Neural Systems, Cell Types, and Synaptic Function in Neuroscience

What are the 3 general functions of neural systems?

Sensory systems, motor systems, and associational systems.

What is the main function of sensory systems?

They provide information about the state of the organism and its environment.

What is the main function of motor systems?

They organize and generate actions or movements.

What is the main function of associational systems?

They link sensory and motor components and support higher-order brain functions.

Which higher-order functions are supported by associational systems?

Perception, attention, cognition, emotions, language, and rational thinking.

What did Reticular Theory propose about nerve cells?

Nerve cells are directly connected by protoplasmic links, forming one continuous nerve network.

What does the Neuron Doctrine state?

Neurons are discrete cells that communicate with one another through specialized contacts rather than forming one continuous network.

What is the key difference between Reticular Theory and the Neuron Doctrine?

Reticular Theory says the nervous system is a continuous network; the Neuron Doctrine says neurons are separate cells that communicate at specialized contacts.

Who is associated with Reticular Theory?

Camillo Golgi.

Who is associated with the Neuron Doctrine?

Santiago Ramón y Cajal and Charles Sherrington.

What evidence helped confirm neurons are individual cells?

High-resolution electron microscopy in the 1950s showed neurons as distinct cells and revealed synapses between them.

What is gene expression?

The production of proteins from genetic information.

What is the central dogma described in the course?

DNA → RNA → protein.

What happens during transcription?

DNA is used to produce RNA.

What happens during translation?

RNA is used to produce protein.

How can transcription factors regulate gene expression?

They become activated, enter the nucleus, bind DNA, and can enhance or turn off transcription.

Why does regulation of transcription matter for gene expression?

It determines whether particular genes are expressed or suppressed.

About how many genes are in the human genome?

About 20,000 genes total; about 14,000 are expressed in the developing or mature nervous system.

What is the function of ribosomes?

Protein synthesis.

What is the function of mitochondria?

They produce ATP through cellular respiration.

What is the main role of the nucleus?

It contains DNA and is where transcription occurs.

What is the function of the Golgi apparatus?

It modifies, sorts, and packages proteins.

What is the function of lysosomes?

They act as the digestive system of the cell.

What is the function of vesicles?

They transport proteins and other materials; in neurons, they package and help secrete neurotransmitters.

What is the function of the cytoskeleton?

It provides structural support and helps determine cell shape.

What are the 2 broad categories of cells in the nervous system?

Neurons and glial cells (neuroglia or glia).

What are neurons specialized to do?

Carry out electrical signaling over long distances and moment-to-moment communication.

What is the general role of glial cells?

They are supportive cells that help maintain conditions needed for nervous system function.

What is the main function of dendrites?

They are receptive regions that receive incoming signals.

What is the main function of the cell body (soma)?

It is a biosynthetic and receptive region that contains the nucleus.

What is the function of the axon hillock?

It is the region where the axon begins and where action potentials are initiated.

What is the main function of the axon?

It relays electrical signals over long distances.

What is the main function of axon terminals?

They are the secretory region where signals leave the neuron.

What are nodes of Ranvier important for?

They are gaps in myelin where voltage-gated channels are concentrated.

What is the usual direction of information flow through a neuron?

Dendrites → cell body → axon hillock/axon → axon terminals.

What is convergence?

The number of inputs received by a single neuron.

What is divergence?

The number of targets innervated by a single neuron.

How do short and long axons differ?

Short axons are typical of interneurons; long axons are projection neurons that extend to distant targets.

What are 3 major properties of an action potential?

It carries signals over long distances, is all-or-none, and propagates from the axon hillock toward the axon terminal.

What is a presynaptic neuron?

The neuron sending information toward a synapse.

What is a postsynaptic neuron?

The neuron or target cell receiving the signal from the synapse.

What is synaptic transmission?

The processes by which information encoded by action potentials is passed at synaptic contacts to a target cell.

Which type of synapse is most abundant?

Chemical synapses are most abundant.

What do synaptic vesicles contain?

Neurotransmitters.

What basic sequence occurs at a chemical synapse after an action potential reaches the axon terminal?

Voltage-gated Ca2+ channels open → Ca2+ enters → vesicles release neurotransmitter by exocytosis → neurotransmitter crosses the cleft → binds postsynaptic receptors.

How can neurotransmitter effects be terminated?

Reuptake through transport proteins, enzymatic degradation, or diffusion away from the synapse.

What is an axosomatic synapse?

An axon of one neuron synapses on the cell body of another neuron.

What is an axodendritic synapse?

An axon of one neuron synapses on a dendrite of another neuron.

What is an axoaxonal synapse?

An axon of one neuron synapses on the axon of another neuron.

What do astrocytes do?

They support and maintain the environment for neurons.

What do oligodendrocytes do?

They produce myelin in the CNS and can wrap multiple axons.

What do Schwann cells do?

They produce myelin in the PNS; one Schwann cell myelinates one axon segment.

What is the key difference between oligodendrocytes and Schwann cells?

Oligodendrocytes myelinate in the CNS and can wrap multiple axons; Schwann cells myelinate in the PNS and one cell wraps one axon segment.

What do microglia do?

They act like macrophage/scavenger cells, remove cellular debris after injury or normal turnover, and secrete cytokines.

How do glial stem cells differ from differentiated glial cells?

Glial stem cells retain the ability to proliferate and produce new cells; differentiated cells are mature cells with specific functions.

What is an afferent neuron?

A neuron that carries information from the periphery toward the brain or spinal cord.

What is an efferent neuron?

A neuron that carries information away from the brain or spinal cord toward effectors.

What is an interneuron?

A local circuit neuron that lies between sensory and motor neurons and usually has a short axon within the CNS.

How are neurons structurally classified?

By the number of processes extending from the cell body: multipolar, bipolar, or unipolar.

What defines a multipolar neuron?

It has 3 or more processes: 1 axon and multiple dendrites. It is the most common type and a major neuron type in the CNS.

What defines a bipolar neuron?

It has 2 processes: 1 axon and 1 dendrite. It is rare; examples include the retina and olfactory mucosa.

What defines a unipolar neuron?

It has 1 short process that divides in a T-shape; both branches are considered axons.

How do multipolar and unipolar neurons differ?

Multipolar neurons have 1 axon plus multiple dendrites; unipolar neurons have one short process that splits into peripheral and central axonal branches.

What structural class are sensory neurons typically?

Almost all sensory neurons are unipolar.

What structural class are motor neurons typically?

Motor neurons are multipolar.

Which structural neuron type is most common in the CNS?

Multipolar neurons.

What happens in the basic knee-jerk reflex sequence?

A tendon tap stretches the muscle; sensory receptors activate and generate an action potential; the sensory input excites a spinal motor neuron; the muscle contracts.

What is the role of the sensory neuron in the knee-jerk reflex?

It detects the muscle stretch and carries afferent information toward the spinal cord.

What is the role of the motor neuron in the knee-jerk reflex?

It carries an efferent signal from the spinal cord to the muscle and causes contraction.

What is the role of the interneuron in the knee-jerk reflex?

It inhibits the motor neuron associated with the opposing response, preventing that motor neuron from producing an action potential.

What type of neuron is labeled C in the Exam 1 practice reflex diagram?

The sensory (afferent) neuron.

What type of neuron is labeled D in the Exam 1 practice reflex diagram and what does it do?

D is an interneuron; it participates in the spinal circuit and inhibits the appropriate motor neuron.

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

The brain and spinal cord.

What is the peripheral nervous system (PNS)?

Nervous tissue outside the brain and spinal cord, including sensory and motor neurons.

What does the somatic motor division innervate?

Skeletal muscles.

What does the autonomic motor division innervate?

Smooth muscle, cardiac muscle, and glands.

What is the sympathetic division associated with?

Fight or flight.

What is the parasympathetic division associated with?

Rest and digest.

What is the enteric division?

Neurons located in the walls of the gut.

What are ganglia?

Collections of neuron cell bodies in the PNS.

What are nerves?

Bundles of peripheral axons in the PNS.

What are nuclei in nervous system anatomy?

Local collections of neuron cell bodies within the CNS.

What are tracts?

Groups of axons in the CNS; they are analogous to nerves in the PNS.

What are commissures?

Tracts that cross the midline of the brain.

What is gray matter?

Any accumulation of neuron cell bodies in the CNS.

What is white matter?

Myelinated axon tracts.

What is a cortex according to the Chapter 1 lecture?

A sheet-like array of nerve cell bodies.

What does electrophysiological recording measure?

The electrical activity of a nerve cell.

What is the difference between extracellular and intracellular recording?

Extracellular recording places an electrode near the cell; intracellular recording places the electrode inside the cell.

What does the Exam 1 review describe for Fig. 1.13 electrophysiological recording?

Stimulate one area and record the result from another; the example touches different parts of a receptive field and records cortical neuron activity.

What is the basic difference between structural and functional brain-imaging techniques?

Structural techniques show brain anatomy/layout; functional techniques show how the brain is working or which regions are active.

What is a CT/CAT scan?

An advanced X-ray technique that provides structural brain images and involves radiation exposure.

What is an MRI?

A structural imaging technique that uses strong magnetic fields and has much higher resolution than CT.

What is DTI used for?

Diffusion tensor imaging tracks white matter tracts.

What does fMRI measure?

It detects blood-related changes/concentrations to identify which brain regions are active at a given time.

What is PET imaging?

A functional technique that injects radioactive material to provide information about brain biology; it is more invasive and expensive than fMRI.

What does EEG measure?

Electrical signals from the brain using sensors placed on the scalp.

What does MEG measure?

Magnetic fields produced by brain activity rather than electrical fields.

What do TES and TMS do?

They are brain-stimulation techniques that use stimulation to activate or inhibit brain regions and help determine function.

What are the 3 major functions of the plasma membrane?

It defines the cell boundary, acts as a selective barrier, and mediates interactions between the cell and its environment.