Muslce Tissue

Question 1

How do muscles contract?

Answer 1

• Muscle fibre receives signal from neuron connected to it by the neuromuscular junction
• Muscles contract when thick and thin filaments slide past each other
• Thick filament: myosin (anchored to centre of the sacromere (M-line))
• Thin filament: actin (anchored to Z-line)
• Myosin filament pulls actin filament along its length
• Cross bridges of the myosin attach to actin and exert force on them to move
• ATP bound to myosin hydrolises into ADP and Pi
• Causing myosin head to extend and attach to binding site
• Power stroke triggered, allowing myosin to pull the actin filament toward the M-line, shortening the sacromere
• ADP and Pi released
• Myosin remains attached to actin until a new ATP bind to it
• Muscle contraction controlled be Ca2+
• When muscle relaxed, tropomyosin blocks the binding site
• When Ca2+s big enough, and ATP present, Ca bind to troponin, which displaces tropomyosin, exposing the binding site
• Ca ions stored in sarcoplasmic reticulum and released in response to signals from the nevrous system to contract
• Neurotrans

Question 2

How are impulses transmitted from sensory neuron to effector cell?

Answer 2

• Depolarisation occurs
• Deplorising electrical potential travels down to the dendrites over the cell body
• Collection of electrical potential at the axon hillock (summation)
• Action potential occurs down the dendrite
• At the axon terminal, electrical impulses pass on to another cell at the synapse
• Space bet Pre synaptic neuron and post synaptic cell called synaptic cleft
• Neurotransmitters packaged in vessicles
• They are released by exocytosis from neuron to synaptic cleft
• Neurotransmitters bind to cell at receptor site attached to ion channels
• Channels open, allowing the movement of ions into and out of the effector cell