NSCI 201 Chapter Notes - Chapter 21: Anterior Grey Column, Neuromodulation, Sweat Gland

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NSCI 201 (19.21)
Visceral Motor System
24th March 2016
Visceral Motor System!
Sympathetic and parasympathetic divisions of the visceral motor system!
Sympathetic: Fight or flight response, helps prioritise processes to this purpose. (eg., liver
converts glycogen to glucose). Parasympathetic processes shut down. Leaves from lumbar and
thoracic spinal cord sections, through sympathetic chain ganglia.!
!
Parasympathetic: Rest and digest response, includes salivation, urination, erections. Leaves
from brainstem and sacral spinal cord sections, nothing in between.!
!
At any given time, there is typically a balance between sympathetic and parasympathetic
activations. This being said, some processes are strictly one or the other. (eg. No
parasympathetic component to sweat gland activation)!
!
Somatic vs Visceral (autonomic) nervous systems!
!
Somatic
Visceral
Cell bodies of lower MN in ventral horn
Cell bodies of postganglionic neurons in PNS
Targeted projections to specific sites on muscles
Diffuse projections to many parts of target tissue
Limited branching
Extensive branching
Specific synapses
Extensive diffusion and volume transmission
At neuromuscular junctions:!
!
ACh > nicotinic RC > depolarization
!
ACh or norepinephrine, many RC types with varied
effects
Upper MNs regulated by motor/premotor cortices
Medial PFC, insula, amygdala, hypothalamus!
(Less cortical influence; ess conscious control)
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NSCI 201 (19.21)
Visceral Motor System
24th March 2016
The hypothalamus!!
!
!
!
!
The hypothalamus is a multinucleate
structure important in regulating responses
to threat. !
!
!
Receives direct input from reticular
formation, releases outputs (e.g.
hormones: cortisol, estradiol) through
pituitary gland. !
!
!
!
!
!
!
!
!
!
!
!
Regulates homeostasis, esp: !
1.Blood flow!
!
!Adjusts cardiac output, !
!Vasomotor tone, !
!Blood osmolarity!
!Renal clearance!
!Motivates drinking, salt consumption!
!
2. Energy!
!Monitors blood-glucose levels,!
!Feeding activity,!
!Digestive rate,!
!Metabolic rate, body temperature!
!
3. Reproductive activity!
!Sexual behaviour, !
!regulation of hormone cycles,!
!Pregnancy/ lactation!
!
4. Coordination of responses to threat!
!Modulates stress hormone release!
!Parasym/sym balance!
!!!!!!!!Allocation of blood flow!
!
Takes contextual information of ideal state and sensory input of current state, compares and
modifies subconscious aspects of physiology to maintain homeostasis!
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NSCI 201 (19.21)
Visceral Motor System
24th March 2016
!
Organization of the preganglionic spinal outflow to sympathetic ganglia!
!
In sympathetic, lots of spinal neurons
making synapse with one proximal post-
ganglionic neuron.!
!
In parasympathetic, much closer to 1:1. !
!
In visceral nervous system, neurons start
in lateral horn, then leaves through
vertebrae to sympathetic chain ganglia
through white communicating ramus.!
!
Information either synapses in ganglia or
goes back out through gray
communicating ramus into bv in skin.!
!
In lower thoracic/ lumbar, pre-vertebral
ganglia are closer to target organs,
further away from spinal cord.!
!
Adrenergic receptor types and some of their effects in sympathetic targets!
Different receptor types can cause different effects in signalling with the same neurotransmitter!
!
All sympathetic fibres use ACh/ noradrenaline (different receptors)!
!!
alpha/ beta fibres: All three types of beta fibres use Gs protein; depolarising effects. Gi is
inhibitory (opposite), decreases cAMP pathway. Gq is coupled to PKC, increases cAMP.!
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