Responding to changes in environment

Question 1

describe what happens when a stimulus is detected by the pacinian corpuscle

Answer 1

1. Detects when pressure is applied
2. stretch mediated sodium ion channels deform
3. this causes an influx of sodium ions as sodium channels open
4. forms a generator potential

Question 2

structure of pacinian corpuscle

Answer 2

1. capsule
2. lamellae
3. singler nerve ending
4. myelin sheath
5. axon of sensory neurone

Question 3

rods in the human retina

Answer 3

1. detects light
2. rhodopsin breaks down or bleaches at dim light
3. rods have low visual acuity
   because many rods are attached to 1 bipolar cell

Question 4

cones in the human retina

Answer 4

1. detects different wavelengths
2. iodopsin bleach at bright light
3. cones have high visual acuity
   because one cone is attached to one bipolar cell

Question 5

describe contraction in control of heart rate

Answer 5

1. SAN located in right atrium and is connected to the medulla
2. initiates wave of depolarisation in atria to contract
3. wave is prevented to make ventricles contract therefore the wave is sent to the AVN
4. AVN passes the stimulation along bundle of His which contains purkyne tissue
5. Purkyne tissue depolarises the ventricles, causing it to contract

Question 6

describe the control of heart rate when blood pH increases

Answer 6

1. chemoreceptors are located in carotids
2. when they detect the increase in blood pH they send impulse along the sympathetic neurone to SAN
3. Nora neurotransmitter is secreted causing the SAN to increase frequency of impulses sent to the heart
4. as a result causes the heart rate to increase
5. removing the CO2 from the blood

Question 7

describe the control of heart rate when blood pressure increases

Answer 7

1. pressure receptors are located in the sinus
2. when they detect the increase in blood pressure, they send an impulse along the parasympathetic neurone to SAN
3. acetylcholine is secreted causing SAN to decrease the frequency of impulses sent to the heart
4. as a result causes the heart rate to decrease
5. allowing the pressure in blood to decrease

Question 8

explain why impulses travel faster along myelinated axons

Answer 8

1. saltatory conduction- jumps from node to node
2. depolarisation only occurs at nodes
3. impulses does not travel the whole length of the axon

Question 9

describe how an action potential is generated and how a resting potential is maintained

Answer 9

1. resting potential- -70mv. no action potential has been generated
2. depolarisation- some sodium ion channels open. when stimulus is enough all sodium ion channels open causing an influx of sodium ions. an action potential can now be generated
3. repolarisation- action potential is at +40mv. sodium ion channels close and potassium ion channels open
4. hyperpolarisation- when the inside of the axon is more negative than usual
5. refractory period- 3Na+ out and 2K+ in. returns to resting potential

Question 10

importance of refractory period

Answer 10

produces discrete impulses so that frequency of impulses can be limited

Question 11

cholinergic synapse

Answer 11

1. neurone to neurone
2. acetylcholine neurotransmitter
3. can be excitatory or inhibitory
4. triggered by AP at presynaptic membrane

Question 12

muscular junction

Answer 12

1. neurone to muscle
2. acetylcholine neurotransmitter
3. can be excitatory
4. triggered by AP at presynaptic membrane

Question 13

temporal summation vs spatial summation

Answer 13

• temporal summation- many impulses arrive within quick succession and effect added together
• spatial summation- impulses arriving simultaneously at different synaptic knobs- its effect added together

Question 14

components of sarcomere

Answer 14

A- dark, myosin and myosin+acting overlap
I- only actin
H- only myosin
Z- attachment of actin
M- attachment of myosin

Question 15

Slow muscles vs Fast muscles

Answer 15

slow muscles- more mitochondria, less fatigue, aerobic respiration, more capillaries
fast- opposite

Question 16

describe how Ca2+ and ATP are involved in the formation of actinmyosin bridge

Answer 16

1. Ca2+ enters the presynaptic knob and causes the release of Ach
2. Ach binds to receptors on muscle fibre casing it to depolarise
3. depolarisation travels down T tubules
4. Ca2+ binds to troponin, unblocking tropomyosin
5. myosin heads bind to actin filament
6. actin and myosin slide
7. attachment of ATP to myosin cause it to detach
8. hydrolysis of ATP releases energy
9. phosphocreatine regenerates ATP without respiration

Question 17

how does hormone insulin regulate blood glucose concentration

Answer 17

1. beta cells detect rise in blood glucose
2. secrete insulin into the blood
3. binds with receptors on cell surface membrane of body cells
4. insulin changes the tertiary structure of glucose transporter protein channels causing them to open and allowing more glucose to enter the cell
5. increases number of carrier molecules in the cell surface membrane

Question 18

how does hormone glucagon regulate blood glucose concentration

Answer 18

1. alpha cells detect decrease in blood glucose
2. secrete glucagon into blood
3. binds with cell surface membrane on liver cells
4. liver cells activate enzyme that converts ATP to cyclic AMP and this triggers other enzymes that converts glycogen into glucose
5. increase conversion of amino acids and glycerol into glucose

Question 19

role of adrenaline

Answer 19

1. first messenger
2. binds to specific receptors on membrane of target cells
3. activates enzyme in membrane
4. converts ATP to cyclic AMP (which is a second messenger)
5. cAMP triggers other enzymes which convert glycogen to glucose

Question 20

structure of the kidney

Answer 20

1. Fibrous capsule: outer membrane that protects the kidney.
2. Cortex: A lighter coloured outer region made up of the renal (Bowman’s) capsule, convoluted tubules and blood vessels.
3. Medulla- a darker region coloured inner region made up of loops of Henle, collecting ducts and blood vessels.
4. Venal pelvis: A funnel- shaped cavity that collects urine into the ureter
5. Ureter: A tube that carries urine to the bladder.
6. Renal artery: Supplies the kidney with blood from the heart via the aorta
7. Renal vein: Returns blood to the heart via the vena cava.

Question 21

structure of the nephron

Answer 21

1. renal capsule- inner layer of the capsule is made up of podocytes
2. proximal convoluted tubule- series of loops surrounded by blood capillaries
3. loop of henle- extends from cortex into the medulla surrounded by blood capillaries
4. distal convoluted tubule- series of loops surrounded by fewer blood capillaries
5. collecting duct- where the distal convoluted tubules empty

Question 22

describe the role of the nephron in osmoregulation

Answer 22

1. formation of glomerular filtrate by ultrafiltration
2. reabsorption of glucose and water by proximal convoluted tubule
3. maintaining a gradient of sodium ions in medulla by the top of henle
4. reabsorption of water by distal convoluted tubule and collecting duct

Question 23

role of ADH

Answer 23

1. secreted when the blood solute concentration is high
2. makes walls of collecting duct more permeable to water
3. more aquaporins in membrane
4. more water is reabsorbed from the filtrate
5. decrease in volume of concentrated urine excreted

Question 24

ultrafiltration steps

Answer 24

1. high hydrostatic blood pressure
2. caused by decreasing diameter from afferent arterioles
3. forces ions and water and other small molecules from capillaries into line of the surrounding bowman’s capsule
4. forms glomerular filtrate
5. larger molecules can not pass through so they stay in the blood

Question 25

describe what happens when there is low water potential in the blood

Answer 25

1. detected by osmoreceptors in hypothalamus 2. signals posterior pituitary gland 3. triggers ADH which enters the blood 4. causes kidney to increase reabsorption 5. less water loss in urine