Block D Flashcards
functions of the CNS
homeostasis- keeping environment of body constant
perception- sight, taste, smell, hearing
movement & coordination
intellect & emotions
what is the CNS composed of
brain and spinal chord
types of neurons in cerebellum
basket cell, purkinje cell, pyramidal cell, stellate cell
astrocytes in glial cells
connect with neurones and blood vessels
ependymal cells in glial cells
line ventricles, spinal canal, CSF circulation
oligodendrocytes in glial cells
myelin sheath in CNS
microglia in glial cells
phagocytes, scavengers
myelin sheath
oligodendrocyte in CNS, Schwann cell in PNS
wraps around axon -> electrical insulation increases speed of action potential conduction
forebrain
outer= cerebrum, corpus striatum, hippocampus
inner= thalamus, hypothalamus
midbrain
basal ganglia including substantial nigra
hindbrain
cerebellum, medulla oblongata, pons, reticular formation
outer forebrain
comprises nerve cells (grey matter)
lobes on the outer forebrain
frontal, parietal, temporal, occipital
corpus striatum
part of basal ganglia, coordinated body movements
hippocampus
part of limbic system- emotion: pleasure, hostility, anger, instincts
involved in memory
thalamus
relay centre
receives sensory input-> cerebrum
relays cerebrum motor output-> other areas
hypothalamus
regulates autonomic, endocrine systems
essential for hunger, thirst, osmotic balance, body temperature, metabolic rate
substantia nigra
in midbrain, part of basal ganglia, coordinated body movements
cerebellum
-in hindbrain
-2nd largest structure in whole brain
-fine, coordinated body movements
what is the brainstem made up of
midbrain, pons, medulla oblongata
brainstem
-continuous with spinal cord
-ascending & descending nerves to/from forebrain
-visceral reflexes- heart rate, digestion, breathing
damage = death
brain stem reticular formation
within brain stem, modulates level of wakefulness/sleep
spinal cord
-neuronal cell bodies in centre (butterfly shape)
-surrounded by ascending & descending nerve tract
ventral root
motor/efferent nerves leaving cord and innervate effectors
dorsal root
sensory/afferent nerves entering cord
dorsal root ganglion
sensory nerve cell bodies
what does cerebrospinal fluid do
supplies metabolites, physically protects brain and spinal cord, provides appropriate chemical environment for neuronal function, aids removal of waste to venous system
metabolite supply to the brain
-CNS-> 2% body weight, but high metabolic rate
-no glycogen stores so relies on blood glucose and oxygen supply to function
-receives 15% blood pumped by heart
-20% total body oxygen usage
what does the blood-brain-barrier (BBB) do
separates CNS from blood
BBB structure
tight junctions between endothelial cells
astrocytes-> 2nd barrier
what does BBB restrict from blood to CNS
-small, non-ionised, lipid-soluble compounds eg O2, CO2, hormones
-substrates for specific transporters eg glucose, essential amino acids, ions
what does injury and inflammation lead to
BBB brekadown
CNS exposed to harmful substances
what does cerebrospinal fluid fill
ventricle spaces in brain
where does CSF flow
from ventricles to surround the brain and spinal cord + small amount into spinal canal, exists via one-way valves to veins
what are choroid plexus
ependymal cells + capillary bed
how much CSF does choroid plexus produce
20ml per hour (total adult volume 130-150ml)
what do ependymal cells secret
sodium ions actively into ventricle followed by chlorine ions passively, which increases osmotic pressure driving water into ventricle
types of non-peptide neurotransmitters
monoamines- noradrenaline, dopamine, serotonin, histamine
amino acids- GABA, glutamate, glycine
others- acetylcholine, ATP, nitric oxide
what is the criteria for identifying a substance as a neurotransmitter
synthesised within neuron, stored in nerve terminal, released by nerve stimulation in calcium-dependent manner, specific mechanisms exist for inactivation, exogenously applied substance mimics endogenous response to neurotransmitter, antagonist inhibits both neurotransmitter & exogenously applied substance
noradrenaline as a transmitter
distributed from brain stem to cortex, limbic system, cerebellum, brain stem. reward system and mood, state of arousal, blood pressure regulation
dopamine as a neurotransmitter
distributed from SN to basal ganglia VTA to limbic system & cortical forebrain hypothalamus to pituitary. motor control reward system, mood, motivation prolactin secretion
seretonin as a neurotransmitter
distributed from brain stem to cortex, limbic system, thalamus, hypothalamus, cerebellum. sleep, wakefulness, temperature regulation, mood
acetylcholine as a neurotransmitter
distributed from long&short projections from basal forebrain interneurons in basal ganglia. arousal, learning and motor control
glutamate as a neurotransmitter
distributed widespread, mainly as interneurons. memory, epilepsy, relay or sensory information
GABA as a neurotransmitter
distributed widespread, mainly as interneurons. anxiety and epilepsy
glycine as a neurotransmitter
distributed spinal cord interneurons, modulates NMDA receptors
neuropeptides
1975: enkephalins are neurotransmitters, 5->30 amino acids long, many functions eg substance P in pain
similarities between neuropeptides and classical neurotransmitters
stored in vesicles, calcium ion dependent release, effect-> 2nd messengers/ change in ion channel activity
slow neurotransmission
seconds to minutes, indirect- via G proteins and cytoplasmic 2nd messengers
fast neurotransmission
10’s of milliseconds, direct- via receptor-operated ion channels
sensory systems
vision, somatic sensory (touch), gustatory (taste), olfaction (smell), auditory (hearing), movement proprioception (balance)
sensory reception
stimulus-> sensory receptor-> afferent neuron-> integration center (CNS)-> efferent neuron(s)-> effector organ-> response
what does sensory reception do
maintains homeostasis, detects and reacts to changes in environment, protects body from damaging stimuli
cutaneous receptors
touch, pressure, temperature, pain
proprioceptors
body position
