Nervous coordination

Question 1

stimulus and process in action potential

Answer 1

a change in an organism’s internal or external environment
in action potential: stimulus excites neurone cell membrane, causing sodium ion channels to open. Membrane becomes more permeable to sodium, so sodium ions diffuse into neurone down sodium ion electrochemical gradient –> inside of neurone becomes less negative

Question 2

depolarisation and process in action potential

Answer 2

decrease in potential difference across a cell membrane, making it less negative than resting potential
in action potential: if potential differences reaches the threshold (-55mV), more sodium ion channels open + more sodium ions diffuse into neurone

Question 3

repolarisation and process in action potential

Answer 3

return of a cell membrane to its resting potential
in action potential: at +30mV, sodium ion channels close and potassium ion channels open. Membrane is more permeable to potassium so potassium ions diffuse out of neurone down potassium ion concentration gradient –> starts to get membrane back to resting potential

Question 4

hyperpolarisation and process in action potential

Answer 4

an increase in potential difference across a cell membrane, making it more negative that the resting potential
in action potential: potassium ion channels are slow to close so there’s a slight ‘overshoot’ (too many K+ ions diffuse out) –> potential difference becomes more negative than resting potential

Question 5

resting potential and process in action potential

Answer 5

potential difference across cell membrane when cell is at rest
in action potential: ion channels are at rest, sodium-potassium pump returns membrane to resting potential by pumping NA+ ions out and K+ ions in, maintains resting potential until membrane is excited by another stimulus

Question 6

cholinergic synapse

Answer 6

synapse that uses the neurotransmitter acetylcholine

Question 7

acetylcholine (ACh)

Answer 7

Neurotransmitter that binds to cholinergic receptors.

At neuromuscular junctions: always excitatory, binds to nicotinic cholinergic receptors, broken down in the synaptic cleft by acetylcholinesterase (AChE)

Question 8

actin and it’s role in muscle contraction

Answer 8

Thin myofilament protein in muscle fibres (light, I-bands). Has actin-myosin binding site. Tropomyosin between actin filaments.
The energy released from ATP causes the myosin head to bend, which pulls the actin filament along in a rowing action.

Question 9

actin-myosin cross bridge

Answer 9

Bond formed when a myosin head binds to an actin filament.

Form and break very rapidly, pulling the actin filament along, shortens the sarcomere, causing the muscle to contract.

Question 10

ATP-phosphocreatine (PCr) system

Answer 10

ADP + PCr ➞ ATP + creatine
generates ATP very quickly by phosphorylating ADP using a phosphate group from phosphocreatine

PCr is stored inside cells but runs out quickly so used during short busts of vigorous exercise

anaerobic + alactic