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Phys. Unit 4

Central nervous system components spinal cord and brain
What nervous system is divided into central and peripheral systems
peripheral nervous system components afferent and efferent
How much of the blood is in the brain/ 15-20% of total blood supply
Weight of brain and percent of total body weight 1.5 kg and about 2% of weight of 70 kg man
What secretes cerebrospinal fluid? choroid plexuses
What is the blood-brain barrier? A tissue complex made by the ependyma neuroglia and controls rates of entry and types of substances allowed in
Direction of afferent NS? Sensory organs to CNS
Direction of efferent NS? CNS to Motor organs
Myelination description Schwann cells secrete mylin (fat) sheath around axon that insulates the axon and increases velocity of transmission of impulses; have Nodes of Ranvier
Two types of NS cells Neurons and neuroglia
What is basic communication unit of NS? Neuron
Part of neuron that receives stimulus Dendrites
What synthesizes proteins and neurotransmitters? Cell body
Where is the action potential initiated? In the cell body in the initial segment, or Hillock Area
Most common type of neuron interneurons (200,000)
Least common type of neuron afferent (1.0)
Afferent neuron size long dendrites, short axons
Efferent neuron size short dendrites, long axons
Interneurons size short dendrites, and either long or short axons
Number of neurons and neuroglia neurons- 10% neuroglia- 90%
Size of neurons and neuroglia neuroglia are smaller, neurons are larger volume is occupied in 50/50 neurons/neuroglia
Somatic Division definition only skeletal muscles (voluntary) activities; fast transmission; always excitatory; uses ACH
Transmission at synapse most chemical (neurotransmitter), a few electrical
Synapses definition 1. can be excitatory(facilitatory) or inhibitory 2. inputs (divergent and convergent)
How many synapses does a spinal neuron have? 15 x 10^3
How many synapses does a cranial neuron have? 100 x 10^3
Autonomic Division definition involuntary activities; parasympathetics and parasympathetics; innervates smooth, cardiac muscles; uses 2 neurons and ganglion; uses ACH and norepinephrine
What division is the major controller of homeostasis? autonomic division
What is the name for adrenal secretions? neurohormones
Adrenal Medulla secretions? 20%- norepinephrine 80%- epinephrine
Sympathetic division secretions? 20%- epinephrine 80%- norepinephrine
Cholinergic receptors 1. Nicotinic: respond to nicotine; found on other neurons and skeletal muscle 2. muscarinic- respond to mushroom toxin; found on smooth and cardiac muscle, as well as glands
What binds cholinergic receptors? ACH
Adrenergic receptors 1. Alpha- excitatory or stimulatory 2. Beta- inhibitory
What binds to adrenergic receptors? epinephrine or norepinephrine(does not bind to beta receptors)
Exceptions to receptors Cardiac muscle-norepinephrine binds to beta receptors (excitatory response) **(NE is not supposed to bind to beta receptors and not excitatory)
Resting membrane potential (Vm) -70 mV
Depolarization definition 1. Apply excitatory stimulus 2. Na channels open and K channels close 3. Na influx and cell becomes more positive (30-40 mV)
Repolarization definition 1. K channels open, Na channels closed 2. K efflux and cell becomes more negative (-80 mV)
Hyperpolarization definition 1. Apply an inhibitory stimulus 2. K channels open, Na channels close 3. K effux, cell becomes more negative than resting potential (Vm)
Threshold value -55 mV
Equilibrium potential values 1. K+: -90 mV (more inside cell) 2. Na+: +60 mV (more outside cell) 3. Cl-: -70 mV (do not contribute to membrane signals)
Types of potentials graded and action
Graded potential 1. created by subthreshold stimulus 2. amplitude/size depends on strength of stimulus 3. transmitted decrementally 4. useful in local or short distances 5. can be summed up to make an action potential
Action potential 1. characteristic of excitable membranes-neurons, muscles, glands 2. caused by rapid changes using voltage-sensitive ion channels
Threshold voltage value +15 mV
Magnitude or size of AP determined by what? independent of stimulus strength, but determined by number of Action Potentials fired/unit of time
Refractory periods 1. Absolute: during all of the depolarization and part of repolarization phase 2. Relative: during late part of the repolarization; can restimulate with supra-threshold stimulus only)
Where is summation of a signal done on a neuron? Hillock area because it has the lowest threshold value
Created by: kcapland



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