Central Nervous SystemThe Autonomic Nervous System

Nervous System

• coordinates the actions of the body• transmits signals between different parts of

the body

Sensory input – gathering information

monitor changes occurring inside and outside the body stimuli

Integration – process and interpret

sensory input

+/- action

Motor output

= response to integrated stimuli

activates muscles/ glands

Nervous System

Central Nervous System

MOTORSENSORY

SOMATIC NERVOUS SYSTEM

AUTONOMIC NERVOUS SYSTEM

Sympathetic

Parasympathetic

Enteric Nervous System

Periferic Nervous System

Autonomic Nervous Systeminvoluntary – automatic – visceral/glands motor system

MOTORSENSORY

AUTONOMIC NERVOUS SYSTEM

Sympathetic

Parasympathetic

Enteric Nervous System

Somatic vs. Autonomic

Effectors (Targets)

skeletal muscle smooth/cardiac muscle & glands

Efferent pathways

1 neuron - myelinated axon from ventral horn of spinal cord all the way to effector

2 neuron pathway – 1st - preganglionic and body resides in brainstem/S2-S4 cord – myelinated axon; 2nd - postganglionic and body resides in autonomic ganglion – unmyelinated axon

SNS = short pre/long post ganglionic axonPsNS = long pre/short post ganglionic axon

Somatic vs. Autonomic

Neurotransmitters somatic vs. autonomic

All motor neurons release Ach - always stimulatory

All preganglionic fibers release Achpostganglionic PsNS fibers release Achpostganglionic SNS fibers release Norepinephrine

→ stimulatory or inhibitory (based on receptor types)

http://health-7.com/Lippincotts%20Illustrated%20Reviews%20Pharmacology/3.%20The%20Autonomic%20Nervous%20System/8

Divisions of the ANS

Parasymathetic NS

- usually inhibitory

=> conservation of energy

Sympathetic NS - usually stimulatory => energy consum

• dual innervation• opposing effects• may work independently • may work together - each

one controlling one stage of the process

Sympathetic nervous systemThe “fight-or-flight” system:

involves activities like: other activities are reduced exercise, excitement, (GI/urinary) emergency and embarrassment Þ ↑ flow to muscle => ↓ blood flow to the organs

heart rate ↑ - breathing ↑rapid and deepbronchioles dilate - ↑ventilation => delivering more oxygen to cellsthe skin is cold and sweatythe pupils dilateliver releases more glucose into circulationlipolysis to the level of the adipocytes

Sympathetic nervous system

• Cervical-thoraco-lumbar division

• Short preggl/long postggl

Adrenal medulla

• same embryological origin as the sympathetic ganglia

• fibers from the thoracic splanchnic nerves

pass thru the Celiac Ganglion

↓

terminate in

the medullary adrenal gland

=> secrete epi- and norepinephrine into the blood

Barwick et al. - Embryology of the adrenal glands and its relevance to diagnostic imaging, Clin Rad, 2005, Vol. 60, Issue 9, pag: 953-959

Parasympathetic nervous system

• active in non-stressful situations – keep the body energy

=> involves activities like:

salivation, lacrimation, digestion,

defecation,urination• Activats lens accommodation - close vision

- ↑ gastrointestinal tract activity- ↓ heart rate, blood pressure- ↓ respiratory rates- constricted pupils

- warm skin

Parasympathetic nervous system

• Fibers emerge from CR.NN. - III,VII,IX, X S2-S4 spinal cord

• Long preganglionic fibers synapse in terminal or intramural ganglia

• a complex, independent nervous system

lines the gastrointestinal tract

“second brain” “the brain of the gut”

► motility

controls essential functions ► secretion

► blood flow

Enteric Nervous System

ENS

Furness JB (2006) The Enteric Nervous System. Blackwell, Oxford, pp 274

Connections CNS - ENS

ANS: Sympathetic & Parasympathetic

The neural connections between the ENS and CNS, and neural connections between gastrointestinal organs

Furness, JB – The enteric nervous system and neurogastroenterology, Nat Rev Gastroenterol. Hepatol, doi: 10.1038/nrgastro. 2012.32

The digestive system contains full reflex circuits of the ENS (motor neurons and interneurons in blue, sensory neurons in purple). Pathways from the gastrointestinal tract project outwards, via intestinofugal neurons (red), to the CNS (neurons in yellow), sympathetic ganglia, gallbladder and pancreas. Neurons in sympathetic prevertebral ganglia (green) receive both CNS and ENS inputs. Sensory information goes both to the ENS, via intrinsic primary afferent (sensory) neurons (purple) and to the CNS via extrinsic primary afferent neurons (also purple) that follow spinal and vagal afferent routes. Pathways from the CNS reach the ENS and gastrointestinal effector tissues through vagal, sympathetic and pelvic pathways. Abbreviations: CNS, central nervous system; ENS, enteric nervous system.

Grant’s Atlas 12 2009

Maps of Referred Pain

Visceral afferents and referred pain

Referred pain

• visceral pain afferents travel the same path as somatic pain afferents

• sometimes - pain stimuli from viscera is interpreted as somatic pain origin by the brain

Eg - heart attack (T1-T5 supply chest & medial aspect of left arm)

CNS processing and modulation of visceral

sensation

Van Oudenhove L, Demittenaere K., Tack J, Aziz Q – Central nervous system involvement in functional gastrointestinal disorders, 2004, Best Pract & Research Cl Gastroentero, Vol 18, pag 663-680

PAG, periaqueductal gray; PB, parabrachial nucleus of the dorsolateral pons; AMYG, amygdala; HT, hypothalamus; Vmpo, MDvc & VPL, thalamic nuclei (ventromedial part of the posterior nuclear complex, ventrocaudal part of the medial dorsal nucleus and ventroposterior lateral nucleus respectively); ACC, anterior cingulate cortex; PCC, posterior cingulate cortex; PF, prefrontal cortex; SMA, supplementary motor area; S1 & S2, primary & secondary somatosensory cortices; M1, primary motor cortex; PPC, posterior parietal complex.

Pain sensation → sensory discriminatory componentsPain affect → combination of emotional and cognitive appraisals related to the pain experience

Levels of ANS Control

• hypothalamus = the main integration center of ANS activity

• subconscious cerebral input - via limbic system - influences hypothalamic function

• other controls come from: - the cerebral cortex

- the reticular formation - the spinal cord

Hypothalamic Control

• centers of the hypothalamus control:– heart activity and blood pressure– body temperature– water balance– endocrine activity– emotional stages (rage, pleasure) – biological drives (hunger, thirst, sex)– reactions to fear and the “fight-or-flight” system.

http://www.upright-health.com/pituitary-gland.html

Superior nervous structures involve in control of ANS: PAG

Hamann S – Affective neuroscience – Amygadala’s role in Experiencing Fear, 2011, Current Biol, Vol 21, R75-R77

Superior nervous structures involve in control of ANS: Amygdala

EMS (Emotional Motor System) – amygdala - hypothalamus - periaquaductal grey

Integrates: - autonomic - neuroendocrine - pain modulatory responses

EMS = neurobiological basis of stress sensitivity

http://brainmind.com/BrainLecture5.html