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Homeostasis and Response Flashcards

1
Q

What is homeostasis?

A

the regulation of the conditions inside your body to maintain a stable internal environment, in response to changes in the internal and external conditions

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2
Q

What are the three main components of your automatic control systems?

A

cells called receptors, coordination centres and effectors

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3
Q

What is negative feedback?

A

When the level of something gets to high or too low your body used negative feedback to bring it back to normal

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4
Q

How does negative feedback work?

A
  • Receptor detects a stimulus - level is too high or low
  • The coordination centre receives and processes the information then organises a response
  • Effector produces a response which counteracts the change and restores the optimum level - level decreases or increases
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5
Q

What are example of receptors and effectors?

A
  • Receptors are the cells that detect stimuli e.g. taste receptors on the tongue and sound receptors in the ears
  • Effectors respond to nervous impulses and bring about a change e.g. muscles contract and glands secrete hormones
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6
Q

What is the central nervous system (CNS)?

A

In vertebrates this includes the brain and spinal corn only. In mammals the CNS is connected to the body by sensory neurons and motor neurones.

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7
Q

What are sensory neurones and motor neurones?

A

Sensory - neurones that carry information as electrical impulses from the receptors to the CNS
Motor - the neurones that carry electrical impulses from the CNS to effectors

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8
Q

In what order does the CNS coordinate a response?

A
  • stimulus - a change happens
  • receptor - detects the stimulus e.g. pain receptors in skin or sound receptors in the ear
  • sensory neurone - carries electrical impulse from the receptor to the CNS
  • CNS - processes the information
  • motor neurone - carries the impulse from the CNS to the effector
  • effector - a muscle or gland that responds to the electrical impulse e.g. muscle contracts
  • response - the action taken e.g. pulling hand away
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8
Q

What is a synapse?

A

the connection between two neurones

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9
Q

How do neurones transfer signals?

A
  • the nerve signal is transferred by chemicals which diffuse across the gap
  • these chemicals then set off a new electrical signal in the next neuron
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10
Q

What is a reflex and why do we have them?

A
  • reflex’s are rapid automatic responses to certain stimuli that don’t involve the conscious part of the brain
  • e.g. if you get a shock your body releases adrenaline automatically
  • We have they to help prevent injurie
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11
Q

What is the order of a reflex arc

A
  • stimulus is detected by receptors e.g painful bee sting
  • impulses are sent along a sensory neuron to a relay neuron in CNS
  • when the impulses reaches a synapse between sensory and relay neuron they trigger chemicals to be released
  • these chemicals cause impulses to be sent along the relay neuron
  • when the impulse reaches a synapse between the relay and motor neuron chemicals are again released and cause impulses to be sent along the motor neuron
  • impulses travel along motor neuron to effector e.g. muscle
  • muscle then contracts to move hand away
    because you don’t think about the response its quicker than normal
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12
Q

Where do neurones in reflex arcs go through?

A

the spinal cord or unconscious part of the brain

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13
Q

What is the brain made up of?

A

billions of interconnected neurons

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14
Q

What does the cerebral cortex do?

A

its responsible for things like consciousness, intelligence, memory and language. (its the biggest bit)

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15
Q

What does the cerebellum do?

A

its responsible for muscle contraction (round bit at the back)

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16
Q

What does the medulla do?

A

controls unconscious activities like breathing and your heartbeat (long shape next to the spinal cord)

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17
Q

What methods do scientists use to study the brain?

A
  • MRI scans produce a very detailed picture of the brains structures. Scientists can use it to find out a what areas of the brain are active when people are doing things like listening to music or trying to recall a memory.
  • studying patients with brain damage. the effect it has on the patient can tell you a lot about how the damaged part of the brain does.
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18
Q

What are consequences of messing with the brain?

A

Its complex and delicate so
- it carries risks such as physical damage to the brain or increased problems with brain function like difficulties with speech
- investigation of brain function or treatment of brain damage is difficult

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19
Q

How does the iris reflex to a bright light and a dim light?

A
  • when light receptors in the eye detect a bright light a reflex is triggered that makes the pupil smaller. the circular muscles in the iris contract and the radial muscles relax. this reduces the amount of light entering the eye
  • the opposite happens, radial muscles contract and circular muscles relax which makes the pupil wider
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20
Q

How does the eye reflex to focus on near and distant objects?

A

Near
- ciliary muscles contract, which slackens the suspensory ligaments
- the lens becomes thicker (curved)
- this increases the amount by which it refracts light
Distant
- ciliary muscles relax, allowing suspensory ligaments to pull tight
- makes lens go thin
- so it refracts light by a smaller amount

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21
Q

What is long sighted and how does it work?

A

People are unable to focus on near objects.
- occurs when the lens is the wrong shape and doesn’t refract the light enough or eyeball is too short
- the images of near objects are brought into focus behind the retina
- you can use glasses with a convex lens to correct it
the lens refracts the light to focus on the retina

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22
Q

What is short-sightedness and how does it work?

A

People are unable to focus on distant objects
- occurs when the lens is wrong shape and refracts the light too much or the eyeball is too long
- the image of distant objects is brought into focus in front of the retina
- you can use glasses with a concave lens to correct it so light rays focus on the retina

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23
Q

What is the medical name for long-sightedness and short-sightedness?

A

long sighted - hyperopia
short sighted - myopia

24
What treatments are there for vision defects?
contact lenses, laser eye surgery and replacement lens surgery
25
How do contact lenses work and what are the benefits?
- thin layers that sit on the surface of the eye and are shaped to compensate for the fault in focusing. - they are popular as they are lightweight, almost invisible and more convenient for sports instead of glasses. - there are two types, soft and hard lenses. soft are more comfortable but have a higher risk of eye infections.
26
How does laser eye surgery work?
- a laser is used to vaporise tissue, changing the shape of the cornea, changing how strongly it refracts light - slimming it down makes its less powerful and can improve short sight - changing the shape so its more powerful will improve long sight - however, there's a risk of infection or the eye reacting in a way that makes your vision worse than before
27
How does the body react to cool you down when your too hot?
- sweat is produced by sweat glands and evaporates from the skin. this transfers energy to the environment - vasodilation, the blood vessels supplying the skin dilate so more blood flows to the surface of this skin to increase heat loss - hairs lie flat
28
How does your body react when your too cold?
- hairs stand up to trap an insulating layer of air - vasoconstriction, blood vessels suppling the skin constrict to close off the skins blood supply to reduce heat loss through the surface of the skin - shivering, needs respiration which transfers some energy to warm the body - no sweat is produced
29
What are hormones?
chemical molecules released by (endocrine) glands directly into the blood and carried to target organs. they tend to have long lasting effects.
30
What does the pituitary gland produce?
- many hormones that regulate body conditions - called the master gland because these hormones act on other glands directing them to release hormones to being about a change - (in the brain)
31
What does the thyroid gland produce?
- produces thyroxine, which regulates things like heart rate, temperature and rate of metabolism - (in the front of the neck)
32
What does the adrenal gland produce?
- produces adrenaline which prepares the body for a fight or flight response - (above the kidneys)
33
What does the pancreas produce?
- produces insulin which is used to regulate the blood glucose level - (liver)
34
What do the ovaries and testes produce?
- produces oestrogen, which is involved in menstrual cycle - produces testosterone, which controls puberty and sperm production in males
35
Whats the difference between hormones and nerves?
nerves - very fast action - act for a very short time - act on a very precise area hormones - slower action - act for a long time - act in a more general way
36
What removes glucose from the blood?
the metabolism of cells and vigorous exercise
37
where can excess glucose be stored?
as glycogen in the liver and in the muscles
38
How is glucose regulates if blood glucose level is too high?
- high sugar level (blood has too much glucose) - insulin released by pancreas - glucoses moves from blood into liver and muscle cells - in the liver, insulin turns glucose into glycogen for storage - as more glucose is removed from the bloodstream, blood glucose is reduced which reduces blood sugar level
39
How is glucose regulated if blood glucose level is too low?
- pancreas detects blood with too little glucose - glucagon released by pancreas (hormone that raises blood sugar level) - glucagon signals the liver to break down stored glycogen into glucose - glucose released into blood by liver - as glucose enter the blood, blood sugar level rises/blood glucose increased
40
What is type 1 diabetes?
- the pancreas produces little or no insulin. - so a persons blood glucose level can rise to a level that can kill them
41
How can type 1 diabetes be treated?
- they need insulin therapy, this involves several injections throughout the day at mealtimes to make sure glucose is removed from the blood once the food has been digested stopping the level getting to high. the amount of insulin injected depends on a persons diet and how active they are - they need to think about limiting the intake of food rich in simple carbohydrates e.g. sugars which cause level to rise rapidly - taking regular exercise to help remove excess glucose from the blood
42
What is type 2 diabetes?
- a person becomes resistant to their own insulin (their body's cells don't respond to the hormone) - this can cause a persons blood sugar level to rise to a dangerous level - being overweight can increase your chance of developing the disease, and obesity is a major risk factor
43
How can you treat type 2 diabetes?
- eating a carbohydrate controlled diet - getting regular exercise
44
What is the kidneys function?
- they make urine by taking waste products ( urea, excess water and ions) out of your blood - substances are filtered out of the blood as it passes through the kidneys, through filtration
45
What is selective reabsorption?
useful substances like glucose, some ions and right amount of water are reabsorbed into the blood after filtration - then waste substances are removed from the body in urine
46
What 3 substances are removed in urine?
urea, ions and water
47
Why do the kidneys remove urea?
- proteins and the amino acids they are broken into cant be stored in the body, so any excess are converted into fats and carbohydrates - this occurs in the liver and involves a process called deamination - ammonia is produced as a waste product from this process and its toxic so its converted to urea in the liver - urea is then transported to the kidneys where its filtered out
48
Why do the kidneys remove ions?
if the concentration of ions e.g sodium is too high or too low it can upset the balance between ions and water, meaning too much or too little water is drawn into cells by osmosis - this could damage the cells or mean they don't work as normal - (some ions are lost in sweat but this is not regulated, so the right balance of ions must be maintained by the kidneys) - so right amount of ions is reabsorbed and the excess is removed in urine
49
Why do the kidneys remove water?
- the body has to constantly balance the water coming in against the water coming out - so the amount of water is balanced by the amount we consume and the amount removed by the kidneys in urine - (water is also lost from the skin in sweat and from the lungs when we breath out, but we cant control how much we lose this way)
50
What hormone controls the concentration of urine?
- ADH (anti diuretic hormone) - the brain monitors the water content of the blood and instructs the pituitary gland to release ADH into the blood
51
What does the negative feedback cycle do to control water content regulation (if it gets too high or too low?)
too high - a receptor in the brain detects that the water content is too high - the coordination centre in the brain receives the information and organises a response - the pituitary gland released less ADH, so less water is reabsorbed from the kidney tubules and more urine is produces - blood water level returns to normal
52
How can kidney failure be treated?
- dialysis treatment, where machines do the job of the kidneys - kidney transplant
53
How does a dialysis work?
- blood enters one end of the filter from the person - in the dialysis machine the persons blood flows between partially permeable membranes surrounded by dialysis fluid - its permeable to things like ions and waste substances but not big molecules like protein - the dialysis fluid has the same concentration of dissolved ions and glucose as healthy blood - so useful dissolved ions and glucose wont be lost from the blood through diffusion, only waste substances such as urea and excess ions and water diffuse across because there is none in the fluid - blood goes back to person through the other end of the filter
54
How often do patients with kidney failure have to do a dialysis?
Three times a week and each session takes 3-4 hours
55
Pros and cons of dialysis?
cons - may cause blood clots or infections - expensive for NHS to run pros - buys a patient time until an organ donor is found
56
How can kidneys be transplanted?
- from people who have died suddenly, they have to be on the organ donor register or carry a donor card - can be transplanted from people who are alive
57
What are the risks?
- risk to the person donating the kidney - risk that the donor kidney can be rejected by the patients immune system - however they are cheaper than dialysis but there are long waiting lists

Biology (10 decks)

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