Neurophysiology - PNS Afferent

CNS is and contains

Central Nervous System

Brain and Spinal Cord

PNS is and contains

Peripheral Nervous System

Cranial and Spinal Nerves and Sensory Organs

Schematic of the Nervous System

1. Sensory Information

2. Goes to receptors

3. Afferent division

4. Goes to CNS (brain and spinal cord)

5. Efferent Division

6. Somatic or Autonomic nervous system

3 classes of receptors in PNS

Exteroceptors

Proprioceptors

Interoceptors

Exteroceptors sense

Sense the external environment

somatic (general) and special senses

Special Senses

vision, hearing, taste, smell, equilibrium (walking)

Proprioceptors sense

Positional Senses

ex) sensing the position of muscle or organ in space

- position and state of the muscle (ex: if its tensed or not)

Interoceptors sense

visceral (deep) senses or internal senses

- blood ph, stomach pain, blood pressure

nothing of the nervous system schematic occurs without

sensory information

afferent division deals with

sensory information that comes in

efferent output is to control effectors of the body via

nerves

somatic nervous system

motor neurons

- skeletal muscles

(biceps, quads, etc).

autonomic nervous system divisions

sympathetic and parasympathetic

sympathetic and parasympathetic control which body parts?

everything other than skeletal

- smooth & cardiac muscle, exocrine and endocrine glands, fat

enteric nervous system is a

self contained system dealing with the digestive organs

how many cranial nerve pairs?

12

- most are just afferent/efferent, few are mixed

How many spinal nerve pairs?

31

- all are mixed, both afferent and efferent

3 types of cartilage

Highland, Fibril, Elastic

Highland cartilage

most abundant

fibril cartilage

least abundant but strongest

elastic cartilage

flimsy, present in ears and nose

intervertebral disks are made of

fibrocartilage/ fibril

hole between a vertebrae

veritable foramen

what is in the veritable foramen

where spinal nerves come/exit

sciatica

inflammation of the sciatic nerve, may be rubbing against the bone or pinched

ppl w/ spina bifida have...

their lamina (back) of vertebrae naturally exposed

herniated disk

cartilage breaks and rubs on the nerve in the veritable foramen

Thinning disk

fibroblast make less connective tissue as you age, thinning between vertebrae

Disk degeneration with osteophyte formation

bone forms which obliterates the cartilage and space lessens

What are in the intervertebral disks?

Glycoproteins/proteoglycans

what do Glycoproteins/proteoglycans do

they have negative charges and attract water inside the disk

- constant water drag inside keeps our disks hydrated and thick

spinal stenosis

narrowing of the spinal canal with compression of nerve roots

Dorsal root ganglion contains

cell bodies of sensory unipolar neurons

dorsal ramus and root contains

sensory neurons

ventral ramus and root

motor neurons

both ventral and dorsal ramus form

fuse together to form the spinal nerve

all of the sensory information goes to the back or front of spinal cord?

back of the spinal cord

explain how sensory info goes through the spinal cord

1. sensory info comes through the dorsal ramus

2. passes by the dorsal root ganglion containing the unipolar cell bodies

3. goes to the rootlet, spinal nerve, then spinal cord to CNS

4. neuron comes out of spinal cord through ventral rootlets (motor info)

5. then goes to spinal nerve, then ventral root to body

spinal reflex arc (finger on stove)

1. stimulus activates receptor (ex) finger on stove

2. sensory neuron sends action potentials

3. sensory info goes to the spinal cord via interneuron, cell bodies of neurons in the dorsal root ganglia

3.5. collateral neuron sends info to the brain

4. motor neuron is activated tells the body to do something (ex: contract biceps)

5. response occurs (ex: you take your hand off stove)

motor neuron cell bodies

located in ventral gray matter of brain stem unlike sensory neuron cell bodies

gray matter looks gray bc

of all the cell bodies it has

All sensory info is processed on the...of the brain

opposite side of the brain

ex) right hand pain processed in left cortex

therefore you remove your hand from pain before your brain knows, this is a protective mechanism

Ipsilateral

info travels on the same side of spinal cord but crosses to the other side in the brain stem

ex) touch

Contralateral

goes across the spinal cord and then up to brain stem

ex) pain and temperature

5 types of receptors

mechanoreceptors, chemoreceptors, thermoreceptors, osmoreceptors, photoreceptors

Mechanoreceptors

need a mechanical stimulus that opens a channel and causes depolarization - sends APs to brain

tactile receptors

for touch

nociceptors

pain receptors

Baroreceptors

pressure receptors

ex) changes in blood pressue, present in carotid artery in neck

Proprioceptors receptors

monitor the position and movement of skeletal muscles and joints

auditory receptors

hearing

equilibrioceptors

equilibrium and balance (walking)

Chemoreceptors include

olfactory receptors, gustatory, and nociceptors

olfactory receptors

smell

gustatory receptors

taste

Thermoreceptors

temperature cold and hot

nociceptor is a

multi-modality receptor

mechanoreceptor and chemoreceptor and thermoreceptor

Osmoreceptors

detect the osmolarity of body fluids (ISF)

photoreceptors

detect vision

tonic receptors

slowly adapting receptors that respond for the duration of a stimulus

- as long as stimulus is there, graded potential continues, action potential is still there but is less

ex) paper cut

phasic receptors

fast adapting

- stimulus is sustained, but graded potential and action potential disappear

- touch, smell, wearing a shirt

somatic (general) senses include

Touch, vibration, pressure, stretch, pain, and temperature

- all located in the skin

3 layers of skin

epidermis, dermis, hypodermis

hypodermis is

a layer of fat beneath the skin

free nerve endings are present in the...

epidermis, detect pain and temp, are dendrites

Merkel's disks

respond to light touch

- in epidermis

- single cell neurons

Meissner's corpuscles

light touch

- connected to hair follicles

- in dermis

Pacinian (lamellated) corpuscles

deep pressure and vibration

- in hypodermis

Ruffini corpuscles

detect stretch

- in dermis

Nocicieption means

pain

analgesia

reducing pain

Antihistamines, what they do

blocks histamine - vasoconsrict your blood vessels

- and histamines vasodilate blood vessels so your nose dries up and blood pressure goes down. Vasodilates so WBCs can go fight it

Antihistamines examples

Benadryl and Zyrtec

NSAIDS, what they do and examples

Blocks prostaglandin

- reduces inflammation which reduces pain because less fluid pressure on neuron

NSAIDs examples

- aspirin and ibuprofen

local anesthetics, what they do

Block voltage gated sodium channels

- no action potentials sent to brain, no pain

local anesthetics examples

articaine and lidocaine

Opiates, what they do

Reduce pain both the brain and spinal cord- endogenous (internal)

opiates examples

endorphines, morphine

Chilli peppers what do they do

Blocks substance P, reduces pain

What does substance P do?

enhances perception of pain, increases histamine

example of chilli peppers

capsaicin

referred pain

pain that is felt in a location other than where the pain originates

referred pain example

- cross talk between neurons in the heart and in the skin and they both travel up to the brain

Phantom pain

pain felt in a body part that is no longer there

why does phantom pain occur?

Stimulus can come from anywhere along the neuron not just the receptor

At the roof of your nasal cavity you have

Olfactory epithelium

supporting cells in nose

sustentacular cells, glial like cells

cribriform plate

A bony structure riddled with tiny holes, separates nose from brain

Holes in the cribiform plate are called

olfactory foreman

olfactory nerve fibers go through the...

holes in the nasal cavity

we have the ability to regenerate... in the nose due to

neurons in the nose due to stem cells

how the olfactory nerves sends info to the brain?

1. olfactory nerves go to your skull into the brain

2. nerve synapse in brian with secondary neurons

olfactory cilia

olfactory cilia or dendrites that contain receptor proteins

oderent molecules

dissolve in fluid and bind to receptors to activate them

sense of taste

gustation

5 tastes

sweet, sour, salty, bitter, umami

what is umami

glutamate

what is spicy? is it a taste?

not a taste, it is a thermal response so it uses unipolar neurons

bumps on the tongue are

papillae, not taste buds