Nervous System 2 b Chapter 11 Autonomic Nervous

Nervous System 2 b Chapter 11

Autonomic Nervous System • A division of the peripheral nervous system • Remember: the sympathetic nervous system is associated with the “bear” • The parasympathetic nervous system is associated with the “book”

Sympathetic NS Parasympathetic NS Originates in the cranial thoracolumbar egments nerves and sacral of the spinal cord segments of the cord (Thoracolumbar system) (craniosacral system) Synapses in ganglia near the spinal cord Synapses in ganglia near the visceral effector Synapses with neurons to several organs Synapses with neurons to a single organ Effect is widespread Effect is local

Sympathetic NS Fight or flight Parasympathetic NS Maintenance functions: feed and breed Preganglionic fibers release ACh (cholinergic) Postganglionic fibers release norepinephrine Postganglionic fibers (adrenergic) release Acetylcholine Receptors are 1, 2, β 1, β 2 Receptors are nicotinic and muscarinic

• Notice: even though it is small in the previous slide – the adrenal gland is innervated by the sympathetic nervous system. When the sympathetic nervous system is activated, it causes norepinephrine and epinephrine to be released from the adrenal medulla into the blood stream. It takes about 20 minutes for these hormones, which mimic the effects of the sympathetic nervous system, to be inactivated.

Cranial Nerves • Part of the peripheral N. S. • Twelve pairs • Designated by Roman Numerals I – Olfactory – sensory nerve that functions in the sense of smell II – Optic nerve – arises from the retina of the eye and functions in vision III – Oculomotor – mostly motor function – most of the muscles of the eye, eyelid, and pupillary constriction

• IV – Trochlear – moves the superior oblique muscle of the eye that passes through a ring of tissue called the trochlea • V – Trigeminal – three branches – motorchewing; sensory – skin of the face • VI – Abducens – lateral rectus eye muscle – abducts the eye • VII – Facial nerve – motor to muscles of facial expression and secretion of saliva and tears; sensory – taste and proprioception

• VIII –vestibulococholear – sensory –hearing and equilibrium (balance) • IX – Glossopharyngeal – motor- secretion of saliva; sensory – taste, regulation of blood pressure, and proprioception of muscles involved in swallowing • X – Vagus – “the wanderer” - motor- smooth muscle contraction and relaxation, secretion of digestive fluids; heart, lungs – parasympathetic innervation; sensory from visceral organs it supplies and proprioception.

• XI – Accessory nerve – motor: swallowing and movements of the head Sensory - proprioception • XII – Hypoglossal – motor- movement of tongue during speech and swallowing sensory- proprioception

One more thing…. . • The blood supply to the brain has many alternate pathways, or anastomoses. The blood vessels that supply the brain, the vertebral arteries and the internal carotid arteries, form branches and link at the base of the brain in a structure called the Circle of Willis. This means that if a blood clot blocks the flow of blood through one pathway, that area of the brain can still be supplied through an alternate vessel.