Nervous Tissue Flashcards
three main functions of the nervous system
-senses changes within the body and outside the body
-interprets the sensory information that is recieved
-responds to the sensory information by initiaing movements or secretions
2 types of cells of nervous tissues
-neurons for intercellular communication
-nueroglia (glial cells) for survival and preservation of structure of nervous tissue
central nervous system
-brain and spinal cord
-connective tissue, nervous tissue and blood vessels
-functioons to process and corodinate sensory data from inside and outside the body
-motor commands control activities of peripheral organs
-higher functions of brain include intelligence memory learning and emotion
peripheral nervous system
-includes nervous tissue outside CNS and ENS
-delivers sensory information to CNS
-carries motor commans to peripehL TISSUE
nerves
-bundles of axons with connective tissues and blood vessels
-carry sensory information and motor commands
-cranial nerves conenct to brain
-spinal nerves attach to spinal cord
functional division of PNS
-afferent and efferent, receptors, effectors
afferent division of the nervous system
-carries sensory information
-from receptors in peripheral tissues and organs to CNS
efferent division of nervous system
-carries motor commans from CNS to muscles glands and adipose tissue
receptors
-detect change sor responds to stimuli
-may be nuerons or specialized cells
-may be single cells or complex sensory organs
effectors
-target organs that respond to motor commands
efferent division of PNS
-somatic nervous system
-autonomic nervous system
somatic nervous system
-controls skeletal muscle contractions
-both voluntary and involuntary reflexes
autonomic nervous system
-control subconscous actions contractions of smooth and cardiac muscle and glandular secretions
-sympathetic has a stimulating effect
-parasympathetic has a relaxing effect
overview of the nervous system
nuerons
-basic functional unit of the nervous sytem
-send and recieve signals
-function in communication information processing and control
cell body
-AKA soma
-perikaryon (cytoplasm) surrounding the nucleus
-mitochondria produces energy
-RER and ribosomes for synthesizing proteins
dendrities
-short and highly branched processes extending from cell body
dendritic spines
-fine processes on dendrities
-recieve information from other nuerons and conduct info into cell body
-80-90% of neuron surface area
-some nuerons have only one dendrite and some has thousands
Axons
-single long cytoplasmic processes
-propagates electrical signals
-carries the nerve signals away from the cell body
-can be a few mm or as long as a meter
axolemma
-plasma membrane of the axon
-covers the axoplasm
initial segment
base of the axon
axon hillcock
-thick region that ataches inital segment to cell body
axon photo
collaterals
-branches of the axon
-side branches that enable single axon to communicate with several other cells
telodendria
-fine extensions of distal axon
axon terminals
-synaptic terminals
-tip of telodendria
structural classification of nuerons
-anaxonic nuerons
-unipolar nuerons
-bipolar nuerons
-multipolar nuerons
bipolar nuerons
-small and rare
-one dendrite and one axon
-found in special sense organs liek sight smell and hearing
anaxonic nuerons
-anaxonic nuerons
-small
-all cell processes look similar
-found in brain and special sense organs
unipolar nuerons
-pseudounipolar nuerons
-axon and dendrites are fused
-cell body to one side
-most sensory nuerons of PNS
multipolar nuerons
-have one long axon and two or more dendrtes
-common in the CNS
-all motor nuerons that control skeletal muscles
structural photo of nueron types
functional classfications of nuerons
-sensory nuerons
-motor nuerons
-internuerons
sensory nuerons
-detect heat cold che icals and transmit info up to the CNS
-unipolar
-cell bodies grouped in sensory ganglia
-processes extend from sensory receptors to CNS
-somatic sensory nuerons (monitor external environment) and visceral sensory nuerons(monitor internal environment)
interoreceptors
-monitor internal systems
-internal senses
exteroceptors
-monitor external environment
-complex senses
proprioceptors
-monitor position and movement of skeletal muscles
motor nuerons
-efferent nuerons
-carry instructions from CNS to peripheral effectors via efferent fibres
-exit CNS and have motor effect
somatic motor nuerons of SNS
-innervate skeletal muscles
visceral motor nuerons
-innervate all other peripheral effectors
-smooth and cardiac muscles glands adipose tissue
internuerons
-most are in brain and spinal ord
-located between sensory and motor nuerons
-responsible for distribution of sensory information, coordination of motor activity
-involved in higher functions like memory planning and learning
nueroglia
-support and protect nuerons
-make up half the volume of the nervous system
-many types of CNS and PNS
types of nuerglia in the CNS
-astrocytes
-epindymal cells
-oligodendrocytes
-microglia
astrocytes
-have large cell bodies with many processes
-function: maintain BBB create 3D dimesntional framework for CNS, repair damaged nervous tissue, guide nueron development, control interstitial environment
epensymal cells
-form epithelium that lines central canal of spinal cord and ventricles of the brain
-produce and monitor CSF
-have cilia that help circulate CSF
oligodendrocytes
-have small cell bodies with few processes
-many cooperate to form a myelin sheath
-myelin insulates myelinated axons
-increase speed of action potentials
-make nerve appear white
can myelinate segments of many axons
internodes
myelinated segments of axon
nodes/nodes of ranvier
-lie between internodes where axons may branch
white matter
-regions of CNS with many myelinated axons
gray matter of CNS
-contains unmyelinated axons, nueron cell bodies and dendrites
microglia
-smallesr and leaast numerous nueroglia
-have many fine branches processes
-migrate through nervous tissue
-clean up cellular debris, wastes and pathogens
two types of nueroglica of the PNS
-insulate nueronal cell bodies and most axons
-satellite cells and schwann cells
satellite cells
-surround nueron cell bodies in ganglia
-regulate o2 and co2 nutrient and nerotransmitter levels around nuerons in ganglia
schwann cells
-surround all axons in PNS; responsible for myelination of peripheral axons; participate in repair process after injury
satellite cells
-surround ganglia
-regulate interstitial fluid around nuerons
schwann cells
-nuerolemmocytes
-form myelin sheath or indented folds of plasma membrane around axons
-nuerolemma is the outer surface of a scwann cell
- a myelianting schwann cell sheaths only one axon and many schwann cells sheather entire axon
schwann cell
wallerian degeneration
-axon distal to injury degenerates
-schwann cells form path for new growth and wrap around new axon
never regeneration in CNS
-limited by astrocytes in CNS
-produce scar tissue
-release chemicals that block regrowth
nerve generation CNS steps
-fragmentation of axon and myelin occurs in distal stump
-schwann cells form cord, grow into cut, and unite
-macrophages engulf degenerating axon and myelin
-axon sends buds into network of schwann cells and then starts growing along cord of schwann cells
-axon continues to grwo into distal stump and is enclosed by schwann cells
synapse
-specialized site where a nueron communicates with another cell
-presynaptic nueron sends the message
-post synaptic nueron recieves the message
types of synapses
-electrical synapses - direct physical contact between cells
-chemical synapses - signal transmitted across a gap by nuerotransmitteers
-chemical synapses
chemical synapses
-most common
-only type of synapse between nuerons and other cells
-cells are seperated by synaptic cleft
-pre synaptic cell sends the messgae
-post synaptic cell recieves the message
types of chemical
-nueromuscular junction - synapse between nueron and skeletal muscle cell
-nueroglandular junction - synapse between nueron and gland cell
nuerotransmitters
-chemical messengers containe within synpptic vesicles in axon terminal of presynaptic cell
-affect receptors of post synaptic membrane
-broken down by enzymes
-reabsorbed and reasssembled by axon terminal
