Ch 13-1: Peripheral Nervous System

the peripheral nervous system divides into the ____ and ____ divisions

sensory and motor

the motor division of the PNS divides into the _____ and _____ nervous systems

somatic and autonomic

the autonomic nervous system divides into the ____ and ____ divisions

sympathetic and parasympathetic

awareness of the stimulus is called?

sensation

understanding the meaning of the stimulus is called?

perception

stimulus that responds to touch, pressure, vibration, and stretch?

mechanoreceptors

stimulus that is sensitive to changes in temperature?

thermoreceptors

stimulus that responds to light energy?

photoreceptors

stimulus that responds to chemicals?

(examples: smell, taste, changes in blood chemistry)

chemoreceptors

stimulus that is sensitive to pain-causing stimuli?

(examples: extreme heat or cold, excessive pressure, inflammatory chemicals)

nociceptors

Responds to stimuli arising outside body

exteroceptors

Responds to stimuli arising in internal viscera (organs) and blood vessels

Interoceptors (visceroceptors)

Responds to stretch in skeletal muscles, tendons, joints, ligaments, and connective tissue coverings of bones and muscles

Proprioceptors

simple receptors are used to detect ______ senses

general

where are simple receptors found?

throughout the body

receptors for special senses are found in?

complex sense organs

simple receptors do not have a “one receptor, one function” relationship which means they can?

respond to multiple stimuli

special sense receptors control…

vision, hearing, equilibrium, smell, and taste

the levels of the somatosensory system are called:

receptor, circuit, and perceptual

which level of the somatosensory system contains sensory receptors?

receptor level

which level of the somatosensory system processes information in ascending pathways?

circuit level

which level of the somatosensory system processes information in cortical sensory areas (the brain)?

perceptual level

what is the purpose of pain?

it acts as a warning signal for potential or actual tissue damage, prompting protective actions

what can trigger pain?

extreme pressure, temperature, and chemicals

what do pain signals travel through?

nerve fibers

the nerve fibers in which pain travel through release neurotransmitters such as?

glutamate and substance P

the body can reduce pain by using?

natural painkillers (endogenous opioids)

natural pain killers are also called

endogenous opioids

same pain detection, different _____

pain tolerance

everyone senses pain at the….

same intensity

____ can affect pain tolerance and response to pain medications

genes

pain that comes from internal organs and feels like a dull ache, burning, or cramping

visceral pain

tissue stretching, lack of blood flow (ischemia), chemicals, and muscle spasms all cause ________?

visceral pain

pain felt in a different area than its actual source is known as?

referred pain

why does referred pain happen?

because visceral and somatic nerves share pathways, so the brain misinterprets the pain's location

made up of bundled axons (both myelinated and nonmyelinated) surrounded by connective tissue

nerves

spinal nerves originate from the

spinal cord

cranial nerves originate from the

brain

3 connective tissue coverings:

epineurium, perineurium, and endoneurium

tough, fibrous nerve covering that surrounds the entire nerve, holding all fascicles together

epineurium

the outermost covering of the nerve is the

epineurium

the innermost covering of the nerve is the

endoneurium

a loose connective tissue that surrounds individual axons and their myelin sheaths (formed by Schwann cells)

endoneurium

a thicker connective tissue that groups axons into bundles called fascicles

perineurium

nerves are classified based on?

the direction they transmit impulses

mixed nerves

contain both sensory and motor fibers, transmitting impulses to and from the CNS

sensory (afferent) nerves

carry impulses toward the CNS

motor (efferent) nerves

carry impulses away from the CNS

most nerves are _____

mixed

sensory fibers that carry signals from muscles to the brain

somatic afferent

motor fibers that carry signals from the brain to the muscles

somatic efferent

sensory fibers that carry signals from organs to the brain

visceral afferent

motor fibers that carry signals from the brain to organs

visceral efferent

sensory nerves are?

afferent

motor nerves are?

efferent

somatic = _______

muscles

visceral = _______

organs

ganglia associated with afferent nerve fibers contain cell bodies of sensory neuron

dorsal root ganglia

ganglia associated with efferent nerve fibers contain autonomic motor neurons

autonomic ganglia

mature neurons are _____, which means they….

do not divide

if the cell body of a damaged nerve is intact, the peripheral axon may _____?

regenerate; only in PNS

where do axons do not regenerate?

in the CNS

______ in the CNS produce growth-inhibiting proteins that prevent regeneration

oligodendrocytes

_______ at the injury site form scar tissue, which also blocks healing

astrocytes

macrophages are used to remove dead axons debris and schwann cells begin to divide

step 2 of the regeneration process

the new axon filaments grow through the regeneration tube

step 3 of the regeneration process

the axon fully regenerates and a new myelin sheath forms around it

step 4 of the regeneration process

macrophages are used to ____ during the nerve regeneration process

remove/clean dead axon debris

how many pairs of cranial nerves are there?

12

most of the cranial nerves attach to the brain stem, except _____ and ______ which attach to the forebrain

olfactory and optic

the axon and myelin sheath beyond the injury break down

step 1 of the regeneration process