ch 13

PNS

Links between CNS to the outside world, consists of mostly nerves

Nerves

A bundle if axons and support tissues

Nerve

Mostly myelin and wrappings, endoneurorum, perineurium and epineurium

Endoneurium

Wraps an individual neuron

Perineurium

Wraps a bundle of neuron (each facicle)

Epineurium

Wraps the entire nerve

sensory

Afferent only

Motor

Efferent only

Both

Mixed, likely both somatic and autonomoc

Cranial nerve

Arises from the brain, 12 pairs

Spinal nerve

Arises from spinal cord, 31 pairs and all are mixed

Rami

Spinal nerve splits to form this

Doraal ramus

Short ramus, extends posteriorly to serve body behind spinal cord, mixed (sensory and motor)

Ventral ramus

Longer ramus, extends anteriorly to serve body infront of spinal cord, mixed, can exit in the thoracic region into rami communicantes

Rami communicantes

Carries autonomic axons to organs

Plexus

A region where multiple ventral rami meet and intersect

Cervical plexus

Located in the posterior portion of the neck, formed by the intermingling of the ventral rami of C1 to C5, produces superficial cutaneous nerves that serve the skin, produces deep motor nerves that serve muscles

Beachial plexus

Located near the meeting of the shoulder and nexk, formed by the intermingling of the ventral rami of C5 through C8 and parts of T1

Lumbar plexus

Lies anterior to pelvis, formed by the intermingling of the ventral rami of L1 through L4, produces nevres rhat serve the lower limbs

Sacral plexus

Lies posterior to the pelvis, formed by the intermingling of the ventral rami of L4 through S4, produces nerves that serve the lower limbs

Sensory receptors

Specialized neurons that collect information

Mechanoreceptors

Sensory cells that responsive to physical forces

Thermoreceptors

Sensory cells that are responsive to temperature, utilizes temperature-gated channels

Photoreceptors

Sensory cells that are responsive to light energy (only in the retina)

Chemoreceptors

Sensory cells that are responsive to the presence of chemicals of chemical changes

Nociceptors

Always responds to damaging stimuli (acid extreme temperatures)

Exteroceptors

Sensitive, usually near the surface of the body

Interoceptors

Sensitive to internal stimuli, subconscious sensory stimuli = visceral

Proprioceptors

A major group of interoceptors, in soft tissue associated with the skeleton, collects data on limb position, posture and muscle stretch, provides feedback to the cerebellum

Nonencapsulated nerve endings

Exposed dendrites, also called free nerve endings, sub type called the itch receptor

Itch receptor

Tiny and cannot be seen with a microscope, sensitive to inflammatory chemicals such as histamine

Exposed dendrites

knobby, group c, mostly epithelial and connective, reponsive to temperature, pain and touch

Encapsulated nerve endings

Dendrites are covered with a connective tissue capsule, almost all are mechanoreceptors

Messners corpsucles

Encapsulated nerve ending, detect and discriminates touch, light pressure, most abundant in hairless skin, also called tactile corpsucles

Pacinan corpsucles

Detects heavy pressure, can feel high frequency vibrations, also called lamellar corpsucles

Musvles spindles

Within skeletal muscles, detect stretch reflexes from lab