ANS Lecture Flashcards
ANS
Part of the nervous system that controls the involuntary activity in the body (smooth muscle, cardiac muscle, glandular tissue).
Central control centers of ANS
Brain and brainstem
Peripheral system:motor system
In peripheral system, the motor system directly supplies target tissues.
Involves sympathetic nervous system and parasympathetic nervous system. They often have reciprocal innervation (counter effects)
Visceral afferents
Sensory neurons that supply target tissues of ANS (smooth muscle. cardiac muscle, glandular tissue) but are NOT considered to be a part of ANS by most individuals.
Sensory axons often travel along same route as the sympathetic and parasympathetic nerve axons.
Examples of ANS effects
Sympathetic stimulations and parasympathetic stimulation often have counteractve effects.
Ex=Pupil dilation (sympathetic)
Pupil constriction (parasympathetic)Special ANS effect with blood vessels
Sympathetic stimulation can cause constriction (alpha receptors) AND dilation (beta receptors) in BLOOD VESSELS.
Sympathetic nervous system origin
Thoracolumbar spinal cord (T1-L4)
Parasympathetic nervous system origin
Sacral spinal cord and brainstem
Somatic efferents vs Visceral efferents (ANS)
Somatic efferents- CNS is directly connected to target muscle through 1 motor neuron (skeletal muscle is good example)
Visceral efferent- like a “relay race”. Long preganglionic axon extends from CNS to a ganglia which communicates with postganglionic axon that will communicate with target tissue.
Cell bodies of preganglionic neurons of sympathetic and parasympathetic nervous system found where
CNS
Sympathetic: thoracolumbar spinal cord (T1-L4)
Parasympathetic: sacral spinal cord and brain stem (CNN 3, 7, 9, 10)
Explain preganglionic/postganglionic relay
Axon of pregang neuron travels in a peripheral nerve (spinal or cranial nerve) to synape on a specific postgang nerve. The axon of postgang neuron travels in a peripheral nerve to synape to specific target tissue to inhibit or stimulate target tissue.
Ganglia
Collection of neuronal cell bodies found outside CNS.
ANS ganglia
Postgang neurons are found in ganglia
Note, not all ganglia are associated with ANS
Sympathetic nervous system ganglia
Most are visible in gross dissection (head, thorax, abdomen, pelvis)
- ->paravertebral (beside vertebral column)
- ->prevertebral (further away from vertebral column)
Sympathetic ganglia need to ID in lab
Middle cervical ganglion
Cervicothoracic ganglion
Sympathetic trunk ganglion
Part of the sympathetic trunk
Cervical, thoracic, lumbar, sacral
ANS bilateral or unilateral
Bilateral. On left and right side of the body
Parasympathetic length of axons and ganglia
Pregangs are long
Postgangs are short and right next to tissue its going to innervate
Ganglia are at or in wall of target organ
Crainial nerve X functions
Vagus nerve
ANS-parasympathetic
Sensory from viscera to brain (accounts for 80% of axons in the vagus nerve)
Motor to skeletal muscles of the larynx via recurrent laryngeal nerve
Vagus nerve orientation
Vagus nerve starts out (from tympano occipital fissure) following the vagosympathetic trunk on L and R side
Vagus nerve leaves trunk around middle cervical ganglia
Vagus nerve splits into dorsal and ventral branches on L and R side
Dorsal and ventral vagal branches from each side unite to give a singular dorsal trunk and a singular ventral trunk
The single ventral and single dorsal trunk will pass through diaphragm with the esophagus to supply abdominal organs.
Sympathetic trunk
Runs lateral to vertebral column on each side. It carres axons mainly from pregang neurons destined to specific ganglion.
Ansa subclavia
Sympathetic trunk divides to form this loop which wraps around subclavian artery (between cervicothoracic and middle cervical ganglia)
Ramus communicans
Communicating branch between a spinal nerve and the sympathetic trunk.
Cranial cervical ganglia
Most cranial ganglia. At head
Middle cervical ganglia
Supplies heart, lungs, other thoracic viscera
Cervicothoracic ganglia
thoracic viscera, supplies thoracic limb (via brachial plexus), neck (via vertebral nerve)
Sympathetic trunk ganglia
Spinal nerves of the trunk, pelvic limbs and tail. Found along the symp trunk in the thoracic, lumbar, and sacral regions.
Celiacomesenteric ganglia
Supploes abdominal viscera
Caudal mesenteric ganglia
Supplies caudal abdominal viscera, pelvic viscera (via hypogastric nerve)
Splanchnic
Sympathetic pregang axons supplying Caudal mesenteric ganglia,`
Plexus
Mixed collection of axons traveling in close proximity to one another.
Horner’s Syndrome
Loss of sympathetic innervation to the head
- ->miosis: small pupil
- ->Enophthalmos:sunken eye ball
- ->ptosis: droopy eyelid
- ->Protrusion of 3rd eyelid
