Chapter 48 Flashcards
Function of nervous tissue
Functions in the receipt, processing, and transmission of information
Nervous tissue contains…
Neurons/nerve cells which transmit nerve impulses, and glial cells/glia which support cells
Glial Cells
Insulation cells which has numerous functions to nourish, support, and regulate neurons
Different Glia cells in CNS
Ependymal cells (make CSF), Astrocytes (provide brain cells with food), Oligodendrocytes (help electronic signals move faster), and microglia (help fight infection)
Different Glia in the PNS
Schwann cells (mylinate neurons in PNS)
Two ways that neurons transfer information within the body
Electrical signals (long-distance) and chemical signals (short-distance)
Three stages of nervous system processing
Sensory input, integration, motor output
What do sensory neurons do?
They transmit information form sensory that detect external stimuli (light, sound, heat, smell, taste, touch) and internal stimuli (blood pressure and muscle tension)
What do interneurons do?
The vast majority of neurons in the brain are interneurons, which form connecting neurons in the brain
What do motor neurons do?
They transmit signals to muscle cells, causing them to contract
What is membrane potential?
The differential distribution of ions between the outside and inside of the cell ; generates voltage (difference in electrical charge)
What is resting potential?
The membrane potential of a neuron not sending signals (inside is negative)
What are action potentials?
Changes in membrane potential ; these signals are conducted by axons
What to sodium-potassium pumps do?
They use energy of ATP to transport K+ into the cell and Na+ out of the cell
What do the concentration gradients represent?
Chemical potential energy.
What can a neuron at resting potential do?
It contains many open K+ channels and fewer open Na+ channels, so K+ diffuses out of the cell, resulting in a negative charge (-70)
What goes in and out of pumps?
3 Na+ out, 2 K+ in
What goes in and out of channels?
Na+ in, K+ out
What is the equilibrium potential difference for K+ permeable vs Na+ permeable?
K+ is -90 while Na+ is +62
Difference between gated ion channels and voltage-gated ion channels
Gated ion channels open or close in response to stimuli, while voltage-gated ion channels open or close in response to a change in voltage across the plasma membrane
What is hyperpolarization?
An increase in magnitude of the membrane potential making the inside of cell more negative
What happens if gated K+ channels open in a resting neuron
The membranes permeability to K+ increases, net diffusion of K+ out of neuron, membrane potential shifts closer to -90mV, and inside of membrane is becoming more negative
What is depolarization?
A reduction in the magnitude of the membrane potential of a cell making the inside less negative
What happens when gated Na+ channels in neurons respond to a stimulus?
The membranes permeability to Na+ increases, Na+ diffuses into the neuron, membrane potential shifts towards ENa (+62mV), and the inside of the membrane becomes more positive
What do each of the polarizations do to the chance of a neuron transmitting a nerve impulse?
Hyperpolerization reduces the change, depolarizations increase the chance
What are graded potentials?
Changes in polarization where the magnitude of the change varies with the strength of the stimulus (stronger stimulus, stronger change in magnitude)
What are some properties of action potentials?
They have a constant magnitude, are all-or-none, and they transmit signals over long distances
What a refractory period?
The period after an action potential when a second action potential cant be initiated
What happens when there are mutations in voltage-gated Na+ channels?
It leads to abnormal neural firing and associated disease phenotypes called channels-atheism
Why are the toxins in animal venom so deadly?
Because they target Na+ channels
What are myelin sheaths made by and what do they do?
They are made by glia (oligodendrocytes in CNS and Schwann cells in PNS) and they cause an action potentials speed to increase
What are the gaps in myelin sheath called?
Nodes of Ranvier
What is saltatory conduction?
When action potentials in myelinated axons jump between the nodes of Ranvier
What is multiple sclerosis (MS)?
It is an autoimmune disease where the body’s immune system attacks the myelin of nerve fibers in the CNS
What happens at electrical synapses?
The electrical current flows from one neuron to another through gap junctions
What happens at chemical synapses?
A chemical neurotransmitter carries information between neurons (most synapses are chemical)
What happens to neurotransmitters in the chemical synapse?
Neurotransmitter binds to a ligand-gated ion channel, causing them to open, which generated a postsynaptic potential. The neurotransmitter’s chemical signal is transducer to an electrical signal changing the membrane potential of the postsynaptic cell
What are excitatory postsynaptic potentials (EPSPs)?
They are depolarizations that bring the membrane potential toward threshold
What are inhibitory postsynaptic potentials (IPSPs)?
They are hyperpolarizations that move the membrane potential farther from threshold
What is summation?
It is when the individual postsynaptic potentials combine to produce a larger potential
What is temporal summation?
It is when two EPSPs are produced in rapid succession
What happens in the termination of neurotransmitter signaling?
The chemical synapse returns to its resting state and the neurotransmitter molecules are cleared from the synaptic cleft
What does Sarin nerve gas do?
It triggers paralysis and death due to inhibition of the enzyme that breaks down the neurotransmitter controlling skeletal muscles
How many receptors can a single neurotransmitter bind to?
More than a dozen
What is Acetylcholine?
It is a common neurotransmitter in vertebrates and invertebrates, involved in muscle simulation, memory formation, and learning
Three main amino acids
Glutamate, glycine, and gamma-aminobutyric acid (GABA)
What is glutamate?
Amino acid that can act as a neurotransmitter in vertebrates and invertebrates
What is glycine?
Glycine acts at inhibitory synapses in parts of the CNS outside the brain
What is GABA?
Gamma-aminobutyric acid ; the neurotransmitter at most inhibitory synapses in the brain
What is bio genie amines and what are some common examples?
They have a central role in a number of nervous system disorders ; include norepinephrine (made from tyrosine), epinephrine, dopamine (lack of creates Parkinson’s), and serotonin
What is Parkinson’s Disease?
It is a motor disorder with symptoms that include muscle tremors, poor balance, flexed posture, and shuffling gait ; involves death of neurons in midbrain that normally release dopamine
What are neuropeptides?
They are relatively short chains of amino acids which also function as neurotransmitters ; They affect our perception of pain ; includes substance P and endorphins ; opiates bind to the same receptors and endorphins and can be used as painkillers
What are gases (neurotransmitter)?
Gases like NO are local regulators in the PNS and they are broken down within seconds of production ; NO is not stored in cytoplasmic vesicles, bit is synthesized on demand
What are the main kinds of neurotransmitters?
Acetylcholine, amino acids, biogenic amines, neuropeptides, and gases
