Homeostasis Flashcards
(116 cards)
1
Q
Homeostasis
A
The regulation of conditions to maintain a stable internal environment, in response to internal and external conditions
2
Q
Stimulus
A
A change in the environment
3
Q
Receptor
A
An organ, tissue or cell that detects a stimulus
4
Q
Coordination Centre
A
Receives receptor information, processes it and initiate a response, (brain, spinal cord)
5
Q
Effector
A
An organ, tissue or cell that produces a response (either muscles contracting or glands secreting a hormone)
6
Q
Synapse
A
A tiny gap between 2 nerve cells which signals must cross
7
Q
Sensory Neurones
A
Carry impulses from the receptors to the CNS
8
Q
Motor Neurones
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Carry impulses from the CNS to the effectors
9
Q
Nervous System Order
A
Stimulus - Receptors - Sensory Neurones - Coordination Centre (found in CNS) - Motor Neurones - Effector - Response
10
Q
Reflex Arc
A
Nerve Pathway that underlies unconscious reflexes
11
Q
Reflex Action
A
An automatic, rapid response to a stimulus which minimises any harm to the body
12
Q
Cerebrum (Cerebral Cortex)
A
Responsible for:
- Consciousness
- Intelligence
- Memory
- Language
- Senses (sight, hearing, taste, etc)
13
Q
Cerebellum
A
Responsible for:
- Balance
- Muscle coordination
14
Q
Hypothalamus
A
Responsible for:
- Regulating body temperature
- Sends signals to pituitary gland
15
Q
Medulla
A
Responsible for:
- Unconscious activities (e.g. breathing, heart rate)
16
Q
How do scientists study brain?
A
- By studying people with brain damage
- By electrically stimulating different parts of the brain
- MRI scans
17
Q
How do scientists study brain damage?
A
For example, if someone had a stroke which caused hearing loss, scientists would know the part of the brain responsible for hearing is damaged
18
Q
How do scientists electrically stimulate different parts of the brain?
A
- Brain is stimulated using electrodes
- Stimulating certain areas creates certain reactions from the body
- From this scientists can tell what that part of the brain is responsible for
19
Q
How do MRI scans work?
A
- Show details of brain structure and function
- Patients are asked to perform various tasks
- By looking at the scan, scientists can see which parts of the brain are active when the task is carried out
20
Q
Risks of treating the brain
A
- Brain surgery can cause damage or side effects that can ruin a patient’s quality of life
- Surgery risks (tumours, infection, brain trauma)
- Brain is very complex and fragile so treating brain damage is difficult
21
Q
Cornea
A
- Refracts (bends) light as it enters the eye
- Transparent to let light enter
- Contains no blood vessels, O2 diffuses through it
22
Q
Iris
A
Controls how much light enters the eye
23
Q
Pupil
A
Gap in the centre of the iris that allows light to pass through to the lens
24
Q
Lens
A
Changes shape to further refract light so it focuses on the retina
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Retina
Contains light receptors that help to see colour
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Optic Nerve
Carries impulses between the eye and the brain
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Sclera
Tough white outer layer of the eye that protects the eye from injury
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Iris Reflex in bright light
- Reflex constricts the pupil (makes it smaller)
- Allows less light to pass through to the lens
- Prevents eye damage
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Iris Reflex in low light
- Reflex dilates the pupil (makes it bigger)
- Allows more light to pass through to the lens
- Allows us to see more clearly in the dark
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Iris Reflex in low light
- Reflex dilates the pupil (makes it bigger)
- Allows more light to pass through to the lens
- Allows us to see more clearly in the dark
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Near Objects
- Ciliary Muscles contract
- Suspensory Ligament
slackens
- Lens thickens and strongly refracts light rays
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Distant Objects
- Ciliary Muscle relaxes
- Suspensory Ligament pulled taught
- Lens thins and slightly refracts light rays
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Hyperopia (Long-Sightedness)
- Light rays don't refract enough
- Image appears behind the retina
- Can't focus on nearby objects
- Fixed using a convex lens
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Myopia (Short-Sightedness)
- Light rays refract too much
- Image appears in front of the retina
- Can't focus on distant objects
- Fixed using a concave lens
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Other ways to correct vision
- Hard and soft contact lenses
-Laser surgery to change the shape of the cornea
- Replacement lens in
the eye
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Thermoregulation
The regulation of internal body temperature
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Where is the thermoregulatory centre found?
In the hypothalamus
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How do our bodies warm us up?
- Vasoconstriction (prevents heat loss through skin)
- Hairs stand up (trap insulating layer of air)
- Shivering (heat energy is released to warm us up)
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How do our bodies cool us down?
- Vasodilation (causes heat energy loss)
- Erector muscles relax (hairs lie flat)
- Sweat - a mix of water and urea (evaporates and carries heat energy with it)
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Pituitary Gland
Located below the centre of the brain and secretes many hormones
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Thyroid
- Produces thyroxine
- Thyroid regulates metabolism
- Found in the neck
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Adrenal Glands
- Produce adrenaline (released during fight or flight)
- Increases heart rate
- Above the kidneys
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Pancreas
- Produces insulin + glucagon (lowers/raises blood glucose concentration)
- In front of the kidneys
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Testes
- Only in males
- Produces testosterone (controls puberty)
- Produces male gametes (sperm)
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Ovaries
- Only in females
- Produces oestrogen (controls puberty + menstrual cycle)
- Produces female gametes (eggs)
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Differences between Endocrine and Nervous Systems
Endocrine:
- Relies on hormones that travel in the bloodstream
- Slower
- Hormones last longer
- More general
Nervous:
- Relies on electrical impulses that travel through neurones
- Faster
- Don't last long
- More precise
46
How does insulin lower
blood glucose levels?
- Insulin binds to receptors on muscle + liver cells
- Those cells take in glucose and store it as glycogen
- This lowers BGC back to normal
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How does glucagon raise blood glucose levels?
- Insulin binds to liver receptor cells
- Those cells break down glycogen into glucose and release it into the bloodstream
- This raises BGC back to normal
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Type 1 Diabetes
- Starts at and early age but affects are lifelong
- The pancreas stops producing insulin so BGC becomes to high and isn't lowered
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Type 2 Diabetes
- Happens at older age
- The body stops responding to insulin so cells don't take in glucose
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Type 1 Diabetes Treatment
Insulin injections into the abdomen/thigh
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Type 2 Diabetes Treatment
- Healthy, low sugar diet
- Lots of exercise
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Role of the kidneys
- Filter the blood and remove any waste products from it
- Regulate levels of ions + water
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Deamination
- Where excess amino acids are converted into fats and carbohydrates for storage
- Takes place in the liver
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Where is urea made?
In the liver during deamination
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How does water leave the body?
- Sweat
- Through the lungs when breathing
- Through urine
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Why is water regulation important?
- Cells lose/gain water depending on how much water is in the body
- An excess of water means it enters the cells through osmosis and damages them or causes them to burst
- A lack of water means water leaves the cell making it flaccid
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How do the kidneys filter the blood?
- Selective reabsorption
- As blood passes through the kidney, tubules absorb all small molecules
- Things that are good for the blood (all glucose and some water) are reabsorbed back into the blood
- Urea isn't reabsorbed but excreted
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What happens when there is too little water in the bloodstream?
- The hypothalamus signals the pituitary gland to release more ADH
- ADH enters the kidneys and alerts the tubules to reabsorb more water
- Less urine is produced
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What happens when there is too much water in the bloodstream?
- The hypothalamus doesn't signal the pituitary gland to release ADH
- Less ADH enters the kidneys so less water is reabsorbed
- More urine is produce
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Kidney system
- Blood enters through renal artery and exits through renal vein
- Kidneys produce urine
- Urine passes though the ureters and is stored in bladder
- Excreted through urethra
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Consequences of kidney failure
- Waste substance aren't removed from the body
- Ion and water levels aren't regulated
- Causes illness and death if untreated
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Dialysis
Medical treatment where blood is removed, filtered and put back in the body
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How does dialysis work?
- Blood passes through dialysis machine and makes contact with dialysis fluid
- Blood and fluid separated by partially permeable membrane
- Ions, water and glucose diffuse in and out of the blood so a good concentration of all is created in the blood
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Why is dialysis fluid constantly replaced?
- To created a constant concentration gradient
- Without one, eventually the molecules wouldn't diffuse in and out of the blood
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Disadvantages of dialysis
- Treatment is time consuming
- Dialysis can cause blood clots and infection
- Dialysis is a life process (has to be done regularly for life)
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Kidney transplant
Surgical procedure where the kidney is replaced
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Disadvantages of kidney transplants
- Organ may be rejected by recipient's immune system
- Drugs are given to stop this but it weakens the immune system and increases chance of illness
- Surgical risks (surgery could go wrong)
- Lack or organ donors
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Puberty
Period where adolescents start to develop secondary sexual characteristics
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What are the 4 stages of the menstrual cycle?
- Menstruation
- Uterus lining develops
- Ovulation
- Uterus lining maintained
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Menstruation
- Between days 0-7
- Uterus lining breaks down
- Bleeding as a result
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Lining builds up
- Between days 7-14
- Lining becomes a thick spongy layer with lots of blood vessels in it
- This prepares the lining for a fertilised egg
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Ovulaltion
- On day 14
- Egg is released from the ovary
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Lining is maintained
- 14-28 days
- If no egg has been fertilised by day 28, menstruation occurs (cycle repeats until fertilised egg)
- If an egg has been fertilised before day 28, it implants itself into the womb to develop into a foetus
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Follicle Stimulating Hormone
- Causes egg to mature in ovary
- Stimulates oestrogen
- Produced in pituitary gland
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Oestrogen
- Repairs, thickens and maintains uterus lining
- Stimulates LH
- Inhibits FSH
76
Luteinising Hormone (LH)
- Triggers ovulation
- Produced in the pituitary gland
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Progesterone
- Maintains uterus lining
- Produces mucus in the cervix
- Inhibits LH and FSH
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Contraception
Any method used to prevent pregnancy
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Hormonal Methods
Rely on the release of oestrogen/progesterone to prevent the release of an egg
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Oestrogen Pill
- Taken everyday to inhibit FSH
- Inhibiting FSH means no egg is matured or released
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Progesterone Pill
- Releases progesterone
- This produces a thick mucus in the cervix
- Sperm can't reach the egg
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Combined Pill
- Contains progesterone and oestrogen
- Very effective but has side effects
- E.g. headaches, nausea
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Contraceptive Patch
- Placed on the upper arm
- Releases progesterone and oestrogen
- Lasts 1 week
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Contraceptive injection
- Progesterone is injected in the upper arm
- Lasts 2-3 months
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Contraceptive Implant
- Placed under the skin in the arm
- Slowly releases progesterone
- Lasts 3 years
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IUD (Intrauterine Device)
- Placed inside the uterus
- Releases progesterone
- Lasts over 3 years
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Non-Hormonal Devices
Prevents the sperm from reaching the egg and fertilising it
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Copper IUD (Copper Coil)
- Prevents sperm from surviving in the uterus by killing them
- Lasts over 3 years
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Condoms
- Acts a barrier and traps sperm
- Only form of contraception that protects against STD's as well
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Diaphragm
- Fits over the cervix
- Blocks sperm from entering the uterus
- Unreliable so is used with spermicides
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Sterilisation
- Cutting the fallopian tubes (women)
- Cutting the sperm ducts (men)
92
Natural methods
- Intercourse only at certain times of the month
- Withdrawing before ejaculation
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Abstinence
- Refraining from intercourse
- Only method that has a 100% success rate
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Infertility Problem
- Low production of FSH so egg doesn't mature properly or at all
- FSH and LH are given in pill form to mature and release eggs
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How IVF (In Vitro Fertility) works
- FSH and LH are given in pill form to mature and release eggs
- Eggs are collected and fertilised with father's sperm in a lab
- Fertilised eggs are placed in an incubator and grow into embryos
- One or more embryos are inserted into the uterus to grow into foetuses
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Pro of IVF
- Allows infertile couples to have children
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Cons of IVF
- Doesn't always work (low success rate)
- Side effects (e.g. abdominal pains, vomiting)
- Multiple embryos can lead to multiple unwanted pregnancies
- Leads to higher risks of complications (stillbirths, miscarriage)
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Ethical issues
- IVF leads to destruction of unused embryos that had potential of life
- Could lead to designer babies
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Adrenaline
- Produced in the adrenal glands during 'fight or flight' response, when you're scared, stressed or are about to exercise
- Prepares the body for physical activity
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Adrenaline Impacts
- Increased heart rate
- Increased blood flow
- Increased blood flow to the muscles
- Increases glucose breakdown by stimulating the liver to breakdown glycogen
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Thyroxine
- Produced y the adrenal glands in the neck
- Main role is to increase metabolic rate
- Pituitary gland produces TSH which stimulates the thyroid to produce thyroxine
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What happens if thyroxine levels are too low?
- The pituitary gland produces more TSH
- This stimulates the thyroid to produce more thyroxine so levels increase to normal
103
What happens if thyroxine levels are too high?
- Thyroxine inhibits the production of TSH form the pituitary gland
- Less TSH means less thyroxine is being produced from the thyroid
- Levels fall to normal
104
Phototropism
Plant response to the stimulus of light
105
Geotropism/Gravitropism
Plant response to the stimulus of gravity
106
Auxins
- Control growth at the ends of shoots and roots of a plant
- Stimulates growth in the shoots
- Inhibits growth in the roots
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Shoots
- Positively phototropic (grow towards the light)
- Negatively geotropic (grow away from the ground against gravity)
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Direction of growth in plant shoot
- Towards the sun
- Auxin accumulates in the shaded side of a plant
- Auxin stimulates growth in shoots so shaded side will grow at a faster rate - towards the light
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Roots
- Negatively phototropic (grow away from light)
- Positively geotropic (grow towards the ground)
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Direction of growth in plant roots
- Constantly curves upwards and downwards
- Auxin accumulates on the lower side of root
- Auxin inhibits growth in roots so lower side grows at a slower rate and curves downwards
- Now there is more auxin in the upper side of the root so that side grows slower
- Root curves upwards
- Cycle repeats
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Uses of Auxin
- Growing plant clones in tissue cultures
- Used in rooting powder to grow plant cuttings
- Used to kill weed by disrupting their growth pattern
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Gibberellin
Initiates seed germination
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Uses of Gibberellin
- Controlling dormancy by inducing germination to produce multiple crops
- Induced flowering
- Used to grow larger fruit
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Ethene
Controls cell division and ripening of fruits
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Use of Ethene
Ripens fruit after it has been transported from different countries so it's fresh
