A&P Gen Bio

Negative feedback

When a change in a physiological variable triggers a response that counteracts that change, brining the variable back to its desired set point

Positive feedback

When a stimulus leads to a response that further increases the stimulus, resulting in a greater change in the same direction

Sensor

Detects the stimulus

Controller

Process signals

Effector

Executes the response

Regulated variable

Specific physiological parameter in the body that is maintained within a certain range

Yeah I did

Look at body temp regulation slide

35.9 - 36.9

Body Temp Set Point

Sensor for body temp

Sensory receptors in skin

Controller for body temp

Hypothalamus

Effector for body temp

Blood vessels vasodilate and

Feedforward control

Expectation of new stimulus changes set point

Homeotherms

Animals that maintain a constant body temperature

Poikilotherms

Animals with fluctuating body temperatures

Ectotherms

Body temp depends on external sources of heat

Endotherms

Control their own heat

Heterotherms

Both control their own heat and use the environment

Endotherms

Produce more heat so are less efficient than their conjugate

CNS

Brain & spinal cord

Sites of information processing and storage

PNS

Provides communication between the CNS and all of the rest of the body

Neurons

Generate and conduct electrical signals

Astrocytes

CNS

Support neurons, regulate blood brain barrier

Ependymal cells

CNS

Lines ventricles and produces CSF

Oligodendrocytes

CNS

Produces myelin (ONLY IN THE CNS)

Microglia

CNS

Immune cells, remove debris

Schwann cells

PNS

Produce myelin (ONLY IN PNS)

Satellite cells

PNS

Protection

Similar to astrocytes

Cell body/Soma

Contains nucleus and organelles

Dendrites

Bring information to the cell body

Axon

Carries information away from the cell body

Axon terminals

At the tip of the axon

Order

Ganglion → (Retina) Bipolar → Cerebral Cortex

Action potentials

Small changes in membrane electric potential that generate large, rapidly reversed changes in membrane potential

Generated at the axon hillock

Synapse

Receiving + delivering section + gap btwn neurons

Synaptic cleft

JUST the space between neurons

Electrical synapse and chemical synapse

2 kinds of synapses

• First allows action potential to pass directly between two neurons

• Second is more abundant but slower, uses neurotransmitters

Membrane potential

Electrical charge difference across a cell membrane

Resting potential

Steady state membrane potential of a neuron

-70 millivolts

The resting potential of an axon

Ions

K+ ^

Na+, Ca2+ v

Resting Membrane Potential

RMP

4 Types of Channels

Leak Channels

Ligand-Gated Channels

Mechanically-Gated Channels

Voltage-Gated Channels

Always open

When are leak channels open?

Graded Potentials

Communications over short-distances

Short-lived, localized changes in membrane potential

Stronger stimulus → voltage changes; farther current flows

• Impulse is the same, regardless of strength

Dies out w/in a few minutes

Muscle fibers

Elecrically exciteable neurons

Depolarizing

Line on graph becomes more positive

At threshold (-55 mv), all Na + channels open

• Depolarizing local currents open voltage-gated Na+ channels, and Na+ rushes into cell

• Na+ activation/inactivation gates oepn

• Na+ influx causes more depolarization, which opens even more channels

• ICF becomes less negative

• Membrane polarity jumps to +30mv

• Results in large action potential spike

Repolarization

Line on graph becomes less positive, returning to it’s resting state

Na+ channels inactivate

• Na+ channel inactivation gates close

K+ channels open

• Voltage-gated K+ channels open

• K+ exits cell down its electrochemical gradient

AP spike stops rising

Hyperpolarization

Line on graph becoming more negative

• Some K+ channels remain open, and Na+ channels reset

• Some K+ channels remain open, allowing for excessive K+ efflux

• Inside of membrane becomes more negative than in resting state

Na+ channels also begin to reset (inactive → closed)

-55 mv

Threshold

-70 to 30 mv

Range of stimulus mv

Resting state

All gated Na + and K + channels closed

Only leakage channels for Na + and K + are open

Activation gates

Type of Na + channel voltage-sensitive gate

Closed at rest, blocking Na +; open with depolarization, allowing Na+ to enter cell

Inactivation gates

Type of Na + channel voltage-sensitive gate

Open at rest; block channel once it is open to prevent more Na+ from entering cell

Na + channels automatically blocked by inactivation gates soon after they open

All-or-none principle

When a stimulus reaches a threshold, AP/amplitude are always the same, so it will reach +30 or not do that. There is no inbetween

Absolute refractory period

Time during which a neuron or muscle cell is completely

Depolarization and repolarization

Relative refractory period

A second strong stimulus during the ____ (hyperpolarization) can give rise to a second action potential

Phase following an action potential during which a neuron or muscle cell can generate another ap, after a stronger than normal stimulus

Saltatory

Jumping (type of conduction), myelinated

Elsa won

Continuous

Unmyelinated, walking

Shawn lost