Chapter 2

The Biological Perspective

The Nervous System - An extensive network of specialized cells thatcarries information to and from all parts of the body.

Neurons & Nerves: Building the Network

• Neuron – basic unit (cell) of nervous system and receives and sends

messages within that system

microscopic; 100 billion; 200 types (size / shape)

3 Structures of the Neuron1. Dendrite – branches that receive information from other neurons & transmits

information toward the cell body (tree like)2. Soma – Cell body that keeps neuron alive; determines if it will “fire” (transmit info) 3. Axon – extending fiber that conducts impulses away from cell body & transmits

them to other neurons or neural cells

• Glial Cells – grey fatty cells that provide support for the neurons to grow on & around, deliver nutrients, produce myelin, clean up waste & dead neurons

• Myelin sheath – fatty substance that coats axon to insulate, protect & speed up impulse

• Nerve – bundles of axon coated in myelin that travel together through the body

Message W/in the Neuron: The Neural Impulse

• Resting potential – when neuron is not firing (- charge inside + outside)

• Action Potential – release of the neural impulse consisting of thereversal of the electrical charge within the axon(+ sodium (Na) enters the cell)

• All or nothing – a neuron either fires completely or does not fire at all

Sending the Message to Other Cells: SynapseSynapse – site of transmission of nerve impulses from one nerve cell to another

– Axon terminal – branches at the end of axon– Synaptic bulb (knob) – rounded area on the end of the axon terminal– Synaptic cleft (gap)– space between bulb of one cell and the dendrite of another– Receptor sites- holes is surface of dendrite; shaped to receive certain neurotransmitters– Neurotransmitters – chemicals in the synaptic vesicles; when released effect the next

cell

Neurotransmission / Synapse1- Neuron at rest (- inside + outside)

2 - Neural impulses move down axon; gate opens; +Na enters cell voltage changes from (-) to (+)

3- When impulse reach button tip;must get across synaptic cleft (gap);synaptic vesicle release neurotransmitter

4- When reaches the other side;briefly bond w/ receptor sites(lock & key)

5- Receiving membrane will change;excite – increase firing (+ voltage)inhibit –decrease firing (- voltage)

6- Neuron returns to resting state (- voltage)

Action potential - a sequence of gates opening down the length of the cell (as 2nd gate opens 1st closes)

-multiple +/- messages sent; take average

Synapse• Excitatory Synapses – synapse at which a neurotransmitter causes the

receiving cell to fire.• Inhibitory Synapses – synapse at which neurotransmitter causes the

receiving cell to stop firing.

Agonists – chemical substances that mimic or enhance the effects of aneurotransmitter on the receptor sites of the next cell, increasein or decreasing the activity of that cell

Antagonists – chemical substances that block or reduce a cells response to the action of other chemicals or neurotransmitters.

Neurotransmitters (NT)

• Serotonin – Excitatory or inhibitory; involved in mood, sleep and appetite

• Dopamine – Excitatory or inhibitory; control of movement and pleasure

• Acetylcholine – Excitatory or inhibitory; muscle contraction, memory

• Norepinephrine – Mainly excitatory; involved in arousal and mood

• GABA - (gamma-aminobutyric acid) major inhibitory NT; sleep & inhibits movement

• Glutamate – major excitatory NT memory formation, nervous system development

• Endorphins – inhibitory neural regulators; involved in pain relief “ natures opiate”

endorphin rush: “falling in love” / battle field

Cleaning up the Synapse

1) Reuptake - neurotransmitters are take back into the synaptic vesicles– Cleans up the synapse

– Some drugs inhibit the reuptake like cocaine

– Depression if small amounts of serotonin released• Medications SSRIs (selective serotonin reuptake inhibitors)

• Leaves more serotonin in synapse to elevate mood

2) Enzymes – breakdown neurotransmitters not taken back into vessels– Acetylcholine – muscle activity can’t wait for reuptake; enzyme breaks it down

Quiz1) Which part of the neuron receives messages from other cells?

a) Axon c) Somab) Dendrite d) Myelin

2) Which one of the following is NOT a function of the myelin?

a) Insulates the axonb) Speeds up the neural messagec) Protects the nerve fiber from damaged) Aids in reuptake

3) When the neuron’s action potential is released, _______ ions are rushing into the axon through openings on the membrane.

a) Sodium c) Chlorideb) Potassium d) Oxygen

Quiz

4) When the action potential reaches the end of the axon terminals, it causes the release of

a) An electrical spark that sets of the next neuronb) Positively charged ions that excite the next cellc) Negatively charged ions that inhibit the next celld) Neurotransmitters that excite or inhibit the next cell

5) Receiving neurons have special __________ that fit the shape of certain molecules.

a) Synaptic vesicles c) Receptor sites

b) Gaps d) Branches

6) Which of the following is associated with sleep, mood and appetite?a) Acetylcholine c) Serotonin

b) GABA d) Endorphin

Quick Quiza) Which word in ( ) better fits each of the following definitions?

1. Basic building blocks f the nervous system (nerves, neurons)

2. Site of communication between neurons (synapse, myelin sheath)

3. Opiate-like substance in the brain (dopamine, endorphin)

4. Chemicals that make it possible for neurons to communicate (neurotransmitters, hormones)

The Nervous System

1) Central Nervous System (CNS)

2) Peripheral Nervous System (PNS)

The Nervous System

1. Central Nervous System (CNS)

1. Brain – Interprets & stores information & sends orders to muscles glands, & organs

1. Spinal Cord –long bundle of neurons that carry messages between the body & brain responsible for fast, life saving reflexes

The Nervous System2) Peripheral Nervous System (PNS)

Transmits information to and from the central nervous system

All nerves and neurons that are not contained in the brain and spinal cord but that run through the body itself

1. Somatic nervous system - carries sensory info from the senses to CNS &from the CNS to the voluntary muscles.

a) Sensory pathways – (Afferent) nerves from sensory organs to CNS

b) Motor pathways – (Efferent) nerves from CNS to the voluntary muscles

2. Autonomic nervous system- controls involuntary muscles, organs & glands

1) Sympathetic nervous system – prepares body to react and expend energy in time of stress (fight or flight)

2) Parasympathetic nervous system – maintain body functions in relaxed state; conserves energy; restore tonormal functioning after arousal

The Peripheral Nervous System

Parasympathetic & Sympathetic

Stem cell research: Pro or Con• Neurogenesis – production of new neurons from immature stem

cells

• Stem Cells – immature cells that renew themselves; grow into any cell

– Need cells a few days old

• Abortion clinics

• Excess from fertility clinics

The Endocrine Glands

Endocrine Glands – organs produce hormones & release into blood stream

Hormones – produced by endocrine glands; effects functioning of other organs

The Endocrine Glandsa) Pituitary Gland – growth hormones & affects all other glands (Master Gland)

– Oxytocin –enhances uterine contractions during birth; ejection of milk /nursing

b) Pineal Gland –– Melatonin – regulate daily biorhythms; promotes sleep

c) Thyroid Gland – regulates metabolism

d) Pancreas - controls levels of sugar in the blood

e) Gonads - Sex glands – development & maintenance of reproductive organs- Ovaries and testes

androgen – testosterone – male characteristics at pubertyestrogen – female characteristics at pubertyprogesterone – lining of uterus in prep for fertilized egg

f) Adrenal Glands – Adrenal hormones - produced by adrenal glands; emotion and stress

respond to heat; cold; pain; exercise; caffeine; nicotine

Cortisol - ^blood sugar; boost energy; gain weightEpinephrine – adrenaline; fight or flight; memory

Quiz1. If you burn your finger, your immediate reaction will probably involve

all BUT which of the following?

a) The brain c) Afferent neurons

b) Spinal cord d) Efferent neurons

2. If you are typing in the computer keyboard, the sensation of your fingers touching the keys is most likely communicated by ____ .

a) The autonomic neurons

b) Motor pathway neurons

c) Sensory pathway neurons

d) Autonomic neurons

3. The neurons of the motor pathway control _______ .

a) Stress reactions c) Involuntary muscles

b) Organs and glands d) Voluntary muscles

Quiz4) What type of cell can become other types of cells in the body?

a) Blood cells c) Neurons

b) Stem cells d) Basal cells

5) Which of the following is NOT a function of the sympathetic division?

a) Increasing digestive activity to supply fuel for the body

b) Dilating the pupils of the eyes

c) Increasing the heart rate

d) Increasing the activity of the lungs

6) Which of the following would be active if you are sleeping?a) Sympathetic division c) Somatic Division

b) Parasympathetic division d) motor division

7) Andrew never really grew to be very tall. The doctor told his parents that Andrew’s ______ gland did not secrete enough growth hormone.

a) Pituitary c) Thyroid

b) Adrenal d) Pancreas

The Structures of the BrainLocation of function – brain areas for particular functions

• Brain stem – top of spinal cord ; pons & medulla

• Pons – sleeping; waking & dreaming; left-right body coordination; arousal

• Medulla – some automatic functions; breathing, swallowing & heart rate

functions that are not consciously willed

• Cerebellum – control & coordinate involuntary,rapid, fine motor movement

Reticular activating system:

Reticular formation

–General attention, alertness and arousal

Structures Under the Cortex• Limbic System –

structures involved in learning, emotion, memory & motivation

• Thalamus – relays sensory message to the cortex; processes some sensory info

Traffic officer of the brain – directs to higher areaolfactory bulb (smell)

Structures Under the Cortex

• Hypothalamus – Hypothalamus – motivational behavior; sleep, hunger; thirst & sex

Structures Under the Cortex• Amygdala – arousal and regulation of emotions

initial emotional response to sensory info ( danger or threat)fear and memory of fear

• Hippocampus – “sea horse” in Latinformation of long term memorystorage of memory for locations objects

The Cortex• The Cerebrum – higher forms of thinking

largest grain structureupper part of brain; 2 hemispheresmost sensory; motor and cognitive processes

Cerebral hemispheres – 2 halves of cerebrum (right & left)Corpus callosum – thick bundle of neurons connecting 2 cerebral hemispheresLateralization – specialization of 2 hemispheres for particular operations

Cortex – collection of several thin layers of cells covering cerebrumhigher mental functions & interpret sensory input

1/8” thick – ¾ of all cells in human braindeep crevices and wrinkles (more neurons) rat-smooth

Grey matter – grey tissue of brain(White matter – long myelin coved axons)

Lobes of the Cortex• Occipital – visual centers

blindness / recognition

• Parietal – somatosensory cortextouch, taste & temp

• Temporal – auditory cortexhearing & meaningful speech

Wernicke’s aphasia – use of meaning-less words

• Frontal – higher mental functioningmake plans; think creatively;fluent speech

Motor cortexMirror neurons Left lobe - Broca’s area – speechBroca’s aphasia – inability to under-

stand written or spoken language

Neuron and Brain Lobes

Prefrontal Cortex & Personality

• Phineas Gage

Prefrontal Cortex - personality• Rats and mice only 3.5%

• Humans – 29%• Phineas Gage – railroad worker

inch thick – 31/2 foot rod through headmiracle lived; think; speak; rememberDr. Jekyll / Mr. Hyde change“not Phineas”mild mannered to mean & angryresponsible to not work; hold jobs

Right and Left Brain

Right Brain

• Controls left hand

• Non verbal

• Spatial visual ability

• Facial recognition

• Emotional thought

• Emotional recognition

• Process the whole

• Pattern recognition

• Musical / artistic

• Intuitive

Left Brain

• Controls right hand

• Spoken language

• Written language

• Reading

• Logic

• Symbolic

• Sequential task

• Rational / analytic

• Analysis of detail

• Math

Split Brain

Split Brain: is left dominant?• Shown composite of photo (a) asked to pick

out the face seen from series of photos (b);

• Stated; seen face on right side of composite;

• Yet, pointed with their left hands to the face that had been on the left

• 2 hemisphere not communicate

• Verbal left side – only saw right half

• Mute right side – aware of left half

Quick Quiz

1) Keeping in mind what both sides of the brain are involved in most activities, which of the following is / are more closely associated with the left hemisphere?

a) Enjoying a musical recording

b) Wiggling the left big toe

c) Giving a speech in class

d) Balancing a checkbook

e) Recognizing a long lost friend

His and Her Brains?

His and Her Brains• Gender differences (intuition, abilities) are stereotypes

– More alike than different.

• Sex differences; result rather than cause of behavioral differences– Nature or nurture

• Brain difference not explain behavior or performance– Difference in brain activity but not ability to complete– Listen to John Grisham; women left and right temporal; men only left.

Quiz1. In which lobe of the cortex do you find the primary auditory area?

a) Frontal c) Occipital

b) Temporal d) Parietal

2. The higher mental function, such problem solving are found in ____ .

a) Frontal c) Temporal

b) Parietal d) Corpus

3. A man wakes up and finds that people around him are using words that make no sense, and they don’t understand him. This is like _____

a) Wernicke’s aphasia c) apraxia

b) Broca’s aphasia d) spatial neglect

4. If you were a split brain patient, which would be TRUE?a) Objects in your left visual field would be easily named

b) Objects in you left visual field are invisible

c) Objects in your right visual field would be easily named

d) Objects in you right visual fields are invisible

Review

Neurotransmission / Synapse1- Neuron at rest (- inside + outside)

2 - Neural impulses move down axon; gate opens; +Na enters cell voltage changes from (-) to (+)

3- When impulse reach button tip;must get across synaptic cleft (gap);synaptic vesicle release neurotransmitter

4- When reaches the other side;briefly bond w/ receptor sites(lock & key)

5- Receiving membrane will change;excite – increase firing (+ voltage)inhibit –decrease firing (- voltage)

6- Neuron returns to resting state (- voltage)

Action potential - a sequence of gates opening down the length of the cell (as 2nd gate opens 1st closes)

-multiple +/- messages sent; take average

Neuron

The Brain