ANS Flashcards
What is the function of the ANS?
Homeostasis
• Maintenance of steady state environment for internal organs and body tissues
- Influences smooth muscle, cardiac muscle, secretory glands and visceral targets
- Regulates:
- Vasculature
- Circulation
- Respiration
- Digestion
- Body temperature
- Reproduction
- Secretions
- Metabolism
What is the difference between the ANS and Somatic?
Similarities
- Visceral SENSORY or ASCENDING pathways
- SENSORY AFFERENTS
- Visceral REFLEX ARCS
- Ex. Gut Peristalsis
- DESCENDING MOTOR
PATHWAYS
• MOTOR EFFERENTS
Differences
Somatic NS
- Direct Efferent to Target
- LMN to Skeletal Muscle
Autonomic NS
- Two Neuron Chain Efferent to Target
- Preganglionic Neurons and Postganglionic Neurons to Target Organs
What are the autonomic reflexes? 3
Reflexes are crucial for and assist with physiological functions
- Baroreceptor reflex
- Micturition reflex
- Body temperature regulation
What is the sympathetic NS and where are its neurons?
Sympathetic NS
- AKA Thoracolumbar Division
- Cell bodies of Preganglionic Sympathetic Neurons located in…
- Interomedial Lateral Horn of Thoracic and Lumbar Gray Matter of Spinal Cord (T1-L2 spinal cord segments)
What is the parasympathetic NS and where are its neurons?
Parasympathetic NS
- AKA Craniosacral Division
- Cell bodies of Preganglionic Parasympathetic Neurons located in…
• Brainstem Medulla: CN III (Oculomotor), VII (Facial), IX (Glossopharyngeal), X (Vagus)) or Sacral Gray Matter of Spinal Cord (S2,3,4 spinal cord segments)
What is pathway 1 for the SNS?
SYMPATHETIC NERVOUS SYSTEM
Cell Bodies of Preganglionic Sympathetic Neurons exit Ventral Horn of Spinal Cord via White Ramus to…
Pathway 1:
• Sympathetic Chain Ganglia AKA Paravertebral Ganglia AKA Sympathetic Trunk
- Synapse with…
- Postganglionic Sympathetic Neurons
- Exits Gray Ramus to Target Organs • Thoracolumbar Outflow: T1-L2 levels
- Innervate adrenal medulla, vasculature, sweat glands & viscera
What is pathway 2 for SNS?
SYMPATHETIC NERVOUS SYSTEM
• Cell Bodies of Preganglionic Sympathetic Neurons exit Ventral Horn of Spinal Cord via White Ramus to…
Pathway 2:
- Three Collateral Ganglia AKA Prevertebral Ganglia
- Celiac Ganglia
- Superior Mesenteric Ganglia
- Inferior Mesenteric Ganglia
- Synapse with…
- Postganglionic Sympathetic Neurons to Target Organs • Innervate digestive, urinary and reproductive systems
What is the PNS pathway?
Parasympathetic Nervous System
- Cell Bodies of Preganglionic Parasympathetic Neurons exit Brainstem and Sacral Spinal Cord to Terminal Ganglion (long distance)
- Postganglionic Parasympathetic Neurons travel from Terminal Ganglion on to Target Organ
- CN III, VII, IX & X: Innervate pupil, salivary glands, and viscera
- Sacral Region: Innervate via pelvic splanchnic nerve for regulation of digestive, urinary and reproductive systems
SNS and PNS
See pic
What are the major neurotransmitters for the ANS? Where are they or are not found?
ANS Neurotransmitters: Acetylcholine (Ach), Norepinephrine and Noradrenaline
-
Cholinergic: (Ach)
- Preganglionic Sympathetic Neurons and Preganglionic Parasympathetic Neurons both release Ach
- Postganglionic Parasympathetic Neurons release Ach
-
Adrenergic: Norepinephrine and Noradrenaline
- Postganglionic Sympathetic Neurons release Norepinephrine and Noradrenaline
What is the Ventricular System?
- Lateral Ventricles (2): which are
- C-Shaped and comprised of Three Horns:
- Anterior or Frontal Horns
- Inferior or Temporal Horns
- Posterior or Occipital Horns
- Body located in Frontal and Parietal Lobes
- One in each Cerebral Hemisphere
- C-Shaped and comprised of Three Horns:
- Connected to Interventricular Foramen AKA Foramina of Monro
- Connected to Third Ventricle which is located in and surrounded by Diencephalon
- Connected to Cerebral Aqueduct of Sylvius • Located in Midbrain
- Connected to Fourth Ventricle
- Located in Pons and Medulla • Continues on as…
- Central Canal which is Located in Caudal Medulla and Spinal Cord
Describe the 4th Ventricle
- Fourth Ventricle
- Between Pons /Medulla and Cerebellum
- Three Apertures
How Ventricular System communicates with Subarachnoid Space (Between Arachnoid and Pia Mater)
- (1) Median Aperture AKA Foramen of Magendie
- (2) Lateral Apertures AKA Foramen of Luschka
What is CSF? What is the Choroid Plexus?
- Choroid Plexus is an highly convoluted and vascular membraneous material that secretes Cerebral Spinal Fluid (CSF).
- Composed of…
- Invaginations into the ventricles
- Arteries, veinules and capillaries
- Ependymal Layer and Pia Mater (Side faces Subarachnoid Layer)
- Cerebral Spinal Fluid is a clear, colorless fluid.
- Purpose is to bathe and nourish the brain and spinal cord
- Produced in the Choroid Plexus
- CSF Circulation turns over several times a day
What is the pathway for CSF?
CSF Forms in the Lateral Ventricles
• Through Interventricular Foramen
• Through Third Ventricle and Cerebral Aqueduct
- Through Fourth Ventricle
- Through Median Aperture and Lateral Apertures
- (1) Median Aperture AKA Foramen of Magendie
- (2) Lateral Apertures AKA Foramen of Luschka • To Cisterna Magna and Pontine Cistern
• Then…
- Superiorly, over Cerebral Hemispheres • Through Superior Sagittal Sinus
- Into Arachnoid Villi for reabsorption
- Returns into Venous System
• And…
- Inferiorly, down to Lumbar Cistern
- Into Arachnoid Villi for reabsorption
- Returns to Venous System
What are the meninges?
- Located between Brain and Cranium and encases Spinal Cord
- “Holds it all together” during head and body movements • Three Meningeal Layers
- Dura Mater (outer) • Arachnoid (middle) • Pia Mater (inner)
What is the dura mater?
What are the 3 dural reflections?
What is the blood supply? And what’s a lesion called there?
Meninges: Dura Mater
- Thickest of the three layers
- Attached to Cranium
- Comprised of Extensions into the cranial cavity called
- Dural Reflections or Dural Septa (Runs between two Cerebral Hemispheres)
- Falx Cerebri (extends into Medial Longitudinal Fissure)
- Tentorium Cerebelli (extends in between Cerebral Hemispheres and Cerebellum)
- Dural Sinuses
- Channels for Dural Venous Sinuses (openings for vessels and nerves)
- Receives CSF from Subarachnoid Space
- Located along Falx Cerebri and Tentorium Cerebelli
- Major Blood Supply
- Middle Meningeal Artery (source for bleeds)
- Bleeding into Subdural Space (Potential Space) called Subdural Hematoma
- Pain Sensitive due to Trigeminal Nerve
- Around eye, temple and forehead
- Pain NOT felt in brain, arachnoid and pia mater
What is the arachnoid?
Meninges: Arachnoid
- Located just inferior to Dura Mater
- Thin avascular layer only a few cells thick (spider web-like)
- Purpose is to keep brain suspended via the Arachnoid Trabeculae
- CSF enters the venous circulation via the Arachnoid Villi
What is the pia mater?
Meninges: Pia Mater
- Located inferior to Arachnoid
- Fine membrane closely adhering to ALL external surfaces of the brain and spinal cord
- Hugs every contour of the gyri and sulci
- Merges tightly with the Arachnoid Trabeculae
What are potential spaces in the meninges?
Injury to the Meninges
- “Potential Spaces”
- Epidural Space is between the Dura Mater and Cranium
- Subdural Space is between the Dura Mater and Arachnoid
- Often due to a bleed that opens up the space
- Cause for creating “potential space”
- Source from Meningeal Artery
- Epidural Space: Epidural Hematoma
- Subdural Space: Subdural Hematoma
