Module 9 - Nervous Intro Flashcards
Functions
Functions of Nervous System
Sensory – sense changes in internal and external environment – sensory receptors
Integrative – analyze information – decisions for appropriate behaviours – association neurons
Motor – respond to stimuli by initiating action – motor neurons
Components
Nerve
Brain
Cranial Nerves
Spinal cord
Spinal nerve
Ganglia
Enteric Plexus
Sensory receptors
Nerve
Nerve – bundle of axons – goes along a defined path to serve a specific region of the body
Cranial Nerves
Cranial Nerves – 12 pairs – base of brain through foramina
Spinal cord
Spinal cord – connected to brain at foramen magnum – surrounded by vertebra
Spinal nerves
Spinal nerves – 31 pairs – contact specific region
Ganglia
Ganglia – outside brain and cord – nervous tissue – contain the cell bodies of neurons
Sensory receptors
Sensory receptors – parts of neurons or specialized cells monitoring changes inside and ou
CNS
CNS – central – brain and spinal cord
PNS
PNS – peripheral – cranial and spinal nerves – sensory = afferent – motor = efferent – ganglia and sensory receptors – subdivided into SNS and ANS
SNS
SNS – Somatic – voluntary – neurons conduct impulses from cutaneous (skin) and special sense receptors to CNS – motor neurons conduct from CNS to skeletal muscle tissue
ANS
ANS – Autonomic – involuntary – smooth and cardiac muscle – sensory neurons from visceral organs – motor neurons convey impulses from CNS to smooth, cardiac muscle tissues and glands – subdivided
Sympathetic & Parasympathetic
Sympathetic
Sympathetic – fight or flight
Parasympathetic
Parasympathetic – rest
ENS
ENS – Enteric – neurons in enteric plexuses extending length of GI tract – many neurons function independently from ANS and CNS – sensory = monitor chemical changes of GI and stretching of walls – motor neurons = contractions and control endocrine cells
Neurons
Neurons
Electrical excitability
Parts:
Cell body (Soma)
Dendrites
Axon
Synapse
Cell body (Soma)
Cell body (Soma) – nucleus, lysosomes, mitochondria, golgi complex, and rough endoplasmic reticulum – RER = NISSL BODIES – Neurofibrils = cytoskeleton
Dendrites
Dendrites – many – conduct impulses from receptor or neurons to cell body
Axon
Axon – single – conduct impulses from neuron to dendrites, or to cell body of other neurons, or to effector organ – muscle or gland
Synapse
Synapse – functional contact b/w two neurons or neuron and effector
Neuroglia
Neuroglia - Specialized cells to support neurons
Myelin
Myelin – electrically insulate axon and increase conduction – lipid and protein covering – surround axon of neurons – gaps = nodes of Ranvier
CNS Neuroglia
CNS Neuroglia
Astrocytes
Oligodendrocytes
Microglia
Ependymal cells
Astrocytes
Astrocytes – filter – build and regulation blood-brain barrier – maintain the balance of extracellular ions – control the production of neurotransmitters – modify synapse – maintains chemical environment - CNS
Oligodendrocytes
Oligodendrocytes – support – myelin production - CNS
Microglia
Microglia – phagocytotic = cell eating – immune responses – take out bad cells - CNS
Ependymal cells
Ependymal cells – line fluid-filled spaces in brain – barrier b/w cerebrospinal fluid and brain tissue – control production and flow CSF, brain metabolism, and waste clearance - CNS
PNS Neuroglia
PNS Neuroglia
Schwann cells
Satellite cells
Schwann cells
Schwann cells – myelin (neurolemma) production – maintain and regenerate axons - PNS
Satellite cells
Satellite cells – support – nutrients to neurons – protective and cushioning cells - PNS
White Matter
White Matter – Communicator – pale tissue
Long axons with myelin sheaths and unmyelinated
Cortex of brain – 60% of brain
Surface of spinal cord – outside of “H” – surrounds grey
Transmits sensory and motor impulses b/w PNS and grey matter
Controls involuntary functions
Blood pressure
Heart rate
Temperature
Grey Matter
Grey Matter – Processor – darker tissue
Surface of brain – forms cortex – 40%
Inside spinal cord
Cell bodies, axon terminals, & dendrites
Capillary blood vessels
Unmyelinated axons
Neuroglia
Processes white matter info, sends instructions to effectors through white matter
Controls senses and muscle control
Hearing
Feeling
Seeing
Speech
Memory
Resting membrane potential
Resting membrane potential
Existence of transmembrane polarity
Determined by unequal distribution of ions on plasma membrane
Na+ - pumps compensate for slow leak into cell – pumps it out
K+
Voltage measured across a membrane – usually -70 millivolts = polarized
Positive outside
Negative inside
Ion channels allow ion movement across membrane to change potential
Leakage – non-gated – always open
Gate – open and closed
Voltage changes
Specific ligands (chemical)
Mechanical vibration or pressure
Synaptic Events
Synaptic Events
1) Impulse at bulb of axon
2) Ca+ channels open, Ca+ flows in
3) Neurotransmitters release into synaptic gap/cleft
4) Bind to receptors, open ion channels on dendrites
5) More ions enter and can trigger impulse
Uptake of Neurotransmitters
Diffusion
Enzymatic degradation
Uptake into cells
Action Potentials
Action Potentials – communication over short and long distances
Rapid
Conducts/propagates point to point across membrane = nerve impulse
Voltage gates for Na+ and K+ open
All or nothing – stronger stim doesn’t = stronger action
Depolarization
Depolarization
Decrease and reverse membrane potential
Activation gate – Na+ gates open – send rush of + ions into cell – throws off the charge of the cell
Must pass threshold to full excite membrane = -55mv or reversed
Rises to +30mv
Nerve impulse is fired
Continuous conduction
Continuous conduction – unmyelinated – slower – travels down axon
Saltatory conduction
Saltatory conduction – myelinated – fast – jumping node to node
Repolarization
Repolarization
Restoration of resting membrane potential
Even out chargers within membrane
K+ gate opens – delayed reaction
Inactivation gate – Na+ closes
Refractory period – Absolute – Impulse cant be generated
Hyperpolarization
Hyperpolarization
K+ channel is late – pumps too much back in
Overextends – too negative
Refractory period – relative
Must send back to resting membrane potential = -70mv
- suprathreshold stim
Rules of Propagation
Rules of Propagation
Larger fibres = faster impulse – more flow
Myelinated = faster – less energy needed
Warm = faster conduction
Grade Potentials
Grade Potentials – communication over short distances
Waves in pond
Dendrites – Starting = high membrane potential
Soma – Waves get smaller and smaller as they travel
Doesn’t always have a strong enough charge to make it to the axon hillock where it would be propagated
Over time charge will add up and hit the threshold
Gates open over time
Neurotransmitter
Neurotransmitter
Excitatory or inhibitory
Body’s chemical messengers
Transmit messages between neurons, or from neurons to muscles
Classes of Neurotransmitters
2 classes of Neurotransmitters
Small molecule – acetylcholine, amino acids, biogenic amines, ATP, purines, and gases
Neuropeptides – amino acids linked by peptide bone
Types of Neurotransmitters
Types of Neurotransmitters
Acetylcholine – ANS – Contracts smooth muscles, dilates blood vessels, increases bodily secretions, and slows heart rat
Glutamate – CNS – memory, cognition, and mood regulation
Aspartate
GABA – CNS – gamma-aminobutyric acid – chemical messenger in, slows down by blocking specific signals in CNS – calming effect.
Glycine
Norepinephrine - neurotransmitter and hormone - “fight-or-flight” – mobilizer
Epinephrine – neurotransmitter and hormone - “fight-or-flight” – mobilizer
Dopamine – emotions, behavior, and movement
