Lecture 20 - Animal Movement 1 Flashcards
Neuronal Signaling: Receptor Cell (3)
Receptor cell receives signal, receptor cell depolarizes, receptor cell releases neurotransmitters
Neuronal Signaling: Sensory Neuron (4)
Sensory neuron receives neurotransmitter from receptor cell, sensory neuron depolarizes, action potential propagated along axon of sensory neuron, sensory neuron releases neurotransmitters
Neuronal signaling: Interneuron (4)
Interneuron receives neurotransmitters, interneuron depolarizes, action potential propagated along axon of interneuron, interneuron receives neurotransmitters
Neuronal signaling: motor neuron (3)
Motor neuron receives neurotransmitters, motor neuron depolarizes, action potential propagated along axon of motor neuron causing muscles to contract
How do muscles appear when they are contracted?
Larger
Early Hypotheses for muscle contraction
Galen- 2nd Century Roman Physician: Spirits enter muscles from nerves
Rene Descartes - 17th century French philosopher: Fluids from the pineal gland of the brain inflate muscles
Jan Swammerdam - 17th century Dutch anatomist: Muscles do not change volume during contraction (true after experiment done when bubble didn’t move after muscle contraction)
Luigi Galvani - 18th century Italian scientist: discover bioelectricity, proved that electricity causes muscles to contract by stimulating the sciatic nerve to make legs move
Giovanni Aldini - 19th century Italian scientist (nephew of Galvini): reanimated the corpse of convicted murderer George Foster in 1803, caused the eyes and face and other muscles to be contorted and move etc.
Muscles
Bundles of muscle fibers
Muscle fiber
A single cell composed of several myofibrils
Myofibrils
Composed of many sacromeres
What is a sacromere?
Part of a myofibril, it is composed of two 2 light bands and a dark band
What happens to the sarcomere when the muscle contracts?
The sarcomere shortens
What happens to the sarcomere when the muscle relaxes?
The sacromere lengthens
What happens to the sarcomere when the muscle relaxes?
The sarcomere lengthens
What proteins is a sarcomere composed of?
Actin and myosin
Actin
The structural protein that the thin filament is composed of
Myosin
The motor protein that the thick filament is composed of
The sliding filament model (3)
The muscle contracts, myosin heads move toward the Z disk, the Z disks are pulled closer together
How do actin and myosin interact? (6)
Myosin heads bind to actin and catalyzes the hydrolysis of ATP, myosin head is bound to actin subunit. ATP binds to head, then myosin head detaches, after which ATP is hydrolyzed to ADP. The head then binds to the next actin subunit. The energized head is now “cocked”. Pi is released, and then the head pivots and moves the thin filament (power stroke). ADP is then released, and the cycle is ready to repeat itself.
What happens when the muscle is relaxed?
Tropomyosin and troponin block myosin binding sites on actin
What happens when muscle contraction begins? (3)
Calcium ions bind to troponin, troponin-tropomyosin complex moves, the myosin binding sites are exposed
Sarcoplasmic reticulum
Sheets of smooth endoplasmic reticulum in a muscle cell
How do neurons initiate contraction? (80
An action potential arrives at the end of the motor neuron’s axon, neurotransmitter acetylcholine is released, acetylcholine binds to acetylcholine receptors on the muscle cell, muscle cell depolarizes, action potential fires in the muscle cell, action potential propogates along the T tubule which is an invagination of the muscle cell membrane, Ca2+ channels open in the sarcoplasmic reticulum, Ca2+ causes the myosin binding sites on the actin filament to be exposed which enables contraction to begin
