Autonomic Nervous System
responsible for controllling bodily functions that are largely involuntary, or automatic, in a nature.
What functions ANS do
Autonomic Nervous System
Functions of ANS
Control of BP, and other CVS functions, digestion, elimination, and thermoregulation.
Anatomy of the ANS:
* Two areas: Sympathetic and Parasympathetic
Parasympathetic or Craniosacral
Composed of neurons originating in the midbrain, brainstem, and sacral region of the spinal cord.
Enteric nervous system
Third ANS division -Comprised of GI tract that controls various aspects of GI function. IT has both Sypathetic and parasympathetic components.
Sympathetic nervous system
thoracolumbar- Arises from thoracic and upper lumbar regions of the spinal cord.
Arise from:Intermediolateral gray columns of the thoracis and upper lumbar spinal cord , Leave Spinal Cord: via ventral root of the spinal nerve, End in: sympathetic ganglion
Located in three areas:1)Chain ganglia/Paravertebral: both side of vertebral Column 2) Unpaired prevertebral ganglia: anterior to aorta 3) Terminal ganglia: in the tissue that is innervated - bladder and rectum
Ratio of preganglionic to post ganglionic fibres
1:15 to 1:20
Route of Sympathetic
PreGanglioninc Fibre-arise-end in sympathetic ganglia-meet post ganglion or more ganglion - leaves to the effector tissue that it supplies (heart, sweat gland etc)
Origin: Midbrain-brainstem (cranial portion) or Sacrall region of Spinal cord
Exit: CNS via cranial nerves- 3,7,9,10
Vagus nerve - cranial nerve 10
comprises of 75% of the efferent component of entire parasympathetic division
Function of Sympathetic and Parasympathetic
Organ innervated by both systems
physiological antagonism typically exists between these two divisions - both divisions innervate the tissue, one division increases function and the other decreases activity.
Sympathetic: to mobilize body energy and Parasympathetic: tends to conserve and store the energy.
Cause: increased cardiac output, decreased visceral blood flow(leave more blood available for skeletal muscle), increased cellular metabolism, several other physiological changes that facilitate vigorous activity.
opposite effect. Slows down heart rate, bring changes that encourage inactivity. Increase intestinal digestion, absorption, an activity thta stores energy for future needs.
Synthesizes and secretes (20%)norepinephrine and (80%) epinephrine directly into blood stream.
Increases Cardiac function and cellular metabolism Because higher affinity for certain receptors: Epi more readily binds to beta subtype of adrenergic receptors.
Where they release
In stress situation: Release directly into blood stream to reach everywhere
Autonomic Integration and Control
Homeostatic control of BP, Thermoregulation, GI function
Reflexes are based on strategies
Peripheral sensor- Monitors the change in a particular syste- inforation goes to CNS- integration of information- adjustment is made in the autonomic discharge in specific tissu/organ- alter activity to return physiological function back to normal level
Baro receptors location
neck and large arteries of thorax
Thermo receptors location
skin, viscera, hypothalamus
Controll of - body temperature, water balance, energy metabolism
Higher involvement of the ANS
cortex, limbic system, brainstem
Acetylcholine (Ach) and Norepinephrine (NorEpi)
Important Neurotransmitters of ANS
Synapse 1: Between Pre-post ganglionic neurons-Sympatheticdivision
Synapse 2: Synapse 1: Between Pre-post ganglionic neurons-ParaSympatheticdivision
Synapse 4: Parasympathetic-Postganglionic - Effector cell synapse
Synapse 3: Sympathetic postganglionic neuron - effector cell
Preganglionic and Parasympathetic postganglionic neurons - because Ach
Most sympathetic postganglionic neurons
Some sympathetic post ganglionic use -Ach, as neurotransmitter. - innervate in sweat glands and certain blood vessels in face, neck, and lower extremities.
Other Neurotransmitters / Contratransmitters
Adenosine and Adinosine Triphosphate : possible transmission in the GI tract, CVS, other organs
Neuropeptide Y, Vasoactive intestinal polypeptide, Calcitonin gene related peptide, orexin, cholecystokinin, and angiostenin II, --- Control of the organs and systems
to regulate peripheral autonomic responses and CNS autonomic activity.
Located at : acytylcholine synapses,
Located at: norepinephrine synapses
ACH---> Cholinergic Receptor ---> 1) Muscurinic 2) Nicotinic
Norepinephrine NE---> Adrenergic Receptor ---> 1)Alpha -> alpha1, alpha2 and, 2) Beta -> beta-1,beta-2
Located: Junction between preganglionic and postganglionic neurons in both sympathetic and parasympathetic pathways
Effects: both divisions of ANS
Type 1 Nicotinic
Means: Located at ANS (Nn)
Type 2 Nicotinic
Means: Located at skeletal neuronmuscular junction (Nm)
Located: all of the synapses between cholinergic postganglionic neurons and the terminal effector cell, including all the parasympathetic terminal synapses and the sympathetic postganglionic cholinergic fibers that supply sweat glands and some specialized blood vessels.
Subtypes of Muscurinic
M1, M2, M3, M4, M5 : Based on their characteristics (chemical and structural)
M1, M4, M5
bladder detrouser muscle and to control pancreatic insulin release, and other peripheral metabolic responses
Adrenergic Receptors (Alpha)
Located at: Smooth muscle- in various tissues thorughout the body
Subtypes of Alpha 1
Alpha 1A, Alpha 1B, Alpha 1D
Alpha 2 or Autoreceptors
Located at: Presynaptic termnal of certain adrenergic synapses
Alpha 2 work
decrease the release of norepinephrine and other chemicals. : overall serve as negative feedback that limits the amount of neurotransmitter released from the presynaptic terminal.
Alpha 2 Stimulation
Cause: Decreased neurotransmitter release and diminished stimulation of the interneurons that influence the alpha motor neurons.
Alpha 2 Stimuants
Agonists - tizanidine, -- decrease neuronal excitability in the spinal cord and so, decrease muscle hyperexcitability in spasticity conditions.
Subtypes of alpha 2
Alpha-2A, alpha- 2B, alpha-2C
Adrenergic Receptors (Beta)
heart and kidneys
located: smooth muscle of certain vasculatures, the bronchioles, the gallbladder, and the uterus
functional role in some tissues. Located at: Adipose tissue