Peripheral nervous system

ANS fiber types and neurotransmitters

-ALL ANS preganglionic axons release acetylcholine -ALL parasympathetic postganglionic axons release acetylcholine -Most sympathetic postganglionic neurons release norepinephrine ***exception: sympathetic postganglionic neurons innervating sweat gland release acetycholine

Sensory receptors

-Classification by stimulus: 1)mechanoreceptors 2) thermoreceptors 3) photoreceptors 4) chemoreceptors 5) nociceptors

Parasympathetic Nervous System

-Rest and Digest --responds to peace -Conserves energy by: --slowing HR --stimulating digestion --contracting bladder -Parasympathetic neurons release acetylcholine as a neurotransmitter -Opposes "flight or fight" activities of the sympathetic system

preganglionic vs postganglionic

-The axon of the preganglionic neuron synapses w/ the dendrite of the postganglionic neuron in a ganglion outside the CNS -Parasympathetic: preganglionic neurons are long and postganglionic neurons are short -Sympathetic: preganglionic neurons are short and postganglionic neurons are long

Motor (efferent) division

-Transmits impulses from the CNS to effector organs (muscles and glands) -There's 2 types of subdivisions: somatic (voluntary) nervous system and autonomic (involuntary) nervous system

Mechanoreceptors

-a sensory receptor that detect mechanical force, pressure (including BP), vibration

Photoreceptors

-a sensory receptor that detects light -only found in the retina in the eye

Nociceptors

-a sensory receptor that detects pain, damaged tissue as a result of extreme heat or cold, excessive pressure, inflammatory chemicals

Chemoreceptors

-a sensory receptor that detects smell, taste, changes in blood chemistry (O2, CO2, osmoality, etc)

Thermoreceptors

-a sensory receptor that detects temperature change

Sympathetic ganglion

-aka sympathetic chain or sympathetic trunk -preganglionic axons exit the lateral horn through the ventral nerve root to enter the sympathetic trunk ganglion

pupillary light reflex

-autonomic reflex -reflexes are diminished or absent with CN damage -it is normal for both pupils to constrict even though light is on one eye

ANS divisions

-causes opposite effects when serving the same organ (tissue) -two divisions: 1)sympathetic divison -fight or flight 2) parasympathetic division -rest and digest

somatic nervous system

-conscious control of skeletal muscles -you need to send a command

Sensory (afferent) division

-convey impulses from skin, skeletal muscles, joints and organs to the CNS

Nerves

-distribution of the major peripheral nerves of the upper and lower extremities

Sympathetic nervous system

-fight or flight --responds to stress -Uses energy to: --pupils dilate --increase HR --dilates bronchi --inhibits digestive tract -Stimulates the adrenal medulla to secrete epi (also called adrenaline) and norepi -Most sympathetic post ganglionic neurons also release norepi as a neurotransmitter -Opposes parasympathetic (peace) processes

peripheral nervous system

-lies outside the CNS -composed of cranial nerves, spinal nerves and ganglia --PNS nerves are associated w/ sensory receptors and efferent motor endings -nerves are bundles of axons -ganglion are swellings containing bodies

Free Nerve Ending Receptors

-located in the epidermis and dermis --4 types of receptor in one: a) mechanoreceptors-detect pressure b) chemoreceptors-detect itch and changes in pH c) thermoreceptors-detect warmth and cold d) nociceptors-detect extreme temperature, pinching, and chemical irritants; they contain proprioception fibers

Anatomy of parasympathetic division

-parasympathetic preganglionic neuron cell bodies are located: --in brain stem and sacral cord levels -parasympathetic postganglionic neuron cell bodies are located: --at a ganglion near the target organ -->where the preganglionin and postganglionin neurons synapse

Anatomy of sympathetic division

-preganglionin neuron cell bodies located: --lateral horns of spinal cord from T1 through~L2 -postganglionic neuron cell bodies located: --sympathetic trunk ganglion (alongside the vertebral column) --collateral ganglion (anterior to the aorta)

Reflexes

-rapid, predictable, and involuntary responses to stimuli -occur over neural pathways called reflex arcs involving both the CNS and PNS -all have five elements; receptor, sensory neuron, CNS integration (may or may not be interneuron), motor neuron, effector organ -there are 2 classifications: 1) somatic or spinal reflexes (only cord involved-doesn't go to the brain) a-deep tendon reflex arc b-withdraw reflex arc 2)autonomic reflexes (brain involvement) a-pupillary light reflex b-salivary reflex

autonomic nervous system (ANS)

-regulates smooth muscle, cardiac muscle and glands -you do NOT need to send a command -2 functional subdivisions are: 1)parasympathetic (rest, digest, peaceful system) 3)sympathetic (fight or flight; stress)

ANS (part II)

-sends impulses to smooth muscle in the walls of visceral organs, blood vessels and glands -controls heart rate, breathing rate, blood pressure and body temp (i.e. deals with homestasis) -functions involuntarily-w/o conscious control

Deep tendon reflex

-simple deep tendon reflexes consists of only two-neurons (sensory->sensory neuron->motor neuron->effector organ) -ex. taping the patellar tendon

Ventral and dorsal rami

-spinal nerves divide into a ventral and dorsal rami -each rami contain both sensory and motor fibers -small dorsal rami innervate the skin and muscles of the back (posterior trunk)

Spinal nerves

-the human body has 31 pairs of spinal nerves -named for the region of the cord from which they arise -formed by combination of ventral and dorsal roots

Autonomic Nervous System (ANS)

-the involuntary motor division of the peripheral nervous system -regulated by the hypothalamus

Cranial nerves

-they are part of the PNS b/c they bring info from outside to the brain -there are 12 pairs and they all come out on both sides of the inferior aspect of the brain -glossopharyngeal nerve is the affected in someone who has had a stroke -the vagus nerve is the only nerve to leave the head and then go to the viscera

Ventral rami

-ventral rami of T1-T12 supply intercostal muscles and skin of lateral and anterior trunk -all other ventral rami form nerve plexuses that supply motor and sensory fibers to the limbs

Spinal nerve formation

-ventral/anterior nerve roots contain motor fibers -dorsal/posterior spinal nerve roots contain sensory fibers -join inside the IVF to form a spinal nerve -therefore, ALL spine nerves are mixed

Withdraw reflex

-withdraw reflexes consists of 3-neurons (sensory receptor->sensory (afferent) neuron->interneuron->motor (efferent) neuron->effector organ) - ex. touching something hot or painful and then immediately move your hand

Mechanoreceptors (part II)

1) Merkel disc (cells) -located in the epidermis -detect light touch 2) hair follicle receptors -located in the dermis around hair follicles -detect hair deflection 3) Meissner's corpuscles -located in the papillary dermis of hairless skin -detect lights pressure -contain proprioception fibers

2 functional divisions of the PNS

1) Sensory (afferent) division 2) Motor (efferent) division

Motor pathway of ANS

ANS consists of a chain of 2 neurons 1) Preganglion neuron originates in the CNS 2) Postganglionic neuron originates in the PNS

Mechanoreceptors (part III)

all have proprioception fibers (which helps your muscles figure out where you are in space) 4) Pacinian corpuscles -located in the reticular dermis -detect deep pressure -ex. deep tissue massage 5) Ruffini corpuscles -located in the reticular dermis -detect deep pressure -ex. deep tissue massage 6) Muscle spindles -located in skeletal muscle -detect muscle stretch -ex. when you stretch 7) Golgi tendon organs -located in tendons -detect tendon stretch -ex. when you stretch outside the normal area 8) Joint kinesthetic receptors -located in synovial joint capsules -detect joint proprioception -ex. when you go from straight elbow to bent elbow

Three pathways

once preganglionic axon enters the sympathetic chain one of three things can happen 1) It can synapse at same level with a postganglionic neuron 2) it can travel up or down the sympathetic chain to synapse at a different level 3) it can travel through a splanchnic nerve to a distant collateral ganglion to synapse