Nervous Systems Anna Garcia Adv. Biology Prof. Llavina 10th grade
Nervous Systems Stretch receptors in skeletal muscles stimulate sensory neurons. Describe how these neurons could participate in an activity such as walking or riding a bicycle, in which opposing muscles alternately contract and relax.
Nervous Systems Sensory nerve cells send information to the brain from every part of the body. Sensory receptors are specialized structures made up of sensory nerve cells and support cells through which the nervous system gathers and interprets stimuli. Sensory neurons are sensory nerve cells and they transmit impulses from the sensory receptors to the central nervous system. Stretch receptors are sensory receptors in a muscle that respond to the stretching of tissue.
Nervous Systems Sensory receptors are made up for sensory nerve cells. Sensory neurons are a type of sensory nerve cells that transmit impulses from the sensory receptors to the central nervous system. Sensory neurons convert external stimuli to internal electrical impulses.
Nervous Systems Sensory neurons activate motor neurons. Motor neurons can be found in the central nervous system which projects the axons. The axons are structures that carry impulses away from the cell body. When axons are projected outside of the central nervous system, they directly or indirectly control muscles.
Nervous Systems • A muscle contractions begins at the central nervous system. This happens because of the brain or the spinal cord. • Motor neurons in the spinal cord activate. • In a ventral root of the spinal cord, action potential passes outward. • Axons branch to supply motor fibers. • Action potential is conveyed to the motor fibers. • Action potential cases acetylcholine to be released to the muscle fiber.
Nervous Systems • This causes electrical resting potential to change. • Then, action potential moves is the two directions across the muscle fiber’s surface. • Action potential enters the muscle fiber through the traverse tubules on its surface. • Where these tubules meet the sarcoplasmic reticulum, Ca++ ions are released. • These Calcium ions cause troponin and tropomyosin to move which enables myosin molecule heads to twirl along thin filaments. • This is the force that drives a muscle contraction.
Nervous Systems • After the muscle contracts and the action potential has passed, calcium gates close. Calcium pumps in the sarcoplasmic reticulum retrieve calcium from the cytoplasm. • As the calcium pumps back, calcium ions come off the troponin. • Troponin returns to its normal state. • Troponin permits tropomyosin to cover acting myosin binding sites on acting filament. • The fact that there are no biding sites available, does not allow cross bridges to form and so the muscle relaxes.
Nervous Systems Sensory neurons participate in activities such as walking or riding a bike because both activities require muscle contractions and relaxations. Without sensory neurons, impulses would not be transmitted from cell receptors and motor neurons will not be activated. If these actions do not occur, muscles do not contract or relax and you’re not able to ride a bike or walk.
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