Neuro midterm

What is the nervous system

Coordinates actions by transmitting signals to and from different parts of the body. Detects and responds to environmental changes divided into the central nervous system and the peripheral nervous system.

What are the divisions of the central nervous system

The brain and spinal cord

What are the divisions of the peripheral nervous system

1. Somatic nervous system

2. Autonomic nervous system

What are the divisions of the somatic nervous system

Cranial nerves and spinal nerves

What are the divisions of the autonomic nervous system

1. Sympathetic division (activating)

2. Parasympathetic division (calming)

Define cranial nerves

12 pairs of nerves that control afferent functions (sensations to eyes, ears and nose) and/ or efferent functions (motor controls to face, tongue and eyes). Influences several autonomic responses by Connecting brain and internal organs

What is the name of the cranial nerve that deals with smell

Olfactory

What is the name of the cranial nerve that deals with vision

Optic

What is the name of the cranial nerve that deals with eye movement

Oculomotor, Abducens and Trochlear

What is the name of the cranial nerve that deals with masticatory movements and facial sensations

Trigeminal

What is the name of the cranial nerve that deals with facial movements And sensations

Facial

What are spinal nerves

They are functionally equivalent to the cranial nerves of the head; control and carry information about the body, trunk and limbs. Bilaterally symmetrical

What are the spinal nerve connections

Dorsal fibers → afferent

Ventral fibers → efferent

What is the pathway of the spinal cord

1. Fibers entering the dorsal root boring sensory info from sensory receptors

2. Fibers leaving the ventral root carry motor info to the muscles

3. Collateral branches of sensory neurons may cross to the other side to influence motor neurons there

4. White matter fibber tracts carry info to and from the brain

What directions are ventral and dorsal

Dorsal is up and ventral is down

What is a root in terms of fibers

A collection of fibers entering and exiting the spinal cord segment

What is the sympathetic division

• fight or flight

• Connected to thoracic and lumbar spinal cord regions

• Spinal cord connects to autonomic control center, made up of ganglia

What is the parasympathetic division

• rest and digest

• Connects through cranial nerves 3,7 and 10 (eye movement, facial movements and heart)

• Connected to sacral region of spinal cord

What are vertebrae

Segements of the spinal cord; divided into 5 regions:

1. Cranial

2. Cervical

3. Thoracic

4. Lum

5. Sacral

   From top to bottom

What are dermatomes

Segements of the body, each dermatomes contain sensory and motor nerves

What is the spinal cord

• controls most of the body movements

• Contains vertebrae and dermatomes

• Can act independently on the brain (spinal reflex and automatic movements)

What are the layers that protect the brain

1. Skin

2. Aponeurosis

3. Periosteum

4. Bone

5. Meninges

   1. Dura mater

   2. Arachnoid

   3. Pia mater

What is dura mater

Tough double layered tissue, encloses brain and spinal cord

What is the arachnid layer

Thin sheet of delicate connective tissue that follows the brain’s contour and creates space for CSF

What is Pia mater

Moderately tough membrane fo connective tissue that clings to the brain’s surface

What is meningitis

Bacterial infection of the meninges particularly the Pia mater and arachnoid as well as CSF. The inflammations puts pressure on the brain and leads to drowsiness and/or coma

What are the lobes of the brain

1. Frontal lobe (motor function, decision making…)

2. Parietal lobe (sensory and motor info processing)

3. Occipital lobe (vison)

4. Temporal (auditory, emotion, memory)

What is the cerebrum

• forebrain structure With 2 identical hemispheres

• Responsible for most conscious behaviours

What is the cerebellum

• control and coordination of small motor skills

• Does not initiate movement but coordinates the timing, precision and accuracy of movements

What is the brainstem

• responsible for unconscious behaviours

• Structurally continuous with spinal cord.

• Receives afferent nerves form the body and sends efferent nerves to the spinal cord

• Divided into 3 regions: Hindbrain, Midbrain and Diencephalon

Wat is gyri and sulci

Gyri: bumps and ridges of the cerebral cortex

Sulci: cracks and grooves of the cerebral cortex

What does larger surface area in the brain equate to

Greater cognitive function

What are cerebral arteries

• 3 major arteries supply the cerebrum (Anterior, middle and posterior cerebral aretiries)

• Blockage of any of these leaders to regional death = stroke

What is gray matter and white matter

• grey matter: composed of cell bodies and capillary blood vessels. Process information and supports behaviour

• White matter: nerve fibers with fatty coverings. Form connections between cells

What are ventricles

4 cavities filled with CSF. 3 main functions:

1. Buoyancy

2. Cushioning

3. Immune support

What are ependymal cells

Cells that line the walls the ventricles and produce CSF

What is the corpus callosum

• 200 million nerves fibers that connect the 2 hemispheres of the cerebrum

• Divide the Brian into cortical and sub cortical regions

What is part of the hindbrain

• cerebellum: controls motor movements

• Pons: connects cerebellum to rest of brain

• Reticular formation: mixture of grey and white matter at core of brainstem

• Medulla: controls breathing and cardiovascular system

What is part of the midbrain

• tectum: receives sensory info from eyes and ears and allows production of reflexes

• Tegmentum: composed of red nuclei (motor coordination of limbs), substantia nitrate (initiates voluntary movements), and periaqueductal grey matter (sexual behaviour and pain)

What is part of the diencephalon

Hypothalamus: controls hormone production, influences sexual behaviour, feeding emotions…

Thalamus: relay station for sensory info travelling to cortex (all sensory info need input from thalamus)

What is the forebrain

• largest and most recently evolves

• Controls perception, planning and movements

• Divided into 4 parts:

  • Neocortex

  • Basal ganglia

  • Allocortex

  • Olfactory system

What is the basal ganglia

Collection of nuclei that control certain aspects of voluntary movements.

What makes up the Allocortex

• hippocampus: memory storage (special memories)

• Amygdala: emotion regulation, fear acquisition and memory enhancement

• Cingulate cortex: helps certain aspects of memory formation and recollection

What makes up the olfactory system

Olfactory bulbs (forebrain structure): allows sense of smell, sends sensory info directly to pyriform cortex. Relatively small in humans

What are the 2 major cell types of the nervous system

1. Neurons: carry out brain’s major functions

2. Glial Cells: provide insulation, nutrients and support to all neurons. Neuron’s parents

What are the parts of a neuron

1. Soma: core region, process information

2. Dendrites: branching extension, receives information (#of dendrites = amount of incoming info)

3. Axon hillock: point at which the axon leaves the soma

4. Axon: caries info to other neurons

5. Myelin sheath: insulate axons for faster signal travelling

6. Axon collateral: point where axon branches out

7. Terminal button

8. Synapse: junction between one neuron and the other

What are the different types of neurons

1. Sensory neurons: brings info to the brain (afferent)

2. Interneurons: associate sensory and motor neurons (branches more to collect more info)

3. Motor neurons: carry info from brain to spinal cord (efferent)

What are the subtypes of sensory neurons

1. Unipolar: single dendrite on one side and cell body on the other

2. Bipolar: sensory receptor on one side, dendrites on the other and cell body in the middle

3. Multipolar: dendrites on both sides and cell body on one extreme

What are the subtypes of interneurons

1. Stellate cell (star shaped): Very small, many dendrites extending around entire cell
   body.

2. Pyramidal cell (pyramid shaped): Long axon with multiple sets of dendrites.

3. Purkinje cell: Output cell; Extremely branched dendrites.

What are the subtypes of glial cell and their roles

1. Ependymal cell – located on walls of ventricles, produce CSF;

2. Astrocyte – provides structural support, regulates blood brain barrier;

3. Microglia – immune function, engulf foreign substances;

4. Oligodendrocytes – insulates axons in the CNS;

5. Schwann cell – insulates axons in the PNS.

What is the role of microglia and Schwann cells

They play a role in repairing damaged neurons in the PNS:
- Microglia remove debris;
- Schwann cells form path for new axons to follow & insulate new axons.

Repair is less common in CNS

How do Axons transmit info

Axons tend to project in bundles
- Nerve when outside the CNS;
- Tract within the CNS.

What are the steps of neurotransmission

1. Electrical;

2. Chemical.

What is a membrane potential

• each neuron has a restin membrane potential. (-70mV)

• This occurs because the inside of the cell is negatively charged, relative to the outside of the cell.
  - Large negatively charged proteins (A-) – inside;
  - Sodium ions (Na+) – outside;
  - Potassium ions (K+) - inside;
  - Chloride ions (Cl-) – outside

How do cells maintain the resting potential

They rely on sodium-potassium pumps to keep this balance.
- Exchanges 3 Na+ (outbound) for 2 K+ (inbound);
- Use up ~2/3 of a cell's energy expenditure.

What are electrochemical gradients

Determines ion movement direction through a membrane based on voltage and concentration gradients. Salt (Na+ and Cl-) dissolves in water. Impermeable membrane = even distribution; pores for Cl- create an electrical potential difference.

What is hyper polarization

membrane potential is exaggerated, so difference between inside and outside are greater; cell is more negative

What is Depolarization

membrane potential is diminished, so difference between inside and outside are lessened. Cell is more positive

How can membrane potentials change?

Channels and pores on the cell membrane allow ions in and out. Different stimuli open specific pores/channels, enabling ion movement.

What is an action potential

A brief, large reversal in axon membrane polarity where the inside becomes positive relative to the outside. This is reversed by K+ outflow, restoring the resting membrane potential (-70mV).

What are the inputs that neurons receive

Excitatory post-synaptic potentials (EPSP)
• Inhibitory post-synaptic potentials (IPSP)

How is the action potential initiated

Once EPSP sum to -50mV (Threshold Potential), an action potential (AP) occurs. It’s an all-or-nothing response, continuing until the cell reaches ~+30mV. At -50mV, Na+ influx happens as channels open, and K+ exits the cell.

Hat are the 7 main parts of the action potential

1.Stimulus
2. Threshold (-50mV)
3. Depolarization (influx Na+)
4. Peak (+30mV)
5. Repolarization (K+ efflux)
6. Refractory period (relative refractory)
7. Return to resting state

What are nodes of Ranvier

Myelin around axons form nodes

What are neurotransmitter

chemical released by nerve cells
• Can be excitatory or inhibitory

how is this info passed to the next cell?

Through chemical transmission:

Chemical transmission occurs through the release of neurotransmitters (NT) into the synaptic cleft (space between two terminals).

What are the 4 main criteria for a molecule to be a neurotransmitter

The 4 main criteria for a molecule to be classified as a neurotransmitter (NT) are:

1. It must be synthesized or present in the neuron.

2. It must be released when the neuron is active and produce a response in a target.

3. The same response must occur when the transmitter is placed on the target experimentally.

4. A mechanism must exist to remove the transmitter after its action is complete.

What are the types of NT

Monoamine: Dopamine (DA), norepinephrine (NE), epinephrine, serotonin (5-HT),

Amino Acid: GABA, glutamate, glycine,

Peptide: Somatostatin, Substance P, etc.

Gases: Nitric oxide, carbon monoxide

What are the main components of chemical transmission

Vesicle → storage of NT
• Synaptic cleft → space between button and spine
• Post-synaptic receptor → binding side of NT

4 Steps of Chemical Transmission

Synthesis: Produced from DNA/mRNA and stored in vesicles in the axon terminal.

Release: Transported to the pre-synaptic membrane and released in response to an action potential.

Receptor Action: Activates target receptors on the post-synaptic membrane, exciting or inhibiting the post-synaptic cell depending on the receptor.

Inactivation: Must be inactivated to prevent continuous stimulation or inhibition; inactivation methods include:

• i) glial cell uptake,

• ii) enzymatic degradation,

• iii) diffusion,

• iv) reuptake.

What parts of thr nervous system is present in vertebrae embryos

1.Forebrain
2. Midbrain
3. Hindbrain
• Remainder of the neural tube = spinal
cord

What are the stages of human neural development

• Day 1: Fertilization, zygote is a single cell.

• Day 2: Cells begin to divide.

• Day 15: Embryonic disc forms several layers.

• Day 18-21: Formation of neural plate and groove.

• Day 22-24: Neural tube forms from the neural plate.

• After 3 weeks: Rapid changes.

• Day 49 (7 weeks): Embryo starts resembling a person.

• Day 100 (14 weeks): Brain begins resembling a human.

• ~7 months: Formation of gyri and sulci.

• ~9 months: Full human brain with a very different cellular structure.

What are neural stem cells

• The cells that line the ventricle

• Area along ventricles with NSCs = Subventricular zone (SVZ) → found throughout our life

How do neural stem cells reproduce

NSCs continuously regenerate by dividing into 2
• One cell dies, the other lives
• The living cells can then give rise to progenitor cells

What are progenitor cells

Progenitor cells (precursor cells) can divide and eventually form non-dividing cells.

Hat are neuroblast and glioblast

Neuroblast: Will eventually form neurons.

Glioblast: Will eventually form glial cells.

What do our brains rely on to form neurons and glia

Our brains rely on a complex mix of chemical and genetic signals during development to form neurons and glial cells.

What are the 3 main signals influencing stem cells production and differentiation

Prolactin: A hormone that increases during pregnancy, boosting fetal neural stem cell production.

Gene Transcription: Genes are turned on through transcription, influencing stem cell fate

Epigenetics: Controls which genes are activated. DNA methylation adds a methyl group to turn genes off. occurs frequently during development and in response to environmental signals

What are Neurotrophic Factors

Compounds that influence the differentiation of NSCs

What are 2 main factors discovered so far that influence NSC fate

1. Epidermal growth factor (EGF) – stimulates NSCs to turn into progenitor cells

2. Basic fibroblast growth factor (bFGF) – stimulates progenitors into neuroblasts (young neurons)

What determines the type of neuron a neuroblast becomes?

The neuroblast becomes any type of neuron depending on its environment, influenced by other neurotrophic factors

What are the stages of neural/glia growth

Cell Birth: Neurogenesis and gliogenesis.

Cell Migration: Cells travel to their final destination.

Cell Differentiation: Development of specific tools/skill sets.

Cell Maturation: Dendritic development and axonal growth.

Synaptogenesis: Formation of synapses.

Cell Death: Apoptosis/pruning.

Myelogenesis: Formation of the myelin sheath.

When does cell migration occur

At 6 weeks

What restricts the type of cells that are formed

Intracellular (between cells) signals

What 3 things do the emergence of a cell type in a specific area depend on

1. Genetic expression

2. Timing

3. Signals found in the local environment

What are the 2 parts that new neurons need to function

1. Dendrites: provide surface area for synapse formation (slow)

2. Axon:extend to the target area to make contact with other neurons (fast)

What are growth cones and Filopods

Growth Cones: extensions of developing axons, first described over 100 years ago.

Filopodia: shoots that extend from the growth cone. If they reach a target (e.g., dendrite), the rest of the growth cone follows, completing the axon.

What do the movement of growth cones depends on

Cell-Adhesion Molecules (CAMs): Located on cells or in the intracellular space, provide surfaces for growth cones to attach to.

Tropic Molecules: Secreted by target cells to attract or repel growth cones.

• Netrin: Attracts the growth cone toward a cell.

• Semaphorins: Repel growth cones

What happens to synapses after birth

After birth, the number of synapses increases drastically, doubling between 2-4 months, especially in the visual cortex.

What happens to synapses from childhood to adulthood

There is about a 40% loss of synapses from childhood to adulthood. This loss is due to Neural Darwinism, where competition for limited resources results in only the synapses best suited to the environment surviving.

What is Nerve Growth Factor (NGF)

a neurotrophic factor produced by cells that helps regulate neuronal survival. It is made by cortical cells and absorbed by cholinergic cells in the basal forebrain.

What is the last process known to occur during deleopment

Myelination - Myelin in the CNS is formed by oligodendrocytes and continues to develop throughout life. Myelination occurs at different rates in various areas of the cortex.

What is Neuroplasticity

the process where the brain is shaped by experience.

Donald Hebb (1947) Experiments with Rats

Provided early biological evidence of environmental impact on brain development.

Raised rats at home, exposing them to various experiences (e.g., chased by his wife with a broomstick).

Control group stayed in the lab with limited experiences.

Home rats performed better in maze tasks than lab rats.

Conclusion: Enriching experiences influence intellectual development.

What is fragile X syndrome

• Martin-Bell Syndrome

• The most prevalent inherited neurodevelopmental disorder

• causes developmental delays and intellectual disability.

• The disorder is due to mutations in the (FMR1) gene, an X-linked gene (X-chromosome appears broken)

What is the epidemiology of Fragile X

Biological males and females affected but males are more severe (only one X chromosome)

Typically noticeable by parents in first 12-16 months
• Strong comorbidity with ASD (4 in 10)

Clinical Features of Fragile X

Mild to severe intellectual disability

Altered physical characteristics

Behavioral, social, and emotional challenges

Speech and language issues

Sensory problems

What are intelligence and learning features of fragile X

Symptoms range from mild to severe, including learning disorders to intellectual disability

Females typically have mild deficits or normal intelligence

Low IQ that worsens with age, possibly due to attentional issues

Delay in certain intellectual milestones

What are some physical characteristics of Fragile X

Long, narrow face with large forehead/jaw and pointy ears

High palate leading to tooth crowding

Flat feet

Extreme joint flexibility

Macro-orchidism (in males during/after puberty)

Most physical features become visible during puberty

What are some behavioural symptoms of Fragile X

• Anxiety in new situations, which may lead to lashing out

• Difficulty making eye contact

• Males often have attentional issues and/or aggression

• Females, especially, tend to have social anxiety

• Flapping or biting hands in social situations