Nervous System Overview: CNS vs PNS

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Questions and Answers

What is the primary function of the Central Nervous System (CNS)?

Regulates involuntary functions of glands

Interprets sensory input and coordinates motor output (correct)

Controls voluntary movements of skeletal muscles

Transmits sensory input from receptors to the body

Which division of the Peripheral Nervous System primarily carries sensory information to the CNS?

Motor Division

Somatic Division

Autonomic Division

Sensory Division (correct)

What type of neuron pathway is used in the Somatic Motor Division?

Reflex arc

Single neuron pathway (correct)

Two-neuron chain

Mixed pathway

How do motor commands from the CNS reach effector organs?

Using efferent pathways Signup and view all the answers

Which neurotransmitter is primarily associated with the Somatic Motor Division?

Acetylcholine Signup and view all the answers

What is the role of the sympathetic division in the Autonomic Motor Division?

Prepares the body for stress Signup and view all the answers

Which component is NOT part of the Central Nervous System?

Cranial nerves Signup and view all the answers

What type of stimuli do visceral sensory pathways primarily transmit?

Internal stimuli from organs and systems Signup and view all the answers

What is the main function of dendrites in a neuron?

Receive incoming signals from multiple sources. Signup and view all the answers

Which type of neuron transmits sensory input to the central nervous system (CNS)?

Sensory neurons Signup and view all the answers

What is the primary role of oligodendrocytes in the CNS?

Myelinate multiple axons. Signup and view all the answers

What is established by the sodium-potassium ATPase pump in resting membrane potential?

Establishes a concentration gradient of sodium and potassium ions. Signup and view all the answers

Which of the following statements describes graded potentials?

They result from localized changes in membrane potential and vary in magnitude. Signup and view all the answers

What occurs when an action potential reaches the axon terminal?

Opening of voltage-gated Ca²⁺ channels. Signup and view all the answers

What is the role of satellite cells in the peripheral nervous system (PNS)?

Regulate the extracellular environment in ganglia. Signup and view all the answers

What occurs during hyperpolarization of the neuron membrane?

Membrane potential becomes more negative than the resting membrane potential. Signup and view all the answers

Study Notes

Central Nervous System (CNS) vs. Peripheral Nervous System (PNS)

CNS Structure: Brain (cerebrum, cerebellum, brainstem) and spinal cord, protected by skull, vertebrae, meninges, and cerebrospinal fluid (CSF)
PNS Structure: Neural tissue outside the CNS, including cranial nerves (12 pairs), spinal nerves (31 pairs), and sensory and motor fibers
CNS Function: Integrating and controlling center, interprets sensory input, plans and coordinates motor output, and stores information.
PNS Function: Sensory division transmits sensory input from receptors to CNS; motor division transmits motor commands from CNS to effectors.

Sensory (Afferent) vs. Motor (Efferent) Components

Sensory (Afferent) Input: Carries signals from sensory receptors to CNS.
- Subdivisions:
  - Somatic sensory (external stimuli e.g., pain, temp, pressure)
  - Visceral sensory (internal stimuli e.g., organ stretch, chemical changes)
Motor (Efferent) Output: Carries commands from CNS to muscles/glands.
- Subdivisions:
  - Somatic motor (voluntary; skeletal muscle activation)
  - Autonomic motor (involuntary; smooth muscle, cardiac muscle, and gland regulation)

Nervous System as a Control System: Functional Steps

Step 1: Sensory Receptors: Detect stimuli (e.g., photoreceptors in eyes, mechanoreceptors in skin)
Step 2: Afferent Pathways: Sensory neurons send signals to CNS
Step 3: Control Center (CNS): Processes input and formulates responses (e.g., reflexes in spinal cord or higher brain processing)

Somatic vs. Autonomic Motor Divisions

Somatic Motor Division:
- Single neuron pathway
- Voluntary control of skeletal muscles
- Neurotransmitter: Acetylcholine (ACh)
Autonomic Motor Division:
- Two-neuron chain (preganglionic and postganglionic neurons)
- Involuntary control of smooth/cardiac muscle and glands
- Divided into Sympathetic (prepares body for stress, "fight or flight") and Parasympathetic (promotes rest and recovery, "rest and digest")

Neuron Anatomy

Components: Cell body (soma), dendrites, axon
- Soma: Contains nucleus and organelles, chromatophilic substance (Nissl bodies) for protein synthesis
- Dendrites: Receive incoming signals, highly branched
- Axon: Transmits action potentials to other neurons or effectors; action potential initiates in axon hillock

Types of Neurons

Sensory (Afferent): Transmit sensory input to CNS; pseudounipolar structure.
Interneurons (Association Neurons): Connect sensory and motor neurons; entirely within CNS.

Neuroglial (Glial) Cells

CNS Glial Cells:
- Astrocytes (blood-brain barrier, regulate extracellular environment)
- Oligodendrocytes (myelinate CNS axons)
- Microglia (phagocytes, remove debris)
- Ependymal cells (line ventricles, produce and circulate cerebrospinal fluid (CSF))
PNS Glial Cells:
- Schwann cells (myelinate PNS axons, aid in repair)
- Satellite cells (support cell bodies in ganglia)

Myelination

CNS: Oligodendrocytes wrap multiple axons
PNS: Schwann cells wrap a single axon; nodes of Ranvier enable saltatory conduction

Resting Membrane Potential (RMP)

Established by sodium-potassium ATPase pump (3 Na⁺ out, 2 K⁺ in) and K⁺ leak channels
Key Concepts:
- Depolarization: Membrane potential becomes more positive (Na⁺ influx)
- Repolarization: Membrane potential returns to resting state (K⁺ efflux)
- Hyperpolarization: Membrane potential becomes more negative

Graded vs. Action Potentials

Graded Potentials: Localized changes in membrane potential, vary in size
Action Potentials: Rapid, all-or-none depolarization, propagate along axons

Synaptic Transmission: Steps

Action potential arrives at axon terminal
Voltage-gated Ca²⁺ channels open
Synaptic vesicles release neurotransmitter into cleft
Neurotransmitter binds to postsynaptic receptors
Excitatory/Inhibitory Postsynaptic Potentials (EPSPs/IPSPs): Depolarizing/Hyperpolarizing signals

Spinal Cord Anatomy and Reflexes

Gross Anatomy: Cervical/Lumbar enlargements (motor neurons for limbs), Conus Medullaris (tapered end of spinal cord), Cauda Equina (nerve roots extending below spinal cord)
Reflex Arc Components: Receptor → Sensory neuron → Integration center → Motor neuron → Effector

Memory and Alzheimer's Disease

Memory: Short-term (temporary synaptic increase), long-term (synaptic remodeling, new dendritic spines)
Alzheimer's Disease: Amyloid plaques, tau protein tangles, neuron death, impaired memory and cognition.

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Description

Explore the structures and functions of the Central Nervous System (CNS) and Peripheral Nervous System (PNS) in this comprehensive quiz. Test your knowledge on the sensory and motor components, including their subdivisions and roles within the nervous system.