nervous system

nervous system

detects changes, make decisions, stimulates muscles and glands to respond, and maintains homeostasis

neural tissue

neurons, neuroglia

neurons

• react to changes

• send nerve impulses

• communication

neuroglia

• surround and support neurons

• nourish neurons

• send & receive messages

central nervous system

brain, spinal cord

peripheral nervous system

connects cns to other body parts

• cranial nerves

• spinal nerves

sensory function

nervous system receives information

integrative function

• nervous system coordinates sensory information to create sensations, memory, thoughts

• nervous system makes decisions on body’s response to sensory information

motor function

• decisions are acted upon

• impulses are carried to effectors (muscles or glands)

• divisions of motor portion of pns: somatic nervous system, autonomic nervous system

somatic nervous system

transmit voluntary instructions to skeletal muscles

autonomic nervous system

transmits involuntary instruction form the cns to smooth muscles, cardiac muscle, and glands

cell body (soma)

contains nucleus, cytoplasm, organelles, neurofilaments, chromatophilic substance (nissl bodies)

dendrites

branched receptive surfaces; a neuron may have many

axon

transmits impulses and releases neurotransmitters to another neuron or effector (another neuron, a muscles cell or a gland cell); a neuron may have only 1 axon

cell body

• neurofilaments

• chromatophilic substance

axon

• axon hillock

• collaterals

• axon terminal

• synaptic knob

schwann cells

myelin/(sheath)

schwann cells

pns neuroglia that encase axon in a sheath

myelin

schwann cells wrap tightly around axon in layers composed of _, a lipoprotein mixture

nodes of ranvier

gaps in myelin sheath between schwann cells

multipolar neurons

• 99% of neurons

• many processes

• most neurons of cns

bipolar neurons

• 2 processes

• eyes, ears, nose

unipolar neurons

• one process

• cell bodies are in ganglia

• sensory

sensory neurons

• afferent neurons

• carry impulse to cns

• most are unipolar

• some are bipolar

interneurons

• association neurons

• link neurons

• multipolar

• located in cns

motor neurons

• multipolar, efferent

• carry impulses away from cns

• carry impulses to effectors

general functions of neuroglia

• provide structural support for neurons

• in embryo, guide neurons into position, may stimulate specialization

• produce growth factors to nourish neurons and remove excess ions and neurotransmitters

• aid in formation of synapses

astrocytes

• connect neurons to blood vessels; exchange nutrients and growth factors

• form scar tissue

• aid metabolism of certain substances

• regulate ion concentrations, such as K+

• part of blood brain barrier

oligodendrocytes

myelinated cns axons; also provide structural support

microglia

phagocytic cell; also provides structural support

ependyma (cells)

• line central canal of spinal cord & ventricles of brain, cover choroid plexuses

• help regulate composition of cerebrospinal fluid

• cuboidal or columnar cells; ciliated

schwann cells

• produce myelin sheath found on some peripheral axons

• speed up speed of nerve impulse transmission

satellite cells

support clusters of neuron cell bodies (ganglia)

synapse

neurons communicate with each other at

synapse

a site which a neuron transmits a nerve impulse to another neuron

presynaptic neuron

sends impulse (synapse)

postsynaptic neuron

receives impulse (synapse)

synaptic cleft

separates the presynaptic neuron and postsynaptic neuron

synaptic transmission

• one-way transfer of information

• impulse travels down axon of presynaptic neuron to axon terminal

• when impulse reaches synaptic knob, causes influx of Ca+2 ions

• this leads to release of neurotransmitters from synaptic vesicles by exocytosis

• neurotransmitter will exert either exictiatory of inhibitory effect on postsynaptic neuron

cell membrane potential

neurons are electrically charged because of unequal distribution of positive & negative ions across the cell membrane

outside inside

bc of active transport of Na+ and K+, neurons have a greater concentration of Na+ _ and a greater concentration of K+ _

selectively permeable membrane

determines the distribution of ions in & outside of cells

hint: K+ ions pass through it more easily than Na+

resting neuron membrane diffusion

because a _ is more permeable to K+ ions than to Na+, K+ ions diffuse out of the cell more rapidly than Na+ ions can diffuse in

every millisecond, more positive charges leave the cell by _ than enter it

resting potential

the potential difference in a resting neuron is called…(-70mV)

depolarized depolarization

if a neuron gets stimulated, the membrane’s potential decreases (inside becomes less megative0, the membrane is said to be.. greater the stimulus the greater the _

threshold potential action potential

if the depolarization is sufficient, the membrane potential reaches a level called _ (about -55mV)

if the threshold is reached, an _ results

axon hillock

thick cone shaped region from the cell body

synaptic transmission

transmission of a nerve impulse from one neuron to another

• released neurotransmitters cross the synaptic cleft and react with specific receptors in the membrane of postsynaptic neuron

• effects of neurotransmitters vary; some open ion channels and others close ion channels

• chemically gated ion channels respond to neurotransmitter

excitatory postsynaptic potential

• membrane change in which neurotransmitter opens Na+ channels

• depolarizes membrane of postsynaptic neuron, as Na+ enters axon

• action potential in postsynaptic neuron becomes more likely

inhibitory postsynaptic potential

• membrane change in which neurotransmitter opens K+ channels (or cl - channels)

• hyperpolarizes membrane of postsynaptic neuron, as K+ leaves axon

• action potential of postsynaptic neuron becomes less likely

summation

EPSPs and IPSPs added together in a process called

usually occurs at the trigger zone (axon hillock)

acetylcholine

stimulates skeletal muscle contraction

neurotransmitters

monoamines, amino acids, peptides, produces in the rough ER or cytoplasm, at least 100

exocytosis

when impulse reaches synaptic knob of an axon, neurotransmitters are released by