PSYC 280 - EXAM 1 (CHP 1-3)

Define 1) Neuroscience and 2) Behavioural neuroscience

1) scientific study of NS

2) relates behaviour to bodily processes

Ancient Egypt perspective on brain

heart most important so they preserved it and tossed second-hand organs like the brain

Ancient Greece - Aristotle perspective on brain

mentalism: mental capacities to be properties of the heart (from terms like fainthearted, openhearted, etc.)

• brain is secondary organ to cool the hot blood from the heart

Ancient Rome: Galen perspective on brain

animal spirits: spirits in the body that passes along nerves; “vital spirit” flowed within heart, and “natural spirits” located in the liver

• limited understanding since dissection was illegal

1650’s Rene Descartes perspective on brain

dualism: mind (soul) and body are separate but brain and NS involved in bodily functions and movements

brain as a machine: fluid forced out of brain by ventricles, filled with cerebral spinal fluid (CSF) that flushes out the brain, and allows muscles to move

• reflexes: when hurt, feeling moves to the brain and “reflects” back down to move body (protection guide)

• proposed that animals are immature compared to humans due to lack of intelligence

17th and 18th century perspective on brain

NS dissected and white and grey matter identified

Luigi Galavani perspective on brain

electrical stimulation: muscles move by electrical signals and found that fluid to brain is not needed to pump muscles (dead frog experiment)

Bell and Magendie perspective on brain

reflex arc in spinal cord: nerves are wires connecting electrical signals

• circuit = stimulation → skin → afferent nerve (sensory) → spinal cord → efferent nerve (motor) → muscle

• dorsal and ventral roots in spinal cord carry sensory info

Franz Joseph Gall perspective on brain

localization of function & phrenology: shape of skull determines personality traits and characteristics

• brain map; foundation for localization function (areas of the brain influences functions), situations that question this…

  • Phineas Gage; metal rod through skull/brain which changed his personality but maintained ability to walk, talk, etc.

  • Broca’s area; patient tan only could speak “tan” but acted like he understood everything that was going on (damage to language production)

  • Wernicke’s area; patient form sentences but made no sense (damage to language comprehension)

End of 19th century perspective on brain

determined that brain was source of behaviour change, but functions unknown…

• histology; study of microscopic tissues that reveals cellular features

• Roman y Cajal — examined microscopic images and sketched every detail

  • Golgi → nerve net = interconnected network fused of nerve fibres

  VS

  • Cajal → neuron hypothesis = brain has individual cells called neurons that do not touch

Hodgkin & Huxley perspective on brain

electrical signals generated by neurons down axon: more understanding of how nerves work

Ottow Loewi perspective on brain

vagus nerve: electrical stimulation of this nerve further understands how nerves communicate

• 2 frog hearts in 2 beakers: chemical transition → stimulation → heart 1 in fluid → heart 2 in fluid receives info

Donald O. Hebb perspective on brain

how circuits strengthen their connections as consequence of experiences led to → Hebbian synapse (type of plastic connection between neurons)

• showed that cognitive processing = networks of active neurons (molded by repeated activation patterns into functional circuits)

Nowadays perspective on brain

• neuroplasticity: to mold of form, yet to be discovered further

• neuroeconomics: aims to identify brain regions that are active when decisions are being made (ex. playing games)

• epigenetics: focuses on lasting effect patterns of gene expression (turning on or off of genes) without changing the structure of genes

Nervous system is made up of what? Describe what it does.

Neurons: arranged into circuits that make up the NS’s two-way communication system — creates simple to complex motor reflexes

What do neurons contain? describe what they all do.

• axons; carries electrical signal away from cell body

  • collateral; multiple branches that split from axon

  • terminal; ends of axon with lots of mitochondria

  • hillock; decision point if a signal is strong enough to send AP

• dendrites; receives info from other neurons

• dendritic spines; bumps on dendrites that contract and retract

• cell body (soma); contains organelles that support cell viability

neuron to neuron AP transmission: define the 4 process functional zones in

1. input zone: dendrites receiving info from other neurons

2. integration zone: soma combines received info to determine sending signal, or not, of its own

3. conduction zone: single extension of axon, carries neuron’s electrical signals away from soma to axon collaterals — aided by myelin sheath to speed up signal and protects it

4. output zone: axon terminals transmit signal across synapses to other neurons

How are neurons classified? describe these categories.

kinds of neurons…

• motor; large axons to trigger muscular contractions and movements

• sensory; various shapes/sizes (usually short) depending on what info (light, sound, or touch) is being transmitted from sense organs to brain

• interneurons; receives info from other neurons and makes up networks/circuits that perform complex functions of the brain

shapes of neurons…

• multipolar; many dendrites and single axon

• bipolar; single dendrite at one end and single axon on other (sensory)

• unipolar; single extension and axon for its entire length, one end branching dendrites and cell body branches off partway along axon (touch/pain from body to spinal cord)

what does synapses do in signal transmission? What are the 3 divisions?

location where information is transmitted from one neuron to another — axon terminal of presynaptic cell to dendrites on postsynaptic cell

• 3 divisons → presynaptic membrane, synaptic cleft, postsynaptic membrane

what are synaptic vesicles and what do they help with?

tiny hollow spheres in presynaptic axon terminal that contains molecules of NT — communicator between presynaptic neurons and postsynaptic cells

• response to electrical activity in axon → synaptic vesicles fuse to post. membrane to rupture and release NT into synaptic cleft → NT interact with matching NT receptors on post. membrane → receptors attach and react to send signal to next neuron → NT detach and diffuse away

how does the axon integrate and transmits information

axon hillock: cone-shaped enlargement on soma that gathers and integrates info from synapses

• innervate; result of integration process determines when neuron produces signals of its own — electrical impulses race down axon towards target

axon transport: axon’s hollow tube contains enzymes and proteins that convey from soma to axon terminals — work in BOTH directions…

1. anterograde transport = moves materials towards axon terminals

2. retrograde transport = moves used materials back to soma for recycling

how do glial cells assist neurons?

affects neuronal processes by providing neurons with support and protection

• 4 types…

  • oligodendrocytes (CNS) and Schwann cells (PNS): wraps around segments of axons to protect them by producing myelin from glial cells — between segments is Node of Ranvier

• astrocytes: weaves around and between neurons with tentacle-like extension to help with structural support, enhance brain activity, and secretes chemical signals

  • form Blood Brain Barrier by weaving through blood vessels

• microglial cells: tiny and mobile that act as health monitor and scavengers by maintaining sites of injury by cleaning up debris

astro and micro can worsen problems like edema which can follow to brain injury and degenerative processes like Alzheimer’s and Parkinson’s disease

what nerves does the somatic nervous system consist of?

• cranial nerves — head, neck, and organ directly from brain)

• spinal nerves — connected segments of spinal cord and each nerve is made up of motor and sensory axons

what are the cranial nerves? (motor, sensory, and both)

sensory:

• olfactory — smell

• optic — visual

• vestibulocochlear — hearing and balance

motor:

• oculomotor, trochlear, and abducens — signals muscle to move eyes

• spinal accessory — controls neck muscles

• hypoglossal —controls tongue

both:

• trigeminal — facial sensation and chewing

• facial — facial muscles and taste

• gloggopharyngeal — taste and throat sensations and throat muscles

• vagus — route for brain to control and receive info from visceral organs (sweating, digestion, and HR)

what are the spinal nerves?

connected segments of spinal cord and each nerve is made up of motor and sensory axons

• cervical — neck

• thoracic — torso

• lumbar — lower back

• sacral — pelvic

• coccygeal — bottom

  • name of nerve = which segment its connected to (ex. nerve connected to 12th thoracic segment, T12)

what is an injury that associates with the spinal nerves?

parapalesia: damage to lower spinal cord can result in losing function in lower limbs

• severity depends whether its partial or complete

what is the autonomic nervous system and what does it consist of?

main system for controlling the body’s organs involuntary, and consists of…

• sympathetic NS; fight or flight — prepares body for immediate action (BP and HR increases, and pupils dilate)

• parasympathetic NS; rest and digest — helps body relax and prepare for future action (regulates SNS)

  • triggers opposite effects of each other (SNS = norepinephrine; PSNS = acetylcholine)

what are the planes and directional terms of the brain?

planes:

• horizontal = flat middle slice around the brain

• sagittal = lateral slice from front to back of brain

• coronal = lateral slice from left to right side of brain

directional:

• medial = middle of brain; lateral = outside of the brain (ears)

• ipsilateral = same side; contralateral = opposite side

• superior = above; inferior = below

• anterior/rostral = front; posterior/caudal = behind

• proximal = close; distal = farther

• dorsal = back of organ; ventral = front of organ

what are the the 2 cerebral hemispheres of the outer surface of the brain?

cerebral cortex: complex cognitive and sensory info

• thick tissue of brain…

  • gray matter — darker area that receives and processes info

  • white matter — lighter area (from myelin) under grey that transmits info

gyri: ridges of tissue created by foldings of the cortex, and are separated by crevices called sulci

• Gyri and sulk get grouped together and turn into lobes…

  • frontal; motor control, abstract thinking, planning, memory, and judgement (teens immature due to this being underdeveloped)

  • parietal; processes sensory info from body for spatial cognition, and sense of touch

  • temporal; auditory processing, language comprehension

  • occipital; vision processing

what are the 2 boundaries between the brain lobes?

1. sylvian fissure: divides temporal from frontal and parietal

2. central sulcus: divides frontal and parietal lobes, and has 2 parts…

• precentral gyrus — motor cortex (frontal lobe)

• postcentral gyrus — sensory cortex (parietal lobe)

describe the development of a fetal brain and their subdivisions

• neural tube made up of cell and filled with fluid, then shows 3 swellings at head end…

  • forebrain: develops into cerebrum, hypothalamus and thalamus

  • midbrain: develops into midbrain

  • hindbrain: develops into pons, cerebellum, and medulla

• remainder of tube forms into spinal cord

• at 50 days frontal divides into 2 regions…

  • telencephalon; forms cerebral hemispheres

  • diencephalon: becomes hypothalamus and thalamus

how does the control in the left and right sides of the brain work?

each side of the brain controls the contralateral side of the body

what does the 6 layers of the brain contain? (include the 2 nerves mentioned)

number of cell bodies and neurons increase as you make your way closer to the core of the brain

• pyramidal cell: most important neuron, in layer 3 or 4

• cortical columns: organization of cerebral cortex from white matter to surface

what are 9 structure in the cerebral cortex?

• basal ganglia: control of movement, contains caudate nucleus, putamen, globus pallidus

• limbic system: emotion, learning and memory, contains amygdala, hippocampus, and singulate gyrus

• amygdala: limbic structure involved in emotional regulation, door perception, and memory

• hippocampus and fornix: learning and memory

• cingulate gyrus: cognitive functions (directing attention)

• olfactory bulb: sense of smell

• thalamus (relay station): directs incoming sensory info to appropriate regions of cortex for processing, and receives instructions back about sensory info

• hypothalamus: regulates biological needs (hunger, temperature, sex, and aggression) — control pituitary gland

• corpus callosum: connects right and left hemispheres by axons and allows brain to act as a single unit

what are the 2 structures in midbrain?

• tectum (roof): sensory processing and has one bump in each hemisphere…

  • superior colliculi → visual

  • inferior colliculi → sound

• tegmentum (covering): main body, contains…

  • substantia nigra → part of basal ganglia (loss of neuron can cause Parkinson’s)

  • periaqueductal → perception of pain

  • reticular formation →reflects sleep and arousal

what are the 4 structures of the brainstem?

• cerebrum: motor,, coordination, movements, balance, posture, and learning (sensitive to alcohol)

• pons: coordination and communication centre connecting midbrain → medulla

• medulla: conveys motor and sensory fibers to and from body, respiration and HR

  • damage = locked-in-syndrome

• reticular formation: regions of brainstem extending from medulla through thalamus, sleep and arousal

what are 2 main structures that protects the brain?

• bone; skull

• meninges; keeps foreign substances out of brain, has 3 layers..

  • dura mater — thick outer layer

  • arachnoid layer — creates subarachnoid space that puts brain in CSF and contains blood vessels to make up its vascularity

  • pia mater — thin inner layer

what is meningitis?

meninges infected by viruses or bacteria that causes inflammation where pressure is on brain

• leads to delirium, drowsiness, stupor, and coma

what is meningioma?

tumours that can slowly grow, with no symptoms or cause, from meninges and presses on brain as it grows

describe the cerebral spinal fluid (CSF)

produced by choroid plexus (lines lateral ventricle) and circulates in and around CNS and is continuously made and drained by the body — function is to cushion the skull

• has 2 systems…

1. ventricular: series of chambers called cerebral ventricles that are filled by CSF

2. glymphatic: drains waste in CSF fluids during sleep, as well as distribution of nutrients, immune system, and signalling substances

describe the CSF flow

lateral ventricle → third ventricle → fourth ventricle → CSF exits from ventricular system through small openings → circulates over outer surface of brain and spinal cord

what is hydrocephalus?

outflow in channels connecting ventricles in blocked, and can cause severe intellectual impairments and even death from built up pressure (enlarged head)

what is chiari malformation?

base of skull is misshapen or too small, the cerebellum gets pushed into lower skull and inhibits flow of CSF

what is the blood brain barrier?

made up of astrocytes and ensures toxic chemicals in blood cannot get to brain

describe what neural signals have

membrane potential: based on electrical potential and contains ions that can either be negatively charged (anions) or positively charged (cations), also has large proteins anions that cannot exit cell

• inside of cell = negative (K+)

• outside of cell = positive (Na+ and Cl-)

what are the 3 layers to maintain resting membrane potential (RMP)?

1. extracellular and intracellular fluid: water and ions

• inside of cell is neg. due to large anion proteins which attracts K+ to come inside then back out to balance the charges

2. phospholipid membrane: hydrophilic heads and hydrophobic tails

• acts as a barrier between extra and intra-cellular space

• selective permeability — only allows selected ions to pass freely through membrane (K+ freely but not Na+)

3. membrane proteins:

• channels — ions cross membrane through appropriate shaped channels

• gates — shaped to allow passage of substances when gates are open (occurs due to a certain voltage), then closes to block

• pumps — changes shape to carry substances across cell membrane

  • sodium-potassium; pumps 3 Na+ out for 2 K+ inside — permeable membrane allows K+ to leave so build up of neg. ions causes electrostatic pressure to pull K+ back until equilibrium potential (balances concentration gradient to resting potential)

what are the 4 movements of ions?

1. randomly and independently

2. random motion, ions diffuse down their gradient

3. charged ions are attracted by opposite charge and repelled by same charge

4. charges can interact across a physical layer

what are the 2 forces that drive ion movement?

1. diffusion: arises from distribution of molecules from high to low concentration gradient

• selectively permeable membrane will allow ions like K+ to move and diffuse equally, while other remain on one side concentrated

2. electrostatic pressure: arises from distribution of electrical charges where charged particles exert electrical forces on one another

• opposite charges attract, same charges repel

• semi-permeable membrane can cause unequal distribution of electrical charge

what are the 2 concepts of how AP are triggered?

1. hyperpolarization: increases membrane potential by making it more neg. than resting

2. depolarization: decreases membrane potential by making it less neg. to resting

• small fluctuations….

  • local potentials — signal does not spread, but diminishes over time

  • graded potentials — variable amplitude depending on stim strength

what is an action potential?

quick switch between negatively charged to positively charged

• flows down axon and always looks the same

• timing of AP may be wave-like from other AP needing time to reset for re-trigger

describe the AP process

1. depolarization: increase flow of Na+ = increase resting voltage (-50mV)

2. repolarization: K+ rushes out to regulate voltage in which voltage settles attempts to settle back to normal (Na+ voltage gated channel is inactive)

3. hyperpolarization: voltage is more neg. than resting

• considered relative refractory — able to trigger another AP its stimulus is strong enough to regulate back to -50mV

4. refractory period: cannot start another AP without voltage resetting to -50mV

• 2 phases…

  • absolute refactory period — immediately follows after production of AP, no stimulation can trigger another AP (Na+ channels inactive)

  • relative refractory period — only strong stimulus can depolarize axon to threshold to produce another AP (determines neuron’s maximal rate of firing)

what does propagation in AP mean?

process in which AP is regenerated in regions of axon where electrical signal travels from one segment to another without losing strength

what is saltatory conduction?

AP jumps from one node of Ranvier to another with the help of myelin insulation resisting flow of ions across membrane — timing of signals are rapid

• if un-myelinated then electrical signal has that wave-like motion — timing is off but signals are the same

describe the postsynaptic potential and its 2 types

brief changes in membrane potential of postsynaptic cell in response to NT

• excitatory postsynaptic potential (EPSP) — opening of Na+ channels (spike of AP triggers another AP due to voltage being above -50mV)

• inhibitory postsynaptic potential (IPSP) — opening of Cl- channels (dip of AP is unlikely to trigger another AP due to voltage being under -50mV)

what does spatial and temporal summation mean?

spatial: multiple AP signals from synapses are more spread apart from different locations and are being added together

temporal: AP signal from synapse coming more quickly and frequent from one location

what are the 7 steps in chemical synaptic neurotransmission?

1. AP arrives at presynaptic terminal

2. voltage-gated Ca2+ channels in membrane of axon terminal open (depolarization)

3. Ca2+ causes synaptic vesicles filled with NT to fuse with presynaptic membrane and rupture (exocytosis), releasing transmitter into cleft

4. transmitter bind to special receptors in postsynaptic membrane, leading to opening of ion channels (results either EPSP or IPSP)

5. IPSPs and EPSPs spread towards axon hillock — if all EPSPs and IPSPs depolarize axon hillock to reach threshold = AP rises

6. synaptic transmission rapidly stops so message is brief and accurately reflects the activity of presynaptic cell

7. synaptic transmitter activates presynaptic receptors as a way of monitoring the extent of presynaptic cell

what is synaptic delay?

time needed for Ca2+ to enter terminal for vesicles to fuse to membrane for transmitter to diffuse across synaptic cleft and transmitter to interact with their receptors before postsynaptic cell responds

how do transmitters bind to receptors?

key in lock concept — ligand; right shape fits into receptor protein and activate it or block it

• agonist: mimics actions of transmitter

• antagonist: blocks actions of transmitter

Ex. acetylcholine (ACh) can act as: excitatory (agonist) — opening Na+ and K+, OR inhibitory (antagonist) — opening Cl-

what are the 2 processes that occur when ACh is released into synaptic cleft

degradation: ACh breakdown and inactivate by acetylcholinesterase (AChE) — AChE makes more ACh

reuptake: transmitters like norepinephrine, dopamine, and serotonin are absorbed back into axon terminal and cleared from synaptic cleft by transporters — repackaged into new synaptic vesicles to await re-release

• depression can cause malfunction of reuptake mechanisms

what are the 5 criteria of neurotransmitters?

1. synthesized in presynaptic neurons and stored in axon terminals

2. released when AP reach axon terminals

3. recognized by receptors on postsynaptic membrane

4. causes changes in postsynaptic cell

5. blocking release interferes with cell’s ability to affect postsynaptic cell

NT CLASSES: amino acid NT

has one effect, prepackaged for action, and needs both transmitters in order for balance

• glutamate: excitatory, metabotropic = slower via second messenger

  • AMPA, NMDA, kainate

• GABA: inhibitory, has 3 types…

  • GABAa; allows Cl- into post which causes rapid hyperpolarization inhibits cell’s activity (ionotrophic = faster)

  • benzodiazepines: Xanax and Ativan activate GABAa receptors to decrease excitability of neurons and acting to reduce anxiety and panic attacks, etc.

  • GABAb: metabotropic, these drugs may help treat diverse chronic problems like pain and mood disorders

NT CLASSES: acetylcholine (ACh) — Aminę

pathways: basal forebrain → cortex → amygdala → hippocampus (cholinergic)

• 2 receptor subtypes…

  • nicotinic receptors: muscle contraction, excitatory, ionotropic

  • muscluarinic receptors: parasympathetic function, inhibitory or excitatory, metabotropic

• loss of neurons = Alzheimer’s (forebrain reveals differently)

NT CLASSES: dopamine (DA) — Amine

motor control, learning and positive reinforcement

• 2 dopaminergic pathways…

  • mesolimbocortical → ventral tegmental area (VTA) → nucleus accumbens → cortex

  • mesostriatal → substantia nigra → basal ganglia

• reward learning: dopamine spikes when predicting a reward and when given a unpredicted reward — dopamine dips/neutral when not given reward

• “frozen addicts”: MPTP metabolized to MPP+ which is toxic to DA neurons in substantia nigra

NT CLASSES: norepinephrine — Amine

controls alertness, mood, sexual behaviours, etc.

• pathways: locus coeruleus → forebrain → lateral tegmental area → brainstem and spinal cord (noradrenergic)

• metabotropic

NT CLASSES: serotonin (5-HT) — Amine

mood, vision, anxiety, sexual, sleep, etc.

• pathways: midbrain raphe nuclei → forebrain → brainstem raphe nuclei → spinal cord (serotonergic)

NT CLASSES: peptide NT

opioid peptides (endorphins) are mimicked by opiate drugs like…

• enkephalins: met-enkephalins, leu enkephalin

• endorphins: beta-endorphin

• dynorphins: dynophin A

  • ALL act as painkiller and has rewarding properties

• oxytocin and vasopressin — memory and social interactions and pair-bonding (peptide hormones)

NT CLASSES: gas NT

breaks all criteria…

• produced outside axon terminals, not held in vesicle and dissolves in cellular fluid and diffuses out of neuron

• no receptors involved; diffuses into target cell and activates second messengers

• retrograde transmitter