Central Control Of Autonomic Function Flashcards
Provide a specific example of an autonomic pathway
Micturition response
Where do afferents originate
Viscera- internal organs in main cavity (especially abdomen)
Where does afferent info involved in reflex arcs come from? What mediates this info
Comes from visceral afferents- wall of intestine, wall of bladder
Mediated by autonomic nervous system
What are general visceral afferents (GVA)
- originate around an organ
- small fibres
- mixed nerves (motor and sensory)
What does GVA information contribute to
Regulating homeostasis
What do GVA neurotransmitters cause the release of
Glutamate
AngII, CCK, oxytocin, somatostatin
What does the enteric NS regulate? How?
Regulate GI motility
Mechanoreceptors of gut wall send afferent input to spinal cord
By reflex control without much descending control using the autonomic NS ‘control system’
Sympathetic NS- what NT is released from preganglionic and postganglionic efferent neuron
Pre- Ach (NAChR)
Post- NA (GPCR- adrenergic)
Parasympathetic NS- what NT is released from preganglionic and postganglionic efferent neuron
Pre- Ach (nACR)
Post- Ach (GPCR- muscarinic)
SNS vs PNS which has long preganglionic efferent neuron
SNS- short pre- long post
PNS- long pre- short post
What spinal cord region controls SNS vs PNS efferents
SNS- preganglionic neuron in thoracic or lumbar spinal cord
PNS- preganglionic neuron in cranial nerves or sacral spinal cords
Where are reflex arc cell bodies found (autonomic NS)
Preganglionic neuron- cell bodies in CNS
Postganglionic neuron- cell bodies in ganglia of PNS
What type of fibres are pre/postganglionic efferents of autonomic NS
Preganglionic efferent- type B
Postganglionic efferent- type C
List the types of sensory fibre types and what it supplies
Ia and Ib- primary muscle spindles, golgi tendon organs
II- secondary muscle spindles, skin mechanoreceptors
III- skin mechanoreceptors, thermal receptors, nociceptors
IV- skin mechanoreceptors, thermal receptors, nociceptors
List motor fibre types
B- preganglionic autonomic nervous system
C- postganglionic autonomic nervous system
A-alpha- extrafusal skeletal muscle fibres
A- gamma- intrafusal muscle fibres
Sensory fibres diameter and conducting velocity
- wide diameter, myelinated = faster
Ia and Ib- 0.13-20 micro m, 80-120 m/s
II- 0.16-12 um, 35-75 m/s
III- 0.11-51 um, 15-30 m/s
IV- 0.2-1.5 um, 0.5-2 m/s
Motor fibre type diameter and conducting velocity
A-alpha- 0.12-20 um, 80-120 m/s
A-gamma- 0.12-8.2 um, 35-37 m/s
B- 0.21-33 um, 3-15 m/s
C- 0.2-2 um, 0.5-2 m/s
What are splanchnic nerves
Mixed nerves that innervate the viscera
How many neurons for efferent and afferent pathways
Efferent- 2- pre/post
Afferent- 1- GVA (general visceral afferents)
Explain Sympathetic reflex = Autonomic Reflex Arc components
Afferent: 1 neuron. GVAs (general visceral afferents) sense stretch- cell bodies in dorsal root ganglia.
Afferent synapse to efferent
Efferent: 2 neurons. Preganglionic and postganglionic. Preganglionic cells concentrated in lateral horn, exit spinal cord via ventral root and enter paravertebral ganglia at same level. Preganglionic cell may synapse at paravertebral ganglia or pass through to enter a splanchnic nerve and travel to a prevertebral ganglia
Difference between efferent pathway in autonomic sympathetic reflex vs somatic motor neurons reflex
Autonomic- Two neuron pathway
Delete
D
How are Preganglionic fibres formed
Specialized motor neurons
Where are sympathetic Preganglionic neurons found
Found in intermediolateral cell columns in the spinal cord- lateral horn (T1-L2)
Where are postganglionic neurons found
- in paravertebral ganglia (chain of ganglia beside the spinal cord)
- in prevertebral ganglia (within abdominal cavity)
- project to smooth muscles, glands, other targets
What kind of receptor is used for transmission between Preganglionic and postganglionic neurons (sympathetic)
Nicotinic or muscarinic ACh receptors (fast vs slow EPSP)
What kind of receptor is used for postganglionic neurons to target cell (sympathetic) and what NT
Alpha or beta adrenergic receptors
NE is neurotransmitter
Name the 6 Sympathetic responses
- ciliary muscle (beta): Pupil dilation
(mydriasis); enhances far vision - heart (beta 1): SA node and ventricles; increases HR and contracility
- stomach (alpha, beta 2): Decreased
motility, sphincter contraction, reduced secretions - small intestine (alpha, beta 2): Decreased
motility, sphincter contraction, reduced secretions - lungs (beta 2): Bronchodilation, increased ventilation
- abdominal Arterioles (alpha, beta 2): Constriction; diversion of blood from GI tract to muscles
What does increased cortisol production cause
Mobilization of carbohydrates and lipid stores for energy metabolism
What is the neuron organization in parasympathetic reflexes
Afferents are GVA
Efferents have 2 neuron motor pathway (pre/post)
Locations of neurons in parasympathetic reflexes
- presynaptic neuron cell bodies in cranial nerves III, VII, IX, X (brain stem) and sacral spinal cord (S2, S3, S4)
- postsynaptic neurons located in ganglia near or in wall of target neuron
Differences in sympathetic and parasympathetic reflexes
- location of presynaptic and postsynaptic efferents
- smooth muscles of blood vessels receive exclusively sympathetic innervation
Name the 7 parasympathetic responses
- ciliary muscles (M3): Pupillary constriction (miosis); enhances near vision
- salivary and lacrimal glands (M3): Increased secretion
- heart (M2): Decreased HR and contractility
- stomach and intestine (M1, M2, M3): Increased motility, relaxation of sphincters, increased secretion
Lungs (M3): Bronchoconstriction
Abdominal Arterioles (M3): Vasodilation
Bladder (M2, M3): contraction, sphincter relaxation
What causes the firing of ANS preganglionic neurons
Controlled by pathways that synapse onto them (not cortex )
- spinal reflex arc
- brain stem reflex pathways
- descending control originating from hypothalamus
What regulates autonomic function
hypothalamus
- preoptic region
- Septal region
- lateral hypo
What things does the ANS regulate
- temperature regulation
- food/water intake
What effects if damage to ANS
Temperature:
• Lesions to the heat loss centre (preoptic center/anterior
hypothalamus) prevent sweating and cutaneous vasodilation, lead to hyperthermia
• Lesions to the heat conservation centre (posterior
hypothalamus) can cause hypothermia
Food intake:
• Glucoreceptors in the hypothalamus activated when blood glucose levels drop
• Lesions to lateral hypothalamus suppress food intake
(aphagia), can cause starvation and death
• Lesions to the ventromedial area (satiety center) results in
hyperphagia, can lead to obesity
What is the micturition pathway (overview)
- involves spinal reflex and descending input from a supraspinal centre
- sympathetic input inhibits destructor (beta) and excites internal sphincter (alpha)
- external sphincter is striated- somatic innervation
Micturition afferent
- stretch activates (GVA) afferents project to pons
- commands reach sacral spinal cord via the reticulospinal pathway
Explain Micturition Pathway
Lecture 9 ANS
What does the body do to warm up or cool off
• Cooling causes shivering, piloerection, increase in thyroid
activity
• Warming reduces thyroid activity, sweating and vasodilation
