Transcript The Nervous System

»Ever wonder how you can do
everything you do?
1 Allows us to sense our external environment as
well as sense changes internally.
2 Movements (actions both involuntary and
voluntary)
3. Allows us to have memory and intelligence –
Thinking!
4. Helps maintain homeostasis by detecting
changes either on the outside or inside and
allowing your body to react appropriately.
» Nervous tissue consists of:
˃ Neurons
+ Main functional unit of nerve tissue
+ Transmit nerve impulses
+ Comprised of: cell body, dendrites, and axons
˃ Neuroglia
+ Provide to the neurons:
– Support
– Insulation
– Nutrients
+ Relay signals for differentiation of neurons from progenitor cells
»Central Nervous System (CNS) = brain and
spinal cord
»Peripheral Nervous System (PNS) = cranial and
spinal nerves and are information lines (like
corded telephones)
» The CNS is the control center. It
houses the brain and spinal
cord.
» The PNS is the message center.
It connects the CNS to the rest
of the body.
» Sensory receptors
˃ At the end of peripheral nerves
˃ Gather in formation
+ Inside and outside of the body
+ Monitor temperature and O2 levels
+ Monitor external environmental factors
˃ Convert information to nerve impulses that transmit over the PNS to the CNS
+ Integration occurs to translate sensation into perception
– Create sensations
– Add memory
– Help produce thoughts
˃ Because of this we make conscious or subconscious decisions and then use motor
functions
» Motor functions
˃ Employ PNS, which carry information from the CNS to the effectors
˃ Effectors are outside of the nervous system and controlled by the nervous
system
+ Muscles or glands
˃ Divided into two categories
+ Somatic nervous system
– Voluntary motions
– Skeletal muscle
+ Autonomic nervous system
– Involuntary motions
– Cardiac muscle, smooth muscle, and various glands
˃ Actions counteract changes detected, therefore helping to maintain
homeostasis
1. Neurons: the basic cell and functional unit
of the nervous system.
˃
They transmit information to the body in the
form nerve impulses.
2. Nervous Tissue: Bundles of neurons or
nerve cells put together.
3. Neuroglial cells: supporting cells in the
nervous tissue.
1. Function: Fill in spaces, provide structural
frameworks, produce myelin, carry on
phagocytosis
2. Types:
˃ Microglial, Oligodendrocites, Astrocytes,
Ependymal, Schwann cells
» Microglial cells
˃ Scattered throughout CNS
˃ Phagocytize bacterial cells and other cellular debris
˃ Form scars in areas of damage
» Oligodendrocytes
˃ Align along nerve fibers
˃ Provide the insulating layer of myelin – myelin sheath
» Astrocytes
˃
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˃
˃
˃
Found between neurons and blood vessels
Provide structural support
Join parts by abundant cellular processes
Regulate concentrations of nutrients and ions
Can also form scar tissue within CNS
» Ependymal cells
˃ Form an epithelial-like membrane
+ Covers specialized brain parts
+ Form inner linings of enclosed spaces in brain and spinal cord
» Schwann Cells
˃ Found in PNS
˃ Produce myelin sheath around axons of myelinated neurons
Conducts impulses
to the neuron
Conducts impulses
to the body
Neuron structure explained:
» 1. Cell body: Contains the nucleus and organelles.
» 2. Dendrites: The part that receives the signal from
sensory neurons or other neurons.
» 3. Axon: The part that conducts the nerve impulse
(The highway it travels down)
» 4. Myelin sheath: protects the axon
» 5. Nodes of Ranvier: The gap where there is no
sheath protecting it.
» 6. Axon Terminal: The end where impulses are sent
out to another nerve.
Depending on what your body needs to do- there are
different types of neurons.
1. Bipolar
(interneuron)
2. Unipolar
(Sensory)
3. Multipolar
(motor)
1. Each neuron is either a Sensory Neuron, a
Motor Neuron or an Interneuron.
1. SENSORY NEURON: Your body senses something and
sends a message to your brain or spinal cord. Afferent=
bring messages into the brain.
2. MOTOR NEURON: It stimulates muscles to contract, or your
body to “do” something either voluntarily or involuntarily.
Efferent= send information away from brain to body.
3. INTERNEURON: Lie within the CNS and link other neurons
together. They transmit impulses from one part of the
brain or spinal cord to another.
1. Autonomic nervous system – controls
everything we don’t think about.. Smooth
muscles, glands, breathing, etc. =
involuntary movement
2. Somatic nervous system – controls the
skeletal muscle = voluntary movement
1. Use the book and your notes to create a foldable
about the different types of neurons.
2. You may fold it anyway you like as long as on the
outside you have three flaps (1 for each of the types
of neurons)
3. The outside you will need to draw what each neuron
looks like and label it.
4. The inside will answer the following info:
1. Where it is located.
2. Something about the number of axons and dendrites.
3. If it is a sensory neuron, interneuron, or motor neuron
and what that means.
4. Is it afferent or efferent.
5. One piece of other information.
1. The brain is composed of about 100 billion
multipolar neurons and even more nerve
fibers to communicate.
2. Divided into three major portions: The
cerebrum, cerebellum, and the brain stem
1. Cerebrum controls sensory and
motor functions, higher mental
functions – memory and reasoning
(Divided into sections)
2. Cerebellum coordinates voluntary
muscle activity
3. Brain stem regulates visceral
activities and connects various parts
of the nervous system
1. The Frontal Lobe
2. The Parietal Lobe
3. The Occipital Lobe
4. The Temporal Lobe
1. Forms the anterior portion of each
hemisphere (Your brain is divided into left
and right portions).
Functions:
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How we know what we are doing
within our environment
(Consciousness).
Controls our emotional response.
Controls our expressive language.
Observed Problems:
• Loss of simple movement of various body parts
(Paralysis).
• Inability to plan a sequence of complex
movements needed to complete multi-stepped
tasks, such as making coffee (Sequencing).
• Inability to express language (Broca's Aphasia).
Location: Posterior to the frontal
lobe, on the top part of the
cerebrum.
Function:
•Location for visual attention.
•Location for touch perception.
Observed Problems:
•
•
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Inability to locate the words for writing.
Problems with reading.
Difficulty with drawing objects.
Difficulty in distinguishing left from right.
Difficulty with doing mathematics.
Inability to focus visual attention.
Difficulties with eye and hand coordination.
Location: Most posterior, at the
back of the head/brain.
Function:
•Vision control center.
Observed Problems:
•Defects in vision
•Difficulty with identifying colors
•Production of hallucinations
•Difficulties with reading and
writing.
Location: Laterally (each side of brain close to
the ears.
Function:
•Hearing ability
•Memory
Observed problems:
•Difficulty in recognizing faces.
•Short-term memory loss.
•Right lobe damage can cause persistent talking.
•Increased aggressive behavior.
Deep in Brain, leads to spinal cord.
Functions:
» Breathing, Heart Rate, Swallowing, Reflexes to seeing and
hearing, controls sweating, blood pressure, digestion,
temperature (Autonomic Nervous System). Anything you
Can’t Control.
» Sense of balance (Vestibular Function).
Observed Problems:
» Decreased vital capacity in breathing.
» Problems with balance and movement. Dizziness and
nausea.
» Sleeping difficulties (Insomnia, sleep apnea).
» Includes midbrain, pons, and medulla oblongata
» Midbrain –vision reflex and auditory reflex
» Pons – relay sensory impulses from peripheral
nerves to the brain
» Medulla oblongata –controls the cardiac center,
blood vessel constriction, and respiratory center.
Located at the base of the skull.
Functions:
» Coordination of voluntary movement Balance
and equilibrium
Observed Problems:
» Loss of ability to coordinate fine movements.
Loss of ability to walk. Slurred Speech
The Spinal Cord
The Spinal Cord
» connected to the brain
» descends down the middle of the back and is
surrounded and protected by the bony vertebral
column
» surrounded by a clear fluid called Cerebral Spinal
Fluid (CSF), that acts as a cushion to protect the
delicate nerve tissues against damage from
banging against the inside of the vertebrae
» transmit electrical information to and from the
limbs, trunk and organs of the body, back to and
from the brain
Spinal Cord
» Cerebral Spinal Fluid:
Spinal
Nerves
There are four main groups of spinal nerves which exit
different levels of the spinal cord.
These are in descending order down the vertebral column:
1. Cervical Nerves "C" : (nerves in the neck) supply
movement and feeling to the arms, neck and upper
trunk. (8 total)
2. Thoracic Nerves "T" : (nerves in the upper back)
supply the trunk and abdomen. (12 total)
3. Lumbar Nerves "L" and Sacral Nerves "S" : (nerves
in the lower back) supply the legs, the bladder, bowel
and sexual organs. (5L and 5S)
Cranial Nerves
Pair of nerves
What is does
1.Olfactory
2. Optic
3. Oculomotor
smell
4. Trochlear
Carries motor impulses to the fifth
voluntary muscle of the eye
5. Trigeminal
Ophthalmic division = sensory fibers
from the surface of the eye, tear
glands, anterior scalp, forehead, upper
eyelids
Maxillary division = upper teeth, upper
gum, upper lip
Mandibular division = scalp behind
ears, skin of jaw, lower teeth, lower
gum, lower lip
vision
Raise eyelids, move the eye, controls
involuntary muscles of the eye, adjusts
amount of light into the eyes
Pair of nerves
What is does
6. Abducens
Moves the rest of the eye
7. Facial
Taste, anterior two-thirds of tongue,
facial expression
8. Vestibulocochlear
Vestibular branch = maintain equilibrium
Cochlear branch = hearing
9. Glossopharyngeal
Tongue and pharynx, tonsils, posterior
third of tongue
10. Vagus
Somatic= Larynx, swallowing, speech
Autonomic = heart and smooth muscles
11. Accessory
Cranial branch = soft palate, pharynx,
larynx
Spinal branch = neck muscles
12. Hypoglossal
Move the tongue for speaking, chewing,
swallowing
How does your brain
send out signals?
» The surface of a cell membrane is
usually electrically charged.
» When the charges are not equal it
is said to be polarized and is VERY
IMPORTANT in sending Nerve
impulses to and from the body CNS
to the PNS!
» The difference in electrical charge between the
inside and outside of a cell is called the
POTENTIAL DIFFERENCE.
» In a nerve cell that is “RESTING” or not sending
impulses this difference in charges is called the
RESTING POTENTIAL
» As long as the nerve cell remains undisturbed or
the charges do not change it will remain in a
resting potential state.
» Action Potential:
1. Electrical charges change by sodium channels
opening and allowing positive sodium into the cell.
This makes it positive. And is called
DEPOLARIZATION
2. Soon after potassium channels open and allow
potassium in ions in again bringing the charge back
to negative. This is called REPOLARIZATION
The action potential is the rapid change from
Depolarization to Repolarization which causes
an impulse to be sent through the neuron
» A wave of action potentials that move
down the neuron and axon until they
hit either another neuron or body cell
to transmit the impulse.
» Nerve Pathways- when nerve impulses
travel from neuron to neuron.
» The junction between two communicating
neurons is called the synapse.
» The neurons DO NOT TOUCH- there is a gap
that separates them
1. An Impulse (action potential) travels from the
dendrite to the cell body and then the axon to
the axon terminals (or end of the neuron).
2. At the end of a neuron or synapse,
NEUROTRANSMITTERS are released from the
axon terminals.
3. Neurotransmitters diffuse to the next neuron
or body cell.
» The simplest nerve pathways that are only a
few neurons long are called REFLEXE ARCS.
» Reflexes are automatic subconscious responses
to changes within or outside the body.
» Example: The Knee-Jerk reflex: Only 2 neurons.
A sensory neuron communicating directly with
a motor neuron.
Page 221222 in book
Knee Jerk
activity