Bio Paper 2 Flashcards
What do Rod cells do
Black and white images, detect light of very low intensity due to retinal convergence
Uses rhodopsin
High sensitivity
What do cone cells do
Process images in colour
Red green and blue cells (each one absorbs diff wavelegth of light)
Requires high light intensity
Uses iodopsin
HIGH VISUAL ACUITY
Where are the majority of cone cells?
Near the fovea
Where is SAN located
In right atrium
Describe control of the heart
SAN releases impulse across atria
AVN then releases a second impulse
Bundle of His conducts impulse down the septum & Purkyne fibres
Apex and walls of ventricles contract
What controls the heart
Medulla oblongata - cardioregulatory centre:
* Sympathetic (increases heart rate)
* Parasympathetic (decreases heart rate)
Heart response to decreased pH
- Chemoreceptors detect drop in pH (during resp)
- Medulla sends impulse via sympathetic nervous system to SAN
- Increases fq of impulses so higher bpm so more resp (removes CO2)
Heart response to decrease in pressure
- Baroreceptors detect drop in pressure
- Medulal sends impulse via sympathetic nervous system to SAN
- Increases fq of impules so higher bpm so higher pressure
Describe the funciton of a synapse
- AP arrives at knob Ca2+ channels open and Ca2+ diffuses in
- Promotes aCh containing vesicles to fuse w presynaptic membrane
- ACh diffuses across and binds to complementary receptors
- Na+ channels open and Na+ enters postsynaptic
- ACh broken down and released closing channels. (ACh recycled in presynaptic)
Define spatial sumamtion
Multiple neurones release neurotransmitter to exceed threshold
Define temporal summation
Single neurone released neurotransmitter rapidly at a higher frequency to exceed threshold value
Z - line
I - band
M - line
A - band
H - band
At end of sarcomeres
Just actin filament
Middle line of sarcomere
Myosin filament (whole legnth)
Just myosin filament
How do muscles contract
- AP arries at SR
- Ca2+ ions released from SR
- Ca2+ bind to troponin causing tropomyosin to expose myosin binding sites
- Myosin head binds forming cross bridges this causes a powerstroke releasing ADP and Pi
- ATP binds to myosin heads causing them to release from binding site
- ATPase hydrolyses ATP causing myosin head to recock
Where are hormones produces
Glands
Describe second messenger model of adrenaline
adr binds to receptor
changes shape of protein
this ativates adenyl cyclase
converting atp inot cAMP
cAMP binds to kindase activating it
this catalyses conversion of glycogen into glucagon
How does insulin work
promotes vesicles containing transport proteins to fuse with membrane increasing uptake of glucose
Pathway of kidneys
renal artery -> afferent arteriole -> bowmans -> PCT -> Loop of henle -> DCT -> Collecting duct
What occurs in the bowmans capsule
Ultrafiltration of the blood - glucose, mineal ions and water are squeezed out to form the glomelular filtrate
Hydrostatic pressure forces small molecules through the gaps between endothelium cells, through the basement layerr and slits between podocyte cells
Describe selective reabsorption
Na+ moves into blood by active transport
Co-transport of Na+ and glucose into PCT cell
water follows by osmosis
loop of henle??????
na+ actively transported out of ascending limb
Low w.p inbetween two limbs so water leaved through the descending limb by osmosis
na+ diffuses out at the base of the ascending limb (into space near collecting)
water moves out out of collecting duct by osmosis
Fall in water potential??
due to heat/too little water being consumed
Osmoreceptors in hypothalamus detect
Hypothalamus releases ADH
goes to posterior pituitary gland where is its secreted
ADH increases permeability of collecting duct and dct by adding more aquaporins so more water reabsorbed
define codominance
both alleles are expressed in phenotype
eg: red coat, white coat, mixed colour coat
define epistasis
allele of one gene masks the expression of another
hardy weinberg?
p+q=1
p^2 + 2pq + q^2 = 1
what is variation due to?
mutations, meiosis (random assortment and crossing over), random fertilisation
3 types of selection?
stabilising
directional
disruptive
define allopatric speciation
speciation due to two populations being geographically seperated
define sympatric speciation
speciation due to two populations being reproductively seperated
eg: behavioural or mechanical
