Neurons, Brain Structure, and Nervous System Lecture Notes

Comprehensive practice flashcards covering cellular neurobiology, neurotransmission, nervous system organization, genetics, brain structures, cortical lobes, plasticity, research techniques, and common brain myths.

What is a neuron?

A cell in the nervous system that communicates with other neurons to perform information-processing tasks, acting as the basic building block from which thoughts, feelings, and behaviors arise.

What are the three basic parts of a neuron?

The cell body (soma), dendrites, and axon.

What is the cell body (soma) and what is its role?

The largest part of a neuron that keeps the cell alive, coordinates information-processing tasks, and houses the nucleus containing DNA.

What is the primary function of dendrites?

To receive information from other neurons and relay that information to the cell body.

What is the primary function of an axon?

To carry information away from the cell body toward other neurons, muscles, or glands.

What is the myelin sheath and how does it affect neuronal communication?

An insulating layer of fatty material covering many axons that increases the speed and efficiency of information transmission.

What are glial cells and what roles do they perform?

Support cells in the nervous system that provide physical and nutritional support, digest parts of dead neurons, and form the myelin sheath around axons.

What happens when the myelin sheath deteriorates?

Communication between neurons becomes slower, leading to demyelinating diseases such as multiple sclerosis that impair feeling, movement, vision, and cognition.

What is a synapse?

The junction or region between the axon of one neuron and the dendrite or cell body of another, across which information is transmitted.

What are the three major types of neurons?

Sensory neurons, motor neurons, and interneurons.

What is the function of sensory neurons?

They receive information from the external world (detecting light, sound, touch, taste, and smell) and convey it to the brain via the spinal cord.

What is the function of motor neurons?

They carry signals from the spinal cord to muscles to produce movement.

What is the function of interneurons?

They connect sensory neurons, motor neurons, and other interneurons, making up most of the nervous system to perform information-processing functions.

What is the basic direction of information flow within a neuron?

Information moves from dendrites to the cell body, then down the axon to the synapse, and finally to the next neuron.

What is the resting potential of a neuron and its typical charge value?

The electrical charge difference across a neuron's cell membrane when at rest, typically measuring around $-70\text{ mV}$ inside relative to outside.

Which ions create the negative charge inside a resting neuron?

A higher concentration of $K^+$ and negatively charged protein ions inside, compared to a higher concentration of $Na^+$ outside the membrane.

What is an action potential?

An electrical signal that travels down the length of a neuron's axon toward the synapse.

What does the 'all-or-nothing' principle of an action potential mean?

If electrical stimulation is below threshold, no action potential occurs; if stimulation reaches or passes threshold, the action potential fires at full, fixed strength.

How do sodium ($Na^+$) ions propagate an action potential down the axon?

Reaching threshold causes $Na^+$ channels to open and $Na^+$ to rush in, altering electrical charge and triggering nearby sodium channels in a domino effect down the axon.

What are the nodes of Ranvier?

Small breaks between sections of the myelin sheath that allow the action potential to 'jump' from node to node, speeding up signal transmission.

What occurs during the refractory period of a neuron?

A brief period following an action potential when another cannot be initiated because $Na^+$ channels temporarily inactivate, $K^+$ exits, and ion pumps restore the resting potential.

What are terminal buttons?

Knoblike structures at the ends of axon branches that contain vesicles filled with neurotransmitters.

What are receptor sites on a receiving neuron?

Parts of the postsynaptic cell membrane with matching molecular structures that bind specific neurotransmitters to initiate or prevent an electrical signal.

What are the three processes that stop neurotransmitter action in the synapse?

Reuptake (absorption back into presynaptic neuron/glial cells), enzyme deactivation (breakdown by synaptic enzymes), and diffusion (drifting away).

What is the function of autoreceptors on the presynaptic neuron?

They detect the concentration of released neurotransmitters in the synapse and signal the presynaptic neuron to halt further release.

What is the primary function of acetylcholine (ACh)?

It participates in voluntary motor control and contributes to attention, learning, sleep, dreaming, and memory.

What functions are regulated by dopamine?

Motor behavior, motivation, pleasure, emotional arousal, reward processing, and addiction.

What are the roles of glutamate and GABA in the brain?

Glutamate is the major excitatory neurotransmitter that enhances transmission, while GABA is the primary inhibitory neurotransmitter that prevents firing.

What condition can result from excessive glutamate or deficient GABA?

Neurons can become overactive, which can trigger seizures.

What function is associated with norepinephrine?

Vigilance, or heightened awareness of potential environmental hazards.

What biological functions does serotonin regulate?

Sleep and wakefulness, eating, aggressive behavior, and mood.

What is the primary function of endorphins?

They act within pain pathways and emotion centers to reduce pain perception and elevate mood.

How do agonist and antagonist drugs differ?

Agonists increase or enhance the action of a neurotransmitter, whereas antagonists diminish or inhibit neurotransmitter function.

How does amphetamine affect neurotransmitter action?

It stimulates the release of norepinephrine and dopamine and blocks their reuptake.

What are the two primary divisions of the nervous system?

The central nervous system (CNS) and the peripheral nervous system (PNS).

What components make up the central nervous system (CNS)?

The brain and the spinal cord.

What are the two subdivisions of the peripheral nervous system (PNS)?

The somatic nervous system and the autonomic nervous system.

What is the functional difference between the somatic and autonomic nervous systems?

The somatic system carries signals between the CNS and skeletal muscles for voluntary control, while the autonomic system controls involuntary functions of internal organs, blood vessels, and glands.

What are the two divisions of the autonomic nervous system and their functions?

The sympathetic nervous system prepares the body for action in threatening situations, while the parasympathetic nervous system returns the body to a normal resting state.

What is a spinal reflex?

A simple nervous system pathway that rapidly triggers muscle contraction without requiring initial input from the brain.

How does the location of a spinal cord injury affect functional loss?

The higher the injury occurs along the spinal cord, the greater the potential loss of sensory input and motor control.

How many pairs of chromosomes do humans normally have?

Humans normally have $23$ pairs of chromosomes.

How do monozygotic and dizygotic twins differ genetically?

Monozygotic (identical) twins develop from one fertilized egg and share $100\%$ of their genes, whereas dizygotic (fraternal) twins develop from two separate eggs and share about $50\%$ of their genes.

What do schizophrenia twin concordance rates reveal about genetics and environment?

Dizygotic twins have a $27\%$ likelihood of developing schizophrenia if their twin has it, compared to $50\%$ for monozygotic twins, showing substantial genetic influence alongside environmental factors.

What is epigenetics?

The study of environmental influences that determine whether and how strongly genes are expressed without altering the underlying DNA sequence.

What are the major structures of the hindbrain and their functions?

The medulla (coordinates heart rate, circulation, respiration), reticular formation (regulates sleep, wakefulness, arousal), cerebellum (controls fine motor skills, sequence, balance), and pons (relays info to other brain parts).

What are the functions of the tectum and tegmentum in the midbrain?

The tectum helps orient an organism toward environmental stimuli, while the tegmentum aids in movement, arousal, and sensory orienting.

What is the function of the thalamus?

It relays and filters sensory information to the cerebral cortex for all primary senses except smell.

What body functions are regulated by the hypothalamus?

Body temperature, hunger, thirst, sexual behavior, blood sugar, and metabolism.

What is the critical role of the hippocampus?

Creating new long-term memories and integrating them into knowledge networks for storage.

What role does the amygdala play in cognitive processing?

It plays a key role in emotional processes, specifically emotional memory formation and attributing emotional significance to events involving fear, reward, or punishment.

What is the function of the pituitary gland?

Known as the master gland, it releases hormones that direct the functions of other endocrine glands throughout the body.

What are the four lobes of the cerebral cortex and their primary functions?

Occipital (processes visual info), Parietal (processes touch/contains somatosensory cortex), Temporal (hearing, language, object recognition), and Frontal (movement/motor cortex, abstract thinking, planning, judgment).

What is meant by contralateral representation in cerebral hemispheres?

Each cerebral hemisphere controls and receives sensory input from the opposite side of the body.

What is the corpus callosum?

A large bundle of axon fibers connecting the left and right cerebral hemispheres that enables communication between them.

What determines the size of a body part's representation in the somatosensory cortex?

The degree of sensitivity of the body part; more sensitive regions (e.g., lips and tongue) have larger cortical representations.

What are mirror neurons?

Neurons that become active both when an individual performs a behavior and when they observe another individual performing that same behavior.

What is brain plasticity?

The brain's ability to adapt to changes in sensory input and reorganize its neural functions.

What is phantom limb syndrome?

A condition in which an individual who has lost a limb continues to experience sensations, movement, or pain as if the missing limb were still present.

What did the case of Phineas Gage reveal about the frontal lobe?

Dramatic changes in his personality following frontal lobe damage demonstrated that the frontal lobe regulates emotion, planning, and decision making.

What key discovery was made through split-brain research?

It demonstrated that the two hemispheres specialize in distinct functions (e.g., language in the left hemisphere) and normally communicate via the corpus callosum.

How do CT scans, MRIs, and DTIs differ in structural brain imaging?

CT scans use multi-angle X-rays to assess tissue density; MRIs use magnetic fields and radio waves for high-resolution soft tissue images; DTIs visualize white matter pathways.

How do PET scans and fMRI differ in functional brain imaging?

PET tracks a radioactive substance in blood flow to identify active regions, whereas fMRI measures oxygenated vs. deoxygenated hemoglobin differences without radiation.

How does Transcranial Magnetic Stimulation (TMS) help establish causal brain relationships?

It uses magnetic pulses to temporarily deactivate specific cortical regions, allowing researchers to observe subsequent behavioral changes and test causal hypotheses.

Is the claim that humans only use $10\%$ of their brain scientifically accurate?

No, it is a myth; the entire brain is active and utilized, though activation levels across different regions vary over time.