CAT prep 2022 Flashcards
Explain their mode of action of curariform drugs are administered.
- curariform drugs are muscle relaxants.
2. the compete for the receptor at the post-synaptic membrane with acetylcholine.
At the end of surgery, drugs are administered to put an end to the effect of curariform drugs. Explain their mode of action.
- Anticholinesterase drugs block the enzymatic hydrolysis of acetylcholine by inactivating acetylcholinesterase.
- They are used as decurarizing drugs to put an end to the action of curariform drugs after completion of surgery. More acetylcholine molecules are available and replace curariform drugs on receptor sites, restoring skeletal muscular motility, and hence respiration.
- Neostigmine and physostigmine combine with acetylcholinesterase to inactivate it for up to several hours, after which they are displaced from the acetylcholinesterase so that it once again becomes active. Only such “reversible” anticholinesterase drugs are used in medicine
All cerebral lobes play a role in either oral or written language
a
effect of diameter on duration and speed of conduction of impulse in the action potential
An axon with a larger diameter offers less resistance to the movement of ions down the axon, causing ions to move faster down the axon and causing the action potential to be conducted faster.
effect of intensity on action potential
intensity increase frequency
effect of frequency on action potential
- frequency increases perception
- frequency increase intensity
- frequency increases the number of action potential like tetanus effect in the muscle.
most abundant excitatory neurotransmitter in the brain.
Glutamate
most abundant inhibitory neurotransmitter in brain.
GABA
what is the most abundant inhibitory neurotransmitter in spinal cord
Glycine
Explain the physiological mechanism of referred pain.
- Referred pain is attributed to converging synapses on the same postsynaptic neurons, in the spinal cord, by visceral nerve fibers and skin nerve fibers.
- A stimulus originating from a viscus is felt as coming from the skin because the topography of the skin is better known (consciously understood) to the individual than viscera topography.
-The pain is referred to as a dermatome on the body surface, specifically at a segment that has the exact embryonic origin as the damaged viscera, because they share some innervations
pathways.
Discuss this term: “hypothalamus is the higher vegetative center or vegetative brain”
It controls and integrates the activities of the autonomic nervous system that regulates the
functioning of viscera (contraction of smooth muscles and cardiac muscle, secretion of
numerous glands).
• the hypothalamus acts as the principal regulator of visceral activities, such as heart rate
and peristalsis,…
• It is associated with rage and aggression reactions.
• It regulates the body temperature.
• It controls food intake by two centers. The hunger center is responsible for the hunger
sensation. When a sufficient quantity of food has been ingested, the satiety center is
stimulated and sends nerve impulses that inhibit the hunger center.
• It contains the thirst center. When certain cells of the hypothalamus are stimulated by the
increase of the osmotic pressure of the extracellular fluid, they produce the sensation of
thirst, if the thirst is quenched, osmotic pressure comes back to normal.
• The hypothalamus is a part of the centers responsible for maintaining the states of awakeness
and sleep.
• It is the controller of the endocrine gland secretion.
The principal functions fulfilled by the hypothalamus
It controls and integrates the activities of the autonomic nervous system that regulates the functioning of viscera (contraction of smooth muscles and cardiac muscle, secretion of numerous glands). As the higher vegetative center (vegetative brain), the hypothalamus acts as the principal regulator of visceral activities, such as heart rate, and peristalsis…
2. It is associated with rage and aggression reactions.
3. It regulates the body temperature.
4. It controls food intake by two centers. The hunger center is responsible for the hunger sensation. When a sufficient quantity of food has been ingested, the satiety center is stimulated and sends nerve impulses that inhibit the hunger center.
5. It contains the thirst center. When certain cells of the hypothalamus are stimulated by the increase of the osmotic pressure of the extracellular fluid, they produce the sensation of thirst. If the thirst is quenched, osmotic pressure comes back to normal.
The hypothalamus is part of the centers responsible for maintaining the states of awakeness and sleep
Explain Presynaptic Inhibition and Facilitation.
Another type of inhibition occurring in the CNS is presynaptic inhibition, a process mediated by neurons that end on excitatory endings, forming axo-axonal synapses. Three mechanisms of presynaptic inhibition have been described. First, activation of the presynaptic receptors increases Cl- conductance, and this has been shown to decrease the size of the action potentials reaching the excitatory ending. This in turn reduces Ca2+ entry and consequently the amount of excitatory transmitter released. Voltage-gated K+ channels are also opened, and the resulting K+ efflux also decreases the Ca2+ influx. Finally, there is evidence for direct inhibition of transmitter release independent of Ca2+ influx into the excitatory ending.
The first transmitter to be shown to produce presynaptic inhibition was GABA, increasing Cl- conductance and K+ conductance.
Presynaptic inhibition occurs in many of the sensory pathways in the nervous system. That is, adjacent terminal nerve fibers mutually inhibit one another, which minimizes the sideways spread of signals in sensory tracts.
Conversely, presynaptic facilitation is produced when the action of the action potential is prolonged and the Ca2+ channels are open for a longer period.
The splanchnic nerves
The splanchnic nerves are paired with visceral nerves (nerves that contribute to the innervation of the internal organs ), carrying fibers of the autonomic nervous system ( visceral efferent fibers) as well as sensory fibers from the organs ( visceral afferent fibers ).
Types of autonomic ganglia
- Lateral (parvertebral) ganglia: The lateral ganglia lie on each side of the vertebral column forming two chains known as sympathetic chains (the lateral ganglia are the sites of the relay of sympathetic fibers).
- Collateral (prevertebral) ganglia: Collateral ganglia lie between the sympathetic chain & the organ of supply. They are the site of the relay of the preganglionic sympathetic fibers that supply the abdominal and pelvic viscera.
- Terminal (peripheral) ganglia: They are present near (or on the surface) of the innervated organs. They are the sites of relay of the parasympathetic fibers.
