Nerves Unit 4 Flashcards
(46 cards)
What are the primary functions of the nervous system?
3 Functions
Receive Information
Process Information
Initiate Response
These functions involve receptors, integrators, and effectors.
What does the central nervous system (CNS) consist of?
Brain and spinal cord
What comprises the peripheral nervous system (PNS)?
Nerves and ganglia
Nerves are bundles of neuronal axons, while ganglia are collections of cell bodies.
What are the two functional divisions of the PNS?
- Sensory (afferent) division
- Motor (efferent) division
Sensory - receptors TO CNS
Motor - AWAY from CNS to effectors
What are the roles of the autonomic nervous system?
Controls effectors like cardiac muscle, smooth muscle, and glands
Somatic - skeletal muscle
It has sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) divisions.
What are neurons?
Cells that respond to stimuli with electrical activity and release neurotransmitters
What are glial cells?
Neuroglia
Support cells of the nervous system
What is the function of oligodendrocytes?
Glial Cells in CNS
Form myelin sheaths in CNS and insulate action potentials
What do astrocytes provide?
Glial Cells in CNS
Blood-brain barrier (BBB)
They protect CNS from blood-borne proteins, toxins, and cells.
What is the role of ependymal cells?
Glial Cells in CNS
Line cavities and produce cerebrospinal fluid (CSF)
What do microglia do?
Glial Cells in CNS
Specialized phagocytic white blood cells that clean debris and pathogens
What is the structure of a neuron?
- Cell body (soma)
- dendrites (branch extensions)
- axon (nerve fiber)
What is the function of the myelin sheath?
Produced by oligodendrocytes (CNS) or schwann cells (PNS)
Insulates the axon
What are the characteristics of neurons?
5 Characteristics
- Excitability
- Conductivity
- Secretion
- Amitotic
- Longevity
What are the three functional types of neurons?
What kinds of neurons are there?
- Sensory (afferent) neurons
- Interneurons (association)
- Motor (efferent) neurons
Afferent - coming in
Association - in-between
Efferent - Going Out
What are the 3 structural types of neurons?
- Multipolar - many dendrites, one axon, most common
- Bipolar - one dendrite, one axon
- Unipolar - no dendrites, one axon
Info moves in one direction
What is the resting membrane potential of neurons?
~ -70 mV
K (negative) concentrated inside
Na (positive) concentrated outside
What causes depolarization in neurons?
Na+ influx
What is hyperpolarization?
When the membrane potential becomes more negative than the resting potential
What is an action potential?
A brief reversal in the charge on the membrane that occurs at the trigger zone
What is the all-or-none rule in action potentials?
If ~-55mV, nothing happens
Once past ~-55mV, an action potential goes to completion and cannot be stopped
What are the phases of an action potential?
- Depolarization (positive, Na gates open and enter cell)
- Repolarization (negative, Na gates close, K gates open, K enters cell)
- Hyperpolarization
What is the refractory period?
Period of resistance to stimulation where no new action potential can be triggered
Absolute (no go) and Relative (very hard to go again)
What is saltatory conduction?
Myelinated Axons
Action potentials jump from node to node in myelinated axons, speeding up conduction
Na+ diffusion between nodes
