Midterm 1 Flashcards
What receptors cause depolarzation when bound to ligand?
Glutamate: NMDS, AMPA, kainte, Nicotinic acetylcholine recpetors, 5-HT3, P2X
What receptors cause hyperpolarization when boudn to ligand?
GABA and glycine
how does magnitude of graded potential respond to distance from open ion channel
The graded potential decreases with increasing distance from channel
causes of decrement in graded potential
- leakage of charged ions across membrane
- electrical resistance of cytoplasm
- electrical resistance of membrane
causes of decrement in graded potential
- leakage of charged ions across membrane
- electrical resistance of cytoplasm
- electrical resistance of membrane
3 characteristics of Action Potentials
- triggered by graded potential @ axon hillock, do not degrade over distance
- travel along distance along membrane
- all or none response
- MUST reach threshold to fire
3 phases of Action potential
depolarization, re-polarization and hyperdepolarization
3 phases of Action potential
depolarization, re-polarization and hyper-depolarization
is it possible to generate a new AP during teh absolute refactory period?
NO
is it possible to generate a new AP during the relative refractory period?
Yes but it is more difficult
How does inhibitory neurotransmitters effect the the axon?
The inhibitory neurotransmitter hyper polarizes the cell making it less likely to generate an AP
What neurotransmitters DO NOT have a degrative enzyme in the synaptic cleft?
GABA, glutamate,
These nerves carry sensory information into the central nervous system
Afferent
These Nerves carry motor information out the CNS
efferent: can be somatic or visceral
Movement of smooth muscle in the digestive system is controlled by _________ nerves
autonomic or visceral
rostal also means
anterior
caudal also means
posterior
CNS Ventricles
Cavities within the CNS where Cerebrospinal fluid circulates due to cilia
where is the pons located
rostral to the medulla
Pons
- Pathway between medulla, cerebellum and forebrain
- controls, alertness, initiates sleep and dreaming
- Linked to cerebellum: motor controls
CEREBELLUM
motor coordination and contains 50% of neurons int eh brain
Medulla Oblongata
autonomic regulation: breathing, heartrate, dilation/contriction of blood vessels, blood pressure.
Many cross overs: left and right; sensory and motor
What part of the brain is response for the startle response to auditory or visual stimuli?
Midbrain
what parts of the brain make up the ‘brainstem’?
pons, medulla and midbrain
another term for tectum (fish/amphibians)?
colliculi (mammals)
which is more rostral in humans the superior or the inferior colliculi?
Superior
How many pairs of cervical nerve cords are there?
8
how many pairs of thoracic nerve roots?
12
How many pairs of lumbar nerves roots?
5
How many pairs of sacral nerve roots?
5
Dermatome
territory innervate from single dorsal root ganglion and spinal nerve
Rapidly adapting afferents
after continued stimulation the AP become stable
Slow adapting afferents
continue to respond with AP for the duration of the stimulus.
Merkel Cell Afferents
- 0.5mm spatial resolution
- slowly adapting
- fingertips
- points, edges and curvature= form and texture
Pacinian Afferent
- deep in dermis
- rapidly adapting
- MOST sensitive
- > 10mm spatial resolution
- high frequency vibrations (5-1000Hz)
- sense vibrations through an object
Meissner Afferent
- 3mm spatial resolution
- rapidly adapting
- low frequency vibrations (1-300Hz)
- closest to skin surface
- 4x more sensitive than merkel afferent
- transduce info when texture object moves across skin=GRIP
Ruffini Afferent
- deep in skin
- slowly adapting
- > 7mm spatial resolution
- responsive to internally generated stimuli
- gives accurate info on position and conformation
- typing, playing piano , etc
Starting at the the surface of skin list the levels of Mechanoreceptors
- Meissner
- Merkel
- Ruffini
- Pacinian
If a pathway uses the nervouse system but only one kind of chemical messenger what kind of feedback is it?
First Order Feedback
IF a pathway uses Two chemical messenger but not an integration system what kind of Feedback is it?
Direct Feedback (secondary?)
What hormones does the Posterior pituitary release
oxytocin and vasopressin
Is the Posterior pituitary first order, second order or direct feedback?
First order
What kind of hormones does the anterior pituitary release?
tropic hormones that stimulate the release of another hormone from the target organ EG. ACTH (adrenocorticotropichormone)
Oxytocin Pathway
Stretch cells-> hypothalamus–>Postpituitary–>Oxytocin–> uterine contraction
is the oxytocin cervixe pathway positive or negative feedback?
Positive. Increased stretch leads to the release of more oxytocin that causes uterine contraction.
Insulin
Decreases blood glucose levels and is released when blood glucose is high
Glucagon
increases blood glucose levels and released when the blood glucose is low
what cells in the pancreas release glucagon?
alpha
what cells in the pancreas release insulin?
beta
the insulin binds to ___________recepetors
tyrosine kinase
what pathways does glucagon activate?
Adenylyl cyclase pathway(activates PKA by converting ATP to cAMP), PKA pathway (phosphorylates GPK) and GPK (breaks down glycogen to glucose)
GLUT1
all tissues, very high affinity and works at low concentrations
Glut2
expressed on surface of Beta cells, bidirectional transporter, low affinity and requiers a high concentration of glucose
Glut3
in brain, work constantly
Glut4
within muscle and fat tissues, when insulin binds it activates the pathway that phosphorylates GLUT4 causing it to translocate to the cell surface. UNIDIRECTIONAL (glucose in NOT out)
what diabetes is insulin dependent?
Type 1, beta cells are destroyed by immune system
when is the sympathetic nervous system most active?
Stress or exercise
what hormone does the adrenal medulla release
epinephrine
Epinephrine
targets tissues to increase blood glucose, increased glucagon by alpha cells and suppress beta cells.
what hormones does the adrenal cortex secrete?
cortisol and targets cells to increase blood glucose levels
what produces a greater response additivity or syngergism?
synergism (glucagon+epinephrine+cortisol)
what part of a neurons receives an incoming signal?
dendrites
what part of the neuron is responsible for signal integration?
axon hillock
What part of the neuron is responsible for signal transduction?
axon
depolarization
the membrane becomes more positive
hyperpolarization
the membrane becomes more negative
does potassium have a higher concentration inside or outside the neurons when it is at rest?
outside
what factors contribute to membrane potential?
- distribution of ion channels across membrane
- relative permeability of ions due to leak channels
- charge of ions
ATP synthase
3NA+ outside
2K+ inside
conductance approximates permeability and is the _______of resistance
g=1/R
equation for electrochemicl driving force
Ik=gk(Vm-Ek)
as positive ions move into the cell the current is
negative
as negative ions move out the cell the current is ______
negative current
as positive ions move out of the cell the current is ________
positive
name four ligand gated ions channels
GABA, glycine, nicotinic aceytlcholine
Capicitance
ability of a membrane to hold a charge when voltage difference between two surface
three features that determine teh capacitance of the membrane
- material properties (ie. lipids, proteins, etc.)
- area of the 2 conducting surfaces: larger area = larger capacitiance
- thickness of the insulating layer: greater thickness= lower capacitance
Time constant
time over which the membrane reaches 37% of maximal value (hoe does it hold a charge)
variables that affect the time constant
resistance of cell membrane, capacitance of cell memebrane
a low resistance (rm) or low capacitance (cm) results in ….
a faster conduction, faster depolarization, capacitor fills up faster
increased resistance of intra/extracellular fluids=»»
decreased voltage over distance of axon
sodium and calcium voltage gated ion channels lead to
depolarization
opening of voltage gated potassium chanels lead to …..
hyperpolarization
how does the magnitude of a graded potential change within respect to distance from the ion channel?
graded potential decreases with increasing distance from the ion channel
longer membranes with larger cells have ______ resistance due to ______ leak channels
decreased resistance; greater leak channels
both impede the flow of ions through the cell
how does diameter of an axon effect conduction velocity?
as the diameter increases the conduction velocity increases
how does a low Rm effect the length constant and conductance speed
the length constant decreases; conductance speed decreases
