Human responses

Question 1

what makes up the central nervous system?

Answer 1

brain and spinal cord with neurone transmitting to and from the CNS

Question 2

what are the voluntary and involuntary nervous systems called?

Answer 2

voluntary - somatic nervous system
involuntary - autonomic nervous system

Question 3

what is the somatic nervous system?

Answer 3

voluntary functions
ie: skeletal muscle contracting when turning book page
impulse reached when acetylcholine released

Question 4

what is the autonomic nervous system?

Answer 4

involuntary functions
ie: heart rate , happens all the time
triggers muscles for digestion
secretion of adrenaline

Question 5

what is the autonomic nervous system broken down into?

Answer 5

sympathetic nervous system
parasympathetic nervous system

Question 6

function and role of sympathetic nervous system?

Answer 6

target organ increases in function
flight or fight response
heart rate increased and breathing rate increased to inc blood supply to the muscles

Question 7

what is the parasympathetic nervous system?

Answer 7

‘rest and digest’
relaxed and asleep
breathing and heart ate decreased
digestion system increases in activity

Question 8

what is the difference between parasympathetic and sympathetic nervous system with the neurotransmitters?

Answer 8

acetylcholine in sympathetic
noradrenaline in parasympathetic

Question 9

describe what makes up a muscle fibre?

Answer 9

sarcolemma - plasma membrane containing folds called t-tubules

sarcoplasm - cytoplasm - has multiple nuclei, contains modified ER called sarcoplasmic reticulum

mitochondria needed for ATP for muscle contractions

myofibrils - part of muscle fibre where contraction takes place

Question 10

what proteins make up myofibrils?

Answer 10

actin and myosin , arranged to form filaments

Question 11

when actin and myosin slide over each other what is this? what is happening?

Answer 11

muscle contraction

Question 12

What is the H band?

Answer 12

only thick myosin filaments

Question 13

What is the I band?

Answer 13

only actin thin filaments

Question 14

what is the A band?

Answer 14

when actin and myosin filaments overlap

Question 15

what is the M line?

Answer 15

attachment of myosin filament

Question 16

what is the Z line?

Answer 16

attachment of actin filaments

Question 17

what is the sarcomere in the myofibril?

Answer 17

section of the myofibril between two z lines

Question 18

what structure of the muscle fibre actually moves and contracts?

Answer 18

sarcomere

Question 19

What is the function of the sarcoplasmic reticulum in skeletal muscle?

Answer 19

stores and releases calcium ions when muscle stimulated
ions needed for binding myosin and actin during muscle contraction

Question 20

What is the role of T-tubules in muscle cells?

Answer 20

carry action potential ensuring whole muscle contracts simultaneously by triggering the release of calcium ions

Question 21

How does the structure of a muscle fibre adapt it for its function?

Answer 21

1. muscle fibres long
2. multinucleated
3. many mitochondria for ATP

Question 22

What is the name of the line that marks the boundary of each sarcomere?

Answer 22

Z line

Question 23

what does striated mean?

Answer 23

muscle has visible bands light and dark under the microscope

Question 24

What happens to the H zone when a muscle contracts?

Answer 24

shortens and disappers

Question 25

What type of neurone stimulates a striated (skeletal) muscle to contract?

Answer 25

motor neurone

Question 26

What is a neuromuscular junction?

Answer 26

synapse between muscle and muscle fibre

Question 27

What triggers calcium ions to enter the motor neurone at the neuromuscular junction?

Answer 27

arrival of action potential at presynaptic membrane

Question 28

What does the influx of calcium ions into the motor neurone cause?

Answer 28

acetylcholine to fuse with presynaptic membrane

Question 29

What happens after acetylcholine is released into the synaptic cleft?

Answer 29

It diffuses across the neuromuscular junction and binds to receptors on the sarcolemma.

Question 30

What does acetylcholine binding to the sarcolemma receptors cause?

Answer 30

Sodium ion channels open, allowing Na⁺ to enter the muscle cell.

Question 31

What effect does the influx of sodium ions have on the muscle cell?

Answer 31

It depolarises the sarcolemma and generates an action potential in the muscle fibre.

Question 32

Where does the action potential travel after the sarcolemma?

Answer 32

Along the T-tubules towards the centre of the muscle fibre.

Question 33

What does the action potential cause in the sarcoplasmic reticulum?

Answer 33

It opens voltage-gated calcium ion channels, releasing Ca²⁺ into the sarcoplasm.

Question 34

What happens when calcium ions are released into the sarcoplasm?

Answer 34

They bind to troponin on the actin filaments.

Question 35

What effect does calcium binding to troponin have?

Answer 35

causes troponin and tropomyosin to move, exposing myosin-binding sites on actin.

Question 36

Why are multiple neuromuscular junctions present on a muscle?

Answer 36

to ensure rapid and coordinated contraction across the whole muscle.

Question 37

What needs to be exposed on the actin filament for myosin to bind?

Answer 37

The myosin-binding sites.

Question 38

What normally blocks the myosin-binding sites on actin?

Answer 38

Tropomyosin, held in place by troponin.

Question 39

What causes tropomyosin to move away from the binding sites?

Answer 39

Calcium ions (Ca²⁺) binding to troponin.

Question 40

What happens when myosin binds to actin in sliding filament theory?

Answer 40

A cross-bridge is formed between the myosin head and the actin filament.

Question 41

What causes the myosin head to detach from the actin filament?

Answer 41

The binding of a new ATP molecule to the myosin head.

Question 42

How is the myosin head reset?

Answer 42

ATP is hydrolysed into ADP and Pi, providing energy to move the myosin head back to its original position.

Question 43

Why does the sarcomere shorten during contraction?

Answer 43

Because the actin filaments slide over the myosin filaments, pulling the Z-lines closer together.

Question 44

Do the filaments themselves change length during contraction?

Answer 44

No, actin and myosin filaments do not shorten—they just slide past each other.

Question 45

What are the three main ways ATP is regenerated in muscle cells?

Answer 45

1. Creatine phosphate system 2. Anaerobic respiration 3. Aerobic respiration

Question 46

What is creatine phosphate (CP)?

Answer 46

A high-energy molecule stored in muscle cells that donates a phosphate to ADP to make ATP quickly.

Question 47

What enzyme catalyses the transfer of a phosphate from creatine phosphate to ADP?

Answer 47

Creatine phosphotransferase (also called creatine kinase).

Question 48

Is oxygen required for the creatine phosphate system?

Answer 48

no - anaerobic process

Question 49

What is a disadvantage of the creatine phosphate system?

Answer 49

It only lasts a short time and creatine phosphate stores are limited.

Question 50

Where does anaerobic respiration occur in muscle cell?

Answer 50

in cytoplasm of muscle cell - sarcoplasm

Question 51

Which process is fastest at producing ATP?

Answer 51

Creatine phosphate system