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Phys. Unit 4
| Question | Answer |
|---|---|
| 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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