Functions of the Nervous System

Study Notes

Functions of the Nervous System

Sensory input involves gathering information to monitor changes both inside and outside the body, known as stimuli.
Integration processes and interprets sensory input to decide if a response is necessary.
Motor output is the response to integrated stimuli, activating muscles or glands.

Structural Classification of the Nervous System

Central Nervous System (CNS) consists of the brain and spinal cord.
Peripheral Nervous System (PNS) includes nerves that extend outside of the brain and spinal cord.

Functional Classification of the Peripheral Nervous System

Sensory (afferent) division carries information to the CNS.
Motor (efferent) division carries impulses away from the CNS and is divided into:
- Somatic nervous system (voluntary control).
- Autonomic nervous system (involuntary control).

Nervous Tissue: Support Cells (Neuroglia)

Astrocytes are star-shaped cells that brace neurons, form barriers between capillaries and neurons, and manage the brain's chemical environment.
Microglia are phagocytic cells that dispose of debris within the nervous system.
Ependymal cells line the cavities of the brain and spinal cord, circulating cerebrospinal fluid.
Oligodendrocytes produce a myelin sheath around nerve fibers in the CNS.
Satellite cells protect neuron cell bodies in the PNS.
Schwann cells form the myelin sheath in the PNS.

Nervous Tissue: Neurons

Neurons, or nerve cells, transmit messages and consist of a cell body (nucleus, Nissl substance, neurofibrils) and processes (dendrites and axons).
Dendrites conduct impulses toward the cell body, while axons conduct impulses away from it.

Axons and Nerve Impulses

Axon terminals contain vesicles filled with neurotransmitters, separated from adjacent neurons by the synaptic cleft.
Schwann cells produce myelin sheaths, and Nodes of Ranvier are gaps in the myelin sheath along axons.

Functional Classification of Neurons

Sensory (afferent) neurons carry impulses from sensory receptors like cutaneous sense organs and proprioceptors.
Motor (efferent) neurons transmit impulses from the CNS.
Interneurons (association neurons) connect sensory and motor neurons in CNS pathways.

Structural Classification of Neurons

Multipolar neurons have multiple extensions from the cell body.
Bipolar neurons possess one axon and one dendrite.
Unipolar neurons have a single process stemming from the cell body.

Functional Properties of Neurons

Irritability is the ability to respond to stimuli, while conductivity refers to the transmission of impulses.
Neurons maintain a polarized plasma membrane at rest, with fewer positive ions inside than outside.

Starting a Nerve Impulse

Depolarization occurs when a stimulus causes the neuron’s membrane to change, allowing sodium ions (Na+) to enter, initiating an action potential.

The Action Potential

If an action potential starts, it propagates along the entire axon; potassium ions exit after sodium ions rush in, repolarizing the membrane.
The sodium-potassium pump restores the original ion configuration, requiring ATP.

Nerve Impulse Propagation

Impulses travel towards the cell body, with speed increased in myelinated fibers.

Continuation of the Nerve Impulse between Neurons

Impulses cross synapses to other neurons by the release of neurotransmitters from axon terminals.

The Reflex Arc

Reflexes are rapid, predictable, and involuntary responses to stimuli utilizing reflex arcs, which follow a direct route from a sensory neuron to an interneuron and then to an effector.

Description

This quiz covers the essential functions of the nervous system, including sensory input, integration, and motor output. Explore how the nervous system responds to stimuli and the structural classification into the central and peripheral nervous systems. Test your knowledge on these foundational concepts of neurobiology.