Lecture 4

Question 1

the hypothalamus plays a dominant role

Answer 1

-initiates fight-or-flight response
-regulatory centers for body temperature, food intake, and water balance

Question 2

medulla oblongata

Answer 2

-contains centers involved in the regulation of breathing, heart rate, and BP

Question 3

autonomic reflex arcs

Answer 3

-regulated by opposing action of sympathetic and parasympathetic branches
-cardiovascular control center influences activity of ANS
-cause adjustments in heart rate, stroke volume and vasoconstriction
-blood pressure returns to normal

Question 4

criteria to be classified as a neurotransmitter

Answer 4

-synthesized in neurons
-released at the presynaptic membrane following depolarization
-bind to a postsynaptic receptor and cause a detectable effect

Question 5

5 classes of neurotransmitters

Answer 5

1. amino acids
2. biogenic
3. neuropeptides
4. acetylcholine
5. ‘other’

Question 6

nicotinic AChR

Answer 6

-NMJ, ganglionic synapse
-ligand-gated, ionotropic, rapid
-effects are always excitatory (graded EPSP)

Question 7

muscarinic AChR

Answer 7

-postganglionic parasympathetic synapse
-metabolic, slow
-diverse effects (excitatory or inhibitory)

Question 8

metabotropic receptor

Answer 8

-ligand (ACh) bind receptor and conformational change activates G-protein - G-protein coupled receptor
-G-protein: heterotrimer activated by GTP binding to ⍺-subunit, ⍺-subunit and βˠ-complex interact to activate ion channels
-leads to opening of ion channels and other intracellular events - signaling cascade

Question 9

adrenergic receptors (ARs)

Answer 9

-sympathetic synapses at effector tissue
-respond to norepinephrine (NE) or epinephrine (E) released from sympathetic postganglionic neuron

Question 10

different receptor types and subtypes of adrenergic receptors

Answer 10

-tissue specific distribution
-⍺ adrenoreceptors
-β adrenoreceptors

Question 11

⍺1 adrenergic receptors

Answer 11

-sensitivity NE>E
-⍺1 ARs: NE binds –> phosphorylates VG Ca2+ channels via PLC and PKC –> opens inactivation gate
-is involved in contraction of smooth muscles (except intestinal)

Question 12

⍺2 adrenergic receptors

Answer 12

-sensitivity NE>E
-⍺2 ARs: NE binds –> dephosphorylates VG Ca2+ channels via inactivation of AC, cAMP lowers, inactivation of PKA (inactivation gate closed)
-located on membrane of adrenergic axon terminals –> inhibit release of NE

Question 13

β adrenergic receptors

Answer 13

-β ARs: NE binds –> activates VG Ca2+ channels via AC, cAMP goes up
-β1 ARs (NE=E): primarily in heart (increase heart rate and strength of contraction)
-β2 ARs (E>NE): prevalent in bronchioles of lungs (bronchodilator (smooth muscles relax))

Question 14

agonist

Answer 14

a subsatance that binds to a receptor and initiates a signalling event (may include both the natural endogenous ligand as well as pharmaceutical agents that mimic the natural substance)

Question 15

antagonist

Answer 15

a substance that binds to a receptor but does not stimulate a signaling event. Interfere with the binding of the natural ligand

Question 16

evolution of the autonomic NS

Answer 16

-divisions of ANS often not as well defined in ‘lower’ vertebrates
-greater reliance on circulating catecholamines (NE, E made by adrenal medulla, not a neuron)

Question 17

exception in SNS - adrenal medulla

Answer 17

-preganglionic neuron synapses onto chromaffin cells (modified postganglionic neurons) of the adrenal medulla (highly modified sympathetic ganglion)
-chromaffin cells (neurosecretory cells) secrete epinephrine and norepinephrine into circulation –> widespread effect