Chapter 3: Biology & Neuroscience

Nervous system: intro

Nervous system: intro

• has neurons and glial cells

• we communicate/ comprehend world via movement and sound

• people from diff cultures have diff variations of this; ie. using more hands etc.

Neuron

• basic building block of NS

• communicate with brain to form thoughts and actions

• code info as electrical signals and send chemical messages to organs

Neuron parts: Dendrite

• extensions of cell body membrane, branch out to communicate to other neurons

• have neurotransmitters and receptor proteins

• more branches = more comms

Neuron parts: Neurotransmitter

• chemicals released from axon terminals

• act as messages to other neurons/body parts

• often bind to receptors

Neuron parts: Receptors

proteins built to receive chemical messages from neurotransmitters

Receptor + neurotrans ->

release chemicals to cells -> fire/reduce fire rate depending on message

As we learn and grow, dendrites...

form connection with more neurons, becomes complex fast

Neuron parts: Soma (star with nucleus)

cell body of neuron, control metabolism of cell; dendrites = extension of soma

Neuron parts: Axon hillock

intersection b/w soma and axon

Neuron parts: Axon (wire)

part of cell mem. delivers messages to other neurons and body parts

Neuron parts: Axon terminal/presynaptic neuron

releases neurotransmitter once the action potential gets to the axon terminal

Neuron parts: Terminal buttons

very edge of the axon terminal where the neurotransmitter exits; has vesicles

Neuron parts: Vesicles

lil bubbles store neurotransmitters

Neuron parts: Synaptic cleft

space b/w the end of neuron that releases a neurotransmitter (AT) and end of the receiving neuron (dendrite)

Neuron parts: Synapse

small fluid filled gap b/w neurons where neurotransmitters are released

Neuron parts: pre and post synaptic neuron

1. release neurotrans in synapse

2. receptor containing neuron ready to bind with neurotrans from pre

Neuron parts: Myelin

protein/fatty substance that wraps around axon to protect and increase speed of electrical impulses; maintain resting potential

Neuron parts: Nodes of Ranvier

gaps in the myelin that allow ions to enter into the axon and change the charge inside

Electrical activity flowchart

soma -> axon -> terminal buttons -> form synapse with other cells

Polarized vs depolarized cells

1. • charge, at rest, do not release neurotrans

2. • charge, likely to send neurotrans

Voltage graph analysis

depolarization -> action potential -> polarization -> refractory period -> rest

Propagation

process by which electrical impulses get sent to the end of a neuron

Na and K pump analysis

• Resting poten: indo pumps closed, transporter pump on (Na exit, K enter)

• Depolar: some Na pumps open and Na+ enter cell, more depolar more open

• Hyperpolar: peak action poten, Na close/K open, membrane is depolar

Excitatory vs inhibitory neurotrans

1. increase the probability of electrically active neuron

2. decrease the probability that the neuron is activated

GABA neurotrans example

inhibitory neurotrans -> binds to receptor -> opens Cl channel -> negative cell

Acetylcholine neurotrans example

excitatory neurotrans -> binds to receptor -> opens Na channel -> positive cell

Triggering action potential steps

• receive neurotrans signal

• Na channel opens, influx of cations lead to depolarization

• K channel opens, repolarization occurs

Drug influence

• agonist mimic endogenous neurotrans (artificial mimics natural)

• passive-aggressive chemicals compete for neurotrans binding site

Types of neurotrans: Glutamate

• excitatory

• learning and movement

• EX: PCP (hallucinations), Ketamine (anesthetic)

Types of neurotrans: GABA

• inhibitory

• learning, anxiety inhibition

• EX: Valium (anxiety), Flumazenil (reverse anesthesia)

Types of neurotrans: Acetylcholine

• excitatory

• learning muscle action

• EX: botox

Types of neurotrans: Dopamine

• E/I

• learning, reward/pleasure

• EX: Cocaine (euphoria inducing)

Types of neurotrans: Serotonin

• E/I

• mood regulation

• EX: Prozac (depression meds)

Types of neurotrans: Norepinephrine

• E/I

• mood regulation

• EX: Doxepin (anxiety/ depression meds)

Types of neurotrans: Enkaphalin/endorphine

• E/I

• pain regulation

• EX: Opiates, Morphine, heroin <3

Glial cells: Oligodendocytes

wrap myelin insulation around axons in central NS

Glial cells: Schwann cells

wrap myelin insulation around axons in peripheral NS

Glial cells: Astrocytes

help with neuron nutrition and maintain ions around membrane

Glial cells: Microglia

clean debris and get rid of germs

Neural network

• complex connections of dendrites and axons

• around 80-90 billion in brain

• axons (the nerve) extend from CNS (brain + spinal cord)

Efferent vs afferent

• Eff: carrying electrical impulses away from CNS trigger neurotrans/hormone release in organ or muscle

• Aff: carrying impulses back to the CNS from the organs and muscles

Neuroplasticity

babies have more neurons, lose inefficient ones overtime, grow new branches (learn new things =_=)

Neocortex vs Medulla

1. outer part of brain, does high-level processing

2. close to spinal cord, regulates breathing, HR, reflexes

Central Nervous System

cells and supporting structures inside the skull and vertebral column; brain and spinal cord

Peripheral Nervous System

nerves outside CNS, specialized sensory endings (retinal cells, touch receptors, hair cells)

PNS: Somatic vs autonomic

1. voluntary movement

2. automatic movement: parasym and symp

Autonomic PNS: Parasympathetic

lower brain region; help with rest, digestion and repair

Autonomic PNS: Sympathetic

responsible for things that require excitement

Brain: Frontal lobe

• decision making (front) and movement (back)

• prefrontal cortex receives info from cerebral cortex to make decisions

Brain: Parietal lobe

• integrates sensory information from across brain

• primary sensory info for touch

• visual info from visual cortex

• damage leads to spatial challenges

Brain: Occipital lobe (striped cortex)

primary sensory processing for visual info

Brain: Temporal lobe

• memory and sound

• has auditory cortex

Brain: Precentral vs Postcentral gyrus (parietal lobe)

1. posterior, motor cortex, voluntary movement neurons

2. anterior, somatosensory cortex, touch

Brain: Pons

• send info from medulla to central cortex for high processing

• send brain info to spinal cord, control facial/eye movements

Brain: Cerebellum (smol brain)

• coordinate movement (rhythm and timing) and problem solving

• spinocerebellar (fine tunes motor patterns)

• vestibulocerebellar (adjusts posture and balance)

• cerebrocerebellar (adjusts timing and planning of movements)

Fetus brain

form neural tube and it grows into various structures

• prosencephalon (forebrain)

• prosencephalon (forebrain)

• rhombencephalon (hindbrain)

Reticular activating system (RAS)

network of cells in medulla and pons that regulate alertness (arousal and focus)

Coordination of brain parts (neurons + glial)

nuclei/ganglia in limbic sys, basal ganglia and cerebellum sort out action/thoughts (help out prefrontal cortex)

Limbic system

• circuits in the cortex (telencephalon) and the midbrain (mesencephalon)

• prefrontal cortex

• olfactory (smell) cortex

• amygdala

• hippocampus

• cingulate gyrus

• hypothalamus

LS: Amygdala

increases electrical activity in its neurons when we are under threat, regulates fight/flight response

LS: Hippocampus

gateway for memory formation

LS: Cingulate gyrus

becomes actives when we experience unpleasant things

LS: Hypothalamus

• control several functions in autonomic and endocrine sys

• responsible for regulating hunger response, sexual behaviour, temp, and aggression

BG: Dorsal Striatum

caudate and putamen; play a role in coordinating movement, near neocortex

BG: Ventral Striatum

globus pallidus, substantia nigra (Parkinson's), subthalamic nucleus; play a role in coordinating movement, near neocortex

Thalamus: Right and left

coordinate all info, except olfaction, to respective parts of brain

Neocortex: Makeup

has gyri (ridges), sulci (valleys) and fissures (spaces between lobes)

Frontal Lobe Regions

• prefrontal cortex (bheaviour and memory)

• premotor/supp motor cortex (movement)

• primary motor cortex

• Broca's Area

• Frontal eye fields

• corticoculbar tract (facial movements)

Parietal Lobe Regions

• receive info from contralateral sides of body

• dorsal column system

• Spinothalamic tract

• process spatial and # info

Temporal Lobe Regions

• forming memories and processing sound

• lesions: dead cells cannot perform function

• auditory cortex/association area

• olfactory cortex

• Wernicke's area: process speech

Occipital Lobe Regions

• light stimuli

• lens -> retina -> optical nerve -> optic chiasma -> LGN -> visual cortex

Corpus Callosum

connect hemispheres and allow them to share info

HPA axis

hypothalamus, pituitary, adrenal

Brain Imaging: CT Scan

• Xrays

• fast, cheap, noninvasive

• radiation exposure

• detect changes to structure due to disease

Brain Imaging: MRI

• H+ magnetic field imaging

• no radiation, precise, noninvasive

• expensive, can't have device in patients tf

• detect changes to structure due to disease

Brain Imaging: fMRI

• H+ magnetic field imaging

• no radiation, noninvasive, no injections/ingestion

• CVD deters measurements, unreliable

• measure activation during or after stimuli

Brain Imaging: DTI

• track water movement along neural pathways, measure its density

• no radiation, noninvasive, no injections/ingestion

• difficult to navigate tracts and pathways

• white matter degeneration in disease

Brain Imaging: PET/SPECT

• track molecular changes via ingested radioactive compound

• see molecular changes irt

• radiation expo

• see activity of neurotransmitters