nervous tissue - anat

whats the nervous system

it is the control communications system of the body, it has functional divisions and structural divisions

what are the components of the structural division of nervous system

central nervous system: brain, spinal cord

peripheral nervous system:

cranial nerves: extend from the brain

spinal nerves: extend from spinal cord

ganglia: clusters of neuron cell bodies outside CNS

what are the components of the functional division of nervous system?

sensory input: afferent neuron, send signals toward the CNS 

integration: interneuron 

motor output: efferent neuron, send signals away from CNS 

whats the difference between somatic and autonomic NS ?

somatic nervous system: provides conscious and subconscious control over skeletal muscles

autonomic nervous system: controls internal/visceral functions largely outside our awareness 

whats the difference between the sympathetic and parasympathetic nervous system?

sympathetic nervous system: heart rate increases, pupils dilate, digestion slows down, breathing accelerates

parasympathetic nervous system: heart rate decreases pupils constrict, digestion stimulates, breathing slows

what are the 3 aspects of information processing ?

1. sensory (afferent) input travels from a sensory receptor

• somatic reception

• visceral reception

• peripheral nervous system

2. integration of info in the brain or spinal cord and produces a response

• central nervous system

3. motor (efferent) signals carried to the effector organ

• somatic motor response of visceral motor response

• peripheral nervous system

what are reflexes and the reflex arc ?

reflexes: are rapid, automatic motor response to stimuli (external or internal) 

• do not involve voluntary control of body 

• no integration in the brain, goes straight through the spinal cord 

reflex arc: simple chain of neurons involved in reflexes 

• shows basic structural plan of nervous system

what are the two types of cells in the nervous system?

neurons: functional cells

• send signals for sensory and motor functions

glial cells: support cells (help neurons function)

• do not send signals

whats a neuron

• it is the basic structural unit of the nervous system

• approx 35-100 billion neurons in an adult

functions

• conduct electrical impulses

• extreme longevity

• non-mitotic

• high metabolic rate

whats the anatomy of the neuron ?

cell body (aka: soma): control center 

• contain nucleus and other organelles 

dendrites 

• short small processes that branch from cell body

axon

• long processes that leave the body 

What are the structures of the axon

• the axon is wrapped in myelin sheath

axon hillock: connection of axon to cell body

axon collaterals: branches that bud from axons

axon terminal (aka: telodendria): extensive branching at distal end of axons

synaptic knobs: extreme tips of axon terminals

node of ranvier: segment of axon between myelin sheath

myelination: process of wrapping axons with concentric layers of plasma membrane fro glial cells

what are the two components under impulse conduction?

action potential: when the voltage across the membrane changes 

• this is the signals that travels down a nerve 

• depolarization: sodium enters the cell and initializes an action potential 

continuous conduction: transmission of an impulse that moves molecule by molecule along an unmyelinated axon 

• relatively slow transmission 

whats saltatory conduction ?

the transmission of an impulse that skips from node to node along a myelinated axon

• fast transmission

• ex: walking fast = myelinated

whats an synapse?

a specialized junction between neurons and a subsequence cell

• ex: other neurons, muscle cells or glands

• area of communication

what are the 3 structures of the synapse ?

presynaptic neuron: carriers impulse towards synapse

• ex: acetylcholine

synaptic cleft: narrow space between presynaptic and postsynaptic neuron

postsynaptic neuron: conduct impulse away from synapse

• membrane has neurotransmitter receptors

what are the 3 types of synapses ?

axodendritic synapse:

• between synaptic knob of presynaptic neuron and the dendrite of postsynaptic neuron 

• most common type 

axosomatic synapse: 

• between synaptic knob of presynaptic neuron and cell body of postsynaptic neuron 

axoaxonic synapse: 

• between synaptic knob of presynaptic neuron and postsynaptic axon 

• lest common type 

what are the 3 structural classifications on neurons ?

1. unipolar neurons: neurons with short single process emerging from cell body, that branches like a T

• peripheral processes: goes from dendrites of axon to cell body

• central process: goes from cell body into the CNS

• dendrites are short and multi-branched with receptive endings

2. bipolar neurons: have one axon and one dendrites extending from a single cell body

3. multipolar neurons: many dendrites and a single axon extending from the cell body

• most common type of neuron

what are the 3 functional classifications of neurons ?

1. sensory neuron (afferent)

• carry impulse from receptors to CNS

2. motor neurons (efferent)

• carry impulse from CNS to muscles or glands

3. interneurons (association neurons)

• lie entirely in CNS

• carry out integrative functions such as decision making, processing, etc.

what are the classifications fo neurons ?

1. unipolar neurons are always sensory neurons 

2. bipolar neurons are sensory neurons in special senses 

3. multipolar neurons are interneurons and motor neurons 

what are the 4 types of glial cells in the CNS

1. astrocytes:

• involved in the blood brain barrier

• contain glycogen and release glucose during period of high consumption

• numerous other functions

2. microglial cells

• least numerous glial cell in CNS

• respond to infections by replacing into phagocytes

• protect CNS from infection

3. ependymal cells

• inner epidermis of the CNS

• produce CSF which bathes the CNS for protection

4. oligodendrocytes

• makes myeline in the CNS

• myelin is fatty wrapping around axons in the CNS that provides insulation for quicker signaling

• one cell can myelinate several neurons and several location of those neurons

what are the 2 glial cells in the PNS

1. satellite cells

• flattened cells arranged around neuronal cell bodies in ganglia

• supply nutrients to surrounding neurons

• act as protective cushion around cells

2. schwann cells

• myelinate axons in the PNS

• one schwann cell myelinates one are of one axon

• neurolemma: refers to the thin delicate outer layer of the schwann cell that remains after myelination, the inner layers become myelin

what are the functions of the myelin sheath in the CNS and PNS 

CNS: one oligdendrocyte provides several segments of myelin on several neurons at once 

PNS: each myelin segment represents one schwann cell 

what are nerves and tracts

nerves: are bundles of parallel axons in the PNS

• most nerves are mixed nerves: they contain axons of motor sensory neurons

tracts are a collection of parallel axons in the CNS

what are the structures of a nerve

• nerves are split into multiple fascicles

• blood vessels run throughout the nerve referred to as the vasa nervorum to provide nutrients to the cells

nerves have multiple CT wrapping enclosing

• endoneurium: CT that surrounds each individual axon and its myelin sheath

• perineurium: CT that surrounds individual fascicles

• epineurium CT that surrounds the entire nerve