Module 3: Lecture 8 Flashcards
what is the adrenal gland composed of?
two areas
- inner adrenal medulla
- a surrounding adrenal cortex
what does the inner adrenal medulla secrete?
epinephrine and norepinephrine
what does the surrounding adrenal cortex secrete?
steroid hormones
the adrenal glands are modified sympathetic ganglion whose cell bodies _________________________ –> ______________________.
do not have axons –> they release their secretions into the blood
instead of the adrenal gland having a post-ganglionic neuron, what does it have/do instead?
from the pre-ganglionic neuron it goes straight into the adrenal gland like acts like the postganglionic neuron
is the adrenal gland an adrenergic fibre?
yes, but it also secretes epinephrine
how much of the adrenal medullas secretion is epinephrine and norepinephrine?
- 80% epinephrine
- 20% norepinephrine
why does the adrenal medulla only secrete 20% norepinephrine?
because it contains high amounts of phenyl-N-methyltransferase (PNMT)
what does phenyl-N-methyltransferase (PNMT) do?
converts norepinephrine into epinephrine
which one has a more wide ranging effects within the body, epinephrine or norepinephrine?
epinephrine
- this is why the adrenal gland should release more of it because it can act more generally rather than locally
are acetylcholine, epinephrine and norepinephrine neurotransmitters?
yes
its not only the neurotransmitter that determines how the tissue is going to respond, its also depends on the?
receptor that, that neurotransmitter is binding to
what are the two types of cholinergic receptors(Ach)?
- nicotinic (ionotropic receptor) - ligand gated ion channel
- muscarinic (metabotropic receptor) - act through a secondary messenger
where is the nicotinic receptor found?
on the postganglionic cell bodies on all autonomic ganglia (because acetylcholine is released at that synapse between the pre and post ganglionic neurons)
what happens when acetylcholine binds to a nicotinic receptor?
its just an ionotropic receptor
- just an ion channel that opens to allow sodium ions into the cell creating the excitatory postsynaptic potential (EPSP)
- depolarizing event
what is responsible for generating an action potential in the postganglionic neuron?
the nicotinic receptor
what are the receptors on your end effector organs?
the muscarinic cholinergic receptors
which system utilizes acetylcholine?
parasympathetic in the post ganglion neurons
depending on the receptor subtype that the tissue is expressing, it will change how ______________________.
that neurotransmitter effects it
- can have either an excitatory effect or an inhibitory effect
stimulation of Beta1 usually leads to?
an excitatory effect (eg. heart stimulation)
stimulation of Beta2 usually leads to?
an inhibitory effect (eg. salbutamol for asthma: smooth muscle cells relax causing bronchodilation without affecting heart rate)
what are G-proteins?
second messengers for metabotropic receptors
- (i could be wrong about this)
what G-protein is for beta receptors?
cyclic AMP (cAMP)
what G-protein is for alpha receptors?
calcium ions
what are cetacholamine receptors?
A catecholamine receptor is a type of G protein-coupled receptor that binds to and responds to neurotransmitters that include, norepinephrine, and epinephrine.
what happens when there is a binding of an agonist to a receptor?
activates the receptor similar to the neurotransmitter’s actions
- essentially binds to that receptor and acting like the neurotransmitter - it activates that receptor
what happens when there is a binding of an antagonist to a receptor?
- blocks the neurotransmitters response
where are your nicotinic receptors?
the connection point between the pre and post ganglionic neurons of the parasympathetic and sympathetic systems
what is the system that we have voluntary and conscious control over?
the somatic nervous system
what is the system that innervates our skeletal muscles?
the somatic nervous system
does the somatic nervous system utilize two neurons?
no, only one that travels from the central nervous system towards the actual skeletal muscle fiber itself
what is the only way you can control your skeletal muscle?
through the motor axon
the cell bodies of the motor neurons are located?
in the ventral horn of the spinal cord or brain stem for the head muscles
what is the neurotransmitter that is released at the output of the motor neuron?
acetylcholine (ACh)
why are motor neurons considered the “final common pathway”?
any time your muscle is activated, it is because your motor neuron was activated
- all the output from your CNS towards your muscle fibers has to come through that motor neuron
can the cell body of the motor neuron receive BOTH inhibitory and excitatory input?
yes
what determines the level of activity of the motor neuron and its output to skeletal muscle fibres?
the relative balance of EPSP and IPSP
is there involuntary input to the somatic nervous system?
yes
- like breathing because if we think about it, we are controlling it. but if we do not think about it, we still do it
what is the neuromuscular junction?
the link between each axon terminal of a motor neuron and skeletal muscle fibres
- link of nerve to muscle
when the axon becomes enlarged in the neuromuscular junction, what is it called?
terminal button
- its just the axon terminal - bulbous swelling at the end of the axon terminal that holds all of your synaptic vesicles with that neurotransmitter
when the neuromuscular junction comes in contact with a specialized portion of the skeletal muscle fibre what is it called?
the motor end plate
what neurotransmitter is released from the neuromuscular junction?
acetylcholine
what is on the motor end plate?
a whole bunch of ion channels that acetylcholine will bind to
when sodium enters the muscle fiber, a graded potential/EPSP is generated. however, because it is in the muscle, what is it called?
end plate potential (EPP)
what is the type of receptors that Ach is going to bind to on the motor end plate?
a nicotinic receptor
- a cholinergic receptor that is an ion channel that opens in response to acetylcholine binding to it
where on the muscle fiber does the motor neuron innervate it at the neuromuscular junction?
the motor neuron tends to innervate it in about the middle of the muscle fiber
because the motor neuron innervates the muscle fiber in the middle of the fiber, what happens when it generates the action potential?
the axon potential will spread in both directions along the fiber, away from the neuromuscular junction
one end plate potential, will always generated an?
action potential in the muscle fiber itself
- unlike a synapse which needs many inputs on the postsynaptic neuron to generate an action potential
if a motor neuron generates an action potential, it will generate _______________________________________________________.
an action potential in the skeletal muscle fiber
is the action potential of a neuromuscular junction always excitatory?
yes
- input zone can receive inhibitory or excitatory, BUT the output zone, when it actually fires the action potential, will always be excitatory at the level of the muscle fiber
what does the venom from a black widow spider result in?
all of your synaptic vesicles to suddenly being released at once
what does botilium toxin do?
its botox
- blocks the release of ACh from the terminal button
what does curare do?
block ACh receptors on the motor end plate (antagonist)
- respiratory paralysis = inability to contract muscles
what does sarin do?
- inhibits the acetylcholinesterase (degrades the acetylcholine to reset to synaptic cleft)
- this blocks/prevents further depolarization of the cell from subsequent action potentials
