CNS vs. PNS Overview

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Questions and Answers

What primarily protects the Central Nervous System (CNS)?

Meninges and neurotransmitters

Skull, vertebrae, meninges, and cerebrospinal fluid (correct)

Synapses and the autonomic system

Cranial nerves and spinal nerves

Which statement accurately describes the role of sensory (afferent) components?

They carry signals from sensory receptors to the periphery

They conduct signals from muscles to the CNS

They function as input pathways carrying signals to the CNS (correct)

They transmit commands from the CNS to effectors

What type of motor control is associated with the autonomic motor division?

Involuntary regulation of smooth and cardiac muscle and glands (correct)

Conscious control of glandular secretion

Involuntary regulation of skeletal muscle

Voluntary activation of cardiac muscle

Which functional step involves sensory neurons sending signals to the CNS?

Afferent pathways Signup and view all the answers

What distinguishes the somatic motor division from the autonomic motor division?

Voluntary control in somatic motor division compared to involuntary in autonomic Signup and view all the answers

Which component of the nervous system is responsible for preparing the body for stress?

Sympathetic division Signup and view all the answers

In which division of the nervous system would you find cranial and spinal nerves?

Peripheral Nervous System (PNS) Signup and view all the answers

What type of receptors would detect light stimuli?

Photoreceptors Signup and view all the answers

What is the primary function of the dendrites in a neuron?

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

Which type of neuron is characterized as pseudounipolar?

Sensory Neurons Signup and view all the answers

What role do oligodendrocytes have in the central nervous system?

Myelinate CNS axons Signup and view all the answers

What process describes a localized change in membrane potential that varies in size?

Graded Potential Signup and view all the answers

How is the resting membrane potential primarily established?

Through sodium-potassium ATPase pump and potassium leak channels Signup and view all the answers

What occurs during the depolarization phase of an action potential?

Sodium ions influx into the neuron Signup and view all the answers

Which glial cells are responsible for supporting cell bodies in the peripheral nervous system?

Satellite Cells Signup and view all the answers

What is the function of the axon hillock in a neuron?

Initiate action potentials 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 and vertebrae, meninges, and cerebrospinal fluid.
PNS Structure: All neural tissue outside the CNS, including cranial nerves (12 pairs), spinal nerves (31 pairs), and sensory/motor fibers.
CNS Function: Integration and control center; interprets sensory input, coordinates motor output, and stores information.
PNS Function: Transmits sensory input to the CNS and motor commands from the CNS to effectors. Sensory division transmits sensory input, and the motor division transmits motor commands.

Sensory (Afferent) vs. Motor (Efferent) Components

Sensory (Afferent): Input pathways; carry signals from sensory receptors to the CNS. Divided into somatic sensory (external stimuli like pain, temperature, pressure) and visceral sensory (internal stimuli like organ stretch, chemical changes).
Motor (Efferent): Output pathways; carry commands from the CNS to muscles/glands. Divided into somatic motor (voluntary; skeletal muscle activation) and autonomic motor (involuntary; smooth muscle, cardiac muscle, gland regulation).

Nervous System as a Control System

Functional Steps: Sensory receptors detect stimuli, afferent pathways send signals to the CNS, control centers process input and formulate responses (reflex centers in spinal cord or higher brain processing).

Spinal Cord Anatomy and Reflexes

Gross Anatomy: Cervical and lumbar enlargements (contain motor neurons for limbs); conus medullaris (tapered end of spinal cord), and cauda equina (nerve roots extending below spinal cord).
Reflex Arc: Receptor → Sensory neuron → Integration center → Motor neuron → Effector.

Memory & Alzheimer's Disease

Memory: Short-term memory involves temporary increase in synaptic efficiency; long-term memory involves synaptic remodeling and new dendritic spines.
Alzheimer's Disease: Characterized by amyloid plaques, tau protein tangles, neuron death, and impaired memory and cognition.

Neuron Anatomy

Components: Cell body (soma) containing the nucleus and organelles, including chromatophilic substance (nissl bodies). Dendrites receive incoming signals. Axon transmits action potentials; the axon hillock initiates action potentials.

Types of Neurons

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

Neuroglial (Glial) Cells

CNS Glial Cells: Astrocytes (blood-brain barrier); Oligodendrocytes (myelinate CNS axons); Microglia (phagocytes); Ependymal cells (line ventricles, produce/circulate 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 with nodes of Ranvier enabling saltatory conduction.

Resting Membrane Potential (RMP)

Established by: Sodium-potassium ATPase pump (moves 3 Na+ out, 2 K+ in); K+ leak channels.
Key Concepts: Depolarization (membrane potential becomes more positive due to Na+ influx); repolarization (membrane returns to resting state due to K+ efflux); hyperpolarization (membrane potential becomes more negative).

Graded vs. Action Potentials

Graded Potentials: Localized changes in membrane potential; varying in size.
Action Potentials: Rapid, all-or-none depolarization; signals 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 postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) create depolarizing or hyperpolarizing signals.

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Description

Explore the structures and functions of both the Central Nervous System (CNS) and Peripheral Nervous System (PNS). Understand the differences between sensory and motor components, along with their roles in transmitting information within the body.