Brain and Cranial Nerves

Secondary vesicles during embryonic development (superior to inferior)

1. Telencephalon

2. Diencephalon

3. Mesencephalon

4. Metencephalon

5. Myelencephalon

6. Spinal cord

forms cerebrum

Telencephalon

1. Epithalamus

2. Thalamus,

3. Hypothalamus,

4. pineal gland

Diencephalon

midbrain

mesencephalon

• Pons

• Cerebellum

Metencephalon

Medulla Oblongata

Myelencephalon

• Neuron cell bodies

• Dendrites

• Unmyelinated axons

structures found in gray matter

superficial layer of gray matter

cortex

clusters of gray matter deep within the brain

Nuclei

three meninges from superficial to deep

• Dura mater (Superficial)

• Arachnoid mater (Middle)

• Pia mater (Deep)

type of tissue dura mater is made of

Dense irregular connective tissue (CT)

two layers of the dura mater

• Periosteal layer – Attached to the skull

• Meningeal layer – Forms dural septa (folds that support the brain)

middle meninge layer between the dura matter and pia matter

1. Arachnoid matter (archne = spider )

   1. “web” of collagen elastic fiber

   2. Contains CFS in subarachnoid space

space is between the dura mater and the arachnoid mater

subdural space (contains csf)

innermost meninge layer

1. Pia matter (tender mother)

   1. areolar CT

   2. “form-fitting”

Brain ventricles

1. Lateral ventricles (1st & 2nd) – in each hemisphere

2. Third ventricle – in the diencephalon

3. Fourth ventricle – between the brainstem & cerebellum

In the cerebrum, one in each hemisphere

lateral ventricles

In the diencephalon, between the left & right thalamus

third ventricle

Between the brainstem & cerebellum

fourth ventricle

What two structures form the BBB?

1. Astrocytes – Their end feet wrap around capillaries

2. Blood capillaries – Have tight junctions preventing leakage

function of the blood-brain barrier (BBB)

Prevents neuron exposure to harmful substances like toxins, drugs, and waste

Where is CSF produced?

Choroid plexus in the ventricles

Cells involved in producing CSF

Specialized ependymal cells in the choroid plexus

What are the three main functions of CSF?

1. Cushioning (protection)

2. Buoyancy

3. Transport – Delivers nutrients & removes waste

What are the main functions of the cerebrum?

conscious thought & complex intellectual functions

• ↳ Intelligence & reasoning

  ↳ Thought, memory, & judgment

  ↳ voluntary motor, visual auditory

Longitudinal fissue

paired cerebral hemispheres are separated by a…

gyri (singular: gyrus)

Ridges or folds on the brain’s surface that increase surface area for neurons

sulci (singular: sulcus)

hallow grooves between gyri that help separate brain regions

Frontal lobe - functions

who u are/motor

• Higher intellectual functions

  • (concentration, decision-making, planning);

• personality;

• verbal communication;

• voluntary motor

temporal lobe - functions

• language

• emotion

• smell

• auditory

Parietal lobe - functions

• general sensory

  • understand position in the environment

Occipital lobe - functions

• visual input

• visual memories

memory, sense of taste

Insula

Motor areas

• ↳Control voluntary motor functions

• ↳ Info going out

  • ↳ Frontal lobe

• precentral gyrus;

  • voluntary contralateral skeletal

Motor Area - Primary (1°) motor cortex

• muscles for eye movement;

  • reading and coordinating

  • binocular vision

Motor Area - Frontal eye field

• muscles used in speech;

  • usually left front lobe only

Motor Areas - Motor speech area (Broca area)

↳ Involved w/ the conscious awareness of sensation

↳ Info going in

↳ parietal lobe

Sensory areas

• postcentral gyrus;

  • general sensory info.

Sensory Areas - 1°somatosensory cortex

• occipital lobe;

  • visual information from eye

Sensory Areas - 1°visual cortex

• temporal lobe;

  • auditory info. from inner ear

Sensory Areas - 1°auditory cortex

• temporal lobe;

  • olfactory info. from nasal cavities

Sensory Areas - 1°olfactory cortex

• insula;

  • taste info. from taste buds

Sensory Areas - 1°gustatory cortex

↳ Process & interpret sensory input and /or coordinate motor output

↳ puts info together

• all over

Association areas

• coordinating learned,

  • skilled motor activities (e.g. reading, grasping)

Association areas - Premotor cortex (somatomotorassociation area)

• understanding of the object producing the stimulus

  • e.g. texture, temperature, pressure, shape

Association areas - Somatosensory association area

• color, movement, form, facial recognition

Association areas -Visual association area

• correlates with memories of sound

  • music

Association areas - Auditory association area

• recognizing/understanding spoken & written language;

  • parietal and temporal lobes;

  • works w/ other areas to speak, type, & write

Association Areas - Wernickearea (hearing)

• integrates all sensory input into a coherent whole

  • produce a comprehensive understanding of current activity;

    • Speaking

    • nostic=knowledge

Association Areas - Gnostic area

• Axons that connect regions within the same hemisphere of the brain

  • arcuate - Connect adjacent gyri (precentral & postcentral gyrus)

  • longitudinal - Connect lobes of the same hemisphere (long-range connections

Cerebral White Matter - association tracts

Curved fibers connecting areas within the same lobe of the brain.

Cerebral White Matter - accurate fibers

Association tracts that connect different lobes within the same hemisphere.

Cerebral White Matter - longitudinal fasciculi

Fibers that connect the left and right hemispheres of the brain.

Cerebral White Matter - commissural tracts

The largest commissural tract connecting the two hemispheres of the brain.

Cerebral White Matter - corpus callosum

• Fibers that connect the cerebrum to the lower brain

  • brainstem and spinal cord

  • Decussate = contralateralization

Cerebral White Matter - Projection tracts

crossing over of nerve fibers

Cerebral White Matter - Projection tracts (Decussate = contralateralization)

• control autonomic NS

  • fight/flight/rest/digest

• regulate

  • body temp

  • hunger

  • sleep/wake cycle

  • emotional behavior

Diencephalon – hypothalamus

• Receives conscious Senses

  • ↳ Except olfaction - smell

• Filters & relays to primary Cortices & association areas

Diencephalon – Thalamus

• pineal gland

  • ↳Endocrine gland Secretes melatonin

  • ↳ Regulates Circadian rhythm

Diencephalon – Epithalamus

Brainstem – autonomic functions

Connects cerebrum, diencephalon, and cerebellum to spinal cord

Mesencephalon -Midbrain

• Superior portion of brainstem

• Sensory & motor tracts connecting

  brain to spinal cord

• autonomic functions

descending motor axons

Mesencephalon - Cerebral Peduncles

“visual reflex centers”

Mesencephalon - Superior Colliculi

“auditory reflex centers”

↳ Only seen in cross section

Mesencephalon - Inferior Colliculi

• Anterior, middle portion of brainstem

• Sensory & motor tracts connecting brain to spinal cord

  • Autonomic functions

Metencephalon - Pons

connects pons to cerebellum

Metencephalon - Middle Cerebellar Peduncles

regulate rate and depth of breathing

Metencephalon - Autonomic

Respiratory Centers

↳ Involved in sound localization

Metencephalon - Superior Olivary complex

• Inferior portion of brainstem

  • continuous w/ spinal cord inferiorly

• sensory & motor tract connecting brain to Spinal cord

• Autonomic function

Myelencephalon –Medulla Oblongata

motor fibers crossover = contralateralization

Myelencephalon – medulla oblongata (Decussation of the Pyramids)

• Regulate heart rate and strength

• Controls blood pressure (arteriole control)

• Respiratory rate (along with

  pons)

Myelencephalon – medulla oblongata Important Autonomic Centers:

Meyelencephalon–Medulla Oblongata (centers controlling)

• coughing

• sneezing

• salivating

• swallowing

• gagging

• vomiting

• hicupping

• Responsible for:

  • coordinating & fine-tuning movements

  • ↳ Planning & executing movements

  • agility (skill)

    ↳ Balance & Posture

    ↳ Adjusts & regulates movements (smoothness)

Metencephalon – cerebellum functions

How many cranial nerve pairs are there?

12 pairs

Where do cranial nerves originate and what regions do they serve?

• Mostly the head and neck,

  • except Vagus (CN X)

    • extends to the thoracic and abdominal organs.

sensory - olfaction (smell)

Cranial Nerve I (olfactory)

sensory - vision

Cranial Nerve II (optic)

somatic motor - four extrinsic eye muscle

Cranial Nerve III (oculomotor)

somatic motor - One extrinsic eye movement

Cranial Nerve IV (trochlear)

sensory - general sensory from surface of head & mouth, including from anterior 2/3 mouth

motor - muscle of mastication

Cranial Nerve V (trigeminal)

motor - 1 extrinsic eye muscle

Cranial Nerve VI (abducens)

sensory - taste from anteiror 2/3 tounge

motor - muscle of facial expression

Cranial Nerve VII (facial)

sensory - hearing & equilibrium

Cranial Nerve VIII (vestibulococclear)

sensory - touch & taste 1/3 tongue

motor - one pharyngeal muscle

Cranial Nerve IX (glossopharyngeal)

sensory - visceral sensory most organs

motor - most pharyngeal & laryngeal muscle

Cranial Nerve X (vagus)

motor - two body muscle

Cranial nerve XI (accessory)

motor - muscle of tounge

Cranial Nerve XII (hypoglossal)