Autonomic Nervous System Flashcards
3 parts of brain
brain stem (pons, midbrain, medulla
cerebellum (small brain, fine motor function)
Front brain (cerebral hemisphere, diencephalon made up of thalamus and hypothalamus)
cerebral hemisphere
broken up into cerebral cortex, basal nuclei, brain stem
Basal nuclei involved in movement, coordination with brain stem
Hippocampus and amygdala involved in emotions/memory
cerebral cortex –> frontal lobe, parietal lobe, occipital lobe, temporal lobe, limbic lobe
cranial nerves
12
arise from brain stem
sensory, motor, mixed
CN2 - optic nerve sensory
CN3 - oculomotor. eye muscles, pupil response
CN4 - trochlear nerve. motor. superior oblique muscles
CN6 - Abducens. Motor. Lateral rectus muscle
Ganglions
Collection of cell bodies that receive signals and pass them on
Peripheral Nervous System
Automatic Nervous System:
involuntary, modulates functions primarily of visceral organs, preganglionic and post panglioninc nerves, preganglionic
release AcH
Somatic Nervous System:
voluntary, single motoneuron and skeletal fibre innervates it. Presynaptic neurons release AcH, activate nicotinic receptors on motor end plates
Autonomic nervous system
activated by centres:
spinal cord, brain stem, hypothalamus, portions of the cerebral cortex project to lower centres than can influence ANS
operates through visceral reflexes. sensory signals from visceral organs
subdivided:
- parasympathetic
- sympathetic
Sympathetic Division
preganglionic neurons originate in thoracolumbar spinal cord
Parasympathetic Division:
preganglionic neurons that originate in the brain stem and sacral spinal cord
Adrenergic and Cholinergic
both divisions
Adrenergic
release norepinephrine
receptors and adrenoreceptors
Cholinergic
release AcH
receptors are cholinoreceptors
Sympathetic Nervous System
mobilise the body for activity - fight, flight
Preganglionic sympathetic neurons originate in the thoracolumbar spinal cord (T1-L3):
- Leave via motor ventral motor roots - Paravertebral ganglia of the sympathetic chain - Pre-vertebral ganglia - Celiac, superior mesenteric, inferior mesenteric
Set of neurons either form a ganglia within the spinal cord or form a ganglia outside of the spinal cord
Sympathetic chain:
- Preganglionic neurons synapse on post ganglionic neurons - Occur in ganglia at the same segmental level of the chain
Or preganglionic fibres turn in the cranial or caudal direction and innervate ganglia at higher or lower levels:
- Synapses at multiple ganglia
Pre vertebral ganglia:
- Preganglionic neurons pass through sympathetic chain without synapses and synapse in pre-vertebral ganglia: celiac, superior mesenteric, inferior mesenteric
Sympathetic Nervous System:
Paravertebral sympathetic chains of ganglia
Pre-vertebral ganglia:
- Celiac - Superior mesenteric - Aortico-reginal - Inferior mesenteric - Hypogastric
Nerves extending from ganglia to different internal organs
Sympathetic nerve fibres originate in spinal cord between T1 and L2:
- Pass into the sympathetic chain - Then into tissues and organs
Preganglionic neuron
- Leave spinal nerve
- Pass through the white ramus
- Into one of the ganglia of the sympathetic chain
- Synapse with postganglionic sympathetic neurons in the ganglion
- Pass upward or downward in the chain and synapse in one of the other ganglia
- Pass variable distances through the chain and then through one of the sympathetic nerves
Synapsing with peripheral sympathetic ganglion
Postganglionic neuron
- Release norepinphrine/noradrenaline
- Inhibitory or excitatory
4 types
A1 receptor:
- Found in vascular smooth muscle of the skin; skeletal muscle and the splanchnic region, sphincters of the GIT, sphincters of the bladder, radial muscle of the iris
- Activation leads to contraction
A2 Receptors:
- Inhibitory
- Located pre-synaptically and post synaptically
- Less common than a1
- Found in the presynaptic adrenergic and cholinergic nerve terminals and in the GIT
- Found as autoreceptors and heteroreceptors
Autoreceptors:
- Present on sympathetic postganglionic nerve terminals
- Activation by norepinephrine/ noradrenaline inhibits further release of norepinephrine/ noradrenaline
Heteroreceptors:
- Present on parasympathetic postganglionic nerve terminals (GIT)
- Norepinephrine/noradrenaline causes inhibition of acetylcholine from parasympathetic post ganglionic nerve terminals
B1 Receptor:
- Prominent in the heart
- Activation increases heart rate
B2:
- Found in vascular smooth muscle, walls of the GIT and bladder, bronchioles
- Activation leads to relaxation or dilation
Neurotransmitters and Types of Receptors - Sympathetic Division:
Preganglionic neurons of the sympathetic division:
- Cholinergic
- Release Ach
- Acts on nicotine receptors of postganglionic neurons
Postganglionic neurons of the sympathetic division:
- Adrenergic in effector organs
- Cholinergic in thermoregulatory sweat glands
Effector organs are innervated by sympathetic adrenergic neurons have one of the following types of adrenoreceptors: Alpha 1, Alpha 2, Beta 1, Beta 2
