Biology- Unit 9 Flashcards
Where are hormones secreted from?
Endocrine glands
What are the two modes of hormone action?
1) Bind to a receptor on the target cell membrane which stimulates the release of a second messenger which activates enzymes
2) Pass through the cell membrane and bind to a receptor inside cell, forms hormone-receptor complex which passes into nucleus and acts as transcription factor
What are the functions of auxins?
Growth stimulant
Maintain apical dominance
Promote root growth
Promote trophic responses (directional growth)
Can be used as weed killer and rooting powder
What do auxins do to achieve this?
Cause cell elongation via AT of H+ into cell walls = more acidic
More acidic = more flexible = more stretch to accommodate more water
What are the functions of gibberellins?
Stimulate elongation at cell internodes
Stimulate growth of fruit
Stimulate germination
Stimulate rapid growth / flowering
How does gibberellins stimulate germination?
Seed absorbs water, activates embryo Embryo secretes gibberellins G diffuses into aleurone layer Aleurone layer produces amylase Amylase diffuses into endosperm and breaks down starch into glucose
What are the functions of cytokinis
Promote cell division / lateral bud development
Works with ethane to promote abscission of leaves
What are the two forms of phytochrome
Pr = inactive, absorbs red light (sun) Pfr = active, absorbs far red light
In long-day plants, Pfr…?
Stimulates flowering
In short-day plants, Pfr…?
Inhibits flowering
What does a plant look like when kept in the dark
Only has Pr Tall and thin Fragile stems Yellowed leaves Little root growth
What systems form the peripheral nervous system?
Autonomic (non-conscious)
Sympathetic (fight/flight)
Parasympathetic (rest/digest)
Voluntary (conscious)
What is the neurotransmitter for the sympathetic system?
Noradrenaline
Ganglia close to CNS
What is the neurotransmitter for the parasympathetic system?
Acetylcholine
Ganglia far from CNS
What is the function of the hypothalamus?
Thermoregulation
Osmoregulation
Hormone secretions
What is the function of the cerebellum?
Smooth movements
Balance
Posture
What is the function of the cerebrum?
Voluntary behaviour
Personality
What is the function of the medulla oblongata?
Breathing
Heart rate
Peristalsis
What is the function of motor neurones?
Transmitting potential differences from CNS to muscles and glands
What is the function of sensory neurones?
Transmit impulses from receptor cells to CNS
What is the function of relay neurones?
Located within CNS
Transmit impulses from sensory to motor
What is the resting potential value?
-70mV
What is the function of the myelin sheath?
Insulator of axon and dendron
Salutatory conduction
What is the effect of nicotine on the nervous system?
Mimics acetylcholine
Triggers release of dopamine
In high doses, blocks acetylcholine receptors
What is the effect of cobra venom on the nervous system?
Binds to and blocks acetylcholine receptors
What pigment do rods contain?
Rhodopsin
Splits into retinal and opsin
What happens to rods in the dark?
Rods aren’t stimulated- sodium ions diffuse into the cell through channels whilst being pumped out via AT
The inside of the cell is only slightly more negative
Membrane slightly depolarised
Glutamate released- inhibit rod neurones
No info goes to brain
What happens to rods in the light?
Rhodopsin splits into retinal and opsin - bleaching
Opsin binds to membrane of cells closing the Na+ channels
Cell membrane becomes hyperpolarised
Action potential forms and is transmitted to brain
What factors increase heart rate?
Low pH
Stretch receptors
Decrease in BP
Adrenaline
How is a low blood pH detected?
Chemoreceptors in arteries, aorta and brain
Send impulses to medulla oblongata
How does heart rate increase?
Receptor sends impulse to cardiac control centre in medulla oblongata
Impulse sent to SAN along sympathetic neurone
Depolarisation occurs
Noradrenaline released at SAN
How does heart rate decrease?
Receptor sends impulse to cardiac control centre in medulla oblongata
Impulse sent to SAN via parasympathetic neurone
Depolarisation occurs
Acetylcholine released at SAN
What is deamination?
Liver- hepatocytes
Amino acids converted into urea
Amine group is removed to form ammonia
Ammonia converted into urea- Orithine cycle
Why is ammonia converted into urea?
Ammonia is extremely toxic
Describe ultrafiltration
Occurs in glomerulus and bowman’s capsule
Small molecules forced out of vessel under high pressure
Afferent arteriole (entering) is wider than efferent arteriole (leaving)
Where does selective reabsorption occur?
Proximal convoluted tubule
All glucose and amino acids reabsorbed by FD and AT
Water diffuses via osmosis
What occurs in the loop of henle?
Medulla extremely low water potential
Descending limb- permeable to H2O
Ascending limb- not permeable to H2O
Water moves through aquaporins via osmosis into low WP in medulla
Ascending limb-
Ions move via FD into medulla to maintain WP in descending
Upper ascending = AT of ions
What occurs in the distal convoluted tubule?
Secretes waste like creatine into filtrate
Actively transports ions
Helps control blood volume
Regulates pH
What occurs in the collecting duct?
ADH
Osmoreceptors in hypothalamus detect water potential
More ADH = more permeable = more reabsorption
What is an ecotherm?
Organism that cannot regulate its body temperature
What is an endotherm?
Able to maintain a constant body temp
Contain thermoreceptors
Hypothalamus
Restore optimum temp
What can endotherms do to regulate heat?
Shivering - increases
Sweat glands - decreases
Hairs - increases
Arterioles - vasodilation/ constriction
