Neuro : psychatric diseases midterm

What is neuroscience

multidisciplinary science that studies the nervous system (brain and spinal cord) and how it functions

* different themes

What is mental illness

* Reduces ability to function for prolonged periods
* significant levels of distress
* changes in mood, behaviour, thinking
* feelings of sadness and loneliness
* feeling disconnected

What are the causes of psychiatric disease

Genetics, early life experience (trauma, abuse) stressful life event (death, loss of job), epigenetics (role of environment), environmental influences on fetus (drug or alcohol abuse)

What is the biopsychosocial model

Model that attributes mental illness to multiple factors

* biological
* psychological
* social factors

Medical model of psychiatric disease

mental illness comes from various underlyine factors (physiological, biological or genetic)

* psychological issues are classified under biological disease or abnormalities in brain function

Etiology

What causes it?

Prognosis

What is it?

What are the short/long term consequences?

Epidemiology/Prevalence

How common is it?

What does RDoC stand for?

Research Domain Criteria Initiative

Dorsal

Directional term for the to of the brain (surface)

Ventral

bottom of the brain

anterior

front of the brain

posterior

back of the brain

medial

middle of the brain

lateral

sides of the brain

coronal section

view from dorsal to ventral

Horizontal section

lateral to lateral

Saggital section

anterior to posterior view

Cerebrum

Major component. Made up of both hemispheres.

Cerebral cortex

Outermost layer of gray matter

Cerebellum

Motor coordination. (w/ balance and fine motor control) and mental processes

Brain stem

connects brain to spinal cord.

Responsible for basic instinctual functions

Spinal cord

carries nerve signals throughout your body

Gyrus

bumps and ridges on your brain

Sulcus

grooves that complement the gyrus

Efferent nerves

Exit.

Connect CNS to skeletal muscles and motor nerves

Afferent Nerves

arrive.

Carries info into the CNS

Parasympathetic syst.

rest and digest

sympathetic syst.

fight or flight.

right hemisphere

controls emotion, creativity, spatial ability, artistic and musical skills

left hemisphere

speech and language control center. Arithmetic and writing.

cerebral hemisphere

groove in the middle of both hemispheres that connects the two.

frontal lobe

reasoning and decision making. Motor and executive function (planning, organization, initiation in order to achieve a goal.)

Central sulcus

separates the lobes

Parietal lobe

tactile functions, sense of self in space, somatic sensory

Occipital lobe

visual processing (real and hallucinatory)

Temporal lobe

visual, auditory and gustotory functions

corpus callosum

White matter made up of axons that connects and communicates between the two hemispheres.

Components of the brain stem

Diencephalon

Midbrain

Hindbrain

Components of the diencephalon

Thalamus and hypothalamus

Thalamus

integrate sensory info in and then divide out the info to different parts to process

hypothalamus

main region involved in homeostasis

midbrain

key cells involved in the reward circuit.

Secretes dopamine

Hindbrain

Pons : connects cerebellum to brain stem. involved in sleep

Medulla: controls breathing and HR. connects brain and spinal cord

ventricular syst.

cerebral spinal fluid circulates in the ventricles in order to cushion the brain.

ventricles

four interconnected hollow spaces in the brain that circulates cerebral spinal fluid (CSF)

cerebral spinal fluid

fills ventricles, similar density to brain.

Meningeal layers + functions

dura mater: thickest

arachnoid: looks like spiderwebs in which CSF circulates

pia mater: delicate inner layer.

blood brain barrier

tighter endothelial junctions

endothelial cells line the inside of the blood vessels. Very small gaps to protect brain from toxins.

ex. area postrema that activates the vomit reflex

neuron

basic information processing units that communicate between each other

glial cells

support and regulate neural activities.

form = function

form myelin sheaths that insulate axons and allow for faster communications

Anatomy of the neuron

Dendrites - cell body - axon hillock - axon - terminal button

(very organized, oriented and layered)

Dendrites

gathers info. collects and integrates into the cell body

cell body of neuron

contains nucleus and DNA

axon hillock

where action potential begins.

Axon

passes down the depolarization to terminal buttons

terminal buttons

conveys info to other neurons through their dendrites.

myelination of axons

myelin = fatty white substance produced by glial cells

oligodendrocyte = (CNS) myelinates multiple axons

schwann cells = (PNS) myelinates one axon

grey matter

cell bodies and blood vessels

white matter

rich in myelinated axons. highways of the brain

Tracts

bundles of axons in CNS

connect nuclei to each other

mostly white myelinated matter

nerves

bundles of axons in PNS

nuclei

clusters of cell bodies that form a functional group w/ specific function.

clusters working together = circuit

Action potential

message travelling from axon hillock to axon terminals

• flows in orthodromic direction

• short term change in membrane polarity that transmits electrical signal

Takes place in ion channels in the neuron membrane. starts at -70mV

• sodium channels open at -50mV. sodium rushes in and depolarizes.

• followed by hyperpolarization to not trigger another action potential right away.

• positive feedback loop that moves it down the axon.

synapse

point of connection between two neurons. site of inter-neuron info transfer

components of synapse

presynaptic neuron - synaptic cleft - post synaptic neuron

(vesicles that each contain a quanta of neurotransmitters)

steps of synaptic transfer

1. Neurotransmitters are synthesized and transported down to terminal buttons where they’re stores in vesicles.

2. action potential changes charge, calcium flows in that releases NT

3. NT bind to respecctive receptors in the post-synaptic membrane

4. Receptors are coupled to ion channels that opens when boound. influx of ions. causes post-synaptic potential (PSP)

Excitatoy PSP

depolarizing event. positively charged cations flows in. Increases likelihood of another action potential.

Inhibitory PSP

Hyperpolarizing event. Anions flow in. decreases likelihood of another action potential.

Temporal summation

Multiple impulses received together will trigger an action potential when alone they wouldn’t have been able too.

Major classes of neurotransmitters

Amino acids

Monoamines

Peptides

Other

Ligands

molecules that bind to and activate receptors.

NT and hormones are ligands to their respective receptor.

Ligand that binds + opens = agonist

Ligand that binds + prevents from opening = antagonist

Deactivation of neurotransmitters

Diffusion

Degradation (via enzyme)

Reuptake proteins (reabsorbs into the cell that just released it)

Glial cells

Hormones

Specific chemicals released by one cell group in an endocrine gland that travel through the blood stream in order to act on targets in the body

HPA axis

 hypothalamic - pituitary- adrenal axis

Hypothalamus releases CRH (corticotropin-releasing hormone). Acts on anterior pituitary

Pituitary releases ACTH (adrenocorticotropic releasing hormone) acts on the adrenal gland

Adrenal: releases glucocorticoids (cortisol)

stress

effect of the stressor.

Stressor

Perceived threat to the body /body’s homeostasis that provokes a response

Either psychological or physical

Stress response

body’s response to stressor.

physiological and/or behavioral changes to cope with/escape stressor

General adaptation syndrome

Alarm: initial fight/flight

Resistance: physiological adaptation to cope with the stressor.

Exhaustion: Physiological resources depleted. Unable to cope. Disease.

SAM axis

Sympatho-adrenomedullary axis

• fast pathway.

Hypothalamus projects to spinal cord to synapse with SNS neurons. Project to adrenal medulla which releases catecholamines

Catecholamines

Epinephrine and norepinephrine which bind to adregenic receptors throught the body

Cortisol

Steroid hormone. Glucocorticoid.

Ligand for:

• Mineralocorticoid receptors (MR)

• Glucocorticoid receptors (GR)

  • Activated by elevated cortisol levels.

Transcription factor type receptors

• goes into DNA and changes how genes are expressed.

Effects of cortisol

Inhibits immune syst.

Metabolic effects

• ↓ bone and connective tissue formation

• ↑ breakdown of lean body mass

• ↑ blood sugar levels

• Altered sensitivity of tissue to other hormones.

Impact of stress on cognition

impairs higher level reasoning, flexible thinking and memory

Prefrontal cortex (main planning, decision maker)

• recent brain structure that inhibits lower brains structures (less adapted to today’s world). Stress inhibits the PFC and the lower structures are dominant (basal ganglia and amygdala)

How to shut down stress response

Negative feedback loop

• GR receptors trigger it. When bound send message to hippocampus to stop CRH

• Hippocampus +hypothalamus reduce CRH

• Anterior pituitary makes less ACTH

• Overall less cortisol produced ending stress response

Chronic stress and brain cells

Extreme chronic stress kills GR receptors in brain. Impairs ability to control cortisol production.

Eustress

positive stress. beneficial

psychological resilience

ability to cope with stressful events

Yerkes-Dodson law

balance between good and bad amount of stress.

optimal level = best performance

stress is good motivator

What is sickness behavior

behavioral and cognitive changes that accompany physical illness.

psychoneuroimmunology

interaction between mind, brain and immune syst.

bidirectional communication. two way street

Immune syst.

Protect body from microbial overgrowth.

Relies on chemical communication via cytokines

Two division w/ coordinated response.

• innate immune sust.

• adaptive immune syst.

cytokines

chemical messengers used like hormones for immune signaling

effects

• inflammatory response

• attract more innate immune cells

• activate adaptive immune syst.

innate immune syst.

“general purposes” born with. sensitive to bacteria. When activated releases cytokines into syst.

ex: macrophages bind to pathogens and trigger phagocytosis

adaptive immune syst.

activated by cytokines. involves two systems of leukocytes

• cell mediated immunity

• anti-body mediated immunity

leukocytes

white blood cells

cell mediated immunity

involves T-cells

• activated by cytokines. attack infected body cells and destroy them

Anti-body mediated immunity

B-cells

produce antibodies that bind to antigens on pathogens to kill or deactivate them

Cytokines and how they get to the brain

Vagus nerve

• bidirectional communication receptors all over the body send the messages up to the brain

Binding and signaling via glial cells

active transport through the blood brain barrier

cytokines and depressive behaviour

cytokine treatment causes depressive sympt.

dep. more common in those w/ anti-inflammatory diseases

anti-depressants improve comp. of sickness behaviour