Chapter 13: Peripheral Nervous System and Reflex Activity

Flashcards covering the key vocabulary terms in the provided lecture notes about the Peripheral Nervous System and Reflex Activity.

Peripheral Nervous System (PNS)

All neural structures outside the brain and spinal cord

Mechanoreceptors

Respond to touch, pressure, vibration, and stretch

Thermoreceptors

Sensitive to changes in temperature

Photoreceptors

Respond to light energy

Chemoreceptors

Respond to chemicals

Nociceptors

Sensitive to pain-causing stimuli

Exteroceptors

Respond to stimuli arising outside the body

Interoceptors (Visceroceptors)

Respond to stimuli arising in internal viscera and blood vessels

Proprioceptors

Respond to stretch in skeletal muscles, tendons, joints, ligaments, and connective tissue

Sensation

Awareness of changes in the internal and external environment

Perception

Conscious interpretation of stimuli

Transduction

Conversion of stimulus energy into nerve signals

Receptor potential

Small, local electrical change on a receptor cell brought about by an initial stimulus.

Receptive field

Area that detects stimuli for a sensory neuron

Phasic receptors

Signal the beginning or end of a stimulus (fast adapting)

Tonic receptors

Adapt slowly or not at all (slowly adapting)

First-order neurons

Conduct impulses from the receptor level to the second-order neurons in the CNS

Second-order neurons

Transmit impulses to the thalamus or cerebellum

Third-order neurons

Conduct impulses from the thalamus to the somatosensory cortex

Perceptual detection

Ability to detect a stimulus (requires summation of impulses)

Magnitude estimation

Intensity is coded in the frequency of impulses

Spatial discrimination

Identifying the site or pattern of the stimulus

Feature abstraction

Identification of more complex aspects and several stimulus properties

Quality discrimination

Ability to identify submodalities of a sensation

Pattern recognition

Recognition of familiar or significant patterns in stimuli

Conjunctiva

Transparent mucous membrane that lines eyelids

Accommodation

Changing the lens shape by ciliary muscles to increase refractory power

Presbyopia

Loss of accommodation over age 50

Myopia (nearsightedness)

Focal point for distant images is in front of the retina

Hyperopia (farsightedness)

Focal point for near objects is behind the retina

Astigmatism

Caused by unequal curvatures in different parts of the cornea or lens

Depth perception

Three-dimensional vision resulting from cortical fusion of slightly different images

Visual pigments (photopigments)

Molecules that change shape as they absorb light

Labeled line code

Pathway from sensory cells to the brain is labeled to identify its origin, and the brain uses these labels to interpret what modality the signal represents

olfactory fibers

A lesion of this area may result in partial or total loss of smell

Labeled line code

A code specifying how each fiber carries signals from sensory cells to the brain to allow the brain to interpret the modality.

Trigeminal neuralgia

Inflammation of this nerve may result in tic douloureux.

Nerve

A cordlike organ composed of numerous nerve fibers (axons) bound together by connective tissue

Perineurium

Connective tissue that wraps fascicles

Epineurium

Bundles numerous fascicles that constitutes whole nerve

Sensory (afferent) nerves

Carry signals from sensory receptors to the CNS

Motor (efferent) nerves

Carry signals from CNS to muscles and glands

Mixed nerves

Consists of both afferent and efferent fibers

Ganglion

Cluster of neurosomas outside the CNS

Reflexes

Quick, involuntary, stereotyped reactions of glands or muscle to stimulation

Inborn (intrinsic) reflex

A rapid, involuntary, predictable motor response to a stimulus

Learned (acquired) reflex

Results from practice or repetition

Muscle spindles

Inform the nervous system of the length of the muscle and the rate at which the muscle length changes

Golgi tendon organs (GTO)

Inform the nervous system as to the amount of tension in the muscle and tendons

Intrafusal fibers

Noncontractile in their central regions

Stretch reflex

Muscle contraction in response to increased muscle length (stretch)

Golgi Tendon Reflex

Polysynaptic reflexes that help to prevent damage due to excessive stretch and tension

Flexor (withdrawal) reflex

Causes automatic withdrawal of the threatened body part

Crossed extensor reflex

Occurs with flexor reflexes in weight-bearing limbs to maintain balance

Dermatome

A specific area of the skin that receives sensory input from a pair of spinal nerves