Chp 9 - Nervous system

neurotransmitters

chemical messengers of nervous system

neurotransmitters are produced only by

neurons

neurotransmitters travel short distances across spaces between nerve cells called

synapses

hormones

chemical messengers of the endocrine system

hormones are secreted directly into the ___

blood stream

2 main divisions of the nervous system

1. central nervous system

2. peripheral nervous system

what is the central nervous system composed of

1. brain 

2. spinal cord

what is the peripheral nervous system composed of

• cordlike nerves

• link CNS with rest of the body

3 main categories of Nervous system activities

1. sensory functions

2. integrating functions

3. Motor functions

functional units of the nervous system

neurons

neurons have a high requirement for ___

oxygen

after an animal is born, neurons lose their ability to ___

reproduce

neurons can still ___ cell processes if the cell body remains intact

regenerate cell processes

neuroglia

cells that structurally & functionally support & protect the neutrons

perikaryon

neuron central cell body

another term for perikaryon

soma

dendrites

• receive stimuli, or impulses, from other neurons

• conduct this stimulation to the cell body

are dendrites afferent or efferent processes

afferent

Dendrites may also be modified into ___

sensory receptors

Axon

• conduct nerve impulses away from the cell bpdy

• toward another neuron/effector cell

effector cell

• cell that does something when stimulated

• exp. muscle or gland cell

are axons afferent or efferent processes

efferent

another term for axon

nerve fibers

nerve fibers

bundles of axons that make up cordlike nerves in the body

Axons are often covered by ___

myelin

myelin

sheath of a fatty substance

white matter

nervous tissue containing many nmyelinated axons/nerve fibers

gray matter

nervous tissue made up largely of neuron cell bodies

myelin sheath in the brain & spinal cord

made of the cell membranes of oligodendrocytes

myelin sheath outside the brain & spinal cord

made of the cell membranes of schwann cells

oligodendrocytes

specialized glial cells associated with the CNS

schwann cellls

specialized glial cells associated with the PNS

nodes of ranvier

• small gaps in the myelin sheath

• between adjacent glial cells

Mylein sheath and nodes of Ranvier work together to enhance the speed of ___ along the axon

conduction of nerve impulses

cranial nerves

• few nerves of PNS

• originate directly from the brain

spinal nerves

most PNS nerves emerge from the spinal cord

afferent nerve fibers

conduct impulses toward the CNS

efferent nerve fibers

conduct impulses away from the CNS

another term for afferent nerve fibers

sensory nerve fibers

another term for efferent nerve fibers

motor nerve fibers

sensory nerve fibers

• conduct sensations

• from sensory receptors in the skin & other locations → CNS

motor nerve fibers

• conduct impulses

• from CNS → toward muscles & other organs

most nerves in the PNS are what type of nerves

mixed nerves

somatic nervous system

voluntary, control of skeletal muscles

autonomic nervous system

self-regulating system that controls & coordinates involuntary functions

autonomic motor nerves send impulses to ___

1. smooth muscle

2. cardiac muscle

3. glands

sodium-potassium pump pushes the sodium ions from where to where

from inside the neuron to the outside

sodium-potassium pump pushes the potassium ions from where to where

from the outisde to inside the neuron

resting membrane potential

electrical difference in charges across neuron’s membrane

depolarization

• opening of sodium channels

• sudden influx of many sodium ions → inside cell

during depolarization, the inside of the neuron goes from a ___ charged resting membrane potention to a net -__ charge

negatively → positively

action potential

significant change in electric charge from negative to positive

repolarization

• closing of sodium channels ​

• opening of potassium channels

• potassium ions flow out of cell

during repolarization, sufficient outflow of potassium ions restores the net ___ charge to inside of cell​

negative

difference between end of repolarization phase & resting state

sodium & potassium ions are on the opposite sides from where they began

Threshold stimulus​

Stimulus is strong enough to cause complete depolarization and to generate a nerve impulse​

All-or-nothing principle in neurons

either the complete neuron depolarizes to its maximum strength or doesn’t depolarize at all

refractory period

• Very brief time period when a neuron is insensitive to additional stimuli​

• Cell is still in depolarization/early repolarization

Absolute refractory period​

During Na+ influx and early K+ outflow​

Relative refractory period​

• During end of repolarization period​

• Possible to stimulate another depolarization if stimulus is very large​

saltatory

saltare - to leap

saltatory conduction

allows rapid transmission over distance in long neurons

how does saltatory conduction work

• depolarization happens at the node of ranvier

• when one sodium channel is open, it opens the next adjacent one

• depolarization wave like dominos

saltatory conduction is mediated by what 2 parts of the neuron

1. myelin

2. nodes of Ranvier​

example of anesthetic drug

lidocaine

Lidocaine

• blocks nerve sodium channel of afferent sensory nerve

• no depolarization = no sensation (no pain)

synaptic transmission

the continuation of the nerve impulse from one neuron to the next cell

Synapse

Junction between two neurons or a neuron and a target cell​

Synaptic cleft​

Gap between two adjacent neurons​

Presynaptic neuron​

• Brings depolarization to synapse​

• Releases neurotransmitter

Postsynaptic neuron​

Contains receptors for the neurotransmitter​

telodendron

branched structure at the end of the axon on the presynaptic neuron

each branch of the telodendron ends in a slightly enlarged bulb called the ___

terminal bouton, synaptic end bulb, OR synaptic knob

two types of neurotransmitters

1. Excitatory neurotransmitters​

2. Inhibitory neurotransmitters​

Excitatory neurotransmitters​

• Usually cause influx of Na+

• postsynaptic membrane moves toward threshold

• beginning a new impulse 

Inhibitory neurotransmitters​

• Make inside of cell more negative

• moving the charge within the postsynaptic cell farther away from threshold​

Acetylcholine

neurotransmitter

at the junction between somatic motor neurons and the muscles they supply, Acetylcholine is an ___ neurotransmitter that stimulates muscle fibers to contract

excitatory

Acetylcholine at the side where parasympathetic nerves synapse with the heart, it has an ___ effect that slows heart rate

inhibitory

3 neurotransmitters belonging to Catecholamines

1. Norepinephrine​

2. Epinephrine​

3. Dopamine

Norepinephrine

• associated with arousal 

• fight-or-flight reactions of the sympathetic nervous system

Epinephrine

released from the adrenal medulla (center of adrenal gland)

Epinephrine plays a role as a ___ in the fight-or-flight reactions of the sympathetic nervous system

hormone

Dopamine

• found in brain

• involved w/ autonomic functions & muscle control

what type of neurotransmitter is Gamma-aminobutyric aid (GABA)​

inhibitory 

what type of neurotransmitter is Glycine

inhibitory 

Gamma-aminobutyric aid (GABA)​

found in the brain

Glycine

found in the spinal cord

Acetylcholinesterase

• found on the postsynaptic membrane

• enzyme that breaks down acetylcholine

Monoamine oxidase (MAO)​

enzyme that breaks down Norepinephrine

Catechol-o-methyl transferase (COMT) ​

enzyme that breaks down any Norepinephrine not reabsorbed by the synaptic knob

Main 4 components of CNS

1. Neuron cell bodies​

2. Myelinated

3. unmyelinated nervefibers​

4. Glial cells

4 divisions of the brain

1. cerebrum

2. cerebellum

3. diencephalon

4. brainstem

Cerebrum​

Largest part of brain in domestic animals​

what is cerebrum made of

1. gray matter in the cerebral cortex

2. white matter beneath cortex (including corpus callosum)

cerebral cortex

outermost superficial layer of the brain

corpus callosum

set of fibers that connects two halves of the cerebral cortex

cerebrum functions

associated with learning and intelligence​

gyri

folds that make up the cerebrum’s wrinkled appearance

fissures

deep grooves that separates gyri in cerebrum