Nerves Unit 4 Flashcards
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
What is a synapse?
Connection between a neuron and its target (synaptic cleft)
Targets: Neuron, Muscle, or Gland
What happens during neurotransmitter release?
Ca2+ enters, causing synaptic vesicles to fuse w/the membrane
What are excitatory postsynaptic potentials (EPSPs)?
Cell is more likely to fire (depolarize) due to Na+ influx
What are inhibitory postsynaptic potentials (IPSPs)?
Postsynaptic cell is less likely to fire (hyperpolarize) due to Cl- influx or K+ efflux
What is temporal summation?
Occurs when a single synapse receives many signals in a short period of time
What is convergence and divergence in neural signaling?
Convergence - Many inputs to one cell leading to integration
Divergence - one cell passes info to many cells
What is multiple sclerosis?
Autoimmune disease causing demyelination
Risk groups - Ages 20-40, more women than men
Symptoms - trouble w/muscle coordination and numbness, vision, memory
What is ALS (Amyotrophic Lateral Sclerosis)?
Rapidly progressing disease that kills the motor neurons
Risk groups - men over 40
Symptoms - loss of muscle control
What is cerebral palsy (CP)?
Congenital disorder affecting muscle movement control
Risk groups - age 3 and older
Symptoms - lack of muscle control
What is spina bifida?
Neural tube defect affecting spinal cord development during the first trimester
Risk groups - Obese and diabetic pregnant women
Symptoms - paralysis in legs, bladder control issues
What are Schwann Cells?
Glial Cells in PNS
Make myeline sheath in PNS and insulate action potentials
Each axon has several Schwann cells
One axon per Schwann cell
What are Satellite Cells?
Glial Cells in PNS
Similar Function to Astrocytes
Surround neuron cell bodies
Barrier cells
What are Nodes of Ranvier?
Gaps in the myelin sheath where axon is exposed
Allows for saltatory conduction
What is Myelin Sheath?
Insulating layer around an axon
What are insulators?
Substances w/high resistance
Myelin sheath
What are conductors?
Substances w/low resistance
Cytoplasm
What is repolarization?
Going from postive to negative, towards the resting potential
What is a graded potential?
A potential that varies in magnitude
What is a decremental potential?
Potential that gets weaker the farther they spread
What is the Na+ to K+ ratio when returning to the resting potential?
3Na+ / 2K+
What is Spatial Summation?
Occurs when single synapse receives signals from many presynaptic cells
What is Fibromyalgia?
Disorder causing muscle pain
Risk groups - middle aged women
Symptoms - tender skin, headaches, sleep disorder, memory issues, numbness of hands and feet
