HPHY 322 Midterm 2

• selectively permeable bi-layer
• lipid soluble substances diffuse easily
• otherwise require protein channel

ion movement across membrane

ion movement that requires interaction with a protein to move across membrane

• ion movement across membrane that requires interaction with protein and energy
• against the gradient

pumps Na+ out and K+ in

Through maintenance of electrochemical gradients and gated channel reactions, action potentials can occur and permit "communication" between cells/neurons.

• 
• maintains gradients
• helps produce negative membrane potential
• requires energy

• Electrical difference (voltage) when comparing the outside and inside of the cell membrane  (mV)
• refer to the voltage inside the membrane relative to the outside

• calculates electrical potential required to balance a single ion's concentration gradient
• 

The membrane potential of the cell combining information about multiple ions' permeability and concentrations

between -70 and -90mV

• 1. Resting membrane potential
• 2. Depolarizing stimulus
• 3. membrane depolarizes to threshold. Voltage-gated Na+ channels open and Na+ enters cell. Voltage-gated K+ channels begin to open slowly.
• 4. Rapid Na+ entry depolarizes cell.
• 5. Na+ channels close and slower K+ channels open.
• 6. K+ moves from cell to extracellular fluid
• 7. K+ channels remain open and additional K+ leaves cell, hyperpolarizing it.
• 8. Voltage gated K+ channels close, some K+ enters cell through leak channels.
• 9. Cell returns to resting ion permeability and resting membrane potential.

Next action potential can being during relative refractory period, but only if there is a more positive graded potential than usually necessary to meet threshold

starts above threshold at its initiation point but decreases in strength as it travels through the cell body

• 1. action potential depolarizes the axon terminal
• 2. depolarization opens voltage gated Ca2+ channels and Ca2+ enters the cell
• 3. Calcium triggers exocytosis of synaptic vesicle contents
• 4. neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell

• 1. NT degraded by enzymes on receptor protein
• 2. NT re-sequestered into presynaptic axon terminal or diffuses away from synapse

found on ion channels

• activate a G-protein complex which results in:
• 1. ion channel opening
• 2. 2nd messenger activation

Whether the stimulus causes the membrane potential to become more positive (excitatory) or more negative (inhibitory).

• cardiac muscle
• smooth muscle
• retina
• odor receptors
• liver

• guanosine nucleotides
• three- alpha, beta, gamma

GDP (guanosine diphosphate)

conformational change on G-Protein causes GDP to be swapped for GTP and the G-Protein complex is associated with receptor

• 1. open an ion channel
• 2. affect intracellular enzymes
• a)adenylyl/adenylatecyclase
• b)phospholipase C

• converts ATP into cAMP
• cAMPa activates Protein Kinase A (PKA)

can phosphorylate (activate) a protein

• stimulatory- causes adenylate cyclase to increase production of cAMP
• inhibitory- causes adenylate cyclase to decrease production of cAMP

deactivates cAMP

• stimulates phospholipase c (PLC)
• PLC cleaves phosphondylinositol (PIP2) into: diacylglycerol (DAG) + Inositol triphosphate (IP3).

cAMP, IP3 & DAG

nicotinic cholinergic

acetlycholine activates nicotinic receptors (opening chemically gated channels on the sarcolemma) leading to sodium influx

voltage gated Na+ channels open and action potentials move along sarcolemma

sarcoplasmic reticulum

mechanical change in ryanodine channels on the SR

• 1. ACh released from alpha motorneuron at the NMJ
• 2. AP in sarcolemma and T-tubules
• 3. DHP receptors in T-tubules react to depolarization
• 4. open ryanodine Ca2+ channels on SR

tropomyosin

• 3 polypeptides
• TnI- binds to actin
• TnT- binds to tropomyosin
• TnC- binds to Ca2+

• 1. action potential from motor neuron
• 2. calcium released from SR
• 3. available ATP

• 1. Z-lines move closer together
• 2. sarcomeres shorten
• 3. I bands shorten
• 4. A bands stay the same length
• 5. H bands shorten

ATP is broken down into ADP+Pi at the myosin head

• 1. rigor state- tight binding between G-actin and myosin
• 2. ATP binds to myosin head - dissociation
• 3. myosin head ATPase breaks down ATP into ADP+Pi
• 4. released energy changes angle between myosin head and myosin filament ("cocked" position)
• 5. power stroke: ADP + Pi are released
• 6. back to rigor state

two-way highway, plus reflex control

all but cerebral cortex; unconscious control

cerebral cortex; thinking & memory integration

muscle spindles send action potentials along afferent neurons to synapse at the spinal cord with alpha motor neurons to the agonist muscle

• afferent information to CNS regarding
• 1. length
• 2. rate of change in length

• afferent information to CNS regarding:
• 1. tension
• 2. rate of change in tension

• 1. complexity of receptor
• 2. fiber type/size & distance travelled
• 3. number of synapses

• large to medium in size
• myelinated

• small
• unmyelinated

• size of receptor field per afferent neuron
• receptor density
• "lateral inhibition" 
• convergence of first order neurons onto second order neurons

achetylcholine, norepinepherine, epinepherine

• mostly release norepinephrine
• some epinephrine
• few acetylcholine

• cells of the adrenal gland originated embryologically as nervous tissue and are rudimentary postganglionic neurons that secrete neurotransmitters into blood
• epinephrine 80%
• norepinephrine 20%

g-protein couple receptors that open ion channels directly or produce second messengers

• parasympathetic- long presynaptic neurons are myelinated and fast
• sympathetic- medulla of adrenal glands release epi into bloodstream which takes time to clear

neurologic dysfunction from biomechanical force

a type of brain injury caused by shearing forces that occur between different parts of the brain as a result of rotational acceleration

• - inability to clean up excess K+
• - inability to transmit signals

• neuronal activity 
• metabolic waste byproducts

• fatigue
• persisting symptoms
• exertion-based symptoms (headache)

• 1.light enters eye: focused by lens onto the retina 
• 2. photoreceptors transduce light energy: change it into electrical signals
• 3. Electrical signals transmitted to brain: eventually allows visual perception.

through retinal cells, is absorbed in posterior layer of eyeball, then stimulates the photoreceptors.

dim light, night vision, black & white, dominate periphery of retina

color vision, mostly cones are found in fovea

Melanin in pigmented epithelium

• photochemical rhodopsin changes from 11-cis to all-trans 
• changes to its activated form

• ligand - photon
• coupled g-protein receptor - rhodopsin
• g-protein - transducin

• PDE
• breaks down cAMP or cGMP

changes shape and activates g-protein transducin

• 1. cGMP gated channels = Na & Ca influx
• 2. K leak channels, allowing efflux
• 3. Na/K ATPase pump
• -40mV membrane potential

hyperpolarize

• rhodopsin is inactive
• cGMP is high
• and ion channels are open
• releases neurotransmitters

• light bleaches rhodopsin
• opsin decreases cGMP
• ion channels are open
• hyperpolarization
• does not release NT

decreases NT release

rods and cone synapse with bipolar neurons which synapse with ganglion cells

ganglion cell axons

in the lateral geniculate nucleus of the thalamus

• perception of frequencies 
• higher frequency = higher pitch 
• normal from 20-20,000Hz

• perception of intensity
• normal 0-120 dB

• ossicular coupling
• transfers energy from tympanic membrane to the foot plate of stapes

works at low frequencies , works at high frequencies

dissipate energy

• supporting cells
• one row of inner hairs
• three rows of outer hairs 
• 16,000

covers hairs

different pivotal points

biggest hair

• opens mechanically gated ion channels 
• inward K and Ca current causes graded potential and release of NT glutamate
• cochlear fibers transmit impulses to the brain

• close K channels
• hyperpolarization

• depolarization
• opens channels
• increase NT

• some channels open
• no stimulus

• all channels open
• depolarization

• all channels close
• hyperpolarization

double the ability to perform exocytosis

• vesicles
• Ca & Ca channel
• action potential 
• NT

inervated by efferent neurons

send afferent signals

the portion closes to the apex

the portion close to stapes

disolved in aqueous solution mucus or saliva

• the taste receptor cell depolarizes when stimulated due to opening of ion channels or 2nd messenger actions
• the taste receptor cell releases a NT onto the sensory nerve fibers, which transmits the signal via action potential

vagus, glossopharyngeal, facial

• brain stem
• thalamus
• sensory cortex
• gustatory cortex (insula)

• taste stimuli produce this reflex
• synapse in the thalamus with efferent neurons to salivary glands

• G-protein coupled receptor in cilia
• activates adenylate cyclase
• increases cAMP
• opens cAMP gated sodium channels
• depolarization of cell beyond -55mV

in the membrane of the cilia or hairs

• reflexes related to salvation- hypothalamus & limbic system
• memory of food likes and dislikes- hippocampus and/or cortex
• analysis of smells- thalamus & frontal cortex