Chapter 3 Flashcards
What are the major divisions of the nervous system?
Central nervous system and peripheral nervous system
What is the central nervous system composed of?
the brain and spinal cord
What is the peripheral nervous system divided into?
sensory (afferent) nerves and motor (efferent) nerves
What do sensory nerves do?
informs the CNS about what is going on within and outside the body
What do efferent nerves do?
sends info from the CNS to the various tissues, organs, and body systems in response to the signals from the sensory division
What are motor neurons in the motor nerve?
neurons that project their axons outside the CNS to directly or indirectly control muscles
What are the two parts of the efferent nervous system?
the automatic nervous system and somatic nervous system
What is a neuron?
the basic structural unit of the nervous system
What are the 3 regions of neurons?
the cell body, dendrites, and axon
What is the axon hillock?
a cone-shaped region the cell body tapers into. Has a role in impulse conduction
What are dendrites?
the neuron’s receivers
How many axons and dendrites does a neuron have?
one axon and many dendrites
How do impulses/action potentials from sensory stimuli enter the neuron?
via the dendrites
What do dendrites do after they receive an impulse/action potential?
carry the impulse toward the cell body
What does the axon do in the neuron?
it’s a transmitter and conducts impulses away from the cell body
What happens at the end of an axon?
it splits into numerous end branches
What are the tips of end branches?
axon terminals
What are the vesicles in axon terminals filled with?
neurotransmitters
Explain how a nerve impulse travels through the neuron.
nerve impulses enter the neuron through the dendrites, to a lesser extent through the cell body then the axon hillock. it then travels down the axon and out through the end branches to the axon terminals.
What is excitable tissue?
neurons that can respond to various types of stimuli and convert those messages to a nerve impulse
How are nerve impulses started?
when a stimulus is strong enough to substantially change the normal electrical charge of a neuron
What happens after a nerve impulse is formed?
the signal moves along the neuron, down the axon, and toward another neuron or group of muscle fibers.
Explain the cycle of an electrical signal/nerve impulse
The electrical signal for communication between the BRAIN and MUSCLE is generated by a stimulus, then propagated down an axon, and transmitted to the next cell in line
What is the resting potential of the cell membrane of a neuron
-70mV
How does the electrical charge work for a cell at resting potential?
the electrical charge inside the cell and the one outside of the cell would differ by 70mV. The inside would be negative relative to the outside
What is resting membrane potential (RMP)?
the electrical potential difference
What is the RMP caused by?
the imbalance in the number of ions inside and outside the cell membrane
When is the membrane polarized?
when the charges across the membrane differ
Why is the resting potential of a neuron’s cell membrane 70mV?
because of the difference in how potassium and sodium ions move. it’s more positive outside than inside.
The neuron has a high concentration of what on the inside of the membrane?
potassium ions (K+)
The neuron has a high concentration of what on the outside of the membrane?
sodium ions (Na+)
How is the ion imbalance maintained without the sodium-potassium pump?
ions will move to establish equilibrium. some K+ ions will move to the area where they are less concentrated, outside the cell
Why can K+ move more freely in the cell membrane?
the cell membrane is more permeable to K+ than Na+
How is the ion imbalance maintained with the sodium-potassium pump?
Na+ – K+ – ATPase actively moves potassium ions in and sodium ions out
What are two ways the ion imbalance in a cell membrane are maintained?
K+ moving to establish equilibrium and sodium-potassium pumps in neurons
How many ions are moved by the sodium-potassium pumps?
3 Na+ ions are moved out of the cell for each 2 K+ ions it brings in
What is the primary function of the sodium-potassium pumps?
maintaining a constant RMP of about -70mV
What is the sodium-potassium pumps fueled by?
ATP
What is happening when the membrane is depolarized?
the inside of the cell becomes less negative making the potential difference across the membrane decrease
What is depolarization?
when the inside of a cell becomes more positive
What happens in depolarization?
The sodium channels are open. -70mV to 0
What does depolarization cause?
movement