Anatomy Exam 3

Central Nervous System

Central Nervous System

Brain and spinal cord

Peripheral Nervous System

Rest of body (brain and cranial nerves)

Sensory (afferent) system

General body sensation and special senses

Motor (efferent) systems

Work on skeletal muscles and autonomic system

Somatic Nervous System

Works on skeletal muscles, voluntary movements

Autonomic Nervous System

Involuntary movements

Sympathetic Nervous System

Responsible for flight or fight response when stressed

Parasympathetic Nervous System

Builds up energy and digests food

Astrocytes

Found in the CNS

Star-shaped, make the BBB, help maintain a chemical environment for nerve impulses

Oligodendrocytes

Found in the CNS

Form the myelin sheath

Microglia

Found in the CNS
Involved in immunity, phagocytes (engulf any bacterial/virus and destroy it to protect nervous tissue)

Ependymal cells

Found in the CNS

Lines spaces in the brain (ventricles to move CSF)

Schwann cells

Found in the PNS
Surround the axon, and form the myelin sheath

Satellite cells

Found in the PNS

Surround the cell body, offer structural support

Nucleus

Clusters of neuron cell bodies in the CNS

Ganglion

Cluster of neuron cell bodies in the PNS

Tract

Bundles of axons in the CNS

Nerve

Bundles of axons in the PNS

White Matter

Made of myelinated axons

Grey Matter

Made of everything else (unmyelinated axons, cell bodies, dendrites, neuroglia)

Vertebral Foramina

Protects the spinal cord

Intervertebral Foramina

Protects the spinal nerves exiting the spinal cords

Spinal Meninges

Protective tissue layers, continuous with cranial meninges, protects the spinal cord, found inside the vertebral foramen

Dura Mater

Outer layer, made of dense irregular CT

Arachnoid Mater

Middle layer, has little strips of tissue that form a web-like connection

Pia Mater

Inner layer, delicate layer, sits directly on top of the spinal cord

Epidural Space

Between the bone and the dura mater, contains fat cushioning (adipose tissue)

Subdural Space

Between dura mater and arachnoid mater, contains interstitial fluid

Subarachnoid Space

Between arachnoid and pia mater, contains CSF

Spinal Cord External Anatomy

16-18” long

0.6” in diameter

Begins at medulla oblongata

Ends between L1 and L2

Cervical Enlargement (in the spinal cord)

Nerves of the upper limbs

Lumbar Enlargement (in the spinal cord)

Nerves of the lower limbs

Conus Medullaris

Tapered, inferior end of the spinal cord (between L1 and L2)

Filum Terminale

Fusion of the meninges that anchors the conus medullaris to the coccyx

Cauda Equina

Inferiorly projecting roots of nerves that will exit the vertebral column below L2

Anterior Median Fissure

Deep dip on the anterior side of the spinal cord

Posterior Median Sulcus

Shallow dip on the posterior side of the spinal cord

Central Canal

Middle of the spinal cord, contains CSF

Posterior Grey Horn

Sensory neuron axons

Lateral Grey Horn

ANS motor neuron cell bodies

Anterior Grey Horn

Motor neuron cell bodies

Grey Commissure

Connects the two sides of the grey matter core

Anterior White Commissure

Connects the sides of the surrounding white matter

Spinal Nerves

31 pairs

Exit via intervertebral foramina

Doral Root

Contains sensory (unipolar) neurons

Doral Root Ganglion

Contains cell bodies of unipolar sensory neurons

Anterior Root

Contains motor neurons

Spinal Nerve

Mixed sensory and motor neurons, this is where the roots come together

Dorsal Ramus

Branch off the spinal nerve

To/from posterior area of the body (smaller)

Anterior Ramus

Branch off the spinal nerve

To/from lateral, internal, anterior, area of the body (larger)

Epineurium

Covers the entire nerve

Perineurium

Separates bundles of axons into little packages called fascicles

Endoneurium

Surrounds each individual axon

Damage to Spinal Cord

Any damage is serious

The more super the damage the more consequences there are

Dermatomes

Area of the skin that provides sensory information via a pair of spinal nerves, can be used to diagnose spinal nerve damage or provide anesthesia to a specific area of the body

Epidurals

Often used to manage pain during childbirth; anesthetic injection into epidural space, the drug targets sensory neurons that convey pain

Spinal Taps

Can be used to remove some CSF for diagnostic purposes or to introduce drugs, the needle is inserted into the subarachnoid space between L3 and L4

Spinal Reflexes

Integrated in the spinal cord, below conscious detections (this is the initial moving away before you fully realize that happened)

Functions of the BBB

Exchange: brings O2 and nutrients, removes CO2 and waste

Protection: from bacteria, viruses, and toxins

Homeostatic Regulation: maintain a stable environment for neuron functions

Structure of the BBB

Tight junctions between capillary cells to keep the blood inside and everything else out

Astrocyte projections that wrap around the capillaries and secrete chemicals to maintain tight junctions

Easily pass through BBB

Lipid-soluble substances such as gasses and some drugs such as alcohol, anesthesia, and antidepressants

Pass slowly/need help crossing the BBB

Some water-soluble substances such as glucose and ions

Do not pass through the BBB

Most other substances such as proteins and must drugs such as antibiotics

Functions of CSF

Exchange of gasses, nutrients, and waste

Homeostatic regulation

Mechanical protection: forms a water bath the brain floats in (buoys the brain)

Composition of CSF

Filtered blood plasma

Clear liquid made of mostly water with dissolved ions and sugar

Formation of CSF

Made in choroid plexuses

Choroid Plexus

Blood capillaries are surrounded by ependymal cells (joined by tight junctions) and the blood is filtered through those

Circulation of CSF

1. Made in choroid plexuses in lateral ventricles

2. Flows from lateral ventricles through interventricular foramina to 3rd ventricle

3. Flows from 3rd ventricle through cerebral aqueduct to 4th ventricle

4. From 4th ventricle the CSF flows

   • Down central canal of spinal cord

   • Into subarachnoid space around spinal cord

   • Into subarachnoid space around the brain

5. CSF is reabsorbed into blood in dural venous sinuses via the arachnoid villi

Medulla Oblongata

Most inferior, all white matter tracts pass through here, contains both sensory and motor neurons

Contain all white matter sensory and motor tracts that pass between the brain and spinal cord

Decussation of the Pyramids

X like structure on the posterior side, this is where most of the axons cross over

Cardiovascular Center

Key nuclei in the medulla oblongata

Controls the rate and force of heartbeat and the diameter of blood vessels

Medullary Respiratory Center

Key nuclei in the medulla oblongata

Adjusts the rhythm of breathing

Cranial Reflexes

Key nuclei in the medulla oblongata

Vomiting, swallowing, sneezing, coughing, hiccupping

Senses

Key nuclei in the medulla oblongata

Taste, hearing, equilibrium

Pons

Superior to the medulla oblongata

Bridge that connects (Pons)

Right and left sides of the cerebellum

Cerebrum and cerebellum

Pontine Respiratory center

Key nuclei in the pons

Together with the medullary respiratory center, helps control breathing

Midbrain

Superior to the pons, connects to the diencephalon, surrounds the cerebral aqueduct

Cerebral Peduncles

Connect motor area in the cerebrum to the pons, medulla oblongata, and the spinal cord

Superior Colliculi

Key nuclei in the midbrain

Visual reflex center

Inferior Colliculi

Key nuclei in the midbrain

Auditory relay pathway

Reticular Formation

Loosely arranged network of grey and white matter scattered throughout the brainstem

Reticular Activating System

Ascending sensory neurons that project to the cerebral cortex and descending motor neurons that regulate muscle tone

Roles of the RAS

Consciousness (inactivation of the RAS cases sleep), attention, prevents sensory overload (filters out insignificant stimuli from reaching consciousness)

Cerebellum

Located on the posterior side of the brainstem, highly folded surface

Divided into a right and left hemisphere

Folia

Grey matter cortex of the cerebellum

Arbor Vitae

White matter cortex of the cerebellum

Functions of the Cerebellum

Coordinate movements, regulate posture and balance

Diencephalon

Central core (deep) surrounded by the cerebrum, superior to the midbrain, surrounds the 3rd ventricle. Has three main parts

Thalamus

Divided into two lobes connected via inter thalamic adhesion

Surrounded by the third ventricle

Major relay station (sensory impulses pass through here on the way to the cerebral cortex; motor impulses pass through here between the cerebral cortex and cerebellum)

Hypothalamus

Inferior to the thalamus

Part of the endocrine system

Connects to the pituitary gland via the infundibulum

Contains mamillary body (prominent bump on inferior side)

Functions of the hypothalamus

Major regulator of homeostasis

Control of the ANS

Production of hormones

Regulation of emotional and behavioral patterns

Regulation of thirst and hunger

Control of body temperature

Regulation of circadian rhythms

Epithalamus

Superior and posterior to thalamus

Contains pineal gland (secretes melatonin)

Circumventricular Organs (CVOs)

Found throughout the diencephalon

Located in wall of 3rd ventricle

Lacks a BBB so it can monitor changes in the blood

Cerebrum

“Seat of intelligence”

Separated into R and L hemispheres by longitudinal fissure, connected by corpus callosum

Made of five lobes

Organization of the Cerebrum

Gyri: ridges

Sulci: valleys

Fissures: deep grooves

Association white matter tracts

Between gyri in the same hemisphere

Commissural white matter tracts

Between corresponding gyri in opposite hemispheres

Projection white matter tracts

Between cerebrum and lower parts of the brain

Basal Nuclei

Deep/inner masses of grey matter