end 2

Question 1

adrenal medulla

Answer 1

Each adrenal gland is composed of an inner adrenal medulla (= secretes epinephrine and
norepinephrine) and a surrounding adrenal cortex (= secretes steroid hormones)
The adrenal glands are modified sympathetic ganglion whose cell bodies do not have axons => They
release their secretions into the blood.

80 Epinephrine 20 norepinephrine

… Because adrenal medulla expresses high amounts of phenyl-N-methyltransferase (PNMT)
Converts norepinephrine to epinephrine
(sympathetic nerves do not express PNMT)

Question 2

Receptor Cholinergic receptors (ACh)

Answer 2

Two types:
1. Nicotinic Found on the postganglionic cell bodies in all autonomic ganglia - ionotropic receptor

Muscarinic –> ACh released by parasympathetic postganglionic fibres binds to muscarinic receptors on effector cell membranes (cardiac muscle, smooth muscle, glands) - metabotropic

Question 3

Adrenergic receptors

Answer 3

Catecholamine receptors (E/NE)
metabotropic:
Coupled to G
-proteins => Second messengers
- cyclic AMP (cAMP) for beta receptors - Ca2+ for alpha receptors
Beta 1 stimulation usually leads to an excitatory effect
(e.g. Heart stimulation)
Beta
2 stimulation usually leads to an inhibitory effect
(e.g. Salbutamol for asthma
: smooth muscle cells relax
causing bronchodilation without affecting heart rate)

Question 4

Autonomic agonists and antagonists

Answer 4

Binding of an agonist to a receptor => Activates the receptor similar to the neurotransmitter’s action
Binding of an antagonist to a receptor => Blocks the neurotransmitter’s response.

Question 5

somatic nervous system

Answer 5

Skeletal muscles are innervated by motor neurons
Cell bodies are located in the ventral horn of the spinal cord or brain stem (for head
muscles)
Different from the autonomic 2-neurons
pathway: continuous from origin in CNS
to muscle
Neurotransmitter = ACh
The relative balance of EPSP and IPSP determines the level of activity of the motor neuron and its
output to skeletal muscle fibres

Question 6

The neuromuscular junction

Answer 6

the link between each axon terminal of a motor neuron (recall: myelinated) and skeletal muscle
fibres
The axon terminal is enlarged = Terminal button.
Contact with a specialized portion of the skeletal muscle fibre = Motor end plate.
Neurotransmitter released = ACh.

Question 7

special

Answer 7

One EPP => One Action Potential? (YES)
IPSP behavior? (Yes on motor neuron, no on NMJ)
Difference between EPP and a regular EPSP?
(1 EPP => 1 action potential; Not true for 1 EPSP
Direction of the action potential propagation?
(Down length of muscle sarcolemma)

Question 8

toxins

Answer 8

Black widow spider venom
=> Explosive release of ACh from
vesicles at ALL cholinergic sites…
Depolarization block (depletion of vesicles
Botulinum Toxin
<= Clostridium botulinum
Blocks the release of ACh from the
terminal button.
 Botulism. (food poisoning)
 One of the most lethal toxin (less
than 0.0001 mg to cause death)