Brain Anatomy & Neural Communication Flashcards
1
Q
Name the terms used to describe the brain’s exterior
A
- Rostral (anterior) → Toward the beak - Jaw, front
- Caudal (posterior) → Toward the tail - Back of head
- Dorsal (superior) → Toward the back - Bottom of head
- Ventral (inferior) → Toward the belly
-
Neural axes → Imaginary line through spinal cord toward front of brain
- Human = Bends because head if perpendicular to the back
Imagine brain as dog
2
Q
Name the neural planes
A
- Lateral → Toward the side
- Medial → Toward the midline (centre)
- Ipsilateral → Same side of midline
- Contralateral → Opposite side of midline
3
Q
Describe the corpus callosum
A
- Large bundle of axons that connect the two hemispheres
- Homotopic → Connects complementary region of other hemisphere
- Heterotopic → Different brain regions
- Ipsilateral → Same side
4
Q
Describe cranial nerves
A
-
12 pairs attached to the ventral surface of the brain
- Tenth → Vagus nerve = Connect to ENS
- Efferent (motor) and afferent (sensory) fibers
5
Q
Describe the telecephalon
Tele = At a distance (from…)
A
- Subdivision of forebrain
- Limbic system
- Basal ganglia
- Cerebral cortex - Largest structure of human brain
- Inner = White Matter
- Outer = Grey Matter
6
Q
Describe spinal nerves
A
- Begin at junction of the dorsal and ventral roots of the spinal cord
- Leave ventral column and travel to muscles or sensory receptors
- Branch repeatedly → Follow blood vessels
-
Afferent axons
- Sensory into CNS
- Located outside CNS
-
Somatosensory axons
- In dorsal root ganglia
- One limb each to spinal cord, sensory organ
-
Efferent axons
- Away from CNS
- Give rise to ventral root
- Located in gray matter of the spinal cord
- Leave through ventral roots to make spinal nerve
- Muscles and glands
7
Q
Why is white matter pale?
A
- High proportion of axon fibres covered in fatty myelin layer
8
Q
Describe the basal ganglia
A
- Nuclei responsible for controlling involuntary movement → Automatised
-
Dysfunctional for Parkinson’s disease
- Tremors, poor balance
9
Q
Describe the limbic system (5)
A
- Consists of…
- Hypothalamus
- Thalamus
- Hippocampus
- Amygdala
- Some nuclei of basal ganglia
10
Q
Describe the parasympathetic division of the ANS
A
- Calming → Restore energy
- Dominates in ‘rest and digest’ mode
-
Neurons located…
- Nuclei of some cranial nerves
- Intermediate horn of the gray matter in the sacral region of the spinal cord
11
Q
What is the diencephalon?
Di = Double
A
-
Thalamus
- Relay station for sensory inputs to cerebral cortex
- Several nuclei
-
Hypothalamus
- Autonomic system
- Endocrine (hormone) system
- Survival behaviours
12
Q
What is the mesencephalon?
Mes = Middle
A
-
Midbrain
- Topmost region of brainstem
- Directly above hindbrain
- Connects pons and cerebellum with forebrain
- Important for motor movement → Eye, auditory and visual processing
13
Q
What is the metencephalon?
Met = Behind
A
- Hindbrain
-
Cerebellum
- Little brain
- Information from visual, auditory, somatosensory and vestibular (balance) systems
- Coordination of movement
-
Pons
- Ventral surface of brainstem
- Several nuclei → Sleep and arousal
- Relay information from cerebral cortex to cerebellum
-
Cerebellum
14
Q
What happens when the cerebellum is damaged?
A
- Problems with walking
- Jerky, poorly coordinated movements
- Problems maintaining balance
15
Q
What is the difference between the basal ganglia and the cerebellum?
Important!
A
- Basal ganglia
- Habit → Hard to change
- Things that are learnings e.g. Piano
- Cerebellum
- Movements that are different depending on the situation
- Integrate new visual and auditory information
16
Q
What is the myelencephalon?
Myel = Marrow, spinal cord
A
-
Medulla oblongata
- Links hindbrain to spinal cord
- Neurons important for autonomic functions → Respiration and heart rate
17
Q
Name the lobes of the brain in order (front (top) to back to (bottom) front)
Include Sulci and Notch
A
- Frontal
- Central sulcus
- Parietal
- Parieto-occipital sulcus
- Occipital
- Pre-occipital notch
- Temporal
18
Q
Describe the primary visual cortex
A
- Medial and lateral parts of the occipital lobe
- Sensory information from retina
- Left and right field projected into contralateral (opposite) hemisphere
- Light stimulus stimulates corresponding area of retina within each eye (left and right of respective eyes - split in half)
- Different regions of retina represented by different areas in PVC
- Further away = Area of PVC further towards back of head (calcarine fissure)
- More neurons dedicated to central vision - Rather than peripheral (extend arm out = thumb distance)
19
Q
Describe the parietal lobe
A
-
Attention and spatial awareness
-
Dorsal surface of cortex = Part of dorsal stream
- “Where” pathway for role in spatial
-
Dorsal surface of cortex = Part of dorsal stream
20
Q
Describe the temporal lobe
A
- Auditory processing
-
Ventral surface of cortex → Ventral stream
- “What” pathway for spatial
- Complex visual processing → Faces and complex object recognition
21
Q
Describe the primary auditory cortex
A
- Superior part of temporal cortex
- Patch of cortex buried in Sylvian fissure
- Receives auditory sensory information from cochlea (inner ear → hearing)
- Different frequencies represented by different areas = Tonotopic map
22
Q
Describe the primary somatosensory cortex
A
- Immediately posterior to central sulcus (between frontal and parietal)
- Sensory information from skin
- Different regions of skin surface represented by different areas = Somatotopic Map
Posterior = Behind
23
Q
Describe the primary motor cortex
A
- Precentral gyrus → Immediately anterior to central sulcus
- Different parts send signals that control different groups of voluntary muscles
- Controls muscles on contralateral (opposite) side of the body
Anterior = In front of
24
Q
Describe the frontal lobe
A
-
Higher order functions
- Voluntary
- Impulse control and emotion regulation
- Abstract reasoning and planning
25
How does the human frontal lobe compare to other animals?
* **Larger** than **non primates**
* **Higher level of connectivity** with **rest of the brain** compared to **apes**
26
Describe the case of Phineas Gage
* **Frontal lobe damage** → **Pole** through
* Behavioural changes
* **Personality** changed
* **Bad temper**
* **Unable to plan**
* **Not employable in old job** → Now jobs where he **did not make decisions**
27
Name and draw the features of a neuron (top to bottom, 7)
* **Dendrite**
* Dendritic spines
* **Soma** (cell body)
* **Axon**
* *Myelin sheath* (over axon)
* **Axon terminals**
* Terminal buttons
28
Describe action potentials
* Caused by **changes in flow of ions** (charged molecules) across **neuron's cell membrane**
* Change **membrane potential**
* ***Rest = Polarised at -70mV***
* *Positive (Na+) ions* → **Depolarise -70mV to 0mV**
* ***AP = -50mV***
* Finish → **Hyperpolarised refractory period**
* **Further from threshold of activation**
* ***Less likely to trigger AP* until returned to resting potential of -70mV**
## Footnote
Beginning = Extracellular space with Na+ (sodium) and CI- (chloride)
Cytoplasm = K+ (Potassium)
29
What is membrane potential?
* **Difference between charges** of...
* **Cytoplasm**
* **Extracellular space**
* Resting does not have to remain fixed during signal transmission
30
Describe the process of depolarisation (5)
1. **Sodium (Na+) channels open**
2. Na+ ions **flow rapidly into neuron**
3. Positive ions = **Increase charge**
4. **Rapidly reduce membrane potential** (difference in charge between inside and outside of neuron)
5. **Inside more *positive*** than outside
31
What happens if there is sufficient sodium (Na+) to bring the membrane potential beyond -50mV?
* **Potassium (K+) channels open**
* Allow **K+ to leave neuron**
* **Na+ still entering** cell = **Continue depolarising**
32
Describe the refractory period
* **1msec after K+ leave** neuron
* **Action potential = Peak**
* **Sodium channels = Refractory (closed channels)**
* Charge is **+40mV**
* **More positive inside** than outside
* **Cannot open again until return to resting**
* **No further Na+ enter**
* **K+** channels still open = **Continue exit**
* Charge **increasingly negative**
33
Describe hyperpolarisation
* **K+ channels closing** = Membrane **more negative until *extra K+ diffuses***
* **Subsequent action potential** will require **greater Na+ influx**
* Because **membrane potential further (more negative) from threshold of excitation**
* **Inside more *negative*** than outside
34
Where are ions able to follow in and out of the neural membrane?
* **Inbetween myelin gaps**
* Allows **AP** to travel down neuron **faster**
35
What is the rate law of action potentials?
* Neuron firing = **All or none**
* **Frequency** determines **strength of neural signal**
* Doesn't get smaller or bigger
* Only frequency changes
* **Strong** stimulus → **Faster threshold for activation** → **More frequent AP**
* **Reaches AP (+40mV) faster**
36
Describe the all-or-none law
* An action potential either **occurs or does not occur**
* Once **triggered**, it is **transmitted down the axon to its end**
* **Exact same size**, without growing or diminishing
* **Even at branches**, only *splits* but **does not shrink**
37
Describe the rate law
* Principle that **variations in the intensity of a stimulus** or other information are **represented by variations in the rate which the axon fires**
38
What is diffusion?
* **Molecules distribute themselves evenly** throughout the medium in which they are dissolved
* From **high to low concentration**
39
What is the force of electrostatic pressure?
* Force from **attraction** (Cation and Anion)
* Force from **repulsion** (Cation x2 or Anion x2)
* **Moves ions from place to place**
* ***Away* from *excess* of molecules with *same charge***
40
What is the reasoning behind electrostatic pressure?
* **Electrolyte dissolve in water** → Split into **2 particles** (ions)
* Each with **opposing charges**
* **Cation Ion +**
* **Anion Ion -**
41
Describe the ions within intracellular and extracellular fluid organically
* **Intracellular**
* **Potassium (K+)**
* Concentrated and **pushed out** (diffusion)
* **Outside** is charged **positively** = **Keep inside cell to balance** (ESP)
* **Organic anions -**
* *Cannot leave cell*
* **Extracellular**
* **Sodium (Na+)**
* **Greater concentration outside = Push in** (diffusion)
* **Negative charge inside attracts** positive Na+ (ESP)
* **Chloride (CI-)**
* **Greater concentration outside = Push in** (diffusion)
* **Inside is charged negatively = Push out to balance** (ESP)
42
What is the sodium-potassium pump?
* *Diffusion and ESP attracting Na+ in*... **SPP keeps it outside**
* **Exchange Na+ for K+**
* Push **out 3 sodium for every 2 potassium** pushed in
43
What are the nodes of Ranvier?
* **Gaps inbetween myelin sheath** on the axon of a myelinated neuron
* **Only contact between cell and extracellular fluid**
44
Describe the structure of a synapse
* Enable communication between neurons
* **Terminal button**
* **Synaptic cleft** (gap between neurons)
* **Pre & post synaptic** membrane
* **Synaptic vesicles**
45
What are neurotransmitters?
* Chemicals synthesised within neurons
* **Chemical messengers**
* **AP stops at end of axon** = **Presynaptic neuron can only influence postsynaptic** through **release of NT across synapse**
46
State the steps of neurotransmission (4)
1. **AP in presynaptic triggers synaptic vesicles to move toward cell membrane**
2. **Fusion** of two membranes
3. **NT molecules released**
4. NT flows into **synaptic cleft**
* **Bind to receptors on postsynaptic** membrane
## Footnote
Voltage dependent calcium channels
Depolarisation → Opens channels
47
Describe the role of calcium in neurotransmission
* Membrane has **voltage dependent calcium channels**
* **Depolarisation opens channels**
* Causes **calcium** (Ca^2+) to **flow in via diffusion and ESP**
* Calcium **binds with protein molecules** that **join the membrane of synaptic vesicles with the presynaptic membrane**
* Segments of clusters of **protein molecules move apart**
* Creates **hole through both membranes that enables them to fuse (fusion pore)**
48
What is docking?
* Clusters of **protein molecules attach to other protein molecules** located in the **presynaptic** membrane
* **Vesicles become docked against presynaptic** membrane
49
What are the 3 types of synaptic vesicles and their uses?
1. **Release-ready**
* **Docked** against inside of presynaptic membrane
* **Ready to release when AP arrives**
2. **Recycling pool**
3. **Reserve pool**
* Uses
* **Low firing in axon → Only release-ready**
* **High firing in axon → Recycling pool then reserve**
50
What is neurotransmitter reuptake?
* **Synapse recycling and reusing NT molecules after release**
* Reabsorption = **(Bulk) Endocytosis**
51
What are the 3 things that can happen to vesicles after they release neurotransmitters?
1. **Kiss and run**
* **Release most or all** of their neurotransmitter
* **Fusion pore closes**
* **Vesicle breaks away from presynaptic** membrane
* Gets **filled with neurotransmitter** again
2. **Merge**
* **Merge** with **presynaptic membrane**
* **Pinch off into cytoplasm** to **become vesicles**
* **Proteins and neurotransmitter inserted**
3. **Recycle**
* **Reserve pool → Recycled with *bulk endocytosis***
* **Large pieces** of **terminal button** membrane **fold inward**
* **Break off**
* **Enter cytoplasm**
* **New vesicles** formed
52
What are postsynaptic potentials?
* **After presynaptic chemicals received** from across the synapse
* **Neurotransmitters** then **produce postsynaptic potentials** → **Brief de/hyperpolarizations**
* **In/decrease rate of firing of axon** of **postsynaptic** neuron
53
Describe neural excitation (EPSP)
* **Excitatory postsynaptic potentials** (EPSPs)
* **Depolarise postsynaptic** cell membrane
* **Increase likelihood that AP will be triggered in postsynaptic** neuron
* Primary excitatory
* Glutamate
## Footnote
PSA : Neurons can only release either inhibitory or excitatory
54
Describe neural inhibition (IPSP)
* **Inhibitory postsynaptic potentials** (IPSPs)
* **Hyperpolarise postsynaptic** cell membrane
* **Decrease likelihood that AP will be triggered**
* Primary inhibitory NT
* Gamma aminobutyric acid (GABA)
55
What is neural integration?
* **Combined effect of EPSPs and IPSPs**
* Neuron **will only fire if excitatory>inhibitory**
* **Pass threshold of activation**
56
Name 4 neuromodulators
* Dopamine
* Noradrenaline
* Histamine
* Serotonin
57
How does a NT enter the post-synaptic neuron?
* **Attach to binding site of receptor sensitive to specific NT**
* **Lock and key** mechanism
* Receptor **can only be activated by one NT/ drug mimicking NT**
* **Receptors** have **specific function/action**
58
How do drugs activate neural receptors?
* **Mimicking chemical structure of natural compound (NT)**
* Perfectly or partially
* **Agonist**
* Activate
* **Antagonist**
* Block receptor → Prevent natural compound from activating
