University:
Kentucky State University
Course:
BIO 303 | Human Physiology
Academic year:

2019
Views:

170

Pages:

32
Author:

penuchelnu2

Some Important Transmitters 42 (1) Acetylcholine (ACh) as NT 43 Acetylcholine Synthesis choline acetyltransferase choline + acetyl CoA ACh + CoA 44 Acetylcholinesterase (AChE) • Enzyme that inactivates ACh. – Present on postsynaptic membrane or immediately outside the membrane. • Prevents continued stimulation. 45 46 The Life Cycle of Ach 47 Ach - Distribution • Peripheral N.S. • Excites somatic skeletal muscle (neuro-muscular junction) • Autonomic NS Ganglia Parasympathetic NS--- Neuroeffector junction Few sympathetic NS – Neuroeffector junction • Central N.S. - widespread Hippocampus Hypothalamus ~ 48 Ach Receptors •ACh is both an excitatory and inhibitory NT, depending on organ involved. –Causes the opening of chemical gated ion channels. •Nicotinic ACh receptors: –Found in autonomic ganglia (N1) and skeletal muscle fibers (N2). •Muscarinic ACh receptors: –Found in the plasma membrane of smooth and cardiac muscle cells, and in cells of particular glands . 49 Acetylcholine Neurotransmission • “Nicotinic” subtype Receptor: – Membrane Channel for Na+ and K+ – Opens on ligand binding – Depolarization of target (neuron, muscle) – Stimulated by Nicotine, etc. – Blocked by Curare, etc. – Motor endplate (somatic) (N2), – all autonomic ganglia, hormone producing cells of adrenal medulla (N1) 50 Acetylcholine Neurotransmission • “Muscarinic” subtype Receptor: M1 – Use of signal transduction system • Phospholipase C, IP3, DAG, cytosolic Ca++ – Effect on target: cell specific (heart , smooth muscle intestine ) – Blocked by Atropine, etc. – All parasympathetic target organs – Some sympathetic targets (endocrine sweat glands, skeletal muscle blood vessels - dilation) 51 Acetylcholine Neurotransmission • “Muscarinic” subtype: M2 – Use of signal transduction system • via G-proteins, opens K+ channels, decrease in cAMP levels – Effect on target: cell specific – CNS – Stimulated by ? – Blocked by Atropine, etc. 52 Cholinergic Agonists • Direct – Muscarine – Nicotine • Indirect – AChE Inhibitors ~ 53 Cholinergic Antagonists • Direct Nicotinic - Curare Muscarinic - Atropine 54 Ligand-Operated ACh Channels N Receptor 55 56 57 Neurotransmitter “Second Messenger” System 58 G Protein-Operated ACh Channel M receptor 59 (2) Monoamines as NT 60 Monoamines • Catecholamines – Dopamine - DA Norepinephrine - NE Epinephrine - E • Indolamines Serotonin - 5-HT 61 Synthesis of Monoamine NT tyrosine hydroxylase Tyrosine L-Dopa dopa decarboxylase Dopaminergic Neurons Dopamine dopamine b hydroxylase Adrenergic Norepinephrine Neurons phenylethanolamineN-methyltransferase Epinephrine Adrenal Glands Mechanism of Action (b receptor) 63 Norepinephrine (NE) as NT • NT in both PNS and CNS. • PNS: – Smooth muscles, cardiac muscle and glands. • Increase in blood pressure, constriction of arteries. • CNS: – General behavior. 64 65 Adrenergic Neurotransmission • a1 Receptor – Stimulated by NE, E, – blood vessels of skin, mucosa, abdominal viscera, kidneys, salivary glands – vasoconstriction, sphincter constriction, pupil dilation 66 Adrenergic Neurotransmission • a2 Receptor – stimulated by, NE, E, ….. – Membrane of adrenergic axon terminals (presynaptic receptors), platelets – inhibition of NE release (autoreceptor), – promotes blood clotting, pancreas decreased insulin secretion 67 Adrenergic Neurotransmission • b1 receptor – stimulated by E, …. – Mainly heart muscle cells, – increased heart rate and strength 68 Adrenergic Neurotransmission • b 2 receptor – stimulated by E .. – Lungs, most other sympathetic organs, blood vessels serving the heart (coronary vessels), – dilation of bronchioles & blood vessels (coronary vessels), relaxation of smooth muscle in GI tract and pregnant uterus 69 Adrenergic Neurotransmission • b 3 receptor – stimulated by E, …. – Adipose tissue, – stimulation of lipolysis 70 (3) Amino Acids as NT • Glutamate acid and aspartate acid: – Excitatory Amino Acid (EAA) • Gamma-amino-butyric acid (GABA) and glycine: – Inhibitory AA 71 (4) Polypeptides as NT • CCK: (cholecystokinin) – Promote satiety following meals. • Substance P: – Major NT in sensations of pain. 72 (5) Monoxide Gas: NO and CO • Nitric Oxide (NO) – Exerts its effects by stimulation of cGMP. – Involved in memory and learning. – Smooth muscle relaxation. • Carbon monoxide (CO): – Stimulate production of cGMP within neurons. – Promotes odor adaptation in olfactory neurons. – May be involved in neuroendocrine regulation in hypothalamus. 73

Some Important Transmitters

Related Documents

Recommended Documents

Description

Related Documents

Free up your schedule!

Take 5 seconds to unlock