Chapter 43 - The Nervous System Flashcards
All animals must be able to respond to ___________
Environmental Stimuli
- Detect stimulus (light, heat, touch)
- Ex. Photoreceptors, chemoreceptor
Sensory receptors
- Respond to sensory receptors
- Ex. Muscle, gland
Motor effectors
Consists of the brain and spinal cord
Central Nervous System
Consists of sensor and motor neurons
Peripheral Nervous System
Three types of neurons
- Sensory neurons
- Motor neurons
- Interneurons
Carry impulses to CNS
Sensory neruons
Carry impulses from CNS to effectors
Motor nuerons
- Provide more complex reflexes and associates functions
- Majority of neurons
- Learning and memory
Interneurons
Three parts of a nueron
- Cell body
- Dendrites
- Axon
Enlarged part of neuron containing the nucleus
Cell body
Short, cytoplasmic extensions that receive stimuli
Dendrites
Single, long extension that conducts impulses away from cell body
Axon
Supports neurons
Neuroglia
Multiple layers of cell membranes wrapped around axons
Myelin sheath
Two neuroglia in CNS
- White matter
2. Grey matter
Myelinated axons form _____?
White matter
Dendrites/cell bodies form ____ ?
Gray matter
Type of neuroglia in the PNS
Nerves
Myelinated axons are bundled to form ________
Nerves
A potential difference exists across every neuron’s plasma membrane
Membrane potential
Charge of cytoplasmic side?
Negative
Charge of extracellular fluid side?
Positive
Cytoplasm is negatively charged because of ____
Sodium -potassium pump
Brings two k+ into cell for every three Na+ pumped out
Sodium-potassium pump
- Moves away from poles (-70mv) and toward neutral (0mV)
- Because cytoplasm is negatively charged, ___________ makes the membrane potential more posotive
Depolarization
Voltage change makes it extremely negative (lower than -70mv)
Hyperpolarization
A change in membrane potential that moves down the axon
Action potentials
The cycle of action potentials
- From resting
- To depolarization
- To hyperpolarization
- Back to resting
Action potentials are proliferated by ________
Voltage-gated ion channels
What are the voltage-gated ion channels?
- Na+ channels
- K+ channels
_________ channels open first??
Na+ channels
What two things do Na+ open channels cause?
- An influx of Na+
2. Depolarization
_________ channels open second??
K+ channels
What two things do K+ channels cause?
- Cause the exist of K+
2. Hyperpolarization
When depolarization occurs, the change in charge is detected by __________
The adjacent Na+ channels
Once the cytoplasm is positive enough, it will cause ____
- The next channels to open
- Na+ to move in
- Depolarization to move down the axon
The positive point in action potential is known as _______
Threshold
___________ follows depolarization down the axon
Hyperpolarization
When hyperpolarization happens, what happens to the voltage gated ion channels?
- The K+ channels open after the Na+ ones do
2. This causes K+ to rush OUT
Comparative Chart for Na+ channels and K+ channels
Na+ Channels
- Open quickly
- Na+ flows into the cell
- Open first
- Depolarizes
K+ Channels
- Open slowly
- Na+ moves in
- K+ rushes out
- Hyperpolarizes
- Before an action potential
- -70mV
- Na+ moves downstream
- Contacts the voltage gated ion channel
- Raises the voltage
Resting potential
- First phase in action potential
- Enough Na+ can cause the voltage gated ion channel to open
- Na+ flows through the channel into the cell
- The region becomes depolarized
Rising action potential
- K+ voltage gated ion channels open next
- K + flows out of the cell
- Repolarizes cell to become negative
Falling action potential
- All the K+ causes the cell to become hyperpolarized
- Less negative than -70 mV
Undershoot