Nervous system Flashcards
Master control and communication system.
3 overlapping functions;
1. sensory receptors monitor changes inside and outside the body.
2. processes and interprets sensory input
3. dictates a response by activating effector organs.
Nervous system
What changes detect inside or outside the body
stimulus
When information is gathered by receptors
sensory input
interpreting input
integration
the response
motor output
- Composed of brain and spinal cord.
- integrating and command center
Central nervous system
- Nerves branched from brain and spinal cord (cranial and spinal nerves)
- links all regions of body to CNS
Peripheral Nervous system
clusters of neuronal cell bodies
ganglia
Afferent signals picked up by sensor receptors
sensory
efferent signals carried away from CNS.
Also innervate muscles and glands
Motor
Sensory input and motor output divided according to regions they serve
Somatic body region
Visceral body region
4 main subdivisions of Somatic and visceral body regions
- somatic sensory
- visceral sensory
- somatic motor
- visceral motor
Receptors spread throughout outer tube of body ; touch, pain, vibration, pressure, temperature; general indicates “widespread”
Somatic sensory
Detect stretch in tendons and muscles
proprioceptive senses (somatic sensory)
Position and movement of body in space
body sense
Hearing, balance, vision, smell
special somatic senses
General senses; stretch, pain, temperature, nausea, and hunger.
widely felt in digestive and urinary tracts and reproductive organs.
Visceral sensory
Taste and smell
special visceral senses
General ; signals contraction of skeletal muscles
under our voluntary control
often called “voluntary nervous system”
Somatic Motor
- Regulates the contractions of smooth and cardiac muscle.
- makes up autonomic nervous system.
- often called “involuntary nervous system”
Visceral motor
Cells are densely packed and interwined.
2 main cell types
-neurons and support cells
Nervous Tissue
transmits electrical signals
neurons
- neuroglia cells in CNS
- nonexcitable
- surround and wrap neurons
Support cells
Basic structural unit of the nervous system.
- specialized cells conduct electrical impulses along the plasma membrane
- nerve impulse (action potential)
The neuron
Longevity, do not divide, high metabolic rate
special characteristics of neurons
can live and function for a lifetime
longevity
fetal neurons lose their ability to undergo mitosis; neural stem cells are an exception
do not divide
require abundant oxygen and glucose
-neurons die within 5 mins without oxygen
high metabolic rate
Size of cell body varies from 5 to 140 micrometers
-contains usual organelles plus other structures
cell body
- bundles of intermediate filaments
- forms a network between chromatophilic bodies
neurofibrils
- neuronal cell bodies located in the CNS
2. Neuronal cell bodies in PNS
- Cell body
2. Ganglia
- Branches from the cell body
- transmit electrical signals toward the cell body
Dendrites
extend only into the basal part of dendrites and to the base of the axon hillock
-functions as receptive sites for receiving signals from other neurons
Chromatophilic bodies
- -Neurons has only one
- impulse generator and conductor
- transmits impulses away from cell body
- chromatophilic bodies are absent
- no protein synthesis in axon
- Neurofilaments, actin microfilaments, and microtubules… - )provide strength and aids in transport of substances to and from the cell body
- Axons
2. Axonal transport
multiple branches at end of axon
terminal arboration
end in knobs
terminal boutons
- generated at the initial segment of the axon
- conducted along the axon to the terminal boutons
nerve impulses
released from vesicles at the terminal boutons
neurotransmitters
- Site at which neurons communicate
- information passed through chemical messengers
- – some info transmitted electrically through gap junctions
synapses
Presynaptic neuron
postsynaptic neuron
Synaptic vesicles
synaptic cleft
4 synapses
conducts signal toward a synapse
presynaptic neuron
transmits electrical activity away from a synapse
postsynaptic neuron
Axondendritic
Axosomatic
2 types of synapse
Between axon terminals of one neuron and dendrites of another
axodendritic
between axons and neuronal cell bodies
axosomatic
On presynaptic side
- membrane bound sacs containing neurotransmitters
- mitochondria abundant in axon terminals
synaptic vesicles
separates the plasma membrane of the 2 neurons
synaptic cleft
4 in CNS and 2 in PNS
- provide supportive functions for neurons
- cover non synaptic regions of the neurons
6 types of neuroglia
most cells have branching processes and a central cell body
outnumbers neurons 10 to 1
make up half the mass of the brain
can divide throughout life
4 types ; astrocytes, microglia, ependymal cells and oligodendrocytes
neuroglia in the CNS
most abundant glial cell type
- sense when neurons release glutamate
- extract blood sugar from capillaries for energy
- take up and release ions to control environment around neurons
- produce molecules necessary for neuronal growth
- propagate calcium signals involved with memory
Astrocytes (CNS)
Smallest and least abundant glial cell
- phagocytes ; macrophages of the CNS
- engulf invading microorganisms and dead neurons
- derive from blood cells called monocytes
- migrate to CNS during embryonic and fetal periods
Microglia
Line the central cavity of the spinal cord and brain
-bear cilia - helps circulate the cerebrospinal fluid
ependymal cells
few branches
- wrap their cell processes around axons in the CNS
- produce myelin sheaths in the CNS
oligodendrocytes
2 types; satellite cells and Schwann cells
Neuroglia in the PNS
Surround neuron cell bodies within ganglia
satellite cells
surround axons in the PNS
-forms myelin sheath around axons of the PNS
Schwann cells
