the nervous system Flashcards
Neuron’s job
conduct electrochemiical impulses
Glial cells
support neurons, hold them together without touching
types of glial cells
astrocytes: clean up brain debris, transport nutrients
schwann cells
form myelin
Axon terminal
or synaptic terminals
have little bumps
contain synapric vesicles
have little sacs containing neurotransmitters
Node de Ranvier
where the axon is unprotected
axon
the long part of the neuron
can be covered in myelin sheath
myelin sheath
- Schwann cells
-increase speed of the neural impulse
-provides axon with nutrients and protexts it
-outer membrane is called neurilemma ; regenerate damaged neurons
cell body
aka soma, contains nucleus and neuroplasm
dendrites
extensions from soma
contain receptors
pick up electrical impulses
Saltatory conduction
impulses jump from one node to another
white matter
neurons contain myelin
grey matter
neurons that do not contain myelin
cannot be fixed once damaged (cognitive part of the brain)
types of neurons
- interneuron
- motor neuron
- sensory neuron
interneuron
carry impulses in the CNS
short axon without myelin
interprets sensory info and sends motor info
motor neuron
from CNS to the effectors
have long myelinated axons
sensory neurons
relay info from the environment to CNS
dendrites have sensory receptors disgned to receive external stimuli
long myelinated neurons
steps of neurotransmission
-resting neuron
-stimulated neuron
-depolarization
-repolarization
-refractry period
-the synapse
resting neuron
ICF is (-) with respect to ECF that is (+)
the membrrane is fairly impermeable to Na+ and mostly impermeable to K+
Na+ in ECF is 10x greater ICF
K+ in ICF is 30x greater than in ECF
Sodium-potassium pump
some ions leak through, the cell fix that with Sodium-Potassium pump (need ATP)
the way Sodium-potassium pump works
Na+ gets into the pump (with ATP) then it flips, Na+ gets out, K+ gets into the pump that flips again, releases K+ and ATP
what is a voltage?
the seperation in charge between ECF and ICF
the inside is negatively charged or POLARIZED
axon’s voltage equals to…
-70 mV
Stimulating a neuron
when neuron is stimulated, action potential begins (neurotransmission)
stimuli that can trigger a neuron to fire
chemicals, negatively charged electrodes, change in pH, mechanical deformation, heat/cold
treshhold level
around -55 mV
it is a minimum level of stimulus required
all or none response
either reaches the treshhold and fires or it doesn’t
Summation
two neurons can release neurotransmitters at the same time
Depolarization
(action potential 1)
Na+ channels opens
rush of Na+ into ECF due to diffusion
the inside becomes (+) (almost +40mV)
Na+ channels are found in the nodes of Ranvier
Repolarization
action potential 2
normal polarity must be restored
K+ channels open
K+ rushes out
action potential 2
normal polarity must be restored
K+ channels open
K+ rushes out
Na+/K+ pumps moves Na+ out and K+ in
refracotry period
time it takes to repolarize a membrane
if a second stimulus is applied, the neuron will not fire
the synapse
region between two nerve cells
neurotransmission passes through presynaptic neuron to postsynaptic neuron
cynaptic cleft
actual gap between presynaptic and postsynaptic neuron
what does the end of the axon contain?
synaptic vesicles that contain neurotransmitters
Acetylcholine (Ach)
is the neurotransmitter found most in the body
when the nerve impulse reaches the axon terminal…
a calcium channel opens up and Ca2+ rushes in
neurotransmitters get released into the synaptic cleft
neurotransmitters bind to the receptors in the postsynaptic membrane ina lock and key style
excitation- depolarization
positive ion channels (Na+ or Ca2+) opens up
positive ions rush in
reaches the treshhold
inhibition- hyperpolarization
K+ channels open up
K+ rushes out
Cl- channels open up
Cl- rushes in
neuron becomes more (-)
GABA
is the most common inhibitory neurotransmitter
why does the body need inhibitory neurotransmitters
-prioritize sensory info
-coordinate muscle mvt
-pain killers inhibit transmission
getting rid of neurotransmitters in the synapse
1.enzymes; break down transmitters
(cholinesterase; breaks down Ach)
2.re-uptake systems; allow neurotransmitters to be carried back inside the axon terminal.
organization of the nervous system
Nervous system: -central nervous system:-spinal cord + brain
-peripheral nervous system: *autonomic: involuntary: sympathetic and parasympathetic
*sensory-somatic nerves: voluntary: sensory neurons and motor neurons
spinal cord
runs from the sacrum into the brain through foramen magnum
large bundle of neurons
spinal cord is protected by…
vertebrae and 3 protected membranes called meninges
layers of spinal cord
outer layer is white matter
inner layer shaped H grey matter
the small hole running through the middle of the spinal cord is called
cerebrospinal canal contains cerebrospinal fluid that protects and carry nutrients and wastes to and from the spinal cord
how many roots each side has?
31 mixed spinal nerves
one half carries the sensory neurons, the other carries motor neurons
the 2 functions of the spinal cord?
- relaying info via interneurons from and to the brain
- the reflex arc
the reflex arc
automatic and involuntary response
1. sensory receptor
2.sensory neuron
3. interneuron
4.motor neuron
5.effector
protecting the brain
skull
3 membranes called meninges ( inflammation of these membranes is called meningitis)
and cerebrospinal fluid
hypothalamus
release hormone
control many autonomic fct
closely related to the pituitary gland
the pituitary gland
controls many hormones
is under the control of the hypothalamus
mostly made of gland tissue
cerebrum
largest part of the brain
consists of 2 hemospheres connected by corpus callosum
emotion, intellect, memory, reasoning
have an outer convulted layer, grey matter called cerebral cortex
each hemosphere of the brain is devided into 4 lobes
frontal lobe: intellect reasoning, planning, speech, mvt
contains motor cortex; controls voluntary mvt
parietal lobe
sensory areas, tpuch, temperature
has a sensory cortex; interpreting touch
occipital lobe
vision, has visual cortex
temporal lobe
hearing, has auditory cortex
left vs right hemospheres
left= math, logic and languages
right= spatial awareness, facial recognition, visual imagery
cerebellum
coordiantion of muscle activity
maintenance of balance
core white matter, convulted outer grey matter layer
pons
relay station for info
passes between cerebellum and medulla
medulla oblangata
swelling on top of the spinal cord
connect PNS and CNS controls autonomic fct
PNS
Peripheral nervous system
sensory somatic nervous system
carries sensory info to the CNS and motor messages to effectors
it has 2 nervess
cranial nerves and spinal nerves
cranial nerves
supply the sense organs and muscles of the head, neck and viscera
Vagus nerve
10th cranial nerve
supplies branches to many internal organs
carries motor nerve fibre to the heart and lungs
Autonomic nervous system
involuntary
part of the peripheral nervous system
autonomic motor nervous to the smooth and cardiac muscles and glabnds
sympathetic
fight or fly response
in stress
uses Ach and adrenaline as neurotransmitters
neurons arise from the middle of the spinal cord
parasympathetic
rest and digest
relaxed
uses only Ach as neurotransmitters
neurons arise from top and bottom of CNS vagus and palvic nerve
sensory receptors
convert various energy into electrochemical energy
baroreceptor ->
chemoreceptors ->
proprioreceptors ->
blood pressure
CO2, O2
mvt of limbs
taste
sweet, sour, bitter, salt and savoury(aka umami)
smell
stimulat eolfactory receptors
sensory adaptation
adjust to a change in the envrmnt
sensory receptors become less sensitive
the thalamus( above hypothalamus blocks those messages)
the eye has…. muscles
6 extrinsic muscles
the sclera
the flexible and thick outermost layer of the eye
at the front become CORNEA
nutrients are supplied by aqueous humor
the chroid layer
black/dark blue pigmented middle layer
prevents light reflexion
becomes iris at the front
iris
a band of thin circular muscles whch controls the amount of light that enters the pupil
the pupil
hole in which the light enters
retina
thin, brown layer
converts light into electrical impluses
contain rods and cons
fovea centralis
area at the back of the retina
it has the most cones for color reception
Fluids in the eye
aqueous humor
vitreous humor
aqueous humor
chamber of transparent fluid between cornea and the lens
vitreous humor
colorless jelly between the lens and retina
the lens
held in place by suspensory ligaments the surround the lens
suspensory ligaments
are held in place by ciliary muscles
they atter the shape of the lens
refraction
bent upside down onto the retina by the cornea, aqueous humor and the vitreous humor
accommodation
the bending of the lens to focus on objects
changes in the eye to see objects in the distance
lens become concave (flat)
ciliary muscles relax and the suspensory ligaments become taut
pupils dialate to capture as much light as possibel
changes to see object up close
lens become convex (rounded)
ciliary muscles contract
suspensory ligaments become slick
near point
the closest an object can get to the eye and remain focused
eye strain
close objects for long period of time
muscles become tired of contracting
interpreting the size of the image
the brain determines the siwze by the image projected on the retina
smaller image, means smaller imprint
eye problems
myopia
hyperopia
myopia
nearsightness
eyeball is too long
see near not far
hyperopia
farsightness
eyeball is too short
see far not near
other vision defects
astigmatism
a cataract
claucoma
astigmatism
abnormal curvature on the surface of the cornea
catarct
when the lens or the cornea becomes opaque
Rods
detect shades of white and grey
there’s no rods in the fovea
function when light levels are low
they are found in the periphery of the retina
cones
color vision
detect blue, red, green
most cones are located in the fovea centralis
colour blindness
one or more types of cones does not work properly
rhodospsin
light absorbing pigments found in rods
how do brain get messages?
impulses travel into the optic nerve, and then to the occipital nerve
blind spot
where the optic nerve connects to the retina
has no rods nor cons
the outer ear
aka pinna, visible part of the ear
auditory canal
carries waves to the eardrum
has sweat glans that produce ear wax
middle ear
tympanum & ossicles
tympanum
aka eardrum or tympanic membrane
flexible membrane that responds to compressions
vibrates at the same frequency and amplitude as the vibrations
ossicles
bones that carry the soumd waves to the inner ear
the first strikes 20x harder that it was struck by.
the eustachian tube
connects throat/nose and middle ear
equalizes pressure between the middle and outer ear
the inner ear
the cochlea (3 coiled chambers)
the cochlea
is snail-shaped structure converts mechanical vibrations into electrical messages
it contains 3 coiled chambers
organ of corti
located in the middle chamber
consists of layer of hair cells which have many cilia
cilia
hair cells standing in a layer of gelatinous fluid
how’s sound waves are transferred?
sound waves come down the cochlea and cause cilia to bend
the neurons connected to cilia fire, then those impulses go through the auditory nerve to the temporal lobe
how’s sound waves travel?
it compress and rarefy at different rates
what is high frequency wave?
the shorter the wavelength is, the higher pitch sound is
what is lower frequency wave?
the longer the wavelength is, the lower pitch the sound is
Amplitude
loudness of the sound is controlled by the amplitude
How does the organ of corti respond to the sound wave?
the first part responds to shorter wavelength
shorter wavelength touches sooner
lower frequency sound seem to travel further
the two types of deafness
- conduction deafness
2.nerve deafness
conduction deafness
the sound wave is not conducted to cochlear nerve
either is cognitial condition or scarring in the middle ear from an ear infection which causes the fossicles to fuse together.
nerve deafness
cochlea cannot transmit impulse to the brain
damaged cilia either by loud sounds or aging
treatment for deafness
hearing aids can be worn.
surgery to repair or replace damaged ossicles
cochear implants
how does the inner ear contributes to the balance?
there’s two parts of the inner ear that contribute to the balance; vestibule and semisercular canals
vestibule
gives info to the brain about the position of the head with respect to gravity
semisercular canals
three chambers that provide balance moving
these canals contain tiny ciliated hair cells attached to the neuron
when a person moves the fluid “sloshes” over hair cells
impulse is then transmitted to the auditory nerve to the brain
