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63 Cards in this Set

  • Front
  • Back
Synapses
-specialized in structure and physiology
-in most cases, communication is one-way
Two methods by which cell can communicate with other:
Electrical and Chemical
Two possibilities of responses:
Excitatory and Inhibitory
Electrical Synapses:
-formed by gap junctions
-no delay
-only limit is size
Electrical Synapse functions:
-fast transmission/communication
-allows for synchronization of activity of all cells
-allow for stereotyped responses--always exactly same response
-almost all electrical synapses are excitatory
Characteristics of chemical synapses:
-most common type
-response of post synaptic cells is determined by what ion channel is open
-excitatory responses are anytime the ion movement takes membrane potential towards or above threshold
-inhibitory response is any synapse where ion movement prevents or takes membrane potential below threshold
Steps of chemical synaptic transmission Part 1 (3 parts)
Pre-synaptic events:
1. Action potential arrives at terminal and causes depolarization.
2. Depolarization causes voltage-gated calcium channels to open
3. Calcium enters terminal and causes synaptic vesicles to fuse with membrane
4. Neurotransmitter released into cleft
*above steps take .5 milliseconds
Steps of chemical synaptic transmission Part 2 (3 parts)
In The Cleft:
1. Neurotransmitter will diffuse to post synaptic cell (1 usec)
2. Neurotransmitter removed (2-5 usec)by:
a. Enzymatic breakdown
b. re-uptake into presynaptic neuron or other nearby cells
c. diffuses away
Steps of chemical synaptic transmission Part 3 (3 parts)
Post synaptic events:
1. Neurotransmitter will bind to membrane receptor
2. Causes receptor to change shape and open selective ion channel
3. Ions move through channel and change membrane potential
4. Channels close as neurotransmitter unbinds and is removed
*above steps take 1 usec
Acetylcholine (ACh)
-on skeletal--excitatory
-on cardiac--inhibitory
(two different responses because receptor is different)
Acetylcholine (ACh)
-released by motor neurons onto skeletal muscles
-also used by autonomica nervous system
-by brain stem
-diencephalon (thalamus & hypothalamus)
-cerebral cortex
-removed by enzymatic breakdown (acetylcholinesterase)
Seratonin (5-HT)
-found in brain stem
-send axons into diencephalon
-appear to be active in mood control and sensory perception
-inactivated by re-uptake
Dopamine (DA)
-located in thalamus, hypothalamus and spinal cord
-involved in emotional responses
-control of complex movements
-subconscious muscle movements
-inactivated by reuptake
-two diseases: Parkinson's and schizophrenia
Norepinephrine (NE)
-in brain stem and autonomic nervous system
-neurons that release are involved in arousal, dreaming, mood regulation
-inactivated by re-uptake
Gamma-aminobutyric acid (GABA)
-in amino acid, but not found in proteins
-always cause inhibition
-30% in cerebral cortex use this
-found in thalamus and hypothalamus
-inactivated by re-uptake
-Huntington disease
Substance P
-used by sensory neurons which signal pain into spinal cord
-inactivated by re-uptake
Enkephalin
-in thalamus and hypothalamus, limbic system and spinal cord
-natural opiate--inhibit pain perception
-removed by reuptake
Synaptic responses
-graded potentials
-excitatory post synaptic potentials (EPSP)
Na+
Na+ and K+ -->very quickly
-inhibitory post synaptic potentials (IPSP)
-ion channel that needs to be open: K+ and Cl-, can get spatial and temporal summation--happening at same time
Responses:
-sometimes not at threshold, nothing happens
-reach threshold, get one action potential
-reach and stay above--will get more than one action potential
Pre synaptic facilitation:
-responses keep getting bigger and bigger
-more channels open
-releasing more neurotransmitter
-pre synpatic cell forces it to make change
Neuromodulator:
Classical synaptic transmission and neuromodulation
-causes effects to last longer period of time
-can decreased membrane permeability
-can change threshold of cell
-activate "special electrical properties"
Brain stem:
-pathway between higher brain centers and lower brain centers and spinal cord
-many pathways cross over to opposite side of nervous system
-motor nuclei for cranial nerves
-control internal organs and involuntary functions
-where autonomic activity is started
-control of eye movements
-reticular formation located here:
1. involved in arousal and sleep
2. involved in coordination of breathing
3. involved in modulating pain
Cerebellum:
-regulates muscle tone-small amount of contraction of muscles
-helps maintain posture and balance
-involved in coordinating and planning skilled voluntary movements
Hypothalamus:
-regulates many homeostatic functions: body temp, thirst, urine output, food intake
-important link between nervous system and endocrine system
-helps maintain waking and sleeping states
-functions as oscillator that drives many biological rhythms
-emotional responses
Thalamus:
-relay station for all sensory inputs except smell to cerebral cortex
-relay station for motor commands from cerebral cortex down to spinal cord
-contributes to emotions and memory
Basal Nuclei:
-coordinating voluntary movements
-inhibits muscle tone
-suppresses useless patterns of movement
1. amygdala-emotions and memory
2. hippocampus-learning and memory
Cerebral Cortex:
Six layers:
1-3: connections between different parts of cortex
4: sensory inputs from thalamus
5: outputs to spinal cord
6: outputs to thalamus
Functions of cerebral cortex:
-voluntary control of movement
-sensory perception
-language
-personality traits
-sophisticated mental events, ex: creativity, memory
Frontal lobe:
1. voluntary motor control
2. location of personality
3. responsible for higher intellectual responses
4. location of verbal communication
Parietal lobe:
1. sensory perception of both skin and muscle sensations
2. understanding of speech and being able to formulate words to express thoughts and emotions
3. ability to interpret textures and shapes
Temporal lobes:
1. interpretation of auditory inputs
2. storage of memory of auditory and visual experiences
Occipital lobe:
1. perception of vision
2. integrates eye movements
3. correlates visual images with previous visual experiences and other sensory inputs
Insula:
1. perception of visceral sensations (ex: stomach ache)
2. plays role in memory
Corpus callosum:
-main connection between two hemispheres
left hemi-reading and producing language
right hemi-can interpret verbal language, but not generate speech, depth perception drawing
Sensory receptors:
transducers will convert sensory stimulus into a neural signal
Five types of sensory receptors:
1. mechanoreceptor: touch, respond to physial change in shape or position
2. chemoreceptor: smell and taste
3. photoreceptor: vision
4. nociceptor: pain
5. thermoreceptor: temperature
sensory modality:
will only detect that certain type of stimulus
Receptive field:
-region or place where sensory stimulation large enough that would cause a response in only one sensory neuron
-send info to brain in very ordered way
labeled lines:
sensory maps, pathways
Receptor potentials:
-caused when sensory stimulation of sensory cell stimulation reception comes
-summation-temporal and spatial
-decremental conductance-get smaller as they go
-size is graded, more light, more seen
Receptor adaptation:
-decrease in sensory cell response to continued stimulation
Phasic receptors:
exhibit adaptation, ex: touch, smell--perfume
Tonic receptors:
will continue to respond, ex: nociceptors
Somatosensory cortex:
part of parietal obe where you get sensations of skin and muscle
Somatosensory homunculus:
the sensory map, ex: lips have more area than knee, so you can sense things coming into mouth
Peripheral nervous system
Autonomic nervous system
-sympathetic
-parasympathetic
Neurotransmitters
-both preganglionic neurons release ACh
-different receptors (on postganglionic)
Nicotinic receptors:
nicotine will activate, open ion channels that let both Na+ and K+ through-depolarization
Muscarinic receptors:
-agonist, will change target cell-use G-protein
-in different targets, open ion channels with only K+ through--cell will hyperpolarize, inhibit that cell
-cause depolarization, but by closing a K+ channel or open a calcium channel
Norepinephrine:
-all work through G-protein
-sometimes will effect ion channels
-some will work through cAMP
Functions of autonomic nervous system:
involved in controlling involuntary targets, cardiac, smooth muscle and glands
Functions of sympathetic nervous system:
-active when body needs to adapt or cope with stresses-physiological and psychological
-produces wide effects, cannot pick and choose
Functions of parasympathetic nervous system:
-day to day stuff, negetative functions
-produces discrete response in one organ and leaves others alone
Neuromuscular junction:
-where motor neurons synapse onto skeletal muscle cell
-receptor in muscle cell is nicotinic receptor, both Na+ and K+ through channel will ALWAYS depolarize to threshold
Actin:
-main protein, two rows of actin molecules
-"strand of pearls" then twisted into helix
Myosin binding site:
where actin binds to myosin
Thick myofilaments
-made up of myosin
-actin binding site of myosin binds to myosin binding site
ATP binding site:
enzyme ATPase
Sarcoplasmic reticulum (SR)
-contains calcium ions, when stimulated it will release them
T-tubules:
part of plasma membrane, goes down deep into cell, carry stimulation down into cell
Contraction: stimulation/excitation steps:
1. action potential travels down motor neuron axon
2. ACh is released at the neuromuscular junction
3. ACh activates receptors that open ion channels that let both Na+ and K+ through
4. muscle membrane potential depolarized to threshold
5. muscle cell will produce action potential which will spread across the muscle cell membrane
6. action potential will travel down T-tubule into cell
7. Action potential will activate the SR
Excitation-coupling steps:
1. Once it's activated, the SR releases calcium ions
2. Calcium ions bind to troponin
3. Troponin and tropomyosin move out of the way and expose myosin binding sites of actin
Contraction steps:
1. Myosin cross bridge binds to actin
2. Myosin cross bridge will bend over in power stroke, pulling the myofilament towards the center of sarcomere and ADP and Pi are released
3. brand new ATP has to bind to myosin cross bridge and then will let go of actin
4. ATP broken down into ADP and Pi and myosin uses energy to move back to starting position
5. process continues until calcium is transported back to SR.