NSCI 200 - midterm 1

what are the 2 kinds of cells in the human nervous system?

• neurons

• glia

what are the different qualities a neuron can be classified from?

• shape

• transmitter expression

• direction of information

• gene expression profile

how many neurons and glia does the human brain contain?

• ~ 86 billion individual neurons and glia

what are the compartments of a neuron?

• dendrites

• soma / cell body

• axon

what organelles do neurons contain?

• membrane

• nucleus

  • prominent nucleoli in large neurons

• mitochondria

  • found throughout, many at synapses

• ribosomes

  • abundant in cell body and dendrites

• endoplasmic reticulum

  • rER restricted distribution in mature neurons to cell body and dendrites

• golgi

  • restricted distribution to cell body and dendrites

where are secreted / integral membrane proteins and membrane made?

• in the neuron cell body and dendrites

what is a motor neuron?

• has its soma in the spinal cord

• receives excitation from other neurons

• conducts impulses along its axon to a muscle or gland

what is a sensory neuron?

• specialized at one end to be highly sensitive to a particular type of stimulation

  • touch, light, sound, etc.

how do motor and sensory neurons work in the spinal cord?

motor:

• cell body in spinal cord

• axons excite muscles in the periphery

sensory:

• cell body just outside spinal cord

• axons bring sensory information into the spinal cord from periphery

what are dendrites?

• branching fibres with a surface lined with synaptic receptors responsible for bringing information into the neuron

• some contain dendritic spines that further branch out and increase surface area

  • greater the surface area of a dendrite, the more information it can receive

  • contain numerous proteins in their plasma membrane including many types of ion channels

what is an axon?

• thin fiber of neuron responsible for transmitting nerve impulses toward other neurons, organs, or muscles

• may have myelin sheath - insulating material containing interruptions

  • nodes of Ranvier

• presynaptic terminals at the end points of an axon release chemicals to communicate with other neurons

what is an axon hillock and axon initial segment?

axon hillock:

• cone shaped region where cell body transitions to axon

axon initial segment:

• voltage gated channels are concentrated

• axon potentials are generated

• important for sorting organelles, cytoskeleton, and proteins / mRNA

  • acts as a barrier to some proteins and organelles

how does a neuron signal across a synapse (axon terminal) work?

• nerve impulse conducted down axon

• release neurotransmitters at axon terminals

• neurotransmitters excite or inhibit postsynaptic neuron

• high energy demands - mitochondria

what are adhesion proteins at a synapse?

critical for synapse formation and plasticity

• cadherins

• neurexins

• neuroligins

• contactins

what is axon transport and what is it used for?

used to move proteins, vesicles, and mitochondria from the neuron cell body along the microtubule cytoskeleton to the axon synapse

• driving force is molecular motors

• anterograde transport - from cell body

  • kinesin + motor

• retrograde transport - to cell body

  • dynein - motor

how do kinesin move?

• ATP stepping

• utilizes inorganic phosphate binding release and binding to create conformational changes

what are glia?

• structural and nutritional support for neurons

• insulate neurons

  • important for action potential transmission

• remove debris and maintain a functional nervous system

what are the different types of glia?

• astrocytes

• microglia

• oligodendrocytes

• schwann cells

• satellite cells

• radial glia

what are astrocytes?

• support cells of the CNS - most numerous type of glial cell

• end feet surround vessels - help maintain blood-brain barrier

• dilate blood vessels - brings more nutrients into brain areas with heightened activity

• maintain a proper chemical environment

what are oligodendrocytes?

• myelinate axons in the CNS

  • myelination is essential for effective electrical signal propagation

  • each can myelinate multiple axons

what are schwann cells?

• myelinate axons in the PNS

  • each can myelinate 1 axon

what are radial glia?

• guide the migration of neurons during embryonic development

• are stem cells - make neurons and glia

what are microglia?

• remove waste material, viruses, and fungi from brain

• remove dead, dying, or damaged neurons

• mobilize after infection, injury, or disease

• not derived from the brain

what is the myelin sheath?

• myelin is an insulating material made of fats and proteins

  • most abundent protein - proteolipid protein 1 (PLP1)

• aids in the clustering of sodium channels at nodes of Ranvier

what are nodes of Ranvier?

• short unmyelinated sections of an axon

• action potential is regenerated at each node by a chain of positively charged ions pushed along by previous segment

  • high density of sodium channels

what is the process of myelination?

• oligodendrocyte process wraps around axon and underneath itself

• myelin sheath compacts and spreads laterally

how do oligodendrocytes select axons for myelination?

• preferentially myelinate intermediate to large diameter axons

• some axons will express inhibitory cues to suppress myelination

• unclear whether positive cues are necessary

  • in culture, will myelinate glass tubes of the right diameter

what can occur from poor myelination?

mutation in PLP1 gene results in reduced function and poor myelination

• causes severe motor and cognitive delay

• never walk, limited language skills, usually die from respiratory complications by second decade

what is the blood brain-barrier?

a semipermeable vascular barrier that regulates entry of proteins, chemicals, particles, etc. into the brain

• neurons in the brain generally do not regenerate - vitally important for the blood brain barrier to block incoming viruses, bacteria, and other harmful material from entering

• essential to health - can pose difficulty for allowing chemicals such as chemotherapy to pass

what are the components of the blood-brain barrier?

• endothelial cell tight junctions

• basement membrane (extracellular matrix)

• pericytes (blood vessel stem cell)

• astrocytic endfeet

what is the function of the blood-brain barrier?

restricts passage of:

• pathogens, immune cells / antibodies, large or hydrophilic molecules

allows passage of:

• hydrophobic molecules, small non-polar molecules

what is active transport in the brain?

• protein-mediated process that expends energy to pump chemicals from the blood into the brain

  • glucose, certain hormones, amino acids, few vitamins are brought into brain by active transport

what are the energy needs of vertebrate neurons?

• vertebrate neurons depend almost entirely on glucose

  • one of the few nutrients able to pass through blood-brain barrier by active transport

• neurons need a steady supply of oxygen

  • 20% of all oxygen consumed by the body is used in the brain

what are dorsal and ventral anatomical directions?

• dorsal = toward the back, away from the stomach

• ventral = toward the stomach, away from the back

what are lateral and medial anatomical directions?

• lateral = toward the side, away from the midline

• medial = toward the midline, away from the side

what are proximal and distal anatomical directions?

• proximal = located close the the point of origin or attachment

• distal = located more distant from the point of origin or attachment

what are ipsilateral and contralateral anatomical directions?

• ipsilateral = on the same side of the body

• contralateral = on the opposite side of the body

what are rostral and caudal anatomical directions?

• rostal = toward the front of the head, toward the nose

• caudal = toward the back end, toward the tail end

what does the central nervous system (CNS) contain?

• brain

• spinal cord

what does the peripheral nervous system (PNS) contain?

• nerves and ganglia located outside of the CNS

what does the somatic nervous system control?

• voluntary skeletal muscles

• transmits sensory information to the CNS

what does the autonomic nervous system control?

• regulates many involuntary processes - heart rate, blood pressure, secretion of saliva, sweat, tears

• contains sympathetic and parasympathetic nervous systems

  • act on many of the same organs with opposite effects

• contains enteric nervous system

  • regulates many processes of digestion

what is white vs grey matter?

• white matter:

  • composed mainly of myelinated axons and glial cells

• grey matter:

  • composed mainly of neuron cell bodies and dendrites, and glial cells

  • typically organized into layers or nuclei

what are the ventricles?

• four interconnected fluid-filled cavities within the brain

• they connect with the central canal of the spinal cord

• spaces are filled with cerebrospinal fluid (CSF)

what are the meninges?

• membranes that surround the brain and spinal cord

  • pia mater, arachnoid mater, dura mater

• cerebrospinal fluid (CSF) in the subarachnoid space

• contain pain receptors

what can result from injury in the meninges?

• swollen blood vessels can cause migraine headaches

• meningitis = inflammation of the meninges

  • often caused by bacterial or viral infection

  • painful and can be fatal if not treated promptly

what are the major structures of the forebrain?

• cerebral cortex

• hippocampus

• amygdala

• basal ganglia

• olfactory bulb

• basal forebrain

what are the major structures of the midbrain?

• tectum (dorsal region)

  • superior colliculus

  • inferior colliculus

• tegmentum (ventral region)

  • substantia nigra

  • cerebral peduncle

  • ventral tegmental area

what are the major structures of the hindbrain?

• medulla oblongata

• pons

• cerebellum

• fourth ventricle

what is the medulla?

• regulation of many involuntary processes

  • breathing, heart rate, blood pressure, vomiting, cough reflex

• receives input about proprioception and muscle tension → relays to the cerebellum

• contains caudal region of reticular formation

what is the reticular formation?

extends through medulla, pons, and midbrain

• regulation of sleep / wake cycles, circadian rhythm

• coordinating heart rate, blood pressure, respiration

• motor coordination - stabilize posture during movement

• raphe nuclei - produces serotonin

  • outputs affect mood, emotions, perceptions of pain

what are cranial nerves?

• afferent nerves - conduct sensory signals from sensory structures to the CNS

• efferent nerves - conduct signals from the CNS to target tissues

• mixed nerves - contain some afferent and some efferent axons

what is the pons?

• regulates breathing and sleep / wake cycles

• contains locus coeruleus (LC)

  • nucleus which produces norepinephrine

  • plays important role in arousal, attention, memory, and stress response

• contains nuclei for several cranial nerves

• contains part of the reticular formation

• many fibre tracts pass through the pons

  • axons from each half of the brain cross (decussate) to the opposite side of the spinal cord - each side controls muscles on opposite side of body

what is the cerebellum?

• extensively folded - outer cerebellar cortex of grey matter surrounding white matter

  • helps regulate motor movement, balance, and coordination

  • important for shifting attention between auditory and visual stimuli

  • critical for certain types of learning such as forming procedural memories

what is the midbrain tectum superior colliculus?

• processes and integrates visual, auditory, and somatosensory information

• uses this information to coordinate head and eye movements for gaze shifts

• primary integrating center for eye movements

what is the midbrain tectum inferior colliculus?

• processes and integrates input from auditory and somatosensory systems to determine locations of sounds

• may help to filter sounds and initiate wakefulness in response to certain sounds

what is the midbrain tegmentum cerebral peduncle?

• fibre tracts - output from the cerebrum to the pons, medulla, and spinal cord

what is the midbrain tegmentum substantia nigra?

• produces dopamine

• outputs to the basal ganglia contribute to the regulation of initiation of voluntary movement

• involved in spatial learning and reward processing

what is the midbrain tegmentum ventral tegmental area (VTA)?

• contains many neurons that produce dopamine

• controls a variety of behaviours including reward processing, motivation, learning, and memory

what is the brainstem?

• refers to the medulla, pons, and midbrain together