Module 5 Angel Flashcards
describe a reflex arc
stimulus detected by receptor sensory neurone passes impulse to CNS relay neurone passes information across CNS motor neurone sends impulse to effector effector brings about a response
what is each of these in the knee-jerk and blinking reflex? stimulus receptor location of relay neurone effector importance
tap below knee cap - touch on cornea (+light/sound)
stretch receptor in muscle - touch receptor in cornea
spinal cord - lower brain stem
quadricep - muscles in eyelid
balance - protecting eyesight
list three importances of reflexes
don’t have to be learnt and therefore provide protection for babies
extremely fast as only has one or two synapses
are involuntary, so the brain is not overloaded and can focus on more important things
what are the three types of muscle?
skeletal
cardiac
involuntary
describe the organisation of muscle
A muscle is an organ made of muscle tissue, made of muscle fibres (cell). Each muscle fibre is packed with organelles called myofibrils. A myofibril is composed of two muscle filaments called actin and myosin. Myofibrils are divided into functional units, each called a sarcomere.
describe the structure of muscle fibres
They are multinucleated, and much longer than normal cells. This is because they are a result of many embryonic muscle cells fusing together, making the muscle stronger as the junction between cells would be a point of weakness. The shared cytoplasm between fibres is called a sarcoplasm. They have lots of mitochondria
describe the structure of actin and myosin
actin- thinner filament, consists of two strands twisted around each other.
myosin- thicker filament, consists of long- rod shaped fibres with bulbous heads that project to one side
what does a myofibril look like ?
alternating dark and light bands, resulting in a striped appearance
what is a light band?
lighter areas as they are the regions where actin and myosin do not overlap
what is a dark band?
darker areas because of the presence of thick myosin filaments. The edges are particular dark as myosin is overlapped with actin
what is a Z line?
The line at the centre of each light band. The distance between each Z line is a sarcomere
what is a H zone?
The lighter region at the middle of each dark band. Only myosin filaments are present at this point. When the muscle contracts, the H zone gets smaller.
what happens when muscles contracts in terms of the sarcomere?
myosin pulls actin towards the middle of the sarcomere, making the sarcomere shorter.
light band becomes narrower
H zone becomes narrower
describe the structure of myosin
have globular heads that can move forwards and backwards. There are binding sites for actin and ATP
describe the structure of actin
have binding sites for myosin heads, but these are often blocked by tropomyosin, which is held in place by troponin
how does a neuromuscular junction work?
impulses arrive at neuromuscular junction and cause vesicles to fuse with membrane and release acetylcholine which binds to receptors on the sarcolemma, causing depolarization. The depolarisation travels down the tubules, and causes the sarcoplasmic reticulum to release calcium ions. This causes contraction. Acetylcholinesterase then breaks down acetylcholine so contraction only occurs when impulses continuously arrive
describe the sliding filament model of muscle contraction
Tropomyosin prevents myosin head attaching to actin
Ca2+ released from sarcoplasmic reticulum cause tropomyosin to pull away from binding sites
Myosin head attaches to binding site on actin
Head of myosin changes angle, moving the actin filament along. ADP molecule is released
ATP fixes to myosin head, causing it to detach from the actin filament
ATP is hydrolysed to ADP, causing myosin to return to its normal position where the cycle can be repeated
What are the energy sources of muscle contraction?
Aerobic respiration/oxidative phosphorylation
Anaerobic respiration
Creatine phosphate- acts as a reserve supply of phosphates that can regenerate ATP
