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Biology > Paper 2- Topic 5 (homeostasis) > Flashcards

Paper 2- Topic 5 (homeostasis) Flashcards

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1
Q

What is homeostasis

A

The regulation of the conditions inside your body to maintain a stable internal environment

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2
Q

What are the three components the automatic control systems are made up of to maintain a steady condition

A

Receptors

Co-ordination centres (brain,spinal cord , pancreas)

effectors

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3
Q

Negative feedback process

A

Receptors detects stimulus level is too high/ low

Co- ordination centre receives and processes the information , then organises a response

Effector produces a response which counteracts the change and restores the optimum level

The effectors will just carry on producing the responses for as long as they’re stimulated by the co-ordination centre

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4
Q

Different parts of the nervous system

A

Central nervous system (CNS)

  • in vertebrates this consists of the brain and spinal cord only
  • the CNS is connected to the body by sensory and motor neurones

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

Motor neurones
- the neurones that carry electrical impulses from the CNS to effectors

Effectors
- all your muscles and glands which respond to nervous impulses

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5
Q

CNS response system

A 
Stimulus 
Receptor 
Sensory neurones 
CNS 
Motor neurone 
Effector 
Response
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6
Q

Synapses

A

The connection between two neurones

The nerve signal is transferred by chemicals which diffuse across the gap

These chemicals set off a new electrical signal in the next neurone

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7
Q

What is a reflex

A

A rapid and automatic response to certain stimuli that doesn’t involve a conscious part of the brain

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8
Q

What is the reflex arc

A

The passage of information in a reflex (from receptor to effector)

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9
Q

Reflex arc system

A

Neurones go trough spinal cord or an unconscious part of the brain

When a stimulus is detected by receptors impulses are sent along a sensory neurone to the CNS

When the impulses reach a synapse between the sensory neurone and a relay neurone they trigger chemicals to be released . These chemicals cause impulses to be sent along the relay neurone

When the impulses reach a synapse between the relay and motor neurone the same happens

The impulses then travel along the motor neurone to the effector

The muscle then contracts and moves hand away from stimulus

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10
Q

Investigating reaction time practical

A

Page 120

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11
Q

The brains different regions

A

Cerebral cortex - responsible for consciousness, intelligence , memory and language

Cerebellum- responsible for muscle co-ordination

Medulla- controls unconscious activities like breathing and heartbeat

Spinal cord

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12
Q

Methods to study the brain

A

Studying patients with brain damage

Electrically stimulating the brain

MRI scans

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13
Q

Different parts of the eye

A

Sclera - tough supporting wall of the eye

Cornea - transparent outer layer found at the front of the eye which refracts light into the eye

Iris - contains muscles that allow to control the diameter of be pupil and therefore how much light enters

Lens - focuses light into the retina (which contains receptor cells sensitive to light and colour)

Ciliary muscles and suspensory ligaments - control the shape of the lens

Optic nerve - carries impulses from receptors on the retina to the brain

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14
Q

Iris reflex

A

When light receptors in the eye detect a very 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 that can enter the eye

The opposite process happens in dim light

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15
Q

To look at near objects

A

The ciliary muscles contract which slackens the suspensory ligaments

The lens becomes fat (more curved)

This increases the amount by which it refracts light

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16
Q

To look at distant objects

A

The ciliary muscles relax which allows the suspensory ligament to pull tight

This makes the lens go thin (less curved)

So it refracts light by a smaller amount

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17
Q

Long sighted - hyperopia

A

This occurs when the lens is the wrong shape doesn’t reflect the light enough or the eyeball is too short

The images of their objects are brought into focus behind the retina

Glasses with a convex lens (curve outward) correct it

The lens refracts the light so they focus on to the retina

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18
Q

Short sighted - myopia

A

This occurs when the lens is the wrong shape and refracts the light too much or the eyeball is too long

The image of distant objects are brought into focus in front of the retina

You can use glasses with a concave lens (curve inwards? to correct it so that the light rays focus on the retina

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19
Q

Treatment for vision defects

A

Contact lenses

Laser eye surgery

Replacement lens surgery

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20
Q

Body temperature controlled by negative feedback

A

Temperature receptors detect that the core body temperature is too high /too low

The thermoregulatory centre acts as a coordination centre - it receives information from the temperature receptors and triggers the effectors immediately

Effectors produce a response and counteract change

21
Q

When you’re too hot - body changes

A

Hairs lie flat

Sweat is produced by sweat glands and evaporates form the skin to transfer energy to the environment

Blood vessels supplying the skin dilate so more blood flows close to the surface of the skin . This is called vasodilation which helps transfer energy to the environment

22
Q

When you’re too cold- body changes

A

Hairs stand up to trap an insulating layer of air

No sweat is produced

Blood vessels supplying the skin capillaries constrict to close off the skins blood supply which is called vasoconstriction

Shivering needs respiration which transfers some energy to warm the body

23
Q

What are hormones

A

Chemical molecules released directly into the blood

Control things in organs and cells that need constant adjustment

24
Q

Different endocrine glands

A

Pituitary gland

Thyroid

Ovaries

Adrenal gland

Pancreas

Testes

25
Q

Pituitary gland

A

Produces many hormones that regulate body conditions

Sometimes called the master gland because these hormones act on other glands directing them to release hormones that bring about change

26
Q

Thyroid

A

Produces thyroxine which is involved in regulating things like rate of metabolism, heart rate and temperature

27
Q

Adrenal gland

A

Produces adrenaline which is used to prepare for ‘fight or flight’

28
Q

Pancreas

A

Produces insulin which is used to regulate glucose levels

29
Q

Ovaries

A

Produce oestrogen which is involved in the menstrual cycle

30
Q

Testes

A

Produce testosterone which controls puberty and sperm production in males

31
Q

Differences between nerves and hormones

A

Nerves have very fast action
Hormones have slower action

Nerves act for a very short time
Hormones act for a long time

Nerves act on a very precise area
Hormones act more generally

32
Q

How kidneys act as a filter

A

Make urine by taking waste products out of your blood

Substances are filtered out of the blood as it passes through the kidneys (filtration)

Useful substances like glucose , some ions and the right amount of water and then absorbed back into the blood (selective reabsorption)

33
Q

Substances removed from the body in urine

A

Urea

Ions

Water

34
Q

Urea

A

Proteins can’t be stored in the body so any excess amino acids are converted into fats and carbs which can be stored.

Ammonia is produced as a waste product from this process

Ammonia is toxic so is converted to urea in the liver . Urea is then transported to the kidneys where it’s filtered out of the blood and excreted from the body in urine

35
Q

Ions

A

Ions such as sodium are taken into the body in food and absorbed into the blood

If the ion content if the body is wrong this could upset the balance between ions and water meaning too much or too little water is drawn into cells by osmosis

Some ions are lost in sweat . However this amount is not regulated so the right balance of ions in the body must be maintained by the kidneys. The right amount of ions is reabsorbed into the blood after filtration and the rest is removed in urine

36
Q

Water

A

The body has to constantly balance the water coming in against water going out

We lose water from skin in sweat and lungs from respiration

We can’t control how much we lose in these ways so the amount of water is balanced by the amount we consume and the amount removed by the kidneys in urine

37
Q

how blood glucose concentration is monitored when too high

A

by the pancreas

when blood glucose levels rise the pancreas senses it and releases insulin

insulin travels all around the body in the blood stream and triggers body cells to take up glucose from the blood

it also triggers liver and muscle cells to store excess glucose as glycogen

because glucose is taken out of the blood and stored , the glucose levels decrease

38
Q

diabetes

A

type 1 - no insulin produced
- insulin therapy used

type 2 - cells do not respond to insulin
- controlled through diet and exercise

39
Q

if blood becomes too dilute

A

water moves into cells by osmosis `

  • the pituitary gland stops releasing ADH
  • the kidneys reabsorb less water into the blood
  • more urine is produced and levels return to normal
40
Q

if blood becomes too concentrated

A

water moves by osmosis out of the cells

  • the pituitary gland releases ADH into the bloodstream
  • ADH travels to the kidneys and causes the kidney tubules to pass out more water
  • this means more water is reabsorbed from the tubules back into the blood
  • because of this less urine is produced and water level returns to normal and as this happens the pituitary gland stops releasing ADH
41
Q

ways we lose water out of our bodies

A

via the lungs when we exhale

via the skin when we sweat

via the kidneys in urine

42
Q

how the kidneys remove urea

A

blood enters the kidney through an artery

the kidney removes the urea and excess ions

these leave the kidney as urine which is stored in the bladder

blood now leaves the kidney through a vein

the blood no longer contains urea

43
Q

how the kidneys adjust the level of molecules in the blood

A

the blood passes through capillaries

small molecules are filtered out of the blood

these pass through a tube

now all of the glucose, some of the ions and some of the water is reabsorbed back into the blood

urea, excess ions and excess water are released as urine

44
Q

how the body deals with excess amino acids

A

the liver breaks down the excess amino acids and produces ammonia

ammonia is a very toxic chemical so the liver immediately converts it to urea

then urea can be safely excreted by the kidneys

45
Q

kidney dialysis

A

when a person has kidney failure, their blood will have a higher conc. of water, ions and urea than it should

in kidney dialysis, the patients blood passes over a semi-permeable membrane

this allows urea, ions and water through nut does not allow larger molecules to pass through

dialysis fluid contains the normal concentration of water and ions but does not contain urea so there is a concentration gradient for urea

the urea diffuses from the blood to the dialysis fluid

46
Q

why kidney dialysis can be inconvenient

A

patients have to visit the hospital several times a week

they have to eat a controlled diet so not too much urea is produced

47
Q

kidney transplant

A

the diseased kidney is replaced with a healthy kidney from a donor

however in some cases the donated kidney may be rejected by the patients immune system

48
Q

issues with kidney transplant

A

shortage of kidney donors

patients have to take anti rejection drugs for the rest of their life

49
Q

menstrual cycle and the four key hormones

A

FSH is released by pituitary gland
FSH travels in the blood to the ovaries where it causes an egg to mature
FSH triggers the ovaries to make oestrogen

Oestrogen causes the lining of the uterus to thicken
oestrogen stops the pituitary gland from releasing FSH

LH is released by the pituitary gland
LH triggers ovulation so mature egg is released

Biology (4 decks)

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