Transcript 13 Central regulation of autonomic functions

Central regulation of
autonomic functions
Levels of ANS Control
Figure 14.9
4 Influence of Brain on
Autonomic Functions
Central Regulation of Visceral Function
1. Spinal cord
 bladder and rectum reflex (micturition and
defecation)
sexual reflex
the baroreceptor reflex
sweating of the skin
Reflex control of micturition
Bladder filling facilitated by tonic
neural activity:
• sympathetics – inhibits bladder
contraction
• sacral somatic motor nerves –
contracts external sphincter
Bladder filling activates
Mechanoreceptors
Voiding (micturition):
threshold reached
• sympathetic and somatic motor
neurons inhibited
• parasympathetic outflow to
detrusor m. activated
• bladder smooth muscle contracts
Neural Control of Defecation.

Filling of the rectum with feces stimulates stretch
receptors, which transmit impulses to the spinal
cord. A spinal reflex stimulates contractions of the
rectum and relaxation of the internal anal sphincter.
Defecation normally does not occur unless voluntary
impulses relax the external anal sphincter.
2. Medulla oblongata
 Vital (respiratory and cardiovascular) center:
 Other autonomic reflexes: Swallow, cough, sneeze,
gag, and vomit.
3. Hypothalamus
Tu :19.17
Hypothalamic Control

Centers of the hypothalamus control:
 Heart activity and blood pressure
 Body temperature, water balance, and endocrine
activity
 Emotional stages (rage, pleasure) and biological
drives (hunger, thirst, sex)
 Reactions to fear and the “fight-or-flight” system
Hypothalamic Functions
2). Food intake:
ventromedial and paraventricular nuclei are satiety
centers,
lesion causes obesity;
lateral HT (feeding center) stimulates food and water
intake
Hypothalamus Functions
3) Water balance
ADH (vasopressin)
Osmotic pressure in hypothalamus – Thirst - Drink
4) Sleep/wake cycle:
suprachiasmatic nuc is biological clock;
preoptic nuc. can initiate sleep;
lat HT can change cortical arousal;
post HT lesion can cause coma or impaired arousal
Hypothalamus Functions
5). Emotions and behavior:

ventromedial lesions can cause viciousness/rage

Posterior HT stimulates sympathetic functions

Anterior HT stimulates parasympathetic functions

Mamillary nuclei: recent memory
Circadian
rhythms of
physiological
functions.
Central control of the
Autonomic NS
Amygdala: main limbic
region for emotions
-Stimulates sympathetic
activity, especially
previously learned fearrelated behavior
-Can be voluntary when
decide to recall frightful
experience - cerebral cortex
acts through amygdala
-Some people can regulate
some autonomic activities
by gaining extraordinary
control over their emotions
Hypothalamus: main
integration center
Reticular formation:
most direct influence
over autonomic
function
Visceral Reflexes
The
visceral sensory neurons are the
first link in the autonomic reflexes
These neurons send information
concerning chemical changes, stretch,
and irritation of the viscera
Visceral Reflexes
 Visceral
reflex arcs have essentially the same
components as somatic reflex arcs
 Receptor
 Sensory neuron
 Integration center
 Motor neuron
 Effector
Visceral Reflexes

Visceral reflex arcs differ in that they have a twoneuron chain
Autonomic Reflexes
Visceral Reflexes
 Additional
cutaneous areas to
which visceral
pain is referred
Autonomic reflexes



a) viscero-visceral
b) viscero-dermal (viscero-somatic)
c) dermato-visceral (somato-visceral)
Cornea
Iris
Lens
Eye
Effector
Radial
muscle
Sphinctor
Ciliary
muscle
Ciliary
muscle
Sympathetic
Parasympathetic
Contraction
—
(mydriasis, 1)
—
Contraction
(miosis)
Slight relaxa- Contraction (near
tion (2)
vision)
Effector
SA node
Atria
AV node
Ventricles
Sympathetic
Tachycardia
(1,2)
contractility
and conduction
(1,2)
conduction
and automaticity (1,2)
contractility,
conduction, and
automaticity
(1,2,1)
Parasympathetic
Bradycardia
contractility,
conduction
(usually)
conduction
—
Blood vessels
Effector
Skin and
mucosa
Skeletal
muscle
Salivary
glands
Erectile
tissue
Sympathetic
Constriction
(1,2)
Constriction
(), dilation
(2)
Constriction
(1,2)
Constriction
()
Parasympathetic
Dilation (?)
—
Dilation
Dilation
Lungs and salivary glands
Effector
Bronchial
sm. musc.
Bronchial
glands
Salivary
glands
Sympathetic
Parasympathetic
Relaxation (2) Constriction
(1),(2),
secretion
Viscous,
amylase
secretion
(1,1,2)
secretion
Profuse watery
secretion
Gastrointestinal tract and liver
Effector
Smooth
muscle
Sympathetic
Parasympathetic
motility and motility and
tone
tone
(1,2,1,2)
Sphincters Contraction
Relaxation
(1)
Secretions secretion (2) secretion
Liver
Glycogenolysis, Glycogen
gluconeogene- synthesis
sis (1,2)
•
•
afferent input integrated
in CNS centers
impacts autonomic
efferent outflow
EXAMPLE:
• blood pressure falls
• sinus nerve activity falls
•
sympathetic outflow increases to the:
vasculature – vasoconstriction
heart – increased cardiac output
adrenal medulla – increased epinephrine
release
Reflex control of GI function
•
smell, taste of food and/or foods in
the stomach
LOCATION OF SENSORY
STRUCTURES?
•
central integration
•
reflex parasympathetic efferent
stimulation which leads to:
increased motor activity (stomach,
gallbladder and intestine)
increased secretory activity
(stomach and pancreas)
Fight or flight response
This is a coordinated, massive increase in sympathetic outflow to all target
organs in response to fear, stress, or exercise. Parasympathetic outflow
ceases.
The coordinated physiologic response is a survival mechanism which
includes:
•
•
•
•
•
•
Increased heart rate, cardiac output, and blood pressure
Contraction of the spleen to mobilize blood cells
Bronchial dilation
Decreased GI activity
Liberation of glucose into the bloodstream
Inhibition of insulin secretion
However, under normal non-stressful situations, autonomic efferent outflow
is more discrete. Autonomic reflexes play an important role in regulating
physiologic function.