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Week 3 Modules - PSY10007_Central_Nervous_System_and_Brain

Concise Version

The Nervous System

  • Enables processing information from and interacting with the environment.

  • Organized into two divisions:

    • Central Nervous System (CNS)

    • Peripheral Nervous System (PNS)

Central Nervous System (CNS)

  • Consists of the brain and spinal cord.

  • Heavily protected by the skull and spinal vertebrae.

  • Constant two-way communication between the brain and spinal cord.

  • Spinal cord reflexes occur without direct brain involvement for rapid reactions.

Peripheral Nervous System (PNS)

  • Sits outside the skull and spinal vertebrae.

  • Connects to the spinal cord via nerves.

    • Afferent nerves:

      • Carry sensory signals from the external environment (skin, eyes, ears, etc.) to the spinal cord and brain.

    • Efferent nerves:

      • Carry motor signals from the brain to the muscles via the spinal cord.

  • Further divided into:

    • Somatic Nervous System

    • Autonomic Nervous System

Somatic Nervous System

  • Controls communication between nerves, muscles, spinal cord, and brain.

Autonomic Nervous System

  • Regulates the body's internal environment (heart, lungs, stomach, etc.).

  • Largely automatic.

    • Sympathetic System:

      • Activates internal organs (e.g., increased heart rate) for fight or flight.

    • Parasympathetic System:

      • Returns internal organs to their resting state.

Subcortical Structures of the Brain (Forebrain)

  • Give meaning to sensory stimuli and serve survival and basic functioning purposes.

  • Include the limbic system and thalamus in the forebrain, and the corpus callosum, among other structures in the midbrain and hindbrain.

Corpus Callosum

  • Thick bundle of fibers connecting the left and right hemispheres of the brain.

  • Enables communication between the two hemispheres.

  • Some brain functions are lateralized (controlled by a single hemisphere).

    • Broca's and Wernicke's areas: located in the left hemisphere

  • Without the corpus callosum, language functions controlled by Broca's and Wernicke's areas could not be translated into associated actions that require right hemisphere involvement.

Limbic System

  • Drives approach and withdrawal behaviors.

  • Regulates motivations and emotions.

    • Key structures:

      • Amygdala

      • Hippocampus

Amygdala

  • Drives fight or flight fear response.

  • Drives everyday motivations involving reward (e.g., food, sex).

Hippocampus

  • Stores memories of emotionally relevant events.

  • Interacts with the amygdala to evaluate stimuli and determine whether they should be approached or avoided.

  • People with Alzheimer's disease often have a smaller hippocampus.

Thalamus

  • Two-lobed structure.

  • Relay point for messages entering the brain via the sensors.

  • Determines the relative importance of sensory information and forwards it to the relevant parts of the brain for processing.

Hypothalamus

  • Small structure lying underneath the thalamus.

  • Regulates basic survival mechanisms: sleep, hunger, thirst, and sex drive.

  • Damage can have a profound effect on any or all of these basic mechanisms.

Cerebral Cortex

  • Wrinkly outer grey matter divided into two halves, supported by white matter and other structures.

  • Grey color due to the lack of myelinated neurons in the outer layer.

  • White matter contains more myelinated neurons, making processing quicker in deeper parts of the brain.

  • Where complex information processing occurs (abstract thought, planning, higher order cognitive processes).

  • Divided into four lobes:

    • Frontal lobe

    • Temporal lobe

    • Parietal lobe

    • Occipital lobe

Functional Areas of the Brain

  • Specific functions are narrowed down to specific regions of the cerebral cortex.

Association Cortex

  • Organizes information from several brain regions for meaningful interpretation.

Broca's Area

  • Central role in speech production.

  • Damage leads to difficulty speaking (inability to coordinate the muscles of the mouth and tongue).

Wernicke's Area

  • Central role in speech comprehension.

  • Damage leads to difficulty understanding language (sensory information cannot be integrated into a meaningful whole).

Prefrontal Cortex

  • Part of the association cortex.

  • Processes mental and cognitive qualities that rely on the integration of complex information (self-control, lying, understanding irony).

  • Lying involves integrating suppressing the truth, creating an alternative scenario, and monitoring others' responses.

Neuroplasticity

  • New skills can be developed by repurposing areas of the brain.

Brain Imaging Techniques

  • Provide access to the living and functioning brain.

  • Help psychologists hypothesize relationships between brain functioning, behavior, and mental processes.

Positron Emission Tomography (PET)

  • Picks up signals from radioactive substances to indicate changes in blood flow and/or glucose metabolism.

  • Blood flow and glucose metabolism correlate with neuronal activity (higher blood flow equals greater brain activity).

  • Can link specific behaviors to neuroanatomy.

  • Low temporal resolution (cannot detect rapid changes in brain function).

Functional Magnetic Resonance Imaging (fMRI)

  • Provides a higher resolution 3D image of the brain than PET.

  • Picks up more rapid changes in neuronal functioning.

  • Uses blood flow as a proxy for neural activity.

  • Picks up changes in natural substances in the brain (protons) using a large magnet.

  • Most widely used due to superior resolution.

Magnetoencephalography (MEG)

  • Uses powerful magnets to measure neural activity.

  • Higher temporal resolution than fMRI (can pick up faster brain processing signals).

  • Lower spatial resolution than fMRI (produces a lower resolution image of the brain).

  • Sometimes used in conjunction with fMRI.

Important Considerations

  • Brain function does not equate to behavior.

  • Behavior and mental processes result from interacting brain structures and functions working together in complex systems.

  • Imaging technologies provide a window into structure and function but cannot capture the complex systems necessary to fully understand how the brain relates to behavior.

  • Social, developmental, and cognitive processes also drive our everyday thoughts and behavior.

Additional Notes

  • Brain imaging techniques are significantly more complex and elaborate than the simple characterizations provided.

  • It is important to have a basic understanding of their strengths and their limitations, in particular, the way in which they relate to thoughts and behaviour.

More Detailed Version

  • Enables processing information from and interacting with the environment through a complex network of specialized cells and structures. This system is fundamental for perceiving, interpreting, and responding to stimuli, as well as for regulating bodily functions. It's responsible for everything from basic reflexes to complex thought processes.

  • Organized into two divisions:

    • Central Nervous System (CNS):

    • Consists of the brain and spinal cord, acting as the control center for the body. The brain is responsible for higher-level functions such as learning, memory, and conscious thought, while the spinal cord relays signals between the brain and the peripheral nervous system.

    • Heavily protected by the skull and spinal vertebrae, which provide a robust physical barrier against injury. The brain is further protected by the meninges and cerebrospinal fluid.

    • Constant two-way communication between the brain and spinal cord ensures that information is continuously processed and acted upon. This communication is vital for coordinating movements and responses.

    • Spinal cord reflexes occur without direct brain involvement for rapid reactions, allowing for quicker responses to immediate threats or stimuli. Examples include withdrawing from a hot surface.

    • Peripheral Nervous System (PNS):

    • Sits outside the skull and spinal vertebrae, connecting the central nervous system to the limbs and organs.

    • Connects to the spinal cord via nerves:

      • Afferent nerves:

      • Carry sensory signals from the external environment (skin, eyes, ears, etc.) to the spinal cord and brain, providing information about touch, vision, hearing, and other senses. These signals are crucial for perception and awareness.

      • Efferent nerves:

      • Carry motor signals from the brain to the muscles via the spinal cord, enabling movement and physical responses. These signals initiate muscle contractions and other motor activities.

    • Further divided into:

      • Somatic Nervous System:

      • Controls communication between nerves, muscles, spinal cord, and brain, allowing for voluntary movements and conscious control of skeletal muscles. It is responsible for actions we consciously decide to perform.

      • Autonomic Nervous System:

      • Regulates the body's internal environment (heart, lungs, stomach, etc.), controlling functions such as heart rate, digestion, and breathing. It operates largely without conscious control.

      • Largely automatic:

        • Sympathetic System:

        • Activates internal organs (e.g., increased heart rate, dilated pupils, and inhibited digestion) for fight or flight responses, preparing the body to face threats or flee from danger. This system increases alertness and energy.

        • Parasympathetic System:

        • Returns internal organs to their resting state, promoting relaxation, digestion, and energy conservation. It counteracts the effects of the sympathetic system.

Subcortical Structures of the Brain (Forebrain)

  • Give meaning to sensory stimuli and serve survival and basic functioning purposes, playing a critical role in emotions, motivations, and homeostasis.

  • Include the limbic system and thalamus in the forebrain, and the corpus callosum, among other structures in the midbrain and hindbrain. These areas work together to ensure proper functioning of the nervous system.

Corpus Callosum

  • Thick bundle of fibers connecting the left and right hemispheres of the brain, facilitating communication and coordination between the two sides. This allows for integrated processing of information.

  • Enables communication between the two hemispheres, allowing them to work together on a variety of tasks.

  • Some brain functions are lateralized (controlled by a single hemisphere):

    • Broca's and Wernicke's areas: located in the left hemisphere, these are critical for language processing.

  • Without the corpus callosum, language functions controlled by Broca's and Wernicke's areas could not be translated into associated actions that require right hemisphere involvement, highlighting the importance of inter-hemispheric communication.

Limbic System

  • Drives approach and withdrawal behaviors, guiding us towards beneficial stimuli and away from harmful ones. It plays a key role in survival and adaptation.

  • Regulates motivations and emotions, influencing our feelings and desires:

    • Key structures:

    • Amygdala:

      • Drives fight or flight fear response, helping us to recognize and respond to threats.

      • Drives everyday motivations involving reward (e.g., food, sex), encouraging behaviors that promote survival and reproduction.

    • Hippocampus:

      • Stores memories of emotionally relevant events, creating a record of experiences that can inform future behavior.

      • Interacts with the amygdala to evaluate stimuli and determine whether they should be approached or avoided, combining emotional and cognitive information.

      • People with Alzheimer's disease often have a smaller hippocampus, leading to memory impairments.

Thalamus

  • Two-lobed structure, acting as a central hub for sensory information.

  • Relay point for messages entering the brain via the sensors, directing information to the appropriate areas for processing.

  • Determines the relative importance of sensory information and forwards it to the relevant parts of the brain for processing, ensuring that important information receives priority.

Hypothalamus

  • Small structure lying underneath the thalamus, regulating essential bodily functions.

  • Regulates basic survival mechanisms: sleep, hunger, thirst, and sex drive, ensuring that these critical needs are met.

  • Damage can have a profound effect on any or all of these basic mechanisms, highlighting its critical role in maintaining homeostasis.

Cerebral Cortex

  • Wrinkly outer grey matter divided into two halves, supported by white matter and other structures. This complex structure is responsible for higher-level cognitive functions.

  • Grey color due to the lack of myelinated neurons in the outer layer, indicating a high density of cell bodies and synapses.

  • White matter contains more myelinated neurons, making processing quicker in deeper parts of the brain, as myelin facilitates faster transmission of electrical signals.

  • Where complex information processing occurs (abstract thought, planning, higher order cognitive processes), allowing for sophisticated reasoning and decision-making.

  • Divided into four lobes:

    • Frontal lobe:

    • Responsible for executive functions, planning, and voluntary movement.

    • Temporal lobe:

    • Involved in auditory processing, memory, and language comprehension.

    • Parietal lobe:

    • Processes sensory information such as touch, temperature, and pain.

    • Occipital lobe:

    • Dedicated to visual processing.

Functional Areas of the Brain

  • Specific functions are narrowed down to specific regions of the cerebral cortex, allowing for specialized processing of information.

Association Cortex

  • Organizes information from several brain regions for meaningful interpretation, integrating sensory, motor, and cognitive information to create a coherent understanding of the world.

Broca's Area

  • Central role in speech production, coordinating the muscles necessary for speaking.

  • Damage leads to difficulty speaking (inability to coordinate the muscles of the mouth and tongue), resulting in expressive aphasia.

Wernicke's Area

  • Central role in speech comprehension, allowing us to understand spoken and written language.

  • Damage leads to difficulty understanding language (sensory information cannot be integrated into a meaningful whole), resulting in receptive aphasia.

Prefrontal Cortex

  • Part of the association cortex, responsible for higher-level cognitive functions.

  • Processes mental and cognitive qualities that rely on the integration of complex information (self-control, lying, understanding irony), enabling sophisticated social interactions and decision-making.

  • Lying involves integrating suppressing the truth, creating an alternative scenario, and monitoring others' responses, requiring complex cognitive processing.

Neuroplasticity

  • New skills can be developed by repurposing areas of the brain, demonstrating the brain's ability to adapt and change over time.

Brain Imaging Techniques

  • Provide access to the living and functioning brain, allowing researchers to study brain activity in real-time.

  • Help psychologists hypothesize relationships between brain functioning, behavior, and mental processes, linking neural activity to cognitive and behavioral outcomes.

Positron Emission Tomography (PET)

  • Picks up signals from radioactive substances to indicate changes in blood flow and/or glucose metabolism, providing insights into brain activity levels.

  • Blood flow and glucose metabolism correlate with neuronal activity (higher blood flow equals greater brain activity), serving as indicators of neural activity.

  • Can link specific behaviors to neuroanatomy, identifying which brain regions are involved in particular tasks.

  • Low temporal resolution (cannot detect rapid changes in brain function), limiting its ability to capture fast-paced brain processes.

Functional Magnetic Resonance Imaging (fMRI)

  • Provides a higher resolution 3D image of the brain than PET, allowing for more detailed localization of brain activity.

  • Picks up more rapid changes in neuronal functioning, making it suitable for studying dynamic brain processes.

  • Uses blood flow as a proxy for neural activity, similar to PET but with better resolution.

  • Picks up changes in natural substances in the brain (protons) using a large magnet, detecting variations in blood oxygen levels.

  • Most widely used due to superior resolution, providing detailed and accurate images of brain activity.

Magnetoencephalography (MEG)

  • Uses powerful magnets to measure neural activity, directly detecting the electrical activity of neurons.

  • Higher temporal resolution than fMRI (can pick up faster brain processing signals), making it ideal for studying rapid brain processes.

  • Lower spatial resolution than fMRI (produces a lower resolution image of the brain), limiting its ability to precisely localize brain activity.

  • Sometimes used in conjunction with fMRI to combine high temporal and spatial resolution, providing a more complete picture of brain activity.

Important Considerations

  • Brain function does not equate to behavior; behavior arises from complex interactions between multiple brain regions and other factors.

  • Behavior and mental processes result from interacting brain structures and functions working together in complex systems, highlighting the importance of studying the brain as a whole.

  • Imaging technologies provide a window into structure and function but cannot capture the complex systems necessary to fully understand how the brain relates to behavior, emphasizing the need for a multidisciplinary approach.

  • Social, developmental, and cognitive processes also drive our everyday thoughts and behavior, interacting with brain functions to shape our experiences.

Additional Notes

  • Brain imaging techniques are significantly more complex and elaborate than the simple characterizations provided, requiring specialized knowledge and expertise to interpret the results.

  • It is important to have a basic understanding of their strengths and their limitations, in particular, the way in which they relate to thoughts and behaviour, to critically evaluate research findings and avoid oversimplifications.