nervous sytem Flashcards
What is the total body weight of the nervous system?
3 % of total body weight with mass of only 2 kg
two divisions:
CNS AND PNS
Central Nervous Tissue
Peripheral Nervous tissue
Neurology
deals with normal functioning and disorders of the nervous tissue
Neurologist
a physician who diagnoses and treats disorders of the nervous system
What does CNS consist of it?
Brain and spinal cord
Brain- located in skull
85 billion neurons
Spinal cord
connected to the brain through the foramen magnum of the occipital bone and encircled by the bones of the vertebral column
100 million neuron
PNS consist of
all nervous tissue outside CNS
Components of the PNS
NERVES AND SENSORY RECEPTORS
Nerve is
A bundle of 100-1000 axons associated with connective tissue and blood vessels that lie outside of the brain and spinal cord
How many cranial nerves are there and where do they emerge from
12
from the brain
How many are there spinal nerves and where they emerge from
31
spinal cord
Sensory receptors refers to
structure of the nervous system that monitor changes in external or internal environment
examples of sensory receptors
touch receptors in skin
photoreceptors in the eye
olfactory receptors in nose
How is PNS divided?
Sensory and motor division
What is sensory division?
What is the other name of the sensory division?
other name is an afferent division
conveys input into the CNS FROM SENSORY RECEPTORS IN the BODY
This division provides the CNS with sensory information about somatic senses and special senses
What are somatic senses?
tacticle, thermal, pain and proprioceptive sensations
What are the special sense?
Smell, taste, vision, hearing and equilibrium
What is motor or efferent division of the PNS?
conveys output from CNS to effectors (muscles and glands
How is the motor or efferent divided further?
The division is further divided into somatic nervous system and an autonomic nervous system
What is the somatic nervous system SNS?
conveys output from CNS to skeleton muscles
What kind of motor responses are of somatic nervous system?
they are consciously controlled, the action of this part of PNS is voluntary
What is autonomic nervous system ANS?
conveys output from the CNS to smooth muscles, cardiac muscles and glands
What kind of motor responses are?
Motor responses are not normally under conscious control the action of the ANS is involuntary
What are the branches of the ANS?
Sympathetic division and parasympathetic division
Effectors receive innervation from both sympathetic division and parasympathetic division and two division have opposite actions
Neurons from from the sympathetic part increases heart rate and nervous of the parasympathetic division slow down
Parasympathertic division part takes care:
rest and digest activities
symphatetic division h
helps support exercise or emergency actions so called fight or flight response
what is third branch of the ANS
enteric plexuses
the activity og what is enteric plexuses
extensive network of over 100 million neuron confined to the wall of the digestive canal
What does enteric plexuses regulates?
the activity of the smooth muscles and glands of the digestive canal
Three basic functions
Sensory function
Integrative function
Motor function
Sensory function
Sensory receptors detect internal stimuli such as increased blood pressure or external stimuli.
This sensory information is carried into the brain and spinal cord through cranial and spinal nerves
Integrative functions
The nervous system processes sensory information by analyzing it and making decisions for appropriate responses and acitivity know as integration
Motor function
Once sensory information is integrated, the nervous system may elicit an appropriate motor response by activating effectors’ muscles and glands through cranial and spinal nerves.
Stimulation of the effectors causes muscle to contract and gland to secret
Two types of cell of nervous tissu
neurons and neuroaglia
neurons
forms the complex processing networks within the brain and spinal cord and connects all regions of the body to the brain and spinal cord
Neurons
highly specialized cells
capable reaching great lengths and making intricate connections with other cells
neuron
provide most of the unique functions of the nervous system such as sensing, thinking, remembering, controlling muscle activity and regulating glandular secretions
neuron
As result of their specialization most neurons have lost ability undergo mitotic division
neuroglia
support nourish and protect neurons and maintain interstitial fluid that bathes them
neuroglia
Continue to divide throughout an individual lifetime
What does neuron poses?
electrical excitability
what is electrical excitability
ability to respond to stimulus and convert it into an action potential
stimulus
any change in the environment that is strong enough to initiate a nerve impulse
nerve impulse or action potential
an electrical signal that propagates (travel) along the surface of the membrane of a neuron
Why does it begin and travel ?
due to the movements of the ion=s such as sodium and potassium between interstitial fluid and inside the neuron through specific ion channels in its plasma membrane
how does nerve impulse travel?
rapidly and at constant strength
what kind of the neurons are there
tiny-propagates nerve impulses over a short distance within CNS
others are the longest cells in the body
what are 3 parts of neuron
the cell body
dendrites
an axon
What is the other name for the cell body?
perikaryon
soma
Cell body contains a nucleus surrounded by cytoplasm that include typical cellular organelles
lysosomes
mitochondria
golgi complex
nissl bodies
Prominent clusters of the rough endoplasmic reticulum to synthesise proteins to replace cellular components, material for the growth of neurons and to regenerate damaged axons in ONS
what does cytoskeleton include
neurofibrils= composed of bundles of intermediate filaments that provide cell shape and support
microtubules assist in moving materials between the cell body and axons
what is lipofuscin
Aging neurons contains lipofuscin, a pigment that occurs as clumps of yellowish-brown granules in the cytoplasm
what is lipofuscin
a product of neuronal lysosome that accumulates as neuron ages but does not harm the neuron
plasma membrane of neuronal cell body
ranges from smooth to very bumpy
why is plasma membrane bumpy?
caused by many small projections of plasma membrane SOMATIC SPINES
wHAT IS SOMATIC SPINES
Receptor sites that bind chemical messengers from other neuron
what does the somatic spines do
increases the surfaces area for interactions with other neuron
ganglion
a collection of neurnal cell bodies outside the CNS
Nerve fiber
General term for any neuronal process (extension) that emerges from the cell body of a neuron.
Most neurons have two kinds of processes, multiple dendrites and a single axon
dendrites
receiving or input portion of the neuron
-short, tapering and highly branched
-form a tree-shaped branch array of processes extending from the cell body
Dendritic spines
The plasma membrane of dendritic contains numerous receptor sites for binding chemical messenger from other neurons
Axon
The long thin cylindrical projection that often joins to the cell body at a cone-shaped elevation called the axon hillock.
initial segments
the part of the axon closest to the axon hillock
where does the nerve impulse arise
AT THE JUNCTION OF THE AXON HILLOCK AND INITIAL SEGMENTS
What is the name of the area at junction of the axon hillock and initial segments where nerve impulse arise
trigger zone
components of axon
MITOCHONDRIA, MICROTUBULES
NEUROFIBRILS
What doesnt axon has
rough endoplasmic reticulum is not present so protein synthesis does not occur
the name of the cytoplasm of the axon
axonplasm
wha is asoplasma surronded by?
plasma membrane called axolemma
axon collaterals
side branches along the length of the axon on the right side to the axon
axon terminal or axon telodendria
The axon and its collaterals end by by dividing into many fine processes axon terminal terminals
What is the name of the site of communication between two neurons or between a neuron and effector cell
synapse
what is synaptic end bulb and varicosities
The tips of some axon terminals swell into the bulb-shaped structure, while others exhibit a string of swollen bumps called varicosities
what do synaptic end bulbs and varicosities contain
Many tiny membrane-enclosed sacs called synaptic vesicles that store chemical called a neurotransmitter
what is a neurotransmitter
a molecule released from synaptic vesicles that excite or inhibits another neuron, muscle fibres or gland cells
The two types of transport systems carry materials from the cell body to the axon terminal and back because some substances synthesized or recycled in the neuronal cell body are needed in the axon or at the axon terminal
Slow axonal transport - it conveys axoplasm one way only from the cell body towards the axonal terminal.
fast axonal transport-capable moving materials a distance of 200-400 mm per day, uses proteins that function as a motor to move materials along the surface of microtubules of the neuron’s cytoskeleton
-it moves material in both directions, away from and towards the cell body
anterograde direction
fast axonal transport that occur in foward direction moves organelles and synaptic vesicles from cell body to axon terminal
retrograde
Fast axonal transport that occurs backward direction moves membrane vesicles and other cellular materials from the axon terminals to the cell body to be degraded or recycled
substances that enter the neuron at the axon terminals are also moved to the cell body by fast retrograde transports
Ex trophic chemicals such as nerve growth factor and harmful agents such as tetanus toxin and viruses that cause rabies, herpes simplex and polio
