Functions of Nervous System

Part 1

Sensory input

gathering information by which sensory receptors monitor changes called stimuli occurring inside and outside the body

Integration

nervous system processes and interprets sensory input and decides whether action is needed

Motor output

a response or effect activates muscles or glands

Homeostasis

the maintenance of a stable internal environment despite external changes

Mental activity

refers to processes such as thinking, learning, memory, and problem-solving that occur in the brain

Central nervous system

organs including the brain and spinal cord

Peripheral nervous system

nerves extending from the brain and spinal cord

Spinal nerves

carry impulses to and from the spinal cord

Cranial nerves

carry impulses to and from the brain

Sensory division

afferent; nerve fibers that carry info to the CNS

Motor division

efferent; nerve fibers that carry impulses away from the CNS organs to effector organs (ex. muscles and glands)

Somatic sensory

afferent; fibers carry info from the skin, skeletal muscles, and joints

Visceral sensory

afferent; fibers carry info from visceral organs

Somatic nervous system (efferent)

voluntary; consciously controls skeletal muscles

Autonomic nervous system (efferent)

involuntary; automatically controls smooth and cardiac muscles and glands and made of sympathetic and parasympathetic nervous systems

Supporting cells

makes up nervous tissue which resembles neurons, unable to conduct nerve impulses, and doesn’t lose the ability to divide (neuroglia, glial cells, glia)

Neuron

nerve cells which transmit messages and can not replicate

Cell body

soma which contains the nucleus and nucleolus

Dendrites

conduct impulses toward the cell body and receive signals from other neurons

Axons

conduct impulses away from the cell body

Synaptic cleft

gap between axon terminals and the next neuron

Myelin sheath

fatty husk surrounding nerve fibers

Schwann cells

produce myelin sheaths in jelly-roll like fashion

Nodes of Ranvier

gaps in myelin sheath along the axon which increase the speed of a nerve impulse

Nuclei

clusters of cell bodies in the CNS

Ganglia

collections of cell bodies outside the CNS in the PNS

Tracts

bundles of nerve fibers in the CNS

Nerves

nerves bundles of nerve fibers in the PNS

White matter

collections of myelinated fibers

Gray matter

mostly unmyelinated fibers and cell bodies

Sensory neurons

afferent; carry impulses from the sensory receptors to the CNS

Motor neurons

efferent; carry impulses from the CNS to viscera and/or muscles and glands

Interneurons

association neurons; cell bodies located in the CNS which collect sensory and motor neurons

Irratability

ability to respond to a stimulus and convert it to a nerve impulse

Conductivity

ability to transmit the impulse to other neurons, muscles, or glands

Reflexes

rapid, predictable, and involuntary responses to stimuli and occur over neutral pathways called reflex arcs

Somatic reflex

stimulate skeletal muscles, involuntary, ex. pulling hand away from hot object

Autonomic reflex

regulate the activity of smooth muscles, the heart, and glands, ex. regulation of smooth muscles, heart, and blood pressure, glands, digestive system

Five elements of reflex arc

1) Sensory receptor which reacts to stimulus

2) Sensory neuron carries message to integration center

3) Integration center (CNS) processes info and directs to motor output

4) Motor neuron carries message to an effector

5) Effector organ is the muscle or gland to be stimulated