The Peripheral Nervous System: Afferent Division; Special Senses

Human Physiology - From Cells to Systems (Lauralee Sherwood) Chapter 6

CNS

Brain and spinal cord

ENS

controls the motility and secretion functions of the digestive system

• innervates the gastrointestinal tract

PNS

made up of nerves and ganglion

Parasympathetic Nervous System

Rest & digest

Sympathetic Nervous System

prepares body for stressful situations

“fight or flight”

stimulus

change detectable by the body

Sensory stimuli

carry conscious input

• five senses

  • sight, sound, smell, touch, taste

Visceral stimuli

carry subconscious input

• Complex stimulation

  • touch, pinch, heat, cutting, crush, and vibration

Photoreceptors

in the retina of the eye that function to detect light and convert it into electrical signals that the brain can interpret as vision

Mechanoreceptors

detect mechanical stimuli

• pressure, touch, and sound waves

Thermoreceptors

detect changes in temperature

Osmoreceptors

in the hypothalamus that detect changes in osmotic pressure

Chemoreceptors

detect chemical changes in the body’s fluids

• blood, cerebrospinal fluid, and saliva

Nociceptors

detect and transmit pain signals to the brain

Receptor potential

A receptor is going to detect a stimuli, determine if it’s important enough, then cause an action potential to occur to be able to send the signal down to the brain to integrate (determine what will happen)

Afferent & efferent neurons

Understand the image.

pain

Nociceptors are sensitive to ______.

a.) sound

b.) osmolarity

c.) pain

d.) light

Tactile

Mechanoreceptors are a type of ________ receptor.

Hair receptor

hair movement and very gentle touch

Merkel’s disc

light, sustained touch

Pacinian Corpuscle

vibrations and deep pressure

Ruffini endings

ONLY deep pressure

Meissner’s corpuscle

light, fluttering touch

Tonic receptor

a sensory receptor that slowly adapts to a stimulus and continues to produce action potentials as long as the stimulus is present

• e.g., thermoreceptors, pain receptors, joint capsule, muscle spindle, & Ruffini corpuscle

Phasic receptors

sensory receptors that respond quickly to stimuli but stop responding when the stimulus is constant

• e.g., Pacinian corpuscle, thermoreceptors, and touch receptors

Phantom pain

may arise from extensive remodeling of the brain region that originally handled sensation

• e.g., amputation of a limb

visceral afferent

What kind of nerves carry subconscious input information?

a.) sensory afferent

b.) sensory efferent

c.) visceral afferent

d.) visceral efferent

First order neuron

Which type of neuron? First, second, or third?

responsible for directly receiving sensory information from the periphery (like skin, muscle, or organs) and transmitting it to the central nervous system (CNS)

Second order neuron

Which type of neuron? First, second, or third?

receives signals from the first-order neuron (sensory receptor) and then transmits the information further up the neural pathway

• passes the spinal cord or brainstem

Third order neuron

Which type of neuron? First, second, or third?

Nerve cells that relay sensory information from the thalamus to the cerebral cortex

Acurity

how accurately a stimulus can be located

• influenced by receptive field or lateral inhibition

Receptive field

region of the skin surface surrounding the somesthetic sensory neuron

Lateral inhibition

each activated signal pathway inhibits the pathways next to it

Perception

conscious awareness of surroundings

Pain

a protective mechanism triggered on stimulation of danger-sensing nociceptors

• brings to conscious awareness the tissue damage that is occurring or about to occur

Pain receptors

Categories of what?

Mechanical (physical), thermal (temp), and polymodal (respond to multiple types of sensory stimulation, such as heat, touch, and chemicals)

Delta fibers and C fibers

types of nerve fibers that transmit pain and temperature sensations

A-delta fibers

nerve fibers that are:

• responsible for the initial perception of sharp pain

  • fast

C fibers

nerve fibers that:

• transmit duller burning pain

  • slow

A-delta fibers

What nerve fibers constitute the “fast pain” pathway?
a.) A-alpha fibers

b.) A-delta fibers

c.) A-beta fibers

d.) C fibers

Analgesic system

a pain control system in the brain and spinal cord that reduces pain perception

• endorphins released during exercise

• stress-induced

• acupuncture

eyelashes; lacrimal

Protective mechanisms that help prevent eye injuries:

• eyelids and ______

• tears and ________ gland

Accommodation

increases the strength of the lens for near vision

• strength depends on its shape

• regulated by the ciliary muscle

ciliary muscle

The strength of the lens depends on its shape, which in turn is regulated by what muscle?
a.) constrictor muscle

b.) radial muscle

c.) suspensory muscle

d.) ciliary muscle

Rods

provide indistinct gray vision at night

• high sensitivity

• low acuity

• vision in shades of gray

Cones

provide sharp color vision during the day

• low sensitivity

• high acuity

• color vision

Phototransduction

convert light stimuli into neural signals

• by retinal cells

• photoreceptors: rods and cones

Trichromatic theory

explains how humans perceive color by combining red, green, and blue light

Opponent processing theory

brain perceives color in terms of opposing pairs, such as red-green, blue-yellow, and black-white

Visual information Processing

modified and separated before reaching the visual cortex

• thalamus and visual cortex elaborate the visual message

  • depth perception

  • hierarchy of visual cortical processing

Visual field

field of view that can be seen without moving the head

external, middle, inner

What are the three parts of the ear?

Hearing

neural perception of sound energy

Sound waves

traveling vibrations of air

pitch, intensity, timbre

What are the three sound characteristics?

pitch

tone

intensity

loudness

timbre

quality

External ear

plays a role in sound localization

• pinna (ear, external auditory meatus (ear canal), & tympanic membrane (eardrum)

Tympanic membrane

vibrates in unison with sound waves in the external ear

• stretch across entrance to the middle

• vibrates when struck by sound wave (like drum)

Cochlea

pea-sized, snail-shaped, “hearing” portion of the inner ear

• contains the organ of Corti, the sense organ for hearing

  • hair cells in the organ of Corti transduce fluid movement into neural cells

Ossicles

Pitch discrimination

depends on the region of the basilar membrane that vibrates

• ability to distinguish among various frequencies of incoming sound waves

basilar membrane

Pitch discrimination depends on the shape and properties of the _______.

a.) basilar membrane

b.) ossicles

c.) stereocilia

d.) microvilli

Semicircular canals

sense head movement and maintain balance

Otolith organs

detect linear acceleration and gravity

Chemoreceptors

receptors for taste and smell

salty, sour, sweet, bitter, umami

Taste buds include what 5 taste bud receptors?

s_____, s______, s______, and u______

pheromones