Brain Structure and Function Notes

Introduction

  • Structure (anatomy) vs. Function (physiology). Anatomy refers to the physical structures of the brain, while physiology describes how these structures function.

  • Seventeen brain structures will be covered in detail. Each structure plays a unique role in overall brain function.

Brains in Organisms

  • Animals have brains due to the presence of nerves and muscles, which facilitate movement and response to stimuli.

  • Brains organize movement by integrating sensory information and coordinating motor outputs.

Body Plans

  • Radially symmetrical organisms: Organized around a central axis (like a tire). These organisms typically have sensory organs distributed around their body.

  • Bilaterally symmetrical organisms: Exhibit clear right and left sides, as well as front and back. This body plan allows for more complex movement and behavior.

  • Sensory information input \rightarrow Integration in the brain \rightarrow Motor neuron output: This sequence illustrates the flow of information in bilaterally symmetrical organisms.

Primitive Brain Structure

  • Common structure in primitive brains:

    • Spinal cord: Transmits signals between the brain and the rest of the body.

    • Hindbrain: Controls basic life functions such as breathing and heart rate.

    • Midbrain: Involved in sensory processing and motor control.

    • Forebrain: Responsible for higher-level cognitive functions and emotional responses.

  • Shark brain retains this primitive structure, offering insights into the evolutionary development of the brain.

  • Functions closer to the spinal cord are more basic (e.g., heart beating, circulation). These functions are essential for survival.

  • Emotional responses originate in the forebrain, highlighting its role in regulating emotions.

  • Embryonic brains resemble this early structure, providing a glimpse into the developmental stages of the brain.

  • Adult brains have radically changed during development, especially the forebrain, which undergoes significant expansion and differentiation.

Brain Anatomy
Key Structures

  • Brainstem: Connects the brain to the spinal cord and controls basic life functions.

  • Cerebellum: Coordinates movement and motor control.

  • Thalamus and Hypothalamus: Relay sensory information and regulate homeostasis.

  • Cerebrum: Responsible for higher-level cognitive functions.

Brainstem

  • Composed of:

    • Medulla oblongata: Regulates breathing, heart rate, and blood pressure.

    • Pons: Relays signals between the cerebrum and cerebellum.

    • Midbrain: Involved in sensory processing and motor control.

  • Functions:

    • Basic needs: breathing, circulation, digestion, swallowing; these functions are essential for survival.

    • Routing and filtering sensory information; the brainstem acts as a gateway for sensory input.

  • Damage is catastrophic; injuries to the brainstem can result in severe disabilities or death.

Cerebellum

  • Function: Motor control and motor memory; the cerebellum plays a key role in coordinating movements.

  • Coordination in sports and learned skills like riding a bicycle; these activities require precise motor control.

Thalamus

  • Function: Sorts data and sends it where it needs to go (like a router); the thalamus acts as a relay station for sensory information.

Hypothalamus

  • Function: Homeostasis (body temperature, osmolarity), circadian rhythms; the hypothalamus helps maintain a stable internal environment.

Pituitary Gland

  • Posterior pituitary: Part of the brain, releases hormones; this gland plays a crucial role in hormone regulation.

  • Examples: Antidiuretic hormone, oxytocin; these hormones regulate fluid balance and social bonding.

Cerebrum

  • Function: Integration of data; making sense of information; the cerebrum is responsible for higher-level cognitive functions.

  • Made of billions of neurons and synapses, which form complex neural networks.

  • Functional MRI: Technology to observe brain activity; this technology measures blood flow changes in response to different stimuli.

Cerebral Hemispheres

  • Right and left hemispheres: The cerebrum is divided into two hemispheres.

  • Corpus callosum: Connects the two hemispheres, allowing them to communicate.

  • Lateralization: Certain functions are more dominant on one side; this specialization allows for efficient processing.

    • Left: Math, logic; the left hemisphere is typically dominant for analytical tasks.

    • Right: Facial recognition; the right hemisphere is often associated with spatial and visual processing.

  • Plasticity: Functions can move; hemispherectomy is possible; the brain can reorganize itself after injury.

Basal Ganglia

  • Nuclei: Clusters of neurons with the same function; these clusters work together to perform specific tasks.

  • Function: Motor control through complex interactions; the basal ganglia play a key role in regulating movement.

  • Parkinson's disease: Related to problems in the basal ganglia area; this disease affects motor control and coordination.

Cerebral Cortex

  • 80% of the brain, divided into four lobes:

Frontal Lobe

  • Executive functions, emotional control; the frontal lobe is responsible for higher-level cognitive processes.

  • Damage can cause emotional swings; injuries to the frontal lobe can result in mood changes.

Parietal Lobe

  • Sensation and reaction to the environment; the parietal lobe processes sensory information.

  • Sensory input; this lobe receives input from various sensory modalities.

Occipital Lobe

  • Vision; the occipital lobe is responsible for visual processing.

Temporal Lobe

  • Language, hearing, memory; the temporal lobe plays a key role in auditory processing and memory formation.

Somatosensory Cortex

  • Inside the parietal lobe, receives sensory information; this cortex processes tactile information.

Motor Cortex

  • On the other side of the lobe, sends motor output; the motor cortex controls voluntary movements.

  • Integration: Sensory input in \rightarrow Decision \rightarrow Motor output; this sequence illustrates the flow of information in the motor cortex.

  • Mapping the cortex: Uneven distribution of neurons related to sensitivity; different areas of the body have varying levels of sensitivity.

Structures and Functions Review
Brainstem

  • Three parts: medulla oblongata, pons, midbrain.

  • Functions:

    • Maintain basic life functions (breathing, heart rate, digestion).

    • Sort information.

Cerebellum

  • Coordination, motor control, and motor memory.

Thalamus

  • Sorts information to the cerebrum.

Hypothalamus

  • Homeostasis.

Posterior Pituitary
Cerebrum
Corpus Callosum

  • Connects hemispheres.

Basal Ganglia

  • Motor control.

Cerebral Cortex

  • Frontal lobe: executive function.

  • Parietal lobe: sensation.

  • Occipital lobe: vision.

  • Temporal lobe: language, hearing, memories