Nervous System Flashcards
1
Q
Central Nervous System
A
- made up of the brain and spinal cord
- integration and command center of nervous system
- receives sensory signals, interprets them and dictates motor response to them
2
Q
Afferent Signals
A
AKA sensory signals
- signals picked up and carried by PNS to CNS
3
Q
Peripheral Nervous System
A
- all nervous tissue outside the CNS
- made up of nerves and ganglia (clusters of neuron cell bodies)
- serve as communication lines linking body to CNS
4
Q
Efferent Signals
A
AKA Motor signals
- carried away from the CNS to effector organs, such as muscles and glands
5
Q
sensory input
A
information gathered by the nervous system
6
Q
integration
A
processing and interpretation of sensory input by the CNS
7
Q
motor output
A
the actions performed by effector organs upon receiving an efferent signal
8
Q
Subdivisions of the PNS
A
Sensory (Afferent) Division
- Somatic Sensory Receptors - outer, ie skin
- Visceral Sensory Receptors - visceral organs
Motor (Efferent) Division
- Somatic Nervous System - innervation of skeletal muscle, etc.
- Autonomic Nervous System - smooth/cardiac muscle and glands
9
Q
Somatic Sensory Perception Divisions
A
General Senses (widespread receptors)
- temperature, pain, pressure, touch (via skin)
- proprioception (joint position, postural tension, balance)
Special Senses (localized receptors)
- Smell
- Taste
- Vision
- Equilibrium & hearing
10
Q
Sympathetic Division of Autonomic Nervous System
A
- readies the body for activity
- “fight or flight”
11
Q
Parasympathetic Division of Autonomic Nervous System
A
- conserves energy and promotes digestion
- “rest and digest”
12
Q
Neurons
A
- basic structural unit of nervous system that conducts electrical impulses along its plasma membrane
- each neuron can live and function for the entire lifetime of the organism
- does not undergo mitosis
- high metabolic rate
13
Q
Neuron Properties
A
- Excitability - responds to changes in body and environment
- Conductivity - produce eletrical signals
- Secretion - releases neurotransmitters at synapses when eletrical signal reaches them
14
Q
purple structure at left containing nucleus
A
Neuron Cell Body (AKA Soma/Perikaryon)
- contains nucleus/cytoplasm
- has the usual organelles as well as specialized neuronal organelles (Nissel granules, Neurofibrils)
15
Q
Branched purple structures coming off cell body at left
A
Dendrites
- shorter than axon, but much branching
- receive signals and transmit them to cell body
16
Q
long thing cytoplasmic extension extending rightward from cell body through the yellow structures
A
Axon
- one per neuron
- Sends signals away from cell body
17
Q
Nissl Granules
A
AKA Nissl bodies
- rER and free ribosomes within neuron cell bodies
- stain densely on microscopic slides
18
Q
Neurofibrils
A
- bundles of microfilaments within neurons
- similar to structure of myofibrils within muscle cells
19
Q
Ganglia
A
clusters of neuron cell bodies outside the CNS, along PNS nerves
20
Q
cone-shaped region of cell body where it meets the axon
A
Axon Hillock
21
Q
branched ends of axon on the right
A
Telodendria
- AKA axon terminals or terminal branches
- end in synaptic knobs/bulbs at dendrites of another neuron, motor end plate, etc.
22
Q
spaces between the yellow structures on the axon
A
Nodes of Ranvier
- neurofibril nodes
23
Q
yellow cells surrounding the axon
A
Schwann cells
AKA neurolemmocytes
- form myelin sheath around axons in PNS only
24
Q
the cells that appear as small dots here amongst the neurons
A
Neuroglial Cells (or Neuroglia)
- outnumber neurons ~10 to 1
- insulate and support neurons
- branching processes and central cell body
25
Types of Neuroglial Cells
**CNS**
* **Astrocytes** - star-shaped, blood vessel connections
* **Microglia** - smallest, least abundant, phagocytes
* **Ependymal Cells** - CS fluid producers, ciliated
* **Oligodendrocytes** - myelination in CNS
**PNS**
* **Satellite Cells** - surround neurons in ganglia
* **Schwann Cells** - myelination in PNS
26
Yellow cell here connecting capillary to neuron
**Astrocyte**
- most abundant neuroglia in CNS
- star-shaped
- connect blood vessels to neurons
- contribute to BBB
- regulate ion balance and brain tissue fluid
- take up neurotransmitters from synapses
- replace damaged neurons
27
phagocytotic glial cell
**Microglia**
- smallest, least abundant CNS neuroglia
- engulfs invading microorganisms and dead neurons
- derived from monocytes
28
cuboidal, ciliated CNS neuroglia shown here as row of darker cells
**Ependymal Cell**
- line brain and spinal cord cavities
- produce **cerebrospinal fluid**
- ciliated to help circulate fluid
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round central structure
**oligodendrocyte**
- CNS neuroglial cell with few branches
- one cell myelinates multiple axons of CNS
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unlabeled structures surrounding the neuron body
**Satellite Cells**
- surround neuron bodies within ganglia of the PNS
31
Protective lipoprotein around axons
Myelin
- 20% protein, 80% lipid
- forms **myelin sheath**, concentric layers of plasma membrane of supporting cells (Schwann in PNS, Oligodendrocytes in CNS)
- insulates axon and increases speed of conduction
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cytoplasm within the axon of a neuron
Axoplasm
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Plasma membrane of an axon
Axolemma
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Outermost layer of Schwann cells around axons
Neurilemma
- outermost layer where nucleus of Schwann cell resides
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Unmyelinated Neurons
- thick axons are myelinated
- thin axons are unmyelinated, meaning surrounded and supported by Schwann cells, but not wrapped
36
What kind of neuron?
**Multipolar**
- more than 2 processes, many dendrites & 1 axon
- muscle innervation
37
What kind of neuron?
**Bipolar**
- 2 processes, dendrites on one, axon on other
- rare neurons in sensory organs (ex: retina)
38
What kind of neuron?
**unipolar neuron**
- pseudounipolar
- has one short single process connecting the body to the receptive and transmissive endings of the axon
39
Function Classification of Neurons
1. **Sensory (afferent) Neurons** - detect changes in body and environment
2. **Motor (efferent) Neurons** - send signals to muscles and glands (effectors)
3. **Interneurons (association neurons)** - between sensory and motor (CNS only), make up 99% of neurons, process, store and retrieve info
40
CT around each nerve fiber (axon)
Endoneurium
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dense irregular CT around each nerve fascicle
Perineurium
42
dense irregular CT around entire nerve, binding fascicles
epineurium
43
nerve fascicles
a group of nerve fibers (axons) bound into bundles, surrounded by perineurium
44
sites at which neurons communicate
synapse
- signals pass in one direction only
45
cell that conducts a signal toward a synapse
presynaptic neuron
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cell that transmits a signal away from a synapse
postsynaptic neuron
47
types of synapses
**Axosomatic** - axon to cell body
**Axodendritic** - axon to dendrites
**Axoaxonic** - axon to axon, signal acts on axon terminals only, regulating synapse function
48
functional junction between a neuron and another cell in which communication is transmitted via ions passing through gap junctions
electrical synapse
49
junction between a neuron and another cell in which neurotransmitters carry a signal across a space between the cells
chemical synapse
50
mebrane-bound sacs in a presynaptic neuron that contain neurotransmitters
synaptic vesicles
51
space between the axon terminal of one neuron and the dendrites of another
synaptic cleft
52
neuronal regeneration overview
- None in CNS
- Axons regenerate slowly (1-5 mm/day) in PNS, but not cell bodies
Dependent on:
* extent of damage
* Schwann cells' secretion of _Nerve Growth Factor_
* distance from damage to organ being innervated (closer = better)
53
Neuronal Regeneration Steps
1. axon is severed
2. proximal end of severed axon seals off/swells, distal end degenerates
3. distal Schwann cells form "regeneration tube"
4. axon regenerates and threads through tube
5. effector is reinnervated
54
Rapid, autonomic motor response to stimuli
Reflex
- predictable and involuntary
55
A simple chain of neurons responsible for a reflex
reflex arc
- made up of:
* **Receptor** - takes in stimulus
* **Sensory neuron** - transmits afferent signal
* **Integration Center** - 1+ synapses in CNS
* **Motor neuron** - conducts efferent signal
* **Effector** - muscle/gland which acts
56
Two Types of Reflexes
**Monosynaptic Reflex:**
* fastest
* contains no CNS interneurons
* less common
**Polysynaptic Reflex:**
* most common
* contains at least 1 CNS interneuron
