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functions of the nervous system (5)
1. Sensory input - monitor temp, sight, smell, taste
2. Integration - make sense out of it, see entire picture
3. Controls of muscles and glands - voluntary or involuntary
4. Homeostasis - primary control. either electrical or chemical
5. Mental activity - using your mind
1. Peripheral nervous system (PNS)
a. Afferent division - coming outside in to CNS
b. Efferent division - going out to muscles or glands
c. Somatic nervous system (SNS) - controls movement of body. skeletal muscle
d. Autonomic nervous system (ANS) - you don't control. ex. heart, lungs, urinary, digestive, glands
- Sympathetic division - fight or flight
- Parasympathetic division - rest & restore
Somatic nervous system (SNS)
Somatic nervous system (SNS) - controls movement of body. skeletal muscle
Autonomic nervous system (ANS)
you don't control Ex. heart, lungs, urinary, digestive & glands
1. Sympathetic division = fight or flight
2. Parasympathetic division = rest & restore
Properties of Neurons (3)
Neurons = bundles of nerve fibers
1. Excitability (irritability)
- Ability to respond to stimuli
2. Conductivity (UNIQUE) - using ions & polarity
- Produces traveling electrical signals
- Neurotransmitter = releases chemical messanger
Cells of the nervous system (2)
1. Neurons - excitable cells
2. Glia - support function of neurons ( electrical) Without the nervous system wouldn't survive
a. Astrocytes (CNS)
b. Microglia (CNS)
c. Ependymal cells (CNS)
d. Oligodendrocytes (CNS)
e. Schwann cells (PNS)
1. Processes cover the surfaces of neurons and blood vessels and the pia mater. Wraps around capillaries & neurons
2. Blood-brain barrier: protects neurons from toxic substances, allows the exchange of nutrients and waste products between neurons and blood, prevents fluctuations in the composition of the blood from affecting the functions of the brain.
Blood-brain barrier (3) ON TEST
1. protects neurons from toxic substances
2. allows the exchange of nutrients and waste products between neurons and blood
3. prevents fluctuations in the composition of the blood from affecting the functions of the brain.
-limits what can get out of capillaries & into the brain.
-Protects from chemicals, can be good or bad. You might need chemicals for your health (Ex. Parkinsons, lack of dopamine, but medical dopamine can't get thru barrier)
1. Line brain ventricles and spinal cord central canal.
2. Specialized versions form choroid plexuses.
3. Choroid plexus
a. Secrete cerebrospinal fluid.
b. Cilia help move fluid thru the cavities of the brain.
Found in vesicles, they make & circulate _________
1. Specialized macrophages.
2. Respond to inflammation, phagocytize necrotic tissue, microorganisms, and foreign substances.
Form myelin sheaths in CNS
White matter = myelin fatty tissue, insulates neurons w. myelin = transmission moves much faster
PNS (AKA neurolemmocytes) plasma cells of ________
1. Schwann cells or neurolemmocytes
- Wrap around portion of an axon to form myelin sheath.
Myelin between axon & PM
In PNS - neurons don't divide.
axon w/neurolemma, axon may regrow
axon w/o neurolemma won't regrow axon.
2. Satellite cells
a. Surround neuron cell bodies in sensory ganglia
b. Provide support and nutrients
Myelinated axons (5)
1. White matter
2. Protects and insulates axons from one another
3. Speeds transmission
4. Functions in repair of axons (if neurolemma)
5. Nodes of Ranvier (gap) impulse travels from gap to gap
1. Excitable cells that initiate and conduct impulses
b. Nissl bodies (pieces of RER producing neurotransmitters)
c. Dendrites - receives the message
d. Axon (only one) carries impulse away from cell body
i. Telodendria = (AKA axon terminal) end branches. at the end of these is the synaptic knob, which contain neurotransmitter.
ii. Synaptic knob
end branches. at the end of these is the synaptic knob, which contain neurotransmitter.
Structural classification of neurons (3)
a. One axon and several dendrites.
Note: MOTOR UNIT = ALL MULTIPOLAR but not all multipolar are motor
2. Bipolar (ex. eye, ear, nose = always SENSORY)
b. One axon and one dendrite. RARE
3. Unipolar (ALL SENSORY)
a. One process comes off neuron cell body
i. Divides into two fibers: central and peripheral fiber.
b. dendrites are myelinated b/c sensory impulses need to come in quick
Functional classification of neurons
1. Afferent (sensory) = UNIPOLAR
2. Efferent (motor) = MULTIPOLAR
3. Interneurons = multipolar, any neuron totally w/in CNS
Reflex arc = series of neurons that are protective (ex. hand touches something hot)
1. Three-neuron arc (most common)
a. Afferent neuron
c. Efferent neuron
2. Two-neuron arc
a. Afferent neuron
b. Efferent neuron
3. Ipsilateral reflex (same) Ex. poke right finger, move right finger
4. Contralateral reflex (opposite) Ex. walk & step on something w/right foot. Ipsilateral=pick up right foot. contralateral = stiffen left leg for balance.
Contralateral reflex (opposite) Ex. walk & step on something w/right foot. Ipsilateral=pick up right foot. contralateral = stiffen left leg for balance.
1. Where nerve signals are transmitted from one neuron to another. Axon comes close to another cell, muscle or gland
2. Two types: electrical and chemical
3. Presynaptic neuron (has to be a neuron)
4. Postsynaptic cell (in book its called postsynaptic neuron, but it can be a cell, gland or muscle.
Grow new connections, not grow new neurons
Nerve fiber repair (4)
1. Mature neurons are incapable of cell division
2. Limited capacity to repair themselves
3. Needs intact cell body and neurilemma and no scarring
4. Oligodendrocytes do not maintain a neurilemma
i. Fill damaged areas (replace neuron w/scar tissue)
ii. Block regrowth of axons
Note 1: if you kill cell body then neuron gone forever
Note 2: if in PNS---if cell body intact & neurolemma intact then cell may grow back
Note 3: schwann cell will help you determine if in PNS or CNS
Action potential - General (4)
(electrical activity w/in neuron)
1. Electrical signals produced by neuron
2. Function = Transfer of information from one part of body to another
3. Result from concentration differences of ions across plasma membrane and permeability of membrane
4. Series of action potentials AKA nerve impulse
Note: separation of charges. Every membrane is polar
Action potential - Membrane potential
1. Slight excess of positively charged ions on the outside of the membrane
2. Slight deficiency of positively charged ions on the inside of the membrane
because of sodium pump
Action potential - Resting membrane potential
1. Membrane potential maintained by a nonconducting neuron's plasma membrane
2. neuron isn't conducting impulse
Ion channels - general
1. gated channels
2. If you open potassium channel then potassium leaves.
3. open channels --- moves faster than sod-pot pump
4. nerves - need channels & pumps
Type of stimuli
1. Neurotransmitter effect determined by receptor NOT neurotransmitter itself. what happens is b/c of receptor.
2. Excitation (decrease in membrane potential)
a. Stimulus triggers the opening of additional sodium channels
b. Membrane potential to move toward zero = depolarization
a. Stimulus triggers the opening of additional potassium channels
b. Increases the membrane potential = hyperpolarization (make difference greater)
Ex. Dopamine inhibits shaking (Parkinsons don't have dopamine so muscle quivers)
a. Sodium gates open
a. Sodium gates close
b. Potassium gates open
3. Refractory period
a. Absolute refractory period
b. Relative refractory period
Synaptic structure (3)
1. Synaptic knob (change from electrical to chemical - potassium, sodium and calcium all electrical)
a. Neurotransmitter vesicles
2. Synaptic cleft
3. Postsynaptic membrane
a. Neurotransmitter receptors
Synaptic transmission (8)
1. Action potential reaches a synaptic knob
2. Calcium channels open in membrane of synaptic knob
3. Calcium ions to diffuse into synaptic knob
4. Calcium triggers exocytosis of neurotransmitter
5. Neurotransmitter diffuses across synaptic cleft
6. Neurotransmitter binds to receptors
7. Sodium channels open in postsynaptic membrane
8. Neurotransmitter deactivated
Synaptic tranmission misc
1. next cell could be cell, muscle, gland
2. have to get neurotransmitter back in:
a. enzyme w/acetylcholine
b. reabsorption. calcium pump (ATP) gets calcium back in
Indirect receptor effect
1. neurotransmitter doesn't enter cell
2. 2nd messenger open gates (cAMP)
3. nervous system & endocrine use the 2nd messenger system
synaptic potentials EPSP (3)
1. Excitatory postsynaptic potential
2. Depolarizes membrane of postsynaptic neuron
3. Action potential of postsynaptic neuron becomes more likely
synaptic potentials IPSP (3)
1. Inhibitory postsynaptic potential
2. Hyperpolarizes membrane of postsynaptic neuron
3. Action potential of postsynaptic neuron becomes less likely
1. movement (wave) of depolarization, moves down axon to synaptic knob
2. depolarize in sections, has to go in one direction
1. jumps from one node to another
2. ion channels open only at nodes of ranvier - jump form node to node
neurotransmitters - definition (2)
1. Chemical messengers that traverse the synaptic gaps between neurons
2. When released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron or cell
Neurotransmitters - types (6)
1. Acetylcholine (ACh)
Neurotransmitters - Acetylcholine
1. Links motor neurons and muscles (contract or relax)
2. Also involved in memory, learning, sleep, dreaming
3. Decreased in Alzheimer's (keep ACh around longer - target this ability)
Neurotransmitters - Dopamine
1. Specialty of neurons in brain regions dealing with emotions.
2. Decreased in Parkinson's
3. Increased in schizophrenia
Neurotransmitters - Serotonin
1. Neurons that govern sleeping, sensory perception, temperature regulation, and emotional states.
2. Found in GI system
3. Decreased in depression
Neurotransmitters - Norepinephrine
1. Apparently affects brain regions concerned with emotions, dreaming, and awaking.
2. Decreased amount can depress mood
Neurotransmitters - GABA
1. Most common inhibitory signal in the brain
2. Decreased amounts can cause seizures, tremors, insomnia
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