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Anatomy of the Nervous System Study Notes

Anatomy of the Nervous System Study Notes

13.3 Circulation & The CNS

  • Objectives:

    • Describe the blood supply vessels to the CNS.

    • Name the ventricular system components and associated brain regions.

    • Explain cerebrospinal fluid (CSF) production and flow through ventricles.

    • Explain how circulation disruptions can result in stroke.

Arterial Supply

  • Carotid Arteries

    • Participate in the orthostatic reflex, which is a physiological response to changes in body position.

  • Vertebral Arteries

    • Supply blood to the posterior part of the brain.

    • Includes:

    • Anterior spinal arteries

    • Basilar artery

  • Circle of Willis

    • An important anastomosis of arteries at the base of the brain.

Stroke

  • Defined as a disruption of the blood supply to the brain.

  • Results in blockage which leads to surrounding tissues becoming deprived of oxygen (O2) and essential nutrients.

  • Impacts brain function, leading to loss of specific abilities (e.g., a stroke in the lateral medulla can cause the loss of the ability to swallow).

  • FAST mnemonic for stroke detection:

    • Face: drooping on one side

    • Arms: weakness or inability to raise both arms

    • Speech: slurred or abnormal speech

    • Time: call emergency services immediately.

Venous Return

  • Dural Sinuses

    • Cavities that contain veins which collect venous blood from the brain.

    • Includes:

    • Superior sagittal sinus: absorbs cerebrospinal fluid (CSF)

    • Confluence of sinuses

    • Sigmoid sinuses: drain into the jugular veins.

Meninges

  • Layers (from superficial to deep):

    • Dura Mater

    • Tough, fibrous outer layer.

      • Contains two layers of fibrous connective tissue: periosteal and meningeal layers.

      • Encloses dural venous sinuses and has partitions such as falx cerebri, falx cerebelli, and tentorium cerebelli.

    • Arachnoid Mater

    • Web-like, fine, and elastic connective tissue.

    • Pia Mater

    • Delicate, gentle layer that is in direct contact with the brain tissue.

  • Functions of Meninges:

    • Protect the central nervous system (CNS).

    • Protect vascular structures.

    • House CSF.

    • Form partitions within the skull (e.g., falx cerebri separates cerebral hemispheres).

Ventricles of the Brain

  1. Lateral Ventricles (two)

    • Located in each hemisphere of the brain.

  2. Interventricular Foramen (foramen of Monro)

    • Connects lateral ventricles to the third ventricle.

  3. Third Ventricle

    • Thin, vertically oriented cavity located in the midline of the brain.

  4. Cerebral Aqueduct (aqueduct of Sylvius)

    • Connects the third ventricle to the fourth ventricle.

  5. Fourth Ventricle

    • Located between the brainstem and cerebellum.

Cerebrospinal Fluid (CSF) Pathway

  • CSF is secreted by the choroid plexus within each lateral ventricle.

  1. Flows through interventricular foramina into the third ventricle.

  2. The choroid plexus in the third ventricle adds additional CSF.

  3. CSF flows down the cerebral aqueduct to the fourth ventricle.

  4. The choroid plexus in the fourth ventricle contributes more CSF.

  5. CSF exits through two lateral apertures and one median aperture, filling the subarachnoid space and bathing the exterior surfaces of the brain and spinal cord.

  6. At the arachnoid granulations, CSF is reabsorbed into the venous blood of the dural venous sinuses.

13.4 Peripheral Nervous System

  • Objectives:

    • Describe PNS structures.

    • Distinguish between somatic and autonomic structures, including enteric nervous system components.

    • List and describe the twelve cranial nerves and their functions.

    • Detail the sensory and motor components of spinal nerves and their associated plexuses.

Ganglia

  • Defined as groups of neuron cell bodies located in the periphery of the nervous system.

    • Dorsal Root Ganglion: contain sensory endings in the periphery.

    • Cranial Nerve Ganglion: analogous to dorsal root ganglia, but associated with cranial nerves instead of spinal nerves.

  • Sympathetic Chain Ganglia: arranged in a chain along the vertebral column.

    • Paravertebral Ganglia: located in the cervical region.

    • Prevertebral Ganglia: located anterior to the vertebral column.

    • Autonomic Ganglia: involved in the autonomic nervous system.

  • Terminal Ganglia: receive input from cranial & sacral nerves (associated with parasympathetic activities).

  • Plexus: network of fibers that are incorporated into organ walls.

Nerves Structure

  • Epineurium: outer connective tissue layer.

  • Fascicles: bundled axons within a nerve.

  • Endoneurium: inner layer enclosing individual axons.

  • The structural organization parallels that of muscular tissue layers.

Cranial Nerves

  • Overview:

    • Total: Twelve (12) pairs of cranial nerves, indicated with Roman numerals (I to XII) and descriptive names.

  • Cranial Nerves List and Functions:

    • CNI - Olfactory n.: Special sense of smell (sensory).

    • CN II - Optic n.: Special sense of vision (sight) (sensory).

    • CN III - Oculomotor n.: Motor innervation to extraocular muscles and pupil (motor).

    • CN IV - Trochlear n.: Motor innervation to one extraocular muscle (motor).

    • CN V - Trigeminal n.: General sensory to the face and motor innervation to mastication muscles (both).

    • CN VI - Abducens n.: Motor innervation to one extraocular muscle (motor).

    • CN VII - Facial n.: Motor innervation to facial expression, innervates salivary glands, and special sense of taste (both).

    • CN VIII - Vestibulocochlear n.: Special sense of hearing and balance (sensory).

    • CN IX - Glossopharyngeal n.: Motor innervation to stylopharyngeus, special sensory taste, and general sensory to the tongue (both).

    • CN X - Vagus n.: Motor innervation to palate and pharynx, taste to epiglottis, and sensory to ear and throat (both).

    • CN XI - (Spinal) Accessory n.: Motor to trapezius and sternocleidomastoid (motor).

    • CN XII - Hypoglossal n.: Motor to tongue muscles (motor).

Cranial Nerve Mnemonics

  1. Oh = Olfactory

  2. Oh = Optic

  3. Oh = Oculomotor

  4. To = Trochlear

  5. Touch = Trigeminal

  6. And = Abducens

  7. Feel = Facial

  8. Very = Vestibulocochlear

  9. Good = Glossopharyngeal

  10. Velvet = Vagus

  11. AH! = Spinal Accessory & Hypoglossal

  12. Some Say Money Matters But My Brother Says Big Brains Matter More

    • This mnemonic indicates the sensory/motor classifications of each cranial nerve.

Brachial Plexus

  • Supplies nearly all nerves for the upper extremity.

  • Contributed by ventral rami from (C4) C5-T1 (T2).

  • Emerges between the anterior and middle scalene muscles.

  • Terminal Branches:

    • Musculocutaneous

    • Radial

    • Median

    • Ulnar

    • Axillary Nerves

Lumbar Plexus

  • Provides nerves for the lower abdomen, anterior and medial thigh.

  • Contributed by ventral rami from L1-L4.

  • Key nerves include:

    • Iliohypogastric

    • Ilioinguinal

    • Genitofemoral

    • Femoral Nerve

    • Lateral femoral cutaneous

    • Obturator

Sacral Plexus

  • Supplies nerves for the pelvis, posterior thigh, and virtually all leg and foot regions.

  • Contributed by ventral rami from L4-S4.

  • Key components include:

    • Superior gluteal

    • Inferior gluteal

    • Common fibular

    • Tibial

    • Sciatic

    • Posterior femoral cutaneous

    • Pudendal

  • Emerges through the pelvis, located inferior to the piriformis muscle.

Questions?

  • Contact: Juliet Moore

    • Office: HSC Tower 320

    • Email: moorejl@udel.edu

Recommended Media

  • Movie Recommendation: The Disaster Artist - A film about the making of The Room.