Autonomic nervous system Flashcards
What is the efferent system?
Peripheral nerves that carry impulses from the CNS , which can be divided into somatic and autonomic nerves
Autonomic nerve divisions
parasympathetic and sympathetic
Autonomic nerve functions
involuntary control of body functions
Sympathetic nervous system primary function
Stimulate body’s fight or flight or freeze response.
Structure of neurons and origins
SHORTER Pre-ganglionic- thoracolumbar division of the spinal cord, mainly T1 to L2/L3. militated
post-ganglionic - LONGER extends throughout the body. Unmyelinated
Structure of sympathetic ganglia
paravertebral chain ganglia that interconnect the neurones. Sympathetic ganglion cells typically in discrete ganglia with long post ganglionic fibres
What is the preganglionic neurotransmitter in sympathetic nerves?
acetylcholine- nicotinic
Sympathetic post ganglionic neurotransmitter
adrenaline
What is the sympathetic outflow?
From thoracic and lumbar nerve divisions to all viscera and cardiac and smooth muscle and glands
Viscera definition
all internal organs in the main cavities of the body
Sympathetic nervous system association with adrenaline?
Preganglionic fibres synapse with the adrenal medulla, releasing acetylcholine which activates it to release adrenaline.
Other roles of the sympathetic nervous system
vasoconstriction of blood vessels towards digestive tract, skin and kidneys- due to the activation of alpha-1 adrenergic receptors by norepinephrine released by post ganglionic neurones.
Parasympathetic nervous system primary function
stimulate the body’s ‘rest and digest’ or ‘feed and breed’ activities
Structure of parasympathetic neurons and origins
origin- 4 cranial nerves and
pelvic splanchnic nerve- S2-4
preganglionic neuron- long
postganglionic neuron short
Why are the neurones these lengths?
The preganglionic neurons don’t synapse in the paravertebral ganglionic chain, instead synapse in intramural ganglia within the organs they innervate.
Thus the pre is very long and post is short.
Structure of ganglia
synapse in intramural ganglia within the organs they innervate.
Four paired parasympathetic ganglia of the head and neck, including the otic and ciliary ganglia.
Two neurotransmitters in parasympathetic nerves
Pre ganglionic nerve fibre- ACh nicotinic
Post ganglionic nerve fibre- ACh muscarinic
4 different cranial nerves and function
Oculomotor nerve III- innervates the eye, controlling 4/6th of the ciliary
Facial nerve VII - innervates the ganglia supplying the tear and salivary glands- pterogopalatine ganglion
Glossopharyngeal nerve IX- supplies otic ganglion regulating the parotid salivary gland
vagus nerve X- supplies heart and lungs and alimentary system
Vagus nerve ganglion location
C1
pelvic splanchnic nerve function
Innervate pelvic viscera and urogenital tract
Different sympathetic ganglia and the nerves that synapse
paravertebral midline ganglia- the heart, lungs
coeliac ganglia- great and small splanchnic - foregut
superior mesenteric ganglia- large intestine, adrenal gland, pancreas, liver and ducts - midgut
inferior mesenteric ganglia- kidney, bladder and sexual organs- pelvic organs
What is Horner’s syndrome?
Caused by a lesion in the superior cervical ganglion which causes loss of sympathetic action, thus cause permanent constriction of pupil, drooping eyelid and a dry and flushed face.
How can hyperhidrosis be managed?
Cut appropriate level of sympathetic nerve roots or use botulinum toxin.
What is the adrenal medulla?
Part of the adrenal gland, located at the centre surrounded by the adrenal cortex. Consists of cells that’s secrete epinephrine and norepinephrine, in response to stimulation by sympathetic preganglionic neurons
What are the adrenal medullary cells modified from?
Modified sympathetic postganglionic cells that have lose their axons and dendrites.
Adrenal medullary cells location and function
Cells form clusters around capillaries where they release norepinephrine and epinephrine into the blood
What is the enteric nervous system?
One of the main divisions of the autonomic nervous system, neither sympathetic nor parasympathetic. Mesh like system of neurons the govern the function of the gastrointestinal tract.
Is the ENS independent, if not what innervates it?
Capable of operating independently of the brain and spinal cord however does rely on innervation from the autonomic nervous system via the vagus nerve and prevertebral ganglia.
What are prevertebral ganglia?
Sympathetic ganglia that lie between the paravertebral ganglia and the target organ
Types of neurons in the ENS
Sympathetic- parasympathetic- secretomotor-
Secretomotor definition
Refers to the capacity of a nerve to induce a gland to secrete a substance
2 plexi in the ENS + locations
Myenteric (Auerbach’s)- between inner and outer layers of muscular external
submucosal (Meissner’s) - in submucosa
Different functions of the ENS
Peristalsis and the churning of the intestinal contents, secretion of enzymes, forming neurotransmitters, segmentation
