Biological Bases of Behavior (Unit 4)

Franz Gall determined in the 1800s that bumps matter, and his work contributed to the study of the brain because he was the first to study…

localization of brain function

what conclusions could be drawn after looking at rats in enriched versus deprived environments and how could it be applied to humans?

rats with enriched environments have more complex neural connections

_______________________________________

applied to humans…

neural complexity could be influenced by our environmental factors

ex. parents are told to read to their children… this in turn strengthens their neurons (nurture / environmental factors played a role)

what is a neuron?

a cell that conducts electrochemical signals (or action-potential)

neurons (nerve cells) are involved in…

thinking, dreaming, feeling, moving, remembering, and learning

neurons ___1___ and receive ___2___ that allow for thinking, moving, learning, etc.

1) send

2) messages

where are neurons located?

they run through the entire body and communicate with each other

what do neurons do?

they send & receive messages from other structures in the body, such as muscles and glands

what happens once a neuron dies (excluding new research)?

they do not grow back

ever heard the saying “he/she just lost some brain cells”?

what does your Nervous System control?

• your ability to see, hear, and smell

• your ability to recognize where you are and to remember if you’ve been there before

• your capacity to wonder

• your capacity to sense danger + the physical response you have to that danger (ex. pulling your hand away from a hot stovetop)

3 basic functions of a neuron:

1. receive signals (or information)

2. integrate signals (to determine whether or not the info should be passed along)

3. communicate signals to target cells (other neuron muscles or glands)

the soma is…

the cell body that contains the nucleus

dendrites are…

branch/tree-like structures that extend from the soma - involved with receiving and processing incoming signals (excitatory or inhibitory)

excitatory signals:

FIRE! React/respond:

these types of signals make the neuron fire (generate an impulse response, ex. pulling your hand away from a hot stovetop)

inhibitory signals:

DON’T FIRE! Don’t react/respond:

these types of signals prevent the neuron from firing

if the neuron receives an excitatory signal and does fire, then…

the action potential is conducted down the axon

the axon…

joins the cell body at the axon hillock and carries the signal to the axon terminals

explain myelin sheath

• protects/covers many axons - it acts as an insulating substance which helps convey the nerve impulse more rapidly

what happens if myelin is damaged?

multiple sclerosis, weakened muscles, fatigue: communication to the muscles slows and eventually, muscle control is lost

at the end of the axon are axon terminals (end with buttons) which…

make connections to target cells by sending the message to the synapse

synapses are…

neuron to neuron connections or the space between neurons:

this is where information travels from the presynaptic (first) neuron to the postsynaptic (second/target) neuron

neurotransmitters are…

the chemical messengers that transmit information by crossing the synapse and binding to membrane receptors on the postsynaptic cell (thus sending on the excitatory or inhibitory signal)

glia cells are…

“the support cells”- they attach to an strengthen neurons…

• Latin for “glue”

• produce myelin

• absorb dead neural cells

• can help axons regenerate

• more plentiful than neurons (10:1)

• research on glia is connected to Alzheimer’s & mood disorders

based on the idea that it’s an excitatory message, how would neural communication run its course? (think: PARTS of a neuron with this… not the whole process of action potential)

1. dendrites receive the message

2. message travels through the cell, down the axon, to the presynaptic terminal

3. the neurotransmitter (chemical message) is released from the presynaptic terminal of one neuron, crosses the synapse, and binds to the dendrites of the next neuron (post-synaptic neuron)

4. this process happens again and again until the message has been communicated to the proper part of the body or brain

if the original message is inhibitory, what happens during neural communication?

the neuron will be pulled further and further away from firing because it is not meant to fire

what is an action potential?

also known as a neural impulse, it is the electrical impulse that travels down the axon in order for it to communicate information

what generates an action potential?

the movement of positively charged sodium and potassium atoms in & out of channels in the axon’s membrane (membrane is semi-permeable)

**without an action potential, there is no neural communication

when not communicating a message, the neuron is…

at rest

when a neuron is at rest, what is it’s charge (specific number?), and what is this state called?

has a negative charge and the cell is polarized in this state

the charge is -70 mv

resting potential means that (and in what state is the axon membrane at this point?)…

the inside of the cell is negative relative to the outside - there are few K+ ions inside, but many Na+ outside

the membrane of the cell is semi-permeable (a flow that goes in and out)

explain how action potential occurs:

1. a neuron receives a signal from a sensory receptor or a chemical message

2. excitatory vs. inhibitory… if the signal is excitatory, the message will be sent, it it’s inhibitory, it will remain at rest

3. when the dendrites receive excitatory input, gates on the semi-permeable membrane open & close

4. sodium gates open and sodium rushes in

5. since Na+ is positive, the charge of the neuron will become less negative

6. if the charge of the neuron reaches the threshold (-55 mv), an action potential will occur

what is the threshold?

the charge needed for a neuron to fire: -55 mv

the all-or-none/nothing principle states:

if the threshold of -55mv is met, an action potential will fire - it either happens or it doesn’t happen… there is NO IN BETWEEN

following an action potential, since the cell would rather be at rest, what needs to happen, and how is it achieved?

it needs to reach -70mv again (become more negative again)

in order to do this, potassium channels open up and potassium rushes out of the neuron, hyperpolarizing it for a split second (causing the refractory period)

the refractory period is when…

for a second, the charge becomes more negative than -70mv (during this time another action potential CANNOT fire)

the neuron is recharging itself to get ready to send more messages

essentially, it’s a slight lag while the neuron tries to reset itself

when is a neuron is hyperpolarized?

when it’s charge is less than -70mv

→ once it’s -70 again, it’s ready to send more messages (fire again)

what does the sodium potassium pump do?

regulates the passage of ions across the cell membrane by pumping positively charged ions into the cell and then pumping them back out when the action potential is over (kind of like diffusion)

moves potassium ions into the cell and sodium ions out - maintains the imbalance of the ions that makes the whole process possible

When action potential reaches the presynaptic terminal of a neuron, it causes the terminal buttons to release neurotransmitters which flood into the synapse- what of 3 things can happen to the neurotransmitters within the synapse?

1. they can bind to receptor sites (carry on the message) on the postsynaptic membrane (dendrites)

2. they can remain in the synapse, where they are destroyed and washed away by other biological substances

3. they can be drawn back into the terminal buttons via a process called reuptake

explain what reuptake is:

it’s like recycling of the neurotransmitters: neurotransmitters released into the synapse go back to the terminal buttons from which they were sent to go again

you must have the right key to fit the receptor-site lock: if the neurotransmitter ___1___, it can’t ___2___ to the next neuron

1) doesn’t fit

2) bind

acetylcholine function:

• muscle function & motor movement

• learning & memory

• attention

what is a result of too little acetylcholine?

• Alzheimer’s Disease (memory loss)

• problems swallowing

• problems with mobility/stability (falling)

what is a result of too much acetylcholine?

• muscle spasms/twitches

is acetylcholine excitatory or inhibitory?

excitatory

dopamine function:

• mood & emotion

  • “feel good” and “reward”

• arousal

what is a result of too little dopamine?

Parkinson’s Disease (tremors, shakes, lack of balance)

what is a result of too much dopamine?

• Schizophrenia

• delusions

• drug addiction

is dopamine excitatory or inhibitory?

both - depends on the situation

serotonin function:

• mood regulation

• hunger

• sleep

what is a result of too little serotonin?

• depression & mood disorders

• eating disorders

• OCD

• anxiety

what is a result of too much serotonin?

• hallucinations

• seizures

• autism

is serotonin excitatory or inhibitory?

inhibitory

norepinephrine function:

• arousal & alertness (fight-or-flight response)

• released during stressful situations

• mood elevation

what is a result of too little norepinephrine?

• mental disorders (specifically depression)

what is a result of too much norepinephrine?

• anxiety

is norepinephrine excitatory or inhibitory?

excitatory

GABA function:

• brain’s main inhibitory NT

• regulates sleep-wake cycle

• “calming NT”

what is a result of too little GABA?

• anxiety

• epilepsy

• insomnia

• Huntington’s Disease

what is a result of too much GABA?

• sleep disorders

• eating disorders

is GABA excitatory or inhibitory?

brain’s MAIN inhibitory NT

endorphins function:

• pain control

• stress reduction

• positive emotions

• eating behavior

what is a result of too little endorphins?

• potential involvement in addiction

  • especially opiates

  • vulnerability to this

what is a result of too many endorphins?

• artificial highs / artificially elevated mood

• inadequate response to pain (can relieve pain but too much so, which can be dangerous because if you never feel pain you could hurt yourself without even knowing it)

are endorphins excitatory or inhibitory?

inhibitory

glutamate function:

• brain’s main excitatory NT

• basis of learning and long-term memory

what is a result of too much glutamate?

overstimulation of the brain, which can cause migraines & seizures

is glutamate excitatory or inhibitory?

brain’s MAIN excitatory NT

what does substance p do?

keeps us from feeling pain

functions as a neurotransmitter and plays a role in transmitting pain signals (coexists with the main excitatory neurotransmitter glutamate)

what do antagonist drugs do?

bind to receptor sites of dendrites and block it from firing, therefore decreasing the effect of the NT

→ antagonist: opposes/gets in the way of the release of that NT

ex. an antagonist drug for dopamine would block more dopamine from being produced, if there is a surplus

what do agonist drugs do?

drugs that mimic NTs to make the neuron fire, therefore increasing the effect of the NT

→ mimics the correct “key” to that receptor site

ex. an agonist drug for dopamine would mimic the dopamine NTs and thus bind to receptors and cause the neuron to fire as if it was real dopamine binding

what 2 nervous systems does the body’s electrochemical communications network include?

1. Central Nervous System (CNS)

2. Peripheral Nervous System (PNS)

the Central Nervous System includes…

• brain (+brain stem)

• spinal cord

the Peripheral Nervous System includes…

• connections between brain & spinal cord neurons to other neurons

afferent/sensory neurons…

get info from outside & inside the body and bring it to the CNS

→ accept input from sensory receptors and pass it onto the brain & spinal cord

ex. touch a hot stove, sensory neurons with endings in your fingertips tell your CNS THIS IS HOT!!!

efferent/motor neurons…

get info from other neurons and convey commands to muscles, organs, glands

→ send signals from the brain to our muscles

ex. touch a hot stove, motor neurons tell our hand to MOVE!!!

what is the mnemonic device to help remember sensory versus motor neurons (their other names)?

Sensory

Afferent

Motor

Efferent

interneurons…

connect one neuron to another

are only found in the CNS (brain and spinal cord)

ex. if you touch a hot stove, the sensory neurons signal would travel to interneurons in your spinal cord, and these interneurons would signal to the motor to MOVE your hand while others would transmit the signal up the spinal cord to neurons in the brain which register PAIN

what are the 2 major parts of the Peripheral Nervous System?

1. autonomic (ANS) (sympathetic & parasympathetic)

2. somatic

the Autonomic Nervous System in the PNS…

controls glands & muscles of internal organs

ex. digestion, heartbeat

2 functions: sympathetic (emergency responses) & parasympathetic (calms)

the Sympathetic Nervous System function of the ANS is…

the emergency response system: arouses and spends energy

when your body perceives a threat and you have some sort of reaction (fight or flight response)

ex. pupils may dilate, accelerated heartbeat, adrenaline/norepinephrine released

the Parasympathetic Nervous System function of the ANS…

calms

undo what happened from sympathetic nervous system prior

ex. heart rate down (undoing the accelerate heartbeat the sympathetic nervous system may have caused)

the Somatic Nervous System in the PNS…

enables voluntary control of muscles

ex. get up for a snack? the somatic nervous system is at work

the Endocrine System is…

a communication system including glands which secrete hormones (chemical messengers) which travel through the bloodstream and affect other tissues including the brain

→ influence our interest in sex, food, and aggression

**some hormones chemically identical to NTs

what is similar of the endocrine and nervous systems?

both produce molecules that act on receptors everywhere

what is different of the endocrine and nervous systems (and what is the result)?

nervous system messages travel very quickly through neurons (fraction of a second - email) while endocrine system messages travel slowly in blood (several seconds - snail mail)

because of this, endocrine messages tend to outlast neural messages

ex. period of fear: hypothalamus glands (endocrine) release epinephrine and body responds (nervous) with increased heart rate, feelings of excitement - fight or flight response triggered… however, excitement still lingers

what is the KEY endocrine gland (the master gland)?

the Pituitary Gland

describe the Pituitary Gland:

• located in brain and controlled by hypothalamus

• releases growth hormones

• stress, growth reproduction

• also releases oxytocin (enables contractions, orgasm, pair bonding, group cohesion, social trust)

• influences the release of other hormones by endocrine glands (hence the title “master gland”) - it signals everything else in the endocrine system

• feedback system → brain → pituitary → other glands → hormones → body & brain

the Thyroid Gland (endocrine)…

• secretes thyroxin

• regulates metabolism

• impacts sleep & concentration

• fatigue

• depression

• dryness

• sensitivity to cold

• joint or muscle pain

the Parathyroid Glands (endocrine)…

• regulate calcium levels / absorption

• bone metabolism (bone density)

the Adrenal Glands (endocrine)…

• releases adrenaline which helps regulate arousal

• releases corticosteroids which impact long-term stress response

the Pancreas (endocrine)…

• digestion

• insulin production

• glucose levels in blood

the ovaries / testes (endocrine)…

• secretes androgen, estrogen, and progesterone

• regulates development sex characteristics and reproduction

the Pineal Gland (endocrine)…

• releases melatonin which helps regulate sleep and body rhythms

the Hypothalamus (endocrine)…

• signals the pituitary gland

what did Phineas Gage’s story teach us?

that different parts of the brain control different aspects of who we are

what is a lesion?

tissue destruction - a brain lesion is experimentally caused destruction of brain tissues

what is ablation?

removal of a part of the brain

ex. removing a brain tumor

what is a CAT/CT scan?

• sophisticated 3D X-ray of the brain

• good for tumor locating or finding blood clots

• tells us nothing about function

• SHOWS STRUCTURE ONLY

what is an MRI?

• gives very detailed pictures using magnetic waves (no exposure to radiation)

• good for finding tumors in the brain,

• AND determining depth (how deep is the tumor? where else has it spread to?) - images can also be used to find out if a tumor has spread into nearby brain tissue

• can take pictures at almost any angle

• SHOWS STRUCTURE ONLY (but depth, unlike a CAT scan)

what is a PET scan?

• measures changes in blood flow associated with brain function

• radioactive glucose lets researchers see what areas of the brain are most active during certain tasks

  • ex. looking at a flower means more blood flows to the part of the brain that neurons are firing in, showing which brain part is associated with looking at things

• cancer metabolizes at different rates, so useful for tumor detection

• looks for METabolic activity

• provides a color-coded image of the body’s FUNCTION rather than its structure

what is an fMRI?

• no radioactive materials

• produces images at a higher resolution than PET

• measures blood flow as brain is active

• STUDIES FUNCTION & STRUCTURE