Exam 2 Flashcards
what is the absolute refractory period?what is its function?
a segment of action potential that starts from the opening of activation gates and ends right before inactivation gates begin to open.
*cannot induce a second action potential during this time *insures action potential only travels in one direction
what is the voltages for neuron resting potential and action potential? what is the voltage threshold for action potential to be triggered?
resting potential = -70mV
action potential = +30mV
threshold = -55mV
what are the 9 steps of membrane potential?
1) resting membrane potential
2) depolarizing stimulus from graded potential
3) membrane depolarizes to threshold. voltage gated Na+ and K+ channels begin to open
4) rapid entry of Na+ depolarizes the cell
5) once at AP voltage, Na+ channels close and slower K+ continue to open
6) K+ moves from cell to ECF which repolarizes the cell
7) K+ channels remain open allowing K+ to continue to exit cell which hyperpolarizes it
8) K+ channels close allowing less K+ to leak from cell
9) cell returns to resting ion permeability and resting membrane potential.
what are the positions of Na+ activation and inactivation gates during the various voltages in membrane potential?
- At resting membrane potential (-70mV)- activation gate is closed, inactivation gate is open
- At or suprathreshold (-55mV +)- activation gate begins to open and inactivation gate is open
- depolarization (-55mV - +30mV) - activation and inactivation gates are both fully open
- At action potential voltage (+30mV) - activation gate remains open and inactivation gate is closed
- hyperpolarization(-80mV - -70mV) - activation gate begins to close and inactivation gate opens
describe the position of voltage gated potassium channels in the various phases of membrane potential
- resting membrane potential - gate closed
- depolarization - gates closed
- action potential voltage (+30mV) - gates are beginning to open
- repolarization - gate is opened
- hyperpolarization - closing but not yet fully closed
depolarization of action potential due to rapid entry of Na+ into the cell is an example of which type of feedback loop and why?
it is an example of a positive feedback loop. the rapid entry of sodium depolarizes the membrane potential and leads to the sodium activation gates opening more leading to more sodium entering and more polarization.
how is depolarization stopped during action potential?
sodium inactivation gates close
what is membrane potential relative refractory period and when does it end?
it begins when the sodium channel active and inactive gates begin to reset to resting positions while potassium channels remain open. when all channels are at resting state, the refractory period is over.
in which refractory period can a second action potential be produced?
if a STRONG stimulus is experienced during the relative refractory period a second action potential may be produced
what is saltatory conduction?
in myelinated axons, action potential is transmitted from node of ranvier to node of ranvier.this is how action potential is able to move so rapidly while maintaining a constant strength
how does saltatory conduction make it possible for action potential to maintain a constant strength?
a new action potential is created at each node of ranvier
where are voltage gated channels found on neuron axons?
at each node of ranvier
what is the purpose of myelin sheath on axons?
insulates axons to prevent voltage from escaping
how fast does action potential travel down a myelinated axon?
2 meters per second
how does action potential transmit the strength of graded potential?
a lower frequency of consecutive action potentials for lower strengths and a higher frequency of consecutive action potentials for higher strengths
what prevents action potential from occuring simultaneously or moving backwards?
the absolute refractory period
what is normokalemia and what affect does this have on membrane potential?
normokalemia = normal K+(potassium ion) concentration in the ECF. this is the optimal condition for membrane potential resting state and will not allow subthreshold graded potential to fire an action potential. further it will allow for the firing of action potential when a suprathreshold graded potential is received
what is hyperkalemia and what affect does this have on membrane potential?
hyperkalemia is a condition where there is a higher than normal concentration of k+ (potassium ions) in the ECF. the lower concentration gradient leads to less potassium ions diffusing out of cells and resulting in a higher positive ion concentration within the cell. this raises the membrane potential resting state to a more positive number that is closer to threshold. weak graded potentials that would normally be subthreshold can now result in the firing of action potential.
what is hypokalemia and what affect does this condition have on membrane potential?
hypokalemia is a condition where there is a lower than normal concentration of K+(potassium ions) in the ECF. this leads to a steeper concentration gradient on potassium and a lower concentration of positive potassium ions within the cell. this lowers (hyperpolarizes) the membrane potential resting state to a value that is more negative bringing it further from the threshold. graded potentials received at the trigger zone in the axon hillock that would normally be at or suprathreshold are now too weak to fire an action potential.
what is the synaptic cleft?what is the postsynaptic neuron?what is the presynaptic neuron?
1) synaptic cleft is the space between the axon terminal of the presynaptic neuron and the body or dendrite of the postsynaptic neuron (or effector cell). the location where neurotransmitters are sent and received
2) the postsynaptic neuron is the neuron in a synapse that is receiving stimuli
3) the presynaptic neuron is the neuron that is sending neurotransmitters to the postsynaptic neuron or effector cell
what are the 5 steps associated with neurotransmitter communication in a synapse?
1) action potential arrives at the axon terminal and depolarizes it.
2) the depolarization opens voltage gated Ca2+(calcium) channels allowing calcium to enter the cell
3) entry of calcium into the cell triggers exocytosis of neurotransmitter filled vesicles
4) neurotransmitters diffuse across the synaptic cleft and binds to receptors on the postsynaptic cell.
5) the binding of neurotransmitters initiates a response in the postsynaptic cell
what is acetylcholine and what is it able to bind to?
acetylcholine (ACh) is a neurotransmitter that is only able to bind to a classification of receptors called cholinergic receptors
what are the two types of cholinergic receptors?
nicotinic cholinergic receptors (nAChR)
muscarinic cholinergic receptors (M)
where are nicotinic cholinergic receptors found?
where are muscarinic cholinergic receptors found?
nicotinic cholinergic receptors are found are found on skeletal muscle cells(voluntary effectors), autonomic neurons(involuntary), and in the CNS
muscarinic cholinergic receptors are found on smooth and cardiac muscle cells(involuntary effectors), endocrine and exocrine glands(involuntary effectors), and in the CNS
what is epinephrine and norepinephrine, what do they bind to, and where are their receptors found?
they are neurotransmitters, they bind to alpha adrenergic or beta adrenergic receptors, and receptors are found in smooth and cardiac muscle, endocrine and exocrine glands, and the CNS
what is dopamine, what does it bind to, and where are its receptors found?
a neurotransmitter that binds to dopamine receptors and is found only in the CNS
what is serotonin, what does it bind to, and where are its receptors found?
a neurotransmitter that binds to serotonergic receptors that are found only in the CNS
what is histamine, what does it bind to, and where are its receptors found?
neurotransmitter that binds to histamine receptors that are found only in the CNS
how is dopamine, norepinephrine, and epinephrine produced?
1) it starts off with a single amino acid called tyrosine
2) tyrosine is converted into DOPA
3) DOPA is converted into dopamine
4) dopamine is converted into norepinephrine
5) norepinephrine is converted into epinephrine
how is serotonin produced?
the amino acid tryptophan can be converted into serotonin
what is neurotransmitter termination?describe the methods of termination.
neurotransmitter action terminates when neurotransmitters are broken down, taken up by cells, or diffuse away from the synapse. neurotransmitters can be:
1) either taken into glial cells or back into axon terminals through protein channels
2) broken down and inactivated by enzymes found on the postsynaptic cell
3) diffused out of the synaptic cleft either into the ecf or blood stream
how is acetylcholine produced?
- acetylcholine is broken down by the enzyme acetylcholinesterase
- acetate is transported into the post synaptic cell and choline enters the presynaptic axon terminal through an Na+ assisted symport carrier
- choline reacts with acetate from acetyl CoA (from pyruvate metabolism) via an enzyme and acetylcholine is produced.
- the CoA unit returns to the mitochondria and returns to pyruvate metabolism
what is the enzyme that breaks down acetylcholine called?
acetylcholinesterase
what is membrane potential?
electrical disequalibrium between ICF and ECF
what is membrane potential due to?
ion movement through leaky ion channels
what are the two types of membrane potentials we are discussing in class?
graded potential and action potential
what is resting membrane potential and what is it due to?
membrane potential has reached a steady state nd is not changing. this is mostly due to K+ (potassium ions)
what is the resting membrane potential for a neuron?
-70mv within the cell
what are the functional classifications of neurons?
1) sensory neurons
2) motor neurons
what are the structural classifications of neurons and where are they found?
1) unipolar neurons(somatic sensory)
2) bipolar neurons(special sensory- hearing, vision, smell,)
3) multipolar neurons(motor function (efferent and CNS)
what are the branches of axon right before axon terminals called?
collaterals
what are nuclei in the nervous system?
a grouping of neuron cell bodies within the CNS
what are ganglia?
a grouping of neuron cell bodies outside the CNS (in the PNS)
what is a tract in the nervous system?
a grouping of nerve fibers that interconnect regions of the CNS
what are nerves?
bundles of axons in the PNS
what is membrane potential depolarization?
membrane potential becomes more positive that resting membrane potential.(creates an electrical signal)
what is repolarization?
depolarized membrane potential returns to resting potential
what is hyperpolarization?
when membrane potential becomes more negative than its resting membrane potential
what chemicals do chemically gated protein channels in neurons respond to?
neurotransmitters, they bind to the receptor which opens the protein channel
what type of gated protein channel responds to membrane potential?
voltage-gated channel proteins
what are characteristics of graded potential?
1) they vary in strength
2) they travel only short distances and lose strength the further they travel
where is graded potential generated and how?
neuron cell bodies and dendrites that receive stimuli from action potentials in other cells and generate a graded potential that may go on to trigger action potential in its own cell
how and where is action potential generated in neurons?
it responds to at or suprathreshold graded potentials that are generated from action potentials originating from other cells. if the graded potential sensed by the axon hillock meets or exceeds a threshold, it generates action potential.
how much strength does action potential lose as it travels?
none, action potential maintains a constant strength
what happens if graded potential detected at the axon hillock does not meet or exceed action potential threshold?
nothing, the threshold must be met to generate action potential.
what is the transporter called that allowed choline to travel back into the neuron called and why?
sodium linked choline transporter because it is a symport transporter that requires sodium to drive the transportation of choline across the membrane
describe cholinergic nicotinic receptors
they are chemically gated antiport transport proteins that respond to acetylcholine and allow sodium to enter the cell and potassium to leave the cell which produces graded potential
describe how a muscarinic cholinergic receptor works
1) acetylcholine binds to the muscarinic cholinergic receptor
2) binding causes the stimulatory g-proteins to break off of the icf side of the receptor
3) the the beta and gamma proteins are stuck together but break away from the alpha protein and float further into the cytoplasm
4) the alpha protein travels along the cell membrane until it reaches a protein structure which triggers a series of chemical reactions that open a transport protein
what binds to adrenergic receptors?
norepinephrine
what is a g-protein?
it is the alpha beta and gamma protein when it is attached to one another and still attached to the receptor
what are the steps related to the adrenergic receptor process?
1) norepinephrine or epinephrine binds to the adrenergic receptor
2) the G-protein attached to the receptor is activated. alpha breaks away from beta and gamma proteins and travels along the plasma membrane until it reaches adenylate cyclase. beta and gamma proteins float off in the cytoplasm together
3) adenylate cyclase is activated and reacts with ATP molecules to form cAMP (second messenger)
4) cAMP activates protein kinase A
5) Protein kinase A phosphorylates a transport protein
6) the protein channel either opens or close to allow or prevent the movement of ions across the cell membrane which produces either an excitatory or inhibitory response
what does ICR stand for?
ion channel receptor
what does GPCR stand for?
G-protein coupled receptor
what are the two postsynaptic responses?
EPSP- excitatory postsynaptic potential
IPSP- Inhibitory postsynaptic response
describe EPSP what receptors produce only EPSP?
excitatory postsynaptic potential depolarizes the postsynaptic cell.nicotinic cholinergic receptors
describe IPSPwhat receptors are capable of producing IPSP?
inhibitory postsynaptic potential hyperpolarizes the cell to prevent graded potential from firing action potential.
muscarinic cholinergic receptors and adrenergic receptors
what happens when graded potential originating from different synapses in one cell body meet one another?
they join together. IPSP will join together to make a stronger graded potential.
if IPSP meets EPSP, the EPSP will reduce the strength of graded potential.
what does the nervous system start out looking like, what is it called?
looks like a tube it is called the neural tube
define rostral and caudal when it concerns the brain
rostral is the head end (anterior)caudal is the tail end or (posterior)
define rostral, caudal, ventral, and dorsal when it concerns the spinal cord
rostral is superior
caudal is inferior
dorsal is posterior
ventral is anterior
what are the three primary vesicles in a developing nervous system?
top = prosencephalon(forebrain) middle = mesencephalon(midbrain) bottom = rhombencephalon(hindbrain)
what does the prosencephalon develop into?
telencephalon (2 hemispheres) and the diencephalon (includes thalamus and hypothalamus)
what does the mesencephalon develop into?
the midbrain
what does the rhombencephalon develop into?
the metencephalon which further develops into the pons and cerebellum
and the myelencephalon which further develops into the medulla
what is the difference in what is contained in the white matter vs. grey matter?
white matter contains myelinated axons, grey matter contains cell bodies and dendrites
what type of information does the anterior (ventral) and posterior (dorsal) spinal nerves carry?
posterior (dorsal) nerves carry sensory information afferently to the CNSanterior (ventral) spinal nerves carry efferent motor signals to effectors
where do ascending and descending tracts in the spinal cord take information?
ascending tracts take information to the braindescending tracts carry commands to motor neurons
what is the function of white matter in the spinal cord?
it transmits information to and from the brain
what is a spinal reflex?
afferent signals bypass the brain and travel through the cell bodies of the grey matter and send signals directly to effectors( skeletal muscles) creating a very fast response
what type of information does the somatosensory tract carry? what are the pathways?
the somatosensory tracts carries information related to general senses to the primary somatosensory area of the cerebral cortex
POSTERIOR COLUMN-MEDIAL LEMNISCUS PATHWAY:
1) signal sent from receptor through the posterior spinal nerve
2) from posterior spinal nerve through posterior column of the spinal cord
3) from posterior column through the “olive” (nuclei of the medulla)
4) from the olive through the medial lemniscus of the midbrain
5) from the medial lemniscus through the thalamus
6) from the Thalamus to the post central gyrus (primary somatosensory area of cerebral cortex)
ANTEROLATERAL PATHWAY (SPINOTHALAMIC):
1) signal sent from receptor through the posterior spinal nerve
2) from the posterior spinal nerve through the anterior and lateral spinothalamic tract in the spinal cord
3) from the spinothalamic tracts through the medial lemniscus
4) from the medial lemniscus through the thalamus
5) from the thalamus to the post central gyrus (primary somatosensory area of cerebral cortex)
what is general sensory?
1) fine touch
2) proprioception
3) vibration
4) pain
5) cold and warmth
6) tickle
7) itch
what is proprioception?
perception of the position of your joints in relation to the space around you
1) what is the posterior column-medial lemniscus pathway of the somatosensory tract used for?2) what is the anterolateral pathway used for?
1) used to transmit information related to fine touch, proprioception, and vibration
2) used to transmit information related to pain, cold, warmth, tickle, and itch
what is the olive in the medulla?
the olive is the nuclei in the medulla it is a sensory relay station
what type of information does the corticospinal tract carry?what is its pathway?
carries motor information from the brain to the spinal cord to be transmitted to effectorsCORTICOSPINAL TRACT PATHWAY:
1) signals are carried from the precentral gyrus (primary motor area of the cerebral cortex) through the medulla pyramids
2) from the medulla pyramids through the left lateral and the right anterior corticospinal tracts
3) from the left lateral and right anterior corticospinal tracts to the anterior spinal nerve on the opposite side the signal was sent.
what are the pyramids of the medulla?
descending tracts that carry motor information
what is dessucation?
the crossing over of tracts to the other side of the nervous system. signals sent from the right side of the brain cross over to the left at the dessucation point which is in the medulla
what type of information passes through the medulla pyramids?
descending motor signals
what type of information passes through the olive (nuclei of the medulla)?
ascending sensory information
what is the function of the thalamus?
it is the main sensory relay station. all sensory signals except olfaction travel through the thalamus
where is the cardiovascular center in the nervous system and what is its function?
it is located in the medulla and its function is to control heart rate and contractility
what type of matter is located in the pyramids and olive of the medulla and the cardiovascular center?
grey matter
where is the respiratory center located and what are their functions?
there is one respiratory center located in the medulla and another in the pons. they work together to control frequency and strength of breathing
what is contained within the pons?what type of matter is the pons made up of?
1) motor tracts from cerebrum to cerebellum and medulla
2) sensory tracts to thalamus
3) respiratory center and tracts to respirator center in medulla
the pons is made up of lots of white matter
what is the official name for the midbrain?
the mesenchephalon
what part of the mesencephalon controls involuntary/reflexive eye movement?
the superior colliculi
where in the mesencephalon does auditory information integration take place?
the inferior colliculi
describe the communication between the superior and inferior colliculi in the mesencephalon
they work with one another so that reflexive eye movement controlled by the superior colliculi can be used when a loud noise is sensed by the inferior colliculi
are there tracts found in the mesencephalon? if so which types?
yes, both sensory and motor tracts
what is the thalamus composed of?
various nuclei (neuron cell bodies and dendrites
what is the function of the thalamus?
- it processes general and special sensory signals and relays them to their targeted locations of the brain
- regulates levels of awareness
what are the functions of the hypothaamus?
1) activates sympathetic nervous system
2) maintains body temperature
3) controls body osmolarity
4) controls reproductive functions
5) controls food intake
6) interacts with the limbic system to influence behavior and emotions
7) influences cardiovascular center in the medulla
8) secrets trophic hormones that control the release of hormones from the anterior pituitary gland
what is catecholamine?
a group of hormones that includes epinephrine, norepinephrine, and dopamine
how does the hypothalamus activate the fight or flight response of the sympathetic nervous system?
it controls catecholamine release from the adrenal medulla
how is the hypothalamus involved in blood glucose regulation?
it acts on the pancreas to release either insulin or glucagon
where in the brain is temperature sensed?
in the hypothalamus
how does the hypothalamus control body osmolarity?
it motivates thirst and drinking behavior and stimulates the secretion of ADH (vasopressin)
where is vasopressin produced?where is it stored?
in the supraoptic and paraventricular nuclei of the hypothalamus.it is stored in the posterior lobe of the pituitary gland
where is oxytocin produced and stored?
it is produced in the supraoptic and paraventricular nuclei of the hypothalamus and is stored in the posterior lobe of the pituitary gland
what are the functions of oxytocin?
promotes uterine contraction and lactation
how does the circadian rhythm work?
the suprachiasmatic nuclei send information related to how much day light is available to the pineal gland (where melatonin is stored) in times of darkness, melatonin release is promoted and makes us tired.
what are the functions of the cerebellum?
1) processes sensory information
2) coordinates the execution of movement
how do the hemispheres of the brain communicate?
through the corpus callosum
what is the function of the basal nuclei(ganglia)?
subconscious control of skeletal muscle.