BVMS1

• control of involuntary activities
• cardiovascular responses
• respiration
• endocrine secretion
• gastrointestinal motility and secretions
• reproductive and urogenital control

limbic cortex--> spinal cord, brain stem, hypothalamus---> AMS--->sympathetic or parasympathetic

• receptors
• Afferent pathways (using visceral and somatic nerves)
• dorsal root ganglion
• CNS
• efferent pathway
• paraveterbral (sympathetic)
• prevetebral (sympathetic)
• pre-ganglionic (parasympathetic)
• post-ganglionic (parasympathetic)

• each lower motor pathway has 2 neurones to organs
• 1) short finely myelinated PRE-GANGLIONIC fibres leave with notor roots of spinal nerves
• 2) LONG POST-GANGLIONIC fibres pass to organs
• (see image)

• Each lower motor pathway has 2 neurones to organs
• 1) long finely myelinated PRE-GANGLIONIC fibres leave w/ the cranial nerves
• 2) Short non-myelinated POST-GANGLIONIC fibres pass to organs
• (75% via vagus nerve (cranial X)
• more localized effect than sympathetic

• Parasympathetic NS: cholinergic/Ach/Cholinergic/Ach
• Ach removed from synapses by cleavage (achase) and reuptake
• Sympathetic NS: Cholinergic/ach/Adrenergic (most)/NA
• NA removed by reuptake, diffusion, enzymatic destruction (monoamine oxidase, catechol-O-methyl transferase)

• Ach--> nicotinic receptor-->Ach--> muscarinic receptor
• increased exocrine gland secretion
• increased GI smooth muscle contraction, decreased heart rate

• Ach-->N-->ach-->M
• (increase sweating, dilate skeletal muscle blood vessels)
• Ach-->N (Adrenal medulla)--> A, NA via blood
• Ach-->N---> NA---> alpha or Beta
• (increased slenic contraction, increased cardiac efficiency, decreased contraction of GI smooth muscle, constrict peripheral blood vessels, dilate airways)

somatic NS--> Ach--> N (skeletal muscle)

• Nicotinic (Nn, Nm)
• Muscarinic (M1, M2, M3, M4, M5)
• adrenoreceptors (alpha (a1[a1a, a1b, a1d], a2 [a2a, a2b, a2c]), Beta (B1, B2, B3, B4)

• secretes:
• Noradrenaline (20%)
• Adrenaline (80%)
• longer effect than neural stimulation, as NA/A not degraded as quickly
• (acts on a & B receptors)
• Adrenaline, generally has the same effects as NA but...
• greater effect at B receptors, increase effect on heart rate, decrease effect on vascular in muscle
• adrenaline has 5-10x effect of NA on metabolism adrenaline can double metabolic rate
• why!?= parallel system (saftey), metabolic regulation is non innervated organs

• both divisions of the ANS are continually active
• basal rate- tone
• adrenal gland cont. secretes low levels of NA and A- adrenal tone

• transmitters released from nerve terminals other than Ach and noradrenaline
• non-peptides (ATP, GABA....)
• peptides
• ex: ATP is released from postganglionic sympathetic nerve terminals in conjunction with noradrenaline

• Cardiovascular: several reflexes
• Baroreceptor reflex: pressure- monitored by receptors in major arteries, signal sent to brainstem- changes sympathetic impulses to heart and blood vessels
• Bladder reflex- stretch- impulses to sacral cord contration of bladder and relaxation of sphincter
• sexual reflex- psychological and physical stimulation- activation of Parasympathetic NS- erection, stimulation of the glans penis- activation of sympathetic NS- ejaculation

• same effect as Sympathetic stimulation
• Noradrenaline
• adrenaline (a & B- cardiac arrest, anaphylaxis)
• Dopamine- effects dependent upon dose, due to ability to interact w/ different receptor subtypes
• isoprenaline- non selective B adrenergic agonist- chronotropic/inotropic actions (does not bind with a)
• phenylpropanolamine- a adrenergic agonist- urinary incontinence in dogs (does not bind to B)
• ephedrine- induces the release or noradrenaline (therefore non-selective)
• usualy used in emergency situations

• Dobutamine- B1, agonist- chronotropic/inotropic cardiac effects
• Clenbuterol- B2, agonist- bronchodilater
• Phenylephtine- a1, agonist- vasocontriction
• Clonidine- a2, agonist- Central sedative effect

• block the effects of sympathetic stimulation
• phenoxybenzamine- a1, irreversible antagonist- laminitis and urinary retention
• Yohimbine- a2, antagonist- reverse sedation
• metoprolol- B1 antagonist- cardiac effect
• propranodol- mixed B antagonist

• same effect as parasympathetic stimulation
• Acteylcholine- rapid broken down
• Methacholine- M>N- cardiovascular system
• Carbochol- M receptors in GI- Glaucoma
• Pilocarpine- M effects- Glaucoma

• Prolong/ increase effects as parasympathetic stim.
• Reversible: Phytostigmine, Neostigmine (reversal agent for non depolarising muscle relaxants. myasthenia gravis)
• Irreversible: organophosphates (parathion, malathion)

• muscarinic antagonists: Atropine (prevents salivation. antidote for OP poisoning), Hyoscine (antiemetic)
• Nicotinic antagonists: N receprots are present at autonomic ganglia and muscle end plate but different subtypes at each location. therefore targeted tx is important.
• non depolarising- Curare, Atracurium
• Depolarising- suxamethonium

• system of neurones contained w/in the gut begin in the esophagus and end at anus
• control GI function movement and secretion
• contains 100 milliion neurones= spinal cord!

• regulates movement
• tonic contraction of gut wall
• intensity of rhythmical contractions
• rate of rhythmical contractions
• speed of peristaltic waves

• absorption
• secrection

• lots!
• Ach, NA, ATP, seratonin, Dopamine substance P, VIP, Somatostatin the specific functions of which are not known!

• Post gangionic fibres of the Parasympathetic (activated) incorporated into myenteric and submucosal
• stimulation increases activity of the enteric
• Cell bodies of post ganglionic sympathetic fibres present w/in the prevertebral ganglia, fibres terminate on both GI smooth muscle and enteric NS
• Stimulation decreases activity of the enteric (sympathetic)

• W/in the enteric (GI secretions, peristalsis)
• GI/prevertebral/GI (gastrocholic- signal from the stomach causes evacuation of the colon) (Enterogastric- signal from the colon and small intestine to inhibit stomach motility and secretion)
• GI/Spinal cord-brain stem/GI (control of gastric motor and secretory activity via signals generated in the stomach and duodenum, pain reflexes- inhibit entire tract, defecation reflexes)