PSY 351 exam 1

Neurons/nerve cells

• specialized cells that receive inputs, integrate them and distribute info to other neurons

• 80-90 billion in brain

Glial cells

• same number of them as neurons

• provide various support functions

• directly participate in info processing

Synapses

tiny gaps between neurons where info is transmitted between them

Principal divisions of neuron

1. input zone

2. integration zone

3. conduction zone

4. output zone

Input zone

dendrites of neurons receive info via synapses from other neurons

Dendritic spines

small projections from surface of dendrite that add more space for synapses

Integration zone

cell body/soma of neuron integrates info received to determine whether to send signal

Conduction zone

axon/nerve fiber carries neuron’s own electrical signals away from cell body

• axon may split into multiple branches — axon collaterals

Output zone

axon terminals transmit neuron’s signals across synapses to other cells

Axon terminals

transmit the neuron’s signal across synapses to other cells

Motor neurons

trigger movements

• large with long axons reaching out to synapse on muscles, causing muscular contractions

Sensory neurons

convey info from sense organs to brain

• take on different shapes depending on which sense the neuron is signalling

• longer axon

Interneurons

• this is what most of the neurons in the brain are

• receive info from other neurons, process it & pass integrated info to other neurons

• make up hugely intricate networks & circuits that perform complex functions of brain

• shorter axons

Larger neurons

tends to

• have more compelx inputs & outputs

• cover greater distaces

• convey info more rapidly than smaller neurons

Classifying neurons by shape

1. multipolar neurons

2. bipolar neurons

3. unipolar neurons

Multipolar neurons

• many dendrites

• single axon

• most common type of neuron

Bipolar neurons

• single dendrite at one end of cell & single axon at other end

• especially common in sensory neurons e.g. vision

Unipolar/monopolar neurons

• single extension, typically identified as axon for its entire legnth

• branching dendrite-like input zone & integration zone from which axos rises directly

• leads away to distant output zone with its axon terminals

• cell body branches off axon partway along its length

• transmit touch & pain info from body into spinal cord

No. of dendrites & complexity of inputs received

• simple neurons have just a couple of short dendritic branches

• others have huge & complex dendritic trees/arbors receiving a ton of synaptic contacts from other neurons

Presynaptic neuron

info transmitted from this

Postsynaptic neuron

info transmitted to this

Synapse divided into compenents

1. presynaptic membrane of axon terminal of presynaptic/transmitting neuron

2. synaptic cleft that separates presynaptic & postsynaptic neurons

3. postsynaptic membrane on dendrite/cell body of postsynatpic/receiving neuron

Synaptic vesicles

• tiny hollow spheres in presynaptic axon terminals

• contain molecules of neurotransmitter

Neurotransmitter

special chemical with which presynaptic neuron communicates with postsynaptic cell

Info transmission through synapses

• in response to electical signal, synaptic vesicles fuse to presynaptic membrane

• rupture to release neurotransmitters into synaptic cleft

• after crossing cleft, the released neurotransmitters interact with matching neurotransmitter receptors that stud the postsynaptic membrane

• receptors capture and react to neurotransmitter, altering level of excitation of postsynaptic neuron

• affects likelihood that postsynaptic neuron will in turn release its own neurotransmitter from its axon terminals

Neuroplasticity

capacity of neurons to continually remodel their connections with other neurons

Functions of axons

• rapid transmission of electrical signals along outer membrane of axon

• slower transportation of substances within the axon, to & from axon terminals

Axonal transport

trransport of substances through interior of axon between cell body (where they are produced) and axon terminals (where they are used)

Anterograde transport

moves materials towards axon terminals

Retrograde transport

moves used materials back to cell body for recycling

Main types of glial cells

1. oligodendrocytes

2. Schwann cells

3. astrocytes

4. migroglial cells

Oligodendrocytes

supply myelination to neurons in brain & spinal cord

• each cell typically supplies myelin beads to several nearby axons

Schwann cells

provide myelination of neurons in other parts of body

• each cell wraps itself around a segment of one axon to provide a single bead of myelin

Myelination

myelin sheaths wrapping around axons of neurons

• large increase in speed in which electrical signal passes down axon

• jumping from one node of Ranvier to the next

Nodes of Ranvier

small, uninsulated patches of axonal membrane between adjacent beads of myelin

Astrocytes

• weave around & between neurons with tentacle-like extensions

• some astrocytes stretch between neurons & fine blood vessels, controlling local blood flow to increase amount of blood reaching more active brain regions

• help form tough outer membranes that swaddle the brain

• secrete chemical signals that affect synaptic transmission & synaptic formation

Microglial cells

• tiny & mobile

• primary job: contain & clean up sites of injury

Gross neuroanatomy

made up of tissues that are comprised of

• neuronal cell bodies

• dendrites

• axons

• glial cells

neural structures that are visible to naked eye

Peripheral nervous system

made up of nerves

• somatic nervous system

• autonomic nervous system

Somatic nervous system

consists of nerves that interconnect brain & major muscles & sensory systems of body

• main pathway through which brain controls movement & receives sensory info from body & sensory organs

• cranial nerves & spinal nerves

Autonomic nervous system

made up of nerves that connect primarily to viscera (internal organs)

• little conscious, voluntary control over its action

• brain’s main system for controlling the organs of body

• sympathetic & parasympathetic nervous systems

Functions of sympathetic nervous system

prepares body for immediate action

• fight-or-flight response

• release norepineprhine

Anatomy of sympathetic nervous system

• axons of SNS exit from middle parts of spinal cord, travel short distance then innervate sympathetic ganglia

• sympathetic ganglia run in 2 chains along each side of spinal column

• axons from sympathetic ganglia then spread throughout body, innervating all major organ systems

Function of parasympathetic nervous system

generally helps body relax, recuperate & prepare for future action

• rest-&-digest response

• release acetylcholine

Anatomy of parasympathetic nervous system

• nerves of PNS originate in brainstem (above sympathetic nerves) & in sacral spinal cord (below sympathetic nerves)

• travel longer distance before terminating in parasympathetic ganglia

• clusters of neurons that are usually located close to organs they serve

Central nervous system

consists of brain & spinal cord

Spinal cord

• funnels sensory info from body up to brain

• conveys brain’s motor commands out to body

• contains circuits that perform local processing & control simple units of behavior

Saggital plane

divides brain into left & right

Horizontal plane

divides brain into upper & lower parts

Coronal plane

divides between front and back

Gray matter

outer layers of cerebral cortex, inner layer of spinal cord

• contain a preponderance of neuronal cell bodies & dendrites

• mostly receives & processes info

White matter

inner layers of cerebral cortex, outer layer of spinal cord

• whitish fatty myelin that insulates many axons

• mostly transmits info

Gyri

ridges of tissue created by cortex folding

Sulci

crevices separating gyri

Ganglion

cluster of neurons outside of brain

Nucleus

cluster of neurons in brain

Superior

Inferior

Anterior

towards the front

Posterior

towards the back

Dorsal

the top of the neuraxis

Ventral

bottom of neuraxis

Rostral

Caudal

Neuraxis

Proximal

closer to target region

Distal

farther from target region

Lateral

towards the sides

Medial

towards the middle

Thalamus

receives sensory info & relays it to cortex (except olfaction)

Hypothalamus

hormones, motivated behavior

• sex

• aggression

• eating

Basal ganglia

form circuit critical for movement

Limbic ganglia

complex nuclei for emotions

Hippocampus

forming declarative memory/facts

• bilateral damage = no declarative memory

Brodmann’s map of the brain

mapped various parts of brain based on function rather than structure

Cerebral cortex

has 6 layers of cells, each layer is has

• band of similar neurons

• a distinctive pattern of dendrites/axons

Mesencephalon

midbrain

• substantia nigra

• ventral tegmental area (VTA)

• superior colliculus

• inferior colliculus

Superior & inferior colliculi

in non-humans, play a big role in vision (especially hunting)

Substantia nigra

uses dopamine for movement

Ventral tegmental area (VTA)

uses dopamine for reward circuit

Rhombencephalon

hindbrain

• metencephalon

• myencephalon

• spinal cord

Myencephalon

medulla oblangata

• life-sustaining functions e.g. breathing, heartrate

Metencephalon

• pons

• cerebellum → coordination

Reticullar formation

large network of neurons that go through hindbrain, midbrain & into forebrain

• norepinephrine as neurotransmitter

• important for vigillance & attention

Dura mater

outermost, tough layer surrounding brain

• visible to naked eye

Arachnoid membrane

• looks like spider web

• has blood vessels and CSF

• below it is subarachnoid space

Pia mater

• aka pial layers

• microscopic layer just before brain matter

Cerebral spina fluid (CSF)

• fills subarachnoid space

• keeps brain from collapsing on itself

Hematoma

internal bleeding

Subdural hematoma

internal bleeding in dura mater

• blood puts pressure on brain & causes brain damage

• may leak out through bottom which is important for life → could die

Carotid arteries

arteries that meet with vertebral artery to go up to brain

• found in sides of neck

• branch into anterior & middle cerebral arteries

Vertebral artery

artery that meets with carotid artery to go up to brain

• towards back of neck

3 main arteries of brain

1. anterior cerebral artery

2. middle cerebral artery

3. posterior cerebral artery

Blood brain barrier

• formed by tight junctions between endothelial cells in blood vessels

• oxygen, carbon dioxide, some fat-soluble molecules pass through freely

• some important substances (e.g. glucose) need active transport by transporter protein

• large and charged molecules can’t pass through

Meninges

3 protective layers surrounding brain

• dura mater

• arachnoid membrane

• pia mater

Stroke

clot/narrowing/rupture interrupts blood supply to brain region, causing it to stop functioning/die

Warning signs of stroke

1. sudden numbness/weakness

2. altered vision

3. dizziness

4. severe headache

5. confusion/difficulty

Gross dissection

yoink out brain to study with naked eye

• only shows structure not function

Studying brain structure

• individual neurons

• nuclei

• gray matter

Study connections between structures

• fiber tracts: bundles of axons

• white matter