Cells/Homeostatis/Excretion/Nerves/Eyes

Question 1

Levels of organisation:
Organelles: microscopic structures within cells (e.g nucleus)
Cells: different adaptions for different jobs
Tissues: made of cells. Has function/structure e.g nerves/muscle/vascular
Organs: made of tissues. Carry out specific functions. Heart pumps blood. Made of vascular tissue
Systems: organs link to form systems e.g nervous/excretory/respitory

Answer 1

Cells:
Animal cells- cytoplasm/membrane/nucleus containing chromosomes
Plants cells- cytoplasm/membrane/nucleus/cell wall/sap vacuole/chloroplasts

Question 2

Diffusion:
- movement of molecules from an area for high to low concentration. Steeper gradient = faster diffusion
Inc in temp speeds up net movement of diffusion
The larger the cells the less effective it is
The higher the SA-V ratio the better
Unicellular organisms can live off diffusion of food but can only grow to a certain size
Multi celled organisms need transport system to carry diffused substances around

Answer 2

Active transport- sometimes cell needs to take substance against concentration gradient - requires energy from respiration
Occurs in: roots of plants for minerals/small intestine- glucose from gut to blood/nerve cells:sodium pumped
Osmosis- movement of water from higher to lower water potential through a semi permeable membrane. OR movement of water from low to high solute concentration through a semi permeable membrane

Question 3

Excretion/kidneys:
Excretion: removal of metabolic waste = chemical water
Organs: kidney/skin/lungs. Waste: Urea/water/CO2. Plants: oxygen
Function of kidney- excretion of urea/osmoregulation/acid, base and ionic balance
Urea - H,C,O,N excess N = toxic. Amino acids broken down in liver and passes into blood
Overview: blood enter at high pressure through renal artery/out through renal vein, urine formed and passes through ureter and store in bladder. Held by sphincters. Out thru urethra

Answer 3

Osmoregulation-
-Body controls water content via kidney
- special cells in hypothalamus detect water in blood. pituitary gland releases ADH
- travels to collecting duct to reabsorb more/less water. Makes it more/less permeable
Decreased level in blood ~more ADH~more reabsorbed~ less excreted. Inc level = opposite
Example of negative feed back where the body tries to maintain normal levels

Question 4

Homeostasis
- maintaining a constant internal environment regardless of external environment. Water, O2 CO2 glucose pH, salts and temp need maintaining
Stimulus (e.g. Temp)~ receptor(skin)~ coordination(hypothalamus)~ effector~ response(vasodilation/vasoconstriction)
Osmoregulation and monitoring body temp = homeostasis

Answer 4

Skin:
Functions: Barrier to pathogens/sensing temp changes- cont heat loss/ preventing water loss
Sweating= too hot/will evaporate using heat which cools us down
Vasodilation/vasoconstriction: control size of vessels near skin. V.D = opening of blood vessels~extra heat loss~ cools down. V.C is Op
Hormones- testosterone/testes/male puberty, oestrogen/ovaries/female puberty, adrenaline/fight flight response/adrenal gland. Bl.Gl high = insulin. Bl.Gl low- glycogen.

Question 5

Nerves/hormones:
Nervous response= quick/temporary/reversible. Travels to specific organ via electrical impulses by neuron
Hormonal response= slow/permanent/irreversible.Chemical signal via blood to w.body
C.N.S = brain and spinal cord. Peripheral nervous system from sense organs to C.N.S to effectors( muscles)
Stimulus(high heat)~ pain receptor stimulated~ signal sent along sensory neurone~ passed along relay neurone to brain~ along motor neurone to effector muscle

Answer 5

Reflex pathway:
Quick response in danger/ signal passed directly: sensory neurone~ relay~ motor neurone= instant involuntary action. Innate behaviour.
Neurone surrounded by substance called myelin sheath which insulates.
Neurones- transmit impulses around body at 10- 100 m/s

Question 6

The eye:
Rods and cones- Rods work in dim light and black and white. Cones work in bright light. 3 types = red/blue/green
We see by the image refracting of the cornea then lens onto fovea
Cornea- refracts light and protects eye
Lens- focuses light onto retina
Fovea- area of retinal with most cone cells
Pupil- lets light in. Ciliary muscles- change lens shape. Aqueous humour - maintains pressure

Answer 6

Iris/accommodation
Iris: changes pupil size:. Controls light amount entering eye. Uses circular and radial muscles
Dim light: Rc, Cr, Pd. Bright light: Rr, Cc, Pc
Accommodation: focuses eye on near and far objects. Lens changes shape. C muscles and suspensory ligaments
Distant objects: Cr , Sl, Lt
Close objects: Cc , Ss, Lf

Question 7

Hormones in plants:
Control growth- roots/shoots/seed germination/leaf fall/disease resistance/fruit formation/flowering time/bud formation
Auxins- group of chemicals that influences growth/development.
Sunlight breaks them down. More auxins = more growth. From angle = lopsided growth and plant bends towards light. Straight sunlight keeps plant straight

Answer 7

Tropism: 
Respond to stimuli: water/light/gravity
Direct response to stimuli= tropism
Towards= positive/ away= negative
Shoots/stems= positive photo and neg geo
Roots = positive geo and neg photo 
Hydrotropism= movement towards water

Question 8

Nephrons- each kidney has over 1 million
- supplied by network of capillaries
- blood passes through ~ 400 times per day
- excess water + water removed from blood, enters nephron and excreted as urine
- collecting ducts from nephrons join to make ureter
Urine - ureter > bladder > urethra

Answer 8

Process- arteriole brings blood renal artery > bowmans capsule
- n.o.c called glomerulus. Vessels wider entering than when leaving= pressure gradient = ultrafiltration - pushed through at high pressure
Glomerular filtrate = water/glucose/urea/ amino acids/electrolytes. NO CELLS OR PROTEINS
Proximal convoluted tubule - selective reabsorption of glucose by active transport
Loop of henle - reabsorbs water. Collecting duct/ distil convoluted tubule reabsorbs water. ADH responsible