Chemical transmission in the autonomic nervous system (ANS) and its effects on smooth muscle Flashcards
(14 cards)
What is the autonomic nervous system (ANS)?
The ANS controls internal bodily functions automatically, including the heart, blood vessels, airways, gastrointestinal system, and smooth muscles of the viscera (internal organs).
What type of muscle is primarily controlled by the autonomic nervous system?
Smooth muscle, which is found in the walls of hollow organs like the gastrointestinal tract.
What is the difference between skeletal muscle and smooth muscle in terms of control?
Skeletal muscle is controlled by the somatic nervous system and is voluntary, while smooth muscle is controlled by the autonomic nervous system and operates involuntarily.
What is the function of acetylcholine (ACh) in the autonomic nervous system?
Acetylcholine is a neurotransmitter that can stimulate smooth muscle contraction, particularly in the parasympathetic nervous system.
What is the function of adrenaline (epinephrine) in the autonomic nervous system?
Adrenaline is a neurotransmitter in the sympathetic nervous system, often causing smooth muscle relaxation and increased heart rate.
What equipment is used to measure the contraction of smooth muscle in this experiment?
A tension transducer connected to a Biopac recording system is used to measure contraction force and other physiological responses.
What are the three main variables measured in the experiment with rabbit gut smooth muscle?
The three variables are:
Maximum contraction force (amplitude)
Resting tension (the baseline length between contractions)
Frequency of contractions (number per minute)
Why is Tyrode’s solution used in the experiment?
Tyrode’s solution mimics extracellular fluid and helps maintain the viability of the isolated smooth muscle tissue during the experiment.
How do you measure the contraction force in the Biopac system
You use the I-beam tool to select the region of the trace representing the contraction and resting tension, and the system will display the peak (max) and trough (min) values.
How are different drugs used and what are some examples of these different drug types?
Drug: chemical substance with biological effects (except nutrients)
Drug uses: psychotropic (‘mind-altering’), medicines, poisons, research tools (these overlap)
What is the difference between a ligand, an agonist, and an antagonist?
Ligand: chemical which binds to a receptor
- endogenous (e.g. hormone, neurotransmitter) or exogenous (e.g. applied drug)
Agonist: ligand which can activate a receptor
Antagonist: ligand which blocks effect of agonist but without an effect of its own
What are the differences between drug specificity, selectivity, and potency?
Specificity: receptors activated specifically by one endogenous agonist
Selectivity: ligand binds to more than one receptor type (similarities in structure of ligands
mediate selectivity for same receptor types)
In practice, exogenous ligands act specifically at low doses and selectively at high doses
Drug side effects often due to lower selectivity (act at several receptor types) at higher doses
Potency: amount of agonist needed to induce response, expressed as dose or concentration
- a higher potency agonist requires a lower dose to induce an effect
- potency determined by characteristics of receptor activation
What is the time scale of effects with activation of the different types of receptors?
Ligand-gated ion channels: very fast (msec) activation by certain neurotransmitters
G protein-coupled receptors: fast (msec-sec) activation by certain neurotransmitters
Kinase-linked receptors: slow (sec-hours) activation by proteins (e.g. insulin)
Nuclear receptors: very slow (hours-days) activation by certain hormones and vitamins
Which two receptor classes are activated by hormones such as insulin and steroids?
Insulin: kinase-linked receptors
Steroids: mainly nuclear receptors (some gonadal steroids can also act on GPCRs)
