Download Body Systems - Bishop Ireton High School

Nervous
Function
 command unit
 provides senses
 sends signal between body and brain
 Responds to internal and external stimuli
Neuron
 Dendrite- impulse
passes here 1st
 Cell Body
 Axon- covered in
myelin- acts as insulator,
“white matter”-end at
axon terminal
3 types of neurons
 Sensory- carries impulse from body to brain or spinal
cord
 Motor- carries impulse from brain to muscle or gland
cell(target cell)
 Interneuron- connects brain to spinal cord
Impulse moves dendrite  cell body 
axon  target cell
How does impulse move along axon?
 Neurons have a charge(-70 mv) on the cell
membrane.This is due to more + ions on the outside of
the cell than on the inside.
 Neurons are excitable- charge can change
 This is called action potential- ability of membrane
to  or  charge.
Normal conditions of cell
 More Na+ outside
 This is the resting
More
K+inside
potential of a cell
 The cell is Polarized
because of the charge
difference.
 Impulse cause Na+ to rush into cell
(DEPOLARIZATION) through ion
gates
 K+ pushed out of cell
 Cell tries to bring back to normal
 Push Na+ out
 Push K+ back in(Reploarized)
 Causes impulse to move down
membrane to next ion gate
How does impulse travel so
quickly?
 Axon covered with an
insulator –MYELIN“White matter”
 Impulse jumps from
node to node
ALL OR NONE THEORY
 An impulse has only 1 strength
 It must be strong enough to start an impulse in a
sensory organ or reach the threshold level.
 If it reaches the TL then the impulse is transmitted, if
not- no transmission
How does impulse jump from axon
to next nerve or cell?
 Need to make connection between neuron and empty
space.
1. Vesicles filled with neurotransmitter
2. Vesicles fuse with membrane
3. Neurotransmitters released into synapse
4. Neurotransmitter binds to receptor site on next
neuron or target cell
5. Depolarization occurs in cell #2
6. Ion gates (K+ and Na+) open up
7. Impulse transmitted
Synapse
There are 2 parts to your nervous
system
 Central Nervous system- Spinal cord + brain
 Peripheral Nervous System- All nerves coming from
cord
Brain
 Protected in 3 ways:
Skull
2. Wrapped in connective tissue: Meninges
3 layers- inner-pia matter
middle- arachnoid
outer-dura matter
3. Cerebrospinal fluid- found between pia matter and
arachnoid layers and serves as a shock absorber
Brain must have constant supply of oxygen!!!
1.
BRAIN
 Cerebrum
 Brain Stem
 Cerebellum
Cerebrum: Site of Intelligence,Memory,Language
Movement of skeletal muscle(voluntary)
 2 halves- left brain/right brain
 Connected by CORPUS COLLOSUM- thick band of
connective tissue(So both sides can talk to each other)
 Each hemisphere is divided into 4 lobes: frontal,
parietal, occipital, and temporal. Has folds or
convolutions to add surface area.
 2 surfaces:
Cerebral cortex or grey matter is the outer surface
Cerebral medulla- white matter is the inner surface
that contains myelinated axons.
Brain Stem : 3 parts-connects brain to
cord
 Medulla Oblongata- breathing/ heart
rate/swallowing
 Pons -above medulla, links cerebral cortex and
cerebellum
 Midbrain -involved in hearing and vision
Cerebellum:
 Balance
 Posture
 Coordination
Two other parts of the brain are found between
brainstem and cerebrum
Hypothalmus-control center for hunger, thirst, fatigue,
anger, and temperature
Thalmus- switching station for sensory input, passes
info to cerebrum
 Brain is a source of weak electrical activity that can be
detected by an EEG(electroencephalogram)
 Sleep is when the cerebral cortex falls to its lowest
possible level
 Memory is thought to be short and long term
THE SPINAL CORD
 Emerges from the base of the skull
 Protected by bone, the vertebral column or backbone;
also the meninges and cerebrospinal fluid.
 Links the brain with the peripheral nervous system.
 Carries impulses to and from the brain and regulates
reflexes.
 A reflex is a response to a stimulus.
 31 pairs of spinal nerves branch out to the body from
the spinal cord.
 The spinal cord consists of 2 kinds of nerve tissue:
1.Central part is H shaped and consists of gray
matter
2.Outer part is the white matter and consists of
myelinated axons.
 Sensory neurons carry impulses from receptors to
the spinal cord.
 Motor neurons carry impulses from the spinal cord
to the effectors (glands/muscles).
 Interneurons connect the sensory and motor
neurons.
Peripheral Nervous System
 2 parts
 Sensory division- transmits impulses from sense
organs to CNS
 Motor Division- transmits impulses from CNS to the
effector(muscle, glands) This has 2 subdivisions:
Somatic
 12 pairs of cranial nerves
voluntary
31 pairs of spinal nerves
 Also controls reflexes- bypasses brain- signal goes
directly to spinal column
 sensory nerve  spinal column motor nerve 
target cell
Autonomic -automatic
 carries impulse from CNS to internal organs
 Involuntary

Sympathetic- controls during time of stress
“Fight or Flight”-increase heart rate, breathing,
temp,blood pressure

Parasympathetic- bring back to normal
Control during rest
Sensing Chemicals
 Chemoreceptors in mouth and nose
 Nose receptors- sense chemicals –impulse carried on
Olfactory Nerve- sent to brain
 Mouth receptors- taste buds on tongue (10,000)
Sweet, sour, salty, bitter
Eye
 consists of 3 layers:
1. outer layer contains the sclera or white of the eye which
2.
3.
consists of tough connective tissue and the cornea which is
the transparent covering of the eye. Between the cornea and
the sclera is the aqueous humor, a clear fluid.
middle layer is the choroid that contains the iris (colored part
of the eye) which has an opening called the pupil. Just behind
the pupil is the lens, that refracts incoming light. The eyeball
itself consists of a large chamber filled with jellylike fluid, the
vitreous humor.
inner layer is the retina located at the very back of the eye and
contains light sensitive cells called photoreceptor cells. This
is the place where light energy is converted into electrical
impulses.
Sensing light These cells contain the
pigment rhodopsin which is
sensitive to different
wavelengths of light. These
cells fall into 2 groups;
 Rods sense light and dark and
the
 Cones sense color.
 It is in these cells where light
is converted into impulses
that then travel to the brain
via the optic nerve.
Mechanical Stimulation
 Hearing- detect vibrations, sound waves
 Outer ear consist of auditory canal-collects vibrations
 Sound waves hit tympanic membrane (eardrum)
 Ear drum vibrates
 Vibration passed to 3 bones- malleus, incus, stapes
 Vibration passed to oval window- causes fluid in cochlea
to vibrate
 This causes little hairs in cochlea to bend
 Sends impulse to brain via auditory nerve
 Brain interprets
Balance- center located in inner
ear
 Sends info to brain
 Semicircular canal filled with fluid and hairs and ear
stones(otoliths-CaCO2)
 Stones lay on hairs
 Hair bends- stimulates nerve
 Sends impulse to brain
Touch- receptors in dermis
 Feel temperature, pressure, pain
 Receptors located in specific areas
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Light touch- tips of fingers, eyelids, mouth
Heavy touch- joints, muscles, palms
Free nerve endings- itch, tickle, hot, cold, pain
Pain- all over body, except brain
Heat- deep in dermis
Cold- near surface