B3 Flashcards
What are sensory neurones?
- neurones that carry electrical impulses from the receptor cells to the CNS
What is the nervous system?
The nervous system consists of the brain and spinal cord which form the CNS and also several other neurones which respond to changes in the external environent
What are relay neurones
- neurones that carry the electrical impulses from sensory to motor neurones (in the CNS)
What are motor neurones?
- neurones that carry impulses from the CNS to the effectors
What are receptors?
- groups of cells that detect a stimulus
What are effectors?
- muscles or glands
- will either contract or release a hormone
What is the CNS
- the CNS is made up of the brain and spinal cord
What is a reflex action?
- an automatic/ involuntary action
- occur without thinking
- impulse will not go to brain
- e.g: Stimulus -> Receptor Cells -> Sensory Neurone -> Spinal Cord -> Motor Neurone -> Effector -> Response
- much faster by not using brain
Reflexes Practical?
- ruler drop time
- can be affected by levels of caffeine, mass of ruler, which hand
- use v2 - u2 = 2 to work out time
What does the cerebellum do?
- co-ordinates muscular activity + balance
- controls involuntary movements
What does the cerebal cortex manage?
- memories
- personality and complex emotions
- learning and conscious thought
What does the medulla do?
- controls essential automatic actions
- such as breathing and heart rate
What does the hypothalmus do?
- regulates temperature
- regulated water balance
What does the pituary gland do?
- known as the master gland
- stores and releases many hormones
How can you scan the brain?
- CT/ X-RAY scans (risk of radiation exposure)
- MRI (less risk of any radiation)
- Damage to the brain can be used to find brain functions
What is the sclera?
- tough white layer of the eye that protects it from damage
What is the cornea?
- transparent front part of the sclera that refracts light into the pupil
What is the pupil?
- The hole in the center of the eye through which light passes through
What is the iris?
- rings of muscles that control the size of the pupil
What is the retina?
-an area of light receptive cells at the back of the eye
What are receptor cells for colour in the eye?
- cone cells
- 3 types for red green and blue
What is the optic nerve?
- nerve which sends signals to the brain from the eye
What are rod cells?
- receptor cells which are sensitive to dim and bright light
What happens when there is low levels of light?
- Radial muscles contract
- Circular muscles relax
- more light is let in as pupil dilates
What happens when there is high levels of light?
- radial muscles relax
- circular muscles contract
- less light is let in as pupil constricts
What happens to the lens for far objects?
- suspensory ligaments contract
- cilliary muscles relax
- lens becomes flatter and there is less refraction of light
What happens to the lense for near objects?
- suspensory ligaments relax
- cilliary muscles contract
- lens becomes more thick and contracts and there is more light refraction
What is myopia?
- the lens is too curved/ the eyeball is too long
- this means the light refracts before the retina
- light is refracted too much
- can be fixed using concave lens
What is hyperopia?
- lens is too thin or eyeball is short
- light refracts too far on the retina
- light is not refracted enough
- can be fixed using convex lens
Differences between endocrine system and the nervous system
- hormones are chemical messengers (nervous system is electrical)
- Hormones are slow acting
- Hormones are long lasting
- Hormone travel in the blood
- Hormones are secreted in glands
What is the endocrine system?
- name given to all the endocrine glands and the hormones they produce
Thermoregulation
The body needs to be maintained at about 37 degrees fro optimum enzyme activity
Homeostasis?
The maintaining of internal body conditions even when external and internal environments change
Thermoregulation cycle?
Receptors (blood vessels, skin) notice temp change -> Thermoregulation centre in Hypothalamus -> response from effectors
What happens when the body is cold?
- Contract Erector muscles to raise hairs (creates small layer of insulating hair
- Blood Vessels will constrict (vasoconstriction) to increase distance from skin so less heat is lost to the environment via the skin
- We do more cellular respiration in the muscles so we shiver and contract more giving off thermal energy as a waste product
What happens when the body is too warm ?
- Erector muscles relax, hairs go down, no layer of insulating air
- Blood vessels will dilate (vasodilation) to decrease distance from skin so more heat is lost to environment via skin
- sweat is produced (water+salt) and because it evaporates heat is taken with it, as it taken energy/heat energy to evaporate the sweat
What happens after we eat
Glucose levels in the blood increase (constant high blood sugar) is bad for you
How do we combat increased blood glucose levels
- Pancreas detects this change and releases the hormone INSULIN which reduces blood glucose levels by stimulating an enzyme reaction to turn excess glucose into GLYCOGEN in the liver
- glucose goes from blood to cells
How do we combat decreased blood glucose levels
- Pancreas detects the change and releases hormone GLUCAGON which stimulates the reaction to turn glycogen into glucose in the liver cells
- This is then used for respiration
- glucose goes from cells to blood
what is Diabetes?
a disease where the body cannot regulate blood glucose levels
Difference between Type 1 and Type 2 Diabetes?
Type 1 is a lifelong condition you are born with where the body immune system attacks the cells that make insulin
Type 2 is a condition that comes later in life when the body becomes resistant to insulin
How treat Type 1 Diabetes?
Insulin Injections, good diet and exercise
How to treat Type 2 Diabetes?
Low Sugar diet with regular effect NO EFFECT WITH INSULIN INJECTIONS
Regulating Water levels?
water levels are regulated in the kidney and in the brain
Lack of water in the blood?
- Decreased water concentration detected in the hypothalamus
- more ADH released (pituitary gland)
- more reabsorbed in the blood from the nephrons
Too much water on the blood?
- increased water concentration detected in the hypothalamus
- less ADH released (from the pituitary gland)
- less water reabsorbed into the blood
Thyroid gland?
- In the neck
- releases hormone thyroxine
- this controls metabolism
Adrenal Gland?
- on top of kidneys
- releases adrenaline
- prepares flight or fight response
Pancreas
- secretes insulin
- controls blood sugar
Pituary Gland?
- stimulates stimulation of other hormones in different glands
What does FSH do ?
- stimulates the release of oestrogen
- matures the egg cell
- Peaks at day 0 and lowest at day 14-21
- produced in the pituary gland
What does Oestrogen do?
- inhibits the release of FSH
- stimulates the release of LH
- causes the uterus lining to thicken
- secreted in the ovaries
- day 7-21 peak
What does LH do?
- secreted in the pituary gland
- stimulates ovulation
- day 14 peak
What does progesterone do?
- if pregnant inhibits LH and FSH and levels of P will be high
- if pregnant will maintain uterus lining
- if pregnant allows mucus to form a lining at the cervix
- secreted from the empty egg follicle
- If no fertilisation takes place from day 28, the uterus lining and egg will be pass out the vagina AS PROGESTRONE WILL cease to release
- cycle restarts
Forms of contraception?
- combined pill - oestrogen + progesterone (inhibits FSH and LH, egg inhibited) has to be taken everyday, bad side effects such as increased BP
- pill only - progesterone (mucus layer, plus inhibition), less side effects
- spermicides, chemicals that destroy sperms
- condoms, stop STD’s and sperm, no side effects
- IUD, lasts 2-5 years can contain progesterone
- Abstinence - avoiding sex, religion
- surgery - permanent sterilisation
Fertility Drugs?
- for females who may not be able to ovulate
- contains FSH and LH to mature drugs and to ovulate
Blocked Oviduct Fertility Issue?
- Fertility drugs are given to mature and release eggs
- eggs are taken and mixed with sperm outside the body
- fertilised eggs/uterus are then syrigned into uterus (IVF)
- solves fertility
- expensive
- embryos can be stored
- limited success rate
- unused embryos can be donated
- mentally and physically draining
- IVF can lead to multiple births
What is negative feedback?
- a homeostatic mechanism where the body detects a change and makes an adjustment to return to normal
Thyroxine Feedback loop?
- If thyroxine levels in the body increase the brain will detect this
- It will send a signal to a motor neurone to a gland (effector), the pituary gland
- The pituary gland will release less TSH (thyroxine stimulating hormoe) which will stimulate less thyroxine to be produced
- This can be done vice versa for too little thryoxine
Effect of Adrenaline?
- pupils dilate to let more light in
- heart rate increases (to pump blood faster)
- glycogen reserves in muscle cells break down (to release more glucose for more respiration)
- Blood from the digestive system is redirected to skeletal muscles
- breathing rate increases to get more oxygen in
Why could there (diet related) not be enough thyroxine?
- lack of iodine, used to make thyroxine
What is the effect of less thyroxine?
- lower metabolism
- lower levels of protein synthesis
- vice versa
What happens if water potential in blood is too high (red blood cells)
- red blood cells with lyse(burst)
What happens if water potential in blood is too low (red blood cells)
red blood cells will shrink and shrivel
Process of Excretion?
- each kidney is supplied with oxygenated blood via the aorta/renal artery
- kidney cleans the blood, removing excess water, urea and salts
- the cleaned blood is sent back to the heart via the renal vein/vena cava
- the waste is sent to the bladder (urine)
What is phototropism?
growth in response to light
What is gravitropism?
growth in response to gravity
What do Auxins do?
- in roots they slow down/inhibit growth
- in shoots they stimulate growth
- auxins will move towards the darker side of the shoot to bend it towards the light
Uses of Auxins?
- selective weedkiller for broad leave plants, will grow too fast and die
- used for rooting powder
Uses of Giberellins?
- help with seed germination
- can induce flowerings
- growing larger seedless fruits
Use of ethene?
- induces ripening
- ethene inhibitors can delay ripening
