Nervous System

A&P 1 exam 4

what is included in the central nervous system?

brain & spinal cord - process and coordinate sensory data from inside and out

what is included in the peripheral nervous system?

all tissue outside CNS - deliver sensory info to CNS; has cranial and spinal nerves - connects to the structures

What are nerves

bundles of axons w/ connective tissue and blood vessels only in PNS

Afferent division

(approach) carries sensory info - from receptors and organs to CNS

efferent division

(exit) carries motor commands - from CNS to effector

receptors

detect changes/ respond to stimuli - start of afferent pathway - (neurons/specialized cells/complex sense organs (eyes/ears))

effectors

target organs that respond to motor commands (muscles/glands/adipose tissue) - end pathway

somatic nervous system (SNS)

voluntary movement of skeletal - efferent system include reflexes (involuntary and voluntary)

autonomic nervous system (ANS)

viceral organ environment - subconscious actions (cardiac muscle, smooth muscle, adipose, glands)

what are neurons used for and why

intercellular communication - excitable cell > create electrical impulses > action potential

can neurons undergo mitosis

no

what do neuroglia do

reserve structure of neurons - essential to survival - supportive cell - make up large volume

label the neuron

what are the functions of this part of a neuron in green

dendrites - process and receive info through chemically gated channels

what part of the neuron is this

axon hillock

collaterals

branches of the axon

axon terminals

synaptic terminals/knobs

what type of neuron is this

anaxonic neurons - found in brain and special sense organs

what type of neuron is this

bipolar - in retina of eye ; 1 dendrite and one axon ; small and rare

what type of neuron is this

pseudounipolar - axon & dendrites fused ; most PNS sensory neurons

what type of neuron is this

multipolar - one long axon w/ 2 or more dendrites ; common in CNS ; all motor neurons for skeletal muscles

what are sensory neurons

pseudounipolar - afferent fibers extend from sensory receptors to cns

what are interoceptors

monitor internal systems - visceral sense receptor

what are exteroceptors

monitor external environment - somatic

what are proprioceptors

monitor position and movement of skeletal muscles and joints - somatic

where do motor neurons carry instructions

from cns to peripheral effectors (via efferent fibers)

what does visceral neurons effect

smooth, cardiac, glands, & adipose tissue

where are interneurons found

in the cns between sensory and motor neurons

what type of neuroglia is this and what does it do

astrocyte - only in brain/spinal cord - nourish neurons; maintain BBB; repair nervous tissue damage

what type of neuroglia is this and what does it do

ependymal cells - epithelium lining central canal; of spinal cord and ventricles - filter blood to produce CSF (uses cilia)

what type of neuroglia is this and what does it do

oligodendrocytes - form myelin sheaths

what are internodes

myelinated section of axon

nodes of ranvier

between internodes - no myelin

what is the white mater made of

myelinated axons

what is grey mater made of

unmyelinated axons, cell bodies, and dendrites

what type of neuroglia is this and what does it do

microglia - least common - migrate thro nervous tissue, cleans up cellular debris, waste, & pathogens

where are satellite cells and Schwann cells found

in the PNS

what type of neuroglia is this and what does it do

satellite cells - surround ganglia and regs interstitial fluid around neurons

what type of neuroglia is this and what does it do

schwann cells - myelin sheath in PNS has neurolemmma

what are collections of neuron cell bodies in PNS

ganglia

what are collections of neuron cell bodies in CNS

nuclei

what are bundles of axons in the PNS called

nerves

what are bundles of axons in the CNS called

tracts

why is nervous tissue regen limited in CNS

by astrocytes producing scar tissue and release of chemicals blocking regrowth

what is wallerian degen

axon distal to injury degens and schwann cells form path for new growth

what does banana in the ocean mean

more K inside cell and more Na outside

describe why the electrochemical gradient is weak for K

chemical gradient push K outside cell and eletrical pushes K in to cell - net electrochemical gradient pushes K out of cell

describe why the electrochemical gradient is strong for Na

net electrochemical gradient pushes Na into cell - both chem and electrical gradient push Na into cell

what maintains the concentration gradients and resting memebrane potential of the neuron

Na-K exchange pump - 2 K in for 3 Na out - active transport

at resting membrane potential are the gated ion channels open or closed

closed

where are chemically gated ion channels found

where neurons communicate w/ other cells

what is the threshold stimulus to stimulate an action potential

-55 mV

where are voltage gated ion channels found and what does inactivated mean

axons of neurons - closed and incapable of opening

what do mechanically gates ion channels respond to

touch pressure or vibration - membrane distortion

what is a membrane potential

electrical charge difference across plasma membrane

how does the resting membrane potential differ in ionic comp

ECF: high Na Cystol: high K and neg proteins

current

movement of charges to eliminate a potential difference

resistance

how much the membrane restricts ion movement - if resistance high current is small

what influences resistance across membrane

ion channels - movement increased or decreased affects current affecting resistance

graded stimulus

change in electrical activity but too low to trigger action potential (less than -55

threshold stimulus

stimulus strong enough to create action potential (@ or greater than 55)

what is the process of causing a graded potential

chemical messenger binding to chemically gated channels = movement of ions

depolarization

less negative charge inside cell - opens chemically gated Na channels

repolarization

restoration charge towards RMP after depolarization - stimulus removed

hyperpolarization

more negative than RMP inside cell - opening chemcially gated K ion cahnnels

where do action potentials go

from entire excitable membrane to the next and do not diminish as they move from source

what are the sections of this graph

when do potassium channels open on the action potential graph

at the start of repolarization

when do sodium channels open on the action potential graph

throughout depolarization and close at peak

all or none principle

any stimulus changing membrane potential to threshold will cause action potential - all are the same - either triggered 100 or 0

what are the steps of the generation of action potential

1. chemical stimulus - depolarization to threshold

2. activation of volt-gated Na channels - inner membrane changes from neg to positive

3. repolarization - inactivate Na and activate K (k moves out of cystol)

4. hyperpolarization - K volt channels close and K continues to leave cell past resting

5. return to RMP

refractory period

membrane will not respond to additional stimulus

absolute refractory

membrane cannot respond to further stimulation (during AP)

relative refractory period

only strong stimulus initiate another action potential - continues until membrane potential stabilizes (after AP and during repolarization

continuous propagation

AP in unmyelinated axons

saltatory propagation

AP in myelinated axons - faster than continuous - current jumps from node to node

how does diameter affect propagation speed

the larger the diameter the faster the speed

chemical synapses

signal transmitted across a synaptic cleft by neurotransmitters

axodendritic synaptic communication

axon of 1 neuron and dendrite of another

axosomatic synaptic communication

axon of 1 neuron and soma of another

axoaxonic synaptic communication

axon of 1 neuron and axon of other

what is a cholinergic synapses

release acetylcholine

what is a adrenergic synapses

release norepinephrine (NE) epinephrine (E) (adrenaline

what are the events of the cholinergic synapse

1. axon depolarized by AP

2. depolarization open volt-gate Ca channels - trigger synaptic vessel to release ACh

3. ACh diffuse across cleftbinds to chem-gate Na channel receptors of postsynaptic memebrane

what is a synaptic delay

time required for Ca ion influx and neurotransmitter release

what does excitatory neurotransmitters cause

depolarization - promote AP

what does inhibitory neurotransmitters cause

hyperpolarization - suppress AP

excitatory postsynaptic potential (EPSP)

graded depolarization of postsynaptic membrane - membrane=excited - potential closer to threshold

inhibitory postsynaptic potential (IPSP

graded hyperpolarization of postsynaptic membrane - shift away from threshold

what is summation

integration of effects of graded potentials - net effect can be no change to emembrane potential

what is information processing

the response of a postsynaptic cell

what does the axon hillock do

integrates all stimuli - determines if AP will happen

temporal summation

rapid repeated stimuli of single synapse

spatial summation

multiple synapses activate at same time - AP generated if membrane = threshold

neuronal pools

interneurons organized into function groups of neurons

what type of neuronal pool is this

serial processing - pain signals

what type of neuronal pool is this

divergence - permits broad distribution of specific input - common in sensory pathways

what type of neuronal pool is this

convergence - control of diaphragm in breathing

what type of neuronal pool is this

parallel processing - step on a nail and move and say ouch

what type of neuronal pool is this

reverberation - postive feedback loop - breathing muscle coordination