Transcript The Nervous System

The Nervous System
Chapter 13 Human Biology
Objectives
Describe the structure and function of tissues and organs of the nervous system.
Compare the nervous system in humans to other animals.
Research and report on technology related to organs.
Nervous system
Receives sensory input from the skin, nose, mouth, eyes, ears, and all parts of the
body and sends those signals through the spinal cord to the brain.
Processes information from all parts of the body, reviews, sorts, stores as memories
and creates a movement or motor response.
The smell of baked cookies or bread evokes pleasant memories of dunking some in
some milk, so you decide to get some.
Generates motor or movement output to muscles, glands, and organs.
The salivary glands secrete enzymes to digest food.
The stomach generates acids and enzymes to digest the cookies.
You grab a cookie or make a dozen baked cookies.
Comparative brains
Comparative brains
Nervous cells make up nervous tissue
Neurons transmit nerve impulses of electricity.
Neuroglial cells support and nourish neurons.
Sensory neurons- receptor cells that connect to the brain and detect changes.
Interneurons- Inside the brain and spinal cord, sum up information before sending it
to the brain.
Motor neurons- send impulses to the muscle, organ, or gland.
Effectors- carry out responses to the environment, both internal and external
environment. https://www.youtube.com/watch?v=rWrnz-CiM7A
Neuron- 3 parts
Cell body, Dendrites, Axon
Cell body- nucleus and organelles
Dendrites- short extensions that receive
signals
Axon- long nerve fibers that conduct nerve
impulses from sensory neurons and
receptors.
Interrupted by the cell body.
Some neurons have a myelin sheath (lipid
substance) that insulates the neuron as
does an electrical wire.
Some neurons have short axons without a
myelin sheath.
Discoverer of neuron structure &
function
Santiago Ramon Y Cajal (1906 Nobel Prize) found that there are axon terminal buds,
very close to a dendrite or another cell body but they don’t touch. This space is called
a Synapse or a Synaptic Cleft. https://www.youtube.com/watch?v=pBd7AJk1drY
One neuron sends a signal to the next neuron which receives the signal.
Calcium ions enter the cell, vesicles fuse with the plasma membrane, include
neurotransmitters- these bind to receptor proteins on the receiving cell membrane.
Sodium ions diffuse into the receiving neuron making an electrical impulse.
Schwann cells- found in the peripheral
nervous systemSupport neurons
Have myelin in plasma membranes.
Gaps are called Nodes of Ranvier
Two types of brain matter
Gray matter- cell bodies that are not myelinated in the
brain and spinal cordWhite matter- myelinated tracts- takes information to
the brain from the spinal cord and to other areas of the
brain.
People with Multiple Sclerosis have no myelin on their nerves.
Myelin helps regenerate a nerve
Left brain controls the right side of the body and the
right side of the brain controls the left side of the body.
Nerve function
A nerve conducts electricity (0.070 volts or 70 millivolts), by making the inside more
negative and the outside of the cell more positive.
Active transport pumps Sodium inside and Potassium outside the cell.
Inside the cell there are more negatively charged proteins.
Through Sodium-Potassium protein pumps.
https://www.youtube.com/watch?v=fHRC8SlLcH0
Charges
Switching ions of Sodium and Potassium produces a temporary positive charge
outside, and a temporary negative charge inside. It lasts about 3-4 milliseconds.
Pain receptors don’t activate until the charge reaches a threshold voltage of -40
millivolts.
It’s an all-or-nothing response.
Protein channels open for Sodium ions in the axon’s cell membrane. Sodium ions go
inside the cell and when the gates close Potassium gates open and Potassium exits
the cell.
Unmyelinated axons are slower
Myelinated fibers allow the electrical impulse to jump nodes of Ranvier.
They are self-propagating along the length of the axon.
Once a signal passes down the axon, the cell can’t conduct another impulse for a
short time, called the refractory period.
Excitatory or Inhibitory
Excitatory- acetylcholine causes the Sodium gate to
open
Inhibitory- causes Potassium to exit the receiving
neuron.
Enzymes deactivate neurotransmitters.
Acetylcholinesterase deactivates acetylcholine.
Others repackage and reabsorb the neurotransmitter so
a new signal can be sent.
Neurotransmitters
100+ neurotransmitters
Acetylcholine (AcH) stimulates skeletal muscles, inhibits cardiac muscles
Norepinephrine (NE) –stimulates smooth muscles, active in dreaming, waking, and
moods
Dopamine- euphoria, allows muscles to contract
Serotonin- helps regulate body heat, sleep, emotions, and perception
Glutamate
GABA (Gamma Amino Butyric Acid)- reduces excitation.
Two more neurotransmitters
Melatonin- helps patterns of sleep, it is produced in the pineal gland in the brain at
night.
Endorphins: Temporarily block pain signals to the brain
https://www.youtube.com/watch?v=haNoq8UbSyc
Spinal Cord and Brain
Meninges wrap around
the spinal cord and the
brain
Meningitis is a viral or
bacterial infection of
the meninges.
1500 people die
yearly from
Meningitis.
Spinal cord
Has ascending tracts that take messages to the brain
Has descending tracts that take messages to muscles, organs, and glands.
Spinal cord and brain
Spinal cord exits the brain through a hole called the foramen
magnum
Spaces in the spine are called intervertebral foramen
Fibrocartilage between intervertebral disks.
Doctors perform a spinal tap, which withdraws a small amount of cerebrospinal fluid from between the
vertebrae with a large needle.
Spaces between the meninges, the ventricles of the brain, and the central canal
of the spinal cord are filled with cerebrospinal fluid.
Breaks in the spinal cord
Paraplegia- thoracic cut or break in the spinal cord that results in lack of use of legs
Quadraplegia- break in the neck or cut in the spinal cord can result in loss of use of
the arm and leg.
Brain anatomy
4 ventricles that contain cerebrospinal fluid.
Lateral left and right
3rd in the middle
4th inferior to the 3rd and by the cerebellum or base of the brain.
Areas
Cerebrum has four lobes
https://www.youtube.com/watch?v=SNuZ4OE6vCk
https://www.youtube.com/watch?v=FYm4RtB
QncQ&nohtml5=False
Frontal lobe
Receives information from all parts of the brain in order to reason and plan our
actions.
Association areas of the brain
Four areas in
the cerebrum
where
memories are
stored
Decide if
sights,
sounds, and
feelings are
mom, dad,
dog, cat, car,
etc…
Pineal gland- produces melatonin for
sleep.
Pituitary secretes hormones that
control various body functions like
growth, metabolism, milk
production
Primitive Brain stem parts
Posture, balance, coordination.
Diencephalon- thalamus
surrounds the 3rd ventricle and
hypothalamus (below the
thalamus)
Brain stem- visual, auditory and
touch senses:
midbrain is the relay between
cerebrum and rest of brain
Pons- relays touch, facial
movements, bladder control
Medulla oblongata controls
breathing, heart rate, blood
pressure
Hippocampus- memory formationpus
callosum
Corpus callosum- fibers that connect the left and
right hemispheres of the brain.
https://www.youtube.com/watch?v=82tlVcq6E7A
Video of a person who had his corpus callosum cut
to prevent seizures.
https://www.youtube.com/watch?v=PzT_SBl31s&nohtml5=False
Ted Talk Teenage Brain
https://www.youtube.com/watch?v=UyyjU8fzEYU&
nohtml5=False
Ted Talk Brain
Assessing risks and planning actions
Done in the basal ganglia along with
the frontal lobe.
They allow one goal to function by
inhibiting other goals.
Limbic System
Hypothalamus, Thalamus, Amygdala
Process emotions
https://www.youtube.com/watch?v=LNs9ruzoTmI&nohtml5=False
Touch
Rapid pressure change
Vibration, Coarseness
Skin stretch
Pressure
Temperature,
Position,
Movement
Touch sensors
Merkel disks- detect pressure
Free nerve endings detect position and movement
Ruffini corpuscles- detect skin stretching
Meissner’s corpuscles- detect rapid pressure changes
Pacinian corpuscles- myelin sheath detect vibration and coarseness.
Hearing
https://www.youtube.com/watch?v=P5gyQf2gVvA
Video on the ear
https://www.youtube.com/watch?v=0CRMLN8hHA&nohtml5=False
Sight
Rods- detect light, Cones- color
https://www.youtube.com/watch?v=AuLR0kzfwBU&nohtml5=False
Different organisms’ eyes perception of
colors
Cat, Snake, Bird
Birds, fish, amphibians, and reptiles have 4 types of cones
Allows them to see in ultraviolet spectrum
Gulls, terns, and albatrosses have yellow oil droplets to improve vision in hazy
conditions.
Humans have 3 types of cones
Video on the eye
https://www.youtube.com/watch?v=gvozcv8pS3c
Taste
Smell
& Taste