Response - topic 7

Question 1

What is an antagonistic muscle pair

Answer 1

one muscle contracts and the other relaxes

Question 2

what is the structure of a skeletal muscle

Answer 2

• made up of muscle fibres
• cell surface membrane = sarcolemma
• cytoplasm = sarcoplasm
• endoplasmic reticulum = sarcoplasmic reticulum

Question 3

what is the sarcolemma

Answer 3

cell membrane of a muscle fibre

folds to create deep tube like projections called t tubules

Question 4

what does the sarcoplasm contain

Answer 4

mitochondria and myofibrils

Question 5

what is the importance of lots of mitochondria in the sarcoplasm

Answer 5

carries out aerobic respiration to generate ATP for contraction

Question 6

Importance of myofibrils in the sarcoplasm

Answer 6

made up of a bundle of actin and myosin filaments which slide past each other in contraction

Question 7

Structure of myosin

Answer 7

thick filament
fibrous proteins with globular heads positioned away from the m line

Question 8

structure of actin

Answer 8

thin filament made up of actin molecules
2 actin chains twist round to form one thin filament
tropomyosin is twisted around the two actin chains
troponin is also attached to the actin chain

Question 9

microscopic structure of a skeletal muscle

Answer 9

• sarcomere
• m line
• z line
• H band
• A band
• I band

Question 10

what is a sarcomere

Answer 10

section of myofibril between two z lines

Question 11

what is a z line

Answer 11

attachment for actin filaments
end of a sarcomere

Question 12

what is a m line

Answer 12

attachment for myosin filaments

Question 13

what is an H band

Answer 13

section of muscle only containing myosin

Question 14

what is an A band

Answer 14

section of muscle containing myosin and actin
where both filaments overlap

Question 15

what is an I band

Answer 15

section of muscle only containing actin

Question 16

breakdown of a muscle fibre

Answer 16

cell unit –> sarcoplasm –> myofibril –> sarcomere –> myosin and actin

Question 17

what is tropomyosin

Answer 17

protein attached/twisted around two actin chains
prevents myosin heads binding to actin at rest

Question 18

process of muscle contraction

Answer 18

• Ca2+ diffuses out of the sarcoplasmic reticulum and into the myofibrils
• Ca2+ binds to a protein attached to tropomyosin
• this causes tropomyosin to change position on the actin and expose the myosin binding sites
• myosin heads bind to actin and form a cross-bridge between the two filaments
• Ca2+ stimulates ATP hydrolase
• ATP is hydrolysed to ADP + Pi on the myosin head which causes the myosin head to bend
• this pulls actin towards the centre of the sarcomere
• ATP binds to myosin head which causes it to change shape and release from the actin and return to its original position
• Myosin head is able to bind to new binding site
• process repeats until muscle is fully contracted

Question 19

what is a cross bridge formation

Answer 19

myosin head binds to actin binding site

Question 20

how is a cross bridge formed

Answer 20

-Ca2+ binds to a protein which causes tropomyosin to change position and expose the myosin binding sites
- Myosin heads bind to actin filament forming a cross-bridge

Question 21

What is the importance/role of ATP in the process of muscle contraction

Answer 21

ATP is required for the myosin head to detach from actin filament and return to original position

ATP is required for myosin heads to bend which allows actin to slide via hydrolysis

ATP required for the return of Ca2+ to the sarcoplasmic reticulum via active transport

Question 22

what is the role of phosphocreatine

Answer 22

molecule stored by muscles which can be used for rapid production of ATP when aerobic respiration is insufficient

Question 23

equation of the generation of ATP from phosphocreatine

Answer 23

ADP + phosphocreatine —> ATP + creatine

Question 24

characteristics of slow twitch muscles

Answer 24

lots of capillaries
lots of mitochondria
high concentration of myoglobin
slow contraction
fatigue less quickly
relies on aerobic respiration
red in colour

Question 25

characteristics of fast twitch muscles

Answer 25

fewer capillaries fewer mitochondria less conc of myoglobin fast contraction fatigue quickly relies on anaerobic respiration pale in colour

Question 26

example of a fast twitch muscle

Answer 26

eyelids

Question 27

example of a slow twitch muscle

Answer 27

back

Question 28

describe an inhibitory synapse

Answer 28

-prevent an action potential being generated - Cl- diffuse in K+ moves out hyperpolarisation occurs more Na+ is required to meet threshold and generate an action potential

Question 29

what is visual acuity

Answer 29

resolution - ability to distinguish between two points

Question 30

Why do cones have high visual acuity

Answer 30

- one cone cell is joined to a singular bipolar cell - sends separate impulses to the brain - brain is able to distinguish between the impulses

Question 31

why do rods have low visual acuity

Answer 31

- multiple rods joined to a singular bipolar cell - sends general impulses to the brain - brain cannot distinguish between impulses

Question 32

process of synaptic transmission across a cholinergic synapse

Answer 32

- action potential arrives at pre synaptic neurone and depolarises it - this causes Ca2+ voltage gated channels to open causing Ca2+ to move into the neurone via facilitated diffusion - causes vesicles containing Asch move and fuse with membrane - Asch diffuses across synapse and binds to receptors on membrane - Na+ channels open and Na+ moves in depolarising the neurone - if threshold is reached action potential is genarated - Asch is broken down or reabsorbed

Question 33

describe the process of water reabsorption in the collecting duct

Answer 33

- water potential of the medulla is lower than the water potential of the filtrate in the collecting duct - collecting duct runs parrallel to ascending loop ( counter- current principle ) - water moves out of the collecting duct via osmosis

Question 34

-nature of refractory period

Answer 34

period of time between impulses where the neurone is unable to be stimulated or generate another action potential as the K+ and Na+ channels are closed

Question 35

importance of the refractory period

Answer 35

ensures the action potentials are discrete events means the impulse can only travel in one direction

Question 36

stimulation of myogenic heartbeat

Answer 36

SAN depolarises and generates an action potential which causes the atria to contract impulses passes through non-conductive to the AVN which creates a delay in the impulse to allows the atria to finish contracting impulse is passed through the bundle to his to the purkyne fibres which causes the ventricles to contract from the bottom up

Question 37

propagation along a non-myelinated neurone

Answer 37

- very slow depolarisation occurs along whole length of axon each section of axon is alternatively depolarised and repolarised

Question 38

propagation along a myelinated neurone

Answer 38

- very fast allows saltatory conduction to occur impulse effectively jumps between the node of Ranvier's within the Schwann cells

Question 39

generation of an action potential from the Paccinian corpuscle

Answer 39

-pressure stimuli causes the membrane to stretch and become distorted - this causes stretch mediated Na+ channels to open - Na+ diffuses into the Pacinian Corpuscle via facilitated diffusion and causes depolarisation which establishes a generator potential - if enough generator potentials are produced an action potential is generated

Question 40

Structure of Pacinian Corpuscle

Answer 40

- layers of membrane separated by vicous gel containing Na+ ions - section of axon exposed to the PC contains stretch mediated Na+ channels

Question 41

Process when glucose concentration is too low

Answer 41

- alpha cells in islets of langerhan in the pancreas detect low glucose concentration and releases glucagon - glucagon binds to specific receptors on liver and muscle cells - activates enzymes for gluconeogenesis and glycogenolysis - secreted until blood glucose levels return to normal

Question 42

process of osmoregulation via ADH

Answer 42

- osmoreceptors in the hypothalamus detects low water potential in the blood and sends an impulse to the posterior pituitary gland which releases ADH - ADH binds to specific receptor proteins on the collecting duct - This stimulates vesicles containing aquaporfins to fuse with the membrane - This increases permeability of the duct so more water is absorbed via osmosis

Question 43

process when glucose concentration is too high

Answer 43

- beta cells in the islets of langerhan in the pancreas detect an increase in glucose and release insulin - insulin binds to receptor proteins on liver and muscle cells and increases permeability of the cells to glucose by increasing rate of facilitated diffusion - also activates enzymes which stimulate glycogenesis

Question 44

secondary messenger model

Answer 44

- glucagon or adrenaline binds to specific receptor proteins on the liver cell - this activates enzyme adenylate cyclase - this enzymes converts ATP to cyclic AMP - cyclic AMP activates protein kinase A - This stimulates a cascade of glycogenolysis reactions which increase levels of glucose in the blood

Question 45

glycogenesis

Answer 45

conversion of glucose to glycogen activated by insulin decreases glucose concentration

Question 46

glycogenolysis

Answer 46

hydrolysis of glycogen to glucose activated by glucagon increases glucose concentration

Question 47

gluconeogenesis

Answer 47

conversion of amino acids and other organic substances to glucose activated by glucagon increases glucose concentration

Question 48

what are the factors affecting speed of conduction

Answer 48

temperature, myelination and axon diameter

Question 49

how does temperature affect speed of conduction

Answer 49

increasing temperature increases the kinetic energy available for facilitated diffusion of Na+ and K+ so rate of depolarisation increases

Question 50

how does myelination affect speed of conduction

Answer 50

myeline sheath insulates the electrical impulse by allowing salatory condition to occur - impulse jumps between the nodes of ranvier

Question 51

how does axon diameter affect speed of conduction

Answer 51

increased axon diameter means that axon membrane increased surface area - increases rate of diffusion of Na+ and K+ which increases the rate of depolarisation