6) Oragnisims Respond To Changes In Their Enviroment Flashcards
1
Q
Principle of Pacinian Corpuscle
A
- (Pressure causes) membrane/lamellae to become deformed/stretched;
- Stretch-mediated sodium ion channels in membrane open and sodium ions move in;
- Greater pressure more channels open/sodium ions enter;
2
Q
Generator potential leading to
action potential
A
- Threshold has been reached;
- (Threshold or above) causes maximal response / all or nothing principle;
3
Q
Retinal Convergence of Rods
and Cones
A
Cones
- cones are connected to a single neurone
- separate sets of impulses to brain/ retinal convergence
Rods
- several rods connected to a single neurone
- single set of impulses to brain.
4
Q
Describe the process of heart
rate control
A
- myogenic / does not require nerve impulse;
- SAN sends wave of electrical activity / impulse;
- over atria;
- rate of beating slowed by parasympathetic;
- rate of beating increased by sympathetic;
- delay through AVN;
- wave of electrical activity passes down bundle of His / through Purkyne tissue;
- allows blood to empty into ventricles / atria to empty;
- before ventricles contract;
5
Q
Heart rate and CO2
levels/blood pressure
A
- Chemoreceptors detect rise in CO2/fall in pH OR baroreceptors detect rise in blood pressure;
- Send impulses to cardiac centre/medulla;
- More impulses to SAN;
- By sympathetic (nervous);
6
Q
The establishment of an action
potential
A
{Depolarization}
- sodium channels open/ membrane more permeable to sodium ions
- sodium ion enter
- by diffusion from high to low concentration
{Reporalisation}
- sodium channels close
- potassium channels open, membrane becomes more permeable to potassium ions
- potassium ions leave
- by diffusion from high to low concentration
7
Q
The establishment of a resting
potential
A
- Large anions inside axon;
- Membrane more permeable to K+ than Na+;
- K+ diffuse out faster than Na+ diffuse in;
- Sodium/potassium pump;
- Na+ pumped out faster than K+ pumped in / 3 for 2
- (So) inside negative compared to outside;
8
Q
Positive feedback due to Na+
channel proteins opening
A
- Ion) channel proteins open, sodium in;
- Depolarisation / reaches threshold;
- More channels open / positive feedback;
9
Q
Why do myelinated nerve
fibres transmit action potentials
faster?
A
- (In myelinated) action potential/depolarisation only at node(s);
- (In myelinated) action potential jumps from node to node/saltatory;
- (In myelinated) action potential does not travel along whole length;
10
Q
Describe transmission across a synapse
A
- impulses causes ca2+ to enter axon.
- vesicles move to/ fuse with presynaptic membrane
- acetylcholine is released
- acetylcholine diffuses across synaptic cleft
- ACH binds with receptors on postsynaptic membrane
- Na+ enter postsynaptic membrane
- if above threshold action potential produced
11
Q
Inhibitory
neurotransmitter - GABA
A
- inside becomes more negatively charged / hyperpolarised;
- stimulation does not reach threshold level / action potential not produced;
- depolarisation does not occur
12
Q
Why is synaptic
transmission unidirectional?
A
- Neurotransmitter only made in/stored in/released from pre-synaptic neurone;
- (Neuro)receptors only on the post-synaptic membrane;
13
Q
Describe muscle contraction
A
- Calcium ions diffuse into myofibrils from sarcoplasmic reticulum
- Calcium ions cause movement of tropomyosin on actin
- This movement causes exposure of the binding sites on the actin
- Myosin heads attach to binding sites on actin
- Hydrolysis of ATP on myosin heads causes myosin heads to bend
- Bending pulls actin molecules
- Attachment of a new ATP molecule to each myosin heads causes causes myosin heads to detach from actin sites
14
Q
Role of ATP in muscle contraction
A
- Attachment / cross bridges between actin and myosin;
- Movement of myosin heads / pulling of actin;
- Detachment of myosin heads;
- Myosin heads move back / to original position;
15
Q
The effect of low pH on muscle contraction
A
- Low pH changes shape of calcium ion receptors;
- Fewer calcium ions bind to tropomyosin;
- Fewer tropomyosin molecules move away;
- Fewer binding sites on actin revealed;
- Fewer actin-myosin bridges can form OR Fewer myosin heads can bind;
16
Q
Number of phosphocreatine in
fast muscle fibres
A
- Phosphocreatine provides phosphate/phosphorylates;
- To make ATP;
- Fast muscle fibres used for rapid/brief/powerful/strong contractions;
- Phosphocreatine used up rapidly during contraction/to make ATP;
- Anaerobic respiration involved;
- ATP used to reform phosphocreatine;
- Lots of phosphocreatine in fast fibres
17
Q
Increase in blood sugar level
A
- leads to more insulin secreted
- binds to specific receptors on liver/muscle cells
- leads to more glucose entering cells/ carrier activity/ increased permeability to glucose
- glucose leaves the blood
- glucose entering cells converted to glycogen
18
Q
Second messenger cAMP
A
- Adenylate cyclase activated / cAMP produced / second messenger produced;
- Activates enzyme(s) (in cell);
- (So) glycogenolysis/ gluconeogenesis occurs / glycogenesis inhibited;
19
Q
Glucagon binding to receptor
on liver – shapes fitting
A
- Glucagon has specific shape / structure;
- receptor molecules (protein) with specific receptor sites /binding sites;
- concept of fitting;
- glucagon receptors only on liver cells;
20
Q
Formation of glomerular filtrate in Bowmans
Capsule - kidneys
A
- Blood pressure / hydrostatic pressure;
- Small molecules / named example;
- Pass through basement membrane / basement membrane acts as filter;
- Protein too large to go through / large so stays behind;
- Presence of pores in capillaries / presence of podocytes;
21
Q
Which molecules/cells remain in the
blood and why?
A
- Red blood cells/platelets/protein/polypeptide;
- Too large to leave glomerulus/to pass through basement membrane
22
Q
Reabsorption of glucose in the proximal
convoluted tubule - kidneys
A
- Reabsorbed into cells lining the proximal convoluted tubule;
- By co-transport with sodium ions;
- Passes (from cells lining the proximal convoluted tubule) into the blood (capillaries) by facilitated diffusion
23
Q
Counter current multiplier in Loop of Henle
A
- In the ascending limb, sodium ions actively removed;
- Ascending limb impermeable to water;
- In descending limb, sodium ions diffuse in;
- Low/more negative water potential in the medulla OR high concentration of ions in the medulla;
- (So) water leaves collecting duct/leaves distal convoluted tubule;
- By osmosis/down water potential gradient;
24
Q
Compare ion concentration is ascending and
descending limb
A
- concentration rises in descending limb because sodium ions enter and water is lost.
- concentration falls in ascending limb because sodium Iona’s and chloride ions are actively removed, water remains in ascending limb because walls are impermeable to water.
25
Collecting duct
1. Concentration rises in collecting duct because it loses water by osmosis;
2. ADH increases permeability (of walls of collecting duct) to water;
26
Osmoreceptor and ADH
1. Low water potential of blood detected by receptors in the hypothalamus;
2. (Receptors stimulate) posterior pituitary secretes/releases (more) ADH;
3. ADH increases the permeability of collecting ducts/ Acts on collecting duct / distal convoluted tubule / second convoluted tubule;
4. Makes cells more permeable / inserts aquaporins in plasma membranes;
5. So more water leaves the nephron by osmosis/moves down the water potential gradient into the blood capillaries;
6. Urine becomes more concentrated;
27
Why is glucose found in urine of diabetics?
1. High concentration of glucose in blood;
2. High concentration in tubule / in filtrate;
3. Reabsorbed by facilitated diffusion / active transport;
4. Requires proteins / carriers;
5. These are working at maximum rate / are saturated;
6. Not all glucose is reabsorbed / some is lost in urine
28
Why do desert animals and whales have extra-
long loop of Henle? - kidneys
1. Loops of Henle produce high chloride ion/sodium ion concentration in medulla of kidney that results in water reabsorption from collecting ducts.
2. The longer loops of Henle in the whale, result in a higher concentration of chloride ions/sodium ions (in the medulla).
3. So the greater water potential gradient results in more water being reabsorbed by the whale’s nephrons (so urine more concentrated)
4. (So) can conserve more water
