NROB60 Neuroanatomy Lab 1: Sheep Brain I Notes

Introduction to Neuroanatomy Lab

  • This lab serves as a guide to practical sessions, providing essential content for hands-on neuroanatomy training.
  • The practical sessions aim to familiarize students with mammalian brain structures through experiential learning.
  • Students will explore neuroanatomical structures and cell types across different species (sheep, human, rodent) using dissections, microscope images, and staining techniques.
  • The material should be approached as learning a new language or reading a map, developing 3D spatial awareness of brain structures.
  • Weekly assessments called "Bellringer"-style quizzes will cover the previous session's material, consisting of five questions with one minute per question.
  • Details about the quizzes are available on Quercus or from the TAs.
  • A translational project involving a comparative analysis of a brain region and/or neural circuit across different species will be conducted to apply learning and highlight evolutionary and functional differences in neuroanatomy.

Acknowledgements

  • The weekly content was developed by Dr. Debra Bercovici, with input from Elfin Akteke (former 2024 NROB60 student).
  • Images and content for Labs 1-3 are adapted from J. LeBoutillier's (2022) Sheep brain atlas: A photographic guide [Laboratory Manual], NROB60, University of Toronto Scarborough.

Lab Expectations & Safety

  • Practical sessions should be informative, encourage scientific and logical thinking, and be enjoyable.
  • Students should approach each lab with curiosity and collaboration.
  • Students are expected to follow directions in the lab manual and from TAs.
  • TAs have the right to override anything written in the lab manual through verbal instructions or email.
  • The instructor should be contacted directly for any course difficulties.

Safety Protocols

  • Adherence to lab safety protocols is mandatory for a safe and effective learning environment.
  • Failure to follow guidelines may result in exclusion from the lab.
    • Protective Equipment:
      • A lab coat and closed-toe shoes must be worn at all times.
      • Disposable gloves are required when handling brain specimens.
      • Safety goggles and masks are recommended for additional protection.
    • Food and Personal Items:
      • No food or drink is allowed in the lab.
      • Personal devices should be kept away from the lab bench to prevent contamination; if used, they should be placed in a disposable plastic bag.
    • Specimen Handling:
      • Brain tissue must remain within the lab and should not be removed from dissecting trays or the lab space.
      • Dispose of all brain tissue in the designated animal waste container.
    • Cleanup Procedures:
      • Rinse and stack dissecting trays in the designated area.
      • Rinse dissection tools and place them in the assigned bins.
      • Wipe down the lab bench with ethanol to maintain a clean workspace.

Lab 1: Sheep Brain I

  • This practical session marks the beginning of hands-on neuroanatomy training through dissection and exploration of a sheep brain.
  • Over the next three sessions, students will work in groups to examine key structures, develop spatial awareness of brain organization, and prepare for quizzes.
  • The sessions aim to be interactive and build confidence in identifying neuroanatomical features.

Objectives

  • Understand and employ anatomical terminology about direction, characteristics, and planes to orient within the brain.
  • Identify external features of the dorsal, lateral, and ventral surfaces.
  • Prepare for the next week’s quiz by memorizing and identifying the above concepts.

Getting Set Up

  • Students will work in groups of approximately three.
  • For the first three weeks, a sheep brain will be handled; students should grab a jar to store the brain, labeling the lid with names and practical section.

Anatomical Terminology

  • The brain's exterior will be examined by rotating it to observe different perspectives. The Dura Mater needs to be removed.
  • Reviewing anatomical terminology is helpful before removing the Dura Mater.
  • Standardized directional terms and planes of orientation help describe the position of structures relative to one another.

Directionality Terms

  • Anterior/Rostral: Towards the head or front
    • Anterior comes from Ante (before)
    • Rostral means beak
  • Posterior/Caudal: Towards the back end, rear, or tail
    • Posterior comes from Post (after)
    • Caudal means tail
  • Dorsal/Superior: Up, on top of, the top side, or relating to the back
    • Dorsal comes from Dorsum (back)
    • Think of a shark’s dorsal fin
  • Ventral/Inferior: Down, below, or on the bottom
    • Ventral comes from Venter (belly)
  • Medial/Nasal: Towards the midline (towards the middle of the body)
    • Medial comes from Medius (middle)
    • Nasal means nose
  • Lateral/Temporal: Away from midline (situated out to the side)
    • Lateral comes from Latus (side)
    • Temporal means temple
  • Ipsilateral: On the same side of the body
    • From Ipsi (self or same)
    • E.g., right eye and right ear are ipsilateral to each other
  • Contralateral: On the opposite side of the body
    • From Contra (against, opposite to)
    • E.g., right eye and left eye are contralateral to each other

Neuroanatomical Characteristics

  • Gyrus (plural = gyri): the “hill” or convolution on the surface of the brain
    • Caused by the folding of the cortex
  • Sulcus (plural = sulci): the “valley” or cleft on the surface of the brain
    • Separates the gyri
  • Fissure: a deep sulcus
    • An elongated cleft
    • A natural division of the brain
  • Lissencephalic: a brain in which the cerebral hemispheres are devoid of gyri and clefts sulci
    • Comes from lissos = smooth; enkephalos = brain
  • Gyrencephalic: a brain in which the cerebral hemispheres are highly folded and convoluted
    • Comes from gyros = spiral; enkephalos = brain
  • Grey matter: consists of neuronal cell bodies and dendrites
  • White matter: composed of bundles of myelinated axons
    • Appears white to the naked eye because myelin is primarily composed of lipid (fat)!

Planes of Orientation

  • Note how each plane is perpendicular to the other planes!
    • Sagittal plane: vertical plane that divides the brain into right and left parts
      • Division is parallel to the midline
    • Horizontal (Transverse) plane: divides the brain into dorsal and ventral
      • Division is perpendicular to the midline
      • Often what is seen in MRI scans
    • Coronal (Frontal) plane: vertical plane that divides the brain into anterior and posterior
      • Corona comes from “crown”

Dissection: Removing the Dura Mater

  • The meninges are the three protective layers of connective tissue that surround the brain and spinal cord.
  • They provide structural support, help circulate cerebrospinal fluid (CSF), and act as a barrier against infections and injuries.
  • The three layers, from outermost to innermost, are:
    1. Dura Mater: The tough, outermost layer that provides strong protection. It is thick and fibrous, anchoring the brain to the skull.
      • When looking at your brain, this is the thick white covering
    2. Arachnoid Mater: The middle layer, which has a web-like structure. It contains the subarachnoid space, where cerebrospinal fluid circulates, cushioning the brain.
    3. Pia Mater: The thin, innermost layer that directly adheres to the brain and spinal cord, following their contours and supplying blood vessels.

Procedure

  1. Use your scissors, forceps, and dissection probe, gently remove the dura mater from the dorsal surface only.
  2. To remove the dura mater from the ventral surface, you will also need to remove the pituitary gland (hypophysis) without damaging the cranial nerves. Orient the brain with the ventral surface facing up. Identify the pituitary gland, a darker-colored bulb located at the center of the ventral surface. With your fingers, carefully lift dura at the edges, noting how it is attached to several cranial nerves.
  3. Use your scissors to carefully snip the cranial nerves as close to the dura mater as possible, preserving their structure for closer examination later. Repeat this process for each nerve until the dura mater and pituitary gland can be lifted off the brain without resistance. Once removed, the nerves should be clearly visible.

External Features of the Sheep Brain

  • Responsibility for identifying by memory the gross anatomy (whole brain) on the dorsal, lateral, and ventral surfaces.

Dorsal View

  • General Landmarks
  • Major Gyri
  • Major Sulci
    • Medial longitudinal fissure
    • Endomarginal sulcus
    • Marginal sulcus
  • Frontal Major Gyri and Sulci
    • Coronal sulcus
    • Precoronal gyrus
    • Ansate sulcus
    • Ectomarginal sulcus
    • Suprasylvian sulcus
Prefix definitions:
  • Endo - within
  • Ecto-outer/external
  • Supra-above/over

Lateral View

  • Major Sulci
    • Sylvian sulcus
    • Diagonal Sulcus
  • Major Structures
    • Rhinal Fissure
    • Presylvian sulcus
    • Pyriform lobe
    • Uncus (Periamygdaloid cortex)
    • Lateral olfactory tract
    • Presylvian gyrus

Ventral View

  • Olfactory bulb
  • Olfactory tract
  • Olfactory tubercle
  • Pyriform Lobe
  • Uncus
  • Tuber cinereum
  • Infundibulum
  • Mammillary body
  • Midbrain
  • Pons
  • Trapezoid body
  • Olive
  • Pyramidal tract
  • Ventral median fissure

Bellringer Quiz Preparation

  • Starting next week, a 5-minute bellringer-style quiz will be conducted at the beginning of the practical session.

Guidelines:

  1. Paper Provided: A piece of paper will be provided to write the answers on.
  2. Format: The TA will display approximately five questions, one at a time, using a slideshow.
  3. Timing: You’ll have 60 seconds per question. When time is up (“the bell rings”), the slide will automatically change to the next question—so manage your time wisely!
  4. Be Specific: Use the most specific anatomical name possible in your answers. For example, write trapezoid body instead of just medulla.
  5. Spelling Matters: Spelling must be correct to earn full marks.
Writing Tools:
  • It is strongly recommended that you write in pen.
  • You may use pencil at your own risk. However, no regrades will be given for answers written in pencil.