Week 2 Lecture Notes

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School

University of Toronto, Scarborough *

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B60

Subject

Anatomy

Date

Oct 30, 2023

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docx

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Week 2 Lecture Notes – Gross Anatomy and Cranial Nerves Lobes - Named according to the overlying bones of the scull. Each lobe is functionally Distinct - Frontal Lobe: reasoning, decision making, motor control, emotion, speech production - Parietal lobe: processing of sensory information from the body - Occipital lobe: Vision - Temporal lobe: hearing, memory, emotion, speech comprehension Gray Matter Structures - Buried deep within the cerebral hemispheres. - Interconnect with each other - Form two important brain systems that contribute to a wide variety of our behaviors: the basal ganglia and the limbic system The basal Ganglia - Important In movement - A group of forebrain nuclei found deep in the cerebral hemispheres - Includes: Caudate nucleus, putamen, globus pallidus, subthalamic nucleus and substantia nigra - Not visible unless looking at a section of the brain - Best viewed on a coronal or horizontal plane The limbic system - Emotional processing, learning and memory - Loosely defined, widespread network - Includes hippocampus, cingulate gyrus, fornix, septal nuclei, stria terminalis, olfactory bulb, amygdala, mammillary bodies. - Some structures can be viewed on the ventral surface: olfactory bulb and mammillary bodies - Some can be viewed from midsagittal half-brain: cingulate gyrus, fornix, mammillary body - Others can be seen from coronal and horizontal sections of the brain

The cerebellum and the brainstem - Easily distinguishable The brainstem - Collectively refers to the midbrain, pons (metencephalon with the cerebellum) and medulla (myelencephalon) - Surface of each brainstem is characterized by bumps and bulges which separate the main areas. - Major subdivisions can be viewed on the midsagittal brain - Brainstem is rostrally continuous with the diencephalon - Diencephalon consists of thalamus and hypothalamus - Thalamus: involved in processing, relaying, and regulating information to and from the cerebral cortex. - Hypothalamus – involved in hunger, thirst, temperature regulation, sex and controls the pituitary gland. Some anatomists include the diencephalon as part of the brainstem. For this course it is considered the midbrain, pons and medulla. Midbrain: sensory (vision and hearing) and motor components Pons: Motor coordination, connected to the cerebellum Medulla: Vital basic body functions Functions of the brainstem - 1. A target for cranial nerves; provides local circuits that integrate afferent signals and coordinate efferent signals. The cranial nerves attach here and synapse onto nuclei. - 2. Provides a “throughway” for all ascending sensory tracts and descending motor tracts from forebrain - 3. Involved in regulating consciousness. Controls cortical activity. Understanding anatomy is essential for neurological diagnosis.

The midbrain - The most rostral end of the brain stem - Connects the cerebrum to the pons and cerebellum - Cerebral peduncles AKA the crux cerebri of the midbrain carry axons of the large descending motor pathway from the motor cortex . Voluntary movement travels down to the cerebellum from here. - Peduncle is a term used for a major band of white matter tracts joining different parts of the brain - Cerebral peduncle (aka crus cerebri or cerebral crus) contains fibers originating in the motor cortex and destined for the spinal cord, pons, or motor nuclei of certain cranial nerves, Dorsal surface of the Midbrain - Contains 4 rounded bumps known as the corpora quadrigemina - Superior colliculus: top two bumps, for vision - Inferior colliculus: bottom two bumps, for audition Major parts of the midbrain are three - Cerebral peduncles Tectum - the dorsal surface of the midbrain, structures dorsal to the cerebral - aqueduct - • Superior colliculus – the higher two bumps, involved in visual processing - • Inferior colliculus – the lower two bumps, involved in auditory processing

- • Corpora quadrigemina (aka quadrigeminal bodies) - all 4 bumps Breaking down meaning of words: - superior means “above” and inferior means “below” - Colliculus (plural: colliculi) means “a small protrusion” - Corpus (plural: corpora) = main part or body” of a structure - “quad” =4, Tectum refers to the corpora quadrigemina and other structures doesal to the cerebral aqueduct. Tegmentum: - the rest of the midbrain, structures ventral to the cerebral aqueduct The pons - Heavily involved in motor coordination through its connections to the cerebellum - Pons means bridge - The pontine nuclei primarily receive input from the cerebral cortex and project it onto the cerebellum The pons cerebellar peduncles - Superior - Middle cerebellar peduncle (largest one and sits more laterally) - Inferior From a ventral surface: only the middle cerebellar peduncle is visible.

The cerebellum - Central regulation of movement (balance and posture) - Smaller hemispheres connected by the vermis - Convoluted to increase surface area - Dorsal to the pons The cerebellum is ipsilateral – the left side of the cerebellum controls the left side of the body The medulla - Most caudal portion of the brainstem - Involved in basic body functions - Damage can be fatal - Any axons passing from brain to spinal cord pass through the medulla - Cranial nerves in the medulla regulate basic life functions. This is why damage here is so fatal. Inferior Olive – involved in motor control. Major source of input to the cerebellum. Smallest groove on the lateral edge. Pyramids (Aka medullary pyramids, pyramidal tract) – carries the major descending motor tracts. A continuation of the cerebral peduncles. Anterior median fissure (aka ventral median fissure) – a deep midline groove The medulla marks the transition between brainstem and spinal cord The reticular formation - Distributed network of neurons involved in consciousness and motor control - From midbrain to medulla. Even goes a little into the diencephalon. - No clear borders – hard to define. - Rostral portion modulates forebrain. Consciousness – involved in sleep and wakefulness. Regulates what will make it to the forebrain/to the conscious level. - Caudal portion – motor control

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