MCAT p/s 3 - Behaviour, Human Development, Behaviour and Genetics, Motivation and Attitudes

Central Nervous System

• Brain and spinal cord

Peripheral Nervous System

• Everything that’s not brain and spinal cord

• Cranial nerves (12 pairs) and spinal nerves (31 pairs)

• Nerves, ganglia, afferent nerves, efferent nerves

Afferent nerves

• Nerves that transmit sensory information from sensory receptors all over the body to the CNS

• Part of PNS

Efferent nerves

• Nerves that carry signals away from the CNS to effectors like muscles and glands causing a response

  • Control smooth muscle cells, cardiac muscle, gland cells

• Part of PNS

Basic functions

Type of functions of the Nervous System

• Motor (skeletal muscle) control

• Sensory

• Automatic (reflexes)

Higher functions

Type of functions of the Nervous System

• Cognition

• Emotions

• Consciousness

Lower motor neurons (LMN)

• Efferent neurons of the PNS synapse that control skeletal muscle

• The skeletal muscle cells they contract are at the other end of the motor unit

• Form a neuromuscular junction

• Abnormalities of the motor unit lead to weakness

• Abnormalities of ________ lead to ______ signs

  • Atrophy of skeletal muscle

  • Fasciculations (involuntary muscle twitches)

  • Hypotonia (decreased muscle tone)

  • Hyporeflexia (decreased muscle stretch reflex)

• Control muscles of limbs and trunk and if they pass through cranial nerves, head and neck

• Controlled by upper motor neurons

Mechanoreceptor

Type of Receptor

• Position, vibration, touch

  • Stimuli: Mechanical stress, pressure changes, sound waves, gravity

• Location: skin, blood vessels, ears

• Fast receptor - axons large in diameter, thick myelin sheath

Chemoreceptor

Type of Receptor

• Stimuli:

  • Specific chemicals

  • Total solute concentrations

  • Blood pH

  • CO2 levels

  • Prostaglandins (nocireceptors)

• Location:

  • Tongue

  • Blood

  • Nose

  • Tissue

• Slow receptor - small axons

Nocireceptor

• Specific type of chemoreceptor

• Responds to pain/prostaglandins

• Slow response - small axons

Thermoreceptor

Type of Receptor

• Stimuli: heat, cold, certain food chemicals

• Location: skin, hypothalamus

• Slow receptor - small axons

Photoreceptor

Type of Somatosensation Receptor

• Stimuli: light

• Location: eyes (rod and cone cells)

• Slow receptor - small axons

Meissner’s corpuscle

Type of Mechanoreceptor

• Location:

  • Papillary dermis

• Non-hairy skin

• Requirements to fire:

  • Constantly changing stimuli

• Sensation:

  • Light touch, flutter, light stretch, small receptive field, grip control

• Adaptation:

  • Velocity

Merkel’s discs

Type of Mechanoreceptor

• Location:

  • Papillary dermis

• Non-hairy skin

• Requirements to fire:

  • Sustained/constant stimuli

• Sensation:

  • Light touch, pressure, fine details, small receptive field

• Adaptation:

  • Velocity and displacement

Ruffini endings (ruffini corpuscle/cylinder)

Type of Mechanoreceptor

• Location:

  • Reticular dermis

• Non-hairy skin

• Requirements to fire:

  • Sustained/constant stimuli

• Sensation:

  • Deep stretch, large receptive field

• Adaptation:

  • Displacement

Pacinian corpuscle (lamellar corpuscle)

Type of Mechanoreceptor

• Location:

  • Hypodermis

• Non-hairy skin

• Requirements to fire:

  • Constantly changing stimuli

• Sensation:

  • Vibration - deep push/poke

• Adaptation:

  • Acceleration

Hair follicle receptor

Type of Mechanoreceptor

• Location:

  • Reticular dermis

• Hairy skin

  • Equivalent to Meissner’s corpuscle for hairy skin

• Requirements to fire:

  • Constantly changing stimuli

• Sensation:

  • Hair movement, light touch

• Adaptation:

  • Displacement

Muscle stretch reflex

• Causes muscle to contract after it is stretched as a protective response

• Ex. knee jerk response

• Muscles = muscle spindles

  • Requires somatosensory neurons and lower motor neurons

• Happens on same side (afferent/efferent)

Somatosensory neurons

• Type of afferent neurons important for muscle stretch reflex

• In muscle spindles

• Form excitatory synapse in spinal cord with another neuron in spinal cord, which sends axon out back of same muscle that was stretched and excites skeletal muscle cells to contract (lower motor neurons)

Afferent nervous system

• No conscious involvment

• Divided into sympathetic and parasympathetic nervous system

• Both have 2 chains or axons

  • SNS - short the long

  • PNS - long then short

• SNS - “Fight or Flight”–blood flow to intestine decreases → goes to skeletal muscle; HR increases; sweat glands activated

• PNS - Rest or Digest–blood flow to intestine increases; HR decreases; salivary glands activate

Gray matter

• Contains most of the neuron somas

• On inside or spinal cord

• On outside of brain

White matter

• Contains myelination axons

• On outside of spinal cord

• On inside of brain

Gray, white

Brain:

• Outside = _______ matter

• Inside = _______ matter

White, gray

Spinal cord:

• Outside = _______ matter

• Inside = _______ matter

Upper Motor Neurons (UMN)

• Type of efferent neuron of the CNS

• Control lower motor neurons

• Found in cerebral cortex and synapse on LMNs in brainstem and spinal cord

  • Divide them into tracts depending on if they go to brainstem (corticobulbar) or spinal cord (corticospinal)

• If damaged ____ signs occur:

  • Hyperreflexia - increased muscle stretch reflex

  • Clonus - rhythmic contractions of antagonist muscle

  • Hypertonia - increased skeletal muscle tone

  • Extensor plantar response - if you take a hard object and scrape along bottom of foot, normal response is flexor–toes will come down on the object. But with extensor, toes extend up

Corticobulbar tract

• Collection of axons of upper motor neurons heading to the brainstem

Corticospinal tract

• Collection of axons of upper motor neurons heading to the spinal cord

Frontal Lobe

Part of the Cerebral Cortex

• Motor cortex - body movements

• Prefrontal cortex - executive function, direct other parts

• Broca’s area - speech production

Parietal lobe

Part of the Cerebral Cortex

• Somatosensory cortex - touch/pain/pressure

• Spatial manipulation

Occipital lobe

Part of the Cerebral Cortex

• Vision

• Striate cortex - striated cells

Temporal lobe

Part of the Cerebral Cortex

• Sound

• Wernicke’s area

Contralateral control

• Let brain controls right side of body and right brain controls left side of body

• True for all senses accept smell (ipsilateral - same side)

Left

• _____ hemisphere us dominant for the vast majority of people

  • Math, language

Old brain

• Most simple structures, all near the bottom

• All occur outside our awareness, sleeping/breathing

  • Brainstem (medulla and pons) - HR/breathing, crossover point of nerves

  • Reticular formation - brainstem to other areas of brain, filters info and sends important info to thalamus, sleep/awake cycle, ability to be aware

  • Thalamus - relay station, where eye/ear info goes

  • Cerebellum - coordinates voluntary movement

Cerebellum

• Part of “old brain”

• Coordinates voluntary movement

  • Motor plan info

  • Position sense

  • Balance

• Middle of ______ helps coordinate middle body movement, walking, speech, eye movement

Brainstem

• Part of “old brain”

• Connects all parts of brain, incl cranial nerves

• Includes pons, medulla, reticular formation

  • Pavlov’s Really Frickin Mad

• Autonomic functions - respiration, digestion, lower/higher functions

  • HR/breathing, crossover point of nerves

• Where many cranial nerves attach

Reticular Formation

Part of the brainstem

• Neuron somas scattered throughout brainstem

• Motivation and alertness

  • tickle

Pons

Part of the brainstem

• Regulates waking and relaxing

Medulla

Part of the brainstem

• Regulates autonomic activity of heart and lungs

  • HR/breathing

Long tracts

• Collection of axons connecting cerebrum and brainstem

• 2 imp: motor (UMN) and somatosensory

Cranial nerves

• Most attached to brain stem

• Many functions

• 12 pairs

Subcortical cerebrum

• Refers to deep structures of cerebrum beneath cerebral cortex

  • Internal capsule

  • Corpus collosum

  • Basal ganglia

  • Thalamus

  • Hypothalamus

• Important for various functions: motor control, sensory processing, cognition, emotion, consciousness, etc.

Internal capsule

Part of Subcortical Cerebrum

• Contains important pathways, including corticospinal tract

Corpus collosum

Part of Subcortical Cerebrum

• Connects right and left hemispheres

Basal ganglia

Part of Subcortical Cerebrum

• Major role in motor functions

• Don’t have upper motor neurons, but help motor areas perform movements

• Cognition and emotion

Thalamus

Part of Subcortical Cerebrum

• Sensory functions

• All senses have pathways that travel here

• Higher functions of brain - cognition, emotion

Hypothalamus

Part of Subcortical Cerebrum

• Controls pituitary gland

  • Master gland that controls all other glands

• Regulates how much fluid in blood volume in any given time

Glutamate

Neurotransmitter

• Most common excitatory neurotransmitter

• Required for consciousness (midbrain structures)

• Reticular activating system has diffuse projection of ______ to cerebral cortex

• Associated with increased cortical arousal

• Amino acid neurotransmitter

GABA

Neurotransmitter

• One of the most common inhibitory NTs

• For brain

• Amino acid neurotransmitter

Glycine

Neurotransmitter

• One of the most common inhibitory NTs

• For spinal cord

• Amino acid neurotransmitter

Acetylcholine

Neurotransmitter

• Released by nuclei in frontal lobe (basilis and septal nuclei)

• Sent to cerebral cortex

• For lower motor neurons and autonomic nervous system

• Main neurotransmitter of the peripheral nervous system

• Involved in muscle contraction

Histamine

Neurotransmitter

• Released by hypothalamus

• Sent to cerebral cortex

• Monoamine neurotransmitter

Norepinephrine

Neurotransmitter

• Released by area in pons called locus coeruleus

• Sent to cerebral cortex

• Monoamine neurotransmitter

Serotonin

Neurotransmitter

• Released by raphe nuclei throughout the brainstem

• Sent to cerebral cortex and other parts of nervous system

• Monoamine neurotransmitter

• Low levels associated with depression

Dopamine

Neurotransmitter

• Monoamine neurotransmitter

• Low levels associated with Parkinson’s disease

• High levels associated with schizophrenia

• Produced by arcuate nucleus:

  • Sent to hypothalamus then pituitary gland

  • To control release of hormones (prolactin)

• Produced by substantia nigra:

  • To pathway associated with motor planning

  • Including basal ganglia - including striatum - if fails to be sent - Parkinson’s

• Produced by ventral tegmental area (VTA):

  • Sent to pre-frontal cortex via mesocortical pathway

    • Associated with reward, motivation, and negative symptoms of schizophrenia

  • Sent to nucleus accumbens, amygdala, and hippocampus - mesolimbic pathway

    • Reward, motivation, positive symptoms of schizophrenia

Endorphins (opioids)

Neurotransmitter

• Peptide neurotransmitter

• Involved in blocking pain sensations

• Produces “runner’s high”

Arcuate nucleus

Production site of Dopamine

• Sent to hypothalamus then pituitary gland

• To control release of hormones (prolactin)

Substantia nigra

Production site of Dopamine

• To pathway associated with motor planning

• Including basal ganglia - including striatum - if fails to be sent - Parkinson’s

Ventral Tegmental Area (VTA)

Production site of Dopamine

• Sent to pre-frontal cortex via mesocortical pathway

  • Associated with reward, motivation, and negative symptoms of schizophrenia

• Sent to nucleus accumbens, amygdala, and hippocampus - mesolimbic pathway

  • Reward, motivation, positive symptoms of schizophrenia

mesocortical pathway

• VTA sends dopamine to pre-frontal cortex via ___________ ________

  • Associated with reward, motivation, and negative symptoms of schizophrenia

mesolimbic pathway

• VTA sends dopamine to nucleus accumbens, amygdala, and hippocampus - _____________ ______

  • Reward, motivation, positive symptoms of schizophrenia

Amino acid neurotransmitters

Type of neurotransmitter

• Includes Glutamate, GABA, and Glycine

• Most functions

Peptide neurotransmitters

Type of neurotransmitter

• Includes opioids (endorphins)

• Perception of pain

Monoamine neurotransmitters

Type of neurotransmitter

• Amino group and aromatic group connected by 2-carbon chains

• Cognition, thinking, emotion, attention

• Includes serotonin, histamine, dopamine, epinephrine, norepinephrine

• Subgroup: catecholamines (benzene w/ 2 hydroxyl groups)

Phrenologists

• Scientists that believed each brain area is devoted to a certain personality characteristic, thought, emotion

• As areas of the brain developed–they would grow and create bumps on the skull which could then be used to study the individual

• Often study brain through observing what happens when injuries/brain damage occur

Cerebral localization

Specific parts of the brain can control specific aspects ofbehavior and emotion, thought, personality

Tissue Removal

Method of Lesion Studies

• surgical removal, surgical aspiration (sucking out brain tissue), orsevering the nerve with a scalpel (this allows for a destroying of the brain tissuein place...less invasive)

Radiofrequency regions

Method of Lesion Studies

• Used to destroy tissue on surface of brain and deep inside brain

• Wire is inserted into brain to determine the area

• Then pass high frequency current which heats up and destroys tissue

• Can vary current intensity/duration to change size, but destroys everything in the area (cell bodies and axons)

• You can’t tell if this area was responsible for the behavior that is not responding, or just has an axon passing through

Neurochemical lesions

Method of Lesion Studies

• MUCH MORE PRECISE METHOD

• Excitotoxic lesions (excitotoxins are chemicals that bind to glutamate receptors and cause influx of calcium that causes so much excitement that kills the neuron/ excites it to death

• Examples:

  • Kainic acid

    • Destroys cell bodies but doesn’t influence axons passing by

    • Don’t sever connections like in knifecuts/ radio frequency lesions

  • Oxidopamine

    • Selectively destroys dopamine and NE neurons. Can model Parkinson’s Disease

    • ery similar to dopamine. In reuptake, thepresynaptic cell takes the oxiopamine back for recycling (normalmechanism) but then this neuron is destroyed. It destroyssubstantia niagra neurons completely.

Cortical cooling (Cryogenic blockade)

Method of Lesion Studies

• Involves cooling down neurons until they stop firing

• Cryoloop–surgically implanted between skull and brain. Most important part is it’s temporary/reversible, unlike other techniques. K/O nerves–see effect, and then bring the animal back to normal functioning

CAT Scan (Computerized Axial Tomography)

Brain Machines

• X-rays to create image of brain

• Can’t tell what areas of brain are active at a given time

• Slightly lower resolution and not as good for soft tissue than MRI, but faster

• Sometimes combined with radioactive dye

MRI (magnetic resonance imagig)

Brain Machines

• Radiowaves added to magnetic field to disrupt orientation of atoms

• As atoms move back to alignment with magnetic field they release signals and those are used to create image

• This also doesn’t tell us anything about brain function either

• Provides high resolution images of soft tissue, but slow

EEG (electroencephalogram)

Brain Machines

• Tells you something about brain function

  • Can’t tell about activity of individual/groups of neurons, but tells you sum of total

  • Tells us about seizures, sleep, cognitive tasks

  • External/non-invasive

  • Don’t get picture of brain

  • Easier than MEG

MEG (Megnetoencephalogram) (aka SQUIDS-Superconducting quantum interference device)

Brain Machines

• Better resolution than EEG, but rarer because requires a large machine and special room to shield it

• Records the magnetic fields produced by electric currents in the brain

fMRI (functional Magnetic Resonance Imaging)

Brain Machines

• Same image from MRI but can look at which structures are active

• Neurons that are active require oxygen

  • Measuring relative amounts of oxygenated vs deoxygenated blood in the brain

  • can figure out what brain areas are being used for a certain task

• a calculated composite of several MRI images registering the changes (shows activity as colored areas over MRI)

PET scan (Positron Emission Tomography)

Brain Machines

• can’t give us detail of structure,but can combine them with CAT scans and MRIs

• Inject glucose into cells and see what areas of brain are more active at given point in time. (Active cells = use most glucose)

• More invasive

• Three-dimensional images of tracer concentration within the body are then constructed by computer analysis

• Require swallowing a radioactive tracer and shows activity, with low resolution

Hormones

• Produced by endocrine system

• Slow, but long-lasting effect (opp of nervous sys)

• Can be:

  • Proteins

  • Steroids (cholesterol)

  • Tyrosine derivates

• 3 types of effects:

  • Autocrine–effects the cell that makes it

  • Paracrine–regional effect

  • Endocrine signals–response that is far away

• Go everywhere, but only picked up by cells w/ receptors

• Secretion controlled by negative feedback loops

Autocrine

Type of hormone effect

• Effects the cell than makes it

Paracrine

Type of hormone effect

• Regional effect

Endocrine

Type of hormone effect

• Response that is far away

Hypothalamus

Part of the Endocrine System

• Connection between nervous and endocrine system

• Regulates how much fluid in blood volume in any given time

Pituitary

Part of the Endocrine System

• Master gland

• Anterior (FLAT-PEG): FH, LH, ACTH, TSH, Prolactin, endorphins, GH

• Posterior: ADH, oxytocin

• Pars Intermedia–MSH (Melanocyte stimulatinghormone)

FH, LH, ACTH, TSH, Prolactin, endorphins, GH

Hormones released by anterior pituitary gland

ADH, oxytocin

Hormones released by posterior pituitary gland

Thyroid

Part of the Endocrine System

• Regulates body metabolism

• T3/T4

• Affects growth and development of the brain, and regulates growth rates

Parathyroid

Part of the Endocrine System

• 4 spots on back of thyroid

• Regulates calcium levels

Adrenal glands

Part of the Endocrine System

• On top of kidneys

• ACTH acts on the gland

• Includes:

  • Adrenal cortex (outer)

    • Fluid volume, stress response

    • Glucocorticosteroids (cortisol)

  • Medulla (inner)

    • Catecholamine’s hormones (epinephrine, norepinephrine)

• Plays a supportive role in muscle and bone development

Gonads

Part of the Endocrine System

• Male = testes, female = ovaries

• FSH/LH stimulation releases sex hormones

  • Progesterone/estrogen

  • Testosterone

• Involved in sexual development during adolescence

Pancreas

Part of the Endocrine System

• Regulates blood sugar

• Not tied to pituitary gland

Sperm

• Male sex cell

• Transfers male genetic material to egg

• Has head (DNA) and tail (flagella) and middle section w/ mitochondria (E)

Egg

• Female sex cell

• Really big and immobile

• Contains genetic material and thick outer coating (zona pellucida)

• Fertilized once sperm penetrates plasma membrane

• Contains lots of mitochondria and other organelles

Fertilization

• When sperm and egg meet

• Steps:

  1. Sperm binding

  2. Acrosome reaction

  3. Cortical reaction

  4. Genetic transfer

Sperm binding

Step 1 of Fertilization

• When sperm comes into contact with zona pellucida

Acrosome reaction

Step 2 of Fertilization

• Enzymes leak into zona pellucida and digest it

• Sperm gets closer to plasma membrane of egg

Cortical reaction

Step 3 of Fertilization

• Enzymes on cortical granules of egg are ejected to zona pellucida and digest it

• Prevents other sperm from binding (blocks polyspermy)

  • If doesn’t happen, zygote fails

Genetic transfer

Step 4 of Fertilization

• Occurs at 2 weeks

• When sperm binds to plasma membrane and acrosome is gone, cortical granules are released, the plasma membranes fuse and all the genetic material gets released into egg

• Fusion of genetic material is fertilization

• Nuclear DNA comes in but also mitochondrial DNA (but the egg has WAYY more mitochondrial DNA that the sperm cell doesn’t have much effect

Embrogenesis

1. Fertilization

2. Cleavage

   • Splitting of zygote w/o growth

   • 1 cell → 2 cell → 4 cell → 8 cell → 16 cells → 32 cell (morula)

   • Morula begins to differentiate

3. Blastulation

   • Two layers develop:

     • Outer shell - trophoblast

     • Inner collection of cells - inner cell mass

       • Eventually differentiates into a two layered bilaminar plate

         • Epiblast

         • Hypoblast

     • Fluid filled cavity - blastocoel

4. Gastrulation

   • Germ layers form

     • Ectoderm, mesoderm, endoderm

5. Neurulation:

   • Core in mesoderm differentiayes into notochord

   • Notochord induces changes in above cells in ectoderm called neural plate

   • Neural plate begins to divide into mesoderm and forms neural tube

Cleavage

Step of Embryogenesis

• Splitting of zygote w/o growth

• 1 cell → 2 cell → 4 cell → 8 cell → 16 cells → 32 cell (morula)

• Morula begins to differentiate

Blastulation

Step of Embryogenesis

• Two layers develop:

  • Outer shell - trophoblast

  • Inner collection of cells - inner cell mass

    • Eventually differentiates into a two layered bilaminar plate

      • Epiblast

      • Hypoblast

  • Fluid filled cavity - blastocoel

Gastrulation

Step of Embryogenesis

• Germ layers form

  • Ectoderm, mesoderm, endoderm