The nervous system Flashcards
Glial cells- general function
- surround the axon and dendrites of neurons
- provide physical and metabolic support
astrocyte function
- regulate composition of the extracellular fluid in the CNS by removing K+ and neurotransmitters around synapses
- stimulate formation of tight junctions between cells that make up the walls around capillaries
- sustain neurons metabolically (provide nutrients and remove waste
- secrete growth factors
ogliodendrocyte
form mylein sheath in the CNS
shwann cells
form mylein sheath in the PNS
microglia
microphage like cells that peform immune function in the CNS
Mylein
-concentric lipid rich layers
direction of calcium, cloride, sodium and pottasium
in, in, in, out
glutamate
excitatory neurotransmitter important for learning and memory
somatic stimuli
- muscle length and tension
- propioception
visceral stimuli
Blood pressure, ph of blood and spinal fluid, oxygen content of blood, lung inflation, osmolarity of body fluids, temperature, glucose levels of blood
somatic senses
touch, temperature, pain, itch, propioception
special senses
vision, hearing, taste, smell, equilibrium
temporal summation
two potentials arriving in a short space of time, rate is increased
spatial summation
many ion channels are opened at once
Graded Potential
- changes in membrane potential (hyperpolarising or depolarising) that are confined to a relatively small area of the plasma membrane
- magnitude can vary and is related to initiation event
- function as signals only over short distances (unless summation occurs)
NMDA receptor
- opens in response to glutamate, allowing Na and Ca influx
Snare proteins
initiate movement of vesicles to the membrane during exocytosis of neurotransmitters
PNS: somatic
- control of skeletal muscle via motor neurones
PNS: Sensory
- relays information to the CNS about the internal and external environment via afferent pathways
PNS: autonomic
- regulates smooth muscle and gland function
somatic excitation pathway
- consists of one cholinergic neurone; no synapses or ganglia
- synapses at a skeletal muscle neuromuscular junction consisting of axon terminals and motor end plates (region of skeletal muscle fibre containing many receptors)
- receptors are always nicotinic choliergic
ACh nicotinic receptor action
non selective iontropic opening, net excitation
slowly adapting receptors
neurones which persistently fire action potentials throughout period of stimulation
Rapidly adapting receptors
only respond when conditions are altered
Sympathetic pathway
- short preganglionic neurone: releases ACh which binds to nicotinic receptors
- long post ganglionic: releases noradrenaline binds to g protein coupled receptor
parasympathetic pathway
long pre-ganglionic neurone: releases ACh which binds to a nicotinic receptor
Short post-ganglionic neurone: Releases ACH that binds to muscarinic receptors on the post-synaptic membrane
Simple receptor
neurones with free nerve endings
complex receptor
nerve enclosed in connective tissue capsule
Complex non neural cells
cells that release neurotransmitters onto sensory neurones, initiating an action potential
