Biology- Unit 9 Flashcards by Jasmine Greenhalgh

Where are hormones secreted from?

Endocrine glands

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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

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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

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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

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What are the functions of gibberellins?

Stimulate elongation at cell internodes
Stimulate growth of fruit
Stimulate germination
Stimulate rapid growth / flowering

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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

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What are the functions of cytokinis

Promote cell division / lateral bud development

Works with ethane to promote abscission of leaves

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What are the two forms of phytochrome

Pr = inactive, absorbs red light (sun)
Pfr = active, absorbs far red light

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In long-day plants, Pfr…?

Stimulates flowering

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In short-day plants, Pfr…?

Inhibits flowering

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What does a plant look like when kept in the dark

Only has Pr
Tall and thin
Fragile stems
Yellowed leaves
Little root growth

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What systems form the peripheral nervous system?

Autonomic (non-conscious)
Sympathetic (fight/flight)
Parasympathetic (rest/digest)
Voluntary (conscious)

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What is the neurotransmitter for the sympathetic system?

Noradrenaline

Ganglia close to CNS

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What is the neurotransmitter for the parasympathetic system?

Acetylcholine

Ganglia far from CNS

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What is the function of the hypothalamus?

Thermoregulation
Osmoregulation
Hormone secretions

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What is the function of the cerebellum?

Smooth movements
Balance
Posture

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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