Psych 115 Midterm I Exam Questions
and Correct Answers
Levels of the Brain ✅Social level, organ level, neural system level, brain region level,
circuit level, cellular level, synaptic level, molecular level
CNS and PNS ✅CNS: Central nervous system
Encased in bone
Brain and spinal cord
PNS: Peripheral nervous system
Not encased in bone
Spinal nerves (motor and sensory) enter and leave the spinal cord
Cranial nerves (motor and sensory) enter and leave the brain.
Autonomic nervous system (sympathetic and parasympathetic) control internal organs
How does one visualize a neuron? ✅German neuroanatomists applied aniline dyes
that had been developed for textiles, dyes with a "basic" character. These dyes stained
"Nissl" substance - nucleic acids - and showed a forest of cell bodies (C above: Nissl
stain). Beginning ~1890 Santiago Ramon y Cajal applied a silver stain developed by
Camillo Golgi to individual neurons, revealing that neurons were individual units (A:
Golgi stain). Fluorescent molecule injections give a similar result (B: Neuron injected
with fluorescent dye).
Cells have a Diversity of shapes and sizes ✅
The parts of a neuron ✅1. Dendrite/diversity
Input zone
Receptors for neurotransmitters
Post-synaptic structure
Dendritic spines
2. Cell soma/body (integration zone)
Nucleus
House-keeping
Transcription
Protein synthesis
Golgi apparatus
3. Axon
can be a meter long)
Conduction zone
Axon hillock
, Myelin sheath
Transport
Efferent (away from)
/Afferent (toward)
4. Axon terminal
Output zone
Release of
neurotransmitters
Pre-synaptic ending
The synapse ✅The axon terminal (or bouton) is presynaptic and releases
neurotransmitter in packets contained within synaptic vesicles.
The transmitter diffuses across the synaptic cleft (10-20 nm) to reach postsynaptic
dendritic spines with receptors.
Synaptic cleft: 10-20 nm across
Synapses were first seen using electron microscopes
Dendritic spine is about 1 micron across
Most cells are 10 microns
Axonal transport ✅Anterograde (kinesin)
from cell soma outward
Retrograde (dynein)
from processes back to cell
soma
Anterograde/Orthograde Transport
Retrograde: sending things back to the cell for recycling
Both take place on microtubules, transported by "motor" proteins, walksstep by step
Tract tracing in the CNS ✅We can take advantage of axonal transport to trace
pathways in the brain:
Anterograde labeling uses radioactive molecules taken up by the cell and then
transported to the axon tips. For instance, radioactive amino acids may be taken up at
the cell soma and used to make proteins that are transported to the axon terminal. The
new (target) location of the radioactivity may be visualized by autoradiography.
Retrograde labeling uses horseradish peroxidase (HRP). This protein is taken up in
axon terminals and transported back to the cell body, where it may be visualized
through chemical reactions.
Proteins in synapses may be taken up by the presynaptic cell as a vescicle and
transported in the retrograde direction, back to cell soma that provided the axon
terminal
,Use markers that give you retrograde and anterograde transport to figure out what
connects to what in the brain
Histochemistry: take advantage of activity of enzyme to mark it
Track tracing: trying to figure out what connects to what
Radioactive amino acids are taken up by the cell body then to the anterograde direction
Four types of glia ✅In the central nervous system (CNS)
1. Astrocytes (star-shaped)
K+ homeostasis,
glutamate uptake,
synapse isolation,
feet on capillaries
Glia = glue
Put something between the neurons to make it stuck there, end feet on capillaries,
surround synapse, housekeeping take up potassium so they don't just stay there,
glutamate too
2. Oligodendrocytes - myelin, nodes of Ranvier, short stretches of many axons, multiple
sclerosis provide lipid layer around axons (myelin)
- breaks in myelin (nodes of Ranvier)
3. Microglia - macrophages, immune system, turn into phagocytes to eat up damage
In the peripheral nervous system (PNS)
4. Schwann cells - myelin of one axon; nodes of Ranvier, one schwann cell myelates a
whole axon
The scale of things ✅large motor neurons - 0.1 mm (100 um) diam
small neurons - 10 um diam
dendritic arbor
0.1 mm (100 um) in diameter
10 nm = 1/100 of a um
um > nm
Synapse = 1 um wide
synaptic clef = 10 nm across
neuronal membrane = 5 nm across
Input (cranial nerves, spinal nerves, hormones) ✅Senses in the head (e.g., eyes and
ears) and internal organs enter as some of the 12 pairs of cranial nerves. numbered
from rostral (front) to caudal (tail)
(DO NOT MEMORIZE.)
Some examples:
Purely sensory:
smell - I (olfactory)
vision - II (optic) hearing/balance - VIII (vestibulocochlear)
Purely motor:
eye movements - III, IV, & VI
, neck muscles - XI (spinal accessory)
tongue - XII (hypoglossal)
Mixed:
facial sensation and chewing - V (trigeminal)
facial muscles and taste - VII (facial)
throat sensation and motor - IX (glossopharyngeal)
Internal organs -
sensory and motor - X (vagus)
Afferents for touch & proprioception (somatosensation) from the body travel via spinal
nerves through dorsal roots to enter the spinal cord (the "13th cranial nerve").
Cranial nerves help with info coming in and out of the brain
Vagus = wander, provides signals for stomach, intestines, ouptut for the autonomic
nervous system
Spinal nerves ✅Spinal nerves - Spinal nerves (31 pairs) are named for the segment of
spinal cord they are connected to. Each is the fusion of dorsal/back (sensory) and
ventral/front (motor) roots.
Cervical (neck) - 8
Thoracic (trunk) - 12
Lumbar (lower back) - 5
Sacral (pelvic) - 5
Coccygeal (bottom) - 1
DO NOT MEMORIZE
Spinal cord has grey matter on the inside and white matter on the outside, cortex is the
opposite
Dorsal roots come out the back
Ventral roots come out in the front
Input to the spinal cord ✅Sensory signals from touch receptors (a.k.a., dorsal root
ganglion cells) enter via dorsal roots to synapse with cells in the dorsal horn (BACK) of
the spinal cord. The cells supply reflexes, more complicated local processing in the
spinal cord, and ascending pathways to the cerebellum and cerebral cortex.
Muscle stretch receptors, Golgi tendon organs, and joint receptors are also dorsal root
ganglion cells and provide their input via dorsal roots.
Sensory info comes in through the spinal cord (first synapse) then to motor neurons ->
kick out leg
Inhibit bottom muscle
Spinal cord knows how to walk using local calculations
Grab things
Motor cortex tells you to go do it
Local and ascending pathways to cerebellum and cerebral cortex
