Human Physiology - Exam 1

anatomy

parts of the body

physiology

functions of the parts of the body

homeostasis

maintaining a constant internal environment (body temperature, heart rate)

what is the basic fundamental functional unit of the human body and how does it relate to the other levels of organization?

the cell. cells make up tissues, organs, organ systems- without them, there would be no communication between parts of the body

microvilli

increases the surface area for absorption

cell membrane

phospholipid bilayer, acts as both a gateway and barrier between cytoplasm and ECF

cytosol

“intracellular fluid (ICF)”, suspends inclusions, fibers, and organelles

lysosomes

small storage vesicles containing powerful digestive enzymes

peroxisomes

contain enzymes that break down fatty acids and some foreign materials

golgi complex

receives proteins on the rough ER, modifies them, and packages them into the vesicles

mitocondrion

make ATP for the cell

nucleus

contains DNA, controlling all the cells processes

rough ER

main state of protein synthesis

smooth ER

main site of synthesis of fatty acids, steroids, and lipids

ribosomes

small, dense granules of RNA, and protein that manufacture proteins

microtubules

movement of cilia, flagella, and chromosomes; intracellular transport of organelles; largest cytoskeleton fiber

microfilaments

form a network just inside the cell, associates with myosin for muscle contraction

describe the structure and function of the plasma membrane

phospholipid bilayer with proteins that act as structural anchors, transporters, enzymes, or signal receptors - acts as a gateway and a barrier between cytoplasm and ECF

gated ion channel

gate is usually closed, allowing for regulation of what ions move through. when opened, ions move through normally (Na+, Ca+, Ca++)

non-gated ion channels

always open, “leakage channel” (Cl-, K+), pores may or may not be selective

carrier (transport) proteins

moves molecules across membranes, ATP dependent (Na+, -K+ exchange protein), ATP dependent (neurotransmitter), maintain homeostasis of the cell

receptor-type protein

bind to ligands, causes cells to respond (insulin, antigen, glucose, neurotransmitters)

enzymes

catalyze intracellular or extracellular reactions (peptides) - mostly in intestines, speeds up reactions

anchoring proteins

attach to cell membrane to the cytoskeleton, attach cell membrane to other membranes; intercalated discs

describe the ways that a molecule can passively diffuse across a cell membrane

passive diffusion is when molecules move across a cell without the use of energy, simple diffusion if they’re small/nonpolar molecules (O2, CO2), facilitated diffusion using channel proteins, carrier proteins to let the large/polar molecules through, ion channels by allowing ions to move across their electrochemical gradient, water channels (aquaporins) to allow water molecules, and the concentration gradient when molecules move from high to low concentrations.

what is the difference between simple diffusion and facilitated diffusion?

the type of molecules they transport and involvement of transport molecules. simple diffusion is for small/nonpolar molecules that directly pass through the lipid bilayer (oxygen), while facilitated is for large/polar molecules and ions that need assistance of specific transport proteins (glucose- big, polar, hydrophilic molecule that needs a specialized protein to diffuse)

exocytosis

removes material in the vesicle from the cell

endocytosis

takes materials in the vesicle into the cell

how are exocytosis and endocytosis

they both form vesicles

primary active transport

used to transport molecules against the concentration gradient using ATP (Na+, Ka+, ATPase pump)

secondary active transport

uses potential energy of the concentration gradient for one solute to move another against the concentration gradient in the same direction (Na+, glucose)

how are primary active transport and secondary active transport different from passive diffusion

primary and secondary active transport require energy to move molecules across their concentration gradient, while diffusion is a passive process that moves molecules down the concentration gradient

compare characteristics of a symporter and antiporter

symporters move molecules/ions in the same direction (Na+/glucose), while antiporters move them in opposite directions - one solute move in while another moves out (Na+, Ca+)

osmolarity

the total molar concentration of all solution (solutes) particles (ICF=300 mOsom, .3 Osm)

osmosis

diffusion of water through a semi-permeable membrane from low to high concentration of non-penetrating particles

tonicity

property of a solution that prevents or promotes osmosis across a semi-permeable membrane, refers to the ECF soulte concentration relative to ICF solute concentration

define what osmotic pressure and hydrostatic pressure are with relation to how these forces act on a cell

osmotic pressure relates to the movement of water across a semi-permeable membrane due to differences in solute concentration, while hydrostatic pressure relates to the pressure exerted by a fluid on a cell. osmotic pressure exserts pressure on the cell membrane moving through it, and hydrostatic pressure can be used for blood pressure

characterize any solution in terms of osmolarity and tonicity

find its osmolarity (see if solutes are non-penetrating), if osmosis will occur (hypo/hyper-tonic)

describe the concentration of Na+, K+, and Cl- ions across the cell membrane

in the ECF Na+ and Cl- have a very high concentration while K+ is very low, but in the ICF K+ has a very high concentration while Na+ and Cl- do not. Na+ and Cl- have a low relative membrane permeability due to their limited presence of channels, K+ as a high relative membrane due to many potassium leak channels in the cell membrane

ECF=ICF

iso-osmotic

ECF<ICF

hypo-osmotic

ECF>ICF

hyper-osmotic

what transport system enables cells to maintain a resting membrane potential

sodium potassium pumps

describe how both the electrical and chemical concentration gradients govern the movement of potassium and sodium ions across the membrane

electrical gradients influence ion movements because of the attraction of opposite charges and repulsions of like charges

equilibrium potential

when the chemical gradient equals the electrical gradient and are opposite in direction. you need the potential energy for the chemical gradient and the potential energy of the electrical charge separation to calculate

the Nernst equation

predicts the electrical potential created by the unequal distribution of a single ion type across a semi-permeable membrane, however, it only accounts for the equilibrium potential of a single ion and doesn’t account for different permeabilities of different ions

the Goldman-Hodgkin-Katz equilibrium equation

developed to address the shortcomings of the Nernst equation- it predicts membrane potential for the entire cell

depolarization

more positive membrane potential

hyperpolarization

more negative membrane potential

repolarization

returning to the resting membrane potential

what process enables a graded membrane potential to spread from the area that it is first generated

ion channels

temporal summation

accumulation of graded potentials over time from a single presynaptic neuron

spatial summation

combines graded potentials from multiple presynaptic neurons or synapses simultaneously

how can temporal and spatial summation of graded membrane potentials determine the output of a post-synaptic neuron

the combined effects of temporal and spatial summation determine whether the postsynaptic neuron fires an action potential. if the sum of excitatory inputs surpasses the threshold, it fires - if inhibitory inputs dominate or if the depolarization doesn’t reach the threshold, the neuron doesn’t fire

chemically-gated sodium channels

activated when a specific neurotransmitter/ligand binds to them

voltage-gated sodium channels

activated/opened when the membrane potential hits a certain voltage

graded membrane potentials

variable- occur in response to stimuli and only travel short distances within neurons and they summate

action potentials

all-or-none response that travels long-distance communication along axons - do not summate

describe how energy, which is stored as the membrane potential, is used by excitable cells to transmit a signal over a long distance

if a stimulus is strong enough to bring the membrane potential closer to the threshold, it can trigger the opening of voltage-gated sodium channels, allowing rapid flow of Na into the cell, causing depolarization, which is the initiating of an action potential

describe the changes in the transmembrane potential and the ionic permeability changes for Na and K that occur during an action potential

the transmembrane potential starts at the resting potential, undergoes depolarization die to the rapid influx of Na ions, peaks at a positive value, then repolarizes from K ions flowing out of the cell to bring the transmembrane potential back to its negative value

describe the effects of local currents on the opening of voltage-gated sodium channels

a depolarizing stimulus, such as a neurotransmitter binding to a receptor, causes a local region in the cell to depolarize, when the membrane potential reaches a certain voltage, Na channels open, allowing them to flow in from a high concentration (ECF) to a low concentration (ICF) down their electrochemical gradient, generating a small local current. the local current continues to flow, rapidly depolarizing adjacent membrane regions, opening more voltage-gated sodium channels

what are the possible configurations voltage-gated Na channels can be in during specific periods of the action potential

in resting state, they are closed. in activation state, the membrane depolarizes, opening the voltage-gated sodium channels, shortly after the activation gate opens, the inactivation gate starts to close, preventing the flow of Na ions, which prevents continuous depolarization

describe the electrical fate of an action potential once it arrives at the axon terminal (presynaptic knob)

it triggers Ca ion influx and neurotransmitter release, allowing for the transmission of information from one neuron to another/from another neuron to an effector cell. the post-synaptic response is determined by the type of neurotransmitter and the receptors which can either excite/inhibit the downstream neuron or effector

absolute refractory period

complete unresponsiveness immediately following an action potential due to the inactivation of Na channels

relative refractory period

period during which the cell can respond to stronger stimuli, but the threshold for excitation is elevated because the membrane potential is still hyperpolarized

what are the events that cause the propagation of an action potential

local currents created by the influx of ions depolarize the membrane (and adjacent regions) allowing the action potential to properly propagate along the axon

saltatory action potential propagation

myelinated axons and nodes of Ranvier allowing for faster and more energy-efficient transmission

continuous action potential propagation

they are slower because their axons are not myelinated

describe the distribution of ion channels in myelinated axons.. is it different from unmyelinated axons?

myelinated axons have a high concentration of ion channels at nodes of Ranvier, allowing for saltatory conduction, and are energy-efficient because of ion pumps - unmyelinated axons do not have these

what determines the rate of action potential propagation in non-myelinated axons

axon diameter, membrane properties (higher resistance=faster), ion channel density, and electrochemical properties of the axon

type a nerve fiber

largest diameter, myelinated, 140 m/s, its a motor neuron, sensory neurons mediating postion, balance, delicate touch, and pressure sensation

type b nerve fiber

second smallest diameter, myelinated, conduction speeds up to 18 m/s, mixture of sensory afferent neurons and peripheral effectors (cardiac, smooth muscle, etc.)

type c nerve fiber

smallest diameter, non-myelinated, 1m/s, sensory afferent fibers

what’s the pathology of multiple sclerosis and the underlying cause of this disease

it’s a demyelination disease and the destruction of myelin sheath allows the local internodal current leak through the membrane, resulting in action potential failure.

what’s a synapse and what does it have to do with presynaptic and postsynaptic elements

the space between the pre/post synapse. the pre-synapse refers to the neuron/cell its transmitting the signal at the synapse and the postsynaptic element is what is recieving the signal

electrical synapses

continuous and allow action potentials to propagate directly into the post-synaptic cell

chemical synapses

not physically coupled- they transmit the signal from pre to postsynaptic cells, bind to receptors on the postsynaptic cell, causing graded membrane potentials to generate, and they are used more in the body

what are the major steps leading to neurotransmitter release from the presynaptic terminal

its initiated by the arrival of an action potential, involving Ca dependent fusion of the synaptic vesicles with presynaptic membrane, then neurotransmitters release, binding to postsynaptic receptors leading to a response and signal across the synapse

list several neurotransmitters and a possible use for each one

acetylcholine - excitatory, causes excitatory post-synaptic potential

glycine, GABA, histamine - inhibitory, causes inhibitory postsynaptic potential

describe the different ion fluxes that can either create an IPSP or an EPSP in postsynaptic membranes

EPSP is caused by increased Na permeability, RMP becomes more positive (Na+ flows in), while IPSP is caused by an increased K and Cl permeability, RMP becomes more negative (K+ flows out, Cl- flows in)

reuptake

a way to eliminate neurotransmitters from the synaptic cleft - they are actively transported back to the presynaptic neuron (ex. zoloft blocks the reuptake of serotonin)

what is a way to eliminate a neurotransmitter from the synaptic cleft

destroying the transmitter- breaking down the neurotransmitters in the synaptic cleft by specific enzymes (ex. acetylcholinesterase to acetylcholine)

indicate how acetylcholine is recycled as a neurotransmitter by a cholinergic pre-synaptic terminal, what organelle is needed to allow this?

there is an uptake - acetylcholine gets transported back to the presynaptic neuron, mitochondria is needed to be present

ionotropic post-synaptic receptors

directly control ion flow through the receptor channel, resulting in rapid changes in the membrane potential (ex. glutamine receptors - excitatory)

metabotropic post-synaptic receptors

initiate intracellular signaling cascades through G protein, leading to slower and more diverse cellular responses (ex. dopamine receptors)

describe the phenomenon of long-term potentiation of glutaminergic synapse (LPT) and indicate the mechanism that underlies this phenomenon

an increase in synaptic efficacy due to the activation of NMDA receptors, Ca influx, and activation of protein kinases. Its believed to be a cellular mechanism underlying learning and memory processing- it strengthens glutamatergic synapses