Endocrine Lab Report
Earthworm Smooth Muscle
In this experiment, contractions of the earthworm gut are measured in an organ bath with a force transducer. The effect of neurotransmitters and ionic concentrations on contraction strength and rate will be investigated.
Written by staff of ADInstruments
With acknowledgement to: Dr. Stuart I. Cromarty, Department of Natural Sciences, Assumption College, Worcester, MA, USA.
[pic]
Background
Smooth muscle is one of three muscle fiber types found in animals. Unlike skeletal and cardiac muscle cells, smooth muscle cells are not striated, and have single nuclei. Smooth muscles are typically under control of the autonomic nervous system, and do not contract voluntarily. Smooth muscle contracts slowly, and does not exhibit the characteristic “twitch” seen in skeletal muscle. In addition, smooth muscle is not prone to muscle fatigue, making it an ideal component of sphincter muscles. Smooth muscle is found in the gastrointestinal tract of many animals, and is responsible for peristaltic movements. Smooth muscle is also present in the walls of arteries and arterioles, where it helps to regulate blood pressure and flow.
Smooth muscle contractions are affected by calcium and potassium ions. Calcium ion influx into the smooth muscle cell initiates a contraction. Potassium ion concentration in the extracellular medium affects the resting membrane potential of the cell, bringing it closer to or farther away from its threshold voltage. Neurotransmitters affect different types of smooth muscle differently, depending on the association of the smooth muscle with excitable cells. In general, acetylcholine increases the muscle cell’s permeability to calcium, while epinephrine decreases the cell’s permeability to calcium.
The earthworm (Lumbricus spp.) gut can be dissected and examined in vitro using an organ bath and force transducer. This preparation is robust; it can remain active for several hours. In this experiment, you
In this experiment, contractions of the earthworm gut are measured in an organ bath with a force transducer. The effect of neurotransmitters and ionic concentrations on contraction strength and rate will be investigated.
Written by staff of ADInstruments
With acknowledgement to: Dr. Stuart I. Cromarty, Department of Natural Sciences, Assumption College, Worcester, MA, USA.
[pic]
Background
Smooth muscle is one of three muscle fiber types found in animals. Unlike skeletal and cardiac muscle cells, smooth muscle cells are not striated, and have single nuclei. Smooth muscles are typically under control of the autonomic nervous system, and do not contract voluntarily. Smooth muscle contracts slowly, and does not exhibit the characteristic “twitch” seen in skeletal muscle. In addition, smooth muscle is not prone to muscle fatigue, making it an ideal component of sphincter muscles. Smooth muscle is found in the gastrointestinal tract of many animals, and is responsible for peristaltic movements. Smooth muscle is also present in the walls of arteries and arterioles, where it helps to regulate blood pressure and flow.
Smooth muscle contractions are affected by calcium and potassium ions. Calcium ion influx into the smooth muscle cell initiates a contraction. Potassium ion concentration in the extracellular medium affects the resting membrane potential of the cell, bringing it closer to or farther away from its threshold voltage. Neurotransmitters affect different types of smooth muscle differently, depending on the association of the smooth muscle with excitable cells. In general, acetylcholine increases the muscle cell’s permeability to calcium, while epinephrine decreases the cell’s permeability to calcium.
The earthworm (Lumbricus spp.) gut can be dissected and examined in vitro using an organ bath and force transducer. This preparation is robust; it can remain active for several hours. In this experiment, you