Brain Structure and Function Quiz

Brain Structure and Function

• Brain is the "nerve center," containing billions of neurons transmitting information from body and environment, and generating responses (conscious and unconscious movements, thoughts, emotions, memories).
• Brain performs multiple tasks simultaneously (e.g., throwing a ball, talking, planning dinner while shopping, daydreaming).
• Brain's multitasking ability stems from distinct regions specialized for specific tasks.

Major Brain Landmarks

• Cerebrum is the largest part, divided into two hemispheres connected by the corpus callosum (nerve fibers).
• Cerebral cortex is the deeply folded surface layer of the cerebrum increasing processing power due to increased neuron surface area.
• Neuroscientists use divisions (lobes) to identify specific regions with unique functions.

Brain Lobes

• Frontal Lobes: Located above eyes; coordinate voluntary movements, speech, memory, emotions, higher cognitive skills (planning, problem-solving), and personality.
• Parietal Lobes: Located behind frontal lobes; integrate sensory signals from skin, process taste and visual information.
• Occipital Lobes: Located at the back of the brain; process visual information, recognizing colors, shapes, and complex visual understanding.
• Temporal Lobes: Located on sides of the brain; process visual and auditory information. The hippocampus within encodes new memories, and the amygdala integrates memories and emotions.

Limbic System

• Limbic system is a deep group of structures (thalamus, hypothalamus) within the forebrain; regulates emotions and motivation.
• Thalamus integrates sensory information and relays it to other brain regions.
• Hypothalamus regulates hormonal signals through the pituitary gland.

Midbrain

• Midbrain is located beneath the thalamus; coordinates eye movements (blinking, focusing), triggers reflexes.
• Inhibits unwanted body movements; coordinates sensory and motor input, enabling fine motor control (writing, playing instruments).
• Part of basal ganglia, which regulates complex body movements.

Hindbrain

• Hindbrain plays roles in glucose regulation, sleep, and movement control.
• Cerebellum (second-largest part by volume) coordinates voluntary movements, learning motor skills, spatial and temporal perception. Damage can cause jerky gait or inability to touch finger to nose.
• Pons influences breathing and posture.
• Medulla carries pathways connecting brain and spinal cord; controls basic functions (swallowing, heart rate, breathing); part of brainstem along with midbrain and pons.

Neural Networks

• Information travels between brain regions via chains of neurons called neural networks.
• Nerve tracts (bundles of neurons) include corpus callosum and anterior commissure.
• Neural networks route signals through the brain for analyzing and organizing information quickly.
• Explains how brain processes movie watching.

Brain Waves

• Brainwaves are rhythmic electrical patterns (detected by EEG) produced by looping neuronal signals through thalamus and cortex.
• Four distinct types: alpha (relaxed, eyes closed), beta (sensory input/concentration), theta (sleep), and delta (deep sleep).
• Each type has characteristic frequencies (Hz) and amplitudes (strength).

Neural Circuits

• Each brain region analyzes a specialized part of incoming information.
• Local neural circuits (interconnected neurons) transform input into output patterns.
• Signals travel down a chain of neurons in a circuit.
• Each column likely dedicated to one specific processing task, but influences of neighboring circuits.

Neurons

• Neurons are excitatory or inhibitory.
• Majority (80%) are excitatory, pushing neighboring neurons to fire (e.g., pyramidal cells).
• Remaining 20% are inhibitory, regulating circuit activity.
• Interplay of excitatory/inhibitory neurons in learning and smoothing signals.
• Epilepsy linked to imbalances in excitatory/inhibitory neurons.
• Circuits can be feed-forward (inhibitory signals to adjacent columns) or feedback (signals to downstream neighbors).

Glia

• Glial cells (astrocytes, microglia, ependymal cells, oligodendrocytes) support neurons.
• Recent studies show ratio of glia to neurons closer to 1:1 in some regions.
• Astrocytes regulate ion concentrations, provide nutrients and new connections.
• Microglia are immune cells, protecting brain from infections and damage.
• Ependymal cells produce cerebrospinal fluid.
• Oligodendrocytes wrap axons in myelin.

Ion Channels and Action Potentials

• Ions cross neuron membranes through ion channels.
• Resting neuron membrane potential (-70 mV) is affected by signals from other neurons.
• Action potential (electrical impulse) triggered when signals reach threshold.

Synapses and Neurotransmission

• Signals pass from one neuron to another at synapses (axon terminal, dendrite, synaptic cleft).
• Neurotransmitters (chemical signals) cross the synaptic cleft.
• Action potential triggers calcium influx that releases neurotransmitters from synaptic vesicles.
• Different neurotransmitters include amino acids, gases, small organic chemicals, peptides.
• Neurotransmitters bind to receptors on the postsynaptic membrane (ionotropic, metabotropic), altering postsynaptic membrane voltage.

Receptors and Molecular Signaling

• Receptors recognize diverse molecules (hormones, neuromodulators, prostaglandins).
• Hormones can diffuse through cell membrane or bind to intracellular receptors.
• Signal transduction pathways internally modify neuronal function.

Neurons, Genes, and Gene Expression

• Neurons differ based on gene expression –building different proteins.
• Genes determine neuron sensitivity to specific neurotransmitters and neuromodulators.
• Protein and DNA complex (chromatin) affects gene activation/inhibition.
• Gene variations can lead to neurological diseases.

Brain Evolution

• Human brain evolved from a simple tube.
• Early vertebrates had simpler brains with specialized regions.
• The brain has developed from a simple tube into the complex structure we know today.