Topic 6 Flashcards by Aaron Bokole

How does distribution of IAA in root cause root to bend downwards

IAA at bottom of root inhibits elongation of cells

IAA at top of root leads to elongation of cells

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How does IAA move from the growing regions of a plant shoot to the tissues

Diffusion

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When a shoot is illuminated on one side IAA stimulates growth on the shaded side

Why does growth on the shaded side help to maintain the leaves in a favourable environment

Cells elongate on shaded side causes shoot to bend towards light

Light used for photosynthesis

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How can temperature effect the rate that auxins are taken up

More kinetic energy

More diffusion

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How can a difference in properties of the cuticle explain lower surface intaking more auxins than upper surface

Thick waxy cuticle in upper surface and thin cuticle on lower surface

More diffusion as there is a shorter diffusion pathway on lower surface

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Taxis movement

Moving directly towards stimulus

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When an image is focused on the fovea , the person sees the object in colour

Explain why

Higher concentration of cones in fovea

Cones detect colour as they contain iodopsin

High cone density

Three types of cone cells

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Why does vision in the fovea have high visual acuity

Each receptor in fovea connected to separate neurone

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Why does vision using other parts of the retina besides fovea have high sensitivity to light

Many rods in other parts of retina

Rhodopsin is very sensitive to light

Receptors connected in groups to neurone

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Role of the sinoatrial node (SAN)

Initiates heartbeat

Sends wave of electrical activity

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The cardiac cycle is controlled by the SAN and the AVN

Describe how

SAN initiates heartbeat

SAN sends wave of impluses causing atrial contraction

AVN delays impulses

Allowing ventricles to fill before they contract

AVN sends wave of impluses down Bundle of His

Causing ventricles to contract from base up

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What is atheroma and how may it cause myocardial infarction

Cholesterol

In artery wall

Atheroma linked to blood clot

Blocks coronary artery

Reduces oxygen supply to heart muscle

Heart muscle unable to respire

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Explain how the heart muscle and the heart valves maintain a one way flow of blood from the left atrium to the aorta

Atrium has higher pressure than ventricle due to contraction causing AV valves to open

Ventricle has higher pressure than atrium due to contraction causing AV valves to close

Ventricle has higher pressure than aorta causing SL valve to open

Higher pressure in aorta than ventricle causing SL valve to close

Ventricular contraction causes increase in pressure

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How does increased exercise intensity lead to an increased HR

CO2 detected by chemoreceptors

Changes to the HR controlled by medulla

More impulses to SAN

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How does the heart control and coordinates the regular contraction of the atria and ventricles

SAN -> AVN -> Bundle of His

Impulses over atria

Atria contract

Non conducting tissue between atria and ventricles

Delay at AVN ensures ventricles fill before ventricles contract

Ventricles contract from apex upwards

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How can the diet of a person increase the risk of coronary heart disease

Too much cholesterol in diet

Increase in cholesterol in blood

Atheroma in artery walls

Blocks coronary arteries

Less oxygen to heart muscle

Increase in blood pressure

Increased risk of clot

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Atheroma

Cholesterol

In the artery wall

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How can a blood clot lead to myocardial infection

Trapped in coronary artery

Prevents oxygen

Reaching heart muscle

Heart muscle stops respiring

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What is the link between atheromas and the increased risk of aneurism

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Fatty material within walls of arteries

Vessels narrow

Blood pressure rises

Weakened blood vessels may burst

How can cigarette smoking and a diet high in saturated fat increase the risk of myocardial infarction

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Carbon monoxide combines with haemoglobin

Decreases concentration of antioxidants in blood

Increases the damage done to artery walls

Blood clot may occur

Blood clot causes constriction of coronary arteries

Less oxygen transported to heart muscle tissue

Explain how nervous control in a human can cause increased cardiac output during exercise

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Coordination via medulla of brain

Increased impulses along sympathetic nerve

To S.A node

Release of noadrenalin

More impulses sent from increased rate of discharge of S.A node

Increased HR

Why is increased cardiac output an advantage during exercise

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In exercise - More energy release for aerobic respiration

Higher cardiac output increases O2 supply

Increases CO2 removal

Describe the myogenic stimulation of the heart and how the regular contraction of the atria and ventricles is coordinated.

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SAN releases wave of electrical activity

So atria contract

AVN passes electrical activity after a delay

Via purkyne tissue and bundle of his

So ventricles contract at the same time from bottom upwards

Describe how stimulation of a pacinian corpuscle produces a generator potential

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There are stretch mediated sodium ion channels in the membrane

Increased pressure deforms sensory neurone membrane

Sodium ion channels open

Sodium ions diffuse in

Depolarisation

All or nothing principle

Action potential is only generated when threshold is reached High pressure generates an action potential

Spike in the graph of action potential

Refractory period

How does AV valve maintain a unidirectional flow of blood

Pressure in atrium is higher than in ventricle causing valve to open Pressure in ventricle is higher than atrium causing valve to close

Exercise causes an increase in heart rate Describe the role of receptors and of the nervous system in this process

Chemoreceptors detect rise in CO2 Send impulses to medulla More impulses to SAN By sympathetic nervous system

When the heart beats, both ventricles contract at the same time Explain how this is coordinated in the heart after initiation of the heartbeat by the SAN

Electrical activity only through AVN Waves of electrical activity passes through both ventricles at the same time

How does the interaction between circular muscle and radial muscle cause the pupil to constrict

Circular muscle contracts Radial muscle relaxes

How does the fovea enable organisms to see in detail

High visual acuity Each cone is connected to a single neurone Cones send separate sets of impulses to the brain

The retina of an owl has a high density of rod cells Explain how this enables an owl to hunt its prey at night

High sensitivity Several rods connected to a single neurone Spatial summation to reach threshold

How is a resting potential of -70mV maintained in the sensory neurone when no pressure is applied

Membrane more permeable to potassium ions and less permeable to sodium ions Sodium ions actively transported and potassium ions in

Why would the membrane potential in the sensory neurone stay at +40mV whether medium or heavy pressure was applied to the finger tip

Threshold has been reached Threshold or above causes all or nothing principle

Explain how applying pressure to the pacinian corpuscle produces the changes in membrane potential

Pressure causes lamellae to become deformed Sodium ion channels in membrane open and sodium ions move in For greater pressure more sodium ions enter

How does destroyed myelin sheaths result in slower responses to stimuli

Less saltatory conduction More depolarisation over length of membranes

Why may a nerve pathway be regarded as a simple reflex arc

Only 3 neurones in reflex arc

Advantages of simple reflexes

Rapid Protect against damage to body tissues Do not have to be learnt Help escape from predators Enable homeostatic control

Following the release of acetylcholine into a neuromuscular junction, a muscle contraction occurs Describe the sequence of events, following the release of acetylcholine that leads to stimulation of this contraction

Acetylcholine diffuses across synaptic cleft Acetylcholine attaches to receptors on post synaptic membrane Sodium ions enter leading to depolarisation Calcium ions released by endoplasmic reticulum

Inhibitory synapses cause hyperpolarisation in postsynaptic neurones Explain how this inhibits synaptic transmission

Potential difference across membrane is greater Prevents sodium ions causing depolarisation

How is resting potential maintained across the axon membrane in a neurone

Sodium ions diffuse in Membrane less permeable to sodium ions entering than potassium ions leaving Sodium ions actively transported out and potassium ions in 3Na+ out and 2K+ in

Why is the speed of transmission of impulses faster along a myelinated axon than along a non myelinated axon

Myelination provides insulation In saltatory conduction In non myelinated depolarisation occurs along whole length of axon

Sequence of events involved in transmission across a cholinergic synapse

Depolarisation of presynaptic membrane Calcium channels open and calcium ions enter Calcium ions cause synaptic vesicles to fuse with presynaptic membrane and release acetylcholine Acetylcholine diffuses across synaptic cleft Acetylcholine attaches to receptors on postsynaptic membrane Sodium ions enter leading to depolarisation

Dopamine is a neurotransmitter released in some synapses in the brain The transmission of dopamine is similar to that of acetylcholine Dopamine stimulates the production of nerve impulses in postsynaptic neurones. Describe how

Dopamine diffuses across synapse Attaches to receptors on post synaptic membrane Stimulates entry of sodium ions AND depolarisation

GABA is a neurotransmitter released in some inhibitory synapses in the brain GABA causes negatively charged chloride ions to enter postsynaptic neurones Explain how this inhibits postsynaptic neurones

Inside of post synaptic neurone becomes more negative More sodium ions required to reach threshold For depolarisation

When a nerve impulse arrives at a synapse, it causes the release of neurotransmitter from vesicles in the presynaptic knob Describe how

Depolarisation of membrane cause Ca channel proteins to open Ca enter by facilitated diffusion Causes synaptic vesicles to fuse with presynaptic membrane

Advantage of the movement of mitochondria towards the presynaptic membrane when nerve impulses arrive at the synapse

Mitochondria supply additional ATP To move vesicles

Topic 6 Flashcards

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