How do skeletal muscles contract.pptx

How do skeletal muscles contract? Anatomy & Physiology Answer: Electricity Skeletal muscles can only contract when stimulated by an electrical impulse sent from the central nervous system. Closer look… Motor neurons are specialised cells which transmit nerve impulses rapidly to a group of muscle f...

How do skeletal muscles contract? Anatomy & Physiology Answer: Electricity Skeletal muscles can only contract when stimulated by an electrical impulse sent from the central nervous system. Closer look… Motor neurons are specialised cells which transmit nerve impulses rapidly to a group of muscle fibres. How contractions occur (1) 2. Nerve impulse travels down the AXON to the… 3. MOTOR END PLATE 1. Nerve impulse is initiated in the CELL BODY in the BRAIN or the SPINAL CHORD. The neuromuscular junction 4. NEUROTRANSMITTER called ACETYLCHOLINE (Ach) is secreted into the SYNAPTIC CLEFT. Electricity CAN’T transmit across to the fibres without Ach (due to the gap). Action potential 5. If enough Ach is secreted, and the there is enough electrical charge, a muscle ACTION POTENTIAL is created. The electrical impulse will now travel across the cleft and to the muscle fibres. Action potential creates a wave of contraction down the muscle fibre. All or none law If the action potential DOES NOT meet the threshold charge NONE of the muscle fibres will contract. If the action potential DOES meet the threshold charge ALL of the muscle fibres will contract.