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Animal Physiology S1
semester one of comparative animal physiology
| Term | Definition |
|---|---|
| nervous systems | the body's interface- links sensory stimuli to behavior and actions via electrical impulses |
| cephalization | the concentration of sensory structures and nerves into one area (head) |
| central nervous system components | brain, spinal cord |
| peripheral nervous system components | cranial nerves, spinal nerves, ganglia outside the CNS |
| passive membrane of neuron | dendrites and cell body- no voltage channels |
| active membrane of neuron | axon hillock and axon- voltage ion channels |
| schwann cells | form myelin sheath, help electrical impulse conduction and regrowth of neurons after damage |
| nodes of ranvier | gaps in between schwann cells on the neuron |
| cells in the nervous system | neurons and glial cells |
| neurons | electrical potentials, characterized by irritability and conductivity, cell membrane is electrically unstable |
| glial cells | "glue," supports neurons (provide nutrients, remove waste, maintain ionic environment), no electrical impulses |
| neuron functions | sensory (afferent- coming in) motor (efferent- going out) interneurons (between) |
| electrochemical equililibrium | charges on both sides of membrane are equal- ions on each side repel each other to maintain equilibrium |
| concentration gradient | when a solute is more concentrated in one area than other (solved via diffusion) |
| nernst equation | used to calculate the equilibrium potential |
| resting potential | Vrest, plasma membrane is impermeable to ions but ions can still be moved via active transport and can move on their electrochemical gradients, normal voltage -70mV |
| ICF | intracellular fluid- high concentration of potassium K+ ions (pulls towards +62mV) |
| ECF | extracellular fluid- high concentration of sodium Na+ ions (pulls towards -90mV) |
| Na+/K+ ATPase | pumps Na+ out of cell and K+ into cell (active transport), 3Na+ for 2K+ |
| membrane potential | Vm, difference between voltage of ICF and ECF |
| electrical impulses in neurons | changes in a neuron's Vrest caused by gated ion channels |
| graded potentials | electrical impulse is proportional to stimulus occurs in passive membrane large, relatively long space constant transmit signals short distances decrease in amplitude with distance b/c cytoplasm/cell membrane are poor conductors ion channels |
| action potentials | electrical impulse is all or nothing always has same amplitude propagate along axon triggered by voltage transmits signals long distances |
| action potential steps | 0) membrane at resting potential Vrest 1) signal causes electrical impulse 2) membrane potential swings rapidly positive 3) membrane potential swings rapidly negative 4) refractory period 5) membrane at resting potential Vrest |
| depolarization | Vm approaches equilibrium potential for Na+ caused by opening of voltage-gated Na+ channels activated by graded potential of sufficient size "getting up as soon as your alarm goes off" |
| repolarization | Vm approaches equilibrium potential for K+ caused by opening of voltage-gated K+ channels K+ diffuses out of cell opened by delayed graded potentials "hitting snooze on your alarm" |
| K+ enters ICF | Vm LOWERS IN VOLTAGE -90v |
| Na+ enters ICF | Vm RISES IN VOLTAGE +60v |
| normal Vm | -70v (polarized) |
| maximizing conduction speed | 1) large diameter axons 2) myelination |
| large diameter axons | bigger axon diameter > less internal resistance > greater space constant > current from action potential spreads further > next action potential triggered further down axon |
| myelination | myelin provides insulation = no ion movement except at nodes of ranvier > circuits of local current flow depolarize next node at further distance than uninsulated axon less ion movements overall SALTATORY CONDUCTION |
| space constant | measurement of the decrease in amplitude of graded potential as it travels through axon = how well a signal will travel through axon |
| synapses | connections between presynaptic and postsynaptic neuron |
| electrical synapse | direct connection via gap junctions- adjacent cells are connected through protein channels at cytoplasm- molecules/ion/electrical signals can pass through rapid and reliable |
| chemical synapse 1 | transmit signals via neurotransmitters in synaptic cleft 1) AP depolarizes axon terminal 2) voltage-gated Ca2+ channels open, calcium enters cell 3) calcium entry triggers exocytosis of synaptic vesicle contents |
| chemical synapse 2 | 4) neurotransmitters diffuse across synaptic cleft and bind with receptors on postsynaptic cell 5) neurotransmitter binding initiates response in postsynaptic cell *a ligand for a ligand-gated ion channel = a graded potential |
| exocytosis | cell transports molecules out of the cell |
| excitatory post-synaptic potentials (EPSPs) | postsynaptic potential that makes PostS neuron more likely to fire AP mediated by Na+ or Ca2+ channels causes graded potential in PS neuron b/c influx of ions cell is depolarized (influx of positive ions) Vm approaches threshold for AP (more positive) |
| inhibitory post-synaptic potentials (IPSPs) | postsynaptic potential that makes PostS neuron less likely to fire AP mediated by K+ or Cl- channels causes graded potential in PS neuron b/c movement of ions cell is hyperpolarized Vm moves away from threshold for AP (more negative) |
| neurotransmitter receptors | each neurotransmitter can have 10+ receptors all do different things- allow for specialization |
| inactivation of neurotransmitters | some taken up by blood, others into glial cells enzyme acetylcholine-esterase breaks down some neurotransmitters |
| temporal summation | graded potentials sum in time if APs occur frequently enough in the PreS cell, graded potentials in the PostS cell overlap accumulation of rapidly occurring stimuli @ a single synapse leads to depolarization/brings initial segment to threshold |
| spatial summation | graded potentials sum in space a single neuron receives several synapses from many PreS neurons in different parts of dendrites if all of these elicit EPSPs they can sum together as they propagate |
| habituation | process by which nervous systems learn what NOT to do occurs @ synapses, decreases vesicle release from PreS neuron e.g. desensitizing horses to noise, touch, etc. |
| classification of receptors | 1) modality 2) role 3) structure |
| modality of receptors | what it will respond to- light, sound, touch, taste, smell |
| role of receptors | 1) exteroreceptors- monitor external environment (vision/touch/smell/hearing) 2) interoreceptors- monitor internal environment (pressure, stretch of blood vessels) 3) proprioreceptors- send info about movement and position of limbs/body parts |
| adaptation | when a stimulus is maintained, many receptors slow down the rate of APs (sensory cell no longer sends information) |
| phasic adaptation | quickly- e.g. touch, pressure briefly @ onset/offset of stimulus |
| tonic adaptation | slowly- e.g. pain, position constant/ongoing |
| general senses | simple receptors 1) somatic sensations (skin) 2) visceral sensations (organs) |
| special senses | 1) taste 2) equilibrium 3) smell 4) vision 5) hearing |
| sensory transduction | stretching dendrites open ion channels = a receptor potential (graded) = triggers APs in muscle receptor organs (MRO) stimulus energy stretches dendrites more stretch=more ion channels open=change in Vm |
| vision accommodation | adjustment of lens shape to change focus -far objects: relaxed ciliary muscle, taut suspensory ligaments, flat/weakly refractive lens -near objects: contracted ciliary muscle, slack suspensory ligaments, spherical/refractive lens |
| photoreceptors | 1) rods: one type, more sensitive, low-light vision, rhodopsin 2) cones: 3 types, color vision, sensitive to short- (B), medium- (G) and long-wavelengths (R) |
| visual pigments | retinal (vitamin A derivative) and opsin (protein) rhodopsin- embedded in membranous discs, G-protein coupled receptor (GPCR) |
| phototransduction | absorption of light shifts rhodopsin to trans isomer (changes shape of rhodopsin molecule)> activates transduction cascade> Na+ channels close> photoreceptor hyperpolarizes> glutamate stops releasing |
| horizonal cells | connect neighboring locations in retina |
| amacrine cells | further tune responses e.g. selectivity for movement |
| bipolar cells | can have different glutamate receptors- different kinds cause excitement (depolarized) or inhibition (hyperpolarized) in the light= on and off channels (created by bipolar cells) |
Created by:
ssumnerr
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