BVMS1

• Endocrine
• neural
• neuro-endocrine

• rectpro message is blood borne message
• integrating centre is hormone secreting gland
• effector message is a hormone

• receptor message is nerve impulses
• integrating centre is central nervous system
• effector message is a nerve impulse

• rectpro message is nerve impulse
• integrating centre is central nervous system
• effector message is a hormone
• (ex: lactation)

peripheral nerve--> afferent neurone (into CNS)(sensory)--> interneurone-->efferent neurone (out of CNS)(motor)--> muscle gland

• Dendrites (recieve info)
• cell body (organelles for most metabolic activity integration of incoming information)
• axon (information transmission- long distance)
• terminals (transfer of information)
• synapse
• 

• unequal distribution of ions
• (concentration of ions- mMol/L)
• Na⁺ 150 extracellular 15 intracellular
• Cl^- 110 extracellular 10 intracellular
• K⁺ 5 extracellular 150 intracellular
• Ca²⁺ 1 extracellular 0.00007 intracellular

• (- intracellular concentration, + extracellular concentration)
• Na+/K+ pump (2 x K+ into cell, 3xNa+ out of cell- uses ATP)
• Differential permeability (Na+ leaks into cell, K+ and Cl- rush out of cell)
• Impermeable negatively charged molecules (positive out, neg in)

• K+ ions move out of cell down concentration gradient until the electrical force opposing ion movement equals the force created by the concentration gradient
• (membrane potential becomes more -)
• (chemical is balanced by electrical gradient)
• K+ ions move out of cell down concentration gradient until the electrical forces opposing ion movement equals the force created by the concentration gradient

membrane potential becomes more +

• the resting potential of a cell is determined by the relative permeability of the membrane to ALL ions
• changes in the permeability of the membrane to any ion results in a change in membrane potenial of that cell
• (adjusting the permeability to either K+ or Na+ will change the membrane potential)

• relative to the determination of membrane potential we have only discussed Na+ and K+ ion movement
• reason- movement of Na+ and K+ ions can explain the changes in membrane potential seen in most nerves and in some but NOT all muscles
• however, that doesn't mean that the movemet of other ions is not important...

• nerve and muscle cells are unique as their membrane potentials can be changed by a synaptic signal from an adjacent cell
• signal transmission relies upon changes in the activity of both chemically gated ion channels and voltage gated ion channels

• resting membrane ~-70
• if a stimulus does not created a graded potential to reach threshold- nothing will happen
• *the farther from the point of stimulas= smaller change in potential.
• the size of the respone is related to the size of the stimulus, in that it must reach threshold
• * we can stimulate or inhibit the membrane potential

• + feed back between membrane potential and Na+ permeability that leads to generation of an action potential:
• stimulus--> increased membrane Na+--> increased flow of Na+ into cell-->membrane potential decreased to threshold-->opening of voltage gated Na+ channels in membrane--> (back to) increased membrane Na+ permeability...
• **threshold movement of Na+ into cell exceeds movement of K+ out of cell
• (moves away from initial start point... further away from resting membrane potential each time stimulus applied)

• all or nothing response
• information about stimulus size coded as frequency!!
• **can NOT change the SIZE of the action potenital**

all channels are closed--> stimulus applied--> Na+ open quick, K+ open slow--> Na+ close (K+ are still open)--> K+ are slow to close

• (RMP--> stimulus--> Action potential--> depolarization-->hyper polarization--> re polarization)
• **remember bigger stimulus doesn't matter- only frequency**

• Absolute refractory period: further stimulation cannot generate a new AP. Na channels are open, no further depolarisation can occur
• relative refractory period: a larger change in the membrane potential is required to stimulate an AP. K channels open, any influx of Na+ is immediately balanced by movement of K+ (because it's hyperpolarized- it would need a greater stimulus to reach threshold)

• at rest all are closed
• activated (Na+ open)
• inactivated (abs. ref)- "bottom" of Na+ close- K+ is partially open
• At rest (closed)- "top" of Na+ closed, K+ is still open
• (K+ is SLOW to open and close!!!)

• Graded potentials: stimulus size is directly related to the size of the response
• action potentials: stimulus size is relative to action potential frequence
• small stimulus: stimulus causes opening of chemically gated channels, that gives rise to a graded potential that just exceeds threshold. cells fires APs as long as the cell is above threshold
• Larger stimuls: takes graded potentials much higher than threshold (reach threshold quicker), cells brought to threshold quicker after each AP thus frequency increased

a large abrupt stimulus is more likely to stimulate and AP than a stimulus of the same size applied slowly

blocking voltage gated Na+ channels

• time for gates to return to resting state cannot be stimulated! (ARP)
• (RRP)- would need greater stimulus to hit AP

• depolarized area (neg outside, pos inside) moves in all directions away from initial location- ('like a ripple')
• *current loops*
• the refractory period blocks the current loop from going back to polarized reigon- theis presence allows proper communication- not radical before movement
• - actions potentials normally move in one direction down an axon as they start at one end of the axon
• - APs normally begin at the axon hillock, move down the axon and sweep back over the cell

• Have shwan cells= insulation
• saltatory conductions: has advantages of speed and energy efficency (less na/k pumps)
• exactly same process- bit only one place current loops at nodes of ranvier.
• (used for fast info over long distance)
• **larger diameter of fiber also increases speed of transmission**

• Convergent systems
• divergent systems
• synapses

the activity of many cells influence the activity of ONE/few

the activity of ONE cell influences the activity of MANY

• electrical- gap junctions- direct current flow
• chemical- the MAJORITY- electrical signal-->chemical signal-->electrical signal

• 1) AP- depolarizes membrane
• 2) Ca2+ opens Ca2+ gated channels, Ca goes into cells= increase Ca concentration- migration of vesicles to synaptic clef
• 3) bonds to P.S. cell- decode signal
• 4) causes reaction in cell membrane (i.e- ion channels)
• 5) remove Neurotransmitter by diffusion or repackaged or destruction

• **always 1 direction!!, there are alot of Neurotransmitters some formed in body some formed in cell)
• (there is a time lag b/c of clef)

• (Post synaptic cell collects infor and decides what to use)
• Excitatory post synaptic potential (EPSP): graded potential on post synaptic cell- open Na+ channels= depolarizing cell membrane
• Inhibitory post synaptic potential (IPSP): open ion channels to make more permeable to K+ or less permiable to Na+
• (**by opening more Cl- channels= membrane is more stable)

• Temporal: same place on membrane over time
• spatial: over distance
• (see diagram)

• availability of NTs (if body or cell doesn't produce it- there will be no communication)
• availability of enzymes (see above)
• Ca2+ concentrations( if change extra cellular [Ca2+] increase = cell will be hyperactive)
• presynaptic receptors

• immediate history (IPSP, EPSP)
• Drugs
• disease
• NT concentrations in cleft
• NT agonist/antagonists
• Receptor concentrations (no receptor= no signal can be transferred)

• information comes in different forms: Touch, sound, light, pain, temperature, chemicals
• but w/in the body information is all transmitted as APs

• mechanoreceptors
• thermoreceptors
• nociceptors
• electromagnetic receptors
• chemoreceptors
• interpretation of the electrical signal occurs w/in the CNS

Stimulus: change in membrane permeability--> graded potential--> AP ( the higher above threshold the greater the AP FREQUENCY)

• membrane and fluid lamelli
• when pressure- fluid displaces causeing receptor potential
• after time- the membrane remains but fluid disperses so the receptor is no longer being stimulated until pressure is removed and fluid displaces once again
• (displaced fluid causes the receptor membrane to displace/be triggered)

• Complete adaptation (fast and slow)- stimulus is constantly applied- but receptors stop triggering
• incomplete adaptation (fast and slow)- stimulus is constantly applied but receptor information is reduced about half way

• energy filtering: ex: pacinian corpuscle
• Membrane effect: Ca2+ entry results in opening of K+ channels
• efferent control: iris of eye (size)
• slowly adapting receptors: infor about stimulus strength
• rapidly adapting receptors- info about rate of change

muslce (stretch receptor)-->AP (sensory neurone)-->dorsal roots (CNS)-->ventral roots--> AP (motor neurone)--> back to muscle

stretch receptor--> sensory neurone-->dorsal roots--> ventral roots--> motor neurone--> different muscle

• nuclear bag fibre vs. nuclear chain fibre
• efferent vs afferent

• more than one synapse in CNA
• slower than monosynaptic reflexes
• responses can be more prolonged due to variable number of synapses

when one muscle contracts antagonist muscle must relax