Cerebral Cortex Overview

Cerebral Cortex

• Consists of three functional areas: motor, sensory, and multimodal association
• Motor areas include the primary motor cortex, premotor cortex, and Broca's area
• All neurons in the cerebral cortex are interneurons

Motor Areas

• Primary motor cortex controls individual movements or sequences of movements requiring multiple muscle groups
• Premotor cortex sends axons to the primary motor cortex and spinal cord, performing more complex task-related processing
• Broca's area is involved in speech production

Sensory Areas

• Primary somatosensory cortex detects sensory information from the body including temperature, proprioception, touch, texture, and pain
• Somatosensory association cortex integrates sensory inputs received from the primary somatosensory cortex, leading to an understanding of the object being felt

Multimodal Association Areas

• Receive input from multiple senses and output to multiple areas
• Help us give meaning to information received, store it in memory, tie it to previous experience, and decide on actions
• Include the Anterior association area (prefrontal cortex), Posterior association area, and Limbic association area.

Blood Brain Barrier

• Helps maintain a stable environment in the brain by preventing exposure to chemical variations that may influence neuronal firing
• Tight junctions between capillary endothelial cells create an exceptionally impermeable barrier
• Substances in the blood must pass through three layers before reaching neurons
• Permeability is selective, some substances can diffuse easily and affect the brain.

Meninges and Spinal Cord

• Meninges cover the spinal cord
• Nerves exit at the level of each vertebrae
• Dorsal root is associated with the dorsal root ganglia, cell bodies outside the central nervous system
• Ventral root carries motor information
• Spinal cord's gray matter consists of sensory and motor nuclei
• White matter consists of axons carrying information to and from the brain.
• Ascending axons carry sensory inputs up to higher centers
• Descending axons carry motor outputs down to lower centers
• Transverse axons transfer information across the cord.

Neuron Synapse

• Axonal terminals contain vesicles with neurotransmitters
• Axon terminals are separated from the next neuron by the synaptic cleft
• Synapse refers to the junction between nerves

Transmission at Chemical Synapses

• A single axon can have multiple branches, synapsing on various postsynaptic cells
• A single neuron receives thousands of synaptic inputs from multiple presynaptic neurons
• Synaptic vesicles contain neurotransmitters
• Action potentials activate voltage-gated calcium channels in the axon terminal membrane
• Calcium influx triggers fusion of synaptic vesicles with the membrane and neurotransmitter release into the synaptic cleft
• Neurotransmitter binds to receptors on the postsynaptic cell, opening or closing ion channels
• This change in ion permeability leads to an excitatory postsynaptic potential (EPSP) if the cell is made more likely to fire or an inhibitory postsynaptic potential (IPSP) if it is made less likely to fire

Signal Termination

• Neurotransmitters are cleared from the synaptic cleft by different mechanisms:
  • Enzymatic degradation (e.g. acetylcholine)
  • Reuptake into the presynaptic neuron for recycling (e.g. serotonin)

Supporting Cells (Glial Cells) of the Nervous Tissue

• Besides neurons, the CNS also contains several different cell types including:
  • Astrocytes
  • Microglia
  • Ependymal cells
  • Oligodendrocytes

Neurotransmitters

• Play a role in emotion, hunger, satiation, memory, movement, and even smiling
• Over 50 neurotransmitters have been identified
• Some neurons produce and release one type of neurotransmitter, while most produce two or more
• Can be classified by chemical structure or function
• Norepinephrine is generally excitatory and involved in vigilance and attentiveness
• Dopamine is involved in reward, movement, and motivation.
• Serotonin is involved in mood, sleep, and appetite
• Different receptors, including ionotropic and metabotropic receptors, bind to neurotransmitters and mediate their effects.

Heteroreceptors

• Receptors on the presynaptic terminal of one neuron that are activated by a neurotransmitter released from another neuron
• They modulate the release of the neurotransmitter from that presynaptic terminal

Autoreceptors

• Receptors located on the presynaptic terminal of a neuron that bind to the neurotransmitter released by that same neuron
• They typically have an inhibitory effect, reducing the release of the neurotransmitter.

The Reward System

• A group of structures that are activated when we experience something rewarding
• Major components and functions:
  • Ventral tegmental area (VTA): Produces dopamine
  • Nucleus accumbens: Receives dopamine and is involved in pleasure and motivation
  • Amygdala: Processes emotions, including fear and reward
  • Hippocampus: Involved in memory formation
  • Prefrontal cortex: Controls executive functions, including decision-making, planning, and impulse control

Explore the key functional areas of the cerebral cortex, including motor, sensory, and multimodal association areas. Learn about the roles of the primary motor cortex, Broca's area, and the primary somatosensory cortex. This quiz will test your understanding of how these regions contribute to brain function.