Human Nervous System – Lecture Review

30 Question-and-Answer flashcards covering key points of the Human Nervous System lecture—components, functions, neuron structure, classifications, and physiological concepts.

What are the two main parts of the nervous system?

The Central Nervous System (CNS)—brain and spinal cord—and the Peripheral Nervous System (PNS)—all nerves outside the CNS.

Which three basic functions are carried out by the nervous system?

Sensation (sensory input), Integration, and Motor output.

How does the nervous system differ from the endocrine system in signal type and speed?

The nervous system uses fast electrical impulses along nerves, whereas the endocrine system uses slower chemical signals (hormones) in the blood.

What is homeostasis and which two body systems are chiefly responsible for it?

Homeostasis is the maintenance of a constant internal environment; it is chiefly controlled by the nervous and endocrine systems.

Define a neuron.

A neuron is a structural and functional unit of nervous tissue that transmits electrical impulses.

Why can destroyed neurons usually not be replaced?

Neurons cannot undergo mitosis after maturity, so lost neurons are generally irreplaceable.

Why do neurons have a high metabolic rate?

They require a continuous supply of oxygen and glucose to maintain electrical activity.

What is a nerve?

A bundle of axons (neurons) surrounded by connective tissue and blood vessels.

Name the three basic structural parts of a neuron.

Dendrites, cell body (soma), and axon.

What is the function of dendrites?

They receive signals from other neurons or sensory receptors.

Where are Nissl granules found and what is their function?

In the neuron’s cell body; they contain rough ER and ribosomes that synthesize proteins.

What is the myelin sheath and what cell forms it in the PNS?

A fatty insulating layer that speeds impulse transmission; formed by Schwann cells.

What is the neurilemma?

The plasma membrane of a Schwann cell that encloses the myelin sheath.

Explain the importance of Nodes of Ranvier.

They are gaps in myelin that allow impulses to jump rapidly from node to node, speeding conduction (saltatory conduction).

What are terminal branches and synaptic knobs?

Terminal branches are fine axon endings that terminate in synaptic knobs, where neurotransmitters are released to signal the next cell.

Do neurons physically touch at synapses?

No; they are separated by a tiny gap called the synaptic cleft where chemical transmission occurs.

Classify neurons by structure.

Unipolar (one process), Bipolar (one axon, one dendrite), Multipolar (one axon, many dendrites).

Where are bipolar neurons most commonly found?

In sensory organs such as the eyes and ears (least common overall).

Classify neurons by function.

Sensory (afferent), Motor (efferent), and Interneurons (association/relay).

What is the pathway of a sensory neuron’s impulse direction?

From receptors in the periphery toward the CNS.

Describe a typical sensory neuron’s structure.

Usually unipolar, cell body off to the side, short axon, no dendrites on the soma.

Where are interneurons found and what is their role?

Entirely within the CNS; they connect sensory and motor neurons and perform integration.

Describe a motor neuron’s impulse direction.

Conducts impulses from the CNS to effectors (muscles or glands).

What structural type are most motor neurons?

Multipolar—one long axon and many dendrites.

What is an effector in nervous system terminology?

A muscle or gland that carries out the response signaled by a motor neuron.

Define sensory receptor.

A structure that detects specific stimuli (e.g., light, temperature, pressure) and initiates a nerve impulse.

Why does myelin make impulse transmission faster?

It insulates the axon and forces the impulse to leap between Nodes of Ranvier rather than travel continuously.

What part of the nervous system evaluates sensory information and decides responses?

The Central Nervous System (brain and spinal cord).

Give two examples of internal stimuli monitored by the nervous system.

Blood pressure and blood pH/glucose levels.

Which nervous-system function directly initiates muscle movement?

Motor output.