Neurons, brain, cell membrane, NT

Question 1

3 classes of neurons

Answer 1

1) Afferent convey info from tissues and organs toward CNS
2) Efferent convey info away from CNS to effector cells
3) Interneurons connect neurons w/in CNS

Question 2

astrocyte function

Answer 2

• Regulate compositn xtracellular fluid in CNS via removal of K+ and neurotransmitters around synapses
• Stimulate fxn of tight junctions between cells that make up walls of capillaries in the CNS
  o Blood brain barrier
• Sustain neurons metabolically
  o Provide glucose, remove ammonia
• In embryos, astrocytes guide CNS neurons as they migrate to their ultimate destination and stimulate neuronal growth via secretion of growth factors
• Have ion channels – can generate weak electrical responses

Question 3

ACh

Answer 3

• Synthesized from choline and acetyl coA in the cytosol of pre-synaptic terminals and stored in synaptic vesicles. Neurons that release ACh are cholinergic neurons.
• RECEPTORS: Nicotinic receptors (ion channel) and muscarinic receptors (metabotropic and couple with G proteins)
• INACTIVATION: Enzyme acetylcholinesterase (located in pre and postsynaptic membranes destroying ACh releasing choline and acetate)
• PHARMACOLOGY: Atropine is a naturally occurring antagonist of muscarinic receptors (eg. Eyedrops) that relax the smooth muscle of the iris, thereby dilating the pupils for eye exam.

Question 4

Biogenic Amines

Answer 4

Catecholamines: dopamine, norepinephrine, epinephrine

• Dopamine is precursor of epinephrine and norepinephrine.
• Synthesis begins with uptake of tyrosine by the axon terminals and its conversion to another precursor L-dopa (by rate limiting enzyme tyrosine hydroxylase). Then, depending on the enzyme expressed in a given neuron, any one of the three catecholamines may be released. Phenylethanolamine N-methyltransferase (PNMT) is the enzyme that converts norepinephrine to epinephrine.
• INACTIVATION: Enzymes monoamine oxidase (MAO) & Catechol-O-methyltransferase (COMT)
• PHARMACOLOGY: drugs known as monoamine oxidase (MAO) inhibitors increase the amount of norepinephrine and dopamine in a synapse by slowing their metabolic degradation, used in treatment of depression.

Question 5

What do beta-blockers do (ie: which receptor do they bond to)?

Answer 5

Beta blockers lower blood pressure by binding to beta-adrenergic receptors, preventing epi and NE from binding since they raise BP

Question 6

what do stimulated alpha-1 receptors do to visceral organs?

Answer 6

widen pupil, constrict arterioles to coronary / skin / skeletal / abdominal viscera / kidney / salivary gland, contract urinary bladder sphincter

Question 7

what do stimulated beta-1 receptors do to visceral organs?

Answer 7

increase HR, contractility, conduction

Question 8

what do stimulated beta-2 receptors do to visceral organs?

Answer 8

relax bronchiole muscle and bladder wall

Question 9

what is the effector enzyme for IP3 / DAG?

Answer 9

phospholipase C

Question 10

what does Botulinum do?

Answer 10

blocks SNARE protein, preventing release of neurotransmitter and causing flaccid paralysis

Question 11

what does atropine do?

Answer 11

It is a muscarinic antagonist; it blocks the muscarinic receptor on the postsynaptic membrane and results in decreased secretions

Question 12

where electron potentials are generated

Answer 12

axon hillock

Question 13

lidocaine action

Answer 13

blocks Na+ voltage-gated channels, preventing action potential

Question 14

tetrodoxin

Answer 14

created by pufferfish

similar to lidocaine in that it blocks voltage-gated Na+ channels to prevent action potential

Question 15

how are NT removed from synaptic cleft?

Answer 15

reuptake, diffusion, enzyme degrades, degraded by nearby glial

Question 16

what kind of junction mediates electrical transmission

Answer 16

gap junctions

Question 17

which part of the ANS is dominant in moment-to-moment modulation of HR and why?

Answer 17

parasympathetic. M2 cause direct stim of K+ channels to open, causing hyperpol whereast B1 stimulate through a G-coupled 2nd messenger system of cAMP activation (this takes longer)

Question 18

older men can have hyperactive internal bladder sphincters. What kind of med is given for this?

Answer 18

alpha-1 blocker to normalize tone of internal bladder sphincter

Question 19

what neuropeptide is lacking in narcolepsy?

Answer 19

orexin

Question 20

organs of limbic system

Answer 20

amygdala, thalamus, hypothalamus, basal nuclei, prefrontal cortex, hippocampus, olfactory bulbs