Download AP BIO- CH - Birdville ISD

AP BIOLOGY: Nervous & Muscle Physiology
TYPES OF NERVOUS TISSUE
1. supporting cells (some, not all)
-ependymal
-oligodendrocytes / schwann
-astrocytes
2. neurons
-sensory neurons, interneurons, motor neurons
-anatomy of a neuron (fig 48.2)
-longevity, amitotic, high metabolic rate
ELECTRICITY IN THE NEURON
-quick electricity review
-membrane potential created mainly by separation of Na+ and Cl- outside the membrane, K+ and negative proteins inside
HOW DOES A NEURON CARRY AN IMPULSE? (fig 48.9)
-neuron resting potential is about –70mV avg. (technically, diff. neurons may be more or less)
1. a graded potential must occur
2. graded potential must be strong enough to reach threshold (-60mV avg.)
3. if threshold is met, we now have an action potential
4. All or None Principle- Once threshold is met a nerve sends an action potential full strength…always.
FYI- A graded potential can go either way. It can depolarize (-69, -68, -67mV…) taking us closer to threshold and making
the neuron more likely to fire, or it can hyperpolarize (-71, -72, -73mV….) taking us farther away from threshold making
it less likely to fire.
SPECIFICS—See handout….note that Steps A –F coincide with diagram steps A-F.
Step A- the neuron ia @ resting state. (note location of Na+ and K+, also note the voltage graph at right)
Step B- a graded potential is created near the axon hillock. It is above threshold when it reaches the axon hillock and will
thus create an action potential (All or none)…The neuron is now going to fire
Step C- Na+ channels change shape at this threshold voltage…their gates open up. These voltage gated Na+ channels are
specific, they only let in Na+. Na+ goes in because of diffusion. As the Na+ enters, the inside of the neuron is becoming
more positive (note graph at right).
Step D- at a voltage of about +30mV (again see graph at right) Na+ channels change shape again…now they are closed.
BUT, voltage gated K+ channels now change to the open shape..following the concentration gradient, K+ now exits the
neuron.
Step E – at about –90mV, K+ channels close (K+ channels close slowly, hence the “undershoot”)
Step F- the Na/K pump (not shown in picture) will help to “reset” the membrane back to resting state so that the neuron
can fire again….
NEURON VELOCITIES (fig 48.11)
-speeds range from about 2mph to 350mph…why?
-diameter of neuron
-myelin sheath (saltatory conduction), cuts down on total nerve size
Alan Cotten, Fossil Ridge High- Keller ISD- Nervous & Muscle Physiology (Campbell 6th Ed.)
HOW DO IMPULSES “JUMP” FROM ONE NUERON TO THE NEXT?(fig 48.12)
Presynapse- secretes neurotransmitters (such as acetylcholine, serotonin, dopamine, etc.)
Synapse- contains “anti” neurotransmitter enzymes
Postsynapse- contains gated ion channels with neurotransmitter specific receptors
-diff. neurotransmitters = diff. effect on postsynaptic membrane (Dopamine, Serotonin, etc)
-EPSP (open Na+ channels…Na+ diffuses in)…such as glutamate
-IPSP (open Cl- channels…Cl- diffuses in)…such as GABA
-drugs, toxins, psychiatric prescription drugs, disorders related to neurotransmitters
-synaptic integration/summation (after all “a single motor neuron in the spinal cord may have as many as
50,000 synapses on it!!!)
FYI- Some neurons produce gases such as NO...NO results in dilation of surrounding vessels (nitroglycerin for heart
patients, little blue pills)
SKELETAL MUSCLE CONTRACTION (SLIDING FILAMENT THEORY)
How does it work? (fig 49.32-36)
Key words:
sarcomere
Thick filaments (made of myosin)
-contains ATPase
-mobile “crossbridges”
Thin filaments (made of F actin, which is made of G actin)
-contains attachment sights for crossbridges
-troponin / tropomyosin complex
-Calcium binding site impt.!!!
A bunch of thick and thin filaments bundle together to make a myofibril (myo = ?)
Myofibrils are surrounded by sarcoplasmic reticulum (holds Ca 2+ ions) and T tubules
Neurons (form nerves attach to the T tubules)
-motor units
-recruitment
MUSCLE METABOLISM AND OXYGEN DEBT, ETC
-muscle with adequate O2 vs. muscle with inadequate O2 (think back to mitochondria)
-Fast twitch vs. Slow twitch muscles (c/c)
-hypertrophy vs. atrophy (use it or lose it!!)
Alan Cotten, Fossil Ridge High- Keller ISD- Nervous & Muscle Physiology (Campbell 6th Ed.)