Nervous System Flashcards
Define NEURON
An electrically excitable cell
Receives, processes & transmits info via electrical & chemical signals.
Define NERVE
Bundle of axons in PNS - conduct impulses between CNS & body.
(axons & neuroglia)
Define NERVOUS SYSTEM
Network of nerve cells & fibres which transmits nerve impulses between bodily parts & coordinates its action.
MACROGLIA
+ main glial cells
+ functions
Cells in CNS & PNS
astrocytes, oligodendrocytes & Schwann cells
nutrition, support, synthesise myelin
MICROGLIA
+ functions
tissue-based macrophages
phagocytosis & protect CNS neurons.
Sensory (afferent) input neurons
Location.
Convery info from tissue stimulus -> CNS.
In PNS.
Motor (efferent) output neurons
Location
Transmit signals from CNS to PNS (effector muscles/glands)
Motor cortex, brain stem & spinal cord.
Interneurons (relay / association)
+ Location
+ Function
Transmit signals between neurons (sensory - motor) (via dendrites).
+ Brain, visual system, spinal cord. (CNS)
+ Information processing & decision making.
Neurosecretory cells
Location
Secrete hormones.
Hypothalamus, adrenal medulla, thyroid gland & hormone secretory organs.
Unipolar neuron
ONE neurite extends from cell body.
Mostly sensory.
PSEUDOUNIPOLAR neuron
Dendrites & axons fused in a single process which divides into 2 processes (axon & dendrite).
BIPOLAR neuron
Has 2 neurite extensions.
Specialised sensory neurons (olfactory cells, inner ear, retina)
MULTIPOLAR neuron
Single axon & many dendrites.
ANAXONIC neuron
axon cannot be differentiated from dendrites.
Often intermediate in multipolar neuron development.
GLIA / NEUROGLIA
+ Functions.
Non-neuronal cells.
- maintain homeostasis: form myelin & support/protect neurons in C&PNS.
Functions of glial cells
- support neurons
- supply nutrients & O2 to NS
- insulate neurons
- destroy pathogens & dead neurons
State 4 CNS macroglial cells.
Astrocytes
Oligodendrocytes
Ependymocytes
Radial glia
State 3 PNS macroglial cells.
Schwann, satellite, enteric glial cells.
Astroglia functions
Form BBB
Regulate external environment of neurons : remove XS K+ ions & recycle neurotransmitters.
Oligodendrocytes
form myelin - coat axons
Ependymocytes
CSF filled.
line spinal cord & brain ventricular system.
Radial glia
Involved in neurogenesis.
Schwann cells
form myelin - coat axons
Satellite cells
Regulate external chemical environment.
Enteric glial cells
Regulate homeostasis in intrinsic ganglia of digestive system.
Describe the structure of a nerve
3 layers: epineurium, perineurium, endoneurium.
Nerve: covered by the EPINEURIUM, contains neurons bundled in fascicles.
Each fascicle is covered by the PERINEURIUM.
ENDONEURIUM covers each small fibre.
CNS
Brain & spinal cord.
INTEGRATION & CONTROL
PNS
Cranial & spinal nerves
Communication pathways between CNS & rest of body.
Sensory (afferent) division
Conduct impulses from receptors to CNS
Motor (efferent) division
Conduct impulses from CNS to effector muscles.
Autonomic NS
Involuntary (unconscious)
Conducts impulses from CNS to cardiac & smooth muscles, glands…
Somatic NS
Voluntary
Conducts impulses from CNS to skeletal muscles.
Sympathetic NS
Fight or flight
Parasympathetic NS
Rest & digest
Enteric NS
Regulate GI tract function
State the 3 branches of the ANS
Sympathetic, parasympathetic & enteric NS.
Define REFLEX ARC
Neural pathway which controls physiological reactions.
Unconditioned reflex
Automatic innative instinctive reaction to a stimulus.
Conditioned reflex
Automatic response established by training.
Outline the pathway of a reflex arc
Stimulus - sensory (afferent) nerve - CNS & motor nerve - motor (efferent) nerve - effector muscle/gland
Neurons communicate via ____
Synapses
Where are neurotransmitters synthesised?
Neuron cell body
then transported down axon
What happens to vesicles without neurotransmitter?
Transported back to cell body.
Describe synaptic transmission from the point where an action potential reaches axon terminal.
- Membrane DEPOLARISATION.
- Voltage-gated Ca2+ channels open.
- Ca2+ influx triggers release of neurotransmitters from vesicles.
- Neurotransmitters bind to receptors -> excites/inhibits postsynaptic neuron.
- Neurotransmitters then recycled.
Excitatory synapses induce cell ____ .
Induces ___ influx in post synaptic neuron.
depolarisation
Na+
Inhibitory synapses induce cell ___ .
Induces __ influx in post synaptic neuron.
hyperpolarisation
Cl-
