Regulation of the Visceral Function by the Nervous System

1
Section 5 Regulation of the Visceral Function by
the Nervous System
2
I Autonomic Nervous System1. Basic of the
Anatomy
3
ANS

• We subdivide the ANS into the parasympathetic,
  sympathetic, and enteric divisions.
• The enteric system is essentially an independent
  nervous system responsible for regulation of
  digestive functions.
• The ANS coordinates cardiovascular, respiratory,
  digestive, excretory and reproductive systems.

4
Somatic and Autonomic Nervous System
5
Somatic and Autonomic Nervous System

• Autonomic
• Smooth and cardiac muscle and glands
• Unconscious regulation
• Target tissues stimulated or inhibited
• Two synapses
• Acetycholine by preganglionic neurons and ACh or
  norepinephrine by postganglionic neurons

• Somatic
• Skeletal muscle
• Conscious and unconscious movement
• Skeletal muscle contracts
• One synapse
• Acetylcholine

6
Sympathetic Division

• Preganglionic cell bodies in lateral horns of
  spinal cord T1-L2

7
Parasympathetic Division

• Preganglionic cell bodies in nuclei of brainstem
  or lateral parts of spinal cord gray matter from
  S2-S4
• Preganglionic axons from brain pass to ganglia
  through cranial nerves
• Preganglionic axons from sacral region pass
  through pelvic nerves to ganglia

• Preganglionic axons pass to terminal ganglia
  within wall of or near organ innervated

8
Parasympathetic and sympathetic nerve distribution
9
2. Neurotransmitters and Neuroreceptors

• Acetylcholine and Norepinephrine
• All preganglionic neurons are cholinergic
• Parasympathetic post ganglionic neurons are
  cholinergic
• Sympathetic post ganglionic neurons are
  adrenergic except
• Sympathetics innervating sweat glands, blood
  vessels in skeletal muscle, and piloerection
  muscles are cholinergic

10
Neurotransmitters
11
Acetylcholine

• Nicotinic receptors
• Nm (muscular-type or N2) skeletal muscle
• Nn (neuron-type, or N1) autonomic ganglia, CNS
• Muscarinic receptors
• Postganglionic parasympathetic and a few
  sympathetic sites, CNS (also autonomic gang.)
• Receptor subtypes M1-5

12
Catecholamines

• Norepinephrine
• Postganglionic sympathetic, CNS, adrenal medulla
• Receptors a1, a2, b1
• Epinephrine
• Adrenal medulla, CNS
• Receptors a1, a2, b1 , b2
• Dopamine
• Autonomic ganglia, CNS
• Receptors D(1-5), a1, b1

13
Location of ANS Receptors
14
3 Function of the Sympathetic and Parasympathetic
Nerve
15
SNS

• Sympathetic nervous system prototypically fight
  or flight.
• Associated with increased
• energy expenditure,
• cardiopulmonary adjustments for intense activity,
  
• blood flow adjustments for maximum energy
  expenditure.

16
SNS - Fight Flight Reaction

• Youre walking alone at night and all the sudden
  you hear an unfamiliar noise near by In a matter
  of seconds,
• your heart rate increases dramatically,
• blood vessels in your skeletal muscles dilate,
• blood vessels in the visceral muscles constrict,
• digestion is ceased,
• your liver ramps up glucose release,
• your pupils dilate,
• salivary production decreases,
• sweat increases.

17
Parasympathetic Nervous System

• If that noise turns out to be the result of wind,
  then the body is returned to pre-noise state.
• This is the job of the parasympathetic nervous
  system.

18
Autonomic Nervous System

• Parasympathicus
• Wind down, relaxation, digestion
• Dominated by Acetylcholine

• Sympathicus
• Fight Flight Reaction
• Dominated by Noradrenaline (Adrenaline)
• Fear, exercise, rage

19
Interactions of the ANS

• Most visceral organs are innervated by both types
  of nerves.
• Most blood vessels are innervated only by
  sympathetic nerves.
• PS activity dominates the heart and GI tract.
• Activation of the sympathetic division causes
  wide spread, long-lasting mobilization of the
  fight-or-flight response.
• PS effects are highly localized and short lived.

20
II. Central Regulation of Visceral Function
1. Spinal cord ? bladder and rectum reflex
(micturition and defecation) ? the baroreceptor
reflex, ? sweating of the skin  
21
2. Medulla oblongata ? Vital (respiratory and
cardiovascular) center ? Other autonomic
reflexes Swallow, cough, sneeze, gag, and vomit.
22
 3. Hypothalamus
Tu 19.17
23
Hypothalamic Functions

• 1). Body temperature
• heat loss center in anterior HT (preoptic area)
• stimulates sweating and peripheral vasodilation,
• lesions cause hyperthermia
• heat gain center in posterior HT
• stimulates cutaneous vasoconstriction,
  piloerection, shivering
• lesions cause poikilothermy
• (the difference between poikilothermal or
  cold-blooded animal and homoiothermal or
  warm-blooded animal)

24
Hypothalamic Functions

• 2). Food intake
• ventromedial and paraventricular nuclei are
  satiety centers,
• lesion causes obesity
• lateral HT (feeding center) stimulates food and
  water intake

25
Hypothalamus Functions

• 3) Water balance
• ADH (vasopressin)
• Osmotic pressure in hypothalamus Thirst - Drink

26

• 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

27
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

28
Hypothalamus Functions

• 6). Circadian
• Almost all land animals coordinate their behavior
  according to circadian rhythms, the daily cycles
  of lightness and darkness that result from the
  spin of the earth.
• Most if not all living organisms have rhythmic
  fluctuation in bodily function that are about 24
  hs in length. (sleep-wake, and body temperature
  cycles).
• Suprachiasmatic muclei (SCN)

29
Circadian rhythms of physiological functions.
30
Hypothalamus Functions
7) Regulation of the Endocrine Function
31
4 Influence of Brain on Autonomic Functions
32
III Function of Sympathetic and Parasympathetic
nerve on the target organs
33
Physiology (Table 5-1)
Cornea
Iris
Lens
Eye
Ciliary muscle
34
Atria
Heart
SA node
AV node
Ventricles
35

36

Blood vessels
37
Lungs and salivary glands
38
Gastrointestinal tract and liver