NS part 2

Neuron

what is the structural unit of the nervous system

conduct messages in the form of nerve impulses

what do neurons do

cell body (soma), dendrite, axon, and myelin

what are the parts of a neuron

cell body (soma)

receives and integrates information

dendrites

processes that receive signals and carry them to cell body

nerve fiber

what is another word for axon

axon

generates impulses and transmits them

neurotransmitters at axon terminal which are released into extracellular space

what do axons have

myelin

a fatty sheath that insulated speeding up conducting

from schwann cells

yes

do Schwann cells regenerate

from oligodendrocytes

in the CNS, how is myelin formed

no

do oligodendrocytes regenerate

voltmeter

used to ensure the difference between two points

70mV more negative inside compared to outside, so it is said to be negative70mV

what does the neuron measure at rest

ion concentration

what accounts for much of the charge

Na+ is lower and K+ is higher

what is the concentration of NA+ and K+ inside the cell

Na+ is higher and K+ is lower

what is the concentration of NA+ and K+ outside the cell

depolarization (action potential)

a decrease in membrane potential, meaning less negative and eventually positive, to about +30mV. Basically less negative to more positive

due to Na+ (sodium) rushing in

how does depolarization occur

threshold

a depolarization to about

K+ flowing out, restoring the original negativity of the inside relative to the outside

what is repolarization due to

temporary hyperpolarization

an increase in negativity, meaning more negative temporarily than the original negative 70mV

an absolute refractory period

what occurs after an action potential

the neuron cannot fire no matter how strong the stimulus

what occurs in the absolute refractory period

an exceptionally strong stimulus can open the Na+ channels again

what occurs in a relative refractory period

axon diameter and degree of myelination

what are conduction velocities dependent upon

axon diameter

the larger the diameter, the faster the impulse

degree of myelination

the presence of myelin dramatically increases the speed of propagation

continuous conduction and saltatory conduction

what are the two types of propagation

continuous conduction

relatively slow, unmyelinated axons, no myelin

saltatory conduction

about 30x faster, due to jumping from unmyelinated areas to unmyelinated areas (myelin sheath gap)

synapse

a junction between two neurons or between a. neuron and a muscle cell of other effector organ

chemical synapse, they allow the release of neurotransmitters

what's the most common type of synapse and what does it do

acetylcholine

what is the primary neurotransmitter and the one that is released at the neuromuscular junction

axon terminal, synaptic vesicles with neurotransmitters synaptic cleft

what are the parts of a synapse

autonomic nervous system

the system that takes charge of thinks that you usually don't have "control over"

motor neurons that innervate smooth and cardiac muscle and glands

what is the ANS a system of

a 2

neuron chain

the stability of our internal environment

what depends upon the ANS

biofeedback

tells us that we can exert some control, so some people choose to call the ANS the "visceral" system

sympathetic and parasympathetic

what are the two branches of the ANS

sympathetic NS

mobilize the body in emergency or threatening situations

in a chain or sympathetic ganglia lateral to the spinal cord

how are cell bodies in the SNS

sweat glands, arrestor pili muscles, and smooth muscle in walls of arteries and veins

what does the SNS innervate

T and L levels, therefore it is called "thoracolumbar"

where does the SNS come from

parasympathetic NS

keeps body energy low and directs "housekeeping" such as digestion

because it includes some cranial nerves and some sacral spinal nerves, also it is located "around" the sympathetic

why is the PNS called "craniosacral"

for helping the body repair and relax

what are the effect of the PNS on target organs

3, 7, 9, 10

what cranial nerves are involved in the PNS

innervates smooth muscles in iris that cause pupillary constriction, also innervated ciliary muscle for accommodation for near vision

PNS function of CN III

innervates lacrimal gland to keep cornea moist, also innervates submandibular and sublingual salivary glands to begin the digestion of starch in the mouth

PNS function of CN VII

innervates parotid salivary gland for beginning of breakdown of starch in the mouth

PNS function of CN IX

innervates virtually every organ in thorax and abdomen- promoting digestion and/or relaxation

PNS function of CN X

CN X

what cranial nerve is the "queen" of the PNS

S2- S4 continues where vagus leaves off, innervates second half of large intestine, urinary bladder, uterus, and reproductive organs

what do the sacral spinal nerves S2 to S4 innervate

NO

are the organs that are targeted by PNS targeted 1:1 by SNS

preganglionic fibers

axon of neuron #1, from CNS to ganglion

postganglionic fibers

axon of neuron #2, from ganglion to target organ

ACH

what is the neurotransmitter in somatic NS

ACH

what is the neurotransmitter in parasympathetic NS

Norepinephrine

what is the neurotransmitter in sympathetic NS

adrenaline, like epinephrine

sympathetic NS is like a rush of what

adrenalin rush

what is mobilization

C3, C4, C5

what keeps the diaphragm alive

eyebrows, eyelids, eyelashes, conjunctiva, lacrimal apparatus, extrinsic ocular muscles, and intrinsic ocular muscles

what are the accessory structures of the eye

protection

eyebrow purpose

eyelid

what is the palpebrae

raises eyelid, passive opening and closed of the eye

what does the levator palpebrae do

ptosis

what occurs if the levator palpebrae is damaged

mucous membrane that lines eyelid and covered sclera

what is the conjunctiva

prevents eye from drying out

conjunctiva purpose

secretes tears

what does the lacrimal apparatus do

antibacterial

what are the enzymes in tears

nasal cavity

where do the lacrimal ducts empty into

superior rectus, inferior rectus, medial rectus, lateral rectus, inferior oblique, and superior oblique

what are the extrinsic ocular muscles

3, 4, 6

what cranial nerves innervate extrinsic ocular muscles

muscles of iris and ciliary body

what are intrinsic ocular muscles

fibrous layer, vascular layer, and inner layer

what are the 3 layers of the eyeball

sclera and cornea

what does the fibrous layer of the eye contain

dense avascular connective tissue

what type of tissue is the fibrous layer of the eye

white of the eye

what is the sclera

anterior continuation of sclera

what is the cornea

choroid, ciliary body, and iris

what does the vascular layer of the eye contain

dark brown membrane whose vessels nourish all eye layers

what is choroid

encircle lens, mostly made of muscles

what is ciliary body

attaches suspensory ligaments which hold onto lens

what does ciliary body attach

lens

what does the suspensory ligaments (ciliary zonule) hold

colored part of the eye, has central pupil

what is the iris

sphincter pupillae (circular muscles, for constriction), and dilator (radial muscles, for dilation)

what two smooth muscle layers does the iris contain

less sensitive

if you have more pigment to the iris, are you more or less sensitive to light

retina

what does the inner layer contain

pigmented layer and neural layer

what two layers does the inner layer (retina) contain

photoreceptors, rods and cones, and other cells such as bipolar cells, amacrine cells, and ganglion cells

what does the neural layer contain

dim light and black and white

what are rod receptors for

color vision and visual acuity

what are cones receptors for

optic disc, macula lutea, fovea centralis

what are other structures in the inner layer

fovea centralis

what area has the most cones, and is the area of the most acute vision

chambers

anterior segment with aqueous humor and posterior segment with vitreous humor

Aqueous humor

what does the ciliary body produce

Glaucoma

what can occur if drainage of aqueous humor is impaired