Neuroscience Basics Quiz

Nervous Tissue

• The nervous system is a complex network in the body responsible for maintaining homeostasis and health.
• It is composed of different branches, and various cell types.
• The nervous system's purpose is to understand how it maintains health and homeostasis, identify and describe different nervous system branches and the different cell types that make up nervous tissue.

Nervous System Overview

• Sensory neurons carry information to the central nervous system.
• Interneurons are found in the brain or spinal cord.
• Motor neurons carry information from the central nervous system.

Nervous System Organization

• The central nervous system (CNS) includes the brain and spinal cord.
• The peripheral nervous system (PNS) includes cranial nerves, spinal nerves, enteric plexuses, and sensory receptors in skin.
• The PNS is further subdivided into the sensory and motor divisions.
• The motor division is further divided into the somatic nervous system (voluntary control of skeletal muscle) and the autonomic nervous system (involuntary control of smooth and cardiac muscle, and glands).
• Within the autonomic nervous system, are further divisions: sympathetic and parasympathetic.

Functions of the Nervous System

• Sensory function: detects changes (stimuli) in or outside the body.
• Integrative function: analyzes sensory information, stores some aspects or aspects, and makes decisions related to appropriate behaviors.
• Motor function: responds to stimuli by activating effectors—muscles or glands.

Histology of Nervous Tissue

• Neurons are electrically excitable cells.
• Neurons are the cellular units found in nervous tissue.
• Neuroglia cells (Glia) are also found in nervous tissue.
• Neuroglia cells do not generate impulses, but support, insulate and protect neurons. Glial cells make up half the volume of nervous tissue.
• Other features of nervous tissue include, myelin sheath. myelinated axons and unmyelinated axons

Neurons

• Neurons are electrically excitable cells.
• A nerve impulse is an action potential.
• Neurons have different structures(parts) like dendrites, cell body, axon etc

Structural Classification of Neurons

• Multipolar neurons have many processes that extend from the cell body.
• Bipolar neurons have two processes that extend from the cell body.
• Pseudounipolar neurons have one process that extends from the cell body, but splits into two branches.

Functional Classification of Neurons

• Sensory neurons convey information to the central nervous system.
• Motor neurons convey information from the central nervous system.
• Interneurons process sensory information and elicit a motor response.

Neuroglia

• Neuroglia support neurons in many ways in the central and peripheral nervous system.
• Neuroglia are not excitable.
• In the central nervous system (CNS), there are four types of neuroglia: (1) Astrocytes; (2) Oligodendrocytes; (3) Microglia; (4) Ependymal cells.
• In the Peripheral Nervous System (PNS), there are two types of neuroglia: (1) Satellite cells; (2) Schwann cells

Myelination of Neurons

• The myelin sheath is produced by Schwann cells (PNS) and oligodendrocytes (CNS).
• Myelin sheath surrounds the axons of most neurons; it increases speed of AP propagation

Gray Matter vs. White Matter

• Gray matter contains neuron cell bodies and dendrites.
• White matter contains myelinated axons.

Electrical Signals in Neurons (Action Potential)

• Excitable cells communicate through action potentials
• Resting membrane potential
• Action potentials occur when a stimulus causes a membrane to reach threshold.

Graded Potentials

• Gradual potentials. These potentials determine the strength of the initial stimulus
• These are brief changes in membrane potential that can be depolarizing or hyperpolarizing.
• Graded potentials generally decreases in strength over time

Ion Channels

• Leak channels: Open/close randomly
• Ligand-gated: Open in response to ligand.
• Mechanically-gated: Open in response to physical changes.
• Voltage-gated: Open in response to voltage changes.

Resting Membrane Potential

• The inside of the neuron—specifically the axon—is negative compared to the outside.
• This difference results from different concentrations of ions (sodium, potassium, etc.) inside versus outside.
• This difference in charge is maintained, in part, by the sodium-potassium pump and other ion channels through the cell membrane.

Postsynaptic Potentials (PSP)

• Excitatory postsynaptic potentials (EPSPs) are depolarizing potentials.
• Inhibitory postsynaptic potentials (IPSPs) are hyperpolarizing potentials.

Neurotransmitters

• Chemical signals that transmit information between neurons or between a neuron and an effector.
• Neurotransmitters can be classified in to several categories based on size and chemical makeup

Summary of Neurotransmitter Removal

• Neurotransmitters can be removed through several mechanisms including diffusion, enzymatic degradation and uptake into cells.

Summation

• Summation of PSPs can result in the firing of an action potential.
• Spatial summation occurs when multiple presynaptic neurons release neurotransmitters at approximately the same time.
• Temporal summation occurs when a single presynaptic neuron releases neurotransmitters in rapid succession.

Neural Circuits

• Simple series: series of neurons
• Diverging: one impulse stimulates many neurons
• Converging: multiple neurons converge on a single neuron
• Reverberating: output neurons stimulate themselves
• Parallel after-discharge: multiple pathways, one final output

Regeneration and Repair of Nervous Tissue

• The nervous system is relatively high in plasticity. This means it can change based on experience and some neurons can regenerate or repair.
• Neurogenesis is little or no repair, especially in the CNS, due to inhibitory influences from neuroglia, growth-stimulating cues that were present during fetal development, and rapid formation of scar tissue
• Damage and repair are possible in the PNS, if cell body is intact, Schwann cells are functional, and scar tissue formation does not occur too rapidly.

Neural Disorders (Multiple Sclerosis & Depression)

• Multiple sclerosis is an autoimmune disease causing progressive destruction of myelin sheath.
• Depression is a neural disorder with various types (major, dysthymia, bipolar, & seasonal). Symptoms include lack of interest, sadness and possibly thoughts of suicide.

Additional Information

• The nervous system is responsible for many functions in the body. The detailed process can be further expanded with more detail.