Week 5, Tuesday

Topic 3 CNS Anatomy for Quiz 3 pdf (continued)

Temporal Lobe

• Gyri and Sulci of the temporal lobe

  • Superior, middle and inferior temporal gyri

    • 3 horizontal gyri on the lateral surface of temporal lobe

    • Inferior continues onto inferior/medial surface of cerebrum

  • Superior and inferior temporal sulci

    • Horizontal

    • Separate temporal gyri

  • Occipitotemporal sulcus:

    • On inferior surface of lobe

    • Separates inferior temporal and occipitotemporal gyri

  • Occipitotemporal (fusiform) Gyrus:

    • On inferior surface of lobe

    • Runs from occipital lobe into temporal lobe

    • Bound by the collateral and Occipitotemporal sulci

  • Lingual Gyrus

    • On medial surface of lobe

    • Runs from occipital lobe into temporal lobe

    • Bound by the collateral and calcarine gyri

  • Collateral Sulcus

    • Separates Occipitotemporal Gyrus from limbic lobe

  • Inferior temporal Gyrus

  • Transverse temporal Gyrus

    • On superior aspect of temporal lobe

    • Buried within lateral sulcus

Functions of Temporal Lobe:

• Hearing

• Language

• Secondary visual area

• Taste

Functional Areas of the Temporal lobe:

• Primary auditory cortex

  • Functional region in transverse temporal Gyrus

  • Processes auditory signals

• Secondary auditory cortex

  • Functional region i super and middle temporal gyri

  • Further processing of auditory signals

• Visual and Auditory association cortex

  • Further processes visual and auditory signals, respectively

• Wernicke’s area

Steps of Auditory function:

1. sound enters the ear

2. CN VIII transmits the sound to the brainstem

3. Various neurons within the brainstem relay the information to the thalamus

4. The thalamus relays the information to the primary auditory cortex

Occipital Lobe

• Gyri and Sulci

  • Lateral occipital Gyri

    • Collective name for gyri on lateral surface of occipital lobe

    • Vary widely per person

  • Calcarine Sulcus

    • Sulcus in middle of medial surface of occipital lobe

    • Separates cutaneous and lingual Gyrus

  • Cuneus

    • Gyrus superior to calcarine sulcus

  • Lingual Gyrus

    • Gyrus inferior to calcarine sulcus

    • Continuing into temporal lobe

Functional Areas of the occipital lobe:

• Primary visual crortex

  • Receives/initially processes visual information

  • Found in cuneus and lingual Gyrus

    • Especially portions nearest calcarine sulcus

• Visual association cortex

  • Found in remainder of the occipital lobe and partially in temporal lobe

  • Further processes visual information

Steps in visual functions:

1. Light strikes the retina and is concerted to action potentials

2. Action potentials travel through axons in the optic nerve, optic chiasm, and optic tract until reaching the thalamus and brainstem

3. From the thalamus, action potentials travel through the optic radiation until reaching the primary visual cortex

Limbic Lobe

• Gyri and Sulci

  • Cingulate Gyrus

    • Between cingulate sulcus and the corpus callosum

  • Parahippocampal gyri

    • Continuation of limbic lobe on medial surface of temporal lobe

    • Between diencephalon and collateral sulcus

    • Circles back on itself as the uncus

  • Paraterminal Gyrus

    • Small Gyrus anterioinferior to corpus callosum

  • Subcallosal Gyrus

    • Small Gyrus anterior to the paraterminal Gyrus

  • Cingulate sulcus

  • Subparietal sulcus

  • Collateral sulcus

Parts of the Limbic System present in the Temporal Lobe:

• Amygdala

  • Small portion of gray mater buried within the temporal lobe

  • Works with the limbic lobe and hippocampus

• Hippocampus

  • Strip of gray matter buried within the temporal lobe, deep to the parahippocampal Gyrus

Functions of the Limbic system:

• learning

• Memory

• Emotional response

• Drive-related behavior

• The uncus also contains the primary olfactory cortex

Steps in olfactory function:

1. Smells enter the nose and are detected by receptors associated with CN I

2. Action potentials are generated in CN I and transported into the cranial cavity

3. CN I synapses with the olfactory bulb on the undersurface of the frontal lobe

4. Action potentials travel int eh olfactory bulb and tract until reaching the uncus and nearby areas

Insula:

• Gyri and Sulci

  • Circular sulcus

    • Boundary of the insula

  • Short gyri

    • Within the insula that are relatively short and vertical

  • Long gyri

    • Within the insula that are relatively long and diagonal

Functions of the Insula:

• primary gustatory cortex

  • The part o the insula (and small portions of the temporal lobe) acting to process taste sensations

• Vestibular cortex

  • Overlaps the insula and the parietal operculum

  • Processes sensory information related to acceleration and rotation of the head

• Association cortex

  • Helps combine several senses together

Steps in Gustatory function:

1. Tastes are sensed by receptors i taste buds

2. CN VII, IX and X relay action potentials to brainstem

3. Action potentials travel in the brainstem to the thalamus

4. The thalamus sends action potentials to the insula

Steps in Vestibular Functions:

1. Acceleration and rotation are detected by structures in the inner ear, resulting in action potentials in CN VIII

2. CN VIII relays the action potential to the brainstem

3. Action potentials travel through several routes in th brainstem

   • One such route travels to the thalamus

4. Action potentials are sent form the thalamus to the vestibular cortex in the insula

Spinal Cord:

• Brainstem/spinal cord functions:

  • Connect brain to periphery

  • Provide route for long tracts (sensory, motor)

  • Various reflex and autonomics activities

  • Origin in of motor and sensory components of CN or spinal nerves

• Important features

  • Long, thin and conical structure

  • Fills superior 2/3 of vertebral column, ends between L1-L2 vertebrae

  • Cervical (C5-T1) and Lumbosacral (L2-S3) enlargements for nerves to limbs

  • Lumbar cistern

    • Continuation of meninges down to S2

    • Provides space with CSF but no spinal cord

  • Anterior and posterior median fissures

    • Long vertical groove separating the left and right laves of the spinal cord

    • The anterior spinal artery fills he anterior median fissure

  • Anterolateral and posterolateral sulci

    • Long vertical grooves

    • Contain the nerve rootlets

    • Posterior spinal arteries are found in the posterolateral sulci

  • Meninges

  • Spinal nerves

  • The spinal cord is divided into segments

    • Each segment is the space of the spinal cord giving rise to a single spinal nerve

    • The spinal cord segment is not necessarily at the same height as the vertebra of the same name

  • Conus Medullaris

    • Inferior end of spinal cord

    • In the adult, found at L1-2 level

  • Cauda Equina

    • Collection of nerves emerging form conus medullaris

Visible on a cross-section of the spinal cord:

• anterior and posterior median fissures

• Horns

  • Anterior, posterior, lateral

• Funiculi

  • Anterior, posterior, lateral

• Gracile and Cuneate fasciculi

  • Above T6, the posterior funiculus is subdivided into:

    • Gracile (medial)

    • Cuneate (lateral)

  • The posterior intermediate sulcus divides the funuculi

  • Gracile carries sensation from below T6

  • Cuneate carries sensations from T6 and above

• Anterior white commissure

  • Brief portion of white matter separating anterior median fissure form central canal

Parts of the Posterior horn:

• subdivided into 3 parts

  • Lissauer’s Tract

    • Superficial region

    • Carried fibers headed to substantia gelatinous a as well as fibers that interact with adjacent levels

  • Substantia Gelatinosa

    • Middle, pale

    • Contains neurons related to pain and temperature sensation

  • Body

    • Deep part of the horn

    • Contains inter neurons relaying somatic and visceral sensory information

  • Dorsal Root ganglion cells ready info about touch to the posterior funiculus