Excitable cells Flashcards
What is an excitable cell?
An excitable cell is a type of cell that can be electrically excited, leading to significant membrane depolarization. This process enables signal transmission in neurons, contraction in myocytes, and secretion in certain endocrine cells.
How are different stimuli detected by the body?
Different stimuli are detected by specialized receptors, which can be classified into thermoreceptors, mechanoreceptors, and chemoreceptors. These receptors often involve specific ion channels or G-protein-coupled receptors (GPCRs), leading to a change in membrane potential and the generation of an action potential.
Describe the nature of electrical excitation in cells.
Electrical excitation in cells is not simply an on or off mechanism; it operates more like a physiological dimmer switch. There is a constant basal level of electrical activity, and ion channels play a crucial role in spreading excitation and controlling its rate.
What are channelopathies?
Channelopathies are disorders caused by mutations in ion channels, which can result in various pathologies affecting the normal function of cells.
What are the primary functions of neurons?
Neurons serve three main functions:
Sensory (afferent) neurons respond to stimuli and transmit signals to the spinal cord or brain.
Motor (efferent) neurons produce effects by sending signals from the brain and spinal cord to muscles.
Interneurons (relay neurons) connect other neurons within the nervous system.
What is nociception?
Nociception is the process by which sensory neurons respond to painful stimuli, such as extreme heat, cold, or irritating substances like spicy food.
How do motor neurons interact with skeletal muscles?
Motor neurons provide direct input to skeletal muscles at the neuromuscular junction, facilitating both voluntary (somatic nervous system) and involuntary (autonomic nervous system) muscle responses.
What distinguishes different types of muscle tissue?
Different types of muscle tissue are distinguished by their underlying architecture and the specific proteins they express. For example, striated muscle has a striped appearance due to sarcomeres, while cardiac and skeletal muscle use troponin and tropomyosin for contraction, whereas smooth muscle relies on calmodulin and myosin light chain kinase.
What is the role of the neuromuscular junction?
The neuromuscular junction is the site where the nerve and skeletal muscle meet. It facilitates the transmission of electrical signals that always lead to muscle depolarization and contraction.
How do neurotransmitters function in smooth muscle?
In smooth muscle, neurotransmitters are released into a wide synaptic cleft through structures called varicosities. This can lead to depolarization and contraction or hyperpolarization and relaxation of the muscle.
What are the cardiac nodes, and what is their significance?
Cardiac nodes are pacemaker regions in the heart where nervous input can alter the rate of pacemaker cells. Hyperpolarization slows the rate of these cells, while depolarization speeds it up.
What are gap junctions, and what role do they play in muscle tissue?
Gap junctions are specialized connections in smooth and cardiac muscle that allow electrical coupling between myocytes. They enable the spread of electrical stimuli from one cell to another, which can either depolarize or hyperpolarize the cells involved.
What types of receptors are involved in detecting mechanical stimuli?
Mechanoreceptors are specialized receptors that detect mechanical stimuli, such as pressure, vibration, and stretch.
How do chemoreceptors function in the body?
Chemoreceptors detect chemical changes in the environment, such as the presence of certain molecules in the air or blood, and are essential for taste and smell.
What happens to the membrane potential when a stimulus is detected?
When a stimulus is detected by receptors or ion channels, it causes a change in membrane potential, leading to depolarization and the generation of an action potential.
