A&P: Chapter 11-Fundamentals of the Nervous System and Nervous Tissue

What are the 3 functions of the nervous system?

Sensory input, Integration, & Motor output.

What is sensory input?

Detection of internal & external stimuli and transmission of that information to the CNS.

What is integration in the nervous system?

Processing and interpretation of sensory input to decide on a response.

What is motor output?

Transmission of signals from the CNS to effectors (muscles and glands) to produce a response.

What is the difference between sensory input and motor output?

Sensory input carries information TO the CNS; Motor output carries commands FROM the CNS.

What structure makes up the CNS?

Brain & spinal cord.

What is the main function of the CNS?

Integration and control center that processes information and directs responses.

What structure makes up the PNS?

Cranial nerves, spinal nerves, and sensory receptors outside the CNS.

What is the main function of the PNS?

Communication lines that carry information to and from the CNS.

What does the sensory (afferent) division of the PNS do?

Carries sensory information FROM receptors TO the CNS.

What are somatic sensory fibers in the afferent division?

Carry sensory information from skin, skeletal muscles, & joints.

What are visceral sensory fibers in the afferent division?

Carry sensory information from internal organs.

What does afferent mean?

Carrying information towards the CNS (arrives).

What does the motor (efferent) division do?

Carries signals FROM the CNS TO effectors (muscles and glands).

What are effectors?

Structures that respond to motor signals (muscles and glands).

What does efferent mean?

Carrying information away from the CNS (exits).

What is the somatic nervous system of the efferent division?

Division of the motor system that controls skeletal muscle (voluntary movement).

What does the somatic nervous system control?

Skeletal muscles.

What is the autonomic nervous system of the efferent division?

Division of the motor system that controls smooth muscle, cardiac muscle, and glands (involuntary).

What does the autonomic nervous system control?

Organs, heart, & glands.

What is the sympathetic division?

Division of the autonomic nervous system that prepares the body for stress (fight or flight).

What does the sympathetic division do?

Increases heart rate, breathing, & energy use.

What is the parasympathetic division?

Division of the autonomic nervous system that conserves energy and promotes normal body functions (rest and digest).

What does the parasympathetic division do?

Decreases heart rate and promotes digestion and energy storage.

How are sensory input, integration, and motor output connected?

Sensory input (afferent) → CNS (integration) → motor output (efferent).

Trace the flow of information through the nervous system.

Receptor, sensory (afferent) → CNS → motor (efferent) → effector

What is the structural and functional relationship between CNS and PNS?

PNS carries information to and from the CNS, and the CNS processes that information and directs responses.

What is the relationship between somatic and autonomic systems?

Both are subdivisions of the motor division; Somatic is voluntary (skeletal muscle), autonomic is involuntary (organs and glands).

What are the two main cell types in nervous tissue?

Neurons (signal transmission) and neuroglia (support cells).

What is the main function of neurons?

Transmit electrical signals (action potentials).

What is the main function of neuroglia?

Support, protect, and maintain neurons.

Where are astrocytes found and what do they do?

Found in CNS; support neurons, regulate environment, & help with nutrient exchange.

Where are microglial cells found and what do they do?

Found in CNS; act as immune cells that remove debris and pathogens (phagocytosis).

Where are ependymal cells found and what do they do?

Found in CNS; line CNS cavities and circulate cerebrospinal fluid (CSF).

Where are oligodendrocytes found and what do they do?

Found in CNS; form myelin sheaths around axons in the CNS.

Where are Schwann cells found and what do they do?

Found in PNS; form myelin sheaths and help regenerate damaged axons

Where are Satellite cells found and what do they do?

Found in PNS; surround neuron cell bodies in PNS and regulate their environment.

Which glial cell forms myelin in the CNS?

Oligodendrocytes.

Which glial cell forms myelin in the PNS?

Schwann cells.

Which glial cell has an immune function?

Microglial cells.

Which glial cell circulates CSF?

Ependymal cells.

Which glial cell supports & regulates neurons in the CNS?

Astrocytes.

Why are neuroglia important if they do not transmit signals?

They maintain environment, protects neurons, provide nutrients, & support signal transmission.

How does myelin improve neuron function?

It insulates axons & increases the speed of signal conduction.

Why can peripheral nerves regenerate but CNS nerves cannot easily?

Schwann cells in the PNS support regeneration, but CNS glial cells do not.

What are the main parts of a neuron?

Dendrites, cell body (soma), axon hillock, axon, axon terminals.

What is the general function of a neuron?

To receive, process, and transmit electrical signals.

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

Processes incoming signals & contains organelles for cell maintenance.

What are Nissl bodies?

Rough ER in the neuron that synthesizes protein.

What is the function of dendrites?

Receive signals & carry them toward the cell body.

Where do graded potentials occur?

Dendrites & cell body.

Where are ligand-gated channels typically found?

Dendrites & cell body.

What is the function of the axon hillock?

Trigger zone where action potentials are generated if threshold is reached.

What happens if threshold is not reached at the axon hillock?

No action potential is generated.

What is the function of the axon?

Conducts action potentials away from the cell body.

Where do action potentials occur?

Along the axon.

Where are voltage-gated channels located?

Axon.

What is the function of axon terminals?

Release neurotransmitters to communicate with other cells.

What triggers neurotransmitter release at the axon terminal?

Influx of Ca²⁺.

What is the difference between dendrites & axons?

Dendrites receive signals; Axons transmit signals away from the cell body.

What is the difference between a nucleus & a ganglion?

Nucleus = cluster of neuron cell bodies in CNS; Ganglion = cluster in PNS.

What is the difference between tracts & nerves?

Tracts = bundles of axons in CNS; Nerves = bundles in PNS.

What is the function of the myelin sheath?

Insulates axon & increases speed of signal conduction.

What is the difference between myelinated & nonmyelinated fibers?

Myelinated fibers conduct signals faster; Nonmyelinated are slower.

What are nodes of Ranvier?

Gaps in myelin sheath where action potentials occur.

What is white matter?

Regions with mostly myelinated axons.

What is gray matter?

Regions with neuron cell bodies & nonmyelinated fibers.

What are the three structural types of neurons?

Multipolar, bipolar, & unipolar.

Which neuron type is most common?

Multipolar.

What are the three functional types of neurons?

Sensory, motor, & interneurons.

What does a sensory neuron do?

Carries signals to the CNS.

What does a motor neuron do?

Carries signals from the CNS.

What does an interneuron do?

Processes & relays signals within the CNS.

Trace the flow of information through a neuron:

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

Where are graded potentials vs action potentials loacted?

Graded potentials → dendrites/soma; Action potentials → axon.

Why is the axon hillock important?

It determines whether the neuron will fire based on threshold.

Why does myelin increase conduction speed?

It allows action potentials to jump between nodes, reducing signal loss.

What is the resting membrane potential (RMP)?

The electrical charge difference across the neuron membrane at rest (~ -70mV).

What does it mean that a neuron is “polarized”?

There is a difference in charge between the inside and outside of the cell (inside negative).

What is voltage?

Difference in electrical charge between two points.

What is current?

Flow of charged particles (ions).

What is resistance?

Opposition to the flow of current.

What ions are high inside the neuron at rest?

K⁺ & negative proteins.

What ions are high outside the neuron at rest?

Na⁺ & Ca²⁺.

Why does K⁺ movement contribute to a negative RMP?

K⁺ leaks out of the cell, taking positive charge with it.

Why do negative proteins contribute to RMP?

They are trapped inside the cell & add negative charge.

What does the Na⁺/K⁺ pump do?

Pumps 3 Na⁺ out & 2 K⁺ in, maintaining ion gradients.

How does the Na⁺/K⁺ pump contribute to RMP?

It causes a net loss of positive charge from the cell.

What is an electrochemical gradient?

Combined effect of chemical (concentration) & electrical forces on ion movement.

What is a chemical gradient?

Movement of ions from low to high concentration.

What is an electrical gradient?

Movement of ions toward opposite charge.

Why does Na⁺ tend to move into the cell at rest?

It is high outside (chemical gradient) & attracted to the negative interior (electrical gradient).

What are leakage channels?

Channels that are always open & allow passive ion movement.

What is the role of leakage channels in RMP?

Allow K⁺ to leak out, helping establish the negative interior.

What are ligand-gated channels?

Channels that open in response to neurotransmitters.

Where are ligand-gated channels typically found?

Dendrites & cell body.

What are voltage-gated channels?

Channels that open in response to changes in membrane potential.

Where are voltage-gated channels typically found?

Axon.

What are mechanically gated channels?

Channels that open in response to physical deformation (pressure/stretch).

Why is the resting membrane potential negative?

Because K⁺ leaves the cell, negative proteins remain inside, and the Na⁺/K⁺ pump removes more positive charge than it brings in.