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The Nervous System Evelin Morales Period 5 (Drugs that affect the brain,…
The Nervous System
Evelin Morales Period 5
Action Potential
strong enough stimulation/ stimulus causes Na+ gates to open
Na+ rush into cell causing depolarization
-70mV + 30 mV
nerve impulse is transmitted during action potential
2.if a strong enough depolarization occurs, threshold potential is reached and impulse is sent down axon
K+ rush out of neuron after Na+ rushes in, depolarizes membrane
membrane is hyper polarized- too many K+ leave the cell. Membrane potential dips below resting potential.
Final Step= resting membrane potential is restored
Neurotransmitters
2 or 3 different neurotransmitters
bind to specific receptor molecules, opening ion channels and thereby stimulating impulse conduction by the membrane
Definition- chemical compounds release from axon terminals (of a presynaptic neuron) into a synaptic cleft
some degraded by enzymes
some reuptake into cells
Spinal Cord Structure
Inner portion is an H- shaped core comprised of gray matter= dendrites and cell bodies of neurons
Outerr portion is formed by columns of white matter, which is made up of spinal tracts= bundles of myelinated nerve fibers
occipital bone to the first lunar vertebra
Ascending tracts: sends impulse up towards the brain
Descending tracts: sends impulses down the cord from the brain
Spinal cord Functions
2.
if any injury cuts across the entire spinal cord, impulses cannot travel anywhere below the injury, which leads to...
Paralysis: loss of ability to make voluntary movements
Anesthesia: loss of sensation
1).
contains centers for thousands of reflex arcs in the spinal cord
Spinal cord reflex: reflex that result from
Interneuron: transfers sensory impulses to outgoing motor impulses
Jerk reflex
Withdrawal reflex
Coverings of Brain and Spinal Cord
Dura mater: tough, outer layer lining the vertebral canal
Pia mater: innermost membrane surrounding the actual cord
Arachnoid matter: membrane in between the dura mater and the Pia mater (like a cobweb; remember, "arachne" means spider)
Main Divisions of the Nervous System:
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
Two Division of PNS:
Sensory (afferent) Nerves
they are affected by the environment or sense the environment
Interneuron- nerves that connect sensory nerves to motor nerves
relay information from skin, muscles, and glands to CNS
Motor (efferent) Nerves
they cause an effect or response
carry impulses from CNS to organs muscles
2 types- Somatic nervous system and Autonomic nervous system (ANS)
Motor Neurons:
2 types of motor neurons
1.Somatic motor neurons
conscious voluntary control
sense and respond to external environment
Autonomis motor neurons
respond to interna environment
automatic, unconscious, involuntary control
Structure of a Neuron
Dendrite- receives impulse and sends signal to the cell body
Cell body- metabolic center
Axon- conducts signal away from the cell body
Myelin- fatty substance that insulates signal , and allows signal to be sent faster
Node(s) of Ranvier- spaces between myelin/ Schwann cells
3 types of Neuron structure:
multipolar- many dendrites, one axon
bipolar- one dendrite, one axon (sensory)
unipolar- fused axon and dendrite (sensory)
Nerve Coverings:
= made up of fibrous connective tissue
Fascicle= a group of nerve fibers (group of wrapped axons)
Endoneurium- surrounds individual fibers within a nerve
Perineurium- surrounds a group of nerve fibers
Epineurium- surrounds the entire nerve
Reflex Arc.
= pathway of a reflex response
5 parts of reflex arc:
sends signal to CNS
connection
delivers response
sensory receptor- nerve ending detects stimulus
target organ responds
Name of all the lobes and their function
Frontal Lobe
personality/ emotions/ intelligence
Precentral gyrus= Primary Motor Cortex
logic/ problem solving
attention/ concentration
controls conscious movement of skeletal muscle
Broca's area- ability to vocalize words (usually L hemisphere)
Temporal
hearing, speech, memory, sequencing and organization
Occipital Lobe
processes vision (visual cortex)
Parietal Lobe
size, shape, color, pain, temperature and speech
Post- central Gyrus= Somatic Sensory Area- interprets sensory info
Compare and contrast the autonomic system
the ANS can be subdivided into the parasympathetic nervous system (PSNS) and the sympathetic nervous sytem (SNS)
the somatic nervous system (SoNS) is the part of the peripheral system
associated with the voluntary control of body movements throughout the skeletal muscles and mediation of involuntary reflex arcs
Subdivisions of the nervous system
the nervous system is comprised of two major subdivisions, the central nervous system (CNS) and the peripheral system(PNS)
Major part of the brain (4 Major Regions)
1.Cerebrum (Cerebral Hemispheres)
has gray matter, white matter and basal nuclei
largest mass of the brain (83%)
superior part of the brain composed of two hemispheres( "higher brain")
allows us to remember the past, plan for the future, and imagine tings that have not happened
responsible for voluntary or conscious activities
Gyrus (gyro)= bump, elevated ridges of tissues
Fissures= deeper grooves, usually separate large parts of the brain
the longitudinal fissure divides the cerebrum into Land R hemispheres (L hemisphere controls r side of body)
sulcus(sulci)= creases, shallow grooves
Brain Stem
B. Pons: relay between cerebrum and cerebellum
C. Medulla oblongata: reflex center for heart rate, B.P. treating, vomiting, and swallowing
A. Midbrain: reflex center for vision and hearing
Reticular Formation controls wale/ sleep cycle
Cerebellum
10% of brain volume but over 50% of the total number of neurons in the brain
damage causes ataxia= clumsy movements and loss of balance
muscles of body to move smoothly
equilibrium and balance (and posture)
Diencephalon
contains 2 main parts:
Thalamus
relays sensory info., recognizes good vs. bad sensation
Hypothalamus
controls body temp, water balance, metabolism and endocrine function...
a part of the limbic system (thirst, appetite, sex, pain, and pleasure)= "lower brain"
sits on top of the brain stem
The layers of the meninges
Meninges= three layers of tissue that cover and protect the brain
membranes located between bone and soft tissues of nervous system
Outer= Dura Matter (tough mother)
Inner= Pia Mater (gentle mother) covers every fold of brain
Middle= Arachnoid mater (looks like cobweb)
Spaces and Ventricles
Cerebrospinal Fluid (CSF)
protects, cushions, nourish brain and spinal cord
ependymal cells from a blood- cerebrospinal fluid barrier
formed by choroid plexuses
protecting brain from harmful substances (and therapeutic drugs)
Blood-Brain Barrier protects from toxins in blood
C.S.F. (Cerebrospinal Fluid)- watery "cushioning" that the brain floats in
Spinal Tap
removing CSF from the lumbar region of the spinal cord
used for diagnosis or treatment
Function of neuron
are electrically excitable cells in the nervous system that function to process and transmit information
neurons also known as neurons, nerve cells and nerve fibers
in vertebrate animals, neurons are the core components of the brain, spinal cord and peripheral nerves.
Classification of neurons
sensory neurons (afferent neurons) are unipolar, bipolar, or multipolar shaped cells
these cells conduct action potentials toward or into the central nervous system
nerve cells are functionally classified as sensory neurons, motor neurons, or interneurons
Diseases associated with the brain
Concussion- shaking of the brain, no permanent damage, mostly result of swelling; loss of consciousness; dizziness; headache
Contusion causes tissue destruction, permanent damage
Intracranial hemorrhage- bleeding in the skull, edema; (skin Baby Syndrome)
Dementia
"Forgetfulness"
destruction of neurons
degenerative and irreversible
loss of brain function
affects memory, language, attention span, intellect, personality, cognitive skills
most common type is Alzheimer's
Parkinson's disease, multiple sclerosis, or Huntington diseases are a few other that can lead to dementia
CVA (Cerebrovascular Accident) - aka stroke- blood flow to brain tissue is blocked causing cell death.
Drugs that affect the brain
A combination of opiates (heroin or prescription painkillers) and alcohol can be especially dangerous.
In the United States, prescription opiates are the cause for kore deaths by overdose than any other single drug.
Most people who overdose are under the influence of more than one drug.
Most of these deaths ultimately result from respiratory failure.
Poly drug Cocktails: Opiates and Alcohol
Alcohol overdose occur mainly in two ways.
FIRST, by decreasing the excitatory effect of glutamate, alcohol causes unconsciousness.
At high levels, it can also slow or stop breathing.
Second the body tries to get rid itself of unabsorbed alcohol by emptying the stomach.
Nicotine
It is possible to overdose on nicotine by using combinations of nicotine patches or nicotine gum and cigarettes at the same time.
sometimes, nicotine can reach levels high enough to paralyze the muscles that control breathing or cause a heart break.
Smoking cigarettes can kill by causing lung cancer, but it cannot lead to a nicotine overdose.
Cocaine and Other Stimulants