nervous tissue 1&2 Flashcards
what is the main control over the bodys functions
the nervous system
the nervous system receives stimuli from the body and environment via
sensory receptors
nervous system processes info to initiate an
appropriate response
the nervous system receives, processes and sends info via
neurons
neurons are supported by
neuroglial cells
neurons maintain a _____ potential inside their plasma membrane
negative
Na+-K+ pump
neurons respond to stimuli with a wave of
depolarization
where do neurons transmit the stimulus to
muscles, glands and other neurons (synapses)
2 main components of nervous system
central nervous system and peripheral nervous system
central nervous system
- brain and spinal cord
- processing and command functions
peripheral nervous system
- all nervous tissue outside of CNS
- relays sensory info to CNS
- directs commands from CNS to the effector organs
PNS consists of 2 divisions
afferent (towards CNS, SENSORY) and efferent (away from CNS, MOTOR)
afferent division of PNS
- towards CNS
- sensory pathway
- somatic sensory receptors
- visceral sensory receptors
efferent division of PNS
- away from CNS
- motor pathway
- somatic nervous system to skeletal muscle
- autonomic nervous system to viscera
autonomic nervous system consists of what two divisions
PNS –> efferent –> autonomic
- sympathetic (fight or flight)
- parasympathetic (rest and digest)
summary of 4 main divisions of the PNS
- general somatic afferent (sensory)
to CNS from receptors in skeletal muscle and skin; pressure and pain receptors - general visceral afferent (sensory)
to CNS from heart, GI tract, urinary and reproductive systems - general somatic efferent (motor)
from CNS to skeletal muscle - autonomic nervous system (motor)
sympathetic and parasympathetic, from CNS to viscera, secretory cells
general somatic afferent (sensory)
to CNS from receptors in skeletal muscle and skin; pressure and pain receptors
general visceral afferent (sensory)
to CNS from heart, GI tract, urinary and reproductive systems
general somatic efferent (motor)
from CNS to skeletal muscle
neurons consist of what 3 parts
- cell body (perikaryon, soma)
- one axon
- one or more dendrite
cell body of neuron nucelus
large round and centrally placed with a prominent nucleolus
cell body of neuron; cytoplasm has a large amount of ____ and numerous ____
rER (Nissl substance/ bodies)
mitochondria
in cell body of neuron, golgi apparatus is responsible for packaging
neurotransmitters
most neuron cells bodies are located in the
CNS
sensory neurons (GSA, GVA) and terminal effector neurons of ANS have cell bodies in
peripheral ganglia; aggregates of cell bodies
dendrites are
processes which extend from cell body; may be one or many
dendrites form connections with axons of other neurons called a
synapse
sites of synapse are studded with
dendritic spines (gemmules)
nerve impulses travel along ____ to _____
dendrites to cell body
the axon is a
single, long cytoplasmic process aka the nerve fiber
the plasma membrane of axon is called the
axolemma
the axons may give rise to branches called
collateral branches; right angles to axons
the axon branches terminate as fine branches called the
telodendrons,
which end as synaptic terminals (form synapses w other neurons or cells)
nerve impulses travel along axon ____ from cell body
away
axon may be insulated in a
myelin sheath
multipolar neurons
- one axon
- many dendrites
- common; motor neurons
bipolar neurons
- one axon
- one dendrite
- rare; receptors for smell, sight, balance
unipolar (pseudo-unipolar)
- one axon that arises from a stem from cell body
- several dendrites
- common; sensory neurons
name 4 neuroglia found within CNS
- astrocytes
- oligodendrocytes
- ependymal cells
- mircroglia
name 2 neuroglia of PNS
- shwann cells
- satellite cells
atsrocytes
- neuroglia of CNS
- star shaped with branching processes
- pale nuclei
- cytoplasm requires special staining methods
- metabolic exchange between neurons & blood
- structural support to neurons
oligodendrocytes
- neuroglia of CNS
- dense nuclei
- cytoplasm requires special staining
- congregate around cell bodies
- produce myelin around axons in the CNS
ependymal cells
- neuroglia of CNS
- cuboidal – columnar epithelial cells
- line the fluid-filled cavities of the brain & spinal cord
- may have cilia or microvilli
microglia
- neuroglia of CNS
- small cells, few in number
- difficult to see with light microscopy
- develop into large, amoeboid phagocytes in response to tissue damage
schwann cells
- neuroglia of PNS
- surround axons in the PNS
- produce myelin
satellite cells
- neuroglia of PNS
- surround cell bodies within ganglia
- provide physical & metabolic support
in PNS, all axons are enveloped by ____ which form ____
schwann cells
myelin
small diameter axons are enveloped only in
Schwann cell cytoplasm, unmyelinated
myelinated nerves include
cranial nerves and spinal nerves
what is myelin
a fatty substance, modified plasma membrane, reduced protein and higher lipid content
myelin is ____ and so nervous tissue that contains a large proportion of myelinated fibers is referred to as _____
white
white matter
unmyelinated tissue appears as ____ and so is called _____
grey
grey matter
myelination function
provides insulation, inhibiting diffusion of nerve impulses
the segment of myelin produced by each schwann cell is called an
internode
between each internode (segment of myelin) is a _____ where schwann cells encase the axon but do not form a myelin sheath
node of ranvier
nerve impulses spread along the axon by jumping from
one node of ranvier to the next; saltatory conduction, allows for v rapid conduction of nerve impulses
describe process of myelination
- Schwann cells align themselves along an axon
- Tongue of cytoplasm folds around the axon
- wraps around many times
- Cytoplasm is excluded leaving only the plasma membrane of the
Schwann cell - These layers of plasma membrane fuse to form the myelin sheath
brain and spinal cord contain both
white and grey matter
grey matter
- neuron cell bodies
- axons
- majority unmyelinated
- neuroglia
- blood vessels
white matter
- axons
- majority myelinated
- neuroglia
- blood vessels
brain white/ grey matter
- grey on OUTSIDE
- white on INSIDE
spinal cord white/grey matter
- white on OUTSIDE
- grey on INSIDE
CNS protected by
bone; cranium and vertebrae
brain and spinal cord have fluid filled canals and ventricles lined by
what kind of fluid
ependymal cells
cerebrospinal fluid (CSF)
how many layers of connective tissue around spinal cord?
what are they?
collectively they are called
3:
dura mater,
arachnoid membrane,
pia mater
together called meninges
dura mater
- outer layer of connective tissue surrounding brain and spinal cord
- tough, fibroelastic connective tissue
arachnoid membrane
- middle layer of connective tissue surrounding brain and spinal cord
- fine, cobweb-like
- spaces filled with CSF
Pia mater
- inner layer of connective tissue surrounding brain and spinal cord
- very fine reticular and collagen fibers
- blood vessels
nerve fiber
- axon of neuron
- may be afferent or efferent
- surrounded by Schwann cell sheath
- may be myelinated or unmyelinated
- enclosed by reticular fibres = endoneurium
nerve fiber enclosed by reticular fibers called
endoneurium
fasciculus
- collection of fibres (axons)
- surrounded by connective tissue = perineurium
fascicules surrounded by connective tissue called
perineurium
nerve
- collection of fasciculi
- contains both afferent & efferent fibres
- blood vessels
- bound by connective tissue = epineurium
nerve fiber surrounded by
fasciculus surrounded by
nerve is surrounded by
endoneurium
perineurium
epineurium
ganglia
clusters of neuron cell bodies OUTSIDE of the CNS
what do ganglia contain? what is it surrounded by
- satellite cells, schwann cells, blood vessels, neurons
- surrounded by connective tissue which is continuous with the epineurium
craniospinal ganglia: where? what kind of fibers? what kind of neurons?
- close to brain and spinal cord
- afferent fibers (sensory)
- unipolar neurons
autonomic ganglia: where? what kind of fibers? what kind of neurons?
- may be free structures or within tissues
- efferent fibers (motor)
- multipolar neurons
nerve impulses cross from one neuron to another at the
synapse
passage of stimulus over the neuron/ synapse usually via
special synapses use direct
chemical transmitters
electrical transmission
most synapses are axo-_____
less comon are axo- _____ and axo-_____
axo-dendritic
axo-somatic and axo-axonic
a single neuron may have how many synapses
hundreds
synapses may be ____ or _____
excitatory or inhibitory
chemical transmission: transmitter substances (aka neurotransmitters) are produced by
pre-synaptic neuron
neurotransmitters are spread across gap between
what is this gap called
presynaptic and postsynaptic neurons
gap is called synaptic cleft
cytoplasm of pre-synaptic neuron contains
mitochondria and vesicles of neurotransmitters
neurotransmitters include
- acetylcholine
- adrenaline (epinephrine)
- noradrenaline (norepinephrine)
- serotonin
- gamma amino butyric acid (GABA)
in electrical transmission (as opposed to chemical) nerve impulses transmitted electrically without
neurotransmitters
in electrical transmission the pre & post synaptic membranes are in close apposition via
gap junctions
in electrical transmissions how do ions move in from pre to post synaptic membrane
ions pass from pre-synaptic membrane to post-synaptic membrane via channels in gap junctions
motor end plates aka neuromuscular junctions are
what kind of nerves
- specialized synaptic nerve endings
- general somatic efferent nerves (motor)
- skeletal muscle
in motor end plates one neuron can be involved with how many muscle fibers
several or several hundred
in motor end plates the acon terminates in a recess on
muscle cell
the axon of motor end plate is enclosed by
the basement membranes of muscle cell and Schwann cell ____
Schwann cell cytoplasm
fuse
in motor end plates the pre-synaptic neuron has _____
signalling is via _____
synaptic vesicles
neurotransmitters
in motor end plates the post synaptic membrane on the skeletal muscle is specialized with
deep folds; secondary synaptic clefts
sensory receptors may be
nerve endings (dendrites) or specialized cells
sensory receptors convert stimuli into
afferent nerve signals which pass on to CNS
sensory receptors:
free nerve endings
- many small terminal branches of dendrites
- loss of Schwann cell covering before termination
- temperature, touch, pain
sensory receptors: encapsulated endings
- terminal branches of neuron surrounded by a capsule of cells
- modify or amplify stimulus, maintain ionic environment
sensory receptors; lamellated endings
- layers of connective tissue cells
- pressure receptors
for sensory receptors which nerve endings involved in temp, touch and pain?
which involved with pressure?
which are involved with meissner’s corpuscle and touch?
free nerve endings (dendrites)
lamellated endings
encapsulated endings
nerves exit from spinal cord as
spinal nerves
spinal nerves contain what fibers (afferent or efferent)
both afferent and efferent
how are efferent and afferent fibers sorted in spinal cord
- dorsal root: afferent (sensory)
- ventral root; efferent (motor)
dorsal root of spinal nerves
afferent, sensory
ventral root of spinal nerves
efferent, motor
dorsal root (afferent, sensory) of spinal nerves contain sensory nerves of:
- general somatic afferent; from body
- general visceral afferent; from viscera
cell bodies of dorsal root are lodged in
what kind of neurons
- dorsal root ganglion near the spinal cord
- unipolar (pseudo-unipolar) neurons
once the neurons of the dorsal root are inside the spinal cord, they synapse with
- other afferent neurons (interneurons) and/ or
- directly with efferent neurons
ventral root (efferent motor) of spinal nerves contain
- general somatic efferent nerves; to skeletal muscle
- autonomic nervous system nerves; to viscera
cell bodies of ventral root are lodged in
grey matter of spinal cord
in the ventral root, general somatic efferent axons terminate on
skeletal muscle as motor end plates
in ventral root, autonomic nervous system axons synapse with a second neuron in an
autonomic ganglion within the tissue
pyramidal motor neurons
- GSE neurons
- ventral horn of spinal cord
- multipolar
- cell body pyramidal (!)
- dendrites receive synapses from sensory neurons
- axon terminates on skeletal muscle as a motor
end plate
sensory neurons
- GSA neurons
- dorsal root ganglia or cranial nerve ganglia
- unipolar (pseudo-unipolar)
- cell body round
- dendrites form sensory endings & axon
enters CNS
prukinje cells (type of neuron in the brain)
- cerebellum
- large, flask-shaped
- right up there with eosinophils
- multipolar
- elaborate dendritic tree
granule cells (type of neuron in the brain)
- cerebellum
- very small
- one axon that divides to make
contact with Purkinje dendrites - several dendrites
specialized cells and neurons: neurosensory cells
- located in the special sense organs
- some are true neurons
- rods & cones in retina
- olfactory cells
- others are cells adapted to transmit stimuli
to dendrites of sensory neuron - taste buds
- hair cells of inner ear
specialized cells and neurons:
neurosecretory cells
- release hormones rather than neurotransmitters
- neurosecretory cells of hypothalamus
- cells of adrenal medulla
Which of the following statements about the nervous system is INCORRECT?
A.
In the central and peripheral nervous systems, axons are myelinated by Schwann cells; unmyelinated axons are surrounded only by Schwann cell cytoplasm
B.
Ependymal cells are cuboidal or columnar epithelial cells, that may have cilia or microvilli, and that line the fluid-filled cavities of the brain and spinal cord
C.
In the spinal cord, the grey matter contains neuron cell bodies and axons, the majority of which are unmyelinated
D.
Ganglia are clusters of neuron cell bodies outside of the central nervous system, and may contain afferent or efferent neurons
A.
In the central and peripheral nervous systems, axons are myelinated by Schwann cells; unmyelinated axons are surrounded only by Schwann cell cytoplasm
Which of the following statements about synapses is INCORRECT?
A.
Synapses usually involve chemical transmitters but special synapses use direct electrical transmission
B.
Synapses are exclusively excitatory
C.
A single neuron may have hundreds of synapses
D.
Synapses may be axodendritic, axosomatic, or axoaxonic
B.
Synapses are exclusively excitatory
Which of the following statements about the central nervous system is INCORRECT?
A.
Spinal nerves contain both afferent and efferent fibres
B.
The dorsal root contains sensory nerves of the General Somatic Afferent and General Visceral Afferent pathways, with the cell bodies located in the dorsal root ganglion
C.
Purkinje cells are large, flask-shaped neurons located within the grey matter of the cerebrum
D.
Pyramidal motor neurons belong to the General Somatic Efferent pathway and are located in the grey matter of the ventral horn of the spinal cord
C.
Purkinje cells are large, flask-shaped neurons located within the grey matter of the cerebrum
Which of the following statements about the central nervous system is INCORRECT?
A.
Spinal nerves contain both afferent and efferent fibres
B.
The dorsal root contains sensory nerves of the General Somatic Afferent and General Visceral Afferent pathways, with the cell bodies located in the dorsal root ganglion
C.
Purkinje neurons are located within the grey matter of the cerebellum between the granular and molecular layers
D.
Pyramidal motor neurons belong to the General Somatic Efferent pathway and are located in the white matter of the ventral horn of the spinal cord
D.
Pyramidal motor neurons belong to the General Somatic Efferent pathway and are located in the white matter of the ventral horn of the spinal cord
