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Ocr Gcse Biology > B3 > Flashcards

B3 Flashcards

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1
Q

What are the 3 main stages to a nervous response?

A

Stimulus-a change in environment
Receptors- a group of cells that detect the stimulus
Effectors- muscles or glands that respond

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2
Q

What are the steps involved in a nervous reaction?

A

Stimulus->receptor cells->sensory neurone-.spinal cord->brain->spinal cord->motor neurone->effectors->response

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3
Q

What are the 3 main types of neurones?

A

Sensory neurones - carry electrical impulses fom receptor cells to the CNS.(dendron transmits the impulse to cell body)
Relay neurones- carry electrical impuses from sensory neurones to motor neurones(only in CNS)
motor neurones- carry eletrical impulses from CNS to effectors(axon transmits impulse away from cell body)

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4
Q

What are reflex actions?

A

They are automatic actionsthat are involuntary. They are faster as thy dont travel to brain

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5
Q

Reflex arc

A

Stimulus->Receptor cells->Sensory neurone->spinal cord->Motor neurone->response

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6
Q

reflex action examples?

A

burning hand-> bicep contracts so hand pulls away

snad in eyes-> eyelids muscles contact making you blink

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7
Q

Main structures of the eye?

A

Cornea-. trnasparent coating at front of the eye that protectseye and refracts light from entering.
Pupil- a centralhole in iris that allows light to enter the eye
iris-> a coloured ring of muscle tissue that alters pupil size by contracting and relaxing.
Lens-a transparent biconvex lens that focuses light clearly on the retina
Ciliary body-ring of muscle tissue that alters hape of lens

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8
Q

How are images formed?

A

Cornea refracts incoming light rays. Light passes through pupil and is refracted by lens creating image on retina. Photoreceptors in retina produce nervous impulse when exposedto light, image travels down optic nerve to brains creating visual image.

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9
Q

How does eye focus on near and far objects?

A
  • When ciliary muscle contracts, lens become more convex(fatter) you can focus on nearby objects
  • When cilialy muscles relax, lens becomes less convex(thinner), you can focus on distant objects
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10
Q

What causes short sightedness, how can it be corrected?

A
  • Shot sightedness is caused by lens being too strong or eyeball being too long. This makes light rays meet infront of retina, image is blury
  • Can be corrected with concave lens, bends light rays before they enter eye
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11
Q

What causes long sightedness, how can it be corrected?

A
  • Long sihgtedness caused by persons lens being too weak, or eyeball too short, light rays meet behind retina so image is blury
  • Convex lens bends light invanrds before it meets eye
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12
Q

What are 2 typesof photoreceptors?

A

Rods- Respond to light, black and white, allows vision in low light levels

Cones- Respond to colours. Diferent cone cells repsond to R,G,B light

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13
Q

Whats an advantage of having a brain?

A

Having a central control centre means neuronal communcations are much faster than if they were spread around the body.

-Function of brain is process info and produce coordinated respone

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14
Q

What are 5 main areas of the brain and functions.

A

Medulla- controls automatic actions, breathing and heart rate
Cerebrum- controls balance, posture and involuntary actions
Cerebellum- controls complex behaviour: learning, memory, personality and consious thought
Hypothalamus- regualtes temperature and water balance.
Pituitary gland- stores and releases hormones that regulate many body functions

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15
Q

How can you investigate brain function?

Hint; scan

A

Ct Scans-> Use x-rays to create 3D imaes of body, it cant be used regularly as its radiation increaea risk of cancer.
MRI Scans->Use powerful magnets to identify braiin abnormalities. Fmri produces real time images

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16
Q

What are effects of dmage to PNS?

A
  • inability to detect pain
  • numbness
  • loss of cordination
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17
Q

How is PNS damage treated?

A

While it can regenate, it has a limited ability to do so, severe nerve damage can be treated through surgery

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18
Q

What are effetcs of CNS damage?

A

Loss of control of body systems
Partial or complete paralysis
Memory loss or processing difficulties

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19
Q

Why is CNS not able to be treated?

A

CNS cannot regenerate and it is extremely hard to do surgery:

  • Spinal cord is so small that identifying and repairing an indidual nevre fibre, without damaging others is too hard
  • Spinal injuries often lead to paralysis
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20
Q

Treatments for CNS brain damage?

A

radiotherapy- used treat a brain tumor
surgery- remove damaged brain tissue
deep brain stimulation- inserting an electron to stimulate brain

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21
Q

What are hormones and how do they travel?

A

Hormones are chemical messengers that are secreted into the blood and made in endocrine glands. The blood transports the hormones in plasma around the body.

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22
Q

What are the roles of hormones?

A

Hormones regulate functions of many cells and organs. Hormonal control body processes that require constant adjustment. Keepng conditionsin your body constant is called homeostasis.

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23
Q

What is the endocrine system?

A

It is all the endocrine glands and hormones they produce.

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24
Q

Compare messaging with nerves and hormones?

A

Hormones- slower, in blood, long acting and larger are. HBGT

Nerves- faster, electrical impulse along axon of neurone, short acting, small precise area.

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25
Q

What is thyroxine?

A

A hormone released by throid gland, located in neck. It plays important role in regulating body’s metabolic rate.

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26
Q

What is adrenaline?

A

Hormone secreted by adrenal gland in times of stress to prepare body for fight or flight situation.

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27
Q

What does adrenaline do?

A

It prepares bodyfor flight or fight by increasing breathing rate and activating processes that increase oxygen supply and glucose to cells.

28
Q

Whats the negative fedback loop?

A
  • Conditions in body change from set point
  • Change detected by receptor
  • Corrective mechanisms activated by an effector
  • Conditions returned to set point
  • Corrective mechanisms turned off
29
Q

How are TSH levels controlled?

A

TSH stimulates thyroid gland to release thyroxine
Hypothalamus detects energy levels are sufficient
Pit glad stops releasing TSH, inhibiting thyroid gland
Thyroid gland stops producing thyroxine

30
Q

What is the menustral cycle?

A
  • lasts 28ish days
  • prepares womens body for potential pregnancy
  • uterus lining thickens when egg matures
  • ovulations occurs around day 14
  • if egg is fertilised it may implant in the uterus lining
  • If egg not fertilised lining and egg removed from body, known as a period
31
Q

Whihc 4 hormones control menustral cycle and their functions?

A

FSH- Secreted by pit gland, causes egg to mature and stimulates ovaries to produce oestrogen
Oestrogen-Made and secreted by ovaries, causes uterus lining to repair/build up. When its levels rise it inhibits production of FSH, so that only 1 egg gets mautred, its last role is to stimulate LH from pit gland
LH- secreted by pit gland. When LH levels reach a peak in middle of cycle voulation occurs.
Progesterone- miantains uterus lining and inhibits LH so that ony 1 egg is released, also inhibts FSH

32
Q

Name 3 non-hormonal methods of contraception and what they do?

A

Condom- Prevents sperm from entering vagina, can protect from STDs
Diaphram/Cervical cap- Inserted in vagina to cover cervix, not effective unless used wiht spermicides(chemials that can kill sperm)
Intrauterine device/coil- Inserted in uterus and releases copper which stops sperm surviving in uterus and fallopian tubes, can also prevent implantation of fertillised ovum, remains effective for 5-10 years.

33
Q

Name 3 hormonal mothods ofcontraception adn what thye do?

A

Combined pill(oestrogen+progestrone)- pevent ovulation, thickens mucus from cervix preventing sperm reaching ovum and implantation of fertilised ovum.

Progestrone pill- Thickens cervix mucus, maintains thin uterus lining preventng implantation, can prevent ovultion

Intrauterine system- Insertd into uterus has same effect as progestrone pill, remains effective for 3-5 years.

34
Q

What are some causes of infertility?

A
  • Blocked fallopian tubes
  • Blocked sperm ducts
  • Not enough sperm produced in testes
  • Lack of mature eggs in testes
  • Failure to release eggs
35
Q

What’s fertility treatment?

A

Using homrones to try and treat infertility. FSH cn be used as an artificial drug as it stimulates eggs to be matured in ovaries and increases oestrogen production,increasing likelihood of eggs being released

36
Q

How does in vitro fertilisation work?

A

FSH and LH are given to the mother, ennsures as many eggs as possible are released to be harvested. Then placed in petri dish with male sperm. Eggs are checked if fetrilised, early embryos start developing. When they form tiny balls of cells, 1 or 2 placed in womb, if successful a baby will potentially be born.

37
Q

What’s phototropism?

A

Phototropism means growing towards light. As stem grows towards light it’s able to photosynthesise more, so theres more food for plant to grow faster.

38
Q

What are auxins?

A

Auxins are plant hormones that contol growth at tips of shoots and roots, enables plant to grow towards or away from a stimulus.
They promote growth in shoots, but inhibit in roots.
They are made in cells near tips of shoots or roots and diffuse backwards to stimulate elongation process

39
Q

What’s gravitropism?

A

Gravitropism is growing in the same direction as gravity. It’s important for roots to grow downwards as this provides support and takes it closer to water.

40
Q

How do plants(shoots and roots) respond to light?

A

Shoots are positively phototrophic. When shoot tip is exposed to light, auxin moves to shaded side building up auxin concentration. This causes cells on shaded side to grow faster, so shoot bends towards light.

Roots are negatively phototrophic, if exposed to light more auxin gathers to shaded side, inhibiting growth, so root bends towards ground

41
Q

How do plants(shootsand roots) respond to gravity?

A

Shoots are negatively gravitropic, when growing sideways, gravity causes uneven distrubution of auxin in tips. This causes lower side to grow faster bending the shoot upwards.

Roots are positively gravitropic. A root growing sideways always has auxin, but the extra auxin inhibits growth causing cells on upperside to elongate faster and roots bend downwards.

42
Q

What are the three plant hormones and their uses?

A

Auxins- Stimulate growth, promoting root growth and delaying ripening.
Ethene- Causes plant fruit to ripen by stimulating starch to sugar conversion. Used to ripen fruit
Gibberellins- They are used to control dormancy

43
Q

How can farmers produce seedless fruit?

A

One way is using auxins. seeds are produced after plant is pollinated by insects or the wind. If auxins applied to unpollinated flowers plant produces seedless fruit.

44
Q

Why is normal body temperature important?

A

37c is most optimum body temperature as enzymes work most efficiently.
If too low, enzyme reactions are too slow, respiration dosent release enough energy cells begin to die, below 35c
If too high, 40-42c enzymes may denature, body reactions cant occur

45
Q

How is internal body temperature monitored?

A

Hypothalamus contains thermoreceptors that are sensitive to blood temperature in the brain.

46
Q

How is external body temperature monitored?

A

Thermoreceptors in your skin monitor external temeprature and send messages to the hypothalamus in the brain.

47
Q

What happens when hypothalamus detects a change in temperature?

A

When change detected, brians sends impulses to effectors, these responses return body temperature to normal.

48
Q

What happens when you’re too hot?

A
  • Hair erector muscles relax hair lays flat, no insulated layer of air around bodu
  • Sweat glands produce sweat, water in sweat evaporates energy transferred from body to environment
  • Blood vessels near skin widen, vasodialation, increase bloodflow increases heat loss by radiation
49
Q

What happens when you are too cold?

A
  • Hair erector muscles contract, hairs stand up trapping air creaating inuslated layer of air
  • Little sweat produced, so no enrgy is lost
  • Blood vessels near skin narrow, vasconstriction, reducing bloodflow reducing heat lost by radiation
  • Shivering, rapid contractions of muskce require energy, body respires quickly, respiration exothermic reaction, energy transferred to warm body
50
Q

Why are is it important for blood glucose levels to remain constant?

A

Glucose in an energy store and is converted to ATP which is used by cells. If too little gluose, no energy in cells, respiration can’t occur properly. If too high, body systems can be damaged, nerves and blood vessels.

51
Q

What’s insulin and why is it important?

A

Insulin is a hormone released by pancreas,when blood sugar levels are too high. It stimulates liver to turn glucose to glycogen.

52
Q

What happens when blood sugar levels are too low?

A

If blood sugar levels are too low, pancreas releases glucagon. Glucagon makes liver convert glycogen to glucose returning blood sugar levels to normal.

53
Q

What happens when blood sugar levels are too high?

A

If blood sugar levels are too ow, it is detected by pancreas and insulin is released. This stimulates liver to convert glucose to glycogen. returning blood sugar levels to normal. Glycogen is stored in the liver

54
Q

Whats effects of type 1 diabetes?

A
  • People with type 1 diabetes can’t produce insulin
  • Their immune system destroyed pancreatc cells
  • Usually from childhood
  • Controlled by regualr insulin injections
55
Q

What are effects of diabetes type 2?

A
  • People with type 2 cant effectiely use insulin
  • persons cells don’t produce enough insulin or dont respond to insulin
  • Regulated by carb intake and matching it to exercise levels
56
Q

List a few ways water is lost from the body?

A
  • Through sweating
  • Through urine
  • Water vapour leaves as you breathe out
57
Q

Why is it important for water levels in blood plasma to stay constant?

A
  • If too much water present it moves into blood cells, causing them to swell and can burst, this is known as lysis
  • if too little water present, water diffuses out of blood cells, causing them to shrink
58
Q

How’s urine produced?

A

Small molecules, water, glucose,saltsand urea passinto kidney tubes, blood cells are too large they stay in capilllary.
kidneys then put back any useful substances in the blood, selective reabsorption.

59
Q

What’s selective reabsorption?

A

Process in which kindeys put back or reabsorb any useful substances back into the blood after uktrafilteration occurrs.

60
Q

What are the 3 main sections of a kidney?

A

Capsule - Outer membrane of kidey, maintains its shape and protects it from damage
cortex - outer part of kidney
medulla - inner part ot kidney

61
Q

In which structures in the kidney is urine produced?

A

In microscopic tubles, called nephrons. Top of nephron found in cortex, lower section found in medulla

62
Q

Which blood vessels allow blood to enter and exit the kidney?

A

Renal artery allows blood to enter.

Renal vein allows blood to leave

63
Q

Why are blood vessels narrow at exit of glomerulus?

A

This increases the blood pressure, the high pressure forces small molecules inclding, water, salts, glucose and urea out through capillary wall into bowmans capsule.

64
Q

What is the sturcture of a nephron?

A

NEED TO INSERT IMAGE

65
Q

Whaat happens in a nephron?

A

First, ultrafilteration occurs in the bowmans capsule and glomerulus. Then selective reabsorption occurs in first coiled tube. Lastly, salt and water regulation occurs in the loop of henle and collecting duct.

Ocr Gcse Biology (4 decks)

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