Muscles

Question 1

Function of sacroplasmic reticulum

Answer 1

Control uptake and release of calcium ions
Which control ATPase activity
And therefore the contraction of the muscle

Question 2

Neuromuscular junction

Answer 2

-Impulse arrive cause vesicles to fuse with the pre-synaptic membrane and release acetylcholine into the gap
-Acetylcholine bind to receptors on muscle fibre membrane causing depo
-Depo travels down tubules
-Leads to Ca2+ release from stores in sacroplasmic reticulum
-Ca2+ binds to proteins in the muscle leads to contraction
-Acetylcholinesterase in gap breaks down acetylcholine so that -contraction only occurs when impulses arrive continuously

Question 3

Changes at the sarcomere during contraction

Answer 3

-I band narrows
-z line moves closer
-H zone becomes narrower
-A stays the same

Question 4

Muscle contraction

Answer 4

-Ca2+ are released from the T tubules
-ADP+ Pi are associated with myosin
-Ca2+ binds to the muscles and moves tropomyosin out of the binding site
-myosin binds to the binding site forming and actin-myosin cross bridge
-actin slides past myosin power stroke
-ADP and Pi are released
-ATP binds to myosin head causing it to detach from the actin
-this is a new ATP molecule
-ATP hydrolyses causing it to move back to its original position
-recocks tropomyosin reverts back to original position and cover binding site forming
-ADP and Pi released
-phosphocreatine regenerates ATP quickly for more contractions
-Ca2+ gets reabsorbed

Question 5

Fast twitch fibres vs slow twitch fibres

Answer 5

-strength vs stamina
-rapid vs slower
-anaerobic vs aerobic
-small amounts quickly vs large amount slowly
-less mitochondria vs more

Question 6

Acetylcholinesterase

Answer 6

Hydrolyses acetylcholine the products diffuse back into the presumptive neurone. Acetylcholine is re synthesised using ATP from the mitochondria

Question 7

Inhibition

Answer 7

Post synaptic membrane has CL- channels when open Cl- diffuses in
Making the post synaptic membrane more negative
Hyper polarisation

Question 8

The all or nothing principle

Answer 8

For an action potential the generator potential must achieve exceed a threshold value
If it doesn’t exceed it no AP is produced. This is the all or nothing principle
A greater stimuli is demonstrated by things the brain interpretes such as:
- by the frequency of AP transmitted down a neurone
-different neurons with different threshold values

Question 9

Purpose of a Refractory period

Answer 9

-Ensures impulses are unidirectional
-to produce discrete impulses
-limit numbers of APs

Question 10

Refractory period

Answer 10

-After on ion channel has opened, need, a rest of about 2 ms before it can open again.
-So only the downstream channels open, causing the AP to move one-way along the axon unidirectional
-To produce discrete impulses
-A new action potential cant be formed directly behind another AP
-This ensures APs are separated from one another
-To limit the number of AP
- if Aps are seperated from one another this limits the number of action potental, that can pass along. an axon at a given time.
-This limits the strengh of the stimulus that can be detected.