Chapter 2 Brain anatomy Flashcards
What are the three types of glial cells?
Astrocytes (Blood brain barrier), Microglial cells (phagocytes), Oligodendrocytes (myelin production CNS, Schwann cells myeling production PNS)
What does a neuron look like?
Dendrites receive input
Soma is cell body
AP originates in axon hillock
AP travels down axon to axon terminal
Synapse is the end where the next neuron meets
What is the difference between presynaptic and postsynaptic?
presynaptic: axon output makes connection to new neuron
postsynaptic: dendrite makes connection to previous neuron
What is the resting potential and why is it negative?
-70 mV
It’s negative, so it stores energy, because of deviation from electrochemical equilibrium
Lipid membrane has more K+ channels (more permeable for K+) and therefore more K+ travels out than Na+ can enter
How do ions travel in a neuron?
Via channels (passive) or pumps (active)
Channels can be normal or voltage-gated (open with change in voltage)
Pumps: Na+/K+ pump: pumps in K+, pumps out Na+ ; against concentration gradient
The channels and pumps are located in nodes of ranvier
What are the 7 phases of generating an action potential and what happens in each phase?
1) Resting phase: K+ channels always open
2) Depolarization: Na+ gated channels open –> more + in
3) Overshoot: most positive point, Na+ g.c. begin to close. K+ g.c. begin to open –> more + out
4) Repolarization: Na+ g.c. closed, K+ open –> more + out
5) Hyperpolarization: K+ still open –> too much + out of cell
6) Recovery phase: K+ close
7) Resting phase
What is the absolute and relative refractory period and what are the consequences?
Absolute = v.g. Na+ channels can’t open (from overshoot until hyperpolarization)
Relative = neuron can only generate AP with larger than normal depolarization (from hyperpolarization until new resting phase)
Consequences:
- Limits amount of AP’s
- Makes sure AP moves in one direction toward axon terminal
What is decremental conduction?
Passive conduction of EPSP and IPSP through the cytoplasm of the soma.
If EPSP is large enough, AP will be triggered in axon hillock
What are the two types of synaptic transmission?
1) Electrical
2) Chemical (dominant)
How does chemical synaptic transmission work? Describe in 5 steps.
1) Electrical current arrives in presynaptic terminal
2) Voltage-gated Ca2+ channels open
3) Fusion vesicles with presynaptic membrane
4) Release neurotransmitters in synaptic cleft
5) Neurotransmitters bind to post-synaptic receptors, that can create IPSP or EPSP
Name two types of postsynaptic receptors
1) ligand-gated ion channels : fast communication
2) GPCRs: G protein coupled receptors : slow communication via second messenger
Name the 6 most abundant neurotransmitters and their functions
1) Glutamate: excitatory, most prevalent
2) GABA: inhibitory, most prevalent
3) ACh: Acetylcholine: neuromuscular junctions
4) Dopamine: motor control/cognition/arousal
5) Norepinephrine/noradrenaline (NE): arousal, fight-flight
6) Serotonin: mood/cognition
Where is dopamine produced and what can a lack of it cause?
Substantia Nigra + ventral tegmental area (VTA) in midbrain
Lack of it can result in Parkinson, schizophrenia and susceptibility to addiction
Where is noradrenaline/norepinephrine produced?
Locus Coeruleus (LC)
Where is serotonin produced and what can a lack of it cause?
Produced in Raphe nucleus (part of reticular formation in brainstem)
Lack of it can result in depression
What are conditional neurotransmitters?
Neurotransmitters that only acts when other factors are present (e.g. another neurotransmitter)
How are neurotransmitters deactivated after release? Name three ways
- Active reuptake by presynaptic terminal
- Enzymatic breakdown
- Diffusion of transmitter to another region
How does electrical synaptic transmission work, what are the necessary anatomical features and what are the limits of it?
Anatomical structures = gap junctions
Two neurons share the same cytoplasm (isopotential) via these gaps
It is useful for quick communication
Limits:
- Can’t amplify a signal
- Passive conduction
What is the difference between a microcircuit and a macrocircuit?
Micro = connected neurons that process specific kinds of information, such as generating movement
Macro = multiple microcircuits with often long-distance connections between various brain regions
What does corticofugal connections mean?
These are projections extending from central structures (e.g. cortex) to the PNS
What are the two divisions of the PNS?
1) Somatic system (voluntary)
2) Autonomic system (sympathetic (fff) - parasympathetic (rest))
What do these terms mean: dorsal - ventral - caudal - rostral
Dorsal = back
Ventral = belly
Caudal = tail
Rostral = beak
in terms of the brain:
Dorsal = superior = top
Ventral = inferior = bottom
Caudal = posterior = back
Rostral = anterior = front
What do these terms mean: lateral - medial - distal - proximal - ipsilateral - contralateral?
Lateral = toward the side
Medial = toward the middle
Proximal = closeby
Distal = far away
Ipsilateral = on the same side of the body (LL or RR)
Contralateral = on the opposite side of the body (LR or RL)
What are the three different cross-sections of the brain and what do they look like?
1) Sagittal: vertically from nose to back
2) Coronal: vertically from ear to ear
3) Axial: horizontally
What is the difference between nucleus and ganglion? What is the dorsal root ganglion?
Nucleus is bundle of neurons in CNS, ganglion is bundle of neurons in PNS.
The dorsal root ganglion is a combination of sensory neurons near the spine
What is the difference between afferent and efferent communication?
Afferent = toward CNS (sensory)
Efferent = away from CNS (motor)
What is the difference between grey and white matter?
Grey = neurons + cell bodies (outer layer brain, inner part spinal cord)
White = axons, glial cells
- In brain grouped in association tracts and projection tracts
- In spinal cord the outer part
- Commissures = bundles of axons (e.g. corpus callosum)
How is the brain protected? Name at least the three meninges
From outside to inside:
1) Skull
2) Meninges:
- Dura mater = thick
- Arachnoid mater
- (subarachnoid space with CSF = reduces shock, cleans brain)
- Pia mater (infection = meningitis)
3) Brain
What are ventricles and how are the connections between them called
Ventricles contain CSF
- First/second Lateral ventrical (right and left)
- Caudal third ventricle
- Fourth ventricle near brainstem
Lateral - caudal connection = interventricular foramen
Caudal - fourth connection = cerebral aqueduct
Eventually all moving down spinal cord
What are the two sources of blood in the brain?
1) Internal carotid arteries
2) Vertebral arteries (in spine and becomes basilar artery in caudal portion of brain)
What is the circle of Willis?
A circular structure of arteries that combines the internal carotid arteries and the basilar artery (from vertebral arteries)
What are the 4 main parts of the CNS?
1) Spinal cord
2) Brainstem + cerebellum
3) Diencephalon (thalamus, hypothalamus)
4) Telencephalon/cerebrum (limbic system, basal ganglia, cortex)
What are the dorsal and ventral horn?
Located in spinal cord
- Dorsal = sensory input enters (afferent)
- Ventral = motor output leaves (efferent)
What are the 4 parts of the brainstem?
1) Medulla
2) Pons + cerebellum
3) Midbrain
4) Reticular formation
What is the function of the Medulla?
Pyramidal decussation = crossing of motor axons (left brain to right body)
Autonomic functions –> heart rate, sneezing, blood pressure
What is the function of the Pons?
Bridge from forebrain to cerebellum
Contains nuclei for sleep, swallowing, facial expressions
What is the function of the cerebellum?
Motor control, balance, cognitive processing
70 billion neurons, but not enough studied
What is the function of the midbrain?
Dorsal part = tectum
- Superior and inferior colliculi combine visual, auditive and tactile information
Ventral part = tegmentum
- Contains substantia nigra + VTA –> Dopamine
- Periaqueductal grey = pain signal modulation
What is the function of the reticular formation?
- Arousal and attention
- Raphe nuclei –> Serotonin
What is the function of the Thalamus and what are the functions of the 4 main nuclei?
Switch board of the brain and receives input from all sensory areas except olfaction
Main nuclei:
1) LGN: vision
2) MGN: audition
3) VPN: somatosensation
4) Pulvinar: attention
What is the massa intermedia?
This connects both sides of the thalamus and is a bridge of grey matter
What is the function of the hypothalamus?
Homeostasis (temperature, metabolism rate, day/night cycle (circadian rhythm)
Production hormones or control of production in for example pituitary gland
What are the three main parts of the limbic system?
- Hippocampus: spatial processing, memory
- Amygdala: emotions, fear
- Cingulate cortex (CC)
What is the function of the basal ganglia? (Neostriatum, Globus pallidus, Nucleus accumbens)
- Movement memory
- Neostriatum: putamen + caudate nucleus (learning, memory, rewards)
- Globus pallidus (position body)
- Nucleus accumbens (dopamine, motivatie)
What are the four different lobes of the brain? What are some of their functions?
Frontal: executive functions + motor control
Parietal: somatosensation + unimodal association area (S2)
Temporal: audition
Occipital: vision
Where are the following structures:
- Lateral silvian fissure
- central sulcus
- Preoccipital notch
- Longitudinal fissure
- Lateral sylvian: between frontal and temporal
- Central sulcus: between frontal and parietal
- Preoccipital notch: between occipital and temporal
- Longitudinal fissure: between both hemispheres
What is the function of the precentral and postcentral gyrus?
Precentral = primary motor cortex
Postcentral = primary somatosensory cortex
What is the structure of neocortex? How does that compare to older evolutionary parts?
Neocortex has 6 layers of grey matter, organized in microcolumns
Evolutionary older parts have less layers and are called paleocortex
What are the 5 main divisions of the cerebral cortex concerning function?
1) Primary sensory
2) Primary motor
3) Unimodal association
4) Multimodal association
5) Paralimbic/limbic areas (between limbic area and cortex)
What can be found in the paralimbic areas?
Olfactorcentric formation, hippocampocentric formation
How does the brain develop?
- Synaptogenesis –> formation of synapses
- Synaptic pruning –> use it or lose it!
- Growth dendritic trees
- Extension of axons
- Myelination of glial cells
- Gray matter loss when maturing
IMPORTANT: neuron amount doesn’t increase
Where is neurogenesis possible?
In hippocampus and olfactory bulb –> Memory!
