Nervous System I Flashcards
Sensory input is information gathered by
By sensory receptors about internal and external change
Integration
Interpretation of sensory output
Motor output (hint: think efferent pathway)
Activation of effector organs (muscles and glands) produces a response
CNS- central nervous system
Brain and spinal cord- integration and command centre
PNS- Peripheral nervous system
Paired spinal and cranial nerves carry messages to and from CNS
ANS Autonomic Nervous System
Sympathetic and parasympathetic- involuntary nervous system eg heart and gastrointestinal
Neurons transmit
Electrical and chemical signals, can live longer than 100 years
Dendrites
Synapse with other neurons and are receptive input region
Axon hillock
Site of electrical impulse (action potential) generation in response to stimulus from dendrites
Axon is the…
Outgoing tail, generates and transmits nerve impulses away from cell body
Neuroglia are glial cells
Groups of supporting cells in CNS and PNS eg Schwann cells
Myelin sheath role
Protects and electrically insulated the axon to prevent charge leaks, increases conduction velocity of nerve impulse transmission.
Myelin sheath Schwann cells
Wrap around axon many times
Myelin sheath Nodes of Ranvier
The gaps between Schwann cells
Electrical current is
The imbalance of ions across cell membrane and subsequent movement of these ions
Polarisation
Membrane is at rest neurons ~70 mV
Depolarisation
Membrane potential less negative ~ -70 to ~ +30 mV
Hyperpolarisation
Membrane potential more negative than testing polarised potential -70 - -90 mV
Membrane ion channels- Leakage
Non-gated ion channels always open
Voltage gated ion channels
Ion channels open in response to changes in membrane potential
Mechanically gated channels
Open and close in response to physical deformation of receptors eg hair cells of inner ear
Ions during polarised
Inside membrane more K+ ions than Na+
Channels closed
Ions during Depolarisation phase
Na+ channels open and Na+ flows down concentration gradients in cell. More positive near inside of cell membrane
Ions during depolarisation phase
Na+ channels close and K+ channels open so K+ flows out of cell. More negative bear inside of cell membrane
Ions during hyperpolarisation phase
Some K+ channels open to allow excessive efflux. Some Na+ channels open allowing membrane potential to return to polarisation
Threshold refers to
Membrane potential required to stimulate an action potential.
Na+ permeability increases triggering action potential event
Subthreshold stimulus refers to
Weak local depolarisation that does not reach threshold. No action potential event
Absolute refractory period
Resistant to stimulus where neuron cannot respond to another stimulus. Enforces one way transmission of nerve impulses
Relative refractory period
Follows absolute refractory when depolarisation is occurring. Threshold for AP generation is elevated during hyperpolarisation
Conduction velocity
Myelinstion can speed conduction velocities. At node of ranvier, voltage gated Na+ ion channels open and ions flow to next node of ranvier.
Synapse is
The gap between axon of one neuron and dendrites of another neuron
Presynaptic neuron
conducts impulses towards the synapse
Postsynaptic neuron
Transmits impulses away from synapse
Chemical synapses
Release and receive neurotransmitters
Composed of axon terminal and receptor region
Synaptic cleft
Fluid filled space separating pre and post synaptic neurons prevents nerve impulses from directly passing from one neuron to the next. Chemical event
Information transfer step 1
AP arrived at axon terminal and opens voltage gated Ca+ channels.
Information transfer step 2
Influx of Ca+ promotes fusion of synaptic vescicles with axon membrane and executor is of neurotransmitter occurs
Information transfer step 3
Neurotransmitter diffuses and binds to receptors (can be chemically gated ion channels) on postsynaptic neuron
Termination of neurotransmitter effects
Can be degraded by enzymes
Re-uptaken by axon terminal in presynaptuc neuron and recycled
Diffusion away from synaptic cleft
