Nervous coordination and muscle contraction Flashcards
What is the difference between the nervous system and the hormonal system?
The nervous response is rapid but doesn’t last long and is restricted to one region of the body.
How is resting potential maintained?
- Sodium potassium pump actively transports 3 sodium ions out of the axon and 2 potassium ions into the axon.
- Also, sodium channels are closed whilst potassium channels are open
What happens in an action potential?
Stimuli causes sodium ion channels to open so sodium diffuses in, making the inside more positive. This is depolarisation.
What happens in repolarisation?
Sodium ion channels close, potassium ion channels open so potassium ions move out of the axon causing the inner membrane to become negative again.
Too many potassium ions diffuse out causing hyperpolarisation
What is the advantage of a myelinated neurone?
Impulses travel faster because depolarisation does not need to happen across the whole membrane only at nodes of Ranvier. This is known as saltatory conduction.
Apart from myelinated sheaths how else can speed of transmission be increased?
Temperature and increased diameter
Why does increasing the diameter of the neurone speed up transmission?
Less leakage makes the potential hard to maintain
What is the all or nothing principle?
Below the threshold value means no action potential. Above the threshold causes an action potential but the strength of the action potential is always the same
What is the refractory period and why is it important?
Once an action potential is created there is a period after where inward movement of sodium ions is prevented which ensures the action potentials are unidirectional, discrete and limited number.
What is the gap between neurones called?
Synaptic cleft
What are the three proteins that make up the muscle fibre?
Actin, myosin and tropomyosin
Describe actin
A thin globular protein consisting of two strands twisted around one another
Describe myosin
Thicker, made up of long rod shaped tails and a bulbous head
What is the difference between slow and fast twitch muscles?
Slow contract slower and weaker as they are built for endurance
Adaptations of slow twitch muscles
Large store of myoglobin
Rich supply of blood vessels
Lots of mitochondria
Adaptations of fast twitch muscles
Large store of glycogen
More myosin filaments
High concentration of enzymes for anaerobic respiration
Store of phosphocreatine
What does phosphocreatine do?
Rapidly generates ATP in anaerobic conditions
What is the purpose of tropomyosin?
Stop myosin heads binding to actin by covering the bonding site until calcium ions released from the sarcoplasmic reticulum causes the tropomyosin to change shape.
What happens to the A band, I band, H zone and Z line in contraction?
A band- No change
I band- Shortens
H zone- shortens
Z lines- closer together
What is the role of calcium ions and ATP in muscle contraction?
Calcium ions cause tropomyosin to move and stimulates ATPase.
ATP causes myosin head to detach and return to normal position.
ATP actively transports calcium ions back to sarcoplasmic reticulum when muscle relaxes
What are the three types of muscle?
Skeletal
Cardiac
Smooth
What is an antagonistic pair?
A pair of muscles that work together to move a bone.
What is the sarcolemma?
The plasma membrane in muscle fibre
What is the sarcoplasm?
Cytoplasm in a muscle fibre
What filaments does the H zone include?
Thick myosin filaments only
What filaments does the I band contain?
Thin actin filaments only
What is the Z line?
End of the sarcomere
What is the sarcomere?
Section of the myofibril in between adjacent Z lines
What is the M-line?
Middle of the sarcomere
What does the A zone include?
Thick myosin filaments overlapping thin actin filaments
What type of transport is used by the sodium potassium pump?
Active transport
What ion channels are open during depolarisation?
Voltage gated sodium ion channels
How does an agonistic drug work?
Same shape as neurotransmitter, so mimic their action
How does an antagonistic drug work?
Block the receptors on the postsynaptic membrane so the neurotransmitter cannot bind
