Brain + Spinal Cord

Top to bottom

1. lateral ventricles

2. interventricular foramen

3. third ventricle

4. cerebral aqueduct

5. fourth ventricle

1. Cervical Vertebrae

2. Nerves

1. 7 bones

2. C1 - C8

1. Thoracic Vertebrae

2. Nerves

1. 12 bones

2. T1-T12

1. Lumbar Vertebrae

2. Nerves

1. 5 bones

2. L1 - L5

1. Sacrum

2. Nerves

1. Just one bone

2. S1 - S5

Epineurium

Covers the peripheral nerve

• superficial

Perineurium

Around one fascicle of the peripheral nerve

• between the epineurium and the endoneurium

Endoneurium

inside the fascicle, covering the myelinated axon of the peripheral nerve

• deep

Spinal Nerves

Mixed nerves. Contain both afferent (sensory) and efferent (motor) fibers

• Anterior (ventral) Root

• Posterior (dorsal) Root

• Spinal (dorsal root) ganglion

Anterior (ventral) Root

axons of motor neurons

Posterior (dorsal) Root

Axons of sensory neurons

Spinal (dorsal) ganglion

cell bodies of sensory neurons just outside of the spinal cord

T or F: the spinal cord is not as long as vertebral column

True

Dermatome

the region of the skin innervated by nerves that originate from a single spinal nerve pair.

Meninges (Superficial to deep) in the spinal cord

1. Dura mater: thick and adheres to the vertebrae

2. Arachnoid mater: web-like, delicate layer

3. Pia mater: adheres directly spinal cord

Reflex arc

The wiring of a single reflex that includes 5 steps

1. arrival of stimulus and activation of receptor

2. activation of a sensory neuron

3. information processing in the CNS

4. activation of a motor neuron

5. Response by a peripheral effector

Reflex Organization (4 categories)

1. Development: innate or required

2. Response: somatic or visceral (autonomic)

3. Complexity: monosynaptic or polysynaptic

4. Processing site: cranial reflex or spinal reflex

Stretch Reflex

Monosynaptic reflex that control the most rapid motor responses of the nervous system. Provides automatic regulation of skeletal muscle length using muscle spindles

Muscle Spindles

• inner part made of intrafusal fibers associated with special sensory neurons

• outer part made of extrafusal fibers

Withdrawal Reflex

Makes you move away from pain.

• Reciprocal Inhibition: flexors stimulated; extensor inhibited or vice versa

Crossed Extensor Reflex

If you were to step on something painful. Makes both side of the body work

• Ipsilateral: the side receiving the painful stimulus. Pulls away

• Contralateral: the other side of the body used for stabling

Primary Brain Vesicles

1. Prosencephalon: forebrain

2. Mesencephalon: midbrain

3. Rhombencephalon: hindbrain

At 3 weeks

Secondary Brain Vesicles

1. Prosencephalon splits into telencephalon (cerebrum) and the diencephalon

2. Mesencephalon (midbrain)

3. Rhombencephalon splits into metencephalon (cerebellum and pons) and myelencephalon (medulla oblongata)

Meninges in the brain (superficial to deep)

1. Periosteal cranial dura

2. Dural sinus

3. Meningeal cranial dura

4. arachnoid mater

5. pia mater

1 and 3 make up the dura mater

Dural Folds

• Falx cerebri: dura mater growing down separating the left and right hemispheres

• Falx cerebelli: growing between the right and left hemispheres of cerebellum

• Tentorium cerebelli: growing between top and bottom of brain separating cerebellum from cerebrum

Superior sagittal sinus

wraps around the midline perimeter of brain

Functions of CSF

1. supports the brain

2. cushions the brain and spinal cord against physical trauma

3. transports nutrients, chemical messages, and wastes

Choroid Plexus

Makes the CSF inside the 3rd and 4th ventricles. Made up of ependymal cells anchores by tight junctions.

Arachnoid granulations

where arachnoid mater punctures through the dura mater creating a valve where CSF fluid can drain into the superior sagittal sinus

Blood supply to brain

internal carotid and vertebral arteries. Brain is protected by blood brain barrier made by astrocytes.

Reflex centers of the Medulla Oblongata

Reticular formation: Regulate autonomic functions like

breathing, blood pressure, thermoregulation. Regulates

some endocrine functions. Body posture, somatic reflexes,

alertness, sleep.

Cardiovascular centers: Regulates heart rate, force of

cardiac contractions, and peripheral blood flow.

Respiratory rhythmicity centers: regulate breathing rate

Decussation of pyramids

Somatic sensory information leaving the medulla oblongata to go to the thalamus, cross over to the opposite sides of the brain

Medulla oblongata cranial nerves

8-12

CN. VIII

vestibulocochlear nerve

• Sensory: vestibular (balance) and cochlear (hearing) systems of the ear

CN IX

glossopharyngeal

• sensory: taste from posterior 1/3 of tongue

• motor: some salivary glands and one muscle of the throat

CN X

Vagus nerve

• Sensory and motor: most muscles of the throat for swallowing and speaking, smooth muscle in most visceral organs

CN XI

Accessory nerve

• Some overlap with CN X.

• Motor: controls of some muscles in the neck (trapezius)

CN XII

Hypoglossal nerve

• Motor: control of tongue

Pons

Relays sensory info to the thalamus and cerebellum

White matter: relays info to other brain regions

Gray matter: functions overlap with other brain regions

• Apneustic and pneumotaxic centers: adjust activities of the respiratory rhythmicity in the medulla oblongata

Pons cranial nerves

5-8

CN V

Trigeminal nerve

• Sensory: face

• Motor: muscles of jaw for chewing

CN VI

Abducens nerve

• Motor: muscle that abducts the eyes

CN VII

Facial nerve

• Sensory: taste from the anterior 2/3 of tongue

• Motor: facial expressions and some salivary glands

Midbrain

Corpora quadrigemina

• Superior colliculi: control reflex movement of eyes, head, neck in response to visual stimuli

• Inferior Colliculi: control reflex movement of head, neck, and trunk in response to auditory stimuli

Substantia nigra: Appears black from presence of melanin. Secretes dopamine. Inhibits activity of basal nuclei in cerebrum, which control subconscious muscle tone and learned movements.

Midbrain cranial nerves

3 and 4

CN III

Oculomotor nerve

• motor: muscles that move the eye and constrict the pupil

CN IV

Trochlear nerve

• Motor: muscle that moves the eye

Functions of the cerebellum

1. Adjusting the postural muscles of the body

• Alters muscle tone to maintain balance

• Modifies activity of motor centers in brain stem

2. Fine-tuning movement controlled at conscious and subconscious level

• Refines learned movement patters

• Compares motor commands with proprioceptive information and makes

• adjustments so movements are smooth

• Works indirectly by regulating activity of motor pathways in other brain regions

top to bottom

1. vermis

2. anterior lobe

3. primary fissures

4. folia

5. posterior lobe