Autonomic Flashcards
The PNS is divided into?
The somatic and autonomic NS
The autonomic NS has which devisions?
Sympathetic, parasympathetic, enteric
Characteristics of the somatic NS
- Voluntary movements
- Main effectors: sceletal muscles
- One synapse between CNS and effector muscle
Characteristics of the autonomic NS
- Involuntary control of bodily functions
- Main effectors: smooth muscles, internal organs
- Two synapses between CNS and effector muscle
Homeodynamics
The integration of homeostatic functions regulated by the autonomic NS with voluntary
movements controlled by the somatic NS
Does the somatic and autonomic NS fight over controll?
No, they support each other to make living possible.
E.g. the autonomic system increases blood flow to muscles when we want to run (using muscles with somatic projections)
Explain the somatic efferent pathway
Information from a lower motor neuron in the spinal cord projects directly to a muscles
Explain the autonomic efferent pathway
Neuron in the spinal cord or brain stem (pre ganglionic) synthesize and secrete ACh project onto a neuron in the periphery (post ganglionic), which sends it’s signals to the smooth muscle either in a synapse or through a varicosity.
varicosities
When the neuron is stimulated, varicosities (some type of terminal) release neurotransmitters along a significant length of the axon and, therefore, over a large surface area of the effector tissue. The neurotransmitter diffuses through the interstitial fluid to wherever its receptors are located in the tissue. This diffuse release of the neurotransmitter affects many tissue cells simultaneously
Difference between neuron and ganglion
Neuron is 1 unit projecting through an axon. A ganglion is a nucleus in the peripheral NS which projects through fibers.
The enteric NS is completely controlled by?
enteric ganglia (control the function of the complete gastrointestinal tract from esophagus to rectum, including gall bladder and pancreas)
Can the ENS control functions of the gastrointestinal tract with it’s separated from the CNS?
Yes
How many neurons in the enteric NS?
500 million (speaks to complexity)
What are the 2 plexi of the enteric NS?
- Myenteric plexus (for smooth muscle movements of the
gastrointestinal tract, peristaltic propulsion of food) - Submucosus plexus (regulates mucosal function)
What’s the largest & most complex division of the ANS
The ENS
Sensory ENS neuron for intestines
GPR65
Sensory ENS neuron for the stomach
GLP1R
Hirschsprung’s disease (HSCR)
characterized by an absence of enteric (intrinsic) neurons from variable lengths of the most distal bowel.
The disease is a developmental disorder, where we have a loss/non-development of enteric neurons –> lead to food not being transported down the tract (gets struck) and we have clog where we need surgery.
Core differences between the sympathetic and parasympathetic NS
1) Sympathetic has a chain and has preganglionic neurons in the spinal cord, the parasymp has preganglionic cells in the brain stem or sacral part of the spinal cord
2) The axons of the preganglionic neurons for the symp are short and axons from the postganglionic cells are long. It’s the opposte from parasym
3) Symp releases Ach from the preganglionic cells and norepinephrine from the preganglionic where parasymp just releases Ach
Symp vs parasymp: function
fight or flight vs rest and digest
Symp vs parasymp: Preganglionic
neurons
Lateral horn thoracic to lumbar spinal cord
vs
Brainstem or lateral grey matter in sacral spinal cord
Symp vs parasymp: Ganglionic
neurons
Sympathetic ganglion on either side of vertebral column
vs.
Terminal or intramural ganglion; close to organs
Symp vs parasymp: axons
Pre-ganglionic: short, Post-ganglionic: long - Extensive innervation
vs
Pre-ganglionic: long, Post-ganglionic: short - Sparse innervation
Symp vs parasymp: Neurotransmitter/hormonal release
Simultaneous, „mass activation“ (e.g. through adrenal gland)
vs.
Local, organ-specific
receptors at the pre/post ganglionic synapse
ACH-R’s: muscarinic receptors (G-coupled and slow) and nicotinic receptors (ionotropic and fast)
receptors at the norepinephrine synapse at neurovascular junction
alpha-2 (presynaptic inhibition) or alpha-1 (postsynaptic transmission) adrenergic receptors
Pharmacological treatments triggering ANS
Hypertension (β-Blockers)
Asthma (β-Agonists)
Sexual dysfunction (PDE5-Inhibitors)
Lack of bladder control (Muscarinic Antagonists)
Which are the 3 ways that the ANS work as antagonists but not really?
1) antagonistic actions at the cellular level (actually doing the opposite: e.g. increase HR, decrease HR)
2) functional antagonism (functionally doing the opposite, but using different muscles to do so. E.g.: Contract pupil dilator muscle, Contract pupil sphincter muscle)
3) Different but not opposite actions (non-related functions. E.g.: Sweat secretion, Contract bladder body)
is parasymp or symp active when bladder is full?
Sympathetic
Name of receptors that detect stretch in the vessels
baroreceptors
Where do the baroreceptors project to?
Solitary nucleus –> project to inhibitory interneuron that will inhibit the sympathetic system if blood pressure is high and not if it’s low
Which nerve detects stretch of the bladder? And what does it do if it’s high?
The pelvic nerve –> projects to the PAG, which projects to the pontine center, which will send an interneuron to inhibit Onuf’s nucleus
What makes the external sphincter tight?
Signals from Onuf’s nucleus
Can CNS affect blood pressure?
Yes, it has modulatory powers that can affect the gain module (schematic representation)
3 bodily responses to fear
1) endocrine reactions: the HPA axis releases corticotropin release factor and signals to the adrenalin glands
2) behavioral responses (running away)
3) Autonomic changes: supports behaviors
the function of higher/lower parts of the brain in defensive behaviours
Higher part: identifying threat, comparing it to memory (cortex, amygdala, hypothalamus and PAG)
Lower part: execution of motor plan and still a little integration (PAG, dorsal nucleus of the dorsal vagus, nucleus)
PAG function and connections in defensive behavior
- Anatomic and functional interface between the forebrain and the lower brainstem
- Major role in integrated behavioral responses to internal (e.g., pain) or external (e.g., threat) stressors
- Inputs from the prefrontal cortex, amygdala, hypothalamus, and nociceptive pathways
- Coordinates specific patterns of cardiovascular, respiratory, motor, and pain modulatory responses
Protein used in optogenetics to depolarize cells
Channelrhodopsin 2 (ChR2)
Virus used to insert proteins in cells for optogenetics
Adenovirus
Proteins (2) used in optogenetics to hyperpolerize cells
Halorhodopsin (NpHR) & Archaerhodopsin (Arch)
Stimulating the dorsal PAG (glutamate) leads to?
Fight responsne
Stimulating the ventral PAG (glutamate) leads to?
Freeze
Does optogenetic activation leads to only the cells they target firing?
No, the brain is a network. E.g. a freezing response is related to a decrease in HR
feedback from visceral reflexes is in the lower brain stem - but with nucleus?
Solitary nucleus
Integration of visceral feedback/interoception into „higher order“ CNS functions requires which areas?
PAG, amygdala, cortex
Does interception affect how we see stimuli?
Yes, interceptive responses to our visceral and somatic responses might modulate perception of a threat and thereby the emotional state –> how anxiety might work
2 models for emotions
1) Bottom up (James-Lange): we run because we’re afraid
2) top-down (Cannon-Bard - current): stimuli lead to emotional state, which is associated with autonomic and behavioral responses
The hypothalamus consists of?
A collection of heterogenous nuclei
The hypothalamus is important for?
Homeostasis Controls the following things: - Blood pressure / electrolyte composition - Energy metabolism - Reproductive behavior - Body temperature - Defensive behavior - Sleep wake cycle - Growth
3 devisions of the paraventricular nucleus of the hypothalamus
Magnocellular neuroendocrine division: vasopressin / oxytocin
Parvicellular neuroendocrine division: somatostatin / thyrotropin-releasing hormone / corticotropin releasing hormone
Descending division: projections to brain stem and spinal cord.
The Arcuate nucleus of the hypothalamus is involved in?
Feeding behaviour. Neurons here attach a negative valence to hunger so we are more likely to seek out food when we’re hungry
Nuclei involved in aggression
- subnucleus of the ventromedial hyp is involved in agression behaviour
- ventromedial hypothalamus is important in male aggression
- Septal-hypothalamic circuit for aggression regulation
The Pituitary is divided into 2:
Anterior pituitary (Adenohypophysis) & Posterior pituitary (Neurohypophysis)
Differences between the anterior/posterior pituitary
1) neruons synthesising NTs and prokjecting to the area:
anterior: Parvicellular neurons - posterior: Magnocellular neurons
2) vessel set up:
anterior: Parvicellular neurons –> Hypophyseal artery ( long portal vessel) –> vessels of the Adenohypophysis
posterior: Magnocellular neurons –> vessels of the Neurohypophysis
Basically: indirect vs direct delivery
3) The NT’s released
NTs released by the Adenohypophysis
see slide 35 for all, but most important so corticotrophin release factor
NTs released by the Neurohypophysis
Vasopressin (ADH) & Oxytocin
The anterior pituitary includes processes like
stress reaction, growth, reproduction, and lactation
How does the HPA induce stress?
corticotrophin is released –> triggers adrenocorticotrophin –> goes through bloodstream to the adrenocortici cortex –> release of cortisol
cortisol mobilize and signal that it has to adapt to a stressor (important for the stress response –> might release adrenaline)
cortisol travels back to the CNS and is a negative feedback system and thereby shuts it’s off in it’s place of origin to ensure that stress doesn’t last forever
Cortisol falls into what type of hormon?
Glucocorticoid hormone
