THE NERVOUS SYSTEM
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Transcript of THE NERVOUS SYSTEM
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THE NERVOUS SYSTEM
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A. TWO PARTS Central Nervous System(CNS)-
brain/spinal cord Peripheral Nervous System(PNS)-nerves
through the body 31 pairs of spinal nerves 12 pairs of cranial nerves
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B. 3 BASIC FUNCTIONS1. Sensory- gathers info
- receptors of PNS send signals to CNS2. Integrative- info is brought together
- interpreted, create sensations, create thoughts, add to memory, make decisions
3. Motor – response to signals (impulses) Signals sent from CNS to muscles/glands Homeostasis- maintain stable conditions
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MOTOR: Somatic Nervous System- skeletal
muscles Autonomic Nervous System- smooth
muscles, glands
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C. NEURONS-NERVE CELLS Body with many extensions(nerve
fibers) that conduct impulses 2 types of processes
Dendrites- shorter more numerous Receive input
Axons- single long fiber Conducts impulse away
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D. NEUROGLIAL CELLS Support tissue of the nervous system 5 Types1. Microglial : scattered throughout,
digest debris or bacteria
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2. Oligodendrocytes: provide insulation around the axons
Creates myelin sheath that insulates axons
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3. Astrocytes: connect blood vessels to neurons
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4. Ependymal Cells: form a membrane that covers brain-like parts
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5. Schwann cells: form the insulating sheath around the neurons within the PNS
*Myelin Sheaths - necessary for insulation of neurons
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NEURON STRUCTURE Cell body- contains cellular organelles Neurofibril - fibers- support organelles Chromatophilic substance (rough ER) -
transport system Myelin -insulation surrounding axons Nodes of Ranvier - gaps in the
insulation Synaptic cleft- space between neurons
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WHITE VS GREY MATTER Myelinated (white matter) – myelinated
axons Unmyelinated (grey matter) -
unmyelinated
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ALL NEURONS DO THREE THINGS:1. Receive a signal.
Can be any type of stimulus (change in environment, signal from another neuron, etc).
2. Transmit a signal to another location. Ex: finger touching something • signal to spinal
cord or brain.3. Stimulate another cell
Another neuron • transmit signal Muscle • contraction Gland • secretion
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CLASSIFICATION OF NEURONSStructural
- Multipolar- Bipolar- unipolar
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Functional- sensory neurons- motor neurons- interneurons
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Nerve- bundle of nerve fibersNerve Impulse- weak electric current
- series action potential along a nerve
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SYNAPSE Presynaptic neuron- brings impulse to
synapse Postsynaptic neuron- neuron
stimulated/inhibited by impulse Synaptic Transmission- signal
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Axon end- hold neurotransmitter
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NEUROTRANSMITTERS Excitatory - increase membrane
permeability, increases chance for threshold to be achieved
Inhibitory - decrease membrane permeability, decrease chance for threshold to be achieved
Synaptic Transmission Dendrite cell body axon synapse
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STEPS1. Neuron membrane maintains resting potential2. Threshold stimulus is received3. Sodium channels open4. Sodium ions diffuse inward, depolarizing the
membrane5. Potassium channels open6. Potassium ions diffuse outward, repolarizing
membrane7. Resulting action potential causes a local bioelectric
current that stimulates adjacent portions of membrane
8. Wave of action potentials travel the length of the axon as a nerve impulse
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http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html
http://outreach.mcb.harvard.edu/animations/actionpotential.swf
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TYPES OF NEUROTRANSMITTERS Acetylcholine - stimulates muscle
contraction Monoamines - Norepinephrine &
Dopamine (sense of feeling good, low levels = depression)
Serotonin (sleepiness) Endorphins (reduce pain, inhibit
receptors)
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DRUGS THAT AFFECT NEUROTRANSMITTERS
Curare Strychnine Cocaine, morphine, alcohol, ether and
chloroform Mescaline and LSD Ecstasy
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ANTIDEPRESSANTS Zoloft is part of a class of drugs called
selective serotonin reuptake inhibitors, or SSRIs for short. SSRIs act on a specific chemical within the brain known as serotonin. This is one of several chemicals used to send messages from one nerve cell to another.
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IMPULSE PROCESSING Neuronal pool- Groups of neurons
making synaptic connections to perform a common function
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TYPES OF NERVES Sensory Nerves - conduct impulses into
the brain or spinal cord Motor Nerves - carry impulses to
muscles of glands Mixed Nerves - contain both sensory
and motor nerves
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NERVE PATHWAYS
Receptor-Detects stimulus
Sensory/Afferent Neuron
Central Nervous System-
processes informationMotor/Efferent
NeuronMuscle or Gland- reacts
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NERVE PATHWAYS Reflex Arc- simple pathway, includes
few neurons Reflex- simplest response Reflex Behavior- automatic,
subconscious response to stimuli Sneezing, heart beat, vomiting, digestion
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Knee-jerk reflex- stimulus knee- sensory nerve-spinal cord-motor nerve
Withdrawal reflex- occurs when you touch something painful
http://www.intelligencetest.com/reflex/index.htm
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CENTRAL NERVOUS SYSTEM Brain = cranial cavity spinal cord= vertebral canal Protection= Mengines- membranes locatedbetween bone and soft tissue
of nervous system
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MENINGES- 3 LAYERS Dura mater- outermost layer, blood
vessels, nerves Arachnoid mater- no blood vessels,
inbetween layer Pia mater- inner layer, contains many
nerves and blood vessels to nourish cells
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LAYER OF DURA MATER
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Cerebrospinal fluid= between arachnoid and pia maters
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SPINAL CORD Nerve column, passes from brain down
through vertebral canal 31 segments – each with a pair of
spinal nerves Spinal nerves- branch to various body
parts
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Cervical enlargement- supplies nerves to upper limbs (neck)
Lumbar enlargement- lower back, supplies nerves to lower limbs
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FUNCTION OF SPINAL CORD Conduct impulses, serves as center for
reflexes
Ascending tracts= carry sensory info to brain
Descending tracts= carry motor impulses from the brain to muscles/glands
Spinal reflexes- reflex arcs pass through the spinal cord
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BRAIN Cerebrum – largest, sensory and motor
functions, higher mental function (memory, reasoning)
Cerebellum – coordinate voluntary muscles
Brain stem – regulate visceral functions
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Balance and Coordination
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STRUCTURES OF THE CEREBRUM1. Cerebral hemispheres- mirror images2. Corpus callosum- nerve fibers that
connect hemispheres
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3.CONVOLUTIONS OF THE BRAIN Wrinkles and Grooves of the brain
gyri- ridges on brain Sulcus- deep grooves Fissure- very deep groove
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4. FISSURES Longitudinal fissure - separate right and
left sides Transverse fissure- Separates cerebrum
from cerebellum
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Lateral fissure- separates the temporal lobe from the Frontal and Parietal lobes
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LOBES OF THE BRAIN5. Frontal – reasoning, thinking, language6. Parietal – touch, pain, relation of body
parts (somatosensory)7. Temporal Lobe – hearing 8. Occipital – vision9. Cerebral Cortex - thin layer of gray
matter that is the outermost portion of cerebrum (the part with all the wrinkles)
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FUNCTIONAL AREAS OF BRAIN1. Motor- controls voluntary movements
- the right side of the brain generally controls the left side of the body
-also has Broca's Area (speech)
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2. Sensory Area-involved in feelings and sensations
(visual, auditory, smell, touch, taste)
Sensory HomunculusThis model shows what a man's body would look like if each part grew in proportion to the area of the cortex of the brain concerned with its sensory perception.
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3. Association Areas- higher levels of thinking, interpreting and analyzing information
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BRAIN STEM- 3 PARTS Midbrain – visual reflexes, eye
movements Pons - relay sensory information Medulla Oblongata– heart, respiration,
blood pressure
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Diencephalon1. Hypothalamus – regulates hormones,
heart rate, blood pressure, body temp, hunger, sleep
2. Thalamus - relay station
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Optic Tract / Chiasma - optic nerves cross over each other
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MEMORY: HIPPOCAMPUS Memory is controlled by the
HIPPOCAMPUS The hippocampus plays a major role in
forging memories.
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EMOTIONS: LIMBIC SYSTEM The prefrontal lobe and the hippocampus are part of
a system of structures in the brain. The LIMBIC SYSTEM also includes olfactory lobes.
Therefore, memory, emotion, and smell are linked. Crayolas are created today with the same scent
because it reminds people of their happy times in childhood.
Why is the brain formed so that smell and emotions are tied together? Because pheromones are tied to emotions and behavior, so they need the link.
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MEMORY We used to classify memory as being
long-term or short-term. The new classification is four memory systems that process information for storage and retrieval:
Episodic, Semantic, Procedural, and Working.
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EPISODIC Involved in remembering personal
experiences, such as a phone conversation you had yesterday or the movie you watched last week.
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SEMANTIC Manages the storage and retrieval of general
knowledge of facts, such as the number of days in a year or the colors in a rainbow.
People with problems in this system may have difficulty in naming an object or describing a named object.
Semantic Memory Tasks 1. What month comes after October? 2. Where do Kangaroos live? 3. What actor played the Joker in the last Batman
movie?
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PROCEDURAL Allows us to learn activities and skills
that will then be performed automatically with little or no conscious thought. Examples are riding a bicycle or driving a
car. Problems with this system leads to loss of
skills or significant difficulties in learning new skills.
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WORKING Governs attention, concentration, and short-
term retention. Problems here can impair her a person's
ability to pay attention or to accomplish multi-step tasks.
Working Memory Tasks 1. Labeling a skeleton (remember that chapter?) 2. Describing the parts of the brain. 3. List all the things you ate yesterday. Test Working Memory
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PHINEAS GAGE