ANS Flashcards
What two nerves does the ANS have?
PREganglionic: CNS –> autonomic ganglion
POSTganglionic: autonomic ganglion –> target tissue
What does the ANS regulate?
1) Contraction and regulation of smooth muscle
2) Heartbeat
3) Exocrine and endocrine secretions
4) Energy metabolism
What do somatic motor neurons do?
Carry information to skeletal muscle
What do autonomic motor neurons do?
Control smooth/cardiac muscle, glands and adipose tissue
What are the two branches of the ANS?
Sympathetic - flight or flight, adrenaline release
Parasympathetic - rest and digest
What are the three characteristics of control?
1) Antagonistic control: opposing effects of para/sympathetic divisions
2) Tonic control: the level of response based on input - it’s not all or nothing
3) Variable control: different receptor populations - how many
Outline the sympathetic branch
-Comes from the middle/lower sections of the spinal cord
-Short preganglia fibres which remain close to spinal cord
-Neurotransmitter is noradrenaline
Pathways: thoracic and luber regions of the spinal cord
Outline the parasympathetic branch
-Comes from the top of the body, hind brain/vagus nerve
-Long pre and post ganglia fibres which are near target organs
-Neurotransmitter is ACh
Pathways: brain stem and sacral region of the spinal cord
Outline the acetylcholine
ACh is a neurotransmitter made in the mitochondria from choline and acetyl COA, released via excytosis.
In the synaptic cleft ACh is broken down by the enzyme acetylocholinesterase, chloine is recycled back to the axon terminal and used to make more ACh
What are varicosites?
Swellings where neurotransmitters are released
How are neurotransmitters made?
1) Precursors get into the nerve through uptake mechanisms
2) Enzymes convert them into NTs and process waste
3) NT must be packaged into vesicles
4) AP makes Ca2+ channels open so Ca2+ can enter
5) Vesicles fuse to cell surface so NTs diffuse across the terminal
6) NTs bind to receptors on target cells and activate
7) NTs are then inactivated outside the cell by blood or inside a nerve/glial cell
How are catecholamines made?
1) Tyrosine has an OH group added by tylosine hydroxylase to make DOPA
2) DOPA has a COOH group removed by DOPA decarboxylase to make dopamine
3) Dopamine has an OH group added by dopamine B-Hydroxlase to make noradrenaline
4) Noradrenaline has a methyl group added which forms adrenaline
List drugs that are used to regulate the ANS
High blood pressure - blocks beta receptors
Asthma - inhalers = beta 2
Glaucoma - fluid drained from eye
Antidepressants - noradrenaline
