chp 11-14 Flashcards
What are the functions of the nervous system?
Maintain homeostasis, receive sensory input, integrate information.
What are the divisions of the nervous system?
CNS (brain and spinal cord) receives and sends information to the body; PNS (all nervous tissue outside CNS) detects stimuli and communicates information between the CNS and the body.
Differentiate between the somatic and autonomic nervous systems.
Somatic is the voluntary division of the motor division; Autonomic is the involuntary division of the motor division.
What does afferent refer to?
Toward the CNS (sensory division).
What does efferent refer to?
Away from the CNS (motor division).
Break down the divisions of the nervous system.
CNS includes the brain (control center) and spinal cord (pathway for nerves); PNS includes Somatic (voluntary movement) and Autonomic (regulating involuntary body functions).
What are the divisions of the autonomic nervous system?
Sympathetic (prepares for fight or flight), Parasympathetic (rest and digest), Enteric (controls the digestive tract).
Describe the structure of neurons.
Neuron cell body (single large nucleus), dendrites (short and highly branched), and single axon (arises from axon hillock).
What are the functions of the components of a neuron?
Neuron cell body/soma performs typical cell functions; Dendrites receive information; Axon transmits electrical impulses.
Classify neurons based on structure.
Multipolar (many dendrites, single axon), bipolar (one dendrite, one axon), pseudo-unipolar (appears to have an axon and no dendrites), anaxonic (no axons, only dendrites).
Classify neurons based on function.
Sensory neurons (afferent, conduct action potentials toward the CNS), Motor neurons (efferent, conduct action potentials away from the CNS), Interneurons (conduct action potentials within the CNS).
Describe the location, structure, and functions of CNS glial cells.
Provide structural and functional support to neurons. Astrocytes maintain the blood-brain barrier; Ependymal cells produce cerebrospinal fluid; Microglia act as immune cells; Oligodendrocytes produce and maintain myelin sheath.
Describe the location, structure, and functions of PNS glial cells.
Schwann cells form myelin sheaths around one axon; Satellite cells surround neuron cell bodies in ganglia, providing support and nutrition.
What is the function of the myelin sheath?
Myelin protects and insulates axons, speeds transmission, and aids in repair of axons.
What happens to nervous tissue in response to injury?
Axon distal from cut breaks into segments; Schwann cells degenerate; macrophages clear debris; Schwann cells form a column for regeneration.
Describe the formation of myelin sheaths in the CNS and PNS.
CNS: oligodendrocytes myelinate multiple axons; PNS: Schwann cells myelinate one axon segment.
Distinguish between gray matter and white matter.
Gray matter consists of unmyelinated axons, cell bodies, and dendrites; White matter consists of myelinated axons.
Explain nerves in CNS and PNS.
CNS: clusters of neuron cell bodies are nuclei; bundles of myelinated axons are nerve tracts. PNS: clusters of cell bodies are ganglia; bundles of axons are nerves.
Define resting membrane potential.
The charge difference inside and outside the plasma membrane in an unstimulated cell.
How is resting membrane potential created and maintained?
Through permeability characteristics of membranes and differences in ion concentrations (more permeable to K+).
What processes can change the resting membrane potential?
Depolarization (inside becomes more positive), Hyperpolarization (inside becomes more negative).
List the three phases of neuron communication.
Generation of action potentials, action potential propagation along the axon, communication with a target cell at the synapse.
Describe the characteristics of a graded potential.
Small change in membrane potential localized to one area; can be depolarizing or hyperpolarizing.
How is an action potential created?
When graded potential reaches a threshold, followed by depolarization, repolarization, afterpotential, and return to resting potential.
How is an action potential propagated?
Depolarization spreads down the axon, triggering more sodium channels to open.
Discuss the all-or-none principle as it applies to action potentials.
An action potential occurs if the stimulus is greater than threshold; it is either produced or not.
Explain the characteristics and purpose of the refractory period.
Period following stimulation where tissue fails to respond to further stimuli; includes absolute and relative refractory periods.
What factors determine action potential frequency?
Subthreshold, threshold, submaximal, maximal, and supramaximal stimuli affect action potential frequency.
Describe the effect of myelination on the speed of action potential propagation.
Action potentials are conducted more rapidly in myelinated axons due to nodes of Ranvier.
What other factors affect the speed of action potential conduction?
Thickness of myelin sheath and diameter of axon.
Describe the general structure and function of a synapse.
Presynaptic neuron releases neurotransmitters; synaptic vesicles store neurotransmitters; synaptic cleft is the space between neurons; postsynaptic neuron contains receptors.
