PSB200 Neuroscience state mandated quiz Fall2025

What are the main parts of a neuron?

Dendrites, cell body (soma), axon hillock, axon, myelin sheath, nodes of Ranvier, axon terminals (terminal buttons).

Where does information typically come into a neuron?

Information usually comes into the neuron through the dendrites (and sometimes the soma), which receive synaptic input from other neurons.

What does the soma (cell body) do?

The soma integrates incoming signals, contains the nucleus and organelles, and supports the cell's metabolic functions (e.g., making proteins).

What is the axon hillock and what is its function?

The axon hillock is the region where the soma transitions into the axon; it is the main site of action potential initiation, where the neuron "decides" whether the summed inputs are enough to fire.

Which part of the neuron determines whether or not an action potential will occur?

The axon hillock (initial segment).

Which part of the neuron conducts the action potential over long distances?

The axon conducts the action potential from the cell body toward the terminals.

Where are the axon terminals located and what do they contain?

Axon terminals (terminal buttons) are found at the end branches of the axon and they contain synaptic vesicles filled with neurotransmitter.

What is myelin?

Myelin is a fatty, insulating sheath that wraps around segments of the axon, speeding up action potential conduction.

Which cells make myelin in the central and peripheral nervous systems?

In the CNS, myelin is made by oligodendrocytes. In the PNS, it is made by Schwann cells

What does myelin do for the neuron/action potential?

Myelin increases the speed and efficiency of action potential conduction by allowing saltatory conduction, where the action potential "jumps" from node to node.

What are nodes of Ranvier and why are they important?

Nodes of Ranvier are small gaps in the myelin along the axon where voltage-gated ion channels are concentrated; they are where the action potential is regenerated in a myelinated axon.

What is an action potential?

An action potential is a brief, all-or-none electrical signal that travels along the axon, caused by rapid changes in membrane potential due to ion movement.

Where does the action potential begin and where does it end?

It typically begins at the axon hillock/initial segment and travels down the axon to the axon terminals.

What is meant by depolarization?

Depolarization is a change in membrane potential that makes the inside of the cell less negative (more positive) compared to rest, moving toward the threshold for firing an action potential.

What is meant by hyperpolarization?

Hyperpolarization is a change that makes the inside of the cell more negative than the resting potential, making it less likely to fire an action potential.

During an action potential, which ions move into and out of the axon?

First, Na⁺ (sodium) ions flow into the axon during depolarization; later, K⁺ (potassium) ions flow out during repolarization/hyperpolarization.

In a myelinated axon, where is the action potential regenerated?

At the nodes of Ranvier.

What is the refractory period?

The refractory period is the time after an action potential when the neuron is less able or unable to fire another action potential. It includes:

What are the two types of refractory periods?

• Absolute refractory period: no new AP can be generated.

• Relative refractory period: a stronger-than-usual stimulus is required.

Why is the refractory period important?

It ensures one-way propagation of the action potential down the axon and sets an upper limit on how frequently a neuron can fire.

What determines the conduction velocity (speed) of an action potential?

Mainly:

• Axon diameter (larger = faster conduction),

• Myelination (myelinated = much faster),

• Distance between nodes of Ranvier.

What is a synapse?

A synapse is the junction between two neurons (or a neuron and another cell) where information is transmitted chemically or electrically.

What are the main structural parts of a chemical synapse?

• Presynaptic terminal (axon terminal with vesicles and transporters),

• Synaptic cleft (small gap),

• Postsynaptic membrane (often on a dendrite/spine with neurotransmitter receptors).

What are synaptic vesicles and what do they contain?

Synaptic vesicles are small membrane-bound sacs in the presynaptic terminal that contain neurotransmitter molecules.

What are transporters in the presynaptic terminal?

Transporters are proteins in the presynaptic membrane that reuptake neurotransmitter from the synaptic cleft back into the terminal, helping clear the synapse and recycle transmitter.

What are neurotransmitter receptors and where are they located?

Neurotransmitter receptors are proteins located on the postsynaptic membrane (usually dendrite or spine) that bind neurotransmitters and generate postsynaptic potentials.

What happens at a chemical synapse when an action potential arrives at the terminal?

1. Action potential reaches the presynaptic terminal.

2. Voltage-gated Ca²⁺ channels open, Ca²⁺ enters.

3. Ca²⁺ triggers vesicles to fuse with the membrane (exocytosis), releasing neurotransmitter.

4. Neurotransmitter diffuses across the cleft and binds to postsynaptic receptors.

5. This opens ion channels or triggers second messengers, creating EPSPs or IPSPs.

6. Neurotransmitter is cleared (reuptake, breakdown, or diffusion).

What is an EPSP (excitatory postsynaptic potential)?

An EPSP is a small, graded depolarization of the postsynaptic membrane that increases the probability of an action potential (e.g., Na⁺ influx).

What is an IPSP (inhibitory postsynaptic potential)?

An IPSP is a small, graded hyperpolarization of the postsynaptic membrane that decreases the probability of an action potential (e.g., Cl⁻ influx or K⁺ efflux).

How are EPSPs and IPSPs related to action potentials?

EPSPs and IPSPs summate (add up) at the axon hillock. If the combined depolarization reaches threshold, an action potential is generated. If inhibition dominates, the neuron will not fire.

What are the four main lobes of the cerebral cortex and where are they located relative to each other?

• Frontal lobe - front (anterior) part of brain.

• Parietal lobe - behind frontal lobe, top of brain.

• Temporal lobe - sides, below frontal and parietal.

• Occipital lobe - back (posterior) part of brain.

What are the 3 major fissures that divide lobes/hemispheres?

• Longitudinal fissure - separates left and right hemispheres.

• Central sulcus (fissure of Rolando) - separates frontal and parietal lobes.

• Lateral fissure (Sylvian fissure) - separates temporal lobe from frontal and parietal lobes.

In which lobe is the primary motor cortex located and what does it do?

Primary motor cortex is in the frontal lobe, on the precentral gyrus. It controls voluntary movements of skeletal muscles.

In which lobe is the primary somatosensory cortex located and what does it do?

Primary somatosensory cortex is in the parietal lobe, on the postcentral gyrus. It processes touch, pressure, pain, temperature, and body position.

In which lobe is the primary visual cortex located and what does it do?

Primary visual cortex is in the occipital lobe; it processes basic visual information (edges, orientation, etc.).

In which lobe is the primary auditory cortex located and what does it do?

Primary auditory cortex is in the temporal lobe; it processes sound information (pitch, volume, location).

Is primary motor and somatosensory processing ipsilateral or contralateral?

They are mostly contralateral: the left hemisphere controls/senses the right side of the body, and vice versa.

How is visual input organized between left and right hemispheres?

Visual processing is contralateral by visual field:

• The right visual field of both eyes is processed mainly in the left occipital cortex.

• The left visual field of both eyes is processed mainly in the right occipital cortex.

Where is the prefrontal cortex located and what are its main functions?

Prefrontal cortex is the most anterior part of the frontal lobes. It is involved in executive functions: planning, decision-making, working memory, impulse control, personality, and social behavior.

What/where is the "what" visual stream (ventral stream) and what does it do?

The ventral stream goes from occipital → temporal cortex and is involved in object recognition ("what" something is: shape, color, identity).

What/where is the "where" visual stream (dorsal stream) and what does it do?

The dorsal stream goes from occipital → parietal cortex and is involved in spatial processing and motion ("where" something is and how to interact with it).

Where is Broca's area (lobe and hemisphere) and what is its main function?

Broca's area is usually in the left frontal lobe, near motor areas controlling the mouth/face. It is critical for speech production and language expression.

Where is Wernicke's area (lobe and hemisphere) and what is its main function?

Wernicke's area is usually in the left temporal lobe (often at the junction of temporal and parietal lobes). It is crucial for language comprehension.

In most people, which hemisphere is dominant for language?

The left hemisphere is dominant for language in most right-handed and many left-handed people.

What is the general function of the brainstem as a whole?

The brainstem controls basic, life-sustaining functions (breathing, heart rate, arousal) and acts as a relay between spinal cord and higher brain areas.

What does the medulla do?

The medulla regulates vital autonomic functions such as heart rate, breathing, blood pressure, and reflexes like coughing and swallowing.

What does the pons do?

The pons helps regulate sleep and arousal, relays information between cortex and cerebellum, and plays a role in facial expressions and eye movements.

What does the midbrain do?

The midbrain is involved in orienting to visual and auditory stimuli, eye movements, and houses structures important for dopamine production and movement (e.g., substantia nigra).

What is the function of the cerebellum?

The cerebellum is critical for coordination, balance, posture, and fine-tuning motor movements; it also contributes to some learning and timing.

What is the function of the thalamus?

The thalamus is a major sensory relay station; it receives sensory information (except smell) and sends it to appropriate cortical areas.

What is the role of the hypothalamus?

The hypothalamus regulates homeostasis (body temperature, hunger, thirst), controls the endocrine system via the pituitary, and is involved in motivated behaviors and the stress response.

What is the function of the hippocampus?

The hippocampus is essential for forming new declarative memories (facts and events) and is involved in spatial navigation.

What is the function of the amygdala?

The amygdala is involved in emotion processing, especially fear, threat detection, and emotional learning.

What is the function of the corpus callosum?

The corpus callosum is a large bundle of axons that connects the left and right cerebral hemispheres, allowing communication between them.

What is the function of the pituitary gland?

The pituitary gland, controlled by the hypothalamus, releases tropic hormones that regulate other endocrine glands (e.g., adrenal, gonads, thyroid). It's often called the "master gland."

What is the function of the pineal gland?

The pineal gland secretes melatonin, which helps regulate sleep-wake cycles and circadian rhythms.

What is the general function of the limbic system?

The limbic system (including hippocampus, amygdala, parts of hypothalamus, etc.) is involved in emotion, motivation, memory, and drives.

What is the general function of the basal ganglia?

The basal ganglia are a group of subcortical nuclei involved in movement control, habit formation, procedural learning, and sometimes cognition and emotion.

What are the two major divisions of the nervous system?

• Central nervous system (CNS): brain and spinal cord.

• Peripheral nervous system (PNS): all nerves outside the CNS.

What are the two main subdivisions of the PNS?

• Somatic nervous system

• Autonomic nervous system

What does the somatic nervous system do?

The somatic nervous system controls voluntary movements and transmits sensory information (touch, pain, etc.) to the CNS.

What are the two main branches of the autonomic nervous system and their general functions?

• Sympathetic nervous system - "fight or flight": increases heart rate, dilates pupils, inhibits digestion, releases adrenaline.

• Parasympathetic nervous system - "rest and digest": slows heart rate, stimulates digestion, promotes energy storage.

In the hypothalamic-pituitary-adrenal (HPA) axis, what is the releasing hormone from the hypothalamus?

CRH (corticotropin-releasing hormone).

In the HPA axis, what is the tropic hormone released from the anterior pituitary?

ACTH (adrenocorticotropic hormone).

In the HPA axis, what hormone is secreted by the adrenal cortex?

Cortisol (a glucocorticoid stress hormone).

In the hypothalamic-pituitary-gonadal (HPG) axis, what is the releasing hormone from the hypothalamus?

GnRH (gonadotropin-releasing hormone).

In the HPG axis, what tropic hormones are released from the anterior pituitary?

LH (luteinizing hormone) and FSH (follicle-stimulating hormone).

In the HPG axis, what hormones are secreted by the gonads?

• Ovaries: estrogens and progesterone.

• Testes: testosterone (and other androgens).

In the hypothalamic-pituitary-thyroid (HPT) axis, what is the releasing hormone from the hypothalamus?

TRH (thyrotropin-releasing hormone).

In the HPT axis, what is the tropic hormone from the anterior pituitary?

TSH (thyroid-stimulating hormone).

In the HPT axis, what hormones are secreted by the thyroid gland?

Thyroid hormones: mainly T3 (triiodothyronine) and T4 (thyroxine), which regulate metabolism.

What is negative feedback in endocrine systems?

Negative feedback occurs when the final hormone (e.g., cortisol, thyroid hormone, sex hormones) feeds back to the hypothalamus and pituitary to reduce further release of releasing and tropic hormones, helping maintain homeostasis.

Which brain region is primarily affected in Alzheimer's disease (early on)?

The hippocampus and surrounding temporal lobe structures are heavily affected early, leading to memory loss; later, pathology spreads to widespread cortical areas.

Which brain region is primarily affected in Parkinson's disease?

The substantia nigra (a dopaminergic nucleus in the midbrain) degenerates, affecting basal ganglia circuits and causing motor symptoms (tremor, rigidity, slow movement).

Which brain region is primarily affected in Huntington's disease?

The striatum (especially the caudate nucleus) of the basal ganglia degenerates, leading to involuntary movements and cognitive/emotional changes.