Download visceral motor - Ollie Hulme`s website

BIOL455 COMPARITIVE NEUROBIOLOGY
LECTURE#22: VISCERAL MOTOR"
DR. OLLIE HULME"
FALL 2010 "
UBC
Housekeeping"
[email protected]"
[email protected]"
office hours (Fri 1.30-4.30)
Answer key + sample
questions (inserted
into slides) are now
up on website
www.hyooom.com"
Neuroanatomy from lecture 9 is recommended for
helping to understand all sensory, motor and cognitive
topics, but will not be explicitly tested
Visceral motor system"
Viscus = internal organ
Visceral= plural of viscus
Visceral motor system = Autonomic nervous system
History"
Gaskell stimulated different parts of
visceral motor system demonstrating
effects on downstream organs
Every tissue is innervated by two sets of nerve fibres of
opposite characters
Pioneered pharmacology of visceral
system – Ach + NA
History"
Walter Cannon elucidated
relationship between visceral motor
system, homeostasis and emotion
Visceral motor function"
Controls involuntary bodily functions mediated by
smooth muscle, cardiac muscle and glands
3 major divisions
1. Sympathetic
2. Parasympathetic
3. Enteric
Sympathetic"
Specialised for challenging
situations
fight or flight
Expends resources
Parasympathetic"
Specialised for quiescent
conditions
‘rest and digest’
Replenishes resources
Restores homeostasis
Central control for…"
somatic motor system =
Upper motor system (Motor
cortices + brain stem nuclei)
visceral motor system =
hypothalamus
Differences between somatic & visceral"
1. Less distinct somatopy
2. Lower motor system of visceral motor located
outside of CNS
3. Contacts between motor neurons and viscera are
less differentiated – e.g no endplates
4. Visceral neurons release diversity of neuroTs
including cotransmission of neuropeptides
5. Greater diversity in receptors mediating greater
range of postsynaptic effects in smooth + cardiac
muscle and glands
Sympathetic"
Sympathetic neurons contribute to virtually all peripheral
nerves innervating a huge range of organs
Sympathetic responses"
Fight or flight
Pupil dilation / Eyelid retraction
Skin + gut vessels constrict
Piloerection
Bronchi dilate
Cardiac rate + force increase
Adrenaline + Noradrenaline into blood
Sympathetic"
Sympathetic neurons driving
these effects
Sympathetic responses"
Not only active during fight or flight,
just maximally active
Maintains tonic activity in all
circumstances
Also it doesn’t activate all together
since different components of the
system can be independently
controlled according to functions
required
Exercise, sex, urination, sleep etc.
Parasympathetic sources"
Parasympathetic
stems from…
Brain stem nuclei
Or
Sacral section of
spinal cord
Parasympathetic brain stem"
Pupillary
response
Saliva + tear
glands
Cardiac
inhibition
Sacral region "
Colon
Rectum
Bladder
Genitals
Parasympathetic in spinal cord"
Parasympathetic effects"
‘Rest and digest’
Constriction of pupils
Slowing of heart
Peristalsis of gut
Dilation of vessels in skin + gut
Piloerector relaxation
Decreased Adrenaline and
noradrenaline released
Enteric system"
Modulated by parasympathetic
+ sympathetic
Works largely
independently
through its
own reflexes
Sensory components of visceral system"
1. Provides local feedback
(stretch, pressure,
chemical, nociceptive) for
ongoing motor activity
2. Informs higher integrative
centers
Sensory input is sparse therefore
explains why hard to localise
visceral pain
Convey only limited information to
consciousness e.g unaware of
blood pressure, heart rate etc
Nucleus of solitary tract"
Central control over visceral motor"
Cortical regions of visceral motor"
= Primary
visceral motor
= Primary
visceral
sensory
Regions involved in integrating visceral information with
input from other senses / cognitive processes
Hypothalamic region of visceral motor"
Hypothalamus"
Critical role in coordination + expression of visceral
motor activity
Hypothalamic function"
Computes error signal and
uses this to correct
homeostasis through
visceral motor system
Cardiac reflexes, Bladder control,
sexual reflexes, Temperature,
Breathing, Eating,
Hypothalamic function"
Can group its homeostatic
functions as regulation of
Blood flow
Energy metabolism
Reproduction
Threat responses
Neurotransmission"
Transmission in final synapse onto muscle
and glands mediated by Noradrenaline +
Acetylcholine
Sympathetic = Noradrenaline
Parasympathetic = Ach
These chemicals have opposing effects on
smooth muscle e.g contraction vs.
relaxation of smooth muscle
Noradrenergic receptors"
Receptor subtypes allow for coordinated control of different
groups of sympathetic responses
Cholinergic receptors"
Same is true for Ach for parasympathetic
Regulation of cardiac function"
To regulate
provision of O2 to
∆ tissues under
many∆ conditions
Mechanical Barosensory
information about
pressure
Chemosensory
information about O2
levels
Determines balance
of parasymp + symp
Cardiac Receptors"
Chemoreceptors in
specialised Carotid
bodies
Baroreceptors
in Heart + major
vessels
Cardiac reflex"
Reflex
coordinated
by Nucleus
of solitary
tract
Rise in Blood
Pressure
- Inhibit sympathetic
+ Excite parasymp
+
+
-
Control of bladder"
Higher
integrative
centres for
decision
making
afferent
Control of bladder"
Governed by integration of
visceral sensory info, emotional,
social, contextual cues
Bladder emptying achieved by
coordinated activation of sacral
parasympathetic + inactivation of
somatic motor
Sample questions"
Essays:
How does the visceral motor system control the body for
challenging and quiescent states?
Describe the three main divisions of the visceral motor system and
how they interact.
Multiple choice:
Enteric nervous system is part of the… visceral motor system
Sympathetic nervous system uses… noradrenaline
Baroreceptors in the heart are sensitive to… arterial pressure
Next lecture"
Association cortices –
chapter 26