NERVOUS SYSTEM: CENTRAL CONTROL OF AUTONOMIC FUNCTION Flashcards
Define: referred pain?
pain felt in one location but the source of the pain may be somewhere else.
Describe the general functions of the autonomic nervous system (ANS) and name its two major divisions.
- Controls cardiac and smooth muscles, endocrine glands, GI system
- sympathetic and parasympathetic
How do the sympathetic and parasympathetic preganglionic cell bodies differ in terms of
- location
- neurotransmitter
sympathetic preganglionic cell body
- thoracolumbar spinal cord
- ACh
Parasympathetic preganglionic cell body
- craniosacral
- ACh
How do the sympathetic and parasympathetic postganglionic cell bodies differ in terms of
- location
- neurotransmitter
sympathetic postganglionic cell bodies
- close to vertebrae and far from target
- norepinephrine
parasympathetic post ganglionic cell bodies
- near to or within wall of organ target location
- ACh
How do preganglionic efferents and post ganglionic efferents differ?
- Cell type
- fiber dimeter
- conduction velocity
pre ganglionic efferents are type B fibers
- fiber diameter is 0.21 - 33 um
- conduction velocity is 3-15 m/s
post ganglionic efferents are type C fibers
- fiber diameter is 0.2-2um
- conduction velocity is 0.5-2m/s
Explain an autonomic sympathetic reflex from the visceral general afferent to the digestive tube
- Visceral general afferents release excitatory neurotransmitters on preganglionic cells concentrated in the lateral horn.
- Preganglionic fibres exit the spinal cord via ventral root and enter paravertebral ganglia in the same level.
- Exit spinal cord via ventral root and enter paravertebral ganglia at the same level
- Some synapse here
- Some give off collaterals that travel rostrally or caudally
- Some pass through the ganglia and enter a splanchnic nerve to travel to a prevertebral ganglia. Splanchnic nerves are mixed nerves that innervate the viscera
- Splanchnic nerve contains both postganglionic fiber and visceral sensory fiber
How do sympathetic reflexes in the autonomic nervous system differ from the somatic nervous system?
- reflexes involve 2 neuron efferent pathway
- afferents are known as general visceral afferents
Describe what adrenergic receptor type is located at the ciliary muscle and what response sympathetic stimulation elicits
a type
pupil dilation (mydriasis); enhancing far vision
Describe what adrenergic receptor type is located at the heart muscle and what response sympathetic stimulation elicits
B1
acts on SA node and ventricles increased heart rate, increased contractility
Describe what adrenergic receptor type is located at the stomach and what response sympathetic stimulation elicits
a, and B2
decreased motility, sphincter contraction, reduced secretions
Describe what adrenergic receptor type is located at the small intestine and what response sympathetic stimulation elicits
a, B2
decreased motility, sphincter contraction, reduced secretions
Describe what adrenergic receptor type is located at the lungs and what response sympathetic stimulation elicits
B2
bronchodilation, increased ventilation
Describe what adrenergic receptor type is located at the abdominal arterioles and what response sympathetic stimulation elicits
a, B2
constriction and diversion of blood from GI tract to muscles
What are the key differences between parasympathetic reflexes and sympathetic reflexes
parasympathetic reflexes
- cell bodies of presynaptic neurons are in cranial nerves III, VII, IX, X and sacral spinal cord S2, S3, S4
- post synaptic neurons are located in ganglia near or even in wall of target organ
- not present in smooth muscles of most blood vessels (primarily sympathetic innervation)
Describe what muscarinic receptor type is located at the ciliary muscles and what response parasympathetic stimulation elicits
M3
- contraction for near vision
Describe what muscarinic receptor type is located at the salivary and lacrimal glands and what response parasympathetic stimulation elicits
M3 - increased secretions
Describe what muscarinic receptor type is located at the heart and what response parasympathetic stimulation elicits
M2
decreased heart rate and contractility
Describe what muscarinic receptor type is located at the stomach and intestine and what response parasympathetic stimulation elicits
M1, M2, M3
Increased secretions, increased motility, sphincter relaxation
Describe what muscarinic receptor type is located at the lungs and what response parasympathetic stimulation elicits
M3
brochoconstriction
Describe what muscarinic receptor type is located at the abdominal arterioles and what response parasympathetic stimulation elicits
M3
vasodilation
Describe what muscarinic receptor type is located at the bladder and what response parasympathetic stimulation elicits
M2, M3
sphincter relaxation
What are the components of the pathways that control firing of the autonomic nervous system?
Spinal reflex arcs, brainstem reflex pathways, and descending controls from the hypothalamus
What 3 regions regulate autonomic function
hypothalamus, preoptic and septal regions
hypothalamus function
regulates body temperature, hunger and thirst, mood, sex drive, blood pressure, and sleep
How does the heat loss centre of the hypothalamus respond if we are too warm?
decrease in thyroid activity,
sweat
vasodilation
How does the heat conservation centre respond if we are too cold?
shivering, piloerection, increase in thyroid activity
Describe the location of the heat loss centre and what a lesion to these areas would cause
- preoptic center and anterior hypothalamus
- prevent sweating and cutaneous vasodilation
- leads to hyperthermia
Describe the location of the heat conservation centre and what a lesion to these areas would cause
- posterior hypothalamus
- hypothermia
What happens in the hypothalamus when blood glucose levels drops?
glucoreceptors activate
What happens if there is damage to the lateral hypothalamus?
aphagia (suppressed food intake - inability to swallow)
can cause starvation and death
What happens if there is damage to the ventromedial area of the hypothalamus
it is the satiety centre.
results in hyperphagia (insatiable appetite), can lead to obesity
What causes syphilis
bacteria called treponema pallidum
Describe the primary, secondary, tertiary stages of syphilis
primary (days-weeks): single sore (chancre)
secondary (months): body, hands, feet, rash
tertiary (years-decades): neurological, cardiovascular, gummas, Argyll Robertson Pupil
Define: gummas
soft swelling of brain, liver, testes, heart
Define: Argyll Robertson Pupil
Pupil does not react to light but accommodation reflex is still normal;
Due to damage of the optic nerves in the pretectal area by bacteria
define: micturition
the act of urination
Describe the micturition reflex including the neurotransmitters, receptors, and intracellular signalling pathway
- Involves spinal reflex and descending input from a supraspinal centre
- sympathetic input: norepinephrine is released onto B adrenergic receptors of detrusor resulting in inhibition and on a adrenergic receptors on internal sphincter resulting in activation
- detrusor muscle contracts during urination to push urine out of bladder
- the external sphincter which is controlled voluntarily (somatic innervation - pudendal nerve), contracts to pee
- parasympathetic input originating from sacral nerve 1, 2, 3: ACh releases onto muscarinic receptors on urinary bladder and internal sphincter. results in urinary bladder contracting and internal sphincter relaxing
