SHS 485: Neuroanatomy, navigational terms, + Etiology

Dorsal

Toward the sky.

May vary based on head positioning.

Examples:

• human —> superior (head), posterior (back)

  • (for below the head think: human laying on stomach/ on 4 legged position)

• dog —> superior (head), superior (back)

• shark —> superior (back)

  • (think: “dorsal fin”)

Ventral

Toward the ground.

• human —> inferior (feet), anterior (stomach)

  • (for below the head think: human laying on stomach/ on 4 legged position)

• dog —> inferior (feet), anterior (feet)

• shark—> inferior (feet)

Rostral

Toward the nose/snout (anterior).

Caudal

Toward the back/tail. (posterior)

What are the 3 anatomical planes?

• Sagittal: Vertical slice. Separates left + right

• Coronal: Vertical slice. Separates rostral + caudal

• Axial (transverse): Horizontal slice (x-axis). Separates dorsal and ventral (top + bottom)

What are the 2 major classes of nerve fibers? Where do they sit in relation to the spine?

1. Descending motor fibers (ventral/ toward human belly)

2. Ascending sensory fibers (dorsal/ toward human back))

How do reflexes work? where are they stored?

• Stored in the spinal cord.

• Allows for the quickness of life-saving reflexes bc: sensory and motor info not coming from distant brain. Instead its a loop within the spinal cord.

Gray matter vs White matter: Composition? Location in the Brain and Spine?

Composition

• gray: dendrites + somas (cell bodies)

• white: axon bundles (think terminals that send airplanes off…). Insulated with white, fatty myelin. The sensory ascending/ motor descending pathways

Location

• Brain

  • white —> inside

  • grey —> outside

• Spine:

  • white —> outside

  • grey —> inside

What 3 structures make up the brain stem? Their overall function?

Overall Function

Basic life sustaining functions. (CHAR)

• C - Circadian Rhythm

• H - Heart rate

• A - Arousal

• R - Respiration

3 Parts

1. Medulla

2. Pons

3. Midbrain

What 3 structures are in the three diff parts of the brain stem (medulla, pons, and midbrain)? What are their functions

Related to motor-speech impairments (as seen in Parkinson’s and Alzheimers:

• Substantia Nigra - produces dopamine. Motor control. (also: emotions, executive functions)

• Red Nucleus - Motor control

Other

• Cranial nerves - In Midbrain.

Cerebellum: Structure + Function?

Structure

The tiny little guy… under Cerebrum + caudal to Brainstem.

• 2 hemispheres

• Contains Cortex (gray matter)

Function

• Fine motor control (postural adjustment, drawing, speech articulation)

• Higher cognitive functions (language production + understanding, reading, saying alphabet backwards, math)

*What 3 structures make up the Diencephalon? Their Functions?

1. Subthalamus (part of basal ganglia circuit)

   1. F: motor control.

2. Hypothalamus (group of nuclei below thalamus)

   1. F: Essential life functions. “The 4 f’s” (Feed, Fight or flight, Freak…, Emotions)

3. Thalamus (2 eggs)

   • F: Sensory relay system.

     • Reciprocal + highly organized connection to Cerebrum: Obtains sensory, motor, and cognitive info and sends it to specific cortex of Cerebrum for processing. (Ie: visual sensory info sent to occipital lobe)

       • Reciprocal connection crucial for sensory-motor tasks + parallel processing?

Cerebrum: Composition and Function? How thick is it?

Composition

• 2 hemispheres; sit on top of diencephalon + brain stem.

• Cortex (outer layer… has 6 lobes) + Subcortex (everything underneath)

  • Lobes: frontal, parietal, temporal, occipital, Limbic (diencephalon cortical bodies), Insular

Thickness: 3-4mm

Function

• Seat of Cognition/thinking

  • (Also: func of the lobes… such as —> Judgment, problem-solving, temperature regulation, movement)

Subcortex: composition?

Composition

• white matter

• subcortical nuclei: Areas of gray matter underneath (dendrites + cell bodies)

• ventricles

(3) classes of white matter pathways?

1. descending pathways

• Motor info going down to muscles

2. ascending pathways

• Sensory info ascending up to brain

3. Cortico-cortical pathways

• Connections between different areas of the cortex

Two types of cortico-cortical:

1. within hemisphere

   • short fasciculi + long fasciculi

2. between hemisphere

• mostly homologous connections (one cortex is connected to the matching cortex in the other hemisphere)

• Commissures (small pathways)

• corpus callosum (long pathways)

What is the Limbic system? What structures are part of it?

Structures

• Amygdala, hippocampus, mammillary body, and cingulate gyrus

Function

• emotional regulation, behavior, motivation and memory

**What are the 3 subcortical nuclei?

• Basal Ganglia

  • Caudate nucleus, putamen, globus pallidus, subthalamic nucleus (diencephalon), substantia nigra (brainstem)

• Claustrum

  • Thin strip of gray matter.

  • L: Lateral to basal ganglia. Reciprocally connected with almost every area of the cortex

  • F: unknown

• Amygdala

  • L: Part of limbic system

  • F: Emotion + emotionally charged memories

Ventricles: What are they? What kind of fluid do they have inside and what is it important for?

Definition

• System of inter-connected fluid-filled cavities in the brain. 

Fluid

• CSF

  • Important for:

    • Brain development

    • Brain recovery

    • Protective brain cushioning

    • Drug delivery

What are Gyri and Sulci?

The hills and valleys/dips on the cerebral cortex.

*What is the Primary Cortex? What are its 4 cortical areas?

• Cortical areas with primary neural projection fields that sensory input pathways target FIRST. (sensory info’s first stop in cortex, in conscious awareness)

• Cortical areas with primary neural projection fields that travel down the spinal cord and send motor/sensory info out to the LAST stop. (?)

  • Ie)

    • Primary visual Cortex (calcarine sulcus) - the place your vision would go to be consciously aware of it.

    • Primary Auditory Cortex (Heschl’s Gyrus) - where sounds are consciously processed. Underneath Temporal Lobe.

    • Primary Somatosensory Cortex (Post-Central Gyrus)

    • Primary Motor Cortex (Pre-Central Gyrus)

*What is the Non-primary cortex?

• Known as the “Association Cortex”

  • Covers most of the cerebral surface

• F: Does the processing between the area sensory input enters (primary sensory cortices) + the motor behavior/output generated at the last stop (primary motor cortices).

Unimodal, multimodal

3 Examples of Topographic organization in Primary Cortex Projection Fields?

• Retinotopic (Primary Visual cortex): spatial arrangement in the primary visual cortex where each neuron represents a specific small region of the visual field

• Tonotopic (P. Auditory c.): Organized by frequency

• Somatotopic (P. sensory + motor cortex c): sensory + motor info from/on different body parts —> organized by size/different areas on the brain

What is Cortical Magnification?

When more neurons are devoted to…

• Primary Visual Cortex —> visual info right in front of us

• Primary Auditory Cortex —> Speech freq.

• Somatosensory —> sensitive senses or fine motor areas (ie: mouth/tongue/lips, hands/feet, etc)

**What are the two types of Association Cortices?

Unimodal (premotor) —> uses one sense

Multimodal (prefrontal) —> uses multiple senses together

• Ie) visual + auditory senses used when reading lips and hearing speech when listening to someone talk.

What does Laminar Organization refer to?

The tissue organization of the Cerebral Cortex.

What is the Neocortex? How many layers does it have?

The same thing as the cortex, but in more evolved mammalian species.

Function

• Conscious thought, sensory perception, spatial reasoning, language, and voluntary motor commands.

Layers —> 6 total

• Layers 2 + 3: corticocortical output layer

• Layer 4: primary input layer

• Layer 5 + 6: descending output layers (basal ganglia, thalamus, brainstem, spinal cord, claustrum)

Cryoarchitecture

organization of tissue/cell layers based on function

• Areas nearby + similar structure —> similar function

Columnar Organization

• When neurons are organized in the same vertical column if they have the same function (in the neocortex)

• 8000 neurons.

• Diameter: ~300-500 nanometers.

3 types of Columnar Functional organization?

1. Minicolumns

2. Columns

3. Hypercolumns