Biological Bases of Behavior (Unit 4)

localization of brain function

rats with enriched environments have more complex neural connections

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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)

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

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

1) send

2) messages

they run through the entire body and communicate with each other

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

they do not grow back

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

• 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)

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 cell body that contains the nucleus

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

FIRE! React/respond:

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

DON’T FIRE! Don’t react/respond:

these types of signals prevent the neuron from firing

the action potential is conducted down the axon

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

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

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

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

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

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)

“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

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

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

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

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

at rest

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

the charge is -70 mv

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)

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

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

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

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)

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 it’s charge is less than -70mv

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

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

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

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

1) doesn’t fit

2) bind

• muscle function & motor movement

• learning & memory

• attention

• Alzheimer’s Disease (memory loss)

• problems swallowing

• problems with mobility/stability (falling)

• muscle spasms/twitches

excitatory

• mood & emotion

  • “feel good” and “reward”

• arousal

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

• Schizophrenia

• delusions

• drug addiction

both - depends on the situation

• mood regulation

• hunger

• sleep

• depression & mood disorders

• eating disorders

• OCD

• anxiety

• hallucinations

• seizures

• autism

inhibitory

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

• released during stressful situations

• mood elevation

• mental disorders (specifically depression)

• anxiety

excitatory

• brain’s main inhibitory NT

• regulates sleep-wake cycle

• “calming NT”

• anxiety

• epilepsy

• insomnia

• Huntington’s Disease

• sleep disorders

• eating disorders

brain’s MAIN inhibitory NT

• pain control

• stress reduction

• positive emotions

• eating behavior

• potential involvement in addiction

  • especially opiates

  • vulnerability to this

• 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)

inhibitory

• brain’s main excitatory NT

• basis of learning and long-term memory

overstimulation of the brain, which can cause migraines & seizures

brain’s MAIN excitatory NT

keeps us from feeling pain

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

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

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

1. Central Nervous System (CNS)

2. Peripheral Nervous System (PNS)

• brain (+brain stem)

• spinal cord

• connections between brain & spinal cord neurons to other 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!!!

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!!!

Sensory

Afferent

Motor

Efferent

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

1. autonomic (ANS) (sympathetic & parasympathetic)

2. somatic

controls glands & muscles of internal organs

ex. digestion, heartbeat

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

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

calms

undo what happened from sympathetic nervous system prior

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

enables voluntary control of muscles

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

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

both produce molecules that act on receptors everywhere

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

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

• secretes thyroxin

• regulates metabolism

• impacts sleep & concentration

• fatigue

• depression

• dryness

• sensitivity to cold

• joint or muscle pain

• regulate calcium levels / absorption

• bone metabolism (bone density)

• releases adrenaline which helps regulate arousal

• releases corticosteroids which impact long-term stress response

• digestion

• insulin production

• glucose levels in blood

• secretes androgen, estrogen, and progesterone

• regulates development sex characteristics and reproduction

• releases melatonin which helps regulate sleep and body rhythms

• signals the pituitary gland

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

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

removal of a part of the brain

ex. removing a brain tumor

• sophisticated 3D X-ray of the brain

• good for tumor locating or finding blood clots

• tells us nothing about function

• SHOWS STRUCTURE ONLY

• 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)

• 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

• no radioactive materials

• produces images at a higher resolution than PET

• measures blood flow as brain is active

• STUDIES FUNCTION & STRUCTURE