to the Central Nervous System (CNS). The nerve impulse is transmitted to the spinal cord to the brain, the brain processes the information (stores or relates to pre-existing information), the brain sends back down the spinal cord to a motor neuron, motor neuron transmits message to effector, leading to a response being carried out

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8
Q

Describe the role of a synapse

A
  • It is a junction between neurons
  • Specific, target method of controlling nerve transmission that can be inhibited
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9
Q

Where are neurotransmitters stored in a neuron?

A

vesicles

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10
Q
  • How are neurotransmitters release from a neuron?
A

Exocytosis

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11
Q

What causes neurotransmitter release?

A

nerve impulse

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12
Q

How do neurotransmitters move across the synapse?

A

Diffusion

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13
Q

How do neurotransmitters create a signal in the post-synaptic neuron?

A

Nerve impulse stimulates vesicles containing neurotransmitters to migrate to the cell membrane (of pre-synaptic neuron) and neurotransmitters are released into the synaptic space
neurotransmitters move across the synaptic space via diffusion and bind to complementary receptors on post-synaptic neuron, this transmits the information, thus resulting in a nerve impulse/signal generation

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14
Q

What happens to neurotransmitters after the signal is sent in the post-synaptic membrane?

A

Released from receptors, re-uptake into pre-synaptic neuron via transporters

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15
Q

How can medications/drugs interfere with the transmission of signals to post-synaptic neuron via neurotransmitters?

A

Inhibit transporters, block receptors, prevent exocytosis

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16
Q

Why are reflex responses important?

A

For self-preservation – ensure the safety of an individual

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17
Q
  • What is the pathway of a reflex response? and State how this response is fast and automatic.
A
  • ## Sensory receptor – sensory neuron – interneuron – motor neuron – effector
  • Fast: via nerves to the nearest part of the CNS
  • Automatic: direct connection to one interneuron between sensory and motor neuron
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18
Q

Name 4 things that a hormone can be made of.

A

Amino acid derivatives, steroids, proteins, peptides

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19
Q

How are hormones transported around the body?

A

Via the bloodstream

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20
Q

State 2 things that can stimulate a hormonal response?

A

Nervous stimulation e.g., fight or flight response
Hormonal stimulation e.g., TSH stimulates thyroxine release

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21
Q

Describe the role of adrenaline in the flight or fight response

A

When an organism detects danger, the brain transmits a nerve impulse, via a motor neuron, to the adrenal gland, the adrenal gland secretes adrenaline, which is responsible for increasing breathing and heart rate, and blood flow to the brain and limbs, and for accessing energy stores via glucose within seconds

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22
Q
  • What organ secretes adrenaline?
A

Adrenal gland

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23
Q

What stimulates adrenaline release?

A

Nervous signal from brain

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24
Q

Describe 3 or more effects of adrenaline on body functions

A

Increase breathing rate, increase heart rate, increase blood flow

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25
Q

What gland secretes TSH?

A

Pituitary gland

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26
Q

Where are the receptors of TSH?

A

Thyroid gland

27
Q

What hormone is released when TSH binds to receptors?

A

Thyroxine (T4)

28
Q

Where are the receptors for thyroxine?

A

All cells in the body

29
Q

What is the effect of thyroxine on the body?

A

Increase metabolic rate

30
Q

Describe the action of thyroid stimulating hormone and thyroxine in metabolism.

A
  1. hypothalamus in the brain releases thyroid-releasing hormone (TRH)
  2. TRH stimulates pituitary gland in the brain to release thyroid stimulating hormone (TSH)
  3. TSH binds to complementary receptors on the cell membrane of thyroid gland, stimulating the steroid to secrete thyroxine
  4. Thyroxine binds to complementary receptors on body cells, transmitting cell signal to increase metabolic rate
31
Q

Describe the action of insulin in blood sugar regulation.

Release from:
Transported in:
Target cells:
Action:
Outcome:

A

Release from: Beta cells in pancreas

Transported in: Blood

Target cells: fat, muscle and liver cells

Action: Binds to complementary receptors on liver cells, transmitting cell signal to open glucose protein channels, (glucose is converted into glycogen for storage), initiates fat and muscles cells to uptake glucose

Outcome: Decreased blood sugar levels

32
Q

Describe the action of glucagon in blood sugar regulation.

Release from:
Transported in:
Target cells:
Action:
Outcome:

A

Release from: Alpha cells in pancreas

Transported in: Blood

Target cells: Liver cells

Action:Binds to complementary receptors on liver cells, transmitting cell signalling to open glucose channels (glucose is converted into glycogen), initiating the release of glucose into the blood stream

Outcome: Increased blood sugar level

33
Q

Describe how diabetes melitus can result from a hormonal imbalance.

A

If insulin is not produced or cannot function properly
Cell signal cannot be transmitted to open glucose protein channels therefore, individual will have constant high blood sugar levels – this is diabetes

34
Q

Describe the effect of antidiuretic hormone (ADH) on the nephron in osmoregulation.

A

Anti Diuretic hormone (ADH) binds to complementary receptors on nephron tubule, transmitting cell signalling to open aquaporins, this increases the permeability of the nephron tubule
This results in more water reabsorption into the blood stream, there will be less water content in urine, hence less volume of diluted urine is produced

35
Q

Discuss links between osmoregulation, blood volume, and blood pressure.

A

ADH increases the permeability of nephrons, therefore more water is reabsorbed into blood stream, resulting in an increase in the volume of blood, increased blood volume results in increased blood pressure

36
Q

Where are the body receptors that detect changes in external temperature?

A

Skin

37
Q

Where is the receptor that detects internal temperature.

A

Hypothalamus

38
Q

When temperature is too cold, state 3 effectors that are stimulated by nerves and describe their effect.

A

Skeletal muscles – muscles contract and relax rapidly to generate more heat (shivering)

Smooth muscles – decrease blood flow to skin surface, keeping warm deep within the body

Arrector pili muscles – muscles contract, hair stands up, trapping an insulating layer of air to reduce heat loss

39
Q

State two hormones that are released when the temperature is too cold and describe their effect.

A

Adrenaline and thyroxine : both increase metabolic rate, increasing heat generation

40
Q

Describe how sweat gland respond when they receive stimulating from a nerve and explain how this cools the body.

A

Nerve impulse stimulates sweat glands to produce sweat on skin surface
Body heat is used to evaporate sweat
Evaporation has a cooling effect
Body heat is lost into the environment, thus cooling the body

41
Q

Explain how nervous stimulation of smooth muscle can help cool the body.

A

Nerve impulse stimulates smooth muscles in blood vessels to relax/dilate (vasodilation), this increases blood flow to skin surface
Heat is radiated from the body, thus resulting in heat loss, which cools the body

42
Q

Describe how hormonal changes can help reduce body temperature

A

Decreased production of adrenaline and thyroxine will result in decreased metabolic rate, therefore less heat is generated

43
Q

What is the meaning of the term osmoregulation?

A

Water balance

44
Q

State the two stimuli for osmoregulation and describe where these stimuli are detected.

A

Hypothalamus detect changes in concentration of the blood – solute concentration
e.g., High solute concentration = low water content = low blood volume = low blood pressure

Stretch receptors in blood vessels detect blood volume
e.g., more stretch = high blood volume = high water content = high blood pressure

45
Q

Describe the nervous transmission involved in osmoregulation.

A

Nervous transmission from stretch receptors to the pituitary gland when stimulus is detected

46
Q

State the name of the hormone involved in osmoregulation.

A

Anti diuretic hormone (ADH)

47
Q

State the name of the effector involved in osmoregulation

A

Nephron tubule

48
Q

Explain the effect of ADH on the permeability of the nephron

A

The more ADH present, the more permeable the nephron tubule
ADH increases the permeability of the nephron by transmitting cell signal to open aquaporins, which allow water reabsorption into the blood stream

49
Q

Describe the effect on blood volume, blood pressure and urine volume when ADH is secreted.

A

By increasing the permeability of the nephron tubule, ADH increases the reabsorption of water into blood stream, this results in an increase in blood volume (Stretch muscles are more stretched)
Increased blood volume increases blood pressure
Less water content in urine, hence less volume of diluted urine is produced

50
Q

What organ contains the receptors for changes in blood sugar levels

A

pancreas

51
Q

What is the hormone that is secreted when blood sugar is high (e.g. after a meal)

A

Insulin (from beta cells)

52
Q

What is the hormone that is secreted when blood sugar is too low?

A

Glucagon (from alpha cells)

53
Q

What types of cell will contain receptors for insulin?

A

Liver, muscle, fat cells

54
Q

Describe the effect of insulin binding on the cell and blood sugar levels.

A

Decreased blood sugar levels
By binding to complementary receptors on liver cells, insulin transmits cell signalling to open glucose protein channels glucose moves from blood into cell
Insulin initiates the uptake of glucose of in fat and muscle cells
(Glucose is converted into glycogen for storage)
Thus, there is less glucose in bloodstream, resulting in decreased blood sugar levels

55
Q

What cells contain receptors for glucagon?

A

Liver cells

56
Q

Describe the effect of glucagon binding on the cell and blood sugar levels.

A

By binding to complementary receptors on liver cells, glucagon transmits cell signalling to open glucose protein channels (glycogen is converted into glucose), glucose is released into the blood stream, thus, resulting in increased blood sugar levels

57
Q

What happens to pH level when CO2 is dissolved in blood?

A

Decrease in pH (more acidic)

When CO2 dissolves in water, carbonic acid is produces, thi

58
Q

What is the name of the receptor that detects changes in blood pH and where is it located?

A

respiratory centre in the brain

59
Q

What does rapid breathing do to the CO2 levels in the blood? And the blood pH?

A

Decrease carbon dioxide levels in the blood, more carbon dioxide is transported via the blood to the lungs where it is eventually expelled through exhalation, decreased carbon dioxide levels increases blood pH levels (as it is less acidic)

60
Q

What will holding your breath do to CO2 levels in the blood? And the blood pH?

A

Decrease blood pH levels, increase carbon dioxide levels

61
Q

What is the type transmission that occurs when maintaining blood CO2 homeostasis?

A

Nervous transmission

62
Q

What two groups of muscles are the effectors for CO2 homeostasis?

A

Respiratory muscles (chest muscles and diaphragm) and cardiac muscles

63
Q

What is the response when CO2 levers are too high?

A

Increase breathing rate: increases expel of carbon dioxide

increase heart rate : trains your body to move oxygen and blood to your muscles more efficiently

this decreases carbon dioxide levels in blood, thus, increases blood pH levels

64
Q

What is the response when CO2 levels are too low?

A

Decrease carbon dioxide levels, increase blood pH levels
Decrease heart rate and decrease breathing rate: less carbon dioxide is expelled, thus, increasing acidic, resulting in a decrease in blood pH levels

ST2 Biology (4 decks)

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