nervous systems Flashcards
nervous system
made up of the central and peripheral system
peripheral nervous system
sensory pathways, motor pathways
- includes the automatic and somatic nervous system
central nervous system
brain, spinal cord
- has grey and white matter
autonomic nervous system
(involuntary)
sympathetic and parasympathetic nervous systems
- internal environment
- controlled by the hypothalamus and medulla oblongata
sympathetic nervous system
fight or flight
- neurons release neurotransmitters norepinephrine
- this converts glycogen to glucose (for energy)
parasympathetic nervous system
rest and digest
- neurons release neurotransmitter acetylcholine
neurons
- respond to physical and chemical stimuli
- conduct electrochemical signals
- release chemicals that regulate various body processes
(found in a nerve, the buncle of nerve fibres, one of the nerve fibres is a neuron) - sensory, inter, and motor neurons
glial cells
- non-conducting cells
- outnumber neurons by 50:1
- nourish neurons, remove their wastes, and protect against infection
- provide a supporting framework for the NS tissue
sensory neurons
- PNS
- take info from the environment to the CNS
- cell body is found midway through the axon
- myelinated
- enters spinal cord through the dorsal route
(ex. eyes, skin)
interneurons
- link neurons within the body
- found mainly in the brain and spinal cord
- CNS
- unmyelinated and shorter in length
- link sensory to motor
motor neuron
- PNS
- relay info from the CNS to the effectors (muscles/glands)
- myelinated
- leaves spinal cord through the ventral root
dendrites
- many
- highly branched
- recieve incoming signals
- conduct nerve impulses toward the cell body
cell body
- receives impulse from dendrite
- cell body –> axon
- contains all major cellular organelles
axon
- conduct nerve impulses toward other neurons or to effectors
- range in length from 1mm to 1m
myelin sheath
- many beads of schwann cells
- thick insulating material
- wraps many times around the axon
nodes of ranvier
- spaces between schwann cells (exposed axon)
- nerve impulse travels quickly from one node to another (saltatory conduction)
neurilemma
- surrounds the axon
- prevents regeneration of damaged axons
- on all nerve fibres in the PNS
axon terminal
- store neurotransmitters (chemicals that will be released to carry the message across the synapse)
5 essential components of a reflex arc
- receptor
- sensory neurony
- interneuron (in the spinal cord
- motor neuron
- effector
(in that order)
electrical nature of nerves
- depends on the movement of ions
across the axon membrane
non-voltage gated ion channels
- ions move via diffusion
some are: - open at all times
- stimulated by chemicals to open/close
voltage gated ion channels
- stimulated by a specific charge
- ions move via diffusion
Na+/K+ pump
- always active
- actively transports ions across axon membrane
- 3 NA+ OUT, 2 K+ IN
resting membrane potential/polarization
- -70mV (milivolts)
- negative on inside relative to outside
intracellular fluid
- inside the neuron
- has negative proteins (too big to leave)
- and negative ions (Cl-) (cant leave selectively permeable membrane)
- considered to be negatively charged overal
threshold
- -55mV
action potentials
- nerve impulses
- occur in the axon and the dendrites of certain sensory cells
- +35mV
impulse propagation
- action potential travels down the neuron (signal does not degrade)
- depolarization stimulates an action potential in the ajacent region that was at rest
saltatory conduction
- can only occur when the axon membrane is exposed
- one node of ranvier to another
- in myelinated neurons only
- shorter recovery
- less ion flow
- faster transmissions (150m/s)
continuous conduction
- every location of the membrane
- unmyelinated neurons
- slower transmissions (5m/s)
- longer recovery
intensity detection
increase stimulus –>
- more neurons are stimulated
- brain interprets a higher # of neurons firing as an increased intensity
- increased frequency of action potentials
the synapse
- small spaces between neurons or between neurons and effectors
neuromuscular junction
- synapse between a motor neuron and a muscle
excitatory neurotransmitters
stimulate action potential
- voltage becomes more positive (on the graph)
inhibitory neurotransmitters
prevent action potential
- voltage becomes more negative (on the graph)
hyperpolarization
when the membrane potential becomes more negative
summation
final outcome of the simultaneous release of excitatory and inhibitory neurotransmitters in a synapse
grey matter
unmyelinated neurons
neuroplasticy
ability of brain to form and recognize synaptic connections
white matter
myelinated neurons
hind brain
- oldest part of the brain
- controls basic life activities (breathing, heartbeat)
- includes the medulla oblongata, the pons, and the cerebellum
medulla oblongata
- 1st extension from spinal cord
- in the hind brain
controls: - heart rate
- breathing
- swallowing
- blood vessell diameter
- coughing
cerebellum
- in the hind brain
- “small brain”
- behind the medulla
- has grey and white matter
- recieves input from specialized sensors located within the skeletal muscles and joints
- coordinates and maintains fine control over all motor actions
- unconscious control of posture
pons
- in the hind brain
- between the medulla and midbrain
- has part of breathing control system
- relays messages from the cerebellum to the cerebrum, midbrain, and other hindbrain centres
midbrain
- above the pons
- made up of 4 bundles of grey matter
- relays visual and auditory info between areas of the hindbrain and forebrain
thalamus
- in the forebrain
- relays sensory impulses to the cerebral cortex –> then motor impulses to spinal cord
hypothalamus
- in the forebrain
- control center for part of the autonomic nervous system
- basic drives, emotions, and controls pituatary gland and endocrine systems
cerebrum
- largest part of the brain
- 2 hemispheres (right and left)
- in the forebrain
- recieves and processes ALL sensory info.
- grey matter on the outside white on the inside
corpus callosum
thick band of nerve fibres
- connects the cerebral hermispheres
cerebral cortex
- in the cerebrum
- internal mass of white matter, and a grey outer layer
- produces most distinctive traits
- sensory perception
frontal lobe
- voluntary movement
- personality
- speech, thought
- conscious thoughts
temporal lobe
- auditory and visiual
- sensory
- memory
parietal lobe
- recieves info from skin
- sensory (touch, temp, taste, pain, pressure)
occipital lobe
recieves visual info
dorsal
back
ventral
front
sensory-somatic nervous system
- external environment
- controls all muscle movement
- part of PNS
- voluntary control
sensory receptors
- converts energy of stimulus to action potential
- some adapt to continuos stimulation (ex. not hearing clock tick anymore)
processing sensory info
brain splits sensory input to various areas of the brain
types of receptors
- photo
- thermo
- mechano
- chemo
the 5 senses and which receptors they use
- taste (gustation) - chemo
- smell (olfactory) - chemo
- vision - photo
- hearing - mechano
- balance - mechano
smell
upper nasal cavity contains chemoreceptors called olfactory cells
touch
proprioceptors in muscles, joints = body position
eye layers
- sclera
- choroid
- retina
sclera
- outer eye layer
- protects internal structures and maintains the shape of the eye
cornea
- the front of the sclera layer
- bends light towards the pupil
- no blood vessels
- recieves dissolved O2 and nutriets from the aqueous
humour
choroid layer
- middle layer
- has blood vessels
- gets O2 and nutrients from blood vessels
- black interior that prevents stray light from bouncing inside the eye
iris
- front of the choroid layer
- thin, circular + radical muscles
- controls amount of light entering the eye
- muscles of the iris constrict/dilate the pupil
pupil
- black in colour because of melanin pigment
- constriction/dilation of the pupil is influenced by the parasympathetic/sympathetic nervous systems
lens
- behind the iris
- bends light to focus an image on the retina
- image is inverted on the retina
ciliary muscles + suspensory ligaments
modify the shape of the lens for a focused image
accomodation
changes in the lens shape
flattened lens
Far Flat
- further is in focus
rounded lens
Close Curved
- up close is in focus
retina
- innermost layer of the eye
- has photoreceptors (rods+cones)
rods and cones
- photoreceptors
- convert light energy into nerve impulses –> bipoar cells –> ganglion cells –> optic nerve –> occipital lobe
blind spot
- optic disc
- where the optic nerve exits to the brain
- photoreceptors are absent here
feild of view
- foveal and non-foveal
foveal
- central view
- foveal centralis of retina
- what you see directly in front of you
non-foveal
- peripheral vision
summary of vision
light, cornea, aqueous humour, pupil, lens, vitreous humour, retina/photoreceptors, optic nerve, occipital lobe
myopia and hyperopia
- near-sightedness
- far-sightedness
sections of ear
outer, middle, inner ear
outer ear
- external ear
- includes the pinna and auditory canal
pinna
funnels sound to the auditory canal
auditory canal
- part of the outer ear
- narrow tube that concentrates sound
- produces ear wax
- lined with little hairs
middle ear
- includes the tympanum, ossicles, and eustachian tube
tympanum
- eardrum
- transmitts sound to ossicles which amplifies the sound
- sound waves hit the tympanum –> vibrations
- air pressure on both sides of the tympanum must be equal for the tympanum to vibrate freely
ossicles
- three small bones
- moved by vibrations
- found in an air filled chamber
- last ossicle strikes the oval window
- continuous intense sounds –> muscles restrict movement of the ossicles and last ossicle moves away from the oval window to decrease intensity on cochlea
oval window
- gets vibrations from the tympanum and ossicles THREE times as loud
- gets pushed by the ossicles into the cochlea and moves fluid in the cochlea
- inner ear
eustachian tube
- in the middle ear
- extends from middle ear to the nose and mouth cavities
- equalizes air pressure
inner ear
- cochlea, semilunar canals, and vesibule
cochlea
- has specialized hair cells (mechanoreceptors)
- hair cells respond and identify sound waves of different frequencies and intensities
- sound waves get turned into fluid
hair cells of the organ of corti
- sense the bending of the stereocilia and synapse with the nerve fibres of the auditory nerve
- can distinguish the frequency (pitch) and amplitude (intensity/volume) of sound waves
frequencies
high - sensed by hairs nearest to the oval window
low - stimulates the hair cells that are further from the oval window
amplitude
- the louder the noise the greater the pressure
semicircular canals
- three fluid filled bone chambers
- have hair cells that detect the motion of fluids in the canals
- synapse with the vesticular nerve
- balances when moving
summary of hearing
sound waves –> auditory canal –> tympanum –> ossicles –> oval window –> organ of corti –> auditory nerve –> temporal lobe
