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Week 8 Flashcards

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1
Q

What are the autonomic sensory components

A

Receptors:
Viscera- not consciously perceived e.g. baroreceptors which detect blood pressure
Somatosensory/external environment- somatic and autonomic integration

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2
Q

Autonomic motor components

A

Different to somatic:
Effectors innervated
Number of neurones between CNS and effector
Neurotransmission

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3
Q

Efferent (motor) neurones and their effector cells

A

Somatic neurones— skeletal muscle
Sympathetic and parasympathetic (autonomic) neurones —— smooth and cardiac muscle and glands

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4
Q

Somatic neurones

A

Alpha-motoneurone, cell body in spinal cord, direct synapse to skeletal muscle, precise control of effector cells

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5
Q

Autonomic neurones

A

Single pre-ganglionic neurone synapses in ganglia outside CNS to post ganglionic neurone/neurones
Effect a large proportion of effector, widespread control

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6
Q

Neurotransmitter release in somatic neurones

A

Discrete
Very precisely match up motoneurone and muscle cell, accurate degree of functional control

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7
Q

Neurotransmitter release in autonomic neurones

A

Covering a larger area
Loads of neurotransmitter release sites from one post ganglionic neurone, can affect a large number of effector cells

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8
Q

Sympathetic neurotransmitters

A

ACh released by pre-ganglionic neurone in ganglia, noradrenaline (NA) released by postganglionic neurone
Except for sweat glands which are sympathetic but both neurones release ACh

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9
Q

Parasympathetic neurotransmitters

A

ACh released by both neurones no NA

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10
Q

Adrenal medulla, exception

A

Preganglionic neurone form synapse with cells in the medulla, release ACh
Adrenal medulla- neuroendocrine organ
Cells then produce hormone, adrenaline and noradrenaline into the bloodstream
Adrenaline— non-innervated receptors, e.g. smooth muscle of bronchioles/ blood vessels

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11
Q

What do the SNS and PNS do

A

Homeostasis + vision, reproduction
SNS- alert and active: always working, emergency -defence response (flight or fight)
PNS- rest and digest, energy conservation, digestion, emptying bowel and bladder

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12
Q

How do the SNS and PNS work

A

Most organs have dual innervation, antagonistic
Heart: SNS increase heart rate, PNS decrease
GIT: SNS decrease motility and PNS increase
Pupil: pupil dilation is SNS (contraction of radial muscle, dilator pupillae). Pupil constriction is PNS (contraction of circular muscle, constrictor pupillae)
Combine action, most active one dominates

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13
Q

SNS and PNS different types of innervation

A

Dual innervation and not antagonistic, exocrine glands e.g. salivary. SNS and PNS work together
Single innervation e.g. sweat glands is SNS only. most blood vessels SNS only, vasomotor tone increase in SNS=vasoconstriction, decrease SNS=vasodilation

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14
Q

Other cases of blood vessels with SNS and PNS

A

Blood vessels of head and reproductive organs
SNS= vasoconstriction
PNS= vasodilation

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15
Q

Exocrine glands in head and neck

A

SNS and PNS not antagonistic, doing same thing
Exocrine gland gets substance from blood vessel
SNS causes vasoconstriction so reduced flow and raw material to blood vessel supplying gland, but SNS increases substance in gland , small quantity of substance released from gland
PNS causes vasodilation, increased raw material and PNS increases substance in gland so lots substance released from gland
PNS> SNS effect

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16
Q

SNS body wide activation can cause vasodilation
Blood vessels of skeletal muscle and heart

A

Most vessels- an increase in SNS activity, noradrenaline produced to alpha receptors . Vasoconstriction
Vessels of skeletal muscle, smooth muscle cells in these vessels have more beta receptors so an increase in SNS produces adrenaline to beta receptors causing vasodilation

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17
Q

SNS and PNS working together

A

Male sex organs
PNS-erection, p for point
SNS- ejaculation

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18
Q

Interaction of autonomic and somatic systems

A

E.g. focusing eye on near object:
ANS- pupil/ lens adjustments
Somatic- eye movement
E.g. response to cold:
ANS-vasoconstriction in skin
Somatic- shivering

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19
Q

What is the enteric nervous system

A

3rd division of ANS sometimes classed as parasympathetic
Targets smooth muscles and secretory cells associated with digestive system
Intramural plexus in GIT
Intrinsic innervation of GIT - oesophagus to rectum, pancreas and biliary system
Contains lots of types of neurotransmitter

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20
Q

Where is enteric nervous system

A

Two major plexuses of ganglion cells and their fibre bundles
Submucosal (Meissner’s ) plexus - stomach and intestines only
Myenteric (Auerbach’s) plexus- full length of GIT, extensively interconnected
Wall of GIT

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21
Q

Wall of GIT

A

Longitudinal muscle
Myenteric plexus
Circular muscle
Submucosal plexus
Submucosa
Mucosa
Lumen

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22
Q

Types of neurones in ENS

A

Afferent: mechanoreceptors and chemoreceptors
Interneurons: excitatory and inhibitory
Efferent (secretomotor) neurones: excitatory or inhibitory, many neurotransmitters including ACh, various peptides
Effectors: motor and secretory- short reflex

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23
Q

What do enteric reflexes do

Study These Flashcards
A

Control: motility, secretion, blood flow to the gut
Motor reflex- Myenteric plexus- synapse with both smooth muscle layers
E.g. peristalsis

24
Q

ENS- Myenteric plexus
Peristalsis

Study These Flashcards
A

One stimulus
To move bolus along need coordination of contraction and relaxation of smooth muscle
Contraction behind bolus and dilation in front(relaxation)
Mucosal stimulation, distension , Myenteric plexus

25
Secretory reflex- submucosal plexus
Both plexuses are connected together, interneurons process info Reflex arc: food-> sensory receptors (mechano, chemo) -> ENS(submucosal plexus) -> secretory neurones-> increase secretion (mucus, enzymes, acid) -> food Right type of secretion varies depending on where you are in GIT
26
Blood flow ENS
Myenteric/ submucosal plexus Vasoactive neurotransmitters Affect smooth muscle in blood vessels, efferent neurones within short reflex not innervating smooth muscle in wall of GIT but are in the wall of blood vessels in submucosal layer. Affect blood flow locally
27
Integration of ENS with CNS
ENS <-> SNS/PNS <-> CNS Long reflex CNS influence varies along GIT
28
What dysfunction/ diseases are associated with ENS
Age in number/ function Disease: pathology, ENS specific or NS generally, function Chaga’s disease: trypanosome parasite, toxin leads to neurone death, problems with nutrition, growth and development Achalasia: oesophagus/ sphincter, may be autoimmune, most often seen in elderly, difficulty swallowing and food moving down oesophagus, leads to malnutrition, food avoidance
29
Hirschprung’s disease
Also known as mega colon Congenital absence of ENS neurones, distal colon manifests itself soon after birth Peristaltic wave halts at the section missing ENS neurones, stasis in faeces movement, distension, colitis Abolition of rectoanalreflex, abnormal defaecation, treatment- surgery, colostomy
30
General neurological conditions association with ENS
Parkinson’s- enteric neurones often badly affected, often have gut dysfunction can be prior to motor symptoms Peripheral neuropathies- can include enteric neurones Myasthenia Gravis- autoimmune condition, antibodies against nicotinic receptors on skeletal muscle, nicotinic receptors on neurones, ACh transmission in enteric, some people produce antibodies that affect receptors on muscle and neurones, can affect transmission on ENS
31
Gut brain axis
Irritable bowel syndrome IBS Different from inflammatory bowel disease IBD Doesn’t appear to be anything wrong histologically, dysfunctional interactions between ENS and CNS Drug therapies can help mange symptoms Mental health: microbiome that lives in the gut, bacteria can change and influence ENS function which can influence brain function
32
ENS neurotransmission
Many drug targets Endogenous opioids ( not really found anywhere in PNS other than ENS, lots in CNS) and receptors Opioid peptides in normal enteric transmission so there’s opioid receptors The good: anti-diarrhoeal medication, targets opioid transmission in gut The bad: analgesia e.g. morphine, codeine- causes constipation. Opioid often used for serious conditions, extreme pain
33
The nervous systems
CNS and PNS (anatomical difference- whether nervous tissue is surrounded by meninges) Afferent and efferent Somatic and autonomic Autonomic= sympathetic, parasympathetic and enteric CNS and PNS are continuum not separate or distinct can have a neurone who’s cell body is located in PNS but its axon extends into CNS
34
The spinal cord
Dorsal horn with dorsal root. Somatic afferents synapse with CNS cell bodies Ventral horn with ventral root. Somatic efferent cell bodies and axons Spinal cord to PNS: horn-> root-> mixed spinal nerve-> dorsal/ventral ramus Within lateral horn of thoracic and lumbar regions contains pre-ganglionic sympathetic neuronal cell bodies Pre-ganglionic cell bodies of pelvic splanchnic nerves (parasympathetic) found in lateral (anterolateral) horn of sacral segments S2-4
35
The autonomic nervous system
Innervation of visceral organs, smooth muscle and secretory glands Involuntary control Responsible for maintaining homeostasis. Cardiovascular, respiratory, digestive, thermos-regulative apparatus, excretory Works continuously Divided into sympathetic (involved in constriction of cutaneous arteries, redirects blood to important organs) and parasympathetic (results in decrease HR, increase in glandular secretion and peristalsis in gut) Both divisions are functionally antagonistic maintaining homeostasis, integrate with each other
36
How does ANS work
Cell body in CNS-> preganglionic fibre-> ganglion in PNS (collection of neuronal cell bodies) -> post ganglionic fibre-> target organ or tissue Pre-ganglionic fibre= myelinated, primary neurotransmitter is ACh (cholinergic fibres), synapse in ganglion. Axon crosses meninges and enters PNS Post-ganglionic fibre= unmyelinated, primary neurotransmitters is either ACh or NA(adrenergic fibres), axon supplies effector organ directly
37
Effector organs of ANS
Muscles of body that generate own electrical activity- myogenic Smooth muscle- walls of blood vessels, tube of GIT Cardiac muscle Secretory glands
38
afferent fibres
General visceral afferent GVA fibres (not ANS) send sensory info back to CNS via dorsal root and horn Visceral or autonomic afferent fibres travel in same way as somatic afferent fibres The neuronal cell bodies are located in specific sensory nerve ganglia or cranial nerves or dorsal root ganglia Visceral afferents involved in nociception, excessive tension in smooth muscle and some pathological conditions produce visceral pain Viscera insensitive to crushing, cutting and burning
39
Dermatomes
Afferent fibres from spinal nerves supply cutaneous innervation to a specific region of skin Dermatome maps map out the region of skin innervated by a particular spinal nerve Theres considerable overlap between cutaneous innervation and spinal segments Visceral or referred pain- pain in visceral organs interpreted in a region innervated by same spinal segment E.g. irritation of peritoneum on inferior surface of diaphragm, which is innervated by phrenic nerve can be referred to skin on top of shoulder which is innervated by other nerves from same spinal level
40
Efferent fibres
Somatic efferent fibres consist of a single neurone which synapses with skeletal muscle General visceral efferent GVE fibres or autonomic efferent fibres consist of 2 neurone pathway Preganglionic fibres synapse within ganglia, postganglionic synapse with cardiac or smooth muscle cells or with gland cells
41
Myotomes
Efferent fibres from spinal nerves supply innervation to skeletal muscles within a specific compartment Most skeletal muscles are innervated by nerves derived from several spinal cord levels
42
Sympathetic nervous system
Acts in sympathy, accordance with emotions Provides autonomic innervation to the head, neck, thorax, abdomen, pelvis and blood vessels Preganglionic cell bodies located in lateral horn between t1-l2 Thoracolumbar outflow Ganglion is found in the sympathetic chain or near target organ Short Preganglionic neurone, long post ganglionic neurone
43
SNS exception innervation of suprarenal gland
Cell body in lateral horn of T1-L2 spinal cord No ganglion ACh Direct innervation from sympathetic preganglionic neurone to adrenal medulla chromaffin cells for production of adrenaline
44
SNS exception innervation of sweat glands
Cell body in lateral horn T1-L2 Ganglion in sympathetic chain or near target organ ACh secreted by postganglionic ‘sudomotor’ neurones innervtaing sweat glands and arrector pili muscle of skin No NA produced only ACh
45
Sympathetic ganglia
Sympathetic chain, paravertebral chain, found in thoracic cavity Pre-aortic ganglia found in aorta
46
Cervical ganglia -sympathetic ganglia
Found behind carotid sheath, nerve synapsing with these ganglia dont originate from cervical part, come from T1-T3/5 ascend upwards Superior cervical ganglia C2-3= pupil dilation and inhibition of salivation. Supplies nerves C1-4, largest Middle C6 cervical ganglia= innervate thyroid + parathyroid gland, trachea, oesophagus, heart. Smallest ganglion, supplies nerves C5-6, sometimes not present Inferior cervical ganglia C7-T1 level (Stellate ganglia) innervates upper limb, supplies C7, C8, T1 sometimes C6 if middle ganglia present
47
Abdominal ganglia
Receive innervation via splanchnic nerve , dont synapse with sympathetic chain Greater (T5-9)/ lesser(T9-10), least (T11-12) Pre-aortic (pre-vertebral) ganglia: Celiac = all nerves,found in abdominal aorta, pain and sensation from foregut Superior mesenteric = found where superior mesenteric artery leaves abdominal aorta, lesser nerve Inferior mesenteric= receives innervation from lumbar splanchnic
48
Sympathetic innervation
Pre-ganglionic neurones depart lateral horn (T1-L2) Pass through ventral root Enter sympathetic chain via white ramus communicantes (myelinated) Synapse at sympathetic ganglion Post ganglionic neurones depart via grey ramus communicantes (unmyelinated) Dorsal ramus will supply back, ventral ramus supplies anterior body and limbs Meningeal ramus supplies dura mater
49
Routes in sympathetic chain
Can either synapse with ganglion on same level or ascend or descend or pass medially and synapse with ganglion not in sympathetic trunk divergence= one Preganglionic neurone projects to several post ganglionic neurones Convergence= one postganglionic neurone receives innervation from several pre ganglionic neurones Occurs via the inter ganglionic nerves connecting ganglia Allows widespread effects on target organs
50
Parasympathetic nervous system
Counterbalances affect of sympathetic Provides autonomic innervation to head, neck , thorax, pelvis, abdomen, blood vessels Preganglionic cell bodies located in cranial nerve nuclei (CNIII, VII, IX, X) and lateral horn of sacral segments S2-4 Craniosacral outflow Ganglion is found near target organ or within walls of tissue intramural Long pre ganglionic, short post ganglionic Both ACh
51
PNS innervation
CN nuclei (CNIII, VII, IX, X)= cell body in brainstem, ganglion near target organ, head neck, thorax , upper abdomen Lateral horn of S2-4= cell body in sacral spinal cord, ganglion, lower abdomen and pelvis Craniosacral outflow with ACh as primary neurotransmitter for both preganglionic and post ganglionic neurons
52
Parasympathetic ganglia in head
Ciliary- Oculomotor nerve CNIII, synapse in ciliary ganglion, post ganglionic fibres innervate sphincter of pupil and ciliary muscle, both muscles act to produce accommodation reflex Pterygopalatine - facial nerve CNVII, innervates lacrimal gland and nasal gland, increased secretion Submandibular -facial nerve CNVII, innervates submandibular and sublingual glands Otic- glossopharyngeal nerve CNIX, innervates parotid gland, increased secretion
53
Parasympathetic vagus nerve
Long pre-ganglionic fibre CNX-> cardiac plexus-> SAN, AVN CNX-> pulmonary plexus-> bronchi CNX-> intramural ganglia-> foregut (stomach and pancreas) CNX-> intramural ganglia-> midgut (small intestines) Contraction of smooth muscles,increases gastric secretion, increase motility and peristalsis
54
Parasympathetic pelvic splanchnic
Anterolateral horn S2-4 Intramural ganglia Innervate bladder, rectum, prostrate or vagina and erectile tissue of penis and clitoris S2- second half perineum (enteric) and bladder sphincter S3- colon S4- erectile tissue of penis/clitoris
55
Plexuses of enteric
Myenteric= peristalsis Submucosal= glandular secretion
56
Autonomic innervation of gut
Parasympathetic: vagus nerve (foregut and midgut), pelvic splanchnic nerves S2-4 (hindgut) Sympathetic: thoracic and lumber splanchnic nerves T1-L2/3, celiac ganglion (foregut), superior mesenteric ganglion (midgut), inferior mesenteric ganglion (hindgut) From autonomic plexuses around arteries and follow blood vessels to reach target organ

NAS (12 decks)

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